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05704-sw-03

FINAL REPORT

Mapping and Monitoring Submerged AquaticVegetation in Ichetucknee

and Manatee Springs

Submitted to:

Suwannee River Water Management District9225 County Road 49

Route 3, Box 64Live Oak, FL 32060

Submitted by:

University of FloridaDepartment of Fisheries and Aquatic Sciences

7922 NW 71st StreetGainesville, FL 32653

(352) 392-9617

2803 Fruitville Road, Suite 130Sarasota, FL 34237

(941) 954-4036

June 2003

05704 (AV) cover 6/10/03 8:00 AM

Mapping and Monitoring Submerged Aquatic Vegetation in Ichetucknee and Manatee Springs

Final Report

June 2003

Prepared for:

Suwannee River Water Management District 9225 County Road 49

Rout 3, Box 64 Live Oak, FL 32060

Prepared by:

R. C. Kurz, P. Sinphay, W. E. Hershfeld, A. B. Krebs, A. T. Peery

2803 Fruitville Road

Suite 130 Sarasota, FL 34237

(941) 954-4036

And

Debra C. Woithe, M.S. 5115 Palmetto Point Drive

Palmetto, FL

And

S.K. Notestein, T. K. Frazer, J. A. Hale, and S.R. Keller Department of Fisheries and Aquatic Sciences

University of Florida 7922 NW 71st Street

Gainesville, Florida 32653 (352) 392-9617

FOREWORD

This report was prepared for the Suwannee River Water Management District (SRWMD) by Post, Buckley, Schuh & Jernigan (PBS&J) under Contract No. 02/03-180.

ACKNOWLEDGEMENTS

Mr. Rob Mattson of the SRWMD was instrumental in coordinating the administrative aspects of the project with the various Park staff and provided direction and technical guidance throughout the project. Mr. Sam Cole, Park Biologist for the Ichetucknee Springs State Park, provided invaluable assistance in coordinating field mapping and sampling within the Ichetucknee Springs and River. He also provided much of the data used in the recreational impact analysis. The Center for Taxonomy and Systematics (Mr. Michael Milligan) conducted all of the SAV-associated macroinvertebrate identification.

Mapping and Monitoring SAV in Ichetucknee and Manatee Springs ii

EXECUTIVE SUMMARY This report describes the mapping and monitoring of submerged aquatic vegetation (SAV) and associated biota and water quality for the Ichetucknee Springs and Manatee Springs systems, located in north-central and west Florida, respectively. The specific tasks for this project were: 1. To map the spatial distribution of SAV in the Ichetucknee Springs and River and Manatee

Spring and its spring run; 2. To conduct monitoring and sampling of SAV in the Ichetucknee and Manatee Spring systems

to document existing vegetation health and identify the relationships between water flow, velocity, canopy cover, and SAV plant community structure;

3. To conduct SAV-associated macroinvertebrate sampling in the Ichetucknee River to better

understand the importance of SAV as a substrate/habitat for other organisms; and 4. To conduct a recreational use impact analysis for the river using SAV data collected by

Ichetucknee Park staff and available hydrologic data. Relationships between water levels and changes in SAV coverage were analyzed after periods of heavy recreational use to determine if damage is greater during drought years.

The most common species encountered (in order of percent cover) in the Ichetucknee Springs and River were Sagittaria kurziana, Zizania aquatica, Vallisneria americana, Chara sp., Myriophyllum heterophyllum, Ludwigia repens, and Hydrocotyle sp. Only sparse patches of Sagittaria kurziana were found in Manatee Springs, mainly at the periphery of the headsprings. Approximately 78% of the Ichetucknee River bottom is covered by SAV compared to approximately 1% coverage in the shorter Manatee Springs run. In comparison to a previous mapping effort by Dutoit in 1979, SAV coverage in the Ichetucknee River has increased by approximately 23 acres or 353% over the past 24 years. Field monitoring was conducted to measure SAV coverage, biomass, water quality, stream velocity, canopy coverage, and periphyton abundance along 31 evenly distributed transects in the Ichetucknee River. The results of field monitoring show that SAV biomass in the river is higher than several spring-fed rivers in north-central and west Florida. The Ichetucknee River has optimal sediment and flow characteristics suitable for SAV growth. Changes in SAV biomass along the river appears to be largely a function of location, depth, and canopy cover, with greater percent cover and biomass in the lower Floodplain reach where light limitations (greater tree canopy cover over the river) may be causing a response in the growth of longer blades. Periphyton abundance was greatest in areas of low canopy cover (Rice Marsh reach). The spatial distribution, abundance, and diversity of SAV and associated epibenthic macroinvertebrate communities, are often utilized to assess the heath of aquatic ecosystems. SAV-associated macroinvertebrates were sampled in the Ichetucknee River along the same 31 transects where SAV field monitoring was performed. A total of 31,539 individuals representing 47 species of macroinvertebrates were identified during this sampling effort. Chironomids dominated the samples and represented approximately 91.8% of all samples combined, followed by Hydracarina sp. (4.3%), Petrophilla sp. (1.2%), Hydroptila sp. (0.7%), and Oxyethira sp.

Mapping and Monitoring SAV in Ichetucknee and Manatee Springs iii

(0.5%). Based on the diversity and abundance of SAV-associated macroinvertebrates, the Ichetucknee River would be considered “healthy” compared to other streams and rivers in Florida. Macroinvertebrate abundance and number of taxa were negatively correlated with canopy cover - the greatest canopy cover occurred in the Headspring and Floodplain reaches compared to the Rice Marsh which had little to no canopy cover over the main river channel. This relationship may be related to the abundance of periphyton, which was also greatest in areas of low canopy cover. Both macroinvertebrate abundance and number of taxa were positively correlated with periphyton abundance. There were no significant differences in the number of macroinvertebrate taxa or abundance with respect to stream flow velocity, water depth, SAV species, or SAV wet weight. Recreational activity has probably been the most important factor affecting the health of the Ichetucknee River and associated SAV beds from the 1970s to present. Monitoring by Park staff has indicated a relatively consistent trend of declining SAV coverage during the high use summer period, followed by an increase in coverage through the spring. The rate of decline in SAV coverage was determined to be significantly correlated with headspring water levels at one of four monitoring stations, and weakly correlated with groundwater levels and park usage (number of people). The following recommendations are presented based on the results of this study:

1) Continued monitoring of SAV and associated fauna and water quality should be conducted periodically (annually or biennially) to assess and compare future conditions with those found in this and previous studies. This information will be extremely useful in the future management of surface and groundwater resources in the area and the development of Minimum Flows and Levels (MFLs).

2) Enforcement of more restrictive park management guidelines for the Ichetucknee Springs

and River may be necessary during drought conditions since it appears that greater SAV loss occurs during periods of lowered water levels in the headspring. Water levels at the headspring should be used as the primary management tool, since these values often lag behind local rainfall conditions/patterns.

3) SAV in Manatee Springs and spring run appear to be affected by both long term and

seasonal changes in water quality (highly tannic waters from the Suwannee River) and grazing by manatees. Restoration of SAV in this spring system will be problematic, especially since most of the headspring area is open to swimming and recreational use. However, protection (e.g., through the use of exclusion zones) of existing, albeit sparse SAV may result in future increases and persistence of this important habitat.

Mapping and Monitoring SAV in Ichetucknee and Manatee Springs i

Table of Contents page

FOREWORD ....................................................................................................................... i ACKNOWLEDGEMENTS................................................................................................. i EXECUTIVE SUMMARY ................................................................................................ ii 1.0 Introduction................................................................................................................... 1 2.0 SAV Mapping ................................................................................................................ 2

2.1 Materials and Methods ............................................................................................. 2 2.1.1 Study Area ..................................................................................................... 2 2.1.1.1 Ichetucknee Springs and River.................................................................... 2 2.1.1.2 Manatee Springs ......................................................................................... 4 2.1.2 Mapping Methodology................................................................................... 5 2.1.2.1 GPS and GIS Specifications........................................................................ 5 2.1.2.2 Field Mapping............................................................................................. 6 2.1.2.3 Preparation of Digital and Hard Copy Maps............................................. 9 2.1.2.4 Quality Control Process ............................................................................. 9

2.2 Results and Discussion ........................................................................................... 10 2.2.1 SAV Maps.................................................................................................... 10 2.2.2 SAV Coverage ............................................................................................. 11 2.2.2.1 Ichetucknee Springs and River.................................................................. 11 2.2.2.2 Manatee Springs ....................................................................................... 12

3.0 SAV Sampling ............................................................................................................ 15 3.1 Introduction............................................................................................................. 15 3.2 Materials and Methods ........................................................................................... 15 3.2.1 Data Summaries and Statistical Analyses............................................................ 17 3.3 Results and Discussion ........................................................................................... 17

4.0 Macroinvertebrate Sampling....................................................................................... 33 4.1 Introduction............................................................................................................. 33 4.2 Materials and Methods ........................................................................................... 33 4.3 Results and Discussion ........................................................................................... 34

5.0 Recreational Use Impact Assessment ......................................................................... 40 5.1 Introduction............................................................................................................. 40 5.2 Methods................................................................................................................... 40 5.3 Results and Discussion ........................................................................................... 41

6.0 References ................................................................................................................... 49 Appendices Appendix A - Metadata for Ichetucknee and Manatee Springs SAV Maps Appendix B - Ichetucknee Springs and River and Manatee Springs and Springs Run SAV Maps Appendix C - Reprints of Dutoit (1979) Ichetucknee River SAV Maps and Cover Estimates Appendix D - Data and Statistical Summaries from SAV Transect Sampling Appendix E - Field Notes from SAV-Associated Macroinvertebrate Sampling Appendix F - SAV-Associated Macroinvertebrate Data for 31 Ichetucknee River Transects

Mapping and Monitoring SAV in Ichetucknee and Manatee Springs 1

1.0 Introduction The spring systems of Florida are a treasured natural resource. They provide a significant source of freshwater, create unique environmental conditions for rare aquatic habitats and biota, and are important recreational attractions for visitors from around the world. However, the springs, their recharge basins, and their downstream spring runs are fragile ecosystems and have been impacted by human development during the past century, particularly through excess nutrient loading and groundwater withdrawals. Recognizing the importance of these unique systems, the Florida Springs Task Force was formed by various state and local agencies and private interest groups in 1999 to develop management strategies for preserving and protecting the state’s springs. The following study was managed by the Suwannee River Water Management District (SRWMD) and funded by the Florida Department of Environmental Protection’s (FDEP) Florida Springs Initiative to address the Task Force’s Information Strategy, which was developed to implement monitoring programs to detect and document long-term trends in spring conditions. This project involved the mapping and monitoring of submerged aquatic vegetation (SAV) in two spring systems, Ichetucknee Springs and Manatee Springs. SAV-associated macroinvertebrates were also collected in the Ichetucknee Springs system. This information will be useful to evaluate trends in ecological conditions in the springs and lead toward the better management of these aquatic ecosystems. The specific tasks for this project were: 5. To map the spatial distribution of SAV in the Ichetucknee Springs and River and Manatee

Spring and its spring run; 6. To conduct monitoring and sampling of SAV in the Ichetucknee and Manatee spring systems

to document existing vegetation health and identify the relationships between water flow, velocity, canopy cover, and SAV plant community structure;

7. To conduct SAV-associated macroinvertebrate sampling to better understand the importance

of SAV as a substrate/habitat for other organisms; and 8. To conduct a recreational use impact analysis for the river. Using SAV data collected by

Ichetucknee Park staff and available hydrologic data, relationships between water levels and changes in SAV coverage were analyzed after periods of heavy recreational use to determine if damage is greater during drought years.

This report is divided into four sections (mapping, monitoring, SAV-associated macroinvertebrates, and recreational use impact analysis) which address each of the above tasks.


2.0 SAV Mapping Submerged aquatic vegetation (SAV) was mapped in both the Ichetucknee Springs and River and Manatee Springs and its spring run. This information was gathered to document the existing spatial distribution and coverage of SAV in each spring system. Comparisons to previous SAV mapping in Ichetucknee Springs were made based on a study by Dutoit in 1979. 2.1 Materials and Methods

2.1.1 Study Area

2.1.1.1 Ichetucknee Springs and River The Ichetucknee Spring and River are located approximately three miles west of Fort White, Florida. The river crosses U.S. 27 and also defines a portion of the county boundary between Suwannee and Columbia County (Figure 2-1). The Ichetucknee River is fed by nine named springs located along the upper 2.5-miles of the river. The northernmost spring forms the head of the river and is known as Ichetucknee Spring or Head Spring (Figure 2-2). Flow from this spring travels southward and forms the Ichetucknee River proper. The remaining eight named springs of the group are, in downstream order, Cedar Head Spring, Blue Hole Spring, Roaring Springs, Singing Springs, Boiling Spring, Grassy Hole Springs, Mill Pond Spring, and Coffee Spring (Figure 2-3). Flow characteristics for the Ichetucknee Springs group are shown in Table 2-1. The springs are within the confines of the Ichetucknee Springs State Park, which occupies 2,241 acres in Columbia and Suwannee Counties and was established in 1970. Historically, the area was used by local residents for swimming, watering of livestock, and phosphate mining. The average river width is 6 to 10 m and average depth is approximately 1 m in the upper reaches of the river. At approximately 550 m downstream, the river meets the southward flow of Cedar Head Spring and Blue Hole Spring. The river then flows about 4800 m south, then 6400 m southwest and discharges into the Santa Fe River. Depth increases in the middle and lower reaches of the river to approximately 2 to 4 m. The Ichetucknee River lies within an ancient basin called the Ichetucknee Trace along the 50 ft contour line of USGS topographic maps (Dutoit, 1979). The contributing basin or spring-shed of the Ichetucknee Springs includes an area north toward Lake City and includes surface flows from several sinkholes including Rose Sink near the city of Columbia. Local recharge occurs in the vicinity of the headsprings through various sinkholes and percolation through limestone outcrops

Figure 2-1 (above). Aerial of Ichetucknee River. Figure 2-2 (below). Ichetucknee head spring.


and sandy soils. The SRWMD is currently evaluating the groundwater basin of the springs through a separate Springs Initiative grant from the FDEP.

Table 2-1. Spring characteristics for Ichetucknee and Manatee Springs.

Spring/Run

Mean Discharge (ft3/sec)*

Max. Discharge (ft3/sec)*

Min. Discharge (ft3/sec)*

Length of Spring Run Studied (ft.)

Ichetucknee** 360 578 241 17,388 Manatee*** 181 238 110 1,148

*from: Florida Geological Survey (1977) **period of record 1917-1974, n=375 measurements ***period of record 1932-1973, n=9 measurements

Figure 2-3. Map of Ichetucknee Springs System (from Florida Geological Survey, 1977).


Figure 2-4 (above). Aerial photograph of Manatee Springs. Figure 2-5 (below.) Manatee Springs State Park location map (source: FDEP).

The mapping area in the Ichetucknee system was located entirely within Ichetucknee State Park extending from the head spring downstream to the U.S. 27 Bridge. This represents a distance of approximately 5300 m. There are three distinct zones within the mapping area representing different canopy coverages, river widths, and depths. The upper zone from the head spring to approximately 1050 m downstream is characterized by heavy tree canopy, relatively narrow channel width (10 to 15 m) and shallow depths (1 to 2 m) and was originally identified as the Headsprings Reach in a previous study by Dutoit (1979). The middle zone or Rice Marsh area is much wider (approximately 60 m wide) and is characterized by thick Zizania aquatica marshes along the shoreline, moderate depths (2 to 3 m) and open canopy. The river channel is approximately 15 to 20 m wide and a few small tree islands occur in this middle zone. Like the upper zone, the lower zone or Floodplain Reach (Dutoit, 1979) is characterized by heavy tree canopy, however, the average width is approximately 15 to 20 m and depth is approximately 2 to 3 m. This zone lies within a flatter topography than the upper zone and is flanked by extensive floodplain forest (primarily bald cypress, Taxodium distichum).

2.1.1.2 Manatee Springs Manatee Springs is located in Levy County, west of Chiefland, along the lower reaches of the Suwannee River. Unlike the Ichetucknee Spring systems, Manatee Springs has a much shorter spring run of only 350 m before entering the Suwannee River (Figures 2-4, 2-5). The area surrounding the spring is also a state park and is used for recreation including camping, swimming and SCUBA diving. A sinkhole (Catfish Hotel) exists approximately 25 m from the Manatee head spring and the two are connected via a cave network. The mapping area in the Manatee Spring system extends from the headspring for approximately 350 m (1,148 ft) downstream to the confluence with the Suwannee River.


2.1.2 Mapping Methodology A combination of mapping methods was used for the Ichetucknee and Manatee Springs. Field mapping methods were selected after an initial field reconnaissance and refined through several trial mapping efforts. Where Global Positioning System (GPS) signals were reliable and met or exceeded minimum standards, integrated GPS/GIS on a handheld computer was used for field mapping. These areas of GPS mapping cover all of Manatee Springs and roughly half of Ichetucknee Springs. In the narrow, heavily canopied areas of the Ichetucknee River where GPS signals were obstructed, transect mapping was performed. SAV was classified according to the percent coverage of each species present. Following completion of field mapping, a seamless coverage of SAV bed polygons was created for the Ichetucknee Springs and River. For Manatee Springs, a shoreline boundary and point coverage were created as separate layers. All coverages were prepared using ESRI’s ArcView GIS software. All field mapping was performed during March, April, and early May 2003. Details describing the GIS software, GPS equipment, field mapping methods, final map preparation, and the quality control process for both spring systems follow.

2.1.2.1 GPS and GIS Specifications The primary field mapping computer hardware was a Compaq iPAQ, model number 3850, running Windows PocketPC. ESRI ArcPad Version 6.01.5 GIS software was used along with a Teletype World NavigatorTM GPS, CF v2.0, Card #1651. The ArcPad mapping software automatically retrieved positions from the GPS as the outline of the SAV bed (polygon) was traced and produced mapped features in the field. The ArcPad graphical user interface was customized with ArcPad Studio using VBScript and XML programing languages. The custom interface provided data entry forms specifically designed for this mapping effort. A standard Dell laptop computer running Windows 2000 and ArcView 3.2 was used to reference information as needed. The laptop was operated using a 9 volt battery and power inverter. The final map was prepared in ESRI ArcView 3.2. The Florida State Plane, North Zone, Datum HPGN (NAD 83/90) with units in Feet projection was used. The minimum mapping unit was 30 square feet. Metadata documentation is provided in Appendix A. Based on the FDEP Mapping Standards for GPS, the following minimum settings were used for all mapping: • PDOP <6.0 • Signal to Noise Ratio >6.0 • Elevation Mask = 15 deg. • Minimum positions = 25 • Minimum number of satellites = 4 • Logging interval of point features = 1 second • Coordinate system = latitude/longitude A deviation of no more than 5 meters was deemed acceptable. For the Ichetucknee River, a Florida Department of Transportation (FDOT) benchmark at the U.S. 27 bridge was used to verify the accuracy of the GPS units used for mapping. Plots of verification points are shown in Figure 2-6 for each of the dates mapping was performed. Quality control and quality assurance were conducted by periodic point feature collection at several locations, including the U.S. 27


bridge, the concrete/rock wall at the head springs, and the Ichetucknee headsprings staff gage. GPS accuracy checks met the 5 meter deviation standard in open canopy areas where PDOP values typically ranged between 1.0 and 3.0 (< 6.0). Measured horizontal accuracy was typically within 1 to 2 m of the FDOT benchmark position. The images used as a base map were one meter resolution, 1:24,000 scale, 1999 USGS color infrared Digital Orthophoto Quarter Quads (DOQQ). Quad number Q4823 Northeast was used for Ichetucknee Springs and Q4424 Northwest was used for Manatee Springs. During preliminary shoreline mapping using GPS, it was determined that the aerial photography for the Ichetucknee River was shifted approximately 25 feet to the north. The known benchmark at the U.S. 27 bridge also confirmed the need to shift the DOQQ. Using the GPS mapped boundary of the headsprings and the benchmark location on the U.S. 27 bridge, the image was shifted to the north along with the digitized shoreline boundary described below. The imagery for Manatee Springs did not appear to be shifted and was used in native format for shoreline and SAV mapping. A staff gage at the springs was used as a reference point.

2.1.2.2 Field Mapping A shoreline feature was created for each spring run to delineate the boundary of the mapping areas. The shoreline boundary was demarcated at the interior edge of dry land, dense wetland hardwood forest, and/or emergent wetland vegetation. Where conditions allowed for GPS mapping, the shoreline was followed with the GPS, in a canoe or on foot, sometimes using an extended pole for a receiver mount. Where GPS signals were obstructed by dense tree canopy, the shoreline was photo-interpreted from aerial photography. The photo-interpreted shoreline was field checked and edited to create a more accurate delineation. Where feasible, ground truthing was done using a GPS reference and edited in the field. In other cases, the width of the river was measured with a tape and the shoreline edited later during map preparation. SAV was evaluated according to the percent coverage of all species present. The classification system, a modified Braun Blanquet cover estimate, follows the methods of Woithe and Sleszynski, (1996), for the nearby Rainbow River in Dunnellon, Florida. Cover categories used were 0%, 0-25%, 25-50%, and 50-100%. To simplify the recording of information in the field, the cover categories were represented by a 0, 1, 2 or 3, respectively. A systematic reconnaissance of an area was first performed to assess the species present, their cover categories, and how they should be delineated. Additional data collected for each spring run were bottom feature type (SAV, bare, or emergent), date, and comments. Some of the information in the comments field includes substrate type (rock or sand), algae coverage, and species present in quantities less than the minimum mapping unit. Vegetation patches as small as 30 square feet were individually mapped for the Ichetucknee River.

Figure 2-6. GPS verification/QC check points at the U.S. 27 bridge on the Ichetucknee River. Note pixel size of DOQQ basemap is 1 m.


Portions of the Ichetucknee River where the GPS was used for SAV mapping are: 1) from the head spring to the end of the broad, open rice marsh, and 2) approximately 2000 ft of river upstream from the downstream take out point near U.S. 27. In these areas, SAV was mapped by following the perimeter of the bed with the GPS unit. This was done while observing the SAV from the canoe, or with a diver in the water guiding the canoe. The GPS receiver was either mounted to a telescoping pole, or on the bow of the canoe. SAV polygons were checked for positional and dimensional accuracy using the aerial photography, visible landmarks, and previously mapped features. A point feature was placed within each SAV polygon, and attributed using the customized forms. Transect mapping was performed as an alternative to GPS mapping in three general sections of the Ichetucknee River: 1) the confluence of the Mill Pond Spring to Dampier’s Landing Dock, 2) Dampier’s Landing to the power lines, and 3) the U.S. 27 bridge to the take out point. A 100-foot floating transect was devised using polyethylene rope, floats and weights. Weights were used to anchor the beginning and end points of the transect, which had large floats. Smaller floats were used to mark 25 foot segments. The beginning transect point of each of the three sections was a fixed point with a location determined using GPS. The transect line was shifted down or up river by moving one of the weights. GPS points were taken at the beginning and endpoints of each transect to assist in locating transects within the river during the GIS desktop mapping. SAV polygons were hand drawn relative to the transect onto waterproof paper from the canoe, or while snorkeling. Notes and sketches were made regarding the location of the transect relative to bends in the river. SAV polygons were drawn onto field sheets with lines representing the relative distance between transect line and river boundary. During the rise in water levels in late March 2003, water lettuce (Pistia stratiotes) formed a dense mat across the entire river at several oxbow locations in the lower portions of the river (Figure 2-7). Little to no light could penetrate this mass of plant material for several weeks. Volunteer crews organized by the Center for Aquatic Studies at the University of Florida’s Institute of Food and Agricultural Sciences were led by the Park staff to clear much of this vegetation during late March and early April 2003. Flow and river stage in the Ichetucknee River and in Manatee Springs (the lower Suwannee River) changed significantly during the field mapping period. Santa

Figure 2-7. Water lettuce mat at oxbows in lower Ichetucknee River in March 2003 (above) and effect of vegetation on water column light penetration (below).


Fe River levels rose approximately 2 to 3 m from late February through late March and this rise was most pronounced in the downstream section of the Ichetucknee River. Ichetucknee River stage is directly affected by rises in the Santa Fe River and a plot of river stage in the Santa Fe and in Manatee Springs is shown in Figure 2-8.

Figure 2-7. Changes in river stage immediately downstream of the Ichetucknee River at the Santa Fe River USGS gaging station and at Manatee Springs near the Suwannee River (source: USGS, 2003). In the Ichetucknee River, several larger Zizania aquatica beds that were emergent during initial field reconnaissance trips in February 2003 became submersed during the field mapping and then became emergent again as the river level declined. Since the rise in stage was known prior mapping, these Zizania beds were delineated as shoreline/emergent areas versus SAV beds. In addition to changes in river stage, shoreline vegetation was pruned during the mapping period.


Private interest groups removed downed trees from the main channel to clear obstructions for tubers, sometimes exposing areas of bare substrate. In the Manatee Spring run, water clarity declined significantly with the rise in river stage – this was due to the more tannic and tidally-influenced Suwannee River backflowing into the spring run in March 2003 (Figure 2-8). The lower portion of the spring run is flanked by cypress floodplain forest which also drained tannic waters into the spring run, even during the May 2003 mapping period where river levels had declined. As a result, light and water quality conditions in this area are extremely variable. The endangered west-Indian manatee (Trichecus manatus) also uses the spring run as a source of freshwater and forages on SAV during the early spring. Due to the poor conditions for SAV growth and intense predation by manatees, SAV in the Manatee Springs run is very sparse. As a result, a point coverage of SAV beds was created instead of polygons to identify the location of SAV. Braun Blanquet coverage was recorded at each point along with approximate dimensions of each bed, which were typically less than the 30 square feet minimum mapping unit.

2.1.2.3 Preparation of Digital and Hard Copy Maps After each field mapping session, the information was transferred and compiled into the comprehensive, geographically referenced GIS database using ArcView 3.2. The GPS field delineation was essentially redigitized "heads up" (traced) in the comprehensive layer to create clean, complete polygons with their associated attributes. For the transect mapping, the locations of the 100 foot transects lines were first digitized onto the basemap, using the GPS points as supplemental information. The SAV polygons and their attributes were then digitized "heads up" relative to transect lines from the field notes, just as they had been in the field. The straight, fixed width transects of the field sheets were fit into the sinuous, changing width of the river with the aid of notes and sketches drawn onto the field sheets.

2.1.2.4 Quality Control Process SAV mapping data was checked using a rigorous quality control process. Quality control of the GIS map was performed to verify that all polygons were correctly labeled and that no polygons were smaller than the minimum mapping unit. The field data were thoroughly reviewed to assure that information was correctly transferred from the GIS file. The GIS files were checked to assure that all polygons were labeled, that adjacent polygons did not have the same attributes, and that attributes in all fields were feasible (for example, that a polygon with Sagittaria kurziana coverage of 50-100% did not have a bottom feature type of "bare"). The completed GIS map was downloaded onto the handheld computer with GPS for field verification. This allowed for tracking and viewing one's location on the map while navigating

Figure 2-8. Manatee Springs run in Feb (above) and May (below) 2003. Note change in water clarity (increase in tannic color).


the river. The map was verified at 70 locations (Figure 2-9) and the overall accuracy was determined to be 94.2%. This field checking was done both by selecting random individual points in the river and by navigating upriver and observing approaching polygons. As the canoe approached a polygon, its characteristics (size and shape, species present, and cover category) were identified from the map, and verified by visual observation. Though the GPS signals were sometimes inadequate to delineate small polygons, they were sufficient to determine relative location of most polygons in the river. Additional quality control was performed by comparing field sampling information from the State Park biologist (Sam Cole) taken at 10 transects and also SAV monitoring data taken by UF in the spring of 2003 at 31 transects.

2.2 Results and Discussion

2.2.1 SAV Maps As described earlier, SAV mapping in the Ichetucknee River was conducted using both GPS and transect field techniques followed by heads up digitization and editing. The most common species encountered (in order of percent cover) in the Ichetucknee Springs and River were Sagittaria kurziana, Zizania aquatica, Vallisneria americana, Chara sp., Myriophyllum

Figure 2-9. SAV polygon quality control checkpoints on the Ichetucknee River.

(checkpoints = green box with check mark)


heterophyllum, Ludwigia repens, and Hydrocotyle sp. (photographs of the more common species are shown below). Chara is an algae which grows along the river bottom in large mats, typically in deeper areas south of the Headspring Run. Zizania was present mainly in the shallower areas of the Headspring Run and along the shoreline and in shallow areas within the Rice Marsh. Sagittaria was present throughout the river but became mixed with Vallisneria in the lower Rice Marsh and Floodplain Reach areas. Myriophyllum was mapped on only nine occasions, all within the Floodplain Reach area. Ludwigia and Hydrocotyle were present as small coverages along much of the river shoreline, but these areas were typically too small to map (less than 30 ft2 minimum mapping unit). Maps of SAV and unvegetated bottom for the Ichetucknee Springs and River are presented in Appendix B. The shoreline and SAV point coverage for Manatee Springs are also presented in Appendix B.

2.2.2 SAV Coverage 2.2.2.1 Ichetucknee Springs and River The total area of submerged habitat surveyed and classified during this study was approximately 150,658.22 m2 or 37.23 acres. A breakdown of area by bottom type is presented in Table 2-1 below. The coverage for emergent bottom type represents only a small percentage of the actual emergent marsh vegetation within the river floodplain since emergent vegetation was only mapped in a few isolated areas immediately adjacent to SAV beds. This was most prevalent within the middle “Rice Marsh” area where SAV and emergents were intermixed within the river boundary. By far, the dominant habitat features in the river are SAV beds. A total of 305 separate SAV beds (polygons) were mapped with a total coverage of 118,035 m2 or 29.2 acres (see Table 2-1). Table 2-2 represents the coverage of each species within the river, which results in a greater total number of acres than reported in Table 2-1. In some cases, an individual polygon may have more than one species present at a lesser percent cover than the dominant species. These calculations were performed by summing the area for each SAV bed (polygon) by each species present in a given bed. Sagittaria kurziana was the most prevalent species within the river representing over 50% of the total SAV cover. The


second most dominant species was Zizania aquatica at approximately 19%, followed by Vallisneria americana at approximately 18%. The algae Chara sp. represented about 10% of the total cover, followed by sparse patches of Myriophyllum heterophyllum, Ludwigia repens, and Hydrocotlye sp. which each represented less than 1% of the total cover.

Table 2-1. Coverage of bottom types at Ichetucknee Springs and River.

Bottom Type Sq. Meters Acres %Bare 4970.70 1.23 3.30%Emergent 27652.07 6.83 18.35%SAV 118035.45 29.17 78.35%Total 150658.22 37.23 100.00%

Table 2-2. Coverage of SAV by species in the Ichetucknee Springs and River.

SAV Species Sq. Meters Acres % of TotalMean Braun

Blanquet CoverSagittaria kurziana 76317.06 18.86 52.44% 3Zizania aquatica 27199.58 6.72 18.69% 2Vallisneria americana 25801.89 6.38 17.73% 3Chara sp. 14821.98 3.66 10.18% 3Myriophyllum heterophyllum 876.69 0.22 0.60% 2Ludwigia repens 499.08 0.12 0.34% 2Hydrocotyle sp. 28.78 0.01 0.02% 1

Braun Blanquet Cover Categories 0 = 0%, 1= 0-25%, 2= 25-50%, and 3= 50-100% cover within 1 m2 quadrat.

2.2.2.2 Manatee Springs The total area of submerged habitat surveyed and classified at Manatee Springs was approximately 9,040.53 m2 or 2.23 acres. A breakdown of area by bottom type is presented in Table 2-3 below. The majority of the head spring and spring run are currently bare. Of the SAV beds present, the dominant species in Manatee Springs and spring run was Sagittaria kurziana. This species typically occurred as small (<10 m2) patches, typically along the shallower (<2 m) fringes of the headspring and also in small (<1 m2) clumps in the main spring run. Blade lengths were typically less than 15 cm. The furthest downstream SAV observation was 215 m from the headspring. Using coverage estimates gathered during the point coverage mapping, estimates of SAV cover were calculated and are presented in Table 2-4 below.

Table 2-3. Coverage of bottom types at Manatee Springs and Spring Run.

Bottom Type Sq. Meters Acres %SAV 124.24 0.03 1%Bare 8916.28 2.20 99%Total 9040.53 2.23 100%


Table 2-4. Coverage of SAV by species in Manatee Springs and Spring Run.

SAV Species Sq. Meters Acres % of TotalMean Braun

Blanquet CoverSagittaria kurziana 116.492 0.0288 93.76% 1Ludwigia repens 2.385 0.0006 1.92% 1Potamogeton sp. 5.366 0.0013 4.32% 2Total 124.24 0.03 100%

Braun Blanquet Cover Categories 0 = 0%, 1= 0-25%, 2= 25-50%, and 3= 50-100% cover within 1 m2 quadrat.

In 1979, Dutoit mapped SAV in the Ichetucknee Springs and River (see Appendix C for copies of these maps). SAV coverages at that time totalled 26,036 m2 or 6.43 ac. The boundaries of Dutoit’s mapping effort appear to be smaller than the boundaries used in this study and did not include several short spring runs at Boiling, Grassy Hole, or Mill Pond Springs. Park use in 1979 had reached over 250,000 visitors per year and stricter regulations to limit environmental abuse had only recently been implemented. A 3,000 user per day limit had just been established by the Park to reduce further degradation of the river ecosystem. As a result, SAV was just beginning to recover after years of unrestricted recreational use during the time of Dutoit’s study. SAV coverage in the spring of 2003 was much higher than in 1979 at approximately 29 ac and 98% SAV cover of the river bottom versus only 33% coverage in the late 1970s. This increase in SAV is due to a number of factors, most notably the implementation of the above-mentioned park regulations and carrying capacity limits for recreational use on the river. Between 1979 and 2003, SAV coverage is estimated to have increased by approximately 74% in the Headspring Reach, 59% in the Rice Marsh, and 86% in the Floodplain Reach (Table 2-5).

Table 2-5. Estimated Changes in SAV Coverage at Ichetucknee Springs and River between 1979 and 2003.

Area Year Sq. Meters Acres % Change

Headspring Reach 1979 1872.00 0.462003 7230.49 1.79 286%

Rice Marsh 1979 12685.00 3.132003 30799.70 7.61 143%

Floodplain Reach 1979 11479.00 2.842003 80005.26 19.77 597%

Low coverage of SAV in Manatee Springs is likely due to the flood stage conditions which occurred immediately prior to mapping. These conditions resulted in the movement of highly colored water from the Suwannee River into the spring run. Park staff reported dark water conditions along the entire length of the run to the head spring. This phenomenon occurs periodically, resulting in low light conditions and poor conditions for SAV growth. Grazing by manatees also occurs during the spring, further reducing SAV coverage. For comparative purposes, the following discussion describes conditions in the nearby Rainbow Springs and River where SAV mapping was recently completed in 2000 (PBS&J, 2000).


Rainbow Springs, located in the southwest Marion County community of Dunnellon, is the fourth largest of the twenty-seven first magnitude spring runs in Florida. It shares many ecological features and species with the Ichetucknee Springs and River. Some notable differences include the Rainbow’s size (width and length), adjacent development, and relatively constant water levels. The Rainbow River is both a State Aquatic Preserve and an Outstanding Florida Water. Its average discharge at the headsprings is 700 ft3/second, and average river velocity is 0.5 miles/hour. Mean depth of the Rainbow River is approximately seven feet and maximum depth 15 feet, while roughly half of the river is between 3 and 5 feet deep (Childs, 1999). The river flows about 6 miles from its source at the head spring to its confluence with the Withlacoochee River, varying in width from about 100 to 300 feet. In general, the Rainbow is less heavily shaded than the narrower Ichetucknee and has a greater overall area between the fringing tree canopies. Spring discharge for the Rainbow River accounts for 97% to 99% of the volume of the river, and as a result water contributions from its watershed are insignificant (Water and Air Research, 1991). Spring discharge varies seasonally in response to rainfall, though regulation by the Inglis dam (located downstream on the Withlachochee River) keeps the Rainbow River stage levels held relatively constant (Jones, 1996). The constant water levels seem to have several effects on the vegetation of the river. Trees endure much less stress without widely fluctuating water levels and therefore tree falls appear to be much less frequent than in the Ichetucknee River. Non-woody emergent and submersed vegetation do not appear to be in transition because they experience constant water depths. Only very slight changes in the size and shape of emergent vegetation beds appear to occur over time. A few, more noticeable changes in emergent beds appear to be caused by recreational impacts. Like the Ichetucknee, the Rainbow is a very popular recreational resource, with concessions providing for tube and canoe rental, as well as swimming and boat launch. The river also used for fishing and SCUBA diving. Motorized boats are allowed on the river, though only idle speed is permitted. Several abandoned phosphate mines are present within the banks of the Rainbow River. The vast majority of the Rainbow River’s west bank is occupied by residential development. Activities associated with this development have a significant potential to impact SAV through both direct clearing of SAV as well as general access and use. Between the 1996 and 2000 vegetation mapping efforts, all changes in aerial coverage were less than 10%. At the time of the 2000 mapping, the most dominant SAV species of the Rainbow River were Sagittaria kurziana (strap-leaf sagittaria), Hydrilla verticillata (hydrilla), and Vallisneria americana (eelgrass), occurring in 52%, 37%, and 18% of the river respectively. With the exception of hydrilla, these percentages are nearly identical to the percentages of Sagittaria and Vallisneria in the Ichetucknee River. The invasive exotic hydrilla has roughly doubled its coverage since 1990 and is a substantial concern to resource managers. Ceratophyllum demerseum (coontial), Najas guadalupensis (southern naiad), and Chara sp., each occur in less than 5% of the river. Ludwigia repens (red ludwigia), Myriophyllum sp., Utricularia sp., and Nasturitium sp. cover less than 1% of the river each and are confined to the headspring area. Eleven percent of the river is bare substrate which is much less than in Manatee Springs, but higher than the approximately 3% bare area in the Ichetucknee River.


3.0 SAV Sampling 3.1 Introduction Sampling of SAV in the Ichetucknee Springs and River was conducted to document existing vegetation conditions and to identify relationships between stream velocity and SAV cover, biomass and community structure. Due to the paucity of SAV in Manatee Springs, no SAV sampling was performed. Water quality data for Manatee Springs is presented in Appendix D. The sampling protocol for SAV provided a statistically rigorous database that was used to assess multiple relationships between flow velocity, stage, water chemistry, physicochemical parameters (temperature, pH, conductivity, dissolved oxygen), and light availability (e.g., canopy cover) and SAV species presence and cover. The sampling protocol followed similar methods developed by Frazer et al. (2001) for the sampling of five coastal rivers along west-central Florida (four of which were spring-fed). 3.2 Materials and Methods For the Ichetucknee River system, 31 evenly distributed transects were selected for sampling and included a range of flows and terrestrial canopy coverage (Figure 3-1). Physical, chemical, and biological samples were collected on April 30th, 2003 between approximately 9 AM and 6 PM. These sites were distributed (approximately 150 m between transects) in three areas: the Headspring Reach; Rice Marsh area; and the Floodplain Reach. The transects were oriented perpendicular to stream flow and began near the head spring canoe launch and ended near the last take-out point near U.S. 27. Several of these transects were adjacent to permanent sampling locations utilized by the park. At each transect, five stations were sampled, with one in the middle of the river and two to either side, approximately one-third and two-thirds the distance to the shoreline. Mid-stream sampling locations were documented with a Garmin WAAS enabled GPS receiver. The sampled parameters included: stream width (Transects 1-8 only), water column depth, stream flow, canopy cover, temperature, specific conductance, dissolved oxygen, pH, water column light attenuation, submersed aquatic vegetation (SAV) biomass and coverage (selected transects), periphyton abundance, and substrate type. Stream widths were measured with a 50 m fiberglass tape measure. Water column depth was measured with a telescoping fiberglass survey rod. Stream velocities were measured at 60% of water column depth with a Marsh-McBirney Model 2000 portable flow meter reporting 5-second average values. Terrestrial canopy cover directly above each station was categorized visually as

Figure 3-1. SAV sampling locations (in green).


0 to 100%. Measures of temperature (deg. C), specific conductivity (µS/cm), dissolved oxygen concentration (mg/L), and pH were measured in situ with a Yellow Springs Instrument Company model 650 hand-held meter. Li-Cor Instruments Inc. quantum light sensors were employed to simultaneously collect surface and downwelling light intensity (umole photons/s/m2 of photosynthetically active radiation, PAR) with a data logger at selected locations. Light attenuation (Kd) was determined from the equation: Kd = [ln (Io / Iz)] / z, where Io is incident irradiance at the water surface and Iz is light intensity at depth z (m) (Kirk 1994). Divers visually determined the substrate type and assigned it to one of 10 categories: mud, mud/sand, mud/shell, mud/rock, sand, sand/shell, sand/rock, shell, shell/rock, or rock. Estimates of SAV coverage (%) were made at all sampling locations (n = 155). Measures of SAV biomass (kg/m2) were collected along 10 of the 31 regularly spaced transects, so that each of the three river zones was adequately represented. This resulted in 50 individual measures of biomass. Along each transect, five stations were sampled for submersed vegetation, with one in the middle and two to either side approximately one-third and two-thirds the distance to the shoreline. At each of the resulting stations, a 1-m2 quadrat was placed on the river bottom and the SAV contained within was visually estimated by its coverage. Although this was done for each SAV species, total coverage is approximately equal to the most abundant SAV species contained within the quadrat. At those transects where SAV biomass was harvested, a 0.25 m2 quadrat was placed on the bottom and the above-ground biomass contained within the quadrat removed by divers and transported to the surface. SAV was separated by species and the different fractions were spun in a nylon mesh bag to remove excess water. Samples were then weighed with calibrated hand-held Pesola scales. Weights were recorded to the nearest 10 g for samples less than 1 kg and to the nearest 100 g for samples greater than 1 kg. All types of vegetation present in the quadrat were recorded and ranked according to their biomass. Periphyton associated with submersed macrophytes were sampled along the ten transects where SAV biomass measures were made. Along these transects, a representative sample of the most abundant macrophyte species was carefully removed and placed in a 1-L Nalgene jar with deionized water and stored in a cooler with ice until processed (within 24 hours of collection). Periphyton abundance was quantified with a method used by Moss (1981) and modified by Canfield and Hoyer (1988a). Periphyton removal was accomplished by vigorously shaking each bottle for 30 seconds and the resultant slurry was poured though a 1.0 mm screen into a Nalgene beaker. Fresh deionized water was then added to the plant sample and the process repeated a total of three times. The total slurry volume (ca. 1 to 1.5 L) was thoroughly mixed and a sub-sample (ca. 50 to 400 ml) filtered through a Gelman type A/E 47 mm glass-fiber filter. Filters were stored frozen in wide-mouth Nalgene jars that contained desiccant until analyzed for chlorophyll. Periphyton abundance was expressed as mg chlorophyll/g of host macrophyte weight. Macrophyte weights were expressed either as wet or dry weights (wet wt and dry wt, respectively). Wet and dry weights for each macrophyte sample were determined by weighing the plants to the nearest 0.001 g on a Mettler Toledo AG204 scale. Wet (fresh) weights were measured after the macrophyte samples had been gently blotted with paper towels. Dry weights were measured after the macrophyte samples had been placed in a forced-air-drying oven maintained at 65 deg. C for approximately 48 hours.


3.2.1 Data Summaries and Statistical Analyses All raw data used in summary figures and tables are available in electronic format. Mean transect values, where appropriate, were used to summarize physical, chemical and vegetative measures. For correlation analyses and model development, all variables were log10-transformed to accommodate heterogeneity of variances (Sokal and Rohlf 1981). When aquatic vegetation biomass estimates were equal to 0.0 kg wet wt/m2, a negligible value of 0.001 kg wet wt/m2 was used for subsequent statistical analyses. All statistical computations were performed with the JMP statistical software package (SAS Institute, Inc. 2000). Statements of statistical significance imply p < 0.05. 3.3 Results and Discussion Raw data and statiscial summaries of the SAV transects are presented in Appendix D. Summary results of each parameter sampled are discussed below. Sampled depth values ranged from 0.3 to 3.0 m, with the sampled river average depth being 1.47 m. Mean mid-channel depth was 1.9 m and mean transect depth generally increased with distance downstream (Figure 3-2), however, variability in depth at each transect was generally lower downstream from transect 15. In the upper river, from the main spring boil to the confluence with Blue Spring run, shallowest average transect depths were encountered. In the Rice Marsh reach, where the river was widest, shallow depths were common as the river widens, but a deeper channel was also present. In the lower river section, stream width narrowed and a concomitant increase in stream depth was noted. Water depth can potentially influence the abundance and distribution of SAV through several processes. First, hydrostatic pressure can be directly inhibitory. In fact, Huchinson (1975) noted that angiosperms in freshwaters are not generally observed deeper than 8 to 11 m. Such depths, however, do not occur in our study area within the Ichetucknee River. Second, increased light attenuation and reduced light availability with depth can negatively affect SAV growth and may, in many instances, prohibit plant colonization. Light levels at all sampling locations in the Ichetucknee River were sufficient, however, for SAV to occur (see below). Third, SAV that occurs in shallow water can be subject to physical damage (tearing or uprooting) by recreational users that walk or drag their feet along the river bottom. The likelihood of recreational users touching the bottom is a function of the height of the water column (and users’ leg lengths). Shallow water in the upper sections of the Ichetucknee River are likely more susceptible to recreational damage, while the more consistently deep sections of the river further downstream may provide a depth refuge for SAV. It is worth noting that SAV in the upper most river (see historical data for station 4.1 from 1989 to 2002) increased as the daily limit of recreational users declined.


ICHETUCKNEE RIVER

0.0

0.5

1.0

1.5

2.0

2.5

0 5 10 15 20 25 30

TRANSECT

DEP

TH (m

)

Figure 3-2. Mean transect depth (m) for the Ichetucknee River on April 30th 2003.

Measured stream velocity rates ranged from –0.01 to 0.56 m/s, with the a mean of 0.20 m/s. The negative flow value was encountered in an eddy along a bend of the river at transect 24. Mean flow velocity gradually increased with distance downstream as a consequence of additional spring discharge (Figure 3-3). However, variation between transects was often large and may simply be reflective of the differences in stream widths and depths. Stream velocity strongly influences the composition of the substrate (Butcher, 1933) which can, in turn, influence the SAV community. Favorable sediments for macrophyte growth, such as sandy clays, may be scoured away at velocities greater than 0.30 m/s (Hynes, 1970) and sand substrates begin to give way to gravel and large rocks at stream velocities of 0.60 m/s or greater (Butcher, 1933). Thus, a stream bed consisting of large stones or bare rock that are continually being rolled or scoured will have little submersed aquatic vegetation, while a river bed that is comprised largely of mud, silt and sand has the potential to support abundant aquatic vegetation (Allan 1995). Additionally, large amounts of continuously shifting sand may bury established macrophyte communities while remaining too unstable to allow re-colonization. Therefore, detrimental aspects of flow are generally encountered at high stream velocities. Within the Ichetucknee River, the average observed flow rate was 0.20 m/s, with only 10% of the measured flow rates exceeding 0.33 m/s. These values appear to be well below those necessary to scour the substrate or dislodge rooted plants (see Butcher, 1933) and correspond closely with the velocity values for peak macrophyte diversity reported by Nilsson (1987). Streams with these velocities may be expected to have mud or sand substrates, which agree with our observations that the substrate in the Ichetucknee River is mostly composed of about 39% sand and 47% mud (see Figure 3-13 below). While we modeled significant relationships between SAV biomass and SAV coverage with stream velocity, only a small amount of the variation in these parameters (13% and 4%, respectively) could be explained by stream velocity (see Figures 3-4 and 3-5). Thus, current velocity is not a strong predictor of the abundance and distribution of submersed aquatic vegetation in this river.


ICHETUCKNEE RIVER

0.00

0.05

0.10

0.15

0.20

0.25

0.30

0 5 10 15 20 25 30

TRANSECT

FLO

W (m

/s)

Figure 3-3. Mean transect flowvelocity (m/s) for the Ichetucknee River on April 30th 2003.

0

2

4

6

8

10

12

14

SAV

Biom

ass

(kg/

m2)

0 .1 .2 .3 .4 .5 .6Flow (m/s)

Figure 3-4. Relationship between SAV biomass and flow in the Ichetucknee River on April 30th 2003.


0

20

40

60

80

100

Mea

n SA

V Pe

rcen

t Cov

erag

e

.10 .15 .20 .25Mean Flow (m/s)

Figure 3-5. Relationship between SAV coverage and flow in the Ichetucknee River on April 30th 2003. Measured canopy cover values ranged from 0 to 100%, with an average of 40% (Figure 3-6). As previously noted, SAV is dependent on adequate light availability. Shading from terrestrial vegetation has been linked to SAV abundance and distribution in stream systems (Canfield and Hoyer 1988). We observed no such relationships between terrestrial canopy coverage and SAV biomass or coverage (Figures 3-7 and 3-8, respectively). While there was a subtle decline in SAV as terrestrial canopy cover increased, it was not statistically significant. Although the presence of a terrestrial canopy certainly can reduce incident surface light, other environmental parameters such as stream orientation or angle of sun inclination may give better estimates of SAV cover or biomass at fixed stream locations. We noted that large amounts of SAV were often measured in shaded portions of the river, but it is possible that the plant growth (production) is reduced in these shaded areas relative to more open areas in the river. If so, then plants occurring in these areas may be more susceptible to further reductions in the light field or other disturbances.


ICHETUCKNEE RIVER

0

20

40

60

80

100

0 5 10 15 20 25 30 35

TRANSECT

TER

RES

TRIA

L C

AN

OPY

CO

VER

(%)

Figure 3-6. Mean transect canopy cover (%) for the Ichetucknee River on April 30th 2003.

0

2

4

6

8

10

12

14

SAV

Biom

ass

(kg/

m2)

0 20 40 60 80 100Terrestrial Canopy Cover %

Figure 3-7. Relationship between SAV biomass and canopy cover in the Ichetucknee River on April 30th 2003.


0

20

40

60

80

100

SAV

Cov

erag

e (p

er m

)


Figure 3-8. Relationship between SAV coverage and canopy cover in the Ichetucknee River on April 30th 2003.

Measured values for the vertical light attenuation coefficient at transects 1, 5, 6, and 7 ranged from 0.49 to 0.71 (Kd/m) with an average of 0.59 (Kd/m). These values suggest that Kd values increase with distance downstream, potentially as a result of an increase in suspended particles in the water column. Light attenuation coefficients are integrated measures of the amount of light reduction with depth. In the aquatic environment, light is absorbed and reflected by suspended particles (algal and non-algal), dissolved material (humics) and by the water itself. If any one of these light-attenuating factors is increased, then the light available for SAV photosynthesis will be reduced. Using our minimum and maximum estimates of light attenuation (Kd of 0.49 to 0.71/m), SAV in the Ichetucknee River should have sufficient light (>10% of incident irradiance) to a depth of 3.2 to 4.7 meters. The euphotic depth is the depth beyond which light levels are less than some percentage of surface irradiation (approximately 1% for phytoplankton and 10% for macrophytes). Below this level, it is generally accepted that net positive photosynthesis by plants and algae does not occur (Scheffer 1998) and, if the low light environment is persistent, plants and algae should not be expected to occur. Given that the present euphotic depth is greater than the water column depth, light limitation of SAV should not occur in the Ichetucknee River unless water clarity declines. Temperatures, at the time of sampling, ranged from 21.8 to 23.8 deg. C, with an average of 23.1 deg. C. Mean transect temperature values gradually increased with distance downstream from the head spring until approximately transect 14, at which point they remained relatively stable (Figure 3-9). The mean temperature for transects 14 through 31 was 23.6 deg. C. These gradual increases in temperature were expected as a result of increasing solar heating within the less


canopied Rice Marsh, and also the lack of significant spring flows in the lower reaches of the river. Specific conductivity values ranged from 309 to 348 uS/cm (at 25 deg. C), with an average of 327 µS/cm. Mean transect specific conductivity values generally increased with distance downstream (Figure 3-10).

ICHETUCKNEE RIVER

21.0

21.5

22.0

22.5

23.0

23.5

24.0

0 5 10 15 20 25 30

TRANSECT

TEM

PER

ATU

RE

(°C

)

Figure 3-9. Mean transect temperature(°C) for the Ichetucknee River on April 30th 2003.

ICHETUCKNEE RIVER

305

310

315

320

325

330

335

340

345

0 5 10 15 20 25 30

TRANSECT

SPEC

IFIC

CO

ND

UC

TIVI

TY (µ

S/cm

)

Figure 3-10. Mean transect specific conductivity (µS/cm at 25 °C) for the Ichetucknee River on April 30th 2003.


Dissolved oxygen (DO) values ranged from 3.6 to 8.1 mg/L, with an average of 6.4 mg/L. In the upper river, dissolved oxygen concentrations rapidly increased with distance downstream from the main spring. At transect 14, values declined (Figure 3-11). These observed trends in dissolved oxygen concentration are consistent with other vegetated spring-fed rivers (Frazer et al. 2001), in which the ground water emanating from spring vents has low DO values, and rapidly increases due to photosynthesis by SAV and atmospheric diffusion.

ICHETUCKNEE RIVER

2.0

3.0

4.0

5.0

6.0

7.0

8.0

9.0

0 2 4 6 8 10 12 14 16 18 20 22 24 26 28 30 32

TRANSECT

DIS

SOLV

ED O

XYG

EN (m

g/L)

Figure 3-11. Mean transect dissolved oxygen (mg/L) for the Ichetucknee River on April 30th 2003. Measured pH values ranged from 7.2 to 7.9, with an average of 7.7. A gradual increase in pH was noted (Figure 3-12). Given the abundance of SAV in the river and the trend of dissolved oxygen and pH values simultaneously increasing downstream, we attribute the changes in pH to a decline in carbon dioxide as SAV utilizes this gas during photosynthesis. Eight SAV species of submersed aquatic vegetation were observed within sample quadrats. In order of rank abundance they were as follows: Sagittaria kurziana (strap-leaf sagittaria) at 54%, Zizania aquatica (wild rice) at 17%, Vallisneria americana (tape grass) 10%, Chara sp. (muskgrass) at 6%, Vaucheria sp. (filamentous algae) at 5%, Fontinalis sp. (watermoss) at 3%, Ludwigia repens (red ludwigia) at 2%, and Hydrocotle sp. (dollar weed) at 1% (Figure 3-13). These values for the dominant species are nearly identical to the values calculated from the SAV maps, and provide further quality assurance for the mapping effort. Two species Nasturtium officinale (watercress) and Myriophyllum heterophyllum (foxtail) were observed outside of sampled quadrats. The three dominant species Sagittaria kurziana, Zizania aquatica, and Vallisneria americana, together comprised 81% of the observations, indicating that relatively few species contribute to the majority of the SAV cover present in the Ichetucknee River.


ICHETUCKNEE RIVER

7.0

7.2

7.4

7.6

7.8

8.0

0 5 10 15 20 25 30

TRANSECT

pH

Figure 3-12. Mean transect pH for the Ichetucknee River on April 30th 2003.

IC H E T U C K N E E R IV E R

0 1 0 2 0 3 0 4 0 5 0 6 0

N o n e

C h a ra

F o n t in a lis

H y d ro c o ty le

L u d w ig ia re p e n s

S a g it ta r ia k u rz ia n a

V a llis n e r ia a m e r ic a n a

V a u c h e r ia

Z iz a n ia a q u a t ic a

FREQ

UEN

CY

OF

OC

CU

RR

ENC

E B

Y SP

ECIE

S

P E R C E N T

Figure 3-13. Frequency of occurrence for the dominant SAV species sampled in the Ichetucknee River on April 30th 2003.

Within the sampled quadrats, SAV coverage ranged from 5 to 100 %, while mean cover values for transects ranged between 44 and 100 %. The sampled river had a mean SAV coverage value of 71 %. Mean transect SAV coverage gradually increased with distance downstream (Figure 3-


14). Mean SAV coverage (by transect) and mean depth (by transect) were positively correlated (Figure 3-15, r2 = 0.26), further suggesting that depth is not limiting SAV growth in the Ichetucknee River. We observed a weak positive correlation between stream flow and SAV coverage (r2 = 0.10; p = 0.09) (Figure 3-5). However, as flow rates are moderate in the Ichetucknee River (see above), it is not likely that the abundance and distribution of SAV would be largely affected by naturally occurring variations in stream flow rates. When comparing SAV coverage to canopy cover, we observed a decline in SAV coverage with increasing canopy cover, but the relationship was not statistically significant (Figure 3-8).

ICHETUCKNEE RIVER

0

20

40

60

80

100

120

0 5 10 15 20 25 30

TRANSECT

SAV

PER

CEN

T C

OVE

RA

GE

Figure 3-14. Mean transect SAV percent coverage for the Ichetucknee River on April 30th 2003.

Within sampled quadrats, SAV biomass values ranged from 0.14 to 13.8 kg/m2 wet weight, while mean values (by transect) ranged between 2.4 and 8.0 kg/m2 wet weight. The sampled river average was 4.7 kg/m2 wet weight. SAV biomass generally increased with distance downstream (Figure 3-16). SAV biomass was positively correlated with depth (r2 = 0.20, Figure 3-17), largely because SAV leaf (blade) length tended to be greater in the lower river where depths were also generally greater. The potential for a reduction in SAV biomass as river depths decline may exist based on this empirical relationship. SAV biomass and stream flow were positively correlated (r2 = 0.13) (Figure 3-18), suggesting (as above) that stream flow does not reach velocities which are inhibitory to SAV biomass in the Ichetucknee River. Finally, we observed a qualitative decline in SAV biomass as terrestrial canopy coverage increased, but the relationship was not statistically significant (Figure 3-7).


0

20

40

60

80

100

Mea

n SA

V Pe

rcen

t Cov

erag

e

1.0 1.5 2.0 2.5Mean Depth (m)

Figure 3-15. Relationship between SAV coverage and depth in the Ichetucknee River on April 30th 2003.

ICHETUCKNEE RIVER

0

1

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5

6

7

8

9

10

0 5 10 15 20 25 30

TRANSECT

SAV

BIO

MA

SS (k

g/m

2 wet

wei

ght)

Figure 3-16. Mean transect SAV biomass (kg/m2 wet weight) for the Ichetucknee River on April 30th 2003.


0

2

4

6

8

10

12

14

SAV

Biom

ass

(kg/

m2)

.0 .5 1.0 1.5 2.0 2.5 3.0 3.5Depth (m)

Figure 3-17. Relationship between SAV biomass and depth in the Ichetucknee River on April 30th 2003.

0

2

4

6

8

10

12

14

SAV

Biom

ass

(kg/

m2)

0 .1 .2 .3 .4 .5 .6Flow (m/s)

Figure 3-18. Relationship between SAV biomass and flow in the Ichetucknee River on April 30th 2003.


Twenty-seven samples from 10 different transects were collected to estimate periphyton abundance (mg chlorophyll per g of host macrophyte wet weight). Periphyton abundance ranged from 0.01 to 0.37 mg chl/g host plant wet weight, with the sampled river average equal to 0.106 mg chl/g host plant wet weight. Mean transect periphyton abundance generally declined with distance downstream, although peak abundance was observed at transect 11 (in the Rice Marsh zone of the river) (Figure 3-19). Periphyton abundance has commonly been correlated to water column nutrient concentrations, stream flow and light availability (e.g., Notestein et al. 2003 and references therein). Although nutrient data were not collected, we may assume that water column nutrient concentrations were highest at the spring vents and declined with distance downstream, as we have observed in other spring-fed river systems (Frazer et al. 2001). A decline in water column nutrients with distance downstream may result in a decline in periphyton abundance. A negative correlation between stream flow and periphyton abundance (r2 = 0.46) was observed when comparing mean transect values (see Figure 3-20). This suggests that as stream flow increases, periphyton may be dislodged at higher rates. Reductions in stream flow could, in turn, facilitate higher periphyton abundance, and negatively impact the SAV community. A negative correlation between terrestrial canopy cover and periphyton abundance (r2 = 0.45) was also observed when mean transect values were compared (Figure 3-21), suggesting that periphyton abundance may be correlated with light availability, as has been reported in other river systems (e.g. Hill and Harvey 1990). Greatest light availability was found in the Rice Marsh reach.

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Figure 3-19. Mean transect periphyton abundance (mg chl/g host plant wet weight) for the Ichetucknee River on April 30th 2003.


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Figure 3-20. Relationship between periphyton abundance and flow in the Ichetucknee River on April 30th 2003.

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Figure 3-21. Relationship between periphyton abundance and canopy cover in the Ichetucknee River on April 30th 2003.


Six different categories of river substrate were observed. By order of abundance they were: mud, sand, rock, shell fragments, mud/sand and sand/rock (Figure 3-22). In general, the substrate was dominated by mud (47%) and sand (39%). The prevalence of mud and sand suggests that most of the river bottom is suitable for SAV colonization and growth.

ICHETUCKNEE RIVER

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Figure 3-22. Histogram of sediment types in the Ichetucknee River on April 30th 2003.

Ichetucknee SAV in comparison to other Florida spring-fed rivers A comparison between the SAV community within the Ichetucknee River and four other spring-fed rivers was made possible based on prior research (Frazer et al. 2001) conducted during the summers of 1998, 1999 and 2000. The other four rivers, Crystal, Homosassa, Chassahowitzka and Weeki Wachee, like the Ichetucknee, are primarily spring-fed. Each of the four latter rivers, however, discharges directly into the Gulf of Mexico and all are tidally influenced. As the spring-fed coastal rivers were sampled during three consecutive summers, we report (as appropriate) mean values by river and ranges within each river over the three year time period. Within the Ichetucknee River, approximately 98% of the stations sampled had at least some SAV present. Within the other spring-fed rivers, we observed that the percentage of sampled river bottom with SAV was less: 42% in the Crystal River, 72% in the Homosassa River, 85% in the Chassahowitzka River and 84% in the Weeki Wachee River. The Ichetucknee River has a high prevalence of SAV and the majority of the SAV is due to two species, Sagittaria kurziana and Vallisneria americana, which had a combined frequency of occurrence of 74%. In the comparative systems, Sagittaria kurziana and Vallisneria americana were rarely dominant. In fact, the combined occurrences of these two species were only 19%, 6%, 32% and 19% (three year average, 1998 to 2000) for the Crystal, Homosassa, Chassahowitzka and Weeki Wachee Rivers, respectively.


In comparison to these four coastal spring-fed rivers, the Ichetucknee River can be characterized as highly vegetated with a relatively small number of dominant native submersed aquatic species. It is worth noting also, that in the four coastal spring-fed rivers, filamentous algae (e.g., Lyngbya, Enteromorpha and Chaetomorpha) were common and frequently abundant to the point of nuisance levels. Additionally, non–indigenous species such as Hydrilla verticillata and Myriophyllum spicatum were commonly observed, and at times were the dominant representatives of the SAV community. This is in stark contrast to the Ichetucknee River. Although SAV coverage was not estimated in the four coastal rivers, biomass was measured at all sampling stations. The mean biomass of SAV within the Ichetucknee River was higher than the four comparative rivers (Table 4-1), and the maximum observed biomass within an individual sampling quadrat in the Weeki Wachee River was the result of a dense bed of Hydrilla verticillata (Frazer et al. 2001). These data suggest that factors which are known to influence the abundance and distribution of SAV, i.e. available light, stream flow, sediment type, grazing and/or salinity, are relatively favorable within the sampled portions of the Ichetucknee River compared to other nearby spring-fed rivers. Table 4-1. A comparison of SAV biomass between five Florida spring-fed rivers. Ichetucknee River statistics are derived from data collected on April 30, 2003 (N = 155), while the other four rivers statistics are from data collected during August of 1998, 1999 and 2000 (N = 300).

River Mean SAV Biomass (kg/m2)

Minimum SAV Biomass (kg/m2)

Maximum SAV Biomass (kg/m2)

Ichetucknee 4.66 2.4 8.0

Crystal 0.42 0.0 2.6

Homosassa 0.71 0.0 4.4

Chassahowitzka 1.44 0.0 5.5

Weeki Wachee 3.86 0.0 21.4


4.0 Macroinvertebrate Sampling 4.1 Introduction Springs and spring-fed rivers provide important habitats for diverse biological communities. A summary describing the current body of research regarding freshwater macrofauna in Florida’s karst habitats was recently prepared by Walsh (2001). The FDEP and researchers at the University of Florida have conducted benthic macroinvertebrate sampling at Ichetucknee Springs and several other spring systems throughout the state (FDEP, 1997; Woodruff, 1993). However, few studies exist which describe the epibenthic or SAV-associated macroinvertebrate communities in spring-fed systems. The most recent monitoring results by FDEP indicate that stream health in the Ichetucknee River system falls midway between Fair and Healthy on the stream index scale with water quality data indicating elevated levels of nitrates (FDEP, 2002). The spatial distribution, abundance, and diversity of SAV and associated epibenthic macroinvertebrate communities, are often utilized to assess the heath of aquatic ecosystems (Thorp, 1997). Benthic macroinvertebrates and SAV are strong indicators of environmental health as they are sensitive to ambient stress imposed by fluctuations in water quality, water quantity, and temperature. Stress tends to reduce the number of different types of organisms present in aquatic systems. Additionally, special emphasis is given to certain taxa that are known to be highly sensitive to pollution (FDEP, 1996). Studies have been conducted identifying the roles of certain taxa within the trophic dynamic of aquatic systems. SAV typically supports a more diverse and higher density population of macroinvertebrates when compared with other open water habitats in the same vicinity (Balci, 2003). Additionally, taxa richness and taxa abundance fluctuate between different species of SAV. In the Ichetucknee River, the SAV community is primarily comprised of Vallisneria americana, Sagittaria kurziana, Zizania aquatica, and Chara sp. SAV-associated macroinvertebrate sampling was conducted throughout the Ichetucknee River concurrently with the SAV mapping effort. This biological data will be used to assess the current health of the macroinvertebrate community and for comparisons between SAV species, river reach (Headspring vs. Rice Marsh vs. Floodplain), flow, and depth. 4.2 Materials and Methods This study was conducted at 31, evenly distributed stations along the Ichetucknee River, beginning at the headsprings of the Ichetucknee State Park down to the most downstream canoe take out point near the U.S. 27 bridge. SAV-associated macroinvertebrate sampling was conducted at the same stations described in the SAV sampling section described above. The sampling stations are the same as shown in Figure 3-1 above. The river was divided into the following three reaches, which corresponds to the different levels of shading created by the canopy: Headspring Reach (heavily canopied), Rice Marsh (little to no canopy), Floodplain Reach (heavily canopied). Sampling was performed by canoe, snorkeling, and SCUBA in deeper reaches of the river. At each of the 31 sites (transects), the total width of the stream was measured. From the total width, three stations where chosen and labeled: one in the middle, and two equidistant between the middle and far edges. The stations were labeled A, B, and C, respectively, with A always occurring on the left side of the river while facing upstream (typically the west side of the river),


all B stations in the middle of the river, and all C stations on the right side of the river. At each transect, ambient weather conditions were recorded along with a brief description of the shoreline on either bank. At each station (A, B, and C) that was vegetated, SAV/macroinvertebrate samples were collected using an elongated nitex mesh bag with a square metal frame at the open end and a sample collection jar at the closed end. The bag was lowered quickly over each site. The vegetation that occurred within the squared open end were cut approximately one inch above the substrate and allowed to float up into the mesh bag. The sample was then brought to the canoe for processing. SAV blades were carefully transferred to pre-weighed, labeled sample containers. The remaining biota in the net was rinsed down to the sample jar at the closed end. The excess water was drained through the net and the sample added to the labeled sample container. Any remaining sample was rinsed down with a squirt bottle using as little water as possible. The sample was than weighed in grams to obtain a wet weight. The sample was then preserved immediately in 10% formalin. At each A, B, and C station, an underwater photograph was taken prior to sample collection. Subsequently, an estimate of the percent cover at each station was conducted using the Braun-Blanquet index of vegetation cover. This index includes identifying all species represented in a standardized area, then assigning each one of the following codes: 0: species not present, 1: species <5 percent of total, 2: species = 5-10 percent of total; 3: species = 10-25 percent of total; 4: species = 25-50 percent of total; 5: species 50-90 percent of total; 6: species = >90 percent of total. Ranges of percent cover are expressed as numerical values. Also noted at each station was the presence or absence of epiphytes and any other pertinent observations. Copies of field notes are provided in Appendix E. In the lab, all macroinvertebrates were subsequently rinsed from the SAV blades and transferred to glass jars and preserved in ethanol. Subsequently they were sorted, enumerated, and identified to the lowest possible taxon. However, due to the high abundance of macroinvertebrates, subsampling was conducted. A glass pan, (approx. 13” x 9” x 2”) was sectioned into identical squares labeled 1 through 40. Individuals were removed and enumerated from a randomly chosen square until 100 animals were counted. Once 100 animals were counted, the remainder of the square was enumerated. If 100 animals were not present within the area of one square, a second would be randomly selected etc., until a count of 100 was reached. A different subsampling method was used for oligochaetes. Due to large numbers of individuals, oligochaetes were subsampled by randomly selecting at least 6 individuals from each sample and identifying to genus and/or species. Three SAV blades (excluding Chara) were measured to calculate an average blade length for each sample. No B samples were collected at stations 13 or 18 due to a lack of SAV in the middle portion of the river. All statistical comparisons were conducted at the 95% confidence level (p<0.05). 4.3 Results and Discussion Results are presented for all mid-river or B sampling stations. A total of 31,539 individuals representing 69 species of macroinvertebrates were identified during this sampling effort. Chironomids dominated the samples and represented approximately 91.8% of all samples combined, followed by Hydracarina sp. (4.3%), Petrophilla sp. (1.2%), Hydroptila sp. (0.7%), and Oxyethira sp. (0.5%). A list of all macroinvertebrate species identified from B stations for the 31 transects is provided in Appendix F. Chironomid taxa are presented in Appendix G.


The results indicate that the number of individual macroinvertebrates and the number of different macroinvertebrate taxa vary between the three river segments (Headspring reach, Rice Marsh, Floodplain reach) (Table 4-1, Figure 4-1). The lowest number of taxa represented within the samples occurred in the Floodplain reach, ranging from 3 to 15 individuals (Figure 4-2). Due to the large number of individual chironomids, this group is represented as one taxa. The Floodplain reach includes transects 15 through 31, and is the furthest downstream and the longest portion of study area. This segment of the river also had the highest percent canopy cover, the highest temperature, the highest flow velocities, and the lowest periphyton abundances. The number of individual macroinvertebrates within the Floodplain reach was as low as 19 animals and as great as 3,319 animals, with an average of 701 individuals. Table 4-1. Mean values for SAV-associated macroinvertebrate abundance and taxa for the Ichetucknee

River. River Reach Range of Abundance Mean Abundance Range of Taxa Mean # of Taxa

Headspring 65-890 376 5-12 8Rice Marsh 369-5337 2364 6-18 12Floodplain 19-3319 701 3-15 8 The Rice Marsh segment of the river included transects 5 through 14, and is the most open reach with respect to canopy cover. The number of individuals was consistently higher within this segment (Figure 4-1). The mean abundance was 2,364, and the greatest number of individuals in a transect was 5,337. The mean abundance and mean number of taxa were significantly higher within the Rice Marsh reach, compared to the other two river segments The highest periphyton abundance was also found within this segment of the spring run.

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Figure 4-1. SAV-associated macroinvertebrate abundance at transects along the Ichetucknee River.


The Headspring reach included transects 1 through 4 and is the shortest segment of the river reach, as defined by this study. This area is also heavily canopied and had the lowest temperatures and depths. The mean number of taxa was the same as the floodplain reach though the mean number of individuals was lower than the other two river segments. This may be due to a lower sample size compared to the Rice Marsh and Floodplain reaches which had between 10 to 15 transects each.

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Figure 4-2. Numbers of SAV-associated macroinvertebrate taxa at transects along the Ichetucknee

River. As previously stated, the Chironomids were not identified to family or genus; however approximately six, randomly selected, individuals were identified to the lowest practical taxon and include the following: Chironomus sp. (gatherer), Cricoctopus sp. (grazer/gatherer), Dicrotendipes sp. (gatherer), Labrundinia sp. (predator), Labrundinia pilosella (predator), Paratanytarsus sp. (gatherer), Pentaneura sp. (predator), Polypedilum convictum (gatherer), Polypedilum illinoesnse gatherer), Procladius sp. (predator), Pseudochironomus sp. (gatherer), Tanytarsus sp. (gatherer), and Thienemanniella sp. (grazer). Of the individuals identified, Dicrotendipes sp. was the dominant taxa, comprising 42% of the total. Macroinvertebrate abundance was negatively correlated with canopy cover (p=0.026) (Figure 4-3). The greatest canopy cover occurred in the Headspring and Floodplain reaches compared to the Rice Marsh which had little to no canopy cover over the main river channel. Mean abundance was significantly greater in the Rice Marsh compared to the Headspring (p=0.0006) and Floodplain (p=0.0003) reaches, but was not significantly different between the Headspring and Floodplain reaches (p=0.87). Mean number of taxa was also negatively correlated with canopy cover (Figure 4-4) and was significantly greater at the Rice Marsh than at the Floodplain reach (p=0.01, n=24). However, there were no significant differences between the Rice Marsh and the Headspring (p=0.11), nor between the Headspring and Floodplain reaches (p=0.76).


Scatterplot (Ichetucknee.STA 11v*27c)y=1932.007-18.78*x+eps

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Figure 4-3. Relationship between macroinvertebrate abundance and average canopy cover (%) in the Ichetucknee River.

Scatterplot (Ichetucknee.STA 11v*27c)y=11.489-0.056*x+eps

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Figure 4-4. Relationship between number of macroinvertebrate taxa and average canopy cover (%) in the Ichetucknee River.


Both abundance (r2 = 0.68, p= 0.006) and number of taxa (r2 = 0.48, p= 0.04) were also correlated with periphyton abundance (mg chl/g host plant wet weight) (Figures 4-5 and 4-6). As described in the previous section, greatest periphyton abundance was found in the Rice Marsh area compared to the Headspring and Floodplain reaches.

The Ichetucknee River is classified as a first-magnitude Florida spring, which is defined as having a discharge of greater than 100 cubic feet per second (cfs). Water velocity is considered to be critical to this type of lotic freshwater community, which is usually dominated by rheophyllic organisms (DEP, 1998). Although there were no significant differences in the number of taxa or abundance with respect to flow velocity, certain species of the following groups are considered to be “current loving”, all of which were observed during this study: Colleoptera, Emphemeroptera, Plecoptera, Tricoperta, Odonata, and Diptera, Oligochaeta (Naididae). The general morphology of SAV influences the colonization and the type of epiphytic macroinvertebrate community that will coexist. However, other factors such as epiphyton biomass, predation pressure, and seasonal variations can affect the distribution and abundance of macroinvertebrates (Balci, 2003). Interestingly, there were no significant differences in the number of taxa (p=0.10) or abundance (p=0.94) with respect to SAV species (Vallisneria, Zizania, Sagittaria, or Chara) or wet weight, indicating that macroinvertebrates were widely distributed among the in-stream vegetation. Several previous studies have shown that Chironomids are one of the most abundant and diverse macroinvertebrate groups that exist within SAV communities of Florida streams (Warren et al., 2000; FDEP, 1998). Chironomid larvae area an important food source for many freshwater fish and other invertebrate species and their role within aquatic systems has been well established (Menzie, 1980). The trophic functions of a majority of the species within this group have been identified as grazers and gatherers. This invertebrate community structure is generally associated with desirable species of SAV, indicative of sufficient water velocity and water quality (Warren 2000). Though an increase in % percent Diptera generally implies lower water quality, diversity among the chironomids is indicative of good stream conditions (FDEP, 1997). Though diversity within the Chironomids was only subsampled, the abundance of animals present was high. The relationship between the dominant SAV-associated taxa (Chironomids), their predicted feeding types (grazer/gatherer), and periphyton abundance (periphytic algae) was statistically significant. As percent canopy cover decreased within the different reaches of the river, periphyton increased along with the macroinvertebrate abundance. Periphyton was more abundant in the Rice Marsh reach where there is less canopy cover and greater light availability.


Scatterplot (Ichetucknee.STA 12v*27c)y=-215.234+12459.7*x+eps

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Figure 4-5. Relationship between macroinvertebrate abundance and periphyton abundance in the

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Scatterplot (Ichetucknee.STA 12v*27c)y=-291.338+161.716*x+eps

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Figure 4-6. Relationship between number of macroinvertebrate taxa and periphyton abundance in the

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5.0 Recreational Use Impact Assessment 5.1 Introduction Recreational activity has probably been the most important factor affecting the health of the Ichetucknee River and associated SAV beds from the 1970s to present. Monitoring by Park staff has indicated a relatively consistent trend of declining SAV coverage during the high use summer period, followed by an increase in coverage through the spring. The rate of decline in SAV coverage may be due to combination of recreational use and other factors such as long-term changes in surface and groundwater levels. Daily limits on the number of recreational users are set at 750 for the Upper tube launch, and 2250 for the Midpoint tube launch; an unlimited number of tubers may enter the river at the Dampier’s Landing tube launch. These limits were established on the basis of studies which evaluated the kinds and amounts of damage that swimming, canoeing, diving, and tubing had on the aquatic communities (Dutoit, 1979; MacLaren and Younker, 1989). Using SAV and park use data collected by Ichetucknee Park staff and available hydrologic data, relationships between water levels and changes in SAV coverage were analyzed after periods of heavy recreational use to determine if damage is greater during times of drought and/or low water levels. 5.2 Methods The Park Service at Ichetucknee Springs has collected transect data since 1989 at 17 transects in the park to evaluate recreational impacts. These locations are shown and labeled by transect number in Figure 5-1. These data are typically collected in April/May, prior to the start of the high use summer period, and in late fall following the peak use period. This information allows the park staff to evaluate impacts caused by heavy use in the summer and then recovery of vegetation during the winter. Changes in vegetation cover for the dominant species at each transect were calculated for each spring and summer monitoring period. Long term rainfall data were obtained for the Lake City

Figure 5-1. Ichetucknee Park transect locations (in blue).


precipitation station to evaluate trends in the recharge area of the springs. Long term groundwater level data (Tin Lizzie well) provided by the District in the vicinity of Ichetucknee Springs was also evaluated to determine if relationships exist with respect to trends in SAV coverage. Park staff has also collected water level data at the head spring since the 1990s. The Park staff has also collected depth soundings along each transect and stage data at the headsprings and headsprings run. The intensity of disturbance with respect to changes in stage was evaluated using this data. Trends were analyzed to determine if relationships exist between stage, water depth, and vegetation cover changes along each spring run along with changes in recreational use (park use statistics). Park use statistics are collected and analyzed by Park staff annually to determine if the carrying capacity of the river has been exceeded and if closings are needed to allow recovery of SAV. Carrying capacity, in this case, can be defined as the rate of use at which damage is equal to the natural ability of each plant community to recover (Dutoit, 1979). 5.3 Results and Discussion Heaviest park use occurs between June and August - this pattern has been consistent since the 1980s (Figure 5-2). Park use declined at the north river area of the park from over 85,000 visitors in the late 1980s to as low as approximately 40,000 visitors in the early 1990s. North river use has been relatively stable at approximately 50,000 to 60,000 visitors since 1995 (Figure 5-3). In the south river area, park use has slowly risen since 1991 from approximately 65,000 visitors to over 100,000 visitors in 1999. A slight declining trend has occurred in both the north and south river since 1999/2000 and 2002.

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Figure 5-2. Changes in park use over between January and December annuall at Ichetucknee Springs State Park.


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Figure 5-3. Changes in river use at Ichetucknee Springs and River since 1987. Long term rainfall trends from the Lake City gage appear to have declined since the El Nino period between 1997 and 1998 (Figure 5-4). Droughty conditions were observed throughout the state during most of 1999 through 2002. These declining rainfall trends resulted in declining water levels measured at the headspring run of the Ichetucknee River (data provided by Sam Cole, Ichetucknee State Park) (Figure 5-5). It appears that the heaviest park usage has also occurred during the declining limbs of the seasonal peaks in water level at the headspring. Declines in vegetation cover for the headspring transects (4-1, 4-2, 5-1, 5-2) also appear to suffer the greatest declines during the drought conditions beginning in 1998/1999. As a result, these transects were selected for further analysis with respect to water level fluctuations.

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Figure 5-4. Trends in rainfall at Lake City, Florida.


Park usage also peaked in 1999 which coincides with the steepest decline in water levels (blue line, dashed blue line indicates trend line) and the most severe decline in SAV (Sagittaria) percent cover at transect 5-1 (red line in bottom graph). Figure 5-6 shows that the trend in SAV percent cover over time at this transect has declined since 1996, but has recently increased to pre-drought conditions in 2003. This may be due to the recent rainfall increases and headspring water levels observed in the early spring of 2003. SAV percent cover (primiarily Sagittaria) at transect 4-1 (light blue line in bottom graph), however, has not shown a similar response to transect 5-1 and, in fact, has increased significantly since 1997, in spite of the drought and lowered water levels (Figure 5-7). This transect may be located in an area where tubers or swimmers are less likely to touch the bottom or walk.

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Figure 5-5. Trends in park usage and water levels (above) and change in vegetation coverage (below) in the Headspring Reach at Ichetucknee Springs.


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Figure 5-6. Trends in SAV percent cover at transect 5-1 in the Ichetucknee State Park..

Ichetucknee Springs State ParkSpring/Fall Vegetative Cover, Transect 4-1

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Figure 5-7. Trends in SAV percent cover at transect 4-1 in the Ichetucknee State Park.


Changes in SAV cover were analyzed with respect to headspring water level, groundwater levels (Tin Lizzie well), and park usage (number of people) (Table 5-1). The only significant (p<0.05) correlation was observed between headspring water level and percent change in vegetation at transect 5-2 (Table 5-2, Figure 5-8). However, similar non-significant trends were also observed at transects 4-1 and 5-1 (Figure 5-9). Relationships between groundwater levels and vegetation change were not significant for any of the headspring transects, however, trends were typically similar to those for headspring water levels at transects 4-2 and 5-2 (Figure 5-10).

Table 5-1. Water level, park usage, and Ichetucknee Park monitoring transect vegetation change data used for regression analysist.

Year

Head Spring Run Stage (ft. NGVD)

Park Usage (# of people)

4-1 Veg Change %

4-2 Veg Change %

5-1 Veg Change %

5-2 Veg Change %

Tin Lizzie Water Level (ft. NGVD)

1989 No Data 62,424 -1.4 No Data 6 No Data 20.461990 24.57 50,872 -2.6 No Data -26.4 No Data 18.781991 25.40 42,105 -0.2 No Data -30.6 No Data 23.291992 25.09 48,685 -7.2 No Data -12.6 No Data 24.011993 24.98 51,606 -10.4 No Data -12 No Data 20.741994 25.35 45,424 -6 No Data -12.6 No Data 22.941995 25.03 49,654 0.3 No Data -37.3 No Data 20.841996 24.94 53,881 -7.9 No Data -50.6 No Data 20.581997 25.27 53,859 2.3 No Data -9.1 No Data 19.971998 25.16 55,308 -0.5 No Data -27.5 No Data 22.771999 25.11 58,053 -6.9 -29 -18.5 -4.6 19.892000 25.03 60,694 -11.2 -2.8 -0.9 -8.3 19.612001 24.70 56,676 -6.2 -17.7 -34.7 -14.6 19.82002 24.51 55,230 2.9 -39 -33.6 -23.3 18.84

Table 5-2. Regression statistics (p-values) between water level and park usage variables against percent change in vegetation at Ichetucknee Park monitoring transects.

4-1 4-2 5-1 5-2Headspring Water Level 0.84 0.46 0.21 0.02Groundwater Level (Tin Lizzie Well) 0.90 0.18 0.85 0.14Park Use (No. of People) 0.62 0.14 0.25 0.22

Transect

Independent Variable


Head Spring Stage vs. % Change in SAV Cover at Transect 5-2

y = 28.697x - 725.44R2 = 0.9682 (p=0.02)

-25

-20

-15

-10

-5

024.40 24.50 24.60 24.70 24.80 24.90 25.00 25.10 25.20

Stage (ft NGVD)

% C

hang

e in

SAV

Cov

er

5-2 Veg ChangeLinear (5-2 Veg Change)

Figure 5-8. Relationship between change in SAV percent cover at transect 5-2 and headspring water level in the Ichetucknee State Park.

Head Spring Stage vs. % Change in SAV Cover at Transect 5-1

y = 36.404x - 937.94R2 = 0.2433

-60

-50

-40

-30

-20

-10

024.40 24.60 24.80 25.00 25.20 25.40 25.60

Stage (ft NGVD)

% C

hang

e in

SAV

Cov

er


Figure 5-9. Relationship between change in SAV percent cover at transect 5-1 and headspring water level in the Ichetucknee State Park.


Tin Lizzie Well Level vs. % Change in SAV Cover at Transect 5-2

y = 14.701x - 299.89R2 = 0.7367 (p=0.14)

-25

-20

-15

-10

-5

018.6 18.8 19 19.2 19.4 19.6 19.8 20

Stage (ft NGVD)

% C

hang

e in

SAV

Cov

er


Figure 5-10. Relationship between change in SAV percent cover and groundwater level at transect 5-2 in the Ichetucknee River State Park.

Park usage was also not significantly related to vegetation change at any of the transects. This lack of trend may be due to the high numbers of park visitors during the last several years and also the lack of sufficient data for transects 4-2 and 5-2 to make adequate statistical inferences. For example, in 1989 approximately 62,424 people used the north run of the river yet only a slight change in vegetation cover was observed at transects 4-1 and 5-1. In fact, an increase in cover was observed at transect 5-1. The following year, fewer visitors were recorded, yet a large change in percent cover was observed at transect 5-1 and this appears to be more related to head spring stage than park usage. This pattern is also present during 1996, 2001, and 2002. Based on the table below, it appears that the greatest percent change in vegetation cover occurs when headspring water levels drop below 25.0 ft. NGVD, regardless of park usage. Future trend analysis may be more easily analyzed through the use of SAV and depth contour maps. Although extremely useful, the transect information may not provide sufficient data to estimate widespread changes in SAV coverage over time with respect to water levels or park usage. Based on the SAV map for the headspring area, it is obvious that losses occur immediately adjacent to and downstream of the north tube launch area (Figure 5-11). Mapping of SAVin this area over time, in conjunction with transect sampling, would allow the calculation of changes in total SAV acreage and percent cover within different zones of the headspring run and also the extent downstream (e.g., linear feet) of losses or gains.


Figure 5-11. SAV map (2003) showing all SAV species (in green) in the upper headspring reach of the Ichetucknee River.


6.0 References Allan, J.D. 1995. Stream ecology: structure and function of running waters. 1st Edition.

Chapman and Hall, London, England. Balci, P., Kennedy, J. H. 2003. Comparison of chironomids and other macroinvertebrates

associated with Myriophyllum spicatum and Heteranthera dubia. Journal of Freshwater Ecology, Volume 18.

Butcher, R. W. 1933. Studies on the ecology of rivers. I. On the distribution of macrophytic

vegetation in the rivers of Britain. Journal of Ecology. 21: 58-91. Canfield, D. E. and M. V. Hoyer. 1988. The nutrient assimilation capacity of the Little Wekiva

River, Final Report. Department of Fisheries and Aquaculture. IFAS, University of Florida, Gainesville.

Childs, D.L. 1999. Spatial Evaluation of Factors Influencing Hydrilla on the Rainbow River.

M.S. Project. Center for Wetlands, University of Florida. Gainesville, FL. Dutoit, C. H. 1979. The carrying capacity of the Ichetucknee Springs and River. Masters Thesis,

University of Florida, Gainesville, Florida. 176 pp. FDEP. 1996. Ichetucknee trace baseline monitoring, 1996. Florida Department of Environmental

Protection, Chemistry Section, Central Laboratory. 15 pp. FDEP. 1997. Biological assessment of the Ichetucknee River Columbia County. Florida

Department of Environmental Protection, Biology Section. 15 pp. FDEP. 1998. The Role of Ecological Assessments in Environmental Management. Florida

Department of Environmental Protection, Bureau of Laboratories. FDEP. 2000. Ichetucknee Springs State Park approved unit management plan. Division of

Recreation and Parks, Tallahassee, FL. FDEP. 2002. EcoSummary of Ichetucknee Springs. Florida Department of Environmental

Protection, Bureau of Laboratories. Frazer, T.K., M.V. Hoyer, S.K. Notestein, J.A. Hale and D.E. Canfield, Jr. 2001. Physical,

Chemical and Vegetative Characteristics of Five Gulf Coast Rivers. Final Report. Southwest Florida Water Management District, Brooksville, Florida

Hill, W.R. and B.C. Harvey. 1990. Periphyton responses to higher trophic levels and light in a

shaded stream. Canadian Journal of Fisheries and Aquatic Sciences. 47: 2307-2314. Hutchinson, G. E. 1975. A treatise on limnology: Vol. III. Limnological botany. John Wiley &

Sons, Inc. New York. 660 pp. Hynes, H.B.N. 1970. The ecology of running waters. University of Toronto Press.


Jones, G.W., S.B.Upchurch, and K.M.Champion. 1996. Origin of Nitrate in Ground Water Discharging from Rainbow Springs, Marion County, Florida. Ambient Ground-Water Quality Monitoring Program, Southwest Florida Water Management District. Brooksville, FL.

Menzie, Charles A, 1980. The Chironomid (Insecta: Diptera) and Other Fauna of a

Myriophyllum picatum L. Plant Bed in the Lower Hudson River. Estuarine Research Federation

Moss, B. 1981. The effect of fertilization and fish on community structure and biomass of

aquatic macrophytes and epiphytic algae populations: An ecosystem experiment. Journal of Ecology. 64: 313-342.

Nilsson, C. 1987. Distribution of stream edge vegetation along a gradient of current velocity.

Journal of Ecology. 75 (2): 513-522. Notestein, S.K., T.K. Frazer, M.V. Hoyer and D.E. Canfield, Jr. 2003. Nutrient limitation of

periphyton in a spring-fed, coastal stream in Florida, USA. Journal of Aquatic Plant Management. 41: 57-60.

PBS&J. 2000. Rainbow Springs Aquatic Preserve 2000 Vegetation Mapping and Change

Analysis Report. Florida Department of Environmental Protection, Bureau of Coastal and Aquatic Managed Areas. Dunnellon, Forida.

Rosenau, J. C., G. L. Faulkner, C. W. Hendry, Jr., and R. W. Hull. 1977. Springs of Florida.

Florida Geological Survey - Geological Bulletin No. 31, revised. From http://www.flmnh.ufl.edu/springs_of_fl/aaj7320/content.html.

Thorp, A. G., R. C. Jones, D. P. Kelso. 1997. A comparison of water-column macroinvertebrate

in beds of differing submersed aquatic vegetation in the tidal freshwater Potomac River communities. Estuaries 20: 86-95.

Walsh, S. J. 2001. Freshwater macrofauna of Florida karst habitats. In: Eve L. Kuniasky, editor,

U.S. Geological Survey Karst Interest Group Proceedings, Water-Resources Investigations Report 01-4011, p. 78-88.

Walsh, S. J., and J. D. Williams. 2003. Inventory of fishes and mussels in springs and spring

effluents of north-central Florida state parks. USGS Final Report submitted to the Florida Park Service.

Warren, G.L., Hohlt, D.A., Cichra, C.E., VanGenechten, D. 2000. Fish and Aquatic Invertebrate

Communities of the Wekiva and Little Wekiva Rivers: A Baseline Evaluation in the Context of Florida’a Minimum Flows and Levels Statutes.

Water and Air Research, 1991. Diagnostic Studies of the Rainbow River. Southwest Florida

Water Management District. Brooksville, FL. Woodruff, A. 1993. Florida springs chemical classification and aquatic biological communities.

Masters Thesis, University of Florida, Gainesville, Florida. 117 pp.

Appendix A

Metadata for Ichetucknee and Manatee Springs SAV Maps

Appendix B

Ichetucknee Springs and River and Manatee Springs and Springs Run SAV Maps

2803 Fruitville Road, Suite 130Sarasota, Florida 34237Phone: 941.539.4036Fax: 941.951.1477

Submerged Aquatic Vegetationin Ichetucknee Springs and River

Spring 2003

G:\Projects\SRWMD_Spring_Veg\DraftGISDeliverables\MXD/figure_1.mxd

0 100 20050Feet

LegendSagittaria kurziana 0-25%

Sagittaria kurziana 25-50%


Vallisneria americana 0-25%



Chara sp. 0-25%

Chara sp. 25-50%

Chara sp. 50-100%

Zizania aquatica 0-25%



Hydrocotyle sp. 0-25%

Myriophyllum heterophyllum 50-100%

Ludwigia repens 50-100%

Chara-Myriophyllum Mix, 0-25%

Ludwigia-Hydrocotyle-Zizania Mix, 0-25%

Sagittaria-Zizania Mix, 0-25%

Sagittaria-Chara Mix, 0-25%


Vallisneria-Chara Mix, 0-25%

Vallisneria-Sagittaria Mix, 50-100%

Bare

Emergent

Other

Out

Headspring R

each

Rice M

arshR

each

Blue Hole Spring



Spring 2003G:\Projects\SRWMD_Spring_Veg\DraftGISDeliverables\MXD/figure_2.mxd

0 100 20050Feet







Chara sp. 0-25%

Chara sp. 25-50%

Chara sp. 50-100%







Bare

Emergent

Other

Out








Rice M

arsh Reach

Roaring Spring

Singing Spring




0 100 20050Feet







Chara sp. 0-25%

Chara sp. 25-50%

Chara sp. 50-100%







Bare

Emergent

Other

Out







Boiling Spring

Rice M

arsh R

each




0 100 20050Feet







Chara sp. 0-25%

Chara sp. 25-50%

Chara sp. 50-100%







Bare

Emergent

Other

Out








Mill Pond Spring

Floo

d P

lain R

each




0 100 20050Feet







Chara sp. 0-25%

Chara sp. 25-50%

Chara sp. 50-100%







Bare

Emergent

Other

Out








Flood Plain Reach




0 100 20050Feet







Chara sp. 0-25%

Chara sp. 25-50%

Chara sp. 50-100%







Bare

Emergent

Other

Out








Flood Plain Reach

Coffee Spring




0 100 20050Feet







Chara sp. 0-25%

Chara sp. 25-50%

Chara sp. 50-100%







Bare

Emergent

Other

Out








Flood Plain Reach




0 100 20050Feet







Chara sp. 0-25%

Chara sp. 25-50%

Chara sp. 50-100%







Bare

Emergent

Other

Out








Flood Plain Reach

U.S. 27 Bridge


Submerged Aquatic Vegetation in

Manatee Springs and Spring RunSpring 2003

G:\Projects\SRWMD_Spring_Veg\DraftGISDeliverables\MXD/report.mxd

0 100 20050Feet

LegendLudwigia repens 0-25%

Ludwigia rpens 25-50%

Potamogeton sp. 0-25%

Potamogeton sp. 25-50%




Bare

Suwannee R

iver

Headspring

Boat Ramp

Appendix C

Reprints of Dutoit (1979) Ichetucknee River SAV Maps and Cover Estimates

Appendix D

Data and Statistical Summaries from SAV Transect Sampling

Table D- 1. Sampling coordinates for the Ichetucknee River as sampled by Frazer et al. on April 30,

2003.

Transect Latitude Longitude

1 29.98310 -82.76071

2 29.98207 -82.76027

3 29.98079 -82.75928

4 29.97948 -82.75875

5 29.97825 -82.75927

6 29.97680 -82.75886

7 29.97541 -82.75895

8 29.97412 -82.75938

9 29.97228 -82.75999

10 29.97115 -82.75998

11 29.96992 -82.76015

12 29.96885 -82.76086

13 29.96770 -82.76151

14 29.96697 -82.76173

15 29.96511 -82.76192

16 29.96445 -82.76287

17 29.96383 -82.76447

18 29.96320 -82.76574

19 29.96188 -82.76811

20 29.96154 -82.76797

21 29.96069 -82.76931

22 29.96031 -82.77084

23 29.95987 -82.77306

24 29.95926 -82.77319

25 29.95922 -82.77435

26 29.95931 -82.77556

27 29.95913 -82.77627

28 29.95842 -82.77834

29 29.95774 -82.77968

30 29.95653 -82.78011

31 29.95537 -82.78222

Table D-2. Ichetucknee River mean values from data collected on April 30, 2003. N = 5 for depth, flow and canopy and N = 3 for each of the remaining

parameters. Asterisk width values were estimated from adjacent FDEP SAV monitoring transects.

TRANSECT WIDTH (m) DEPTH (m) FLOW (m/s) CANOPY

(%) TEMPERATURE

( C) SPECIFIC

CONDUCTIVITY (µS/cm)

DISSOLVED OXYGEN

(mg/L) pH

LIGHT ATTENUATION

(Kd/m) 1 17 0.98 0.11 78 21.9 320 4.3 7.46 0.49 2 21 0.98 0.18 20 21.8 320 4.5 7.46 . 3 15 0.98 0.22 90 21.8 320 4.7 7.57 . 4 16 1.18 0.26 86 21.9 312 3.7 7.27 . 5 26 1.00 0.23 0 21.9 311 4.1 7.45 0.58 6 45 0.82 0.20 0 22.1 309 5.0 7.49 0.58 7 54 1.12 0.23 10 22.2 314 4.9 7.50 0.71 8 50 1.00 0.24 2 22.3 315 5.2 7.59 . 9 . 1.00 0.15 5 22.5 323 5.2 7.67 .

10 . 1.04 0.17 0 22.6 322 6.2 7.61 . 11 . 1.03 0.13 0 23.0 321 6.7 7.75 . 12 . 1.44 0.13 0 23.2 322 7.4 7.70 . 13 . 1.20 0.14 33 23.3 321 7.6 7.79 . 14 . 1.16 0.15 0 23.5 321 7.8 7.84 . 15 . 1.48 0.17 30 23.6 329 7.4 7.61 . 16 22.7* 1.80 0.23 90 23.6 332 7.2 7.63 . 17 25.8* 1.82 0.21 80 23.6 335 7.1 7.67 . 18 . 1.32 0.23 0 23.6 334 7.2 7.72 . 19 . 1.94 0.15 36 23.6 334 7.2 7.75 . 20 . 1.80 0.18 61 23.6 334 7.2 7.77 . 21 19.7* 2.10 0.24 64 23.7 334 7.2 7.74 . 22 . 1.48 0.26 68 23.7 335 7.2 7.75 . 23 . 1.82 0.26 78 23.7 335 7.1 7.68 . 24 21.2* 1.80 0.14 100 23.7 336 7.1 7.74 . 25 21.2* 1.72 0.23 0 23.6 339 7.0 7.73 . 26 . 1.60 0.24 60 23.6 336 7.0 7.71 . 27 21.2* 2.06 0.27 50 23.7 336 7.1 7.70 . 28 . 1.76 0.18 58 23.6 336 6.9 7.70 . 29 . 2.28 0.22 50 23.6 334 6.9 7.70 . 30 . 1.84 0.22 40 23.5 340 6.6 7.71 . 31 19.7* 1.98 0.17 60 23.6 337 6.9 7.76 .

Sampled River Mean 1.47 0.20 40 23.1 327 6.4 7.65 0.59

Table D-3. Ichetucknee River mean transect values (N = 5) for SAV data collected on April 30, 2003.

TRANSECT SAV PERCENTCOVERAGE

SAV BIOMASS (kg/m2 wet weight )

PERIPHYTON (mg chl/g host wet wt.)

DOMINANT SAV SPECIES

1 47 Sagittaria kurziana 2 52 3.32 0.11 Sagittaria kurziana 3 44 Sagittaria kurziana 4 67 Sagittaria kurziana 5 61 3.26 0.11 Zizania aquatica 6 74 Zizania aquatica 7 51 Zizania aquatica 8 69 4.49 0.12 Sagittaria kurziana 9 51 Sagittaria kurziana 10 57 Zizania aquatica 11 44 2.43 0.27 Zizania aquatica 12 81 Sagittaria kurziana 13 72 Sagittaria kurziana 14 82 8.04 0.14 Sagittaria kurziana 15 77 Sagittaria kurziana 16 52 Sagittaria kurziana & Vallisneria americana 17 59 4.06 0.07 Sagittaria kurziana 18 90 Sagittaria kurziana & Vallisneria americana 19 54 Sagittaria kurziana 20 92 3.46 0.05 Chara sp. 21 88 Sagittaria kurziana 22 82 Sagittaria kurziana 23 82 5.73 0.08 Sagittaria kurziana 24 80 Chara & Fontinalis 25 100 Vallisneria americana 26 84 5.98 0.02 Sagittaria kurziana 27 100 Sagittaria kurziana 28 78 Chara & Sagittaria kurziana 29 70 6.48 0.05 Vallisneria americana 30 72 Sagittaria kurziana 31 82 Chara sp.

Sampled River Mean 71 4.66 0.11

TABLE D-4. Manatee Spring mean values from data collected on May 8, 2003. N = 3 for the transect mean values.

SPECIFIC DISSOLVED Light Attenuation (Kd/m)TRANSECT WIDTH (m) DEPTH (m) FLOW (m/s) TEMPERATURE ( C) CONDUCTIVITY (uS/cm) OXYGEN (mg/L) pH

1 . 22.4 498 2.0 6.97 0.432 26 1.87 0.11 22.4 488 2.0 7.03 1.033 . 1.87 0.10 22.5 482 1.8 7.10 1.954 . 1.87 0.08 22.7 419 1.7 7.06 2.435 . 2.20 0.09 22.9 410 1.9 7.05 2.80

Sampled Area Mean 1.95 0.09 22.6 453 1.8 7.05 1.92

SAV Biomass (kg/m2) By Depth (m)

0

2

4

6

8

10

12

14

SAV

Biom

ass

(kg/

m2)

.0 .5 1.0 1.5 2.0 2.5 3.0 3.5Depth (m)

Linear Fit Linear Fit SAV Biomass (kg/m2) = 1.36 + 2.34 Depth (m) Summary of Fit R Square 0.20R Square Adjusted 0.18Root Mean Square Error 3.34Mean of Response 4.75Observations 48 Analysis of Variance Source DF Sum of Squares Mean Square F RatioModel 1 129.07 129.07 11.58Error 46 512.72 11.15 Prob > FC. Total 47 641.80 0.001 Parameter Estimates Term Estimate Std Error t Ratio Prob>|t|Intercept 1.36 1.11 1.23 0.22Depth (m)

2.34 0.69 3.40 0.001

Figure D-1. Empirical relationship between stream depth and submersed aquatic

vegetation (SAV) biomass for the Ichetucknee River on May 30th 2003.

Mean SAV Percent Coverage By Mean Depth (m)

0

20

40

60

80

100

Mea

n SA

V Pe

rcen

t Cov

erag

e

1.0 1.5 2.0 2.5Mean Depth (m)

Linear Fit Linear Fit Mean SAV Percent Coverage = 41.526713 + 19.911519 Mean Depth (m) Summary of Fit R Square 0.26R Square Adjusted 0.24Root Mean Square Error 14.28Mean of Response 70.77Observations 31 Analysis of Variance Source DF Sum of Squares Mean Square F RatioModel 1 2117.84 2117.84 10.39Error 29 5910.01 203.79 Prob > FC. Total 30 8027.85 0.003 Parameter Estimates Term Estimate Std Error t Ratio Prob>|t|Intercept 41.53 9.43 4.41 0.0001Mean Depth (m)

19.92 6.18 3.22 0.003

Figure D-2. Empirical relationship between stream depth and submersed aquatic

vegetation (SAV) coverage for the Ichetucknee River on May 30th 2003.

SAV Biomass (kg/m2) By Flow (m/s)

0

2

4

6

8

10

12

14

SAV

Biom

ass

(kg/

m2)

0 .1 .2 .3 .4 .5 .6Flow (m/s)

Linear Fit Linear Fit SAV Biomass (kg/m2) = 2.19 + 12.06 Flow (m/s) Summary of Fit R Square 0.13R Square Adjusted 0.11Root Mean Square Error 3.50Mean of Response 4.66Observations 49 Analysis of Variance Source DF Sum of Squares Mean Square F RatioModel 1 84.73 84.73 6.92Error 47 575.56 12.25 Prob > FC. Total 48 660.29 0.01 Parameter Estimates Term Estimate Std Error t Ratio Prob>|t|Intercept 2.19 1.06 2.06 0.05Flow (m/s) 12.06 4.59 2.63 0.012

Figure D-3. Empirical relationship between stream flow and submersed aquatic

vegetation (SAV) biomass for the Ichetucknee River on May 30th 2003.

Mean SAV Percent Coverage By Mean Flow (m/s)

0

20

40

60

80

100

Mea

n SA

V Pe

rcen

t Cov

erag

e

.10 .15 .20 .25Mean Flow (m/s)

Linear Fit Linear Fit Mean SAV Percent Coverage = 49.059242 + 109.85366 Mean Flow (m/s) Summary of Fit R Square 0.096R Square Adjusted 0.065Root Mean Square Error 15.82Mean of Response 70.77Observations 31 Analysis of Variance Source DF Sum of Squares Mean Square F RatioModel 1 768.23 768.23 3.069Error 29 7259.62 250.33 Prob > FC. Total 30 8027.85 0.090 Parameter Estimates Term Estimate Std Error t Ratio Prob>|t| Intercept 49.059 12.714 3.86 0.0006 Mean Flow (m/s)

109.854 62.709 1.75 0.090

Figure D-4. Empirical relationship between stream flow and submersed aquatic

vegetation (SAV) coverage for the Ichetucknee River on May 30th 2003.

SAV Biomass (kg/m2) By Terrestrial Canopy Cover Percentage

0

2

4

6

8

10

12

14

SAV

Biom

ass

(kg/

m2)


Linear Fit Linear Fit SAV Biomass (kg/m2) = 5.10 - 0.012 Terrestrial Canopy Cover % Summary of Fit R Square 0.02R Square Adjusted -0.0002Root Mean Square Error 3.71Mean of Response 4.66Observations 49 Analysis of Variance Source DF Sum of Squares Mean Square F RatioModel 1 13.63 13.63 0.99Error 47 646.66 13.76 Prob > FC. Total 48 660.29 0.32 Parameter Estimates Term Estimate Std Error t Ratio Prob>|t| Intercept 5.10 0.69 7.35 <.0001 Terrestrial Canopy Cover %

-0.012 0.013 -1.00 0.32

Figure D-5. Empirical relationship between terrestrial canopy cover and submersed

aquatic vegetation (SAV) biomass for the Ichetucknee River on May 30th 2003.

SAV Coverage (per m) By Terrestrial Canopy Cover Percentage

0

20

40

60

80

100

SAV

Cov

erag

e (p

er m

)


Linear Fit Linear Fit SAV Coverage (per m) = 72.59 - 0.045 Terrestrial Canopy Cover % Summary of Fit R Square 0.003R Square Adjusted -0.003Root Mean Square Error 33.43Mean of Response 70.77Observations 155 Analysis of Variance Source DF Sum of Squares Mean Square F RatioModel 1 594.52 594.52 0.53Error 153 170937.12 1117.24 Prob > FC. Total 154 171531.64 0.47 Parameter Estimates Term Estimate Std Error t Ratio Prob>|t| Intercept 72.59 3.67 19.80 <.0001 Terrestrial Canopy Cover %

-0.045 0.062 -0.73 0.47

Figure D-6. Empirical relationship between terrestrial canopy cover and submersed

aquatic vegetation (SAV) coverage for the Ichetucknee River on May 30th 2003.

Mean Periphyton Abundance (mg chl/g host wet wt.) By Mean Flow (m/s)

0.00

0.05

0.10

0.15

0.20

0.25

0.30

Mea

n Pe

riphy

ton

Abun

danc

e (m

g ch

l/g h

ost w

et w

eigh

t)

.10 .15 .20 .25Mean Flow (m/s)

Linear Fit Linear Fit Mean Periphyton Abundance (mg chl/g host wet weight) = 0.3249848 - 1.0868469 Mean Flow (m/s) Summary of Fit R Square 0.46R Square Adjusted 0.39Root Mean Square Error 0.05Mean of Response 0.10Observations 10 Analysis of Variance Source DF Sum of Squares Mean Square F RatioModel 1 0.020 0.020 6.86Error 8 0.023 0.003 Prob > FC. Total 9 0.044 0.03 Parameter Estimates Term Estimate Std Error t Ratio Prob>|t| Intercept 0.325 0.087 3.76 0.006 Mean Flow (m/s)

-1.087 0.415 -2.62 0.03

Figure D-7. Empirical relationship between stream flow and periphyton abundance (mg

chl/g host plant wet weight) for the Ichetucknee River on May 30th 2003.

Mean Periphyton Abundance (mg chl/g host wet wt.) By Mean Terrestrial Canopy Cover

0.00

0.05

0.10

0.15

0.20

0.25

0.30M

ean

Perip

hyto

n Ab

unda

nce

(mg

chl/g

hos

t wet

wei

ght)

0 25 50 75 100Mean Canopy Cover (%) Linear Fit

Linear Fit Mean Periphyton Abundance (mg chl/g host wet weight) = 0.1511356 - 0.0013761 Mean Canopy Cover (%) Summary of Fit R Square 0.45R Square Adjusted 0.38Root Mean Square Error 0.06Mean of Response 0.10Observations 10 Analysis of Variance Source DF Sum of Squares Mean Square F RatioModel 1 0.020 0.020 6.477Error 8 0.024 0.003 Prob > FC. Total 9 0.043 0.034 Parameter Estimates Term Estimate Std Error t Ratio Prob>|t| Intercept 0.151 0.026 5.87 0.0004 Mean Canopy Cover (%)

-0.0013 0.0005 -2.54 0.034

Figure D-8. Empirical relationship between terrestrial canopy cover and periphyton

abundance (mg chl/g host plant wet weight) for the Ichetucknee River on May 30th 2003.

Appendix E

Field Notes from SAV-Associated Macroinvertebrate Sampling

Appendix F

SAV-Associated Macroinvertebrate Data for 31 Ichetucknee River Transects

Appendix G

SAV Occurrence Comparisons and Additional SAV-associated Macroinvertebrate Data

Errata: The methodology for enumerating SAV-associated macroinvertebrates was misstated in the original report. The correct methodology is stated below: “In the lab, all macroinvertebrates were subsequently rinsed from the SAV blades and transferred to glass jars and preserved in ethanol. Subsequently they were sorted, enumerated, and identified to the lowest possible taxon. However, due to the high abundance of macroinvertebrates, subsampling was conducted. A glass pan, (approx. 13” x 9” x 2”) was sectioned into identical squares labeled 1 through 40. Individuals were removed and enumerated from a randomly chosen square until 100 animals were counted. Once 100 animals were counted, the remainder of the square was enumerated. If 100 animals were not present within the area of one square, a second would be randomly selected etc., until a count of 100 was reached. A different subsampling method was used for oligochaetes. Due to large numbers of individuals, oligochaetes were subsampled by randomly selecting at least 6 individuals from each sample and identifying to genus and/or species. Three SAV blades (excluding Chara) were measured to calculate an average blade length for each sample. No B samples were collected at stations 13 or 18 due to a lack of SAV in the middle portion of the river. All statistical comparisons were conducted at the 95% confidence level (p<0.05).“

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