The Concentration of Nitrite and its Role in the Dissolved Oxygen Content in Ebey Slough

BIS 499 Independent Research Project

Dr. Robert Turner

Tajinder Singh6/8/2016

AbstractAs a part of a research team with classmates Chris Themelis and Kabrina C. Orchard at the University of Washington Bothell, we collectively gathered water quality data from within and near the Qwuloolt estuary restoration site in Marysville, WA. After a levee breach in August 2015 that allowed tidal inundation from Ebey slough to a former farmland in hopes to facilitate natural hydrologic processes that occur when fresh and saline water mix and eventually form an estuarine wetland that will serve as a site for salmon rearing. We mainly measured nitrate levels at the site using the SUNA senor and tracked any fluctuations in nitrate levels because of the breach. Although it is too early to tell at this stage of the restoration project to conclude anything substantial, there was a slight upward trend of nitrate levels in and around the breach site. This may indicate that nutrients from the soil in the former farmland are being distributed into Ebey slough. That is not a matter for concern, but it if nitrate levels continue to rise, Ebey slough might become polluted with excess nitrate and/or phosphorous coming from both surface runoff and the soil, which may cause eutrophication and lower the dissolved oxygen content of the water to a point it may no longer sustain aquatic wildlife.

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Table of Contents

Introduction: pg. 2Site Characteristics: pg. 4Methods: pg. 9Results: pg. 10Discussion: pg. 12Conclusion: pg. 14References: pg. 16

FiguresFig. 1: pg. 5Fig. 2: pg. 6Fig. 3: pg. 7Fig. 4: pg. 7Fig. 5: pg. 8Fig. 6: pg. 10Fig. 7: pg. 11Fig. 8: pg. 11Fig 9: pg. 12

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Introduction:

The main goal of the Qwuloolt Estuary Restoration Project is to restore the natural processes of rivers

and tides by breaching a levee dividing Ebey slough from a 400-acre former marshland and farming area

knows as the Qwuloolt floodplain. A Estuarine residence like the Qwuloolt floodplain site when restored

would provide juvenile salmon with extensive forage opportunities, refuge from predation, and time for

physiological adaptation to increasing salinities during the transition from fresh to salt water all of which

is essential for survival and growth of keystone PNW salmon (Healey 1982).

This restoration project involved cooperation from the following stakeholders and representatives:

Tulalip Tribes of Washington.

National Oceanic and Atmospheric Administration (NOAA).

U.S. Fish and Wildlife Service (USFWS).

Washington Department of Ecology (WDOE).

US Army Corps of Engineers.

Natural Resource Conservation Service (NRCS).

City of Marysville.

Salmon are an integral part of the economy and ecosystem of the PNW since they are a keystone

species and over 137 different species depend on salmon directly and indirectly (WDOE 2002). The long-

term goal of the Qwuloolt restoration is to transform the former farmland into a self-sustaining,

vegetated estuarine wetland that will maximize the natural ecological potential of the site and facilitate

the natural hydrologic processes, which will support and deposit sediment and seeds required for

succession of native vegetation and plant cover, all of which will facilitate in providing optimal rearing

habitat for salmon going upstream through Ebey slough. The floodplain is currently home to various

invasive species such as reed canary grass, thistle, and Himalayan blackberry. One of the goals is to

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promote dieback of these types of invasive vegetation at the site in order to provide native

reintroduction and plant cover.

The official objectives of the restoration include according to the Qwuloolt website is as follows:

To maximize cover, forage, migratory pathways, and other habitat functions for salmon.

Facilitate native vegetation re-establishment through restoration planting.

Promote dieback of invasive vegetation cover through brackish water re-introduction.

Restore the public and Tulalip people’s connection to the Qwuloolt marsh.

Protect infrastructure by constructing a setback levee.

Enhance water quality through construction of stormwater treatment cells.

Recover the natural stream and floodplain forms through filling of drainage ditches and re-

contouring of mainstream and distributary networks.

Increase salmon populations and channel-floodplain habitat functions through placement of

large wood within creeks.

According to the Snohomish Basin Salmon Conservation Plan (Snohomish Basin Salmon Recovery Forum

2005), the quality and quantity of rearing habitat in the nearshore estuary and mainstream rivers is the

primary factor limiting Chinook and bull trout salmon. The Qwuloolt restoration project is expected to

benefit these federally threatened species, as well as other fish and wildlife by increasing the extent and

connectivity of estuarine wetlands in the Snohomish area.

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Site Characteristics

The Qwuloolt floodplain is 354 acres in size, the old levee was built about 110 years ago to prevent tide

and salt water from coming into the then farmland. The US Army Corps of Engineers breached the levee

and dug out about 260 feet gap to allow tide to come in from Ebey slough in hopes to create a mix of

salt and freshwater to promote optimal rearing habitat for salmon and a diverse wetland with various

native species.

Our main sampling sites for nitrate were as follows:

QC1 (Quilceda Creek Fish Catch Site)

CR6 (Directly in front of the Marysville sewage treatment facility located near the Qwuloolt

floodplain)

CR5 (At the mouth of the "Marysville Restoration Site: Jones Creek")

CR4 (Below the breach, at the mouth of the Ebey Fyke; NOAA's lower fish catch site)

CR3 (Located directly in front of the levee breach site)

CR2 (About 30m above the breach)

CR1 (Point Furthest above breach. Just past the Heron Fyke NOAA fish catch site)

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Figure 1. Depicting Qwuloolt restoration site aerial view (2009)

Source: (Monitoring Plan for the Qwuloolt Restoration Project. Rice, Casimir 2011)

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Figure 2. Blue indicates minor excavation, red is major excavations and the yellow is location of new setback

levee. (Image source: http://www.qwuloolt.org/AboutUs)

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Figure 3. Picture of the breach site the day before from a webcam installed at the site.

Figure 4. At the site of the breach on August 28 2015, the US Army Corps of Engineers excavating.

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(Image source: http://www.heraldnet.com/article/20150828/NEWS01/150829126)

Figure 5. Photo taken on August 28 2015 after the levee breach.

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Methods

We collected data from the Qwuloolt restoration site on a weekly basis every Tuesday during low tide

from 10/21/2015 until 11/28/2015. We sampled mainly at the points mentioned earlier in the site

characteristics section using our equipment. Our methods included going to the site every Tuesday

during low tide to ensure we were able to get close enough to Ebey Slough and the breach site safely

since we were on foot and did not have access to a boat. We recorded the data collected from the YSI 85

and SUNA sensor.

The YSI gave us important water quality parameters like the temperature, salinity, dissolved oxygen

content, and conductivity levels in the water. We wanted to see the connection between dissolved

oxygen content and nitrate since high nitrate concentrations contribute to eutrophication, which is

when excess growth of vegetation in the water such as algae can occur, which in turn lowers the

dissolved oxygen content, which fish and other aquatic wildlife depend on. The SUNA (Submersible

Ultraviolet Nitrate Analyzer) was used to take both fresh and salt-water nitrate readings, the SUNA was

developed to measure nitrogen-based nutrients concentrations in ocean, estuarine and high turbidity

freshwater environments. To take nitrate readings we would submerse the SUNA sensor in the water for

at 15-25 seconds to collect the readings via the attached tablet and then save it and export it to a

Microsoft Excel spreadsheet for graphical analysis.

We also conducted brief site surveys of the vegetation, and writing down any changes to the site if

applicable, for example new algae growth, tide level, wind, weather, etc.

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Results:

0 2 4 6 8 10 120

2

4

6

8

10

12

Nitrate (mg/L) Fresh Water Deployment: Nitrate concentrations over 2 months Fall 2015

Day of data collection

mg/

L ni

trat

e

Figure 6. Nitrate levels from fall 2015 were consistent but showed a slight upward trend, the graph in this figure combined nitrate levels within from Ebey slough. The sites are CR1, CR2, CR3, CR4, CR5, and CR6.

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10/27/2015 11/24/2015 11/28/20150

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.472472928 0.463765527

0.607372479

Average Nitrate Levels within Ebey Slough

Date of Sampling

Nitr

ate

Conc

entr

ation

(mg/

L)

Figure 7. This figure depicts the concentrations of nitrate in (mg/L) over time similar to figure 6, this representation shows the concentrations gradually going up with them being highest on our last day of data collection 11/28/2015 with 0.6073 mg/L nitrate.

QC1 CR6 CR5 CR4 CR3 CR2 CR10.59

0.595

0.6

0.605

0.61

0.615

0.60091818

0.60577857

0.60287143

0.61121667

0.61375556

0.60207143

0.6081

Nitrate Fall Averages 2015 @ Main Sampling Sites:

Sampling Site

Nitr

ate

Conc

entr

ation

(mg/

L)

Figure 8. This figure shows sites sampled and the average nitrate concentrations in (mg/L) after the breach samples were taken from October 2015 to November 2015. The main sample sites are within Ebey slough with the exception of QC1, which is located at the boat launch site away from the slough. Source (Themelis, 2016).

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QC1 CR6 CR5 CR4 CR3.5 CR3 CR2 CR10.440.460.48

0.50.520.540.560.58

0.60.62

0.596555

0.53852560.523789181818182 0.5117777777777

78

0.56256

0.500916666666667

0.5116950.499182625

Nitrate Averages Summer 2015 (including post breach point CR3.5)

Site Location

Nitr

ate

Conc

entr

ation

(mg/

L)

Figure 9. This graph shows the nitrate averages taken after the breach in the summer 2015. As you compare these numbers to the ones in Figure 8, you will see there is an increase in nitrate concentrations for each of the sites from the months of October to November. This proves that nitrate concentrations will increase overtime because of allowing tidal inundation in the Qwuloolt site from Ebey slough. Source (Themelis, 2016).

Discussion

Because salmon gain 95% of their body mass in the ocean then return to freshwater to spawn and die,

the marine-derived nutrients they transport can be substantial for nutrient-poor freshwater streams and

lakes (Naiman et al. 2002, Schindler et al. 2003, Janetski et al. 2009). In this case, the salmon that will be

traveling through the Qwuloolt restoration site will be bringing with them essential nutrients that may

aid in creating an optimal spawning habitat within the estuarine wetland.

The nitrate concentration averages for the Qwuloolt estuary restoration site were all below 1.0 mg/L

and ranged from 0.45-0.61 mg/L. These nitrate concentrations are not a toxicity concern. Nitrate

concentrations of 5-10mg/l are mildly toxic to eggs and fry of cutthroat and rainbow trout species.

Chinook salmon are affected at 20 mg/L nitrate levels, and Coho salmon are sufficiently resistant

(Kincheloe et. al. 1979). As a general guideline, nitrate at levels around 10 mg/L in surface water limit

salmon rearing and spawning.

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Nitrate and phosphorus are extremely important parameters in water quality because increased nitrate

concentrations contribute to excess vegetation growth and algal blooms in waters. According to the

EPA, nutrient pollution is one of America’s most widespread and challenging environmental problems.

Eutrophication may occur at the qwuloolt site and Ebey slough if excess nitrogen and phosphorus from

sources such as fertilizers and surface runoff gets into the surface waters and that will provide favorable

habitat for plant growth such as algae and duckweed. Algal blooms at the surface of water bodies

prevent sunlight from reaching deeper depths, as a result, the plants that reside there die, and dissolved

oxygen is depleted by absence of respiration. Decomposers then break down the dead plants, which

further depletes oxygen levels. Eventually if pollutants like nitrogen and phosphorous continue to enter

the water body hypoxia will occur. Hypoxia occurs when the dissolved oxygen content in the water

depletes to a point that it no longer can support aquatic life at all. Since the levee breach was separating

Ebey slough from a former farmland, the soil on the land itself could be a source of nitrate from

fertilizers used in the past, and from animal and plant residue that may have deposited nitrogen into the

soil.

We believe that nitrate concentrations will rise over time, as the Qwuloolt site is flooded overtime from

the tide coming in from Ebey slough. The tide will serve as a medium to remove and transport nutrients

from the restoration site and distribute in Ebey slough. From comparing the data in figure 9 and figure 8

it is clear that nitrate levels in and around the breach site went up over time since the breach occurred,

we need to continue to monitor these changes in nitrate levels to ensure that the restoration project

will be successful.

Water temperature is another factor when determining survival and rearing habitat for salmon in

estuaries. Adult salmon have experienced poor survival when exposed to water temperatures greater

than 60°F (15.5°C), it is important to note that adults held in water temperatures greater than 15.5°C

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and less than 3.3°C have less viable eggs than those held at 3.3°C-15.5°C which is the optimal

temperature (Marine, K. R., & Cech, J. J. 2004). In our results, the temperature recording did not exceed

10°C and averaged around 5.0°C, which is within the given range of survival or optimal rearing habitat,

given that temperature is not a parameter of major concern at this point we did not graphically

represent it as we did the nitrate levels.

Conclusion

This project is a continuation of the one that began in spring 2015 prior to the levee breach to set a

baseline of data that will be used in the future for hydrology students at UWB. We gathered data to get

a better understanding between the connection of nitrate and dissolved oxygen in Ebey slough after the

breach of a levee that was separating the slough from the former farmland for over 100 years and thus,

allowing tidal inundation. The ultimate goal is to allow fresh and salt water to mix and eventually create

an estuarine wetland with abundant native species that will provide plant cover and forage

opportunities for salmon traveling upstream and create a favorable environment for spawning. We do

not have strong conclusive data from the Qwuloolt estuary restoration site, given the short since the

breach, it is difficult to assess any changes to the water quality that may have a detrimental impact. In

figures 6 and 7, you will see that the average nitrate concentrations showed a slight upward trend, and

the highest recorded concentration on nitrate being at CR3 (directly in front on breach located in Ebey

slough) and CR4 (below the breach site), which are in close proximity to one another. It is important to

note in figure 9 and 8, the average nitrate levels gradually went up overtime since the breach in summer

2015. This positive trend confirms our hypothesis that nitrate storages from the soil in the farmland will

migrate slowly into Ebey slough. The increased concentration of nutrients because of tidal inundation

will in theory promote an optimal estuarine habitat for PNW salmon and provide a favorable

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environment to grow native vegetation. We must be patient before expecting salmon population to

make a dramatic return since this project is long-term. We can continue to gather data and create

graphical representations of the nitrate levels, dissolved oxygen content, temperature, salinity, etc., and

create a database of those parameters to refer to. If we continue to gather data from and monitor the

Qwuloolt restoration site in the next coming months and years continuously, only then we may come

across some more reliable data in order to predict the future and success of the Qwuloolt restoration

project.

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