ecological processes€¦ · overhanging vegetation and root balls in the bank create structured...

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Data Compilation and Estuary Processes Study – Darkum Creek, Woolgoolga Lake and Willis Creek 1616892

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Ecological Processes 7 7 7

7.1 Estuarine Habitat There are a variety of habitats present in most estuaries. The most common estuarine habitats are vegetative habitats such as mangroves, seagrass and saltmarsh and non-vegetative habitats such as sand, mud and gravel bars, rocky reefs and boulder fields. Representative areas of most of the above habitat types can be found in Darkum Creek, Woolgoolga Lake and/or Willis Creek. In general, the availability of aquatic habitat types is dependent upon geomorphic and hydrological factors. For example, mangroves and seagrass habitats have specific substrate and water quality requirements. As a result of this, ‘zones’ of habitat availability commonly concur with geomorphic process zones and zones of specific tidal and/or freshwater influence. 7.1.1 Field survey of aquatic habitats The following sections describe the results of aquatic habitat surveys undertaken in January and April 2011. Aquatic habitats were described in detail for a series of cross channel transects located in representative positions throughout the three estuaries. The aspects that were considered were: � benthic material; � aquatic vegetation in the channel; � presence of snags; � aquatic and semi aquatic vegetation along the banks; � overhanging vegetation; � channel width; and � GPS position. Detailed results from each transect are reproduced in Appendix I. The position of the transects are mapped in Illustration 7.1 to Illustration 7.3. The resulting information was used to develop the following overall descriptive pictures of the available aquatic habitats across the three estuaries and to inform mangrove and saltmarsh vegetation mapping from aerial photographs (see Section 7.1.2). Mangrove and saltmarsh vegetation maps produced for this study can be found in Illustration 7.5 to Illustration 7.7. 7.1.2 Darkum Creek For the purposes of a general habitat description Darkum Creek estuary can be broken up into three broad conceptual zones. A map of these zones is provided in Illustration 7.4. The zones will be referred to as the entrance zone, the central channel and the upper estuary. The entrance zone is a short section of the creek that offers little structured aquatic habitat. The benthic material is sand, some of which is intertidal for short periods after entrance breakouts when the creek is affected by the tide. The position of the channel and banks is dynamic in this part of the creek and as a result vegetation is largely absent from these features for most of the time. The entrance zone corresponds closely with the Marine Tidal Delta geomorphic zone in Illustration 5.1.

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SAFETY BEACH

Darkum Creek

Data Compilation and Estuary Processes Study1616478

Illustration

Locations of Sample Sites Used During Ecological Surveys Undertaken as part of the Estuary Processes Study - Darkum Creek

North 7.1

Drawn by: RE Checked by: MVE Reviewed by: TIM Date: June 2011Source of base data: Coffs Harbour City CouncilInformation shown is for illustrative purposes only

L E G E N D Darkum Creek Estuary catchment

!( Invertebrate Core!( Seine Net!( Fish Trap!( Water Quality

Transect

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WOOLGOOLGA

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Locations of Sample Sites Used During Ecological Surveys Undertaken as part of the Estuary Processes Study - Woolgoolga Lake

North 7.2


L E G E N D Woolgoolga Lake Estuary catchmentTransect


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Locations of Sample Sites Used During Ecological Surveys Undertaken as part of the Estuary Processes Study - Willis Creek

North 7.3


L E G E N D Willis Creek Estuary catchmentTransect


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Woolgoolga Lake

Darkum Creek

Willis Creek


Illustration

Conceptual Zones Used for the Description of Aquatic Habitats in Darkum Creek, Woologoolga Lake and Willis Creek

North 7.4


L E G E N D Estuary catchment boundariesCentral ChannelEntranceLake asinLo er Creek

pper Creekpper Estuary

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The central channel of Darkum Creek is a long section of relatively homogenous aquatic habitat availability. The following habitat features distinguish the central channel: � the benthic material is a patchy mixture of sand, mud and gravel. Most of the benthos is below the typical

low tide level, meaning intertidal habitats are sparse; � mixed species of mangroves were present at most of the mapped transects along the central channel.

Three species of mangrove are present. The river mangrove (Aegiceras corniculatum) is the dominant species, followed by the grey mangrove (Avicennia marina). The milky mangrove (Excoecaria agallocha) is present as scattered individuals. Mangroves do not grow in an unbroken band along the creek bank but are variously present as wide bands and as scattered individuals for most of the length of the estuarine region. A map of mangrove distribution was undertaken as part of this study and is displayed in Illustration 7.5;

� there are two small patches saltmarsh habitat present in the central channel, dominated by marine rush (Juncus krausii) and salt couch (Cynidolon dactylon) – refer to Illustration 7.5;

� there were no submerged aquatic macrophytes, such as seagrass or algae, actively growing at the time of the survey. During the CCA survey (DPI 2006) a significant patch of seagrass (Halophila sp.) was mapped at the entrance. This particular species is known to be dynamic in its occurrence and distribution. It is quite possible that when conditions are optimal that it will reoccur in a similar part of the creek;

� snags are a key habitat type in Darkum Creek, particularly along the central channel. Fallen trees along the bank and logs in the middle of the channel are common occurrences. Along with mangrove pneumatophores and gravel beds, snags represent most of the in-stream structural habitat for fish and invertebrates in Darkum Creek; and

� the other features of the central channel that provide habitat value are reeds and rushes (mostly common reed (Phragmites australis) and river club rush (Schoenoplectus validus)) and the root balls and overhanging branches of riparian vegetation.

The upper estuary zone of Darkum Creek is limited to the short section where the channel narrows dramatically. The key differences in this zone are the lack of mangroves, narrower channel and steeper banks. Riparian vegetation is dominated by rushes and reeds amongst swamp oak (Casuarina glauca) and paperbark (Melaleuca quinquinerva) forest. Overhanging vegetation and root balls in the bank create structured habitat. The benthic material in this upper part of the creek is a patchy mixture of gravel and mud. 7.1.3 Woolgoolga Creek For the purposes of a general habitat description Woolgoolga Lake can be broken up into four conceptual zones. These will be referred to as the entrance zone, the lake basin, the lower creek and the upper creek. These zones are mapped in Illustration 7.4. The entrance habitat zone is short, limited to the length of the creek between the entrance and just upstream of the Caravan Park. The entrance habitat zone is characterised by the following features: � a marine sand benthos, devoid of aquatic vegetation with small gravel bars; � wide but shifting intertidal sand bars; � intertidal rocky shores and rock revetment that depend upon sand distribution. These provide substrate for

oysters, tube worms and barnacles; � limited riparian vegetation for the most part, with areas of swamp oak and scattered individual mangroves;

and � patchy distribution of gravel bars. The lake basin habitat zone is the largest habitat zone of the Woolgoolga Lake estuary. The lake basin zone is a relatively large body of open water characterised by the following features: � a benthos made up of mud and some sand; � large areas of intertidal mud and sand bars; � scattered large snags;


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� large intertidal gravel bars, scattered throughout the zone supporting oysters and other shelled molluscs; � an area of subtidal rocky reef supporting a large colony of saddle tree oyster (Isognomon ephippium); � a narrow band of mangroves landward of intertidal mud flats, made up of the grey mangrove (Avicennia

marina) and the river mangrove (Aegiceras corniculatum). Mangroves are found around most of the margins of the lake basin but not all (refer to Illustration 7.6);

� mixed riparian vegetation dominated by marine rush, river club rush, swamp oak and paperbark; � a lack of subtidal aquatic macrophytes such as seagrass or seaweeds; and � small patches of salt marsh made up mostly of salt couch and scattered marine rush (refer to

Illustration 7.6).

Plate 7.1 Saltmarsh Area in Woolgoolga Lake Estuary The lower creek habitats in Woolgoolga Lake are the areas immediately upstream of the confluences of Woolgoolga Creek and Poundyard Creek with the lake basin. The lower creek zone is characterised by the following habitat features; � a benthos made up primarily of gravel and shell grit; � significant, dense colonies of mangroves up to 10m deep; � steep, high banks in areas, formed by bed rock and supporting a diverse riparian vegetation. Riparian

vegetation is dominated by swamp oak but also includes paperbark, eucalypt species, sedges, camphor laurel;

� root balls in the steep banks forming overhangs and providing structural habitat; � small areas of intertidal mud being colonised by mangroves; and � overhanging vegetation and lots of large snags. The upper creek habitats in Woolgoolga Lake are differentiated primarily by a lack of mangroves and increasingly steep and high banks. The banks typically have root balls which form overhangs and provide structural habitat. Large snags are a common feature. The riparian vegetation forms a canopy over the creek for most of this zone. It is made up mostly of swamp oak but also includes angophoras, figs, umbrella trees, camphor laurels, climbing vines and sedges.


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7.1.4 Willis Creek For the purposes of a general habitat description Willis Creek, like Darkum Creek, can be broken up into three conceptual zones. These will be referred to as the entrance zone, the central channel zone and the upper estuary zone. These zones are mapped in Illustration 7.4. The entrance zone of Willis Creek is a short section that offers little structural or vegetative aquatic habitat. The benthic material is sand, some of which is intertidal for short periods after entrance breakouts when the creek is affected by the tide. The position of the channel and banks is dynamic in this part of the creek and as a result vegetation is largely absent from these features for most of the time. The central channel habitat zone of Willis Creek is the longest of the three conceptual zones. The central channel is relatively homogenous for its length, and is made up of the following habitat features: � mangroves are present over the length of this zone, either in wide bands, small patches or as individuals.

Only grey mangroves were encountered during this survey. Mangroves appear to be actively recruiting to Willis Creek (refer to Illustration 7.7);

� rushes and reeds are an important structural vegetative habitat in the central channel of Willis Creek. There are large colonies of common reed, river club rush and dirty dora (Cyperus difformis);

� there are significant areas of salt marsh along the fringes of the central channel (refer to Illustration 7.7). The dominant saltmarsh species are marine rush and salt couch;

� there are a few large snags throughout this zone but not many; � the bed of the creek is generally deep mud, with some sand in the most downstream reach; and � there are no significant areas of intertidal soft sediments nor significant submerged aquatic vegetation such

as seagrass or seaweed. The upper estuary habitat zone is limited to a short section of creek where the channel narrows. This upper section flows through a low lying swamp forest (SEPP 14 protected wetland), variously dominated by swamp oak and paperbark. The banks of the creek are steep and dominated by these trees and occasional rushes (Baumea sp.) and sawsedge (Gahnia sp.). The benthos in this zone is muddy, with lots of decomposing detritus input from the riparian zone. Key structural habitats are small snags, root balls and holes in the banks and overhanging riparian vegetation. Instream vegetative habitats are completely lacking from this zone. 7.1.5 Estuarine Habitat Mapping The most recent maps of mangrove, seagrass and saltmarsh habitats were prepared in 2006 (Williams et al. 2006) from aerial photography collected in 2004. In order to assess the changes in the extent and distribution of these habitats over time, they were mapped again for this study. The mapping was undertaken using ADS40 aerial photography captured in Autumn 2009. This was the highest quality, most recent orthorectified aerial photography freely available to the study. The mapping was informed by data collected in the field as part of the habitat mapping described in Section 7.1.1. The locations of colonies recorded in the field were used to identify colonies on aerial photographs. The visible extent of colonies were then traced in a GIS platform with the scale of the aerial photo set to 1500:1. Scattered individual trees and plants were not mapped. No seagrasses were observed during the field surveys undertaken for this study. As a result, seagrasses were not mapped from the ADS40 aerial photos used. The extent of mangroves and seagrasses mapped are displayed in Illustration 7.5 to Illustration 7.7. The results of estuarine habitat mapping undertaken for this study have been compared with the results of previous studies in an attempt to assess trends in habitat distribution and abundance. Table 7.1 shows the differences in the extent of estuarine habitats over time. There were differences in the methods applied by the three different studies with respect to the resolution of imagery used and the way information gathered in the field was


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incorporated into maps. Clearly, some of the changes detected are a result of these methodological differences. Despite this, the following conclusions can be drawn: � the area of mangroves in each of the three estuaries has increased since 1981. Newly recruited mangroves

can be seen around the margins of existing mangrove colonies and in other suitable habitat throughout each of the three estuaries. Newly accreted sediments are often quickly colonised by mangroves, leading to an increase in their extent. In addition, removal of the constant freshwater inflow from the STP previously discharging into Willis Creek may have improved the conditions for grey mangrove recruitment through changes to the salinity regime;

� seagrasses in Darkum Creek are dynamic and probably appear and senesce naturally over time scales larger than the time frame for an estuary management plan. None of the three estuaries provide good conditions for the maintenance of seagrass beds. This is common among ICOLLS with irregular and uncommon entrance openings; and

� changes in the area of saltmarsh mapped at different times are difficult to interpret. There would appear to be some difference between the interpretation of what constitutes saltmarsh between the mapping of saltmarsh habitats in Willis Creek undertaken for this study and the undertaken in 1994 (data provided by CHCC). The increase in the area of saltmarsh in Woolgoolga Lake is due to the inclusion of a large area of regularly inundated salt couch adjacent to the residential area in the south western corner of the central lake basin. This particular area of saltmarsh is mowed, thus limiting the diversity of species that can occur there.

Table 7.1 Abundance of vegetated aquatic habitats as mapped for various studies.

Habitat System 1981 Area (ha)

2004 Area (ha)

2009 Area (ha)

Mangrove Darkum Creek 0.1 0.97 1.43 Woolgoolga Lake 0.2 0.63 1.12 Willis Creek No data No data 0.91 Saltmarsh Darkum Creek <0.1 0.04 0.06 Woolgoolga Lake <0.1 0.02 0.14 Willis Creek No data 6.39* 1.62 Seagrass Darkum Creek 0 1.30 0** Woolgoolga Lake 0 0 0** Willis Creek No data No data 0**

Note: * - mapped in 1994, methods unknown, data provided by CHCC. ** - seagrass areas reported for 2011, not 2009.

SAFETY BEACH

Darkum Creek


Illustration

Estuarine Habitat Mapping Undertaken as part of this Study Compared with Williams et al (2006) - Darkum Creek

North 7.5

Drawn by: RE Checked by: MVE Reviewed by: TIM Date: July 2011Source of base data: Coffs Harbour City CouncilInformation shown is for illustrative purposes only

L E G E N D an rove Comprehensive Coastal nalysis 004an rove uatic Science and ana ement 00

Sea rass Comprehensive Coastal nalysis 004Saltmarsh Comprehensive Coastal nalysis 004Saltmarsh uatic Science and ana ement 00

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Estuarine Habitat Mapping Undertaken as part of this Study Compared with Williams et al (2006) - Woolgoolga Lake

North 7.6

Drawn by: RE Checked by: MVE Reviewed by: TIM Date: July 2011Source of base data: Coffs Harbour City CouncilInformation shown is for illustrative purposes only

L E G E N D Saltmarsh (Aquatic Science and Management - 2009)Mangrove (Aquatic Science and Management - 2009)Mangrove (Comprehensive Coastal Analysis - 2004)Saltmarsh (Comprehensive Coastal Analysis - 2004)

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Lake B

each

Willis Creek


Illustration

Estuarine Habitat Mapping Undertaken as part of this Study Compared with Williams et al (2006) - Willis Creek

North 7.7


L E G E N D Saltmarsh (Aquatic Science and Management - 2009)Saltmarsh (Coffs Harbour City Council - 1994)Mangrove (Aquatic Science and Management - 2009)

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7.2 Aquatic Fauna The estuarine habitats descried in the previous section are important to a wide variety of fauna. 7.2.1 Macroinvertebrate Sampling Macroinvertebrate fauna were sampled using a 100 mm diameter core sampler entered to 100 mm depth. As the sampling was intended to survey fauna, single samples were collected from each site. Three sites were chosen from each estuary. The locations of sample sites are displayed in Illustration 7.1 to Illustration 7.3. A sample from the upstream site in Woolgoolga Creek (BM3) was not obtained due to the nature of the creek bed there, which is hard packed shale. Samples were field rinsed over a 0.5 mm sieve and fixed in 10% formalin solution with Bengal rose dye. Samples were re-rinsed over a 0.5 mm sieve in the laboratory and then preserved in ethanol. Sorting and identification were undertaken using a binocular microscope. Fauna were identified to family level where possible. The sample from Darkum Creek BM2 was elutriated to remove animals and sediment from the coarse gravel in the sample. The complete results are displayed in Table 7.2. In general the numbers and diversity of benthic organisms were low. Two samples from Willis Creek and one sample from Darkum Creek contained no animals. Across the three estuaries the greatest diversity of taxa were found in the samples collected from the central region. No benthic fauna were found in any of the samples from the upper sections of the estuaries, though no sample could be collected from the upper section of Woolgoolga Lake due to the coarse gravelly nature of the benthos there. These trends are displayed visually in Plate 7.2. The samples from Darkum Creek were dominated by Polychaete worms. The samples from Woolgoolga Lake were dominated by amphipods. Table 7.2 Results of benthic macroinvertebrate sampling from the estuaries.

Class/Order Taxa Common Name Darkum Creek Woolgoolga Lake Willis Creek BM1 BM2 BM3 BM1 BM2 BM3 BM1 BM2 BM3

Polychaeata Capitellidae Polychaete worm 3 2 - - - N/A - 7 - Nereididae Polychaete worm 1 1 - - - N/A - - - Opheliidae Polychaete worm - 1 - N/A Orbiniidae Polychaete worm 1 - - - - N/A - - - Spionidae Polychaete worm - 1 - - 6 N/A - 1 - Amphipoda Melitidae Amphipod - - - - 5 N/A - 3 - Phoxocephalidae Amphipod - - - 1 3 N/A - - - Urothoidae Amphipod - - - 2 - N/A - - - Isopoda Cyclopoida Isopod - - - - 1 N/A - - - Phratoicidea Isopod - 1 - - - N/A - - - Gastropoda Hydrobiidae Snail - - - - 2 N/A - - - Bivalvia UnIdd Bivalve Bivalve - - - - 11 N/A - - - Diptera Chironominae Caddis fly larvae 4 - - - - N/A - - - Orthicladiinae Caddis fly larvae - 1 - - - N/A - - - Total Individuals 9 7 0 3 28 N/A 0 11 0 Total Taxa 4 6 0 2 6 N/A 0 3 0

In a previous study of the invertebrate fauna of Willis Creek only two taxa were encountered, despite an intensive sampling regime (Jellife 1997). In the present study there were three, two of which had not been encountered previously (from families Spionidae and Melitidae). This is an indication of the changes in the hydrology of Willis Creek since the cessation of effluent discharge. It is also an indication that the impacts of effluent discharge are beginning to be mitigated by natural processes.


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Plate 7.2 Number of benthic macroinvertebrate taxa in sediment samples from different zones

7.2.2 Fish sampling A survey of fish species was undertaken using a seine net and bait traps on 22 May 2011. Fish were collected under a NSW I&I section 37 permit for scientific collection ( #P10/0070-1.0). Incidental sightings of bird species and uncaptured fish fauna were noted throughout field surveys. Fish sampling locations are mapped in Illustration 7.1. The use of the seine net was limited to areas where it could be deployed and collected efficiently. Fish habitat such as snags and mangrove pneumatophores cannot be sampled with a seine net. Due to the lack of submerged aquatic vegetation this meant that the seine net was used to sample only bare sand, mud and gravel beds. A seine net was deployed at 2 sites in Darkum Creek and Woolgoolga Creek and one site in Willis Creek. At each site two individual ‘shots’ were made and the results aggregated for each site. All fish were identified and released in the field. The results of the seine net samples are displayed in Table 7.3. In comparison with previous studies (e.g. the NSW estuarine fish biodiversity study reported in Section 4 of the Comprehensive Coastal Assessment) the diversity of captured fish was very low in each of the three estuaries. Seven species of fish and two types of crustacean were encountered during the study. With the exception of an unidentified cardinal fish (probably Psuedamia sp.) all the fish species sampled had been observed in these waters during the NSW estuarine fish biodiversity study. Bait traps were set amongst structural habitat in two locations in Willis Creek and Woolgoolga Lake and one location in Darkum Creek (see Illustration 7.1). At each site, five bait traps were set over a 10 – 15 m long area. The traps were set for approximately 7 hours during the day and baited with a mixture of aniseed scented pellets and sardines. All fish were identified, counted and released in the field. Results were aggregated for each site. The results of bait trapping are displayed in Table 7.4. Low numbers of fish and a low diversity of species were collected using bait traps. No fish were trapped at either site in Woolgoolga Lake. Only one species that was not collected using the seine net was collected using bait traps, the Flathead gudgeon (Phylipnodon grandiceps). Flathead gudgeons were encountered in all three waterways during the NSW estuarine fish biodiversity study.


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Table 7.3 Results of fish sampling using a seine net.

Species Name Common Name Darkum Creek

Woolgoolga Lake

Willis Creek

SN1 SN2 SN1 SN2 SN1 Fish Silago Cilliata Sand Whiting 24 5 - - 15

Gerres subfasciatus Silver Biddy 7 12 2 10 - Redigobius macrostoma Large mouth goby 1 9 1 - - Favonigobius tamarensis Tamar river goby - 4 6 19 1 Ambassis sp Glass fish - 102 546 - 73 Family: Apogonidae Unidentified cardinal fish - 11 - - 6 Mugil cephalus Sea mullet - - - 69 -

Crustaceans Family: Palaemonidae Shrimp 3 1 2 14 1 Family: Penaedae Prawn - - 1 - 3

Total Individuals 35 144 558 112 99 Total Taxa 4 7 6 4 6

Table 7.4 Results of fish sampling using bait traps.

Species Name Common Name Darkum Creek

Woolgoolga Lake Willis Creek

BT1 BT1 BT2 BT1 BT2

Fish

Redigobius macrostoma Large mouth goby 1 - - - - Favonigobius tamarensis Tamar river goby - - - 3 - Phylipnodon grandiceps Flathead gudgeon 3 - - - 1 Ambassis sp Glass fish - - - 1 -

Crustaceans Family: Palaemonidae Shrimp - - - 21 2 Family: Penaeidae Prawn - - - 3 11

Total Individuals 4 0 0 28 14 Total Taxa 2 0 0 4 3

The conditions in the period leading up to the fish sampling had been good for fish recruitment to the estuaries. All three creeks had been open to the ocean for significant periods in January and February 2011. Whilst the diversity in late autumn is expected to be lower than during the summer the following factors also may have contributed to the low diversity encountered: � the absence of submerged aquatic flora and limited availability of suitable structural aquatic habitats for fish; � entrance breakout in the week prior to the survey and poor water quality experienced after heavy rainfall;

and � the limited scope of the survey and limited ability to sample structural habitats. 7.2.3 Incidental observations of fauna A variety of fauna were observed incidentally during field work undertaken as part of this study. Table 7.5 gives a summary of incidental observations.


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Table 7.5 Incidental observations of fauna.

Species Common Name Darkum Creek Woolgoolga Lake Willis

Creek Habitat Associations

FISH Mugil cephalus Sea mullet X X Surface water Liza argentea Flat tail mullet X Surface water Acanthopagrus australis

Silver bream X Bare sand, gravel bars

Platycephalus fuscus

Dusky flathead X Bare sand, mud

Daysiatus thatidus Black sting ray X

CRUSTACEANS Scylla serrata Mud crab X Mangroves, intertidal

mud BIRDS

Ixobrychus flavicollis

Black bittern X X X Intertidal mudflats, mangroves

Alisterus scapularis

King parrot X Riparian vegetation

Eurystomus orientalis

Dollar bird X Riparian vegetation

Malurus cyaneus Superb fairy-wren X Riparian vegetation

Rhipidura leucophrys

Willie wagtail X X Riparian vegetation

Egretta novaehollanidae

White faced heron X X X Creek margins,

intertidal flats Ardea alba Great egret X Haliaeetus leucogaster

Sea eagle X

Pandion haliaetus Osprey X Todiramphus sanctus

Sacred kingfisher X X X Riparian vegetation,

mangroves, open water Alcedo azuria Azure

kingfisher X Riparian vegetation, open water

Phalacrocorax varius

Pied cormorant X X X Open water, snags

Phalacrocorax sulcirostris

Little black cormorant X Open water, snags

Chenonetta jubata Australian wood duck X X Open water

Centropus phasianinus

Pheasant coucal X Riparian vegetation


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Species Common Name Darkum Creek Woolgoolga Lake Willis

Creek Habitat Associations

Vanellus miles Masked lapwing X Intertidal flats,

saltmarsh REPTILES

Physignathus lesueurii

Water dragon X X X Riparian vegetation and snags

MAMMALS Macropus giganteus

Eastern grey kangaroo

X X X Riparian vegetation, intertidal flats

7.3 Threatened and Protected Species and Communities No threatened aquatic species have been individually reported from any of the three waterways. The results from a database search are detailed in Appendix J. The following information summarises the search results relevant to the estuaries: � seventy five bird species were identified by the combined searches. Of these, 11 were considered to have a

possible interaction with riparian zones or upstream wetlands, 2 were waterfowl mostly associated with freshwater habitats and 20 were either waders, shorebirds or fishing birds strongly associated with estuaries;

� ten amphibians listed under the TSC Act were indentified from within the CHLGA. Of these there were 3 that could potentially inhabit upstream freshwater wetland habitats within the study area. These are the endangered green and golden bell frog (Littoria aurea), and the vulnerable wallum froglet (Crinia tinnula) and olongburra frog (Litoria olongburensis). The green and golden bell frog and the olongburra frog are also listed as vulnerable under the EPBC Act; and

� thirty five mammals were identified by the combined searches. One of the key species directly associated with the study area is the Grey-headed Flying-fox. Refer to Section 7.3.2 for further discussion.

A search of TSC Act listed endangered ecological communities in the CHLGA identified 11 listings. Refer to Appendix J for further details of endangered terrestrial vegetation communities. The EPBC Act lists protected migratory species included in international treaties such as JAMBA (Japan Australia Migratory Bird Agreement), CAMBA (China Australia Migratory Bird Agreement) and the Bonn Convention. Relevant results from a search of listed species revealed: � eight terrestrial birds that possibly utilise the area (some of which would be likely to have a strong

association with the estuaries); � five migratory wetland birds that possibly utilise the area (all of which could potentially have a strong

association with the estuaries); � 18 migratory marine birds that possibly use the area most of which would be unlikely to have a strong

association with the estuaries. One of the exceptions is the Little Tern – refer to Section 7.3.1; and � five migratory marine reptiles (some of which could possibly have an association with the estuaries). 7.3.1 Little Terns The Little Tern (Sterna albifrons) is listed as an Endangered Species under the Threatened Species Conservation Act 1995 (TSC Act) and a Migratory Species under the Environmental Protection and Biodiversity Conservation Act 1999 (EPBC Act). It is the smallest Australian member of the family Laridae. The populations which occur in NSW are migratory, occurs mainly between Spring and Autumn. In NSW they occur exclusively in


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coastal environments, nesting and roosting in estuaries or on beaches, and foraging in nearby waters (NSW NPWS 2003). Two different populations appear to occur in NSW: � South-eastern Australian population which are breeding migrants, and spend non-breeding periods in south-

east Asia; and � Asian population which are non-breeding migrants, and breed in Asia (NSW NPWS 2003). 7.3.1.1 Local Significance One of the most significant breeding sites for the Little Tern (South-eastern Australian population) in NSW in recent times is located at the Willis Creek / Hearns Lake entrance area. The site is located on crown land (managed by the Land and Property Management Authority - LPMA) and is being actively managed seasonally to protect the nesting colony in a joint project undertaken by Department of Environment, Climate Change and Water (DECCW) Northern Branch National Parks and Wildlife Service (NPWS) and Coffs Harbour City Council (CHCC). The Willis Creek entrance area was reportedly a valuable Little Tern breeding site prior to approximately 40 to 50 years ago (Paul Parramore, unpublished). In recent years the Little Tern has begun to reuse the site. It is unclear as to why the species has returned or been absent from the site, as a range of factors influence potential nesting site usage, including natural coastal erosion and deposition processes that influence the structural suitability of a site; seasonal suitability of alternative sites; human induced disturbances; and predation. The Little Tern is particularly sensitive to predation and disturbances (Paul Parramore, unpublished). . During the 2009/2010 season, the nesting colony at the Willis Creek mouth area consisted of approximately 200 individuals at the start of the season, however was reduced to just 60 individuals with only 16 chicks hatching by the end of the season. This was believed to be primarily due to disturbances from dogs vehicles and kite surfers (Nigel Costell, 2010 in press). CHCC and NPWS have consequently identified the need to undertake responsive active management of the site. Upon completion of the October 2010/2011 monitoring season, between 150 and 200 individuals have been recorded at the site. A Shorebird Recovery Program (Paul Parramore, unpublished) has been devised to guide management of the site. Current management initiatives include: � staged fencing off of the nesting site to restrict human, domestic pet and pest access (particularly Red Foxes

– Vulpes vulpes); � community awareness initiatives (including media releases and signage at the site); � seasonal monitoring (October to April) undertaken by Volunteers under the direction of Northern Branch

NPWS; � NPWS is currently liaising with the local kite-surfers on how to avoid disturbances to the Little Tern colony; � Council is investigating opportunities to limit dog access to the site, potentially by amending the Companion

Animals Management Plan so the general locality around the nesting site becomes a “leashed dog only area” when the Little Tern is present; and

� Council/NPWS are investigating opportunities to restrict vehicle access around the site when the Little Tern is present.

NPWS have advised that the revised Red Fox Threat Abatement Plan 2 (yet to be release), includes the Willis Creek mouth Little Tern nesting site as a priority area to manage the Fox (David Nalder, NPWS pers. comm.). This will enable greater access to funding and resources to undertake active fox abatement works. The management works specifically undertaken for the Little Tern, are considered to provide an umbrella effect for local biodiversity, including other locally breeding migratory and shorebirds species including the Red-capped Plover (Charadrius ruficapillus), Rainbow Bee-eater (Merops ornatus) and Striated Pardalote (Pardalotus


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striatus). It may also provide future benefits for other local threatened species such as the Sooty Oystercatcher (Haematopus longirostris) (Nigel Cotsell, CHCC Ecologist, pers. comm.). 7.3.2 Woolgoolga Lake Flying Fox Camp A Grey-headed Flying-fox (Pteropus poliocephalus) maternity camp occurs along the banks of Woolgoolga Lake, approximately 1 km north of the town centre. This species is listed as vulnerable under both the Australian Commonwealth Environment Protection and Biodiversity Conservation Act 1999 and the NSW Threatened Species Conservation Act 1995. The extent of the reserve area covers 6.8 ha, however the effective roost area has been reduced due to weed encroachment and degradation to approximately 1 ha (Our Living Coast 2010). In order to protect, restore and manage the camp Coffs Harbour City Council (CHCC), as part of the Our Living Coast program, plan on developing a Flying-fox Management Strategy and obtain approval from both state and federal governments. The aims of the strategy are to achieve an equitable balance between conservation and the social, cultural, aesthetic and environmental values shared by the community (Our Living Coast 2010). The document would include vegetation management, direct amelioration of concerns within the community, information packages, links, protective fencing, signage and tourist interpretive materials. Key objectives of the strategy include: � restore the Endangered Ecological Community components; � restore the area’s value as Secondary Koala Habitat as mapped under the Coffs Harbour KPoM 1999; � increase the area’s value as a Wildlife Corridor and link to Regional Park; � protect and enhance the Woolgoolga Lake riparian and coastal values; � provide for the community’s needs in terms of recreation, education and interpretation of these values to

ensure the long-term management of the camp; � identify the management issues and works required with regard to the camps coastal position and actions to

address them; and � incorporate all of Council’s legal, community and cultural protection responsibilities (Our Living Coast 2010). 7.4 Riparian Vegetation Plants growing alongside waterways are known as riparian vegetation. They provide organic material to the food chain, stabilise banks against erosion and provide important shade that can reduce water temperatures and camouflage fish from predators. Riparian vegetation also provides habitat for birds and other native animals. The riparian vegetation communities in the study area are diverse and range from dry sclerophyll open grey gum and blackbutt forests in the upper reaches of the estuaries to swamp sclerophyll open paperbark and swamp oak forests, mangrove forests, saltmarshes, sedgelands, and estuarine wetlands in the mid to lower reaches, and coastal health and banksia and acacia dune communities in the lower reaches. The following sections outline the results of the riparian vegetation condition assessment and invasive weed surveys undertaken in January 2011. 7.4.1 Riparian Vegetation Condition The condition of riparian vegetation was mapped during the January 2011 field survey. The condition assessment rated the riparian vegetation based upon cover, diversity, structure (appropriate to the vegetation community), and integrity (presence of invasive weed species). The results of the riparian vegetation mapping are shown in Illustration 7.8 to Illustration 7.10. Riparian vegetation through the study area is in moderate to very good condition (96% of surveyed banks) with only a single reach on the southern foreshore of Woolgoolga Lake classified as poor to very poor (3%: impacted


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by foreshore clearing presumably for resident’s views). Table 7.6 summarises the condition for each estuary and for the study area as a whole. Table 7.6 Riparian vegetation condition by estuary system in the Darkum/Woolgoolga/Willis Creek

study area (mapped January 2011)

Estuary Total

length

(m)

Very Poor

(m)

Poor

(m)

Mod.

(m)

Good

(m)

Very Good

(m)

Very Poor

(%)

Poor

(%)

Mod.

(%)

Good

(%)

Very Good

(%)

Darkum Creek 5045 - - 639 1784 2622 - - 13% 52% 35%

Woolgoolga Creek 7957 168 406 1327 3890 2166 2% 5% 17% 49% 27%

Willis Creek 3379 - - 561 2471 287 - - 17% 73% 9%

TOTAL 16381 168 406 2527 8145 5075 1% 2% 15% 50% 31%

7.4.2 Riparian Weed Mapping Introduced weed species occur along the length of the three estuaries. The major weed species identified include bitou bush (Chrysanthemoides monilifera), coastal morning glory (Ipomoea cairica), groundsel (Baccharis halimifolia), pink lantana (Lantana camara), camphor laurel (Cinnamomun camphora), winter cassia (Senna pendula glabrata), ground asparagus (Asparagus aethiopicus), and noogoora burr (Xanthium occidentale). Other exotic plants including introduced grasses and assorted garden escapees occur in various locations within the study area but have not been mapped for this study. According to the Northern Rivers Invasive Plants Action Strategy 2009-2013 (Oakwood, 2009), groundsel bush is the highest priority (Priority B) invasive weed species mapped during the field assessment. Other weeds listed within the strategy include: � in coastal landscapes: winter cassia and bitou bush (Priority C) and coastal morning glory and ground

asparagus (Priority D); and � in riparian landscapes: lantana (Priority C), camphor laurel (Priority D), and blue morning glory and coastal

morning glory (Priority E). All other mapped environmental weeds are not identified as priority weeds in either coastal or riparian landscapes within the strategy. The distribution of the Priority B and C invasive weeds mapped in the riparian zones of the three estuaries surveyed is provided in Illustration 7.11 to Illustration 7.13.

SAFETY BEACH

MULLAWAY


IllustrationRiparian Vegetation Condition in Darkum Creek Estuary

North 7.

Drawn by: AMM Checked by: RE Reviewed by: TIM Date: May 2011Source of base data: Coffs Harbour City CouncilInformation shown is for i llus trative purposes only

L E G E N D Dar um Cree Estuary catchmentery Good

GoodModerate

Saety

ea ch

0 300

Darkum Creek

Wool g oolga Beach

W

Woolgoolga Lake

CreekWoolgoolga

S E E CH


Illustration

iparian egetation Condition in Woolgoolga ake Estuary(mapped anuary 20 )

North 7.9

Drawn by: RE Checked by: MVE Reviewed by: TIM Date: May 2011Source of base data: Coffs Harbour City CouncilInformation shown is for i llus trative purposes only

L E G E N D Woolgoolga Lake estuary catchmentVery GoodGoodModeratePoorVery Poor

0 200


Illustrationiparian egetation Condition in Willis Creek Estuary (mapped anuary 20 )

North 7.10


L E G E N D Willis Creek estuary catchmentGoodModerateVery Good Hear

ns Lake

Beach

Willis Creek

0 100

SAFETY BEACH

MULLAWAY


Illustration

Distribution of Priority B and Priority C InvasiveWeed Species in Darkum Creek Estuary (mapped January 2011)

North 7.11

Drawn by: AMM Checked by: RE Reviewed by: TIM Date: May 2011Source of base data: Coffs Harbour City CouncilInformation shown is for i llus trative purposes only

L E G E N D Dar um Cree Estuary catchment

itou ushGroundsel ushGroundsel ush and SennaGroundsel ush Senna and LantanaSenna and Lantana

Saety

ea ch

0 300

Darkum Creek

Wool g oolga Beach

W

Woolgoolga Lake

Creek

Woolgoolga

S E E CH


Illustration

istribution of riority and riority C n asi e Weed Spe ies in the Woolgoolga Creek Estuary (mapped anuary 20 )

North 7.12


L E G E N D Woolgoolga Lake estuary catchmentGroundsel bush, Senna and, LantanaSenna and LantanaLantana

0 200


Illustration

istribution of riority and riority C n asi eWeed Spe ies in the Willis Creek Estuary (mapped anuary 20 )

North 7.13


L E G E N D Willis Creek estuary catchmentBitou BushGroundsel BushGroundsel Bush and LantanaGroundsel Bush and SennaGroundsel Bush, Senna and LantanaLantanaSenna and Lantana Hear

ns Lake

Beach

Willis Creek

0 100


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7.5 Estuarine Health No definitive system exists for the quantitative assessment of estuarine health. Instead, there are a number of physical and biological indicators of estuarine health that are commonly used in a qualitative fashion. These are: � water Quality, using measures such as Chlorophyll, physical attributes, nutrients and pathogens; � sediment Quality, using measures such as benthic invertebrates, CO2 flux, contaminants, and sediment

denitrification efficiency; � habitat Extent and Quality, using indicators such as changes in area, maturity index and habitat variability

index; � biotic indicators such as Benthic Invertebrates, Fish Assemblages, Macroalgae, Seagrass, Shorebirds and

Hermit Crabs; and � ecosystem Integrity using algal blooms, pest invasions and fish kills. The utility of the above indicators depends upon the length, intensity and accuracy of data collection activities. In assessing the health of Darkum Creek, the following comments can be made: � water quality is generally acceptable for the protection of aquatic ecosystems; � saltmarsh and mangrove habitats are in good condition and mangroves are widely dispersed throughout the

estuary. There is evidence of consistent recruitment of mangroves. A large area of seagrass has disappeared from the estuary since 2004. The riparian corridor is largely intact. There are also many snags throughout the estuary, providing valuable structural habitat;

� fish and macroinvertebrate populations are scarce and lack diversity; � there is no evidence of fish kills, pest invasions or algal blooms; and � in general, the health of Darkum Creek is good. In assessing the health of Woolgoolga Lake, the following comments can be made: � water quality in Woolgoolga Lake is generally acceptable for recreational use and for the protection of

aquatic ecosystems; � saltmarsh is scarce and poorly managed. Mangroves appear to be recruiting to the system, a positive

indication. Seagrass appears to have disappeared from the system in the past decade, though the original extent is unknown. Weeds and other disturbances to riparian vegetation are common;

� fish and macroinvertebrate populations are scarce and lack diversity; � fish kills have been related to pesticide spills; � algal blooms and pest invasions do not appear to be an issue; and � in general, the health of Woolgoolga Lake is average. In assessing the health of Willis Creek, the following comments can be made: � there is a lack of recent water quality data. Sediment quality data would also be useful as excess nutrients

are likely to have been stored in the benthic sediment. Previous water quality data indicated that Willis Creek suffered from excessively high nutrient concentrations;

� saltmarsh and mangrove habitats are in relatively good condition. The riparian corridor is negatively impacted by weeds but well protected against erosion and well vegetated;

� fish and macroinvertebrate populations are scarce and lack diversity, though macroinvertebrate diversity appears to be improving;

� blue green algae occurs in frequent small patches. There are no reported fish kills; and � there is too little information to make an informed assessment of the health of Willis Creek.


136

7.6 Bushfire Management The Coffs Coast Regional Park (North Section) and Garby Nature Reserve Fire Management Strategy (Type 2) (2005) (FMS) maps the bushfire suppression, risk management information and the status of fire thresholds for areas surrounding Darkum Creek, Woolgoolga Lake and Willis Creek. Bushfire risk management mapping of the park identifies asset protection, strategic fire advantage and land management zones within the Coffs Coast Regional Park. Illustration 7.14 identifies areas within the Darkum Creek, Woolgoolga Lake and Willis Creek estuary catchment areas that are mapped as asset protection and land management zones. The Fire Management Strategy states the “objectives of APZs is the protection of human life and property. This will have precedence over guidelines for the management of biodiversity. Maintain overall fuel hazard at moderate or below.” Asset protection zones are located generally in areas between bushland and residential areas within the Coffs Coast Regional Park. The APZs and the agency responsible for their maintenance as identified within the FMS are listed in Table 7.7 below. Table 7.7 Coffs Coast Regional Park FMS Asset Protection Zones

Asset Protection Zone Name Responsibility Estuary Catchment Area APZ – Darkum Road NPWS Darkum Creek

APZ – Safety NE; NPWS Darkum Creek APZ – Safety School CHCC Woolgoolga Lake APZ – Safety South NPWS Woolgoolga Lake APZ – Market Street CHCC Willis Creek

APZ – Lane Way CHCC Willis Creek 7.7 Impacts of Climate Change The key physical drivers associated with climate change that have the potential to impact upon the ecology of ICOLLS such as Darkum Creek, Wooolgoolga Lake and Willis Creek are as follows (following Haine 2008): � an increase in the average sea level, leading to an increase in average levels during entrance open

conditions; � a landward and upward shift in the beach profile for Woolgoolga Lake, leading to an increase in the average

level during entrance closed conditions; � increased overall volume of the waterways; � increased intensity of flood events; � reduced overall rainfall runoff; and � increased water temperature and ocean acidification. Increases in the average level of the waters of the three estuaries are likely to have an impact upon the distribution and extent of mangroves and saltmarshes. Mangroves and saltmarshes are likely to migrate in a landward direction where topography allows (Lovelock et al 2009). This is likely to ‘squeeze’ the current area of saltmarsh between the southern shores of Woolgoolga Lake and Sunset Lakes Estate. Where barriers to this migration exist current mangrove and saltmarsh distribution will be lost. It is uncertain how sediment accretion


137

rates will affect this scenario. Similar impacts might also occur for fauna that rely on fringing and intertidal habitats for nesting and feeding. Increased volume and therefore depth of the waterways has the potential to negatively affect productivity of the estuaries. Benthic microalgae are a major contributor to the overall productivity of ICOLLs such as Woolgoolga Lake through their role as primary producers. Increased depth can negatively impact upon benthic microalgal production via reductions in light availability at the benthic level and also through increasing stratification and reduced wind driven resuspension (Haines 2008). Increasing frequency and intensity of storm events is forecast under current climate change scenarios. This has the potential to impact upon estuary ecology via increasing frequency of poor water quality events and also through changes to entrance dynamics. Rainfall influences species composition and diversity in estuarine wetlands. Decreases in the overall rainfall may negatively impact upon the growth, diversity and productivity of mangroves (Lovelock et al 2009) and also result in reduced abundance of fish (Booth et al. 2009) Increasing water temperatures have the potential to lead to increased episodes of harmful algal blooms. This may be exacerbated by increased delivery of nutrients from the catchment caused by increasing intensity and frequency of storms (Haines 2009) and also by increased delivery of tropical species of microalgae due to a strengthening of the east Australian current (Hallegraeff et al 2009).

Darkum Creek

Woolgoolga Lake

Willis Creek


Illustration

Bushfire Risk Management

North 7.14

Drawn by: AMM Checked by: RE Reviewed by: TIM Date: May 2011Source of base data: Coffs Harbour City Council and National Parks and Wildlife ServiceInformation shown is for illustrative purposes only

L E G E N D Estuary catchment oundariesAsset Protection oneLand Management oneStrategic ire Advantage one

0 600

ecological processes€¦ · overhanging vegetation and root balls in the bank create structured...

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