KANGAROO ISLAND
An assessment of selected inland wetlands
of Kangaroo Island, South Australia.
Author Russell Seaman
Scientific Officer, Wetlands Management.
National Parks and Wildlife Cartography and design
Russell Seaman Photographs Russell Seaman
Geographical Information System Data
Supplied by Geographical Analysis and Research Unit, Planning SA, Department for Transport, Urban Planning and the Arts.
and
The Department for Environment and Heritage, South Australia.
Funding Sources Environment Australia National Parks and Wildlife SA
Acknowledgments
In the preparation of this report the expertise, advice and support of several people is greatly appreciated.
• Rob Walsh
• Roman Urban, DEH.
• Sandy Carruthers, Planning SA.
• Tim Croft, DEH.
• Kylie Moritz, DEH.
Executive Summary
During Novemeber and December 2000 a wetland inventory was undertaken on Kanagaroo Island which documented a representative sample of inland wetlands by recording their physical, chemical and biological attributes. Twenty-six wetlands were surveyed and included saline lake systems (19 sites), brackish water bodies and freshwater wetlands. Breakneck River and Six-mile Lagoon are classified as the only freshwater wetlands surveyed.
The aquatic invertebrate fauna was notably scarce in many of the salt lakes surveyed, however, 14 wetlands displayed good invertebrate trophic levels. The correlation between increasing salinity levels and decreasing biological activity was clear; this decline is of concern for the health of many wetlands on Kangaroo Island.
Sixteen wetlands surveyed are considered to be nationally important by meeting the
ANZECC criteria of being a good example of a wetland type occurring within a biogeographic region in Australia. These wetlands include Six-mile Lagoon, Duck Lagoon and Destree Swamp. Three wetlands are recommended for monitoring; these are Grassdale lagoon, Six- mile Lagoon and Rush Lagoon.
SECTION ONE - WETLAND INVENTORY... 9
1.0 INTRODUCTION ... 9
2.0 REPORT STRUCTURE... 9
3.0 PROJECT SCOPE ... 9
4.0 OVERVIEW OF PAST WETLAND INVENTORY STUDIES ... 10
5.0 WETLAND RISK ASSESSMENT ... 11
6.0 WETLAND INVENTORY METHODOLOGY ... 12
6.1 STUDY AREA BOUNDARIES... 12
6.2 SITE SELECTION... 12
6.3 GIS DATABASE... 12
6.4 WETLAND INVENTORY SURVEY... 13
7.0 WETLAND SURVEY TEMPLATE... 13
SECTION TWO - WETLAND ASSESSMENT FOR KANGAROO ISLAND... 14
8.0 INTRODUCTION ... 14
8.1 WETLAND OVERVIEW... 14
9.0 WETLAND LAND USE ... 15
9.1 BACKGROUND... 15
9.2 ANALYSIS... 15
10.0 TENURE AND MANAGEMENT AUTHORITY... 16
10.1 BACKGROUND... 16
10.2 ANALYSIS... 16
11.0 ENVIRONMENTAL ASSOCIATIONS AND IBRA REGIONS ... 17
11.1 BACKGROUND... 17
11.2 ANALYSIS... 17
12.0 KEY BIODIVERSITY AREAS... 18
12.1 BACKGROUND... 18
12.1 ANALYSIS... 19
13.0 WETLAND AREA... 19
13.1 BACKGROUND... 19
13.2 ANALYSIS... 19
14.0 LANDFORM ELEMENT ... 20
14.1 BACKGROUND... 20
14.2 ANALYSIS... 20
15.0 GEOLOGY... 21
15.1 BACKGROUND... 21
15.1 ANALYSIS... 21
16.0 HYDROLOGY... 22
16.1 BACKGROUND... 22
16.2 ANALYSIS... 22
18.0 DEGRADATION AND DISTURBANCE ... 26
18.1 BACKGROUND... 26
18.2 ANALYSIS... 26
19.O AQUATIC VEGETATION CLASSES ... 27
19.1 BACKGROUND... 27
19.2 ANALYSIS... 27
20.0 AQUATIC FAUNA ANALYSIS... 29
20.1 INVERTEBRATES... 29
20.1.1 Ecological benefits ... 29
20.1.2 Trophic dynamics... 29
20.2 TEMPORARY WETLANDS... 30
20.3 SALINE SYSTEMS... 31
20.4 ANALYSIS... 31
20.4.1 Frequency of invertebrate occurrence ... 31
20.4.2 Trophic levels... 34
20.5 AMPHIBIANS... 38
20.6 FISH... 38
20.7 MAMMALS... 38
20.8 AVI-FAUNA... 38
21.0 WATER CHEMISTRY ... 39
21.1 PH... 40
21.1.1 Background... 40
21.1.2 Analysis... 41
21.2 CONDUCTIVITY... 41
21.2.1 Background... 41
21.1.2 Analysis... 42
21.3 TURBIDITY... 44
21.3.1 Background... 44
21.3.2 Analysis... 46
21.4 WATER TEMPERATURE... 46
21.4.1 Background... 46
21.4.1 Analysis... 47
21.5 DISSOLVED OXYGEN... 47
21.5.1 Background... 47
21.5.2 Analysis... 48
22.0 RAPID ASSESSMENT... 49
22.1 AQUATIC FAUNA... 49
22.2 AQUATIC FLORA... 50
22.3 RIPARIAN VEGETATION RAPID ASSESSMENT... 51
22.3.1 Analysis - Toe of bank ... 51
23.3.2 Bank ... 52
23.3.3 Buffer ... 52
23.0 WETLAND CONDITION SCORE... 53
24.0 RAPID ASSESSMENT TOTAL SCORE... 54
25.0 ANZECC WETLAND CRITERIA... 55
25.1 ANALYSIS... 55
26.0 WETLAND TYPES ... 57
26.1 Analysis... 58
SECTION THREE - WETLAND MONITORING... 59
27.0 INTRODUCTION ... 59
27.1 Ecological change... 59
28.0 MONITORING PROTOCOLS AND INDICATORS ... 61
28.1 EARLY WARNING INDICATORS... 62
28.2 TOXICITY TESTS... 62
28.3 FIELD EARLY WARNING INDICATORS... 63
28.4 RAPID ASSESSMENTS... 63
29.0 RECOMMENDED INDICATORS FOR MONITORING SURVEYED WETLANDS... 63
29.1 EARLY WARNING INDICATORS – WATER CHEMISTRY... 63
29.2 ECOSYSTEM BASED INDICATOR... 64
29.3 OTHER CONSIDERATIONS... 64
30.0 RECOMMENDED WETLANDS TO MONITOR ... 65
30.1 RECOMMENDED PRIORITY WETLANDS TO MONITOR... 65
31.0 RECORDING MONITORING PARAMETERS ... 66
BIBLIOGRAPHY ... 67
APPENDIX 1 WETLAND INVENTORY DESCRIPTIONS... 71
APPENDIX 2 INVERTEBRATE RECORDS FOR SURVEYED WETLANDS... 82
Figures
FIGURE 9-1. ON SITE WETLAND LAND USES... 15
FIGURE 11-1. NUMBER OF WETLANDS LOCATED IN ENVIRONMENTAL ASSOCIATIONS... 17
FIGURE 12-1. WETLANDS WITHIN KEY BIODIVERSITY AREAS... 18
FIGURE 13-1. WETLAND AREA. ... 19
FIGURE 14-1. WETLAND LANDFORM ELEMENTS. ... 20
FIGURE 19-1. AQUATIC VEGETATION TYPES... 27
FIGURE 20-1. INVERTEBRATE SCORES. ... 34
FIGURE 21-1. TEMPORARY WETLAND CYCLES... 39
FIGURE 21-2. PH VALUES... 40
FIGURE 21-3. FISH ACTIVITY AGAINST TURBIDITY VALUES AND TIME... 45
FIGURE 22-1. AQUATIC FAUNA RAPID ASSESSMENT... 49
FIGURE 22-2. AQUATIC FLORA RAPID ASSESSMENT... 50
FIGURE 22-3. RAPID ASSESSMENT, LOW – HIGH WATER... 51
FIGURE 22-4. RAPID ASSESSMENT, BANK... 52
FIGURE 22-4. RAPID ASSESSMENT, BUFFER... 52
FIGURE 23-1. WETLAND SCORE... 53
FIGURE 24-1. RAPID ASSESSMENT SCORES. ... 54
FIGURE 26-1. WETLAND TYPES IN KANGAROO ISLAND... 58
Plates PLATE 1. DUCK LAGOON... 15
PLATE 2. SIX MILE LAGOON 2... 16
PLATE 3. LUNETTE ADJACENT TO WHITE LAGOON. ... 21
PLATE 4. SIX MILE LAGOON... 22
PLATE 5. HALLS ROAD SWAMP... 25
PLATE 6. DESTREE SWAMP... 25
PLATE 7. CYGNET RIVER LAGOON... 25
PLATE 8. HALLS ROAD SWAMP... 26
PLATE 9. RUSH LAGOON... 28
PLATE 10. GRASSDALE LAGOON... 28
PLATE 11. DISCOVERY LAGOON... 28
PLATE 12. DIACYPRIS CF.SPINOSA... 32
PLATE 13. DICROTENDIPES SP. ... 32
PLATE 14. TRICOPLERA OECETIS. ... 32
PLATE 15. CHIRONOMIDAE... 36
PLATE 16. ANISOPS. ... 36
PLATE 17. SIX MILE LAGOON... 42
PLATE 18. DUCK LAGOON... 43
PLATE 19. BIG WHITE SALT LAGOON... 43
PLATE 20. SALT LAKE... 43
PLATE 21.. NEPEAN BAY LAGOON... 47
PLATE 22. RUSH LAGOON. ... 48
PLATE 23. CYGNET RIVER LAGOON. ... 48
PLATE 24. LASHMAR LAGOON. ... 51
PLATE 25. GRASSDALE LAGOON... 53
PLATE 26. BREAKNECK RIVER... 56
PLATE 27. GRASSDALE LAGOON... 56
PLATE 28. BAY LAKE... 58
PLATE 29. EMANUAL LAGOON... 58
Maps
Map 1 Kangaroo Island wetland study area Map 2 Surveyed wetlands on Kangaroo Island Map 3 Environmental Regions on Kangaroo Island Map 4 Key Biodiversity Areas on Kangaroo Island
Map 5 Geological Features underlying surveyed wetlands
SECTION ONE WETLAND INVENTORY 1.0 INTRODUCTION
Kangaroo Island is one of the few remaining regions in South Australia with inland temperate freshwater wetlands in near natural condition. The freshwater wetlands on Kangaroo Island are unique because many are independent from river systems forming their own hydrological unit within the landscape.
This Wetland Inventory of Kangaroo Island documents a representative sample of inland wetlands and records their physical, chemical and biological attributes. From this information, aquatic environments that contain high biodiversity are highlighted, and threats documented.
The inventory provides a snap shot of the condition and conservation value of wetlands throughout Kangaroo Island. Those wetlands that meet one or more of the Australian and New Zealand Environment and Conservation Council (ANZECC) criteria for an important wetland will be nominated for inclusion into the National Directory of Important Wetlands in Australia.
The Wetland Inventory for Kangaroo Island is an initiative of the Wetland Section-
Environment Australia and the South Australian Department for Environment and Heritage.
2.0 REPORT STRUCTURE
This report is divided into three sections, namely of the wetland inventory, wetland assessment and wetland monitoring.
Section 1 - Wetland Inventory. Outlines the project aims and inventory methodology.
Section 2 - Wetland Assessment. Provides an analysis of the wetland inventory, which includes the identification of wetland values and threats.
Section 3 – Wetland Monitoring. Discusses frameworks for monitoring, and recommends indicator species for monitoring and specific wetlands to monitor.
3.0 PROJECT SCOPE
The project scope consist of five actions, these are to:
1. Undertake baseline wetland surveys for inland surface waters in on Kangaroo Island.
2. Identify wetlands of conservation significance, according to agreed ANZECC classification.
3. Provide digital coverage of spatial boundaries of identified wetlands in ARC/INFO compatible format at appropriate scale, in consultation with Planning SA.
4. Produce a report detailing the physical, biological and chemical attributes of wetlands on Kangaroo Island.
5. Nominate wetlands of significance for inclusion in the Directory of Important Wetlands in Australia.
4.0 OVERVIEW OF PAST WETLAND INVENTORY STUDIES
The most comprehensive listing of wetlands in South Australia in terms of numbers and coverage is by Lloyd and Balla (1986). This study identified approximately 1500 wetlands and complexes state-wide.
The Lloyd and Balla listing was a desktop study that collated and recorded information within a standard format. This included:
• wetland type • aquatic and fringing vegetation
• name • wetland condition
• location • water regime
• size • landuse
• catchment • impacts
• aquatic fauna • tenure .
The Lloyd and Balla report provides a good starting point in understanding the extent and some attributes of South Australian wetlands. However, the study falls short in providing up to date information on invertebrate composition, water chemistry and basic landform
information. Fifty-three wetlands are documented for Kangaroo Island in the Lloyd and Balla report, this includes swamps, lakes and rivers.
In 1984, Barritt completed a study of the water resources on Kangaroo Island. Barritt describes six different groups of lagoons on Kangaroo Island and surveyed a total of 36 lagoons, 14 river sites and five dryland areas. His report provides a general overview of wetland resources through field notes and observations.
Since Lloyd and Balla’s 1986 report, several state-wide studies have mirrored this kind of information collection and presentation, but have generally not collected detailed field baseline wetland information. None-the-less, good information has been generated for certain areas including the Murray River corridor, for example, Thompson’s (1986) study documented, mapped and described the River Murray Wetlands and Jensen et al (1996) Wetland Atlas Report of the South Australian Murray Valley Wetlands made inroads into spatially capturing the locations through the use of GIS. The introduction of linking wetlands with GIS enabled the creation of a wetlands GIS database for the Murray Valley Wetlands. In 1997 Carruthers and Hille developed a GIS database for the South East wetlands. This database recorded wetland type, name, complex, watercourses and assigned a condition score and conservation value. The benefits of collecting data and linking it to GIS became evident not only for environmental planning and for information retrieval, but also for reporting to Environment Australia on the extent of wetland resources.
In 1993 the Australian Nature and Conservation Agency published the first edition of ‘A Directory of Important Wetlands in Australia’. A second edition was complied in 1996, which included information on 68 wetlands in South Australia, 13 of which are located on Kangaroo Island. This constitutes 72% of the important wetlands in the Mount Lofty Block IBRA region, (Willoughby, N. et al 2001)
De Jong and Morelli (1996) commented that in compiling the Directory of Important Wetlands it became apparent that several regions within South Australia were lacking baseline wetland information. They suggested that there is a need for systematic inventories, biological
surveys and research programs in many areas of the State. Wetland information in regions
The Wetland Inventory for the Kangaroo Island combines some of these recommendations, including continuing the development of a GIS database and providing baseline information which includes physical, chemical and biological information for wetlands on Kangaroo Island.
5.0 WETLAND RISK ASSESSMENT
The wetland risk assessment is a conceptual framework to assist in predicting and assessing change in the ecological character of wetlands. The framework has been adopted by Ramsar (resolution V11.10) and is now promoted as an integral component of the management planning process for wetlands. The relevance of undertaking wetland inventories becomes apparent within this framework. A wetland inventory ultimately collects information for the wetland assessment framework. This information is also critical in order to make
recommendations for monitoring.
A central component of the wetland risk assessment is the ability to record the ecological character of a wetland. The ecological character is the sum of the biological, physical, and chemical components of the wetland ecosystem and their interactions that maintain wetland functions and attributes. Recording changes to the ecological character of a wetland involves the development of a monitoring program, this is further discussed in Section Three –
Wetland Monitoring.
6.0 WETLAND INVENTORY METHODOLOGY
A wetland inventory essentially collects information that assists in wetland management. It can provide information for specific assessment and monitoring activities.
6.1 Study area boundaries
The project boundary is based on the Kangaroo Island Natural Heritage Trust (NHT) boundary. Refer to Map 1.
6.2 Site selection
The aim of the wetland selection process was to sample a broad range of wetlands across Kangaroo Island. Factors such as time constraints, accessibility and the project budget were limiting factors in the number of wetlands selected. Wetlands were selected initially by studying the GIS waterbody coverage for Kangaroo Island. Waterbodies within State government lands, community lands, Council managed lands, land under management agreements and Heritage Agreements were targeted for further investigation. Stakeholders such as National Parks and Wildlife were also consulted.
A total of 26 wetlands were surveyed on Kangaroo Island; refer to Map 2 for wetland locations.
6.3 GIS Database
This project builds on initiatives undertaken by Planning SA and the Department for
Environment and Heritage. GIS databases have been developed for the Murray River region by Carruthers and Nicolson (1992) and published in the form of an Atlas, Jensen et al (1996).
A GIS database exists for the South East region of the state and has been published in the form of a technical report by Carruthers and Hille (1997). No other regions in South Australia have a GIS wetland database at present. One of the project objectives is to provide a digital coverage of spatial boundaries of wetlands surveyed on Kangaroo Island.
A state wide numbering system was developed for identifying wetlands which follows the system established for the Murray River wetlands. The Murray River wetlands have been assigned the numbers S0001 to S0999. The South East region (numbers S1000 to S1999), Eyre Peninsula, (numbers S3000 to S3999), Northern Agricultural Districts numbers S4000 to S4999 and the Mount Lofty Ranges (numbers S2000 to S2999). Kangaroo Island has been assigned the numbers S5000 to S5999. The software used to produce the wetlands data is the ESRI (Environmental Systems Research Institute) geographic information system (GIS) ARC/INFO. The GIS layer was created initially from the existing land cover layer that contained areas designated as swamps, vegetated swamps, lakes and vegetated lakes. This land cover layer was mapped from 1:40 000 colour aerial photography by the Geographical Analysis and Research Unit, Planning SA, Department for Transport, Urban Planning and the Arts.
6.4 Wetland inventory survey
In developing the wetland survey, it was critical that information collected could be used for an initial assessment of wetland character. This ultimately involved the collection of physical, biological and chemical parameters. In the development of the survey template, several methodologies were studied and adapted, these include:
Ø Butcher, R.J. (1999) Assessing biodiversity in temporary and permanent wetlands. pp. 50-53 in The Other 99%. The Conservation and Biodiversity of Invertebrates, ed by Ponder, W. and Lunney, D. (1999). Transactions of the Royal Zoological Society of New South Wales.
Ø Finlayson, C.M. and Spiers, A.G. (1999). Techniques for enhanced wetland inventory and monitoring. Supervising Scientist, Canberra
Ø Fairweather, P.G. and Napier (1998). Environmental indicators for national state of the environment reporting - inland waters. Environment Australia.
Ø Maher, W. and Liston, P. (1997). Water quality for maintenance of aquatic ecosystems:
Appropriate indicators and analysis. Australia: State of the Environment Technical Paper Series.
(Inland waters). Environment Australia.
Ø Morelli, J. and de Jong, M. (1996). A Directory of Important Wetlands in South Australia. South Australian Department of Environment and Natural Resources, Adelaide.
Ø Storey, A.W., Lane, J.A.K. and Davies, P.M. (1997). Monitoring the ecological character of Australia's wetlands of international importance (RAMSAR Convention). Western Australian Department of Conservation and Land Management and Biodiversity Group of Environment Australia.
7.0 WETLAND SURVEY TEMPLATE
For each wetland surveyed physical, biological and chemical information was collected, a brief outline is given below. The complete wetland survey descriptions are given in Appendix 1.
Physical parameters
• Wetland Reference Number • Wetland name
• Ramsar Site • Description of site
• Land use • Tenure
• Land element • Geology
Biological parameters
• Vegetation associations • Noteworthy flora and fauna
• Biological threats • Aquatic vegetation classes Chemical parameters
• Dissolved oxygen • pH
• Conductivity • Temperature
SECTION TWO WETLAND ASSESSMENT FOR KANGAROO ISLAND 8.0 INTRODUCTION
Wetland assessment involves the identification, cataloguing of values and status of threats to wetlands as a basis for the collection of more specific information through monitoring. This section presents each survey parameter by discussing background information and analysis of data collected during field assessment.
8.1 Wetland overview
The Wetland Inventory surveyed two main types of inland wetlands; these are classified as saline wetlands and freshwater wetlands. The saline wetlands generally occur on the eastern section of Kangaroo Island (within the Mac Gillivary and Amberley environmental
associations). These saline wetlands are located in a largely fragmented habitat with cleared land occupying a majority of the landscape. A large concentration of saline wetlands occur approximately 20 kilometres south from Kingscote. The largest of these wetlands are Rush Lagoon, White Lagoon and Waidrowski Lagoon.
The freshwater wetlands tend to be located on the western section of Kangaroo Island with wetlands of high biodiversity values located within the National Parks and Wildlife reserve areas or areas under private conservation management. Wetlands such as Grassdale Lagoon, Six Mile lagoon and further west, Murray’s Lagoon are excellent examples of inland freshwater wetlands.
Map 2 illustrates the wetland survey locations on Kangaroo Island.
9.0 WETLAND LAND USE 9.1 Background
Land use around and in wetland areas usually dictates the level of protection and the condition of the wetland. This wetland survey is biased toward lands that have a land use favouring conservation, as these tend to contain wetlands with high biodiversity values.
Surrounding land uses are a major contributor to the processes that may threaten wetlands.
Many wetlands on Kangaroo Island are under threat from increasing resulting from the clearance of native vegetation.
9.2 Analysis
Figure 9-1. On site wetland land uses
Note: these figure include 15 sites, which were not included in the wetland survey, but information was included from Lloyd and Balla (1986) and Barritt (1982).
The importance of off-reserve wetland conservation becomes evident with 15 sites recording a land use of private conservation. Several sites (such as Rush Lagoon) are within private land and under a Heritage Agreement. Eleven wetlands surveyed have a primary land use of grazing (eg Lashmar Lagoon) and eight sites have a conservation management land use being in NPWSA reserves (eg Grassdale Lagoon). Seven sites recorded a land use of cereal and legume production.
Duck Lagoon is managed by Kangaroo Island Council as a conservation reserve.
The lagoon provides good habitat for flora and fauna, as illustrated by the presence of Australian White Ibis (Threskiornis molucca) and the Pied Cormorant (Phalacrocorax varius).
Wetland land use 7
11 15 8
Cereal and legumes Private conservation Grazing
National Parks and Wildlife reserves
10.0 TENURE AND MANAGEMENT AUTHORITY 10.1 Background
The type of management authority and tenure surrounding a wetland often dictates the type and level of protection and management for the wetland. An understanding of this also allows consideration of different legislation and approaches concerning on-site management and planning for wetland sites.
Figure 10-1. Tenure and management 10.2 Analysis
The majority of wetlands (31 sites) are managed by landholders (eg Lashmar Lagoon, Rush Lagoon, Six-mile lagoon). Local government manages two wetland sites (Duck lagoon and Chapman River) and the Department for Environment and Heritage manages eight wetlands (eg Grassdale Lagoon, Bay Lake 2, Breakneck River). Note: includes 15 sites from
information sourced from previous studies (Lloyd and Balla (1986) and Barritt (1982).
Wetland Tenure
31 2
8
1
Private
Local government
Department for
Environment and Heritage Unknow n
Six mile lagoon 2 is private land.
This lagoon is an excellent example of a freshwater wetland.
11.0 ENVIRONMENTAL ASSOCIATIONS AND IBRA REGIONS 11.1 Background
The Interim Biogeographic Regionalisation for Australia (IBRA) is a framework for
conservation planning and sustainable resource management within a bioregional context.
IBRA regions represent a landscape based approach to classifying the land surface from a range of continental data on environmental attributes. In 1999-2000, IBRA version 5 was developed. Eighty-five bioregions have been delineated, each reflecting a unifying set of major environmental influences that shape the occurrence of flora and fauna and their interaction with the physical environment. (See:
http://www.ea.gov.au/parks/nrs/ibraimcr/ibra_95/index.html)
The Wetland Inventory for Kangaroo Island is located within the Flinders Lofty Block. The Flinders Lofty Block is described as temperate, with well-defined uplands of Cambrian and late Proterozoic marine sediments. The dominate vegetation type is eucalypt open forests and woodlands and heaths on mottled yellow and ironstone gravelly duplex soils in the wetter areas and red duplex soils in drier areas; now largely cleared for agriculture and urban development, (Thackway and Cresswell 1995).
Environmental associations are the next level of complexity down from the IBRA regions, these associations were first described and mapped by Laut et al (1977).
11.2 Analysis
The Wetland Inventory covers seven environmental associations, each having unique attributes. Refer to Map 3 for Environmental Associations.
Figure 11-1. Number of wetlands located in Environmental Associations
Note: includes 15 sites from information sourced from previous studies (Lloyd and Balla (1986) and Barritt (1982).
The majority of wetlands surveyed are located in the Parndana environmental association, which covers the western and central areas of Kangaroo Island. Several wetlands located in this association have high conservation values, for example Larrikin Lagoon, Bay Lake and
Environmental Associations
3
11
2 4 4
15
3
Mt Marsden Mac Gillivary Gantheaume Coranda Amberley Parndana Cygnet
12.0 Key Biodiversity Areas 12.1 Background
Key biodiversity areas are outlined in the Biodiversity Plan for Kangaroo Island, developed by the Department for Environment and Heritage, South Australia. Key biodiversity areas have been developed through the use of existing biological data, vegetation mapping, GIS
analysis, expert knowledge and community consultation (Willoughby, Opperman, Inns 2001).
Three biodiversity areas are identified within the biodiversity plan; these are large remnant areas, threatened habitat areas and fragmented habitats. Map 4 shows the location of these biodiversity areas.
Large remnant areas
These areas have been identified on the basis that they contain large blocks of vegetation, open space linkages, species diversity and populations of species with high conservation significance.
Threatened habitat areas
Threatened Habitat Areas have been identified on the basis that they are:
• selectively cleared and modified resulting in low remnancy of plant communities;
• contain vegetation that is poorly conserved within reserve systems;
• contain large numbers of species of high conservation significance.
Fragmented habitat areas
Fragmented habitats have been identified on the basis that they are:
• contain a mixture of large blocks of native vegetation and large amounts of cleared land;
• biodiversity in areas of large blocks likely to approach that of pre-European settlement levels;
• population sizes for most species are likely to be viable in the long-term.
13
22
7
0 5 10 15 20 25
Large Remnant
Area
Threatened Habitat
Fragmented Habitat Key Biodiversity Areas
12.1 Analysis
The majority of wetlands surveyed are located within threatened habitats (22 sites) and includes wetlands surveyed in the saline district area and lagoons in Cygnet River. Wetlands surveyed in this region include Murray Lagoon, White lagoon, Salt Lake and Birchmore Lagoon. A large remnant biodiversity area is located on the western section of Kangaroo Island and encompasses Flinders Chase National Park. Thirteen wetlands were surveyed in this key biodiversity area. A biodiversity area of fragmented habitats is located in central Kangaroo Island and includes the upper drainage lines of several river systems; seven wetlands are identified in this area (eg Six-mile Lagoon).
13.0 WETLAND AREA 13.1 Background
The area of wetlands was calculated by using ArcView GIS based on waterbody mapping provided by Planning SA.
13.2 Analysis
The majority of wetlands have an area between 0 and 50 ha (18 sites). Four sites recorded areas between 51 and 100 ha and two sites recorded areas between 101 and 200 ha, namely Rush Lagoon 116 HA and Big White Salt Lagoon 105 ha. One site recorded an area between 201 and 300 ha (White Lagoon 291ha) and two sites recorded areas over 300 ha (Murray Lagoon 666 ha and Salt lagoon 400 ha). 27 wetlands were surveyed for this analysis.
Figure 13-1. Wetland area.
0 5 10 15 20
0-50 51-100 101-200 201-300 300+
Wetland Area
14.0 LANDFORM ELEMENT 14.1 Background
The landform element definitions used in the wetland inventory has been adapted from Heard and Channon (1997) Guide to a native vegetation survey using the biological survey of South Australia methodology, Section 3. Geographic Analysis and Research Unit,
Department of Housing and Urban Development. For landform element descriptions, refer to Appendix 1.
14.2 Analysis
Figure 14-1. Wetland landform elements.
Note: includes 15 sites from information sourced from previous studies (Lloyd and Balla (1986) and Barritt (1982).
Wetlands are ultimately defined by the surrounding landforms. On Kangaroo Island, lagoons were the most common landform surveyed (14 sites). Examples of these lagoons include Duck Lagoon and Grassdale Lagoon. Salt lakes were also represented in the survey,and included wetlands located in the salt lake district located south of Kingscote.
Landform Element
14
3 8 6 3
6
2
Lagoon Salt Lake Swamp
Closed depression Lake
Drainage depression Stream Channel
15.0 GEOLOGY 15.1 Background
The geological record on Kangaroo Island spans nearlly half of the Earth’s history. The oldest exposed rocks (Cambrian 570 million years) on the island occur on the Dudley Peninsula the eastern end of the island. The basic framework of Kangaroo Island was formed during the Cambrian-Ordovician (505 million years ago). The younger sediments since then have formed the island’s landscape. These sediments such as aeolianite dunes, spread across and along the south coast of Kanagroo Island altering the drainage flow from the higher central plataeu to the coast. This assisted in forming the lagoons and lakes in the southern section of Kangaroo Island, for example Murray Lagoon. Lunettes also formed during the late Pleistocene and are a unique feature on Kangaroo Island and good examples can be seen adjacent to White and Rush lagoons.
15.1 Analysis
Table 15-1. Geology underlying surveyed wetlands.
Geological description Number of wetlands surveyed
Bridgewater formation 12
Alluvial/fluvial sediments 12
Kanmantoo trough 6
Lacustrine playa sediments 2
Gibbers, sandstones and claystones 6
Carboniferous permain rocks 2
Note: includes 13 sites from information sourced from previous studies (Lloyd and Balla (1986) and Barritt (1982).
The Bridgewater formation is located along the southern coast line and forms the underlying geology for 12 wetlands surveyed. These wetlands include; Grassdale Lagoon, Salt Lake and Big White Lagoon. Alluvial and fluvial sediments are found within another 12 wetlands surveyed, including, Murrays Lagoon, Rush Lagoon, White Lagoon and Salt Lagoon.
Refer to Map 5 for locations of geological formations underlying the surveyed wetlands.
The lunette composed of wind
16.0 HYDROLOGY 16.1 Background
The Wetland Inventory documented the annual average rainfall for the wetlands surveyed and made observations on the main sources of water entering the wetland. Many of the wetlands are closed hydrological systems being fed by small drainage lines and run-off from the surrounding catchment, a good example of this is Six mile Lagoon.
16.2 Analysis
Table 16-1. Rainfall analysis
Rainfall bracket Number of wetlands
500 26
550 3
600 5
650 3
750 2
800 3
Note: includes 15 sites from information sourced from previous studies (Lloyd and Balla (1986) and Barritt (1982).
Rainfall fall on the high plateau on the western section of the island contrbutes to surface water run-off into the south-eastern surrounding catchments containing wetlands. Wetlands not located in the south-eastern section of the island rely on localized surface water run-off to maintain the hydrological cycle.
Plate 4. Six-mile Lagoon.
Six-mile lagoon is an excellent example of a wetland dependent upon surface water entering the wetland from the surrounding catchment.
17.0 FLORA ANALYSIS
A large proportion of the wetlands surveyed on Kangaroo Island are considered to be freshwater (<1500 µs). Aquatic and semi-aquatic flora was noticeably abundant in many water bodies, especially in freshwater (below 900 µs). Members from the genera Baumea, Blechnum, Carex, Gahnia and Juncus are common and form the understorey component of the vegetation structure surrounding these wetlands. Saline waterbodies recorded aquatic flora such as Samolus repens, Ruppia, Chara, Wilsonia and Myriophllum species. These genera were common within White lagoon, Rush Lagoon and Murray Lagoon.
Table 17-1. Vegetation associations at survey sites Dominant vegetation community adjacent to
wetland
Number of wetland sites
Melaleuca halmaturorum over introduced grasses 7
Melaleuca halmaturorum tall shrubland over Gahnia filum open sedgeland
3
Melaleuca halmaturorum tall shrubland overSclerostrgia arbuscula Tall open shrubland
8
Eucalyptus diversifolia, E.cosmophylla, +/- E. baxteri, +/- E.
fasciculosa +/- Melaleuca gibbosa over Gahnia sp. Open mallee.
1
Eucalyptus camaldulensis var. camaldulensis, E. leucoxylon ssp.leucoxylon over introduced grasses
2
Eucalyptus cladocalyx, E. diversifolia, +/- over Callistemon rugulosus +/- Juncus sp. woodland
1
Eucalyptus remota, E. cosmophylla, +/- E. baxteri over Acacia retinoides and Gahnia sp
1
Eucalyptus cosmophylla, E. baxteri over Leptospermum continentale, Acacia retinoides var. retinoides, Low woodland
2
Eucalyptus baxteri, E. obliqua, E. cosmophylla low woodland 1
Melaleuca gibbosa, M. brevifolia +/- Callistemon rugulosus Var.
rugulosus +/- Hakea rugosa shrubland
2
Eucalyptus cneorifolia, E. lansdowneana ssp. albopurpurea, E.
diversifolia, +/- E. cosmophylla Open mallee
1
Melaleuca brevifolia, M. gibbosa, +/- M. halmaturorum Shrubland 3
Eucalyptus cladocalyx, +/- E. obliqua, +/- E. baxteri, E.
cosmophylla Woodland
1
Eucalyptus cosmophylla, Eucalyptus fasciculosa, very open mallee +/- Melaleuca halmaturorum over cyperus sp
1
Leptospermum continentale, A. retinodes var. retinodes, E.
cosmophylla, E. baxteri Shrubland.
1
Note: includes eight sites from information sourced from previous studies (Lloyd and Balla (1986) and Barritt (1982).
Willougby et al (2001) state that vegetation associations containing Melaleuca
halmaturmorum, Melaleuca brevifolia and Melaleuca gibbosa are considered to be rare on Kangaroo Island. The association of Callstemon rugulosus var. rugulosus, +/- Melaleuca halmaturorum, +\- Hakea rugosa Tall closed shrubland is also considered to be rare on Kanagaroo Island.
The ecological role of Melaleuca halmaturmorum as a fringing saline wetland species is very important. Melaleuca halmaturmorum often forms an effective buffer for water bodies from increased sediment loads and nutrient concentrations. Greenway (1997) discusses some further direct benefits from Melaleuca halmaturorum these include:
Hydrological benefits
• Improved water quality by filtering suspended particles and by removing, recycling, or immobilising contaminants and nutrients, thereby preventing deterioration of downstream aquatic ecosystems (eg Cygnet River Lagoon).
• Provide a protective buffer zone between shorelines, estuaries and river systems protecting these waterways from siltation, nutrient run-off and erosion
• Provide flood mitigation by storing and detaining precipitation and run-off thus reducing flow rates and peak floods (eg Rush and White lagoons).
• Provide groundwater recharge and a water source for people and wildlife.
Ecological benefits
• Melaleuca trees are highly productive at recycling nutrients and function as long-term biomass sinks (eg Destree Swamp).
• During major flood events, particulate matter is washed into the rivers and estuaries to provide a food source for heterotrophic mirco-oranisms and detritivores (eg Lashmar Lagoon).
• Provide both temporary and permanent habitats for a variety of flora and fauna, including roosting and breeding areas for wildlife. Some Melaleuca swamps support large ibis and egret colonies.
• Provide vital refuges for wildlife during periods of drought.
• Melaleuca trees flower prolifically and provide a source of nectar for resident and migratory birds, bats, possums, bees and other insects. Their nectar is a particularly valuable food source for migratory honey-eaters and parrots during the autumn/winter months.
Threats
There are various key threatening processes which affect the majority of remnant Melaleuca halmaturorum woodlands on Kangaroo Island. These include increased nutrients moving into the water due to catchment clearance and farming practices, resulting in dieback and a change in water chemistry.
Plate 5. Halls Road Swamp
Plate 6. Destree Swamp
Plate 7. Cygnet River Lagoon
Halls Road Swamp has suffered from increased salinity levels and reduced frequency of freshwater flushing which has caused extensive dieback of the Melaleuca halmaturorum
Destree Swamp located on the Hundred Line Road is an excellent example of a functioning Melalueca swamp.
Cygnet River Lagoon plays an important role in filtering nutrients before water enters Cygnet River.
18.0 DEGRADATION AND DISTURBANCE 18.1 Background
Disturbances or threats are defined as any direct or indirect human activities at the site or in the catchment area that may have a detrimental effect on the ecological character of the wetland. The effect may be a low level disturbance (low level grazing) or a major threat such as water diversion schemes.
18.2 Analysis
Table 18-1. Land degradation
Degradation type Number of Occurrences
Access Tracks 13
Clearance 22
Grazing damage 14
Fence lines 5
Mining impact 1
Altered flows 3
Many wetlands contained disturbances; the two most frequent disturbances recorded are clearance (22 occurrences) and grazing damage (14 occurrences). Access tracks dissecting or traversing wetlands were also common (13 sites). A concern with many of these tracks is that they are usually formed with compressed soil and during high rainfall events, sediment often runs into adjacent wetlands. Other disturbances recorded include fences (5 sites) and altered water flows(3 sites) through stormwater inputs, banks, drainage and water extraction.
Other disturbances not recorded in this survey but documented by other observers, include the impacts from feral pigs (Sus scrofa) and populations of introduced freshwater crayfish, Yabbies (Cherax destructor) and Marron (Cherax tenuimanus) (Willoughby 2001).
Plate 8. Halls Road Swamp
An example of a common land degradation disturbance. Clearance is of a major concern and is affecting many wetland ecosystems on Kangaroo Island. Increased salinity levels through vegetation
clearance can destroy freshwater ecosystems.
19 AQUATIC VEGETATION CLASSES 19.1 Background
Parameters for seven classes of aquatic vegetation were included in the survey. These records can indicate the types of producers (production of oxygen and plant food) within the wetland system. The diversity of classes recorded may indicate the level of aquatic
biodiversity present, the vegetation classes consist of:
Algal and aquatic moss commonly comprise Charophyta (stoneworts) and Chlorophyta (green algae) which forms macroscopic mats either attached to plants or in open water.
Algae forms the photosynthetic basis for the open water food sources in many inland waters, (Boulton and Brock, 1999).
For images of green algae see: http://www.nmnh.si.edu/botany/projects/algae/Imag-Chl.htm.
Floating vascular/leaved plants have part or all of the leaves at the waters surface.
Examples include Azolla species floating ferns that host bacteria that fix nitrogen,
(Romanowski 1998), Lemna, Spirodela and Wolffia (duckweeds) and the genera Utricularia (bladderworts). Members from the family Potamogetonacea (pondweeds) are also common floating plants and can be found in a variety of habitats. All these plants are able to provide habitat for invertebrates, provide shelter for fishes and produce oxygen.
Rooted vascular plants are those rooted in the sediments with either a major proportion of material above water (reeds, rushes and sedges) or totally under water (Vallisneria spp.).
Many of these plants play a key role in nutrient cycling and provide habitat for birds, insects and aquatic invertebrates. Typical genera include Baumea, Bolboschoenus, Carex, Cyperus, Gahnia, Schoenus, Juncus, Triglochin and Myriophyllum. Myriophyllum is a distinctive
wetland genus that provides food, shelter and spawning or nesting sites for a variety of animals, from invertebrates to fish, frogs and birds (Romanowski, 1998).
19.2 Analysis
Figure 19-1. Aquatic vegetation types
Note: includes eight sites from information sourced from previous studies (Lloyd and Balla (1986) and Barritt (1982).
Rooted vascular plants are the most common form of vegetation class within the surveyed wetlands. Genera such as Juncus, Carex, Cyprus and Gahnia were frequently recorded in freshwater wetlands (29 sites, eg Grassdale Lagoon). Saline wetlands commonly recorded
Aquatic vegetation classes
3
29 5
1
Floating Leaved Rooted vascular Algae
Moss
Plate 9. Rush Lagoon
Plate 10. Grassdale Lagoon
Plate 11. Discovery lagoon
The distinct bands of floating
vegetation can be seen in the center of the photo.
Grassdale lagoon has a diversity of all aquatic classes. Pictured are dense stands of Juncus.
Discovery Lagoon recorded a high abundance and diversity of submerged aquatic flora, including Chara and Myriophyllum spp.
20 AQUATIC FAUNA ANALYSIS 20.1 Invertebrates
Macro and micro invertebrates are an essential component of the wetland food web. They are responsible for a significant proportion of the secondary production occurring in wetlands, and form two interconnected wetland food chains, a grazing food chain and a detrital food chain. Invertebrates comprise much of the diet of waterfowl populations the diversity and abundance of waterfowl can be a direct consequence of the invertebrate food supply.
20.1.1 Ecological benefits
Yen and Butcher (1997) provide some examples of direct ecological benefits that invertebrates contribute:
Tangible direct benefits:
1. Plant pollination
2. Effects on soil; soil formation and fertility.
3. Decomposition; fragmentation and recycling of dead plant and animal material.
4. Position in the food web; invertebrates are the principle food for many vertebrates.
5. Preditation and parasitism. Invertebrates are involved in the natural regulation of
populations of other species through predation and parasitism, and thus form the basis of biological control.
Indirect ecological benefits:
1. Ecosystem stability: the loss of species from highly interrelated systems is likely to cause a cascade of further extinction losses.
2. Evolutionary time: the diversity within ecosystems over time maintains diversity.
20.1.2 Trophic dynamics
Standing water communities are dynamic systems which reflect change in many variables.
The trophic state of a wetland depends on nutrient inputs from the catchment and within the wetland (Boulton and Brock 1999). Invertebrates were collected during the Wetland Inventory and classified according to trophic levels. If samples from all trophic groups are collected, this could suggest that the aquatic ecosystem is in a reasonable state of equilibrium. The top of the food chain is occupied by vertebrate predators, including fish, water rats and water birds. These terrestrial predators can be considered to be on the top of the aquatic food chain, and provide a pathway for the export of nutrients and other material from the wetland ecosystem (Boulton and Brock,1999). These trophic levels are described below.
Primary producers
Primary producers form two groups, those that are suspended or floating and those attached to substrate or other plants. Attached macrophytes includes fringing reeds and submerged plants and periphyton (the biota attached to submerged surfaces). Suspended or floating forms generally consist of the phytoplankton and algae groups. Phytoplankton form the basic photosynthetic basis for the open water food web in most standing waters.
Consumers
There are two main types of consumers based on diet: grazers that consume plants and predators that consume other animals.
Grazers
Grazers consist of aquatic snails (Gastropoda) and some mayfly nymphs (Ephemeroptera), caddisfly larvae (Trichoptera) and beetles (Coleoptera). These groups are usually found near the edges of the water body.
Within the open water, some of the important grazers are zooplankton, including water fleas (Cladocera) and copepods (Calanoida and Cyclopoida).
Vertebrate Grazers
Vertebrate grazers generally consist of groups such as tadpoles, fish and waterbirds.
Vertebrate grazers can influence the food web considerably when attracted to water bodies in times of flood or in types of drought.
Predators
Predators include dragonfly larvae (Odonata) which tend to ambush prey and invertebrates that hunt in open water such as diving beetles (Dytiscidae, Coleoptera) (Boulton and Brock 1999). Areas such as the littoral zone tend to have high biodiversity of grazers which in turn attracts many invertebrate predators.
20.2 Temporary Wetlands
Many of the wetlands on Kangaroo Island are temporary and display slightly different invertebrate fauna composition from other wetland systems such as saline lakes or permanent waters. Williams (2000) makes four general conclusions from his study of temporary wetlands, these are:
1. Faunal diversity is high and often higher than in many permanent wetlands.
2. A wide range of fauna groups occurs with the particular assemblage depending largely upon time from filling. Many species are restricted to temporary wetlands, for example all notostracan, conchostracan and anostracan species are restricted to temporary
wetlands.
3. Local differences in hydrology, filling frequency, basin shape and other factors often result in differences between wetlands in the same area and same time.
4. Considerable continental and regional endemism prevails. Most macofaunal species are endemic to Australia.
The filling or flooding of temporary water bodies releases a pulse of nutrients that, together with light and water, provide the resources for germination and growth of both micro and macro photosynthesizers. Habitat for consumers and decomposers soon follows. The invertebrate sediment egg bank with desiccation-resistant stages seems to be the initial source of colonists. The groups that tend to be first in temporary waters include rotifers, ostacods, copepods and cladocerans. When the water body starts to dry a ‘predator soup’
results, and terrestrial predators (eg birds) come to the water to feed during the drying process. This process forms a critical trophic link between aquatic and terrestrial systems (Boulton and Brock 1999).
20.3 Saline Systems
Large areas of Kangaroo Island contain saline wetlands, those surveyed include:
• Lashmar Lagoon • Milky’s Lake
• Greenfields Wetland • Rush Lagoon
• Big White Salt Lagoon • White Lagoon 1
• Discovery Lagoon • Salt Lagoon
• Salt Lake • Halls Road Swamp
• Wangara Lagoon • Emanual Lagoon
• Destree Swamp • White Lagoon
• Murray Lagoon • Birchmore Lagoon
• Chapman River • Nepean Bay Lagoon
• Salt Lake 2
Freshwater organisms in Australia generally tolerate salinities up to about 3 gL (3000 EC), beyond this there is a change in community composition, with decreased richness and increased abundance (Williams,1998); Skinner et al 2001). The biological process in salt lakes can resemble those of fresh water bodies despite the differences in physical, chemical and biological attributes (Boulton and Brock1999). The beds of many salt lakes are covered by benthic microbial mats dominated by photosynthetic producers, and lake crusts contain propagules of decomposers, producers and consumers. Boulton and Brock (999), comment that little is known about the microbial loop in salt lakes.
A high diversity of invertebrates can occur within salt lakes, examples include rotifers, anostracan, cladocerans, calanoid copepods and ostracods. Fish are usually absent from saline lake systems and the top consumers are mostly water birds.
In general, invertebrate species richness in salt lakes declines with increasing salinity, but at intermediate salinities where many species tolerances are broad, other factors such as biological interactions and pH will affect community composition (Skinner et al 2001,
Williams, 2000). Studies by Skinner et al (2001) indicates that salinization shifts invertebrate community structure and algae tends to also become dominant at the higher salinity levels.
This could lead to insufficient food for animals higher in the trophic level, including fish and waterfowl.
20.4 Analysis
Analysis of invertebrates is discussed in four areas:
1. frequency of invertebrate occurrence 2. trophic levels
3. number of invertebrate records for each surveyed wetland 4. invertebrate lists for each wetland tabled in Appendix 2.
20.4.1 Frequency of invertebrate occurrence
Table 20-1 lists the invertebrate species identified from collections made during the Wetland Inventory in December 2000, with the frequency of occurrence given against each identified invertebrate. A total of 80 species are recorded, with 37 species recorded once and 43
Plate 12. Diacypris cf.spinosa.
Plate 13. Dicrotendipes sp.
Plate 14. Tricoplera oecetis.
The genera Diacypris (recorded 13 times) belongs to the subclass Ostracoda, of which there are 11 families and 37 genera.
Ostracods are generally found in most habitats Australia-wide.
Five occurrences of Dicrotendipes sp. were recorded.
Two occurrences of Tricoplera oecetis (caddis fly) were recorded. Note the protective case surrounding the larvae.
Table 20-1. Frequency of invertebrate species occurrence
Identified invertebrates Frequency of occurrence
Ablabesmyia sp 1
Aeshnia brevistyia 1
Agraptocorixa sp 3
Alboa worooa 6
Alona sp 2
Anisops sp 8
Apocyclops annulosus 2
Australocyclops australis 5
Australocyclops similis 2
Australocyclops sp 1
Austrochiltonia australis 10
Austrolestes annulosa 2
Austrolestes cingulatus 2
Austrolestes leda 1
Austrolestes sp 2
Berosus sp. 2
Boeckella sp 2
Boeckella symmetrica 7
Boeckella triarticulata 2
Calamoecia ampulla 5
Calamoecia australis 1
Calamoecia clittelata 3
Calamoecia salina 4
Candonocypris sp 2
Ceriodaphnia sp 1
Chironominus sp 6
Cladotanytarsus sp 1
Chostonectes sp 1
Cloeon sp 1
Cnephia sp 1
Culex sp 2
Cypricercus sp 1
Daphnia cf carinata 1
Daphnia sp 1
Daphniopsis sp 2
Diacyclops bisetosus 1
Diacypris spinosa 13
Dicrotendipes sp 5
Dunhevedia crassa 2
Enithares sp 4
Enithares woodwardi 2
Eucyclops sp 1
Eucyclops cf baylyi 1
Fluvidona sp 1
Gomphodella sp 1
Haloniscus searli 1
Hemianax papuensis 1
Hesperocordula sp 1
Ilyocryptus sp 2
Kennethia sp 2
Keratella sp. 1
Limnocythere porhyretica 1
Macrothrix sp 9
Macrocyclops sp 1
Mesocyclops sp. 12
Metacyclops mortoni 6
Miconecta sp 8
Mixocyclops sp 2
Mytilocypris tasmanica 1
Mytilocypris ambiguosa 4
Necterosoma sp 1
Neocyclops petkovis 1
Newnhamia fenestrata 2
Notalina sp 1
Odontomyia sp 1
Oxythira cf columba 1
Paracyclops sp 1
Parachironomus sp 1
Parartemia zeitziana 7
Paraterina 1
Paratanytarsus sp 1
Plea sp 1
Procladius sp 5
Sigara sp 2
Simocephalus cf expinosus 1
Simocephalus elizabethae 2
Simocephalus sp. 3
20.4.2 Trophic levels
Invertebrate composition analysis is affected by the study of trophic levels present in each wetland. Conclusions made about the ecosystem health of a wetland based on the
invertebrates could not be made due to the limited sample size, and can only provide an indication at the time of the sampling.
Invertebrate scoring method
Invertebrate scores were assigned for each wetland, each sample was identified to family level and the trophic level of each family recorded. From the samples identified the diversity and abundance was recorded and the following scoring system has developed.
Score 1 = (Low) sampled one family from one trophic level, usually from a lower level trophic level, (eg detritivores and herbivores).
Score 3 = (Moderate) sampled more than one family with representatives from one or more trophic levels, (eg herbivores and carnivores).
Score 5 = (High) sampled more than two families with representatives from three or more trophic levels, (eg detritivores, herbivores, omnivores and carnivores).
Figure 20-1. Invertebrate scores.
Fourteen wetlands scored 5, seven scored 3 and two wetlands scored 1.
Trophic scores
14 7
2
Score 5 Score 3 Score 1
