WETLAND INVENTORY EYRE PENINSULA
An assessment of selected inland wetlands for Eyre Peninsula, South Australia.
This report may be cited as:
Seaman, R.L. (2002) Wetland Inventory for Eyre Peninsula, South Australia.
Department for Environment and Heritage.
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 Support Organisation 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
Executive Summary
The Wetland Inventory of Eyre Peninsula documents a representative sample of inland wetlands by recording their physical, chemical and biological attributes. Twenty-seven wetlands were surveyed, the majority of these comprised saline lake systems and brackish water bodies, with only one freshwater wetland being recorded during the survey.
The aquatic invertebrate fauna was notably scarce in many of the wetlands surveyed. This may be attributed to the high conductivity readings in the majority of wetlands, only four wetlands displayed good invertebrate diversity. The correlation between increasing salinity levels and decreasing biological activity was clear, and this decline is of concern for the health of many wetlands.
Several wetlands surveyed are considered to be nationally important as they meet the ANZECC criteria of being a good example of a wetland type occurring within a biogeographic region in Australia. These wetlands include the saline lake systems within Lincoln National Park and Lake Newland Conservation Park. Seven wetlands are recommended for monitoring, and include four wetlands in the District Council of Elliston and three wetlands managed by National Parks and Wildlife.
SECTION ONE - WETLAND INVENTORY ... 8
1.0 INTRODUCTION... 8
2.0 REPORT STRUCTURE ... 8
3.0 PROJECT SCOPE... 8
4.0 OVERVIEW OF WETLAND INVENTORY TRENDS... 9
5.0 WETLAND RISK ASSESSMENT... 10
5.1 ECOLOGICAL CHARACTER... 10
6.0 WETLAND INVENTORY METHODOLOGY ... 10
6.1 STUDY AREA BOUNDARIES... 10
6.2 SITE SELECTION... 10
6.3 GIS DATABASE... 11
6.4 WETLAND INVENTORY SURVEY... 11
6.5 WETLAND SURVEY TEMPLATE... 12
SECTION TWO - WETLAND ASSESSMENT FOR EYRE PENINSULA ... 13
7.0 INTRODUCTION... 13
8.0 EYRE PENINSULA... 13
8.1 WETLAND OVERVIEW... 13
9.0 WETLAND LAND USE... 14
9.1 BACKGROUND... 14
9.2 ANALYSIS... 14
10.0 TENURE AND MANAGEMENT AUTHORITY ... 15
10.1 BACKGROUND... 15
10.2 ANALYSIS... 15
11.0 ENVIRONMENTAL REGIONS ... 15
11.1 BACKGROUND... 15
11.2 ANALYSIS... 16
12.0 KEY BIODIVERSITY AREAS... 16
12.1 BACKGROUND... 16
12.1.1 Large remnant areas ... 16
12.1.2 Threatened Habitat Areas ... 17
12.2 ANALYSIS... 17
13.0 WETLAND AREA ... 18
13.1 BACKGROUND... 18
13.2 ANALYSIS... 18
14.0 LANDFORM ELEMENT ... 19
14.1 BACKGROUND... 19
14.2 ANALYSIS... 19
17.1 BACKGROUND AND ANALYSIS... 21
18.0 DEGRADATION AND DISTURBANCE ... 24
18.1 BACKGROUND... 24
18.2 ANALYSIS... 24
19.0 AQUATIC VEGETATION CLASSES ... 25
19.1 BACKGROUND... 25
19.2 ANALYSIS... 25
20.0 AQUATIC INVERTEBRATE ANALYSIS ... 26
20.1 BACKGROUND... 26
20.1.1 Ecological benefits ... 26
20.1.2 Trophic dynamics ... 26
20.2 SALT LAKE SYSTEMS... 27
20.4 ANALYSIS... 28
20.4.1 Invertebrate abundance ... 28
20.4.2 Invertebrate diversity ... 30
21.0 WATER CHEMISTRY... 32
21.1 PH ... 33
21.1.1 Background ... 33
21.1.2 Analysis ... 34
21.2 CONDUCTIVITY... 34
21.2.1 Analysis ... 35
21.3 TURBIDITY... 38
21.3.1 Analysis ... 38
21.4 WATER TEMPERATURE... 40
24.4.1 Analysis ... 41
22.0 RAPID ASSESSMENT ... 41
22.1 AQUATIC FAUNA... 41
22.2 AQUATIC FLORA... 42
23.0 RIPARIAN VEGETATION RAPID ASSESSMENT ... 42
24.0 WETLAND CONDITION SCORE ... 42
25.0 RAPID ASSESSMENT TOTAL SCORE ... 43
25.1 WETLANDS WITH HIGH VALUES... 43
25.2 MODERATE WETLAND VALUES... 43
25.3 LOW WETLAND VALUES... 44
26.0 ANZECC WETLAND CRITERIA ... 44
26.1 ANALYSIS... 45
27.0 WETLAND TYPES... 46
SECTION THREE - WETLAND MONITORING ... 49
28.0 INTRODUCTION... 49
28.1 ECOLOGICAL CHANGE... 49
29.0 MONITORING PROTOCOLS AND INDICATORS... 51
29.1 EARLY WARNING INDICATORS... 52
29.1.1 Toxicity tests... 52
29.1.2 Field early warning indicators... 52
29.1.3 Rapid Assessments... 52
30.0 RECOMMENDED INDICATORS FOR MONITORING SURVEYED WETLANDS ... 53
31.0 RECOMMENDED WETLANDS TO MONITOR... 54
31.1 RECOMMENDED PRIORITY WETLANDS... 55
31.2 SECOND PRIORITY WETLANDS... 55
32.0 RECORDING MONITORING PARAMETERS ... 55
BIBLIOGRAPHY... 57
APPENDIX 1 WETLAND INVENTORY DESCRIPTIONS ... 60
Figures FIGURE 1. ON SITE WETLAND LAND USES ... 14
FIGURE 2. TENURE AND MANAGEMENT ... 15
FIGURE 3. WETLANDS WITHIN ENVIRONMENTAL REGIONS... 16
FIGURE 4. WETLANDS WITHIN KEY BIODIVERSITY AREAS... 18
FIGURE 5. WETLAND AREA. ... 18
FIGURE 6. WETLAND LANDFORM ELEMENTS. ... 19
FIGURE 7. GEOLOGICAL STRUCTURE UNDERLYING WETLANDS... 20
FIGURE 8. WETLAND DISTURBANCE ... 24
FIGURE 9. AQUATIC VEGETATION CLASSES... 25
FIGURE 10. INVERTEBRATE DIVERSITY BY WETLAND SITE. ... 30
FIGURE 11. TEMPORARY WETLAND CYCLES... 32
FIGURE 12. PH VALUES ... 33
FIGURE 13. WETLAND PH VALUES FOR SURVEYED SITES ON EYRE PENINSULA... 34
FIGURE 14. SALINITY GUIDELINES... 36
FIGURE 15. FISH ACTIVITY AGAINST TURBIDITY VALUES AND TIME... 39
FIGURE 16. AQUATIC FAUNA RAPID ASSESSMENT ... 41
FIGURE 17. ANZECC CRITERIA. ... 45
FIGURE 18. WETLAND TYPE... 47
TABLES TABLE 1. INVERTEBRATE ABUNDANCE ... 29
TABLE 2. TURBIDITY GUIDELINES. ... 40
TABLE 3. RIPARIAN VEGETATION RAPID ASSESSMENT... 42
TABLE 4. WETLANDS WITH HIGH RAPID ASSESSMENT SCORES. ... 43
TABLE 5. WETLAND WITH MODERATE RAPID ASSESSMENT VALUES. ... 43
TABLE 6. WETLANDS WITH LOW RAPID ASSESSMENT VALUES. ... 44
TABLE 7. WETLANDS WITH ANZECC CRITERIA... 45
TABLE 8. WETLAND TYPES. ... 48
TABLE 9. RECOMMENDED PRIORITY WETLANDS FOR MONITORING. ... 55
TABLE 10. SECOND PRIORITY WETLANDS TO MONITOR. ... 55
PLATES
PLATE 1. MELALEUCA HALMATURORUM TALL SHRUBLAND OVER HALOSARCIA SP... 22
PLATE 2. MELALEUCA HALMATURORUM... 23
PLATE 3. INTRODUCED GRASSES ... 23
PLATE 4. GAHNIA SP. ... 23
PLATE 5. FLINDERS HIGHWAY... 24
PLATE 6. DIACYPRIS CF. SPINOSA PLATE 7. DAPHNIOPSIS PUSILLA ... 29
PLATE 8. OLD PLOUGH SWAMP PLATE 9. BIG SWAMP ... 31
PLATE 11. MIDDLE LAKE PLATE 12. LAKE TUNKETTA ... 31
PLATE 12. HAMP LAKE PLATE 13. TADDIE POOL... 37
PLATE 14. MEADOW POOL PLATE 15. SAMPHIRE FLAT ... 37
Maps
Map 1. Natural Heritage Trust Boundary for Eyre Peninsula Map 2. Wetland survey localities
Map 3. Key Biodiversity Areas
Map 4. Geology underlying wetlands on Eyre Peninsula
SECTION ONE WETLAND INVENTORY 1.0 INTRODUCTION
Eyre Peninsula contains unique and significant inland wetlands, the majority of which are saline lake systems with characteristic tea-trees forming circular bands around them. In spite of the high salinities, these lake systems contain excellent biodiversity values within the aquatic zone and adjacent terrestrial vegetation. This wetland inventory documents a representative sample of inland wetlands and records the physical, chemical and biological attributes of each waterbody. From this information, aquatic environments that contain high biodiversity are highlighted and threats affecting them documented. The inventory
provides a snap shot of the condition and conservation value of wetlands on Eyre Peninsula. 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 database and inventory project is an initiative of the South Australian Department for Environment and Heritage, Conservation Strategies Section with support from Environment Australia, National Wetlands Program.
2.0 REPORT STRUCTURE
This report is divided into three sections, namely the wetland inventory, wetland assessment and wetland monitoring.
Section 1 - Wetland Inventory. Outlines the project aims, wetland risk assessment methodology 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 wetlands to monitor.
3.0 PROJECT SCOPE
The project scope consist of seven actions, these are to:
• Undertake wetland baseline surveys for the inland waters of Eyre Peninsula.
• Identify wetlands from surveys of conservation significance, according to ANZECC classification.
• Identify gaps in the data and prioritise the need for further surveys.
• Develop a South Australian wetland management database, format fields to be compatible with the Directory of Important Wetlands in Australia, and to allow for inclusion of data in the Directory and the Wetlands Inventory of Australia.
• Provide digital coverage of spatial boundaries of identified wetlands in ARC/INFO compatible format at appropriate scale, in consultation with Planning SA.
4.0 OVERVIEW OF WETLAND INVENTORY TRENDS
The most comprehensive listing of wetlands in South Australia in terms of numbers and coverage is by Lloyd and Balla (1986). This study identified about 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.
This report does provide a good starting point in understanding the extent and some attributes of South Australian wetlands. The study does however fall short in providing up to date information on invertebrate composition, water chemistry and basic landform information. The wetlands listed in Lloyd and Balla formed the basis for site selection in undertaking baseline surveys for this current study.
Since Lloyd and Balla’s 1986 report, several studies have mirrored this kind of information and presentation of wetland information, but has not been collected within a standard format. However, good information has been generated for certain areas including the Murray River corridor. Thompson’s (1986) study of River Murray Wetlands and Jensen et al (1996) Wetland Atlas report of the South Australian Murray Valley Wetlands made inroads into spatially capturing wetland locations through the use if GIS. The introduction of linking wetlands with GIS enabled the creation of a wetlands GIS database for the Murray Valley Wetlands.
In 1997 a GIS database was also created for the South East wetlands. This database recorded wetland type, name, complex, watercourses and assigned a condition score and conservation value, Carruthers and Hille (1997). The benefits of collecting data and linking it to GIS became evident not only for environmental planning and 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. Information was collected and put into a format which provided, for the first time, a detailed assessment of selected wetlands in South Australia.
It became apparent, that several regions within South Australia were lacking baseline wetland information.
De Jong and Morelli (1996) suggested that there is a need for systematic inventories, biological surveys and research programs in many areas of the State. Wetland information in regions such as the Great Victoria Desert, Flinders and Olary Ranges, Eyre Peninsula, Yorke Peninsula, Kangaroo Island and Nullarbor is inadequate.
This project combines some of these key developments and recommendations, namely developing a GIS database and providing baseline information for nominated regions.
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 processes 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 develop monitoring programs.
5.1 Ecological Character
A central component of the wetland risk assessment is the ability to record the ecological character of a wetland. The first process comprises of the collection of information, the wetland inventory.
Ecological character is the sum of the biological, physical, and chemical components of the wetland ecosystem and their interactions that maintain the wetland and its products, functions, and attributes.
Change in ecological character is the impairment or imbalance in any biological, physical, or chemical components of the wetland ecosystem, or in their interactions.
Van Dam et al (1999) outline five main causes of adverse change, namely:
1. changes to the water regime 2. water pollution
3. physical modification
4. exploitation of biological products 5. introduction of exotic species.
6.0 WETLAND INVENTORY METHODOLOGY
This section describes the approach and information collected for the wetland inventory. A wetland inventory can be defined as the collection of core information for wetland management, including the provision of an information base for specific assessment and monitoring activities (Finlayson and Eliot, 2001). Costa et al (1996) also suggests that inventories have the attributes of set objectives over a given time-period with the aim of publishing and disseminating the information and making it available within a database.
6.1 Study area boundaries
The project boundary is defined by the Natural Heritage Trust administration boundaries for Eyre Peninsula.
Refer to Map 1.
6.2 Site selection
The aim of the wetland selection process is to sample a broad range of wetlands within each region and where access was relatively simple. Factors such as time constraints and project budget was also a limiting
6.3 GIS Database
This project builds on initiatives undertaken by Planning SA and the Department for Environment and Heritage. GIS databases are developed for the Murray River region 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 published in the form of a technical report (Carruthers and Hille 1997). One of the project scopes for this project is to provide a digital coverage of spatial boundaries of identified wetlands. This will provide a GIS database for Eyre Peninsula, Mount Lofty Ranges, Northern Agricultural Districts and Kangaroo Island. Gaps in coverage will occur simply due to project constraints, and it is suggested that these gaps be filled at a later stage.
A State-wide numbering system was developed for identifying wetlands which follows the system
established for the Murray wetlands. The Murray region wetlands have been assigned the numbers S0001 to S0999. The South East region wetlands have been assigned the numbers S1000 to S1999, Northern Agricultural Districts S4000 to S4999, Kangaroo Island S5000 to S5999 and the Mount Lofty Ranges S2000 S2999. Eyre Peninsula is assigned numbers S3000 to S3999.
The system 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 (Carruthers and Hille 1997).
6.4 Wetland inventory survey
In developing the wetland survey it was critical that information relevant to the wetland risk assessment framework was incorporated. This ultimately involves the collection of physical, biological and chemical parameters. Several survey methodologies were studied and incorporated; these included:
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. & Napier (1998) Environmental indicators for national state of the environment reporting - inland waters. Environment Australia
Ø Maher W & 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 & 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.
6.5 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
• Ramsar Site
• Land Use
• Land Element
• Wetland Name
• Description of Site
• Tenure
• Geology
Biological parameters
• Vegetation Associations
• Biological Threats
• Noteworthy Flora and Fauna
• Aquatic Vegetation Classes
Chemical parameters
• Dissolved Oxygen
• Conductivity
• Turbidity
• pH
• Temperature
SECTION TWO WETLAND ASSESSMENT FOR EYRE PENINSULA 7.0 INTRODUCTION
Wetland assessment involves the identification of the status of and threats to wetlands as a basis for the collection of more specific information through monitoring activities. In essence, Section Two of this report analyses the survey results by looking at each relevant survey parameter individually. This comprises a background discussion, analysis and discussion of results.
8.0 EYRE PENINSULA 8.1 Wetland overview
Eyre Peninsula contains excellent examples of inland saline lake systems found within South Australia.
These wetland systems are confined mainly to the south-west of the Peninsula. There are also several areas with good quality coastal wetland systems consisting of mangroves and samphire flats; these are located within the numerous bays and tidial inlets around the Peninsula. The eastern portion of Eyre Peninsula contains many degraded saline lake systems and the occasional freshwater wetland. These remaining freshwater wetlands are quickly becoming saline due to the effects of dryland salinity. Threats to deteriorating water quality in wetlands include vegetation clearance contributing to increased salinisation, livestock grazing, introduced plants and animals, altered water regimes and introduction of industries dependant upon irrigation are affecting wetland areas on Eyre Peninsula.
There are several inland wetland areas on Eyre Peninsula that are listed in the Directory of important wetland for South Australia. These include Big Swamp, Little Swamp, Sleaford Mere, Lake Newland and Lake Hamilton.
A total of 27 wetlands were surveyed. Some are conserved within the South Australian reserve system, including Lake Newland in Lake Newland Conservation Park and Sleaford Mere and Pillie Lake within Lincoln National Park. Other wetland areas protected in the reserve system but not covered by the survey include Coffin Bay Conservation Park and Calpatanna Waterhole Conservation Park.
Refer to Map 2 for wetland survey localities.
9.0 WETLAND LAND USE 9.1 Background
On site and surrounding land uses can have major impacts on wetlands. The most common land uses on Eyre Peninsula include cropping and grazing. Land used for cropping can lead to bank erosion, depleted soil structure and loss of nutrients. Dryland salinity is significantly increased in areas where deep-rooted vegetation has been replaced by annual crops. Grazing by domestic stock affects wetlands by removing vegetation, breaking up of the soil surface, distributing weed species and increasing organic nutrients through faecal deposits. Land set-aside for conservation purposes either through the reserve system or on- farm conservation have the least impact but currently comprise the minority of wetland land uses.
9.2 Analysis
Figure 1. On site wetland land uses
Twenty-one occurrences of cropping and grazing were recorded as the main land uses within or adjacent to wetlands surveyed on Eyre Peninsula. Land uses for four wetlands were classified as unknown. These are areas that have been rested from primary industry or are roadsides or lands with no clear land use
allocation. Wetlands located within NPWSA reserves were sufficiently protected from deleterious surrounding land uses.
Wetland land uses on site
0 5 10 15 20 25
Land uses
Occurrences of wetlands
Series1 21 4 3 4 1
Cropping/Grazing Local government reserve
Conservation/Nation
al Park Unknown Reservoir
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 parameter also allows consideration of different legislation and approaches concerning on-site management and planning for wetland areas.
Figure 2. Tenure and management 10.2 Analysis
Private tenure and management was the most common occurrence with 20 sites recorded. This suggests that the management of wetlands surveyed on Eyre Peninsula lies with private landholders. This factor has implications for the management of wetlands for biodiversity, and highlights the importance of off reserve conservation programs.
11.0 ENVIRONMENTAL REGIONS 11.1 Background
Laut et al (1977) described and mapped South Australia hierarchically into Environmental Provinces, Environmental Regions and Environmental Associations. The three tiers are based on geological formations and vegetation type. Eyre Peninsula is part of the Eyre and Yorke Peninsula Province. This province is divided into six Environmental Regions, which are based on vegetation criteria. The wetland survey is contained within three of these regions.
The Southern Highlands and Plains Environmental Region encompasses the southern section of the uplands of the Koppio Hills and along the east coast of Eyre Peninsula, and the undulating to low hilly plains to the west. The western boundary represents a change from duplex soils on the hilly or undulating country to sands and calcarenite plains, the north is defined by inland dune landforms (Laut et al 1977).
The West Coast Environmental Region is comprised predominantly of undulating to hilly plains on calcarenite with local rises and the occasional steep-sided hills on quartzite on the west side of Eyre
Peninsula. Dunes are restricted to the coastal fringe where they occur in association with lagoons and lakes (Laut et al 1977).
Tenure and management
0 5 10 15 20 25
Occurrence of wetlands
Type
Type 20 4 5 4
Private Local
government
State
government No data
The Central Mallee Plains and Dunes and Environmental Region extends across Eyre Peninsula from its western extremity to Spencer Gulf. It is distinguished climatically by being more arid than regions to the south, and this is reflected in the vegetation. The northern margin is formed by the dunefields of the Great Victoria Desert and the eastern margin by the Gawler Ranges. The region is essentially an undulating plain with an extensive cover of dunes and sand sheets (Laut et al 1977).
11.2 Analysis
Figure 3. Wetlands within environmental regions
The West Coast and the Southern highlands and plains regions contained most of the wetlands surveyed.
This suggests that more wetlands occur in these regions, which correspond to the geological characteristics of limestone or highland wetland formations.
12.0 KEY BIODIVERSITY AREAS 12.1 Background
Key Biodiversity Areas are used to define areas of high biodiversity on Eyre Peninsula. The ability of overlying wetlands surveyed within Key Biodiversity Areas assists in highlighting wetlands located in environmental significant areas. Two key biodiversity areas are identified in the Biodiversity Plan for Eyre Peninsula (Matthews, 2001). These are large remnant areas and threatened habitat areas which have been developed by combining the biological assets of Eyre Peninsula. Refer to Map 3 for Key Biodiversity Areas.
12.1.1 Large remnant areas
These areas have been identified on the basis that they contain large blocks of vegetation, good linkages, species diversity and populations of species with high conservation significance. Two large remnant areas have been identified on Eyre Peninsula, the ‘Central North-West linkage’ and the ‘Jussieu Peninsula to Coffin Bay Peninsula’.
Environmental Regions
0 2 4 6 8 10 12 14 16 18
Occurrence of wetlands
Region 17 14 2
W est coast Southern highlands
and plains
Central mallee plains and dunes
Bay, Sleaford Mere and Kathai Conservation Parks and a number of Heritage Agreements (Matthews 2001).
12.1.2 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
• poorly conserved within reserve systems
• fragmented and contain regionally threatened plant communities
• contain large numbers of species of high conservation significance.
Five Threatened Habitat Areas have been identified on Eyre Peninsula. These are Koppio Hills, Cleve Hills, South-west, Sheoak Grassy Woodlands and the Far West Threatened Habitat Areas (Matthews 2001).
Koppio Hills Threatened Habitat Area contains small scattered remnants of highly significant vegetation communities such as the regionally threatened community of E. camaldulensis woodland (river red gum).
The Koppio Hills cover an area of approximately 96,000 hectares with a total area of native vegetation of 18,000 hectares (Matthews 2001).
Cleve Hills Threatened Habitat Area has been identified as a Threatened Habitat Area due to a number of threatened and endemic species. The boundary of this area has been made on the southern and eastern boundary at approximately 200m above sea level (Matthews 2001).
South-West Threatened Habitat Area has been identified due to a number of significant biological features of this area. This area includes the plains to the south-east of Lake Hamilton, and includes the large areas of salt lakes including Lakes Malata and Greenly. The South-West Threatened Habitat Area comprises 172,000 hectares with a total of 25,000 hectares of native vegetation.
Sheoak Grassy Woodlands Threatened Habitat Area contains scattered sheoak populations, Allocasuarina verticillata and temperate native grasslands and grassy woodlands. Sheoak Grassy Woodlands comprises an area of 123,000 hectares with 27,000 hectares of native vegetation.
Far West Threatened Habitat Area has been identified due to a number of significant biological features of this area. This area contains several vegetation communities that have been identified as being rare or threatened. Unlike the other Threatened Habitat Areas the Far West extends down to the coast and incorporates high biodiversity coastal areas. Areas such as Tourville Bay contains mangroves and salt marshes for wading birds and other wetland species (Matthews 2001).
12.2 Analysis
K e y B io d iv e rs ity A re a
4 6 8 1 0 1 2 1 4
Occurrence of wetlands
Figure 4. Wetlands within Key Biodiversity Areas.
The grouping of Threatened Habitat Areas has the highest wetland occurrence, especially within the
subgroup of Sheoak Grassy Woodlands (13 sites). This is understandable due to the characteristic calcrete sheets formations which have formed wetland areas in weathered or cracked calcrete sheets. The South- West Threatened Habitat Area contains wetlands such as Lake Hamilton and Lakes Malata and Greenly.
Again, geological formations (dune and calcrete) have dictated much of the distribution of wetlands in this area. Several wetland sites are located within the Large Remnant Area of the Central-Northwest Linkage, these wetlands are mostly located within Lincoln National Park and Coffin Bay National Park.
13.0 WETLAND AREA 13.1 Background
The area of wetlands was calculated by using ArcView GIS based on ISB/GAR Landcover – 1991 Photography, River/Lakes Layer 2000, Evaporation Basins 2000.
13.2 Analysis
Figure 5. Wetland Area.
The total wetland area for Eyre Peninsula is approximately 64,000 hectares with a mean of 21 hectares and a maximum of 3,170 hectares. With only 13,000 hectares having baseline data, the opportunity exists for the other 51,000 hectares to be mapped and baseline data attributed to these wetlands.
Wetlands over 300 hectares in size include Sleaford Mere (707 ha), lake Hamilton (1,900 ha) and Lake Greenly (2,629 ha).
0 2 4 6 8 10 12
Wetland Area (Hectares)
Occurrence 11 6 6 2 6
0-50 51-100 101-200 201-300 over 300 Ha
14.0 LANDFORM ELEMENT 14.1 Background
Landform element definitions have 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.
14.2 Analysis
Figure 6. Wetland landform elements.
Salt lakes were the most common wetland sampled. Salt lakes are defined as lakes that contain a concentration of mineral salts (predominantly sodium chloride in solution as well as magnesium and
calcium sulphate). Swamps were the next most common wetland landform with seven occurrences (eg Old Plough Swamp and Elliston Cemetery Swamp). Swamps are generally level or closed depressions with a seasonal or permanent water table at or above the surface; sometimes biological (peat) accumulation occurs.
W etland land form elements
0 5 10 15 20
Occurrences 17 7 1 3 3 1 1
Salt Lake Swamp No data Lake Lagoon Rock outcrop
Open depression
15.0 GEOLOGY 15.1 Background
Eyre Peninsula is underlain by a basement of crystalline rocks, mainly granite and gneiss. The triangular shape of the peninsula is due to the intersection of two major fault zones. The Lincoln fault runs along the east coast, south-west from the vicinity of Port Augusta and another fault runs from the southern tip of the peninsula north-west to Elliston. The northern section of the peninsula is separated from the Gawler Ranges by the Corrobinnie depression. This depression also extends southwest from Minnipa and is characterised by a series of ephemeral salt lakes (Matthews 2001). The Corrobinnie depression contains old limestone formations, which forms series of sub-surface water areas. The Bridgewater Formation containing these limestone formations is a dominant geological band along the west coast. A number of basins are located within this area, namely the Lincoln, Uley South, Uley Wanilla and Polda Basins. Refer to Map 4 for the geology underlying the surveyed wetlands.
15.2 Analysis
Figure 7. Geological structure underlying wetlands.
The majority of wetlands are located within the Bridgewater Formation (eg salt lakes near Elliston and Lake Hamilton). The Bridgewater Formation consists of partly cemented calcareous sand usually calcreted at the surface. This formation extends from south of Port Lincoln along the west coast to beyond Streaky Bay.
Calcrete is formed by dissolution and replacement of shell fragments which gradually develops a nodular or sheet of hardened material (Parker et al, 1985). Several of the wetlands surveyed are underlaid by
Holocene sediments (eg Round Lake and Sheringa Lagoon) these sediments form the base of the
longitudinal sand dunes of the Corrobinnie Depression. The Holocene sediments are described in Map 4 as undifferentiated alluvial/fluvial sediments. The soil characteristics tended to reflect the underlying geological formations, hence the majority of soils ranged from calcareous sands to silty loams and clays.
Geological structure underlying surveyed wetlands
0 2 4 6 8 10 12 14 16
Occurrence
Occurrence 9 14 4 3 1 1
Holocene Bridgewater formation
Hutchison group
Pleistocene sediments
Quaternary aeolian sediments
No data
16.0 HYDROLOGY 16.1 Background
The wetland survey recorded average annual rainfall for wetland areas and made observations on the main sources of water for the wetlands. The mean average annual rainfall varies from 550 mm to 500 mm on the south of the Peninsula to 400 mm in the north-western section near Elliston and 350 mm near Cleve in the north-east. Nearly all of the rainfall is during winter with Port Lincoln receiving an average rainfall of 260 mm and Elliston of 200 mm (Schwerdtfeger, 1985). Evaporation is high in summer throughout the region and mean monthly evaporation exceeds median monthly rainfall throughout the year except in southern areas in winter.
Surface water is the most common source of water for wetlands on Eyre Peninsula. The surrounding catchment plays a critical role in supplying and filtering water for the lower lying drainage depressions that form the wetlands. Extensive vegetation clearance in many areas has resulted in increases in dryland salinity which has increased water salinity levels. This has affected aquatic fauna composition, aquatic flora and surrounding terrestrial flora. Groundwater occurs in three geological environments which are Pre- cambrian, Tertiary and Quaternary ages. The most important of these is the Bridgewater Formation; refer to Map 4. This formation houses the three southern basins, Lincoln, Uley South and Uley Wanilla. Recharge for these basins is mainly from rainfall (Matthews, 2001).
16.2 Analysis
All of the wetlands surveyed had annual rainfall ranges between 400 and 500 mm. Limited information is available on the groundwater connections to the wetlands surveyed. The Polda Basin near Elliston may have some impact on surrounding wetlands and the Lincoln Basin probably influences Big Swamp and Sleaford Mere. The majority of the information available regarding water resources on Eyre Peninsula is focused on water supplies for human consumption and use by stock; there is a need for investigations regarding water requirements for biodiversity.
17.0 PLANT ASSOCIATION SUMMARY 17.1 Background and Analysis
A large proportion of the wetlands surveyed within the three regions are considered to be saline (>3000EC).
Aquatic flora was noticeably scarce in most water bodies, especially in hyper-saline water bodies (>100 000EC). Those species that tend to dominate saline areas are mainly terrestrial-aquatic species. Genera of the family Chenopodiaceae are common including Halosarcia and Sarcocornia (glassworts or samphires).
Several species of submerged aquatic genera (Ruppia and Lepilaena) also occur within saline water bodies. These genera tend to form the understorey and ground cover within the structural vegetation formation surrounding wetlands.
The most common canopy vegetation type is Melaleuca halmaturorum ssp. halmaturorum. Melaleuca halmaturorum ssp. halmaturorum tall shrubland is considered rare on Eyre Peninsula. The wetland survey recorded 13 sites with Melaleuca halmaturorum as the dominant vegetation association and four sites recorded Melaleuca halmaturorum over Gahnia filum (which is recognised as a threatened plant community on Eyre Peninsula). Several sites recorded Eucalyptus species (E. camaldulensis at three sites and one site with E. diversifolia). The remaining sites recorded introduced grasses either with or without Melaleuca halmaturorum forming the canopy.
The ecological role of Melaleuca halmaturorum 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
• Provide a protective buffer zone between shorelines, estuaries and river systems protecting these waterways from siltation, nutrient runoff and erosion
• Provide flood mitigation by storing and detaining precipitation and runoff thus reducing flow rates and peak floods
• 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
• During major flood events, particulate matter is washed into the rivers and estuaries to provide a food source for heterotrophic mirco-oranisms and detritivores
• 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 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 several key threatening processes which affect the majority of remnant Melaleuca halmaturorum woodlands. Drainage or water extraction, which influences soil chemistry, is common and can cause acid sulphate soils.
Increased nutrients moving into the water due to catchment clearance may result in vegetation dieback and change in water chemistry. Melaleuca halmaturorum requires fresh water flushing on a seasonal basis to stimulate regeneration of seedlings and maintenance of existing specimens.
Plate 2. Melaleuca halmaturorum
Plate 3. Introduced grasses
Plate 4. Gahnia sp.
Melaleuca halmaturorum in full flower providing excellent nectar source for insects.
North of Wanilla, Eyre Peninsula.
Typical example of a wetland with introduced grasses as the dominant vegetation.
Meadow Pool, central west region, Eyre Peninsula.
Example of a wetland with Gahnia sp. as the dominant vegetation association.
Orana Swamp, central west region, Eyre Peninsula.
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 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 such as low stocking rates or major threats from water diversion schemes.
18.2 Analysis
Figure 8. Wetland disturbance
Many wetlands were found to have a number of disturbances at the one site, the two most frequent
disturbances recorded were access tracks and cleared land. The majority of wetlands are located on private property where cleared land for cropping and access tracks are a necessity. Many of the tracks are located adjacent to wetlands and clearance for cropping occurs to the wetland edges. Drains, grazing and fence lines are also common disturbances. Rubbish dumping occurred within two wetlands, both on private property. Altered flows commonly involved extracting water for irrigation or the construction of levy banks for vehicle access and drainage.
Wetland disturbance
18
9 3 2
18 6
6 1
Access tracks Fence lines Rubbish Altered flows Cleared land Grazing damage Drains
Borrow pits/quarry
Flinders Highway
19.0 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 within the wetland system. The diversity of classes recorded may indicate a level of aquatic biodiversity present, or lack of plants recorded indicates limited primary production within the wetland system.
The vegetation classes consisted of:
• Algal • Floating vascular
• Aquatic Moss • Submergents
• Rooted Vascular • Surface vegetation
• Floating leaved •
Algal and aquatic moss commonly comprise Charophyta (stoneworts) and Chlorophyta (green algae) which forms macroscopic mats either attached to plants or in open water. Algal forms the basis for photosynthetic basis for the open water food sources in many inland waters (Boulton and Brock, 1999).
For green algae images 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 members of the family 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 9. Aquatic vegetation classes recordeded.
The aquatic class of rooted vascular is the most common form of vegetation class within the wetlands surveyed. Genera such as Myriophyllum, Halosarcia and Sarcocornia were frequently recorded within those
0 10 20 30
Vegetation classes
Occurrence 2 4 24 7 1 1
Floating Aquatic Rooted No data Floating Algae
surveyed had very little aquatic vegetation abundance or diversity. The majority of vegetation was in the form of terrestrial-aquatic species such as samphires.
20.0 AQUATIC INVERTEBRATE ANALYSIS 20.1 Background
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, Davis and Rolls (1987). 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. They form a basic element in food chains and networks which underlie the general balance of nature
5. Preditation and parasitism; 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:
• Ecosystem stability: the loss of species from highly interrelated systems is likely to cause a cascade of further losses.
• Evolutionary time: diversity within ecosystems maintains greater 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). If samples from all trophic groups are collected, this could suggest that the aquatic ecosystem is a reasonable state of equilibrium. The top of the food chain is occupied by vertebrate predators, including fish, water rats and water birds. Terrestrial predators can be considered to be on the top of the aquatic food chain, and provide a pathway for export of nutrients and other material from the wetland ecosystem
(Boulton and Brock 1999).
Primary producers
Primary producers form two groups those that are suspended or floating and those attached to substrate or other plants. Attached macrophytes includes frindging reeds and submerged plants and periphyton (the biota attached to submerged surfaces). Suspended or floating forms generally consist of the phytoplankton
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 rotifers, 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 Salt Lake Systems
Freshwater organisms in Australia generally tolerate salinities up to about 3 gL (3000 EC), and beyond this there are changes 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 Brock 1999). The beds of many salt lakes are covered with benthic microbial mats dominated by photosynthetic producers, and lake crusts contain propagules of decomposers, producers and consumers. Boulton and Brock (1999) 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. Fishes 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, 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.
20.3 Temporary Wetlands
Many of South Australia’s inland wetlands are temporary and display slightly different invertebrate fauna composition from other wetland systems (saline lakes or permanent waters) Williams (2000) makes four general conclusions from his study of temporary wetlands.
1. Faunal diversity is high and often higher than in many permanent wetlands.
2. A wide range of fauna groups occurs, 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 realises 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).
20.4 Analysis
Thirty-three sites were surveyed with 18 sites returning invertebrate sample results. The remaining 15 sites did not have invertebrates present; these are hyper saline wetlands that do not support micro invertebrates, or had water levels that were to low too retrieve samples. Overall species composition, richness and trophic structure is quite deficient in wetlands surveyed on Eyre Peninsula.
20.4.1 Invertebrate abundance
Table 1 illustrates the invertebrate abundance sampled within the 18 survey sites. Twenty-three species were recorded in total. The average abundance of species within each wetland is approximately four species. Abundance levels varied from one species to 14 species, with three species showing substantially higher frequency of occurrence than the other 15 species. Two of these species are from the family
Ostracoda (Candonocypris sp. and Diacypris cf. spinosa) and the other Daphniopsis pusilla is from the family Cladocera. Both families are widely distributed and common, occurring within inland waters fresh and saline. Ostracods vary in form, some being swimmers, clingers, climbers or burrowers. Cladocerans usually live on the substrate where they feed on fine particulate matter, others are mainly free-swimming and constitute an important part of the plankton of the open water (Williams 1980). Cladocerans are also an important food for zooplanktivorous fish. Their nutritional value is high, they are in particular rich in essential highly unsaturated fatty acids and natural anti-oxidants.
Table 1. Invertebrate abundance
Invertebrate identification Number of records
Acanthocyclops sp. 2
Alona sp. 2
Atherinosoma sp. 1
Austrachiltonia australis 4
Bennologia australis 2
Boeckella triatriculata 5
Calamoecia cilitellata 4
Calamoecia salina 5
Candanocypris sp. 14
Chydorus cf.sphaericus 1
Coxiella striata 1
Cypricercus sp. 5
Daphnia cf. carinata 4
Daphniopsis pusilla 8
Diacypris cf. spinosa 10
Liyodromus sp. 6
Macrothrix spp. 6
Mesochra cf. baylyi 2
Mesocyclops spp. 1
Metacyclops cf. mortoni 6
Mytilocypris 4
Parartemia cf. zietziania 3
Simocephalus cf. elizabethae 1
Plate 6. Diacypris cf. spinosa. Plate 7. Daphniopsis pusilla
Diacypris cf. spinosa. (family Ostracoda) 40X Daphniopsis pusilla (family Cladocera)
20.4.2 Invertebrate diversity
Figure 10 illustrates invertebrate diversity by wetland site. Two wetlands stand out as having high diversity;
these are S3033 (Old Plough Swamp) and S3006 (Big Swamp). Both sites have different landform characteristics, vegetation and water regimes, but with the same occurrence of invertebrate diversity.
Wetland sites S3023 (Lake Tungketta) and S3022 (Middle Lake) are very similar, both being typical salt lake systems with invertebrate species common to both sites. Genera common to both sites includes Mytilocypris, Austrachiltonia, Calamoecia, Diacypris and llyodromus.
Figure 10. Invertebrate diversity by wetland site.
Invertebrate Diversity
0 1 2 3 4 5 6 7 8 9
S3001 S3003 S3006 S3014 S3016 S3017 S3018 S3019 S3020 S3022 S3023 S3026 S3027 S3031 S3033 S3034 S3035 S3037
Plate 8. Old Plough Swamp. Plate 9. Big Swamp
Invertebrate family structure is quite similar between Old Plough Swamp and Big Swamp wetlands both comprising of copepods, cladocerans and ostracods. The differences at each site are on a species level with each comprising six different species and two common species. One conclusion is that the genera found in Old Plough Swamp are adapted to temporary waters (Daphnia, Diacypris, Metacyclops and Calamoecia) while those found in Big Swamp are adapted more to a permanent water regime (Alona, Coxiella, Cypricercus and Simocephalus).
Plate 11. Middle Lake
Plate 12. Lake Tunketta
Middle Lake and Lake Tungketta are good examples of salt lake systems, both sites recorded seven different taxa.
Old Plough Swamp. Temporary water regime located within agricultural land.
Big Swamp. Permanent water regime located within a largely agricultural catchment.
Established aquatic and fringing vegetation exists.
21.0 WATER CHEMISTRY
Chemical processes in permanent and temporary waters are extremely complex. The chemistry of the water directly influences the biological process (such as photosynthesis) the physical features of the wetland also has a strong influence on both the chemical and biological processes. These three factors (chemical, physical and biological) are constantly in a state of movement and change. Changes in these parameters are most apparent in temporary wetlands where a wetting and drying cycle occurs. The majority of wetlands on Eyre Peninsula have seasonal water regimes, filling during winter and remaining dry
throughout spring, winter and autumn.
Depth
Water Temp
Dissolved Oxygen
Conductivity
pH
Nutrients
DRY FILLING FILLED DRYING DRY
Brock and Boulton (1999) state that changes in water quality during drying and filling depend on factors including:
1. sediment properties (composition, nutrients and organic content) 2. type of drawdown (gravity or evaporative)
3. severity of drying (rate of drying, temperature, weathering)
4. conditions of refilling (origin of water, degree of sediment disruption).
Figure 11 describes the changes in chemical variables over time during the phases of filling and drying in temporary wetlands. Seasonal changes in invertebrate composition is also noted.
21.1 pH
21.1.1 Background
The pH value of water indicates how acidic or alkaline it is on a scale 1-14. Acids have a low pH of about 2 for a strong acid like sulphuric acid and about 4 for a weak one like lactic acid. Alkalis have a high pH of about 12 for sodium hydroxide. Pure distilled water has a pH of 7 which is neutral. From pH 7 to 0, a liquid becomes increasing acidic and from pH 7 to 14, a liquid becomes increasingly alkaline.
Generally in South Australia, the pH of natural water ranges between 6.0 and 8.5 with most water bodies in the range 7.0-8.0. The higher pH of natural water bodies is caused by high bicarbonate levels in the water and can raise the pH during the day and lower pH at night. Chemicals entering the water can also affect the pH.
PH is an important environmental indicator. At extremely high or low pH values, the water becomes unsuitable for most organisms.
Figure 12. pH values
14 HIGH (Alkaline)
10 MEDIUM 9 MILD 8 PRISTINE
6 MILD 5 MEDIUM 4
HIGH (Acidic)
1
21.1.2 Analysis
Figure 13. Wetland pH values for surveyed sites on Eyre Peninsula.
The average pH of the wetlands surveyed ranged between pH 7 and 8, which falls into a neutral pH value.
This suggests that aquatic species diversity within the wetlands surveyed are not severely affected by pH levels. Wetland site S3038 (Samphire Flat) recorded the highest acidic reading with a pH of 6; opposing this was wetland site S3016 which recorded the highest alkaline reading of 9. These two sites had very different conductivity readings. Site S3038 was hyper-saline (185 Ms) and site S3016 was slightly saline (14 Ms).
Turbidity readings were also quite different with site S3038 having extremely high turbidity (15 NTU’s) and site S3016 had a turbidity reading of zero. These results suggest that pH is closely linked to conductivity and turbidity levels. pH readings are regarded as a useful secondary chemical indicator of water quality rather than a primary one.
21.2 Conductivity
The majority of wetlands studied within the three regions are affected by salt either through natural processes or by secondary salinisation processes. In closed drainage basins (typical throughout Yorke Peninsula, Eyre Peninsula and Kangaroo Island) salt is retained and accumulated over long periods. This natural accumulation of salt in closed basins results in the development of salt lakes, and this process is primary or natural salinisation. Natural salinisation has caused almost 45% of global surface waters to become more saline (Williams 2001).
Secondary salinisation primarily results from human activities. Disturbances have increased the number of salt lakes and the levels of salt in freshwater wetlands. The main causes of secondary salinisation include:
• Clearance of native deep-rooted vegetation from catchments and its replacement by pasture and other agricultural crops.
• Drainage of saline waste water from irrigated regions.
• Rising saline ground waters and saline intrusions.
pH Values
0 1 2 3 4 5 6 7 8 9 10
S3000 S3001
S3003 S3006
S3016 S3012
S3014 S3014
S3017 S3032
S3033 S3034
S3035 S3019
S3020 S3022
S3023 S3024
S3025 S3026
S3027 S3029
S3030 S3031
S3036 S3037
S3038 Wetland Site
Value
