Freshwater dependent ecosystems

The CFEV database contains data on the following freshwater dependent ecosystems:

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Rivers

Diverse ecosystems, typically with flowing water.

The CFEV Program considers a river to be a freshwater-dependent ecosystem characterised by flowing water.

Tasmania's rivers are as diverse in their character as they are in their condition. Examples range from the wild rivers of the west and the lowland rivers throughout the midlands, to the intermittent rivers along the east coast. Natural and artificial variations can also occur within a single river system from its headwaters to the sea. These systems provide a broad range of habitat for a wide variety of aquatic plant and animal species as well as supporting varied geomorphic features and a range of ecological processes. Rivers are also the life-blood of major agricultural and urban industries in Tasmania and are important for social and recreational activities.

Rivers can be characterised in many ways using biological and physical components. These include aquatic flora and flora communities, both aquatic and within the riparian zone, physical form and hydrology.

The condition of Tasmania's rivers has been affected by a range of threats and impacts associated with human activities. These include changes in catchment land use through land clearance, agriculture, mining, infrastructure and urban and industrial development, as well as water use and regulation through extraction, diversion and storage.

Wetlands

Often vegetated, these shallow, still water ecosystems can be important centres of biodiversity.

The CFEV Program considers wetlands as freshwater-dependent ecosystems that are vegetation dominated and vary in hydrodynamics from deep and permanently inundated to shallow and temporary.

Tasmania has a wide variety of wetlands including sphagnum bogs, peatlands, coastal lagoons, swamp forests and freshwater marshes. The wetlands also vary in permanency from the deep, permanent marshes on the west coast to shallow, temporary wetlands, like those throughout the Midlands, which may dry out seasonally or in dry years.

Wetlands are important ecosystems because they:

• are breeding grounds for many animals, especially macroinvertebrates, fish and waterbirds
• provide protection from floods
• provide habitat and protection for animals
• are areas of high biodiversity
• are important refuge areas for wildlife in times of drought

Wetlands are often perceived as wastelands and as a result have been degraded by impacts such as drainage and alterations to the natural water regime, grazing by stock, vegetation clearance and ploughing for agriculture, pollution from adjacent land use and four-wheel driving activities.

Waterbodies

These deep-water ecosystems are often important landmarks.

The CFEV Program considers waterbodies or lakes as freshwater-dependent ecosystems which are still, open water systems that may undergo cycles of physical stratification and mixing. The CFEV Program also considers inland, naturally saline basins under the same theme.


Tasmania has many lakes and waterbodies, which range in size from the nation's largest, natural, permanent waterbody, Great Lake, to a myriad of tiny freshwater tarns dotted across the Central Plateau. Tasmania is also home to the deepest lake in Australia, Lake St Clair.

Lakes are generally characterised by still, open water which may undergo cycles of physical stratification and mixing. They also provide important habitat for a large number of aquatic flora and fauna species, some of which are endemic to the state.
The lakes and waterbodies in Tasmania are used for many activities including recreational boating and fishing, the generation of hydroelectricity and irrigation for agriculture.

Threats to Tasmania's lakes and waterbodies include changes in lake level regimes, catchment impacts such as land clearance, use of agricultural chemicals and sedimentation, barriers to fish movement, as well as introduced plant and animal species.

Saltmarshes

A little-known coastal ecosystem that is understudied and often ignored.

The CFEV Program considers saltmarshes as freshwater-dependent ecosystems that are influenced by the marine environment. They are recognised by their communities of plants and animals that can tolerate high soil salinity and periodic inundation by sea or brackish water.

Saltmarshes are wetland-like areas that contain communities of plants and animals that can tolerate high soil salinity and periodic inundation by marine or brackish water. Saltmarshes are influenced by tidal movement and therefore, are generally located within estuaries and along the high tide zones of low energy coastlines. They also benefit from freshwater inputs and hence are affected by land and catchment activities.

Saltmarshes are important habitats, which provide essential feeding, roosting and breeding areas for a large variety of birds, particularly migratory species. These intertidal areas are also important nursery areas for a range of marine organisms. Where inundating water is highly saline, saltmarshes are dominated by succulent herbs and shrubs, whereas mildly salt tolerant rushes, sedges and grasses are commonly found in areas which are frequented by freshwater flushes. Saltmarshes act as a buffer and filtration system for sediments and nutrients, while also providing important nutrients to estuarine systems.

In many areas, the extent and health of saltmarsh communities has rapidly declined due to pressure from agriculture, land reclamation and urban development. Saltmarshes have also been used as rubbish tips and invaded by exotic species.

Estuaries

The interface between rivers and the sea, these ecosystems can be highly productive.

The CFEV Program adopted the definition of estuaries from Edgar et al. (1999) as being "semi-enclosed or periodically closed coastal bodies of water in which the aquatic environment is affected by the physical and chemical characteristics of both fluvial drainage and marine systems".

Estuaries are influenced by tidal movement and can periodically become blocked at the ocean end. Estuaries vary in shape, size and topography and are also influenced by both natural and anthropogenic catchment-based processes including: rainfall and run-off, geomorphology, land-use, erosion and vegetation cover (Edgar et al. 1999). Tasmania has many types of estuaries including coastal inlets, drowned river valleys, barrier estuaries, river estuaries and coastal lagoons.

The mix of marine and freshwater influences on estuarine systems results in these areas being highly productive. Estuaries are essential for the survival of many flora and fauna, in particular, birds and fish. Estuaries provide important nursery and feeding areas for many species of fish.
Some migratory wader birds also rely on estuaries as resting and feeding grounds during their long journeys.

In Australia, estuaries are often selected as settlement areas, and as such they support many recreational and commercial activities. Accordingly, estuaries regularly suffer from the human impacts associated with such activities. Human activity in estuaries and their catchments has resulted in the deterioration of water quality, increased siltation and subsequent habitat loss. Estuaries are frequently used as disposal areas for urban and industrial waste. Catchment impacts that affect rivers, such as land clearance and agricultural activities, also filter down to their connecting estuaries.

Reference:
Edgar, G. J., Barrett, N. S. & Graddon, D. J. (1999). A Classification of Tasmanian Estuaries and Assessment of their Conservation Significance using Ecological and Physical Attributes, Population and Land Use. Technical Report Series. Number 2. Tasmanian Aquaculture & Fisheries Institute, Hobart, Tasmania. 231 pp.

Karst

Typically cave systems, but these ecosystems include a range of geographic features unified by the calciferous rocks from which they are formed.

Karst areas are distinctive landforms that occur where certain rock types are easily dissolved in water. This geological process often results in unique surface and sub-surface structures including sinkholes, disappearing streams, springs and complex cave systems. These landforms are strongly associated with the limestone and dolomite areas within Tasmania.

Karst systems provide a variety of distinctive habitats. These can be either terrestrial or aquatic, but both ultimately owe their existence to aquatic origins. The ecological systems associated with karst can be broadly divided into two groups; those that are specialised to the extent that they occur nowhere else (obligate communities), and those that can exist within karst habitats but also occur elsewhere (facultative or opportunistic communities). The obligate faunal communities associated with karst systems are not particularly diverse, but are often distinctive and frequently exhibit high levels of endemism. In Tasmania they include a variety of invertebrates, from minute aquatic snails to blind cave beetles.

A number of direct and indirect impacts can be detrimental to karst systems. Loss of vegetation in the vicinity of caves and sinkholes can lead to erosion and subsequent over-sedimentation of karst. Karst areas have also been used as rubbish dumps and resultant groundwater pollution can impact upon both karst ecosystems and physical structure. Similarly, upstream impacts on river and streams such as grazing, use of agricultural chemicals and water regulation can flow through to karst. More directly, human activities in and around caves have the potential to alter them drastically; increased light and nutrient levels can substantially modify these normally unproductive systems.

Conservation - Karst

Groundwater Dependent Ecosystems

These ecosystems are a lot more extensive than maps suggest and have the potential to be both diverse and novel.

Groundwater dependent ecosystems (GDEs) are broadly defined as 'those parts of the environment, the species composition and natural ecological processes of which are determined by the permanent or temporary presence or influence of groundwater' (SKM 2001).

Some examples include springs, seeps and underground streams. Our knowledge of these systems is far from complete, so the CFEV program deals with them as a list of important locations without information on their biophysical classification or condition. All GDE's are considered to be of high conservation value.

Reference: SKM (2001). Environmental Water Requirements of Groundwater Dependent Ecosystems. Environmental Flows Initiative Technical Report Number 2. Commonwealth of Australia, Canberra.

Conservation - Groundwater Dependent Ecosystems