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Lacustrine Wetlands

Lacustrine wetlands are large, open, water-dominated systems (e.g. lakes). This definition also applies to modified systems which possess characteristics similar to lacustrine systems (e.g. deep standing or slow-moving waters).

 

MILLENNIUM ECOSYSTEM ASSESSMENT REPORTING CATEGORY

Inland Waters

 

What ecosystem functions do lacustrine wetlands perform?

Lakes can occur naturally in landscape depressions retaining sediments and creating important water storages.

Table 1 presents the magnitude lacustrine wetlands perform different ecosystem functions relative to other ecosystems in SEQ. From this table, it can be seen that Lacustrine wetlands perform highly the ecosystem functions under all four ecosystem function categories.

Lacustrine wetlands are not a common type of natural wetland in SEQ. The unique lacustrine wetlands on our sand islands provide habitats for many rare and threatened species. As water retaining features in the landscape they have a major role as refugia, a role which will become more critical under projected increases in climate variability. Animals adapted to living in lacustrine wetlands include fish, reptiles and many species of waterbirds, the natural balance of species provides biological control of pests within this ecosystem and to surrounding terrestrial environments.

Due to the water storage ability of lacustrine wetlands, many natural lakes have been modified to allow them to store more water and many other types of wetlands have also been converted to lacustrine systems. Lacustrine wetlands play a major role in retaining sediments and act as effective assimilators and biotransformers of nutrients and wastes. However care must taken to ensure that the systems are not overloaded or these functions can be significantly impaired or lost.

These wetlands, in combination with other wetland types (palustrine, riverine, estuarine, subterranean) provide a connected network throughout the landscape which facilitates many processes including the movement of species. Lacustrine wetlands play a major role in mitigating the impacts of flooding by retaining floodwaters and slowly releasing it, in fact this is one of the reasons for the construction of many of our (artificial) reservoirs (such as dams). Large reservoirs store significant quantities of carbon and can have a major influence on gas regulation and local climate.

 

Table 1:The relative magnitude (to other Ecosystem Reporting Categories) lacustrine wetlands perform each ecosystem function.

Ecosystem Function Category Ecosystem Function 0
1
2
3
4
5
Regulating Functions
Gas Regulation            
Climate Regulation            
Disturbance Regulation            
Water Regulation            
Soil Retention            
Nutrient Regulation            
Waste Treatment and Assimilation            
Pollination            
Biological Control            
Barrier Effect of Vegetation            
Supporting Functions
Supporting Habitats            
Soil Formation            
Provisioning Functions
Food            
Raw Materials            
Water Supply            
Genetic Resources            
Provision of Shade and Shelter            
Pharmacological Resources            
Cultural Functions
Landscape Opportunity            

 

What types of lacustrine wetlands are in SEQ?

This Ecosystem Reporting Category contains all 'enclosed' natural and semi-natural large deep standing open-water dominated ecosystems. The term enclosed is applied in the context that the release of water from this system is not controlled by humans in the form of 'gates' such as with dams. Large open-water dominated systems where water is held and released through human control mechanisms are assessed under the Ecosystem Reporting Category 'Dams'. Water maybe extracted however from lacustrine systems through means of irrigation. This Ecosystem Reporting Category was assessed predominantly on the water body itself. Vegetation surrounding this water body, particularly if it is a recognised RE will be found in a seperate Ecosystem Reporting Category. Therefore, when assessing the ecosystem functions and the potential to provide ecosystem services within a decision making context, lacustrine wetlands should be assessed along with the adjacent ecosystems.

 

Lacustrine wetlands provide refugia in times of drought.

A lacustrine wetland on Moreton Island.

Links to other publications and websites

Australian Society for Limnology
WetlandCare - Types of wetlands
WetlandInfo
Lacustrine Conceptual Models
Ramsar Convention

 

What is the area and extent of lacustrine wetlands in SEQ?

Lacustrine wetands cover approximately 16 km2, 0.06% of SEQ. This map shows lacustrine wetlands are extremely scattered across SEQ. The lakes of Moreton and North Stradbroke Island (e.g. Blue Lagoon and Brown Lake) should be assessed under this category however they are not identified in this map. The large lakes found in the north including Lake Cootharaba have tidal influences and are classified under the coastal zone wetlands for the purposes of this Framework.

 

What is the vulnerability of lacustrine wetlands and threats to this ecosystem in SEQ?

In their natural state these systems have a great degree of robustness and resilience to national climate variability. Plants and animals have adapted features such as migration, dormancy, breeding strategies etc to deal with this variability and they can "bounce back" from extreme events to become hot spots of biodiversity. Unlike palustrine wetlands, many of the lacustrine systems in SEQ are now permanently wet and their functions have changed from what they originally were. In addition many lacustrine systems are now disconnected from other aquatic systems by the construction of levee banks and dam walls and while they act as refugia there are limits on the role they may play in recolonising areas after droughts and other disasters.  

Development, earthworks and water extraction can all harm or destroy lacustrine wetlands and most lacustrine wetlands in SEQ are significantly modified. Feral animals such as exotic fish (gambusia, goldfish, carp) and invasive plants (water hyacynth, salvinia etc.) spreading into lakes can kill or overwhelm local species and upset the wetland’s natural balance. Excessive nutrients and sediments can damage the natural functioning of wetlands and lead to poor water quality and the increase of nuisance and public health issues such as toxic algal blooms. 

 

How do we manage lacustrine wetlands in SEQ?

The Queensland Government Department of Environment and Heritage Protection has direct responsibility for the protection, conservation and management of wetlands in SEQ, a responsibility shared with local government and the Australian Government (e.g. wetlands of international significance such as lakes on the islands in Moreton Bay). These responsibilities are found in laws passed by the Queensland parliament, laws of the Commonwealth, international obligations and in agreements between state, local and the federal governments. Policies, laws and management plans relating to the management of lacustrine wetlands include sustainable water use and extraction, land use planning, impacts on threatened and migratory species, development impacts and impacts on water quality. In addition to policies, legislation and plans the active management of wetlands by landholders, non-government organisations, SEQ Catchments and local councils play a role in ensuring the health of wetlands in SEQ.

Better recognition of the ecosystem services provided by lacustrine wetlands would promote and encourage more informed and integrated decision making. If statutes do not allow for such values to be considered in decision making, opportunities for sustainable wetland management will be missed. Considering lacustrine wetlands independently of the other aquatic systems in the landscape again can lead to poor decision making. Opportunities should be explored for considering landscape processes and the role that lacustrine wetland play in this. This in turn may lead to the rehabilitation of existing wetland areas, possible reinstatement of others and multiple outcomes.