Development of a diatom water quality calibration set for coastal lakes of NSW, a tool for effective lake management and restoration.

A project undertaken at the School of Environmental Science & Management, southern Cross University, Lismore, and supervised by K Taffs

Coastal lakes are rare ecosystems that contain a high level of biodiversity. They are threatened by a range of conflicting land uses including urbanisation, agricultural land use practices and tourism. Coastal lake ecosystems are a high management priority and sometimes require essential restoration works. Yet, many coastal lakes are difficult to manage because of their remote location and inadequate knowledge of the lake history, in particular its response to past climatic and human induced environmental changes.

Techniques are available to increase our understanding of coastal lake ecosystems in a rapid and cost effective manner. Biomonitoring of lakes using diatoms as bioindicators is widely used overseas but a neglected technique within Australia. Diatoms are the most widely used group of bioindicators, and they are particularly suited to studies of water quality.

In northern NSW there are a large number of coastal lakes. These lakes are under increasing pressure from residential developments, agricultural land use and tourism activities, among others. These lakes have a high biodiversity and hence conservation significance, often offering rare habitats for threatened species in addition to being of high value for human use as many coastal lakes also serve as town water supplies. However, due to the impact of multiple activities many are experiencing degradation. Basic environmental data on the history of these lakes is rarely available but of high priority for management agencies. Hence, there is a need for the construction of diatom training sets and hence the establishment of diatom transfer functions in order to construct baseline environmental data of northern NSW coastal lakes that can then be applied to the active management and restoration of these ecosystems.

The aim of this project is to undertake the essential  monitoring necessary to develop a diatom water quality calibration set for northern NSW. Such a dataset is of high priority for the effective management and restoration of NSW coastal lakes. This research will quantify water quality fluctuations and the associated fluctuations in diatom assemblage species and abundance. Thereafter, water quality conditions can be monitored through sampling of diatom communities and past water quality changes can be reconstructed from fossil diatoms assemblages. Such a calibration set will allow more time and cost effective monitoring and management of NSW coastal lakes.

This research project will enable the:

• identification of diatom assemblages unique to coastal lakes of NSW;
• construction of a diatom reference collection for coastal lakes of NSW;
• construction of diatom transfer functions enabling monitoring and reconstruction of water quality in coastal lakes of NSW.
• biomonitoring of water quality in coastal lakes of NSW; and
• reconstruction of the water quality history of coastal lakes of NSW.

Thus far (July, 2003), three sampling trips have been completed, sampling diatom assemblages and water quality of a range of coastal lakes between Coffs Harbour and Tweed Heads. A relationship between diatom communities and the associated water quality conditions will be established after 12 months of sampling is completed.