Thermal pollution and algal growth in the Tuggerah Lakes.

Abstract

Abundant growth of ‘weed’ and its accumulation and decomposition in inshore waters and on the shoreline are seen as increasing problems in estuaries and lakes in regions of expanding populations. The weed may be visually unacceptable, become malodorous as it decomposes, and can considerably reduce the amenity value of the water-way if it interferes with activities such as swimming and boating. In Australia, the phenomenon has been studied in detail in the Peel-Harvey estuarine system in Western Australia (Hodgkin et al. 1985) and the Swan River estuary (John 1987). In New South Wales, Yassini (1985) has provided an overview of the problem of algal growth in Lake Illawarra. In Tuggerah Lakes on the central coast of New South Wales, the problem of excessive weed growth is one of the problems being tackled by Wyong Shire Council in relation to the overall management of the lake system. In this case, as elsewhere in Australia, the weed problem is due to macroalgae (seaweeds) and not aquatic angiosperms (seagrasses). There is no evidence of an explosion in seagrass growth in the last 20 or so years, though there have been changes in the overall distribution (See King & Hodgson 1986, and King & Hodgson 1986 for relevant literature). When the Munmorah Power Station was planned, algal growth was not perceived as a likely outcome of power station operation but seagrasses were studied because of suggestions that the growth of particular ‘reeds’ would accelerate, thereby reducing the cooling field and potentially offering resistance to the pumping of water through the lake. This possibility has not been realised in the 21 years of power station operation.