The seagrasses of Lake Illawarra, New South Wales.

Abstract

Ecological studies on seagrasses and seagrass communities in eastern Australia date back only as far as those of Wood (1959a, b). The most detailed studies in New South Wales have been made on the central coast lakes, Lake Macquarie (see King 1986, for references) and Tuggerah Lakes (see King & Holland 1986). Detailed studies in those lakes over five years (King & Hodgson 1986) showed that in terms of the area occupied by seagrasses, species composition of the communities, and the biomass of the eelgrass Zostera capricorni Ascherson, there are marked fluctuations which cannot be correlated easily with seasonal or environmental changes. Such variation appears to be inherent in the nature of seagrass communities but has not often been properly documented. In some cases aerial photographs can be used to give an overview of the (recent) history of the distribution of seagrass beds but without concurrent field survey there is no information on species present or biomass. The biota of Lake Illawarra is of special interest, not only because it is in a region of rapid urbanisation with associated recreational use, but also because of proposals to refurbish and upgrade the existing Tallawarra Power Station. Lake Illawarra is already subject to environmental problems, especially eutrophication which has resulted in excessive algal growth (LIMC 1986b), but while this is a major immediate problem the most severe long-term concern is with the infilling of the lake (LIMC 1986a). Lake Illawarra has, as a consequence, been the subject of a range of intensive studies most of which are summarized in the ‘Environmental Audit’ (SPCC 1986).