Benthic communities of the Gippsland Lakes, Victoria

Samples of benthos from muddy or sandy bottoms along the axis of the Gippsland Lakes, Victoria, and on shallow seagrass beds were taken between November 1978 and October 1979. The benthic communities are described and the likely effects resulting from changes in water usage in the catchment discussed. Gradients in environmental parameters (salinity, temperature, dissolved oxygen and suspended solids) were not regular but were steepest near a constriction in the system, McLennans Strait. Ninety species of benthic fauna were recorded, with greatest diversity and density at the seagrass sites. The fauna was similar to that recorded in other south-eastern Australian estuaries except for its rich amphipod fauna and depauperate bivalve fauna. Densities, especially on seagrass, were higher than recorded in other estuaries although the number of species was lower. Temporal changes in the fauna could not be related clearly to seasonal changes in temperature or other environmental factors. Classification of the data revealed a seagrass community and smaller groups of species and stations, only loosely indicating a faunal gradient along the lakes. A distinct marine fauna was recognized on well-sorted sand at the lower end of the lakes, Reeve Channel, and a freshwater component at the opposite end. Physical structures such as McLennans Strait are responsible for the major differences between the faunas of adjacent areas in the greater part of the system. It is suggested that increased salinity in the future may allow establishment of euryhaline species in more placid parts of the lakes but that deoxygenation of bottom water and high benthic mortalities may occur if a salt wedge is maintained.