The macrobenthic fauna of Great Lake and Arthurs Lake, Tasmania

The histories of Great Lake and Arthurs Lake are outlined In terms of geology, geomorphology, discovery, previous biological collections and drainage alterations. Collections of the benthic fauna were made from six sites in each lake every two months for a period of twelve months in Great Lake and fourteen months in Arthurs Lake. A total of 1560 grab samples in 20 sample series were examined. The number of individuals in each species was counted and total wet weights for each sample series were estimated. Physical data collected included sediment particle size distribution and organic content as well as temperature readings. An accurate and comparatively complete species list for each lake has been compiled and affinities are discussed. Approximately 15 species collected during the survey have been recognised as new to science and taxonomic descriptions have been made, or are pending. The data were briefly examined for variation within sample series at each site and for seasonal variation within a site. Some data on life histories of certain species are presented. Detailed analyses of faunal variation between sites, within and between lakes were made. This was done using both qualitative and quantitative (numbers of individuals) data. Cluster analysis, using various sorting strategies, generally grouped sites from the original lake areas of both lakes before grouping sites from different levels of the same lake. Principal coordinates analysis gave similar results. Biomass levels are presented and discussed in terms of component species groups. Instantaneous growth rates of some species are briefly examined. The species diversity and benthic biomass of the two lakes are discussed in relation to other Tasmanian, Australian and overseas lakes. The topics of lake typology and lake classification are examined both in relation to Australian lakes and in general. The question of prediction of lacustrine production levels is also briefly examined.