Structure,dynamics and production of the benthic fauna in Lake Manitoba

The structure and diversity, including seasonal variation, and the energy budget of the benthic fauna in southern Lake Manitoba were studied and related to physical and chemical properties of the water and sediment. A total of 47 taxa were identified but 90 percent of individuals were represented by seven taxa (Candona rawsoni, Cytheromorpha fuscata, Pisidium spp., Amnicola limosa, Harnischia curtilamellata, Procladius freemani and Chironomus sp.). The spatial and temporal dynamics, dispersion patterns and life cycles of these abundant species are described.The net production was 5.05 Kcal/m²/yr for the only carnivorous species (Procladius freemani) and 28.53 Kcal/m²/yr for non-carnivorous species. The gastropod Amnicola limosa and the chironomid Chironomus sp. appear to be the most important contributors to the total biomass and net production of the community. Annual turnover rate (P/B) for all seven taxa aver-aged 2.82, with the chironomid species having the highest value and the gastropod species the lowest (3.7 and 1.75 respectively).Contribution No. 52 of the University of Manitoba Field Station (Delta Marsh).