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UBC Theses and Dissertations

The role of meiofauna in the benthic community of a small oligotrophic lake Hoebel, Michael


Meiofaunal distribution and abundance were studied in Marion Lake, a small, shallow (8m maximum) oligotrophic lake in southwestern British Columbia. Experimental techniques were used to investigate the influence of food and predation on meiofaunal populations, and to estimate relative carbon -flow to all components (micro-, meio-, and macrofauna) of the zoobenthic community. In two years' sampling of over 50 species of meiofaunal rotifers, nematodes, copepods, cladocerans and halacarine mites, only a few species were abundant. Three depth zones were sampled (1.0, 2.5, 4.5m) and maximum densities occurred at 2.5m. Population densities of all groups were stable over the sampling period, fluctuating less than one order of magnitude annually. In culture studies, representative meiofaunal species had longer generation times and lower reproductive rates than expected. Attempts to use laboratory results to predict field population dynamics were generally unsuccessful, but led to clarification of reproductive parameter estimates. Experiments in the laboratory and in the field suggested that meiofaunal species are not food-limited. Predation on meiofauna is not heavy but might be significant for those species whose reproduction is suppressed by adverse temperatures. Radiotracer experiments indicated that carbon flow to the zoobenthic community from sediment microflora was partitioned approximately 12% to microfauna (ciliates), 12% to meiofauna, and 76% to macrofauna, while the contributions to zoobenthic biomass were 1%, 7% and 92% respectively. In related experiments, a common harpacticoid copepod species had a high assimilation efficiency but rapidly respired and excreted recently ingested carbon. Meiofaunal organisms are apparently not an important food source for higher trophic levels in Marion Lake but may play a significant role in stimulating microfloral production by their grazing activity.

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