Studies on the meiofauna of rocky shores

Doctoral Thesis


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University of Cape Town

Annual macrofaunal and meiofaunal standing stocks were estimated on an exposed rocky shore along the west coast of False Bay, South Africa, using comparable area based sampling techniques. While meiofaunal densities exceeded those of macrofauna in all zones, by an overall ratio of approximately 400:1, macrofaunal biomass exceeded that of meiofauna by an overall ratio of 10:1. The numbers of meiofauna were not evenly distributed across the shore but varied with the algal standing stocks in each zone and their sediment load. By incorporating turnover ratios from the literature, mean annual productivity ratios were calculated which suggested that meiofauna were responsible for 25 of total (excluding bacterial) secondary production. To follow this up, the impact of wave exposure on the meiofauna of one species of alga (viz. Gelidium pristoides) was examined on five shores around False Bay. Meiofaunal densities (dominated by animals between 63um-280um) were significantly greater on sheltered than exposed shores. As the minimum width of Gelidium fronds exceeds that of these permanent meiofauna, and tufts offer little resistance to wave action, only those individuals living in the dense, holdfast region of plants could escape the impact of waves on exposed shores. Total meiofaunal biomass per plant remained constant irrespective of shore type, due to the greater numbers of juvenile bivalves and amphipods on exposed shores. Algal and herbivore biomass were not significantly different between shore types around False Bay and therefore, the proportional contribution by meiofauna to total secondary production on sheltered shores was predicted to be greater than on exposed shores, where the biomass of macrofaunal filter feeders was very high. It has previously been argued that differences in meiofaunal communities between plant species are a result of differential surface area, number of habitats and refugia from predation. The possible fate of meiofaunal productivity as food for higher trophic levels (fish) and the mediating role played by algal complexity was investigated in a series of carefully designed laboratory and field experiments.

Bibliography: leaves 88-97.