INTERSPECIFIC DIFFERENCES AMONG MEIOBENTHIC COPEPODS IN THE USE OF MICROALGAL FOOD RESOURCES

We examined the potential for interspecific differences among meiobent hic copepods in their exploitation of microalgal food resources in a n atural benthic community. The feeding behaviors of Coullana sp., Cleto camptus deitersi, Microarthridion littorale, and Pseudostenhelia wells i were examined using C-14-radiotracer grazing experiments and gut-pig ment analyses. In one grazing experiment, laboratory-cultured microalg ae were labeled using (NaHCO3)-C-14 and injected into intact sediment cores to determine whether copepods were grazing on algae from the wat er column and/or at the sediment-water interface. In another grazing e xperiment, (NaHCO3)-C-14 was injected directly into sediment cores and grazing on C-14-labeled natural algae was measured. Fluorometric anal yses of gut pigments were used to determine the recent feeding histori es of copepods. Functional responses of copepod feeding to variation i n sedimentary chlorophyll (chi) a concentrations were also used to dis cern interspecific differences in feeding. Coullana sp. grazed on micr oalgae from the water-column and at the sediment-water interface. C. d eitersi grazed predominantly on microalgae from the sediment-water int erface. Grazing on laboratory-cultured algae was minimal in M. littora le and I! wellsi, but grazing experiments with C-14-labeled natural al gae and gut-pigment analyses indicated that these copepods grazed on m icroalgae in the field. However, a positive functional response to chi a concentrations by M, littorale and a lack of a functional response by P. wellsi suggest that these 2 species exploit algal resources diff erently. Collectively, our observations indicate that each copepod spe cies examined exploits microalgal resources differently.