Research Product

Processing of sand by sand dollars (Echinodermata: Mellita quinquiesperforata) resulted in modification of the benthic microbial community without a significant effect on gross nutrient balances. Measures of cellular and membrane biomass (total adenosine nucleotides, lipid phosphate and chlorophyll a) were essentialy unchanged. Muramic acid concentration and thymidine incorporation into DNA, which are measures of prokaryotic biomass and activity, remained unchanged. Total metabolic activity, measured as acetate incorporation into lipid, was unchanged. Lipid glycerol and the inositol and glucosamine remaining in the extracted residue were reduced in the processed sediment, as was sulpholipid biosynthesis. Fatty acids characteristic of prokaryotes were enriched whereas fatty acids characteristic of microeukaryotes decreased in processed sands. The same was true for the lipid neutral carbohydrates. Examination of meiofauna showed significant reduction in foraminifera, suggesting that sand dollars are selective predators for a portion of the nonphotosynthetic microeukaryotes, having little effect on the biomass or metabolic activity of benthic prokaryotes.