Microbial extracellular polysaccharides are ubiquitous in the epilithon covering submerged lotic surfaces, yet their significance to carbon transfer in these ecosystems is unknown. The proposed research will estimate production of bacterial and algal biomass and the production of microbial extracellular polysaccharide on wood substrates in the Ogeechee River, a sixth order blackwater river, and measure the efficiency with which extracellular polysccharide may be assimilated by nymphal ayflies and by oligochaets. Assimilation of extracellular polysaccharide will be determined by feeding studies using 14C labelled extracellular polysaccharides. These polysaccharides will be purified form cultures of slime-producing bacteria which have been isolated from wood submerged in the Ogeechee River. Oak dowels in stream-side flumes will be used as subtrates for microbial colonization. If extracellular polysaccharides are assimilated by freshwater invertebrates, the contribution of microbes to invertebrate productivity would be much greater than suggested by estimates of cellular consumption alone. The assimilation of these products of microbial metabolism may contribute to meeting detritivore carbon requirements in many aquatic habitats where cellular microbial biomass is insufficient to meet detritivore needs. This research should be of significant basic ecological interest and produce results with meaning for stream management. The student's mentor is an excellent scientist, and institutional accommodations are good. The Ecosystem Studies Program recommends support for this doctoral dissertation improvement project.
