BIODIVERSITY AND ECOSYSTEM PROCESSES IN FRESH-WATER SEDIMENTS

All freshwater eventually passes through or over sedimentary habitats on the way to oceanic or atmospheric domains. These zones of freshwate r sediments contain an enormous variety of species that produce and pr ocess organic carbon, Some species perform specific functions such as fixing or recycling nitrogen. Others break down contaminants or mix se diments so as to alter the rates of ecosystem processes. Approximately 175000 species have already been described and yet still, new species continue to be discovered. Their diversity and distributions range gr eatly along gradients of depth, dissolved oxygen, latitude, and altitu de in wetlands, lakes, rivers, and groundwaters. Deep, isolated habita ts contain unique, endemic species especially among those organisms wi th limited dispersal ability. Competent scientists must be trained in many parts of the globe to accelerate studies of this species-rich bio ta and essential ecosystem relationships.