BENTHIC BIOLOGICAL PROCESSES AND E-H AS A BASIS FOR A BENTHIC INDEX

It is proposed that the common measures of benthic community condition can be augmented with a vertical E-H profile taken through the benthi c bioturbation zone. Sediment E-H, an electrochemical measure of oxidi zed and reduced compounds in sediment porewater, measures the integrat ive consequences of all metabolic and transport processes of the benth ic community. Biota, especially microbiota, metabolize carbon using a variety of electron accepters, including O-2, SO4 and some nitrogen an d metal compounds. Motile benthic macrofauna ingest and transport part icles, ventilate deep burrows and anoxic sediment with overlying seawa ter while sedentary suspension-feeding fauna deposit suspended organic matter onto the sediment surface. Collectively, these metabolic and b ehavioral processes advect particles and seawater between bottom water and deep sediment and define the overall structure of porewater chemi stry. That structure creates a full spectrum of biogeochemical conditi ons of solubility, reactivity, and microbial metabolism which reminera lizes excess organic carbon and most organic contaminants, defines sol ubility of trace metals, and pushes the vertical E-H profile toward ox idizing conditions. It is proposed that a standard E-H probe inserted downward through the bioturbation zone will provide a general measure of this resulting porewater chemistry and thus the impact of feeding, irrigation, and metabolism of the total macro, meio, and microbenthic community. If such a measure can be validated it will permit extended measurement of community function and reduced efforts in measuring com munity structure.