Benthic Biological Processes and E sub(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 sub(H) profile taken through the benthic bioturbation zone. Sediment E sub(H), an electrochemical measure of oxidized and reduced compounds in sediment porewater, measures the integrative consequences of all metabolic and transport processes of the benthic community. Biota, especially microbiota, metabolize carbon using a variety of electron acceptors, including O sub(2), SO sub(4) and some nitrogen and metal compounds. Motile benthic macrofauna ingest and transport particles, ventilate deep burrows and anoxic sediment with overlying seawater while sedentary suspension-feeding fauna deposit suspended organic matter onto the sediment surface. Collectively, these metabolic and behavioral processes advect particles and seawater between bottom water and deep sediment and define the overall structure of porewater chemistry. That structure creates a full spectrum of biogeochemical conditions of solubility, reactivity, and microbial metabolism which remineralizes excess organic carbon and most organic contaminants, defines solubility of trace metals, and pushes the vertical E sub(H) profile toward oxidizing conditions. It is proposed that a standard E sub(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 community structure.