|Local:||IPMA Algés Lisboa|
Subaqueous sedimentary environments are inhabited by a variety of macro- and micro-organisms distributed according to life habits, availability of food and space, and, in the case of micro-organisms, availability and types of electron donors and acceptors. The heterogeneous distribution of organisms and their various activities create a dynamic, three-dimensional mosaic of environments with distinctly different chemical properties among which fluxes are driven by ever changing concentration gradients. In such a dynamic environment the transient state prevails at all scales: burrows are excavated and refilled; burrows are irrigated periodically by their inhabitants; food is captured and stored; the speciation of bacteria changes as the available electron acceptors change; the local redox potential changes and with it the oxidation state of several elements; complexes are formed with ligands produced by bacteria; solutes diffuse or are advected. This talk will illustrate the rich complexity of the sedimentary habitat with data on the effects of functional group species of benthos on fluxes of nutrients; direct visual observation of the dynamics of burrow excavation; and data on the fine scale distribution of metal species in different sedimentary environments.