We will investigate how small-scale heterogeneity and horizontal and vertical, multilevel interactions affect biodiversity-ecosystem functioning (BDEF) relations in intertidal, shallow subtidal and deep sea sediments. Functional properties investigated include primary (microalgae) and secondary production (meio- and macrobenthos), EPS secretion, OM minteralization and denitrification by prokaryotes. We will combine field studies and experiments using functionally well-characterized groups of organisms.