Macrofaunal control of microbial community structure in continental margin sediments

Abstract

Significance The majority of the seafloor is bioturbated by macrofauna and most organic carbon mineralization in marine sediments is performed by microorganisms inhabiting bioturbated sediment. However, little is known about how sediment macrofauna influence the community structure of these microorganisms. We show that microbial community composition differs systematically between bioturbated and nonbioturbated sediments across divergent continental margin settings. While microbial communities in bioturbated surface sediments are regulated by macrofauna-controlled geochemical variables, subsurface microbial communities show site-related trends, which correspond to differences in organic carbon sources. Our study produces insights into the controls on microbial community structure in marine sediments. Such insights are necessary to understand the inner workings of the global carbon cycle.