Deep-sea benthic biodiversity and ecosystem functioning in cerianthid fields and adjacent sediments of a subarctic fjord

Epibenthic megafaunal species may serve as ecosystem engineers by creating novel niches for associated fauna. Here we consider cerianthid (tube anemone, Ceriantharia) fields, a common but understudied feature of North Atlantic shelf and deep-sea ecosystems, and their effect on macrofaunal community ecology and ecosystem functioning. Based on remotely operated vehicle push-core sampling of sediments in Hebron Fjord (northern Labrador, Canada) and complementary shipboard incubations, we found that cerianthid fields influence macroinfaunal communities and shift ecosystem functioning. Specifically, increased macrofaunal density and differences in community composition and biodiversity through sediment layers inside cerianthid fields contrasted adjacent sites, along with shifts in nutrient fluxes. Greater degradation of organic matter inside cerianthid fields enhanced silicate efflux. We attribute differences in abundance patterns to predation pressure from cerianthids and altered hydrodynamics inside cerianthid fields that might enhance pelago-benthic coupling, supporting greater densities of deposit-feeding and opportunistic polychaetes.