The relative effects of bottom trawling, organic enrichment, and natural environmental factors on coastal seabed communities

Abstract

Coastal regions are under intense and growing pressure from human activities. Here, we examine how human and natural drivers interact with benthic communities, species, and life-history traits across four distinct coastal areas. Sediment organic content was a key driver of seabed community characteristics, with positive (increased benthic biomass) and strongly adverse (depauperate communities) effects observed. Similarly, environmental factors such as bottom currents were highly influential. In contrast, bottom trawling impacts varied by location. Beam trawling in areas of low organic enrichment was most damaging to seabed fauna, even in the presence of strong bottom currents. However, we did not observe any faunal impacts of trawling under chronic enrichment, despite the fishery using relatively heavy gears (e.g. otter trawls) at high intensities. Lastly, we discuss how human and natural factors interact and shape seabed ecosystems under different conditions, and how management measures can be adapted to improve coastal seabed health.