Sediment microtopography predicts localised benthic ecosystem functioning and the effect of species interactions

Abstract

Soft-sediment ecosystems play a crucial role in marine environments, yet understanding the relationships between species composition and ecosystem functioning remains challenging. We investigated the potential of sediment microtopography as a predictor of ecosystem functioning in soft-sediment environments. We conducted controlled laboratory experiments focusing on the activity and microtopography generated by 2 co-occurring and functionally important species: the tellinid bivalve Macomona liliana and the maldanid polychaete Macroclymenella stewartensis. Custom-built, flow-through, gas-tight tanks were utilized to quantify sediment microtopography and assess benthic fluxes and porewater nutrient concentrations. Rugosity explained between 35 and 61% of the variability in oxygen, ammonium and nitrate + nitrite fluxes and was positively correlated with the variability of deep porewater ammonium concentrations. As a first step to validating direct links between microtopography and biophysical drivers of ecosystem processes, we highlight the potential to advance biodiversity-ecosystem function relationships for seafloor habitats. Broader investigation of the potential of microtopography as a surrogate for ecosystem functioning will lay the groundwork for novel approaches to predict and characterize changes in these vital coastal environments and inform management strategies.