Seasonal Variation in the Role of Benthic Macrofauna Communities for Ecosystem Functioning in Shallow Coastal Soft-Sediment Habitats

Coastal zones include a variety of habitats and numerous biodiversity components, which provide essential ecosystem functions and services. In the wake of the escalating climate and biodiversity crises, there is an urgency for increased understanding of how biodiversity affects ecosystem functioning. The strong seasonality in high-latitude ecosystems is adding complexity to these relationships. To examine this complexity, recurrent sampling of benthic macrofauna and solute fluxes was conducted in three shallow (< 4 m) coastal soft-sediment habitats (I sandy mud, II fine sand, and III medium sand) over a year (April 2015–April 2016) in SW Finland (N 59° 50.670′, E 23° 14.963′). In addition to temperature, key benthic fauna species (Macoma balthica, Cerastoderma glaucum, Hediste diversicolor, and Marenzelleria spp.) accounted for variability in solute fluxes at every site (27–47% of the variability explained). At the most exposed site, with medium sand, the organic matter content also apparently affected solute fluxes. These results highlight that the strength of the benthic biodiversity-ecosystem functioning relationships depends on season, macrofauna species, and environmental context.