MEPS prepress abstract  -  DOI: https://doi.org/10.3354/meps13008

Changes in macrofaunal biological traits across estuarine gradients – implications for the coastal nutrient filter

Anna Villnäs*, Urszula Janas, Alf B. Josefson, Halina Kendzierska, Henrik Nygård, Joanna Norkko, Alf Norkko

*Email: anna.villnas@helsinki.fi

ABSTRACT: Benthic macrofaunal communities have a profound impact on organic matter turnover and nutrient cycling in marine sediments. Their activities are of particular importance in the coastal filter, where nutrients and organic matter from land are transformed and/or retained before reaching the open sea. The benthic fauna modify the coastal filter directly (through consumption, respiration, excretion and biomass production) and indirectly (through bioturbation). It is hard to experimentally quantify faunal contribution to the coastal filter over large spatial and temporal scales that encompass significant environmental and biological heterogeneity. However, estimates can be obtained with biological trait analyses. By using benthic biological traits, we explore how the potential contribution of macrofaunal communities to the coastal filter differ between inner and outer sites in an extensive archipelago area, and examine the generality of the observed pattern across contrasting coastal areas of the entire Baltic Sea. Estimates of benthic bioturbation, longevity and size (i.e. “stability”) and total energy- and nutrient contents differed between coastal areas and inner versus outer sites. Benthic traits indicative of an enhanced nutrient turnover but a decreased capacity for temporal nutrient retention dominated inner sites, while outer sites were often dominated by larger individuals, exhibiting traits that are likely to enhance nutrient uptake and retention. The overarching similarities in benthic trait expression between more eutrophied inner vs less affected outer coastal sites across the Baltic Sea suggest that benthic communities might contribute in a similar manner to nutrient recycling and retention in the coastal filter over large geographical scales.