Partitioning benthic nitrogen cycle processes among three common macrofauna holobionts

• Published in: Biogeochemistry Vol. 157; no. 2; pp. 193 - 213
• Main Authors: Zilius, Mindaugas, Daunys, Darius, Bartoli, Marco, Marzocchi, Ugo, Bonaglia, Stefano, Cardini, Ulisse, Castaldelli, Giuseppe
• Format: Journal Article
• Language: English
• Published: Cham Springer International Publishing 2022; Springer Nature B.V
• Subjects: Ammonium; Ammonium compounds; Annan geovetenskap och miljövetenskap; Baltic Sea; Benthic functioning; Benthos; Biogeosciences; Bioturbation; Bottom water; Cycles; Denitrification; Earth and Environmental Science; Earth Sciences; Ecological function; Ecology; Ecosystems; Ekologi; Environmental Chemistry; Estuaries; Estuarine dynamics; Filter feeders; Geochemistry; Geokemi; Geologi; Geology; Invertebrate-microbe associations; Life Sciences; Macrofauna; Marine crustaceans; Metabolism; Microbial activity; Microbiomes; Microorganisms; Nitrate reduction; Nitrogen; Nitrogen cycle; Nitrogen fixation; Nitrogenation; Nutrients; Other Earth and Related Environmental Sciences; Positive feedback; Reduction; Sediment; Sediments; Solutes; Zoobenthos; Zoologi; Zoology; Nitrogen cycle; Benthic functioning; Sediments; Invertebrate-microbe associations; Nitrate reduction; Baltic Sea
• ISSN: 0168-2563; 1573-515X; 1573-515X
• DOI: 10.1007/s10533-021-00867-8

The effects of single macrofauna taxa on benthic nitrogen (N) cycling have been extensively studied, whereas how macrofaunal communities affect N-related processes remains poorly explored. In this study, we characterized benthic N-cycling in bioturbated sediments of the oligotrophic Öre Estuary (northern Baltic Sea). Solute fluxes and N transformations (N
2
fixation, denitrification and dissimilative nitrate reduction to ammonium [DNRA]) were measured in sediments and macrofauna-associated microbes (holobionts) to partition the role of three dominant taxa (the filter feeder
Limecola balthica
, the deep deposit feeder
Marenzelleria
spp., and the surface deposit feeder
Monoporeia affinis
) in shaping N-cycling. In the studied area, benthic macrofauna comprised a low diversity community with dominance of the three taxa, which are widespread and dominant in the Baltic. The biomass of these taxa in macrofaunal community explained up to 30% of variation in measured biogeochemical processes, confirming their important role in ecosystem functioning. The results also show that these taxa significantly contributed to the benthic metabolism and N-cycling (direct effect) as well as to sediments bioturbation with positive feedback to dissimilative nitrate reduction (indirect effect). Taken together, these functions promoted a reuse of nutrients at the benthic level, limiting net losses (e.g. denitrification) and effluxes to bottom water. Finally, the detection of multiple N transformations in macrofauna holobionts suggested a community-associated versatile microbiome, however, its role was of minor importance as compared to the activity of sediment-associated microbial communities. The present study highlights hidden and interactive effects among microbes and macrofauna, which should be considered analysing benthic functioning.