Mediation of nitrogen by post-disturbance shelf communities experiencing organic matter enrichment

Marija Sciberras; Karen Tait; Guillaume Brochain; Jan G Hiddink; Rachel Hale; Jasmin A Godbold; Martin Solan

doi:10.1007/s10533-017-0370-5

Mediation of nitrogen by post-disturbance shelf communities experiencing organic matter enrichment

Biogeochemistry. 2017;135(1):135-153. doi: 10.1007/s10533-017-0370-5. Epub 2017 Aug 29.

Authors

Marija Sciberras¹, Karen Tait², Guillaume Brochain², Jan G Hiddink¹, Rachel Hale³, Jasmin A Godbold³, Martin Solan³

Affiliations

¹ 1School of Ocean Sciences, Bangor University, Askew St, Menai Bridge, Anglesey LL59 5AB UK.
² 2Plymouth Marine Laboratory, Prospect Place, The Hoe, Plymouth, PL1 3DH UK.
³ 3Ocean and Earth Science, National Oceanography Centre Southampton, University of Southampton Waterfront Campus, European Way, Southampton, SO14 3ZH UK.

Abstract

Microbes and benthic macro-invertebrates interact in sediments to play a major role in the biogeochemical cycling of organic matter, but the extent to which their contributions are modified following natural and anthropogenic changes has received little attention. Here, we investigate how nitrogen transformations, ascertained from changes in archaeal and bacterial N-cycling microbes and water macronutrient concentrations ([NH₄-N], [NO₂-N], [NO₃-N]), in sand and sandy mud sediments differ when macrofaunal communities that have previously experienced contrasting levels of chronic fishing disturbance are exposed to organic matter enrichment. We find that differences in macrofaunal community structure related to differences in fishing activity affect the capacity of the macrofauna to mediate microbial nitrogen cycling in sand, but not in sandy mud environments. Whilst we found no evidence for a change in ammonia oxidiser community structure, we did find an increase in archaeal and bacterial denitrifier (AnirKa, nirS) and anammox (hzo) transcripts in macrofaunal communities characterized by higher ratios of suspension to deposit feeders, and a lower density but higher biomass of sediment-reworking fauna. Our findings suggest that nitrogen transformation in shelf sandy sediments is dependent on the stimulation of specific nitrogen cycling pathways that are associated with differences in the composition and context-dependent expression of the functional traits that belong to the resident bioturbating macrofauna community.

Keywords: Ammonia-oxidisers; Bioturbation; Bottom fishing; Denitrification; Ecosystem functioning; Microbial–invertebrate interactions; Nitrogen cycling.