TY - JOUR

T1 - Mediation of nitrogen by post-disturbance shelf communities experiencing organic matter enrichment

AU - Sciberras, Marija

AU - Tait, Karen

AU - Brochain, Guillaume

AU - Hiddink, Jan

AU - Hale, Rachel

AU - Godbold, Jasmin

AU - Solan, Martin

PY - 2017/9

Y1 - 2017/9

N2 - 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 ammoniaoxidiser community structure, we did find an increase in archaeal and bacterialdenitrifier (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.

AB - 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 ammoniaoxidiser community structure, we did find an increase in archaeal and bacterialdenitrifier (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.

KW - ammonia-oxidisers

KW - bioturbation

KW - bottom fishing

KW - denitrification

KW - ecosystem functioning

KW - microbial-invertebrate interactions

KW - nitrogen cycling

U2 - 10.1007/s10533-017-0370-5

DO - 10.1007/s10533-017-0370-5

M3 - Article

VL - 135

SP - 135

EP - 153

JO - Biogeochemistry

JF - Biogeochemistry

SN - 0168-2563

IS - 1-2

ER -