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Nitrogen incorporation and retention by bacteria, algae, and fauna in a subtropical, intertidal sediment: An in situ 15N‐labeling study
Author(s) -
Veuger Bart,
Eyre Bradley D.,
Maher Damien,
Middelburg Jack J.
Publication year - 2007
Publication title -
limnology and oceanography
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.7
H-Index - 197
eISSN - 1939-5590
pISSN - 0024-3590
DOI - 10.4319/lo.2007.52.5.1930
Subject(s) - benthic zone , sediment , environmental chemistry , fauna , microbial population biology , nitrogen , biomass (ecology) , chemistry , intertidal zone , ecology , biology , bacteria , organic chemistry , paleontology , genetics
We performed a 15 N‐labeling study to investigate nitrogen incorporation and retention by the benthic microbial community (bacteria and benthic microalgae) and fauna in the intertidal sediment of the subtropical Australian Brunswick Estuary. The main experiment involved an in situ 15 N pulse‐chase experiment. After injection of 15 NH 4 + into the sediment, 15 N was traced into bulk sediment, total hydrolyzable amino acids (THAAs, representing bulk proteinaceous biomass), the bacterial biomarker D‐alanine, and fauna over a 30‐ d period. Additional experiments included short‐term (24 h) incubations of sediment cores injected with different 15 N‐labeled substrates (NH 4 + , NO 3 − , urea, and an amino acid mixture) and sediment core incubations for analysis of benthic fluxes of O 2 , dissolved inorganic carbon, NH 4 + , NO x − , dissolved organic nitrogen, and N 2 . 15 N was rapidly incorporated and strongly retained in microbial biomass (THAAs) during the 30‐d period in situ, indicating efficient recycling of 15 N by the benthic microbial community. Analysis of 15 N in D‐alanine revealed a major bacterial contribution (50–100%) to total microbial 15 N incorporation and retention. 15 N was also incorporated into fauna via grazing on 15 N‐labeled microbial biomass, but this was a negligible fraction (<1%) of total 15 N in the sediment. Altogether, results show that efficient recycling of nitrogen by the benthic microbial community can be an important mechanism for nitrogen retention in the sediment and an important pathway supporting benthic microbial production.