Seasonal cycle of benthic denitrification and DNRA in the aphotic coastal zone, northern Baltic Sea

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http://hdl.handle.net/10138/317404

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Hellemann , D , Tallberg , P , Aalto , S L , Bartoli , M & Hietanen , S 2020 , ' Seasonal cycle of benthic denitrification and DNRA in the aphotic coastal zone, northern Baltic Sea ' , Marine Ecology. Progress Series , vol. 637 , pp. 15-28 . https://doi.org/10.3354/meps13259

Title: Seasonal cycle of benthic denitrification and DNRA in the aphotic coastal zone, northern Baltic Sea
Author: Hellemann, D.; Tallberg, P.; Aalto, S. L.; Bartoli, M.; Hietanen, S.
Contributor: University of Helsinki, Ecosystems and Environment Research Programme
University of Helsinki, Ecosystems and Environment Research Programme
University of Helsinki, Ecosystems and Environment Research Programme
Date: 2020-03-05
Language: eng
Number of pages: 14
Belongs to series: Marine Ecology. Progress Series
ISSN: 0171-8630
URI: http://hdl.handle.net/10138/317404
Abstract: Current knowledge on the seasonality of benthic nitrate reduction pathways in the aphotic, density stratified coastal zone of the Baltic Sea is largely based on data from muddy sediments, neglecting the potential contribution of sandy sediments. To gain a more comprehensive understanding of seasonality in this part of the Baltic Sea coast, we measured rates of benthic denitrification, anammox and dissimilatory nitrate reduction to ammonium (DNRA) monthly in the ice-free period of 2016 in both sandy and muddy aphotic sediments, northwestern Gulf of Finland. No anammox was observed. The seasonal cycle of denitrification in both sediment types was related to the hydrography-driven development of bottom water temperature. The seasonal cycle of DNRA was less clear and likely connected to a combination of bottom water temperature, carbon to nitrogen ratio, and substrate competition with denitrification. Denitrification and DNRA rates were 50-80 and 20% lower in the sandy than in the muddy sediment. The share of DNRA in total nitrate reduction, however, was higher in the sandy than in the muddy sediment, being (by similar to 50%) the highest DNRA share in sandy sediments so far measured. Our data add to the small pool of published studies showing significant DNRA in both cold and/or sandy sediments and suggest that DNRA is currently underestimated in the Baltic coastal nitrogen filter. Our results furthermore emphasize that the various environmental conditions of a coastal habitat (light regime, hydrography, and geomorphology) affect biogeochemical element cycling and thus need to be considered in data interpretation.
Subject: Nitrate reduction
Sandy sediment
Coastal filter
Benthic-pelagic coupling
Water column density stratification
Organic matter
Geomorphology
Northern Gulf of Finland
DISSIMILATORY NITRATE REDUCTION
ISOTOPE PAIRING TECHNIQUE
ESTUARINE SEDIMENT
MARINE-SEDIMENTS
NITROGEN REMOVAL
NUTRIENT FLUXES
FIXED-NITROGEN
ANAMMOX
AMMONIUM
NITRIFICATION
1172 Environmental sciences
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