Hellemann , D , Tallberg , P A S , Bartl , I , Voss , M & Hietanen , S S 2017 , ' Denitrification in an oligotrophic estuary: a delayed sink for riverine nitrate ' , Marine Ecology. Progress Series , vol. 583 , pp. 63-80 . https://doi.org/10.3354/meps12359
Title: | Denitrification in an oligotrophic estuary: a delayed sink for riverine nitrate |
Author: | Hellemann, Dana; Tallberg, Petra Astrid Sofia; Bartl, Ines; Voss, Maren; Hietanen, Siru Susanna |
Contributor organization: | Environmental Sciences Susanna Hietanen / Principal Investigator Aquatic Biogeochemistry Research Unit (ABRU) Marine Ecosystems Research Group |
Date: | 2017-11-16 |
Language: | eng |
Number of pages: | 18 |
Belongs to series: | Marine Ecology. Progress Series |
ISSN: | 0171-8630 |
DOI: | https://doi.org/10.3354/meps12359 |
URI: | http://hdl.handle.net/10138/230263 |
Abstract: | Estuaries are often seen as natural filters of riverine nitrate, but knowledge of this nitrogen sink in oligotrophic systems is limited. We measured spring and summer dinitrogen production (denitrification, anammox) in muddy and non-permeable sandy sediments of an oligotrophic estuary in the northern Baltic Sea, to estimate its function in mitigating the riverine nitrate load. Both sediment types had similar denitrification rates, and no anammox was detected. In spring at high nitrate loading, denitrification was limited by likely low availability of labile organic carbon. In summer, the average denitrification rate was similar to 138 mu mol N m(-2) d(-1). The corresponding estuarine nitrogen removal for August was similar to 1.2 t, of which similar to 93% was removed by coupled nitrification-denitrification. Particulate matter in the estuary was mainly phytoplankton derived (> 70% in surface waters) and likely based on the riverine nitrate which was not removed by direct denitrification due to water column stratification. Subsequently settling particles served as a link be tween the otherwise uncoupled nitrate in surface waters and benthic nitrogen removal. We suggest that the riverine nitrate brought into the oligotrophic estuary during the spring flood is gradually, and with a time delay, removed by benthic denitrification after being temporarily ` trapped' in phytoplankton particulate matter. The oligotrophic system is not likely to face eutrophication from increasing nitrogen loading due to phosphorus limitation. In response, coupled nitrification-denitrification rates are likely to stay constant, which might increase the future export of nitrate to the open sea and decrease the estuary's function as a nitrogen sink relative to the load. |
Subject: |
1172 Environmental sciences
Coastal filter Northern Baltic Sea Nitrogen Sand sediment Particulate organic nitrogen Isotope pairing technique Quark Strait ANAEROBIC AMMONIUM OXIDATION ISOTOPE PAIRING TECHNIQUE STIRRED BENTHIC CHAMBERS COASTAL MARINE-SEDIMENTS NORTH-ATLANTIC OCEAN BALTIC SEA ORGANIC-MATTER NITROGEN BIOGEOCHEMISTRY PERMEABLE SEDIMENTS SEASONAL OXYGEN |
Peer reviewed: | Yes |
Rights: | cc_by |
Usage restriction: | openAccess |
Self-archived version: | publishedVersion |
Funder: | Unknown funder |
Grant number: |
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