An assessment of upper ocean carbon and nitrogen export fluxes on the boreal continental shelf: A 3-year study in the open Baltic Sea comparing sediment traps, 234Th proxy, nutrient, and oxygen budgets
2013 (English)In: Limnology and Oceanography: Methods, ISSN 1541-5856, E-ISSN 1541-5856, Vol. 11, 495-510 p.Article in journal (Refereed) Published
Six different approaches for estimating the upper ocean export of carbon and nitrogen has been assessed using 2-3 years of observations in the open Baltic Sea. The long-term average export ratios, relative to primary production, were similar from approaches based on upper ocean N budget (0.29 +/- 0.02), upper ocean O budget (0.25 +/- 0.02), collection-efficiency-corrected sediment traps (0.30 +/- 0.03), and Th-234-derived POC export (0.21 +/- 0.03; POC/Th-234 ratio from traps). Estimates of carbon export efficiency based on direct sediment traps (0.14 +/- 0.02) likely reflected under trapping whereas filter-based Th-234-derived POC export (0.86 +/- 0.03) indicated that POC/Th-234 ratio from filters were larger than the ratio on truly settling matter; these two approaches and estimates are thus not recommended. This study provides improved constraints on the upper ocean C and N export in offshore temperate-boreal continental shelf regimes such as the open Baltic Proper. The long-term export fluxes derived by averaging the four geochemically consistent yet independent approaches were for POC 44.6 +/- 4.0 gC m(-2) y(-1) and for PON 7.0 +/- 0.6 gN m(-2) y(-1). This multi-technique approach improves understanding of carbon and nitrogen cycling in the upper ocean by constraining the export efficiencies through comprehensive time-series measurements.
Place, publisher, year, edition, pages
2013. Vol. 11, 495-510 p.
Oceanography, Hydrology, Water Resources
Research subject Biogeochemistry
IdentifiersURN: urn:nbn:se:su:diva-97495DOI: 10.4319/lom.2013.11.495ISI: 000328880100002OAI: oai:DiVA.org:su-97495DiVA: diva2:681638
FunderEcosystem Approach to the Baltic Sea (Upphört/Closed 2010)Swedish Research Council, 1-AA/GB 12291-301Mistra - The Swedish Foundation for Strategic Environmental Research, 98538Mistra - The Swedish Foundation for Strategic Environmental Research, SUCOZOMASwedish Environmental Protection Agency, 212-0508