English (United Kingdom)

https://curated-unify.zendy.io/wp-json/zendy-region/v1/featured_content/oa?rat=en

https://curated-unify.zendy.io/wp-json/zendy-region/v1/highlighted_journal/

Global: Zendy Tools annual

Presents the keyphrase highlighting as premium feature

Keyphrase Highlighting

Presents the summarisation as premium feature

Summarisation

Insights

Presents the pdf analysis as premium feature

PDF Analysis

Presents the zaia usage as premium feature

ZAIA

Global: Zendy Tools monthly

Global: Zendy Plus monthly

Presents the access of premium content as premium feature

Premium Content

Global: Zendy Plus annual

Global: Zendy Free Plan

Abstract. Particle sinking is a major form of transport for photosynthetically fixedcarbon to below the euphotic zone via the biological carbon pump (BCP).Oxygen (O2) depletion may improve the efficiency of the BCP.However, the mechanisms by which O2 deficiency can enhanceparticulate organic matter (POM) vertical fluxes are not well understood.Here, we investigate the composition and vertical fluxes of POM in two deepbasins of the Baltic Sea (GB: Gotland Basin and LD: Landsort Deep). The twobasins showed different O2 regimes resulting from the intrusion ofoxygen-rich water from the North Sea that ventilated the water column below140 m in GB, but not in LD, during the time of sampling. In June 2015, wedeployed surface-tethered drifting sediment traps in oxic surface waters (GB:40 and 60 m; LD: 40 and 55 m), within the oxygen minimum zone (OMZ; GB:110 m and LD: 110 and 180 m) and at recently oxygenated waters by the NorthSea inflow in GB (180 m). The primary objective of this study was to testthe hypothesis that the different O2 conditions in the water columnof GB and LD affected the composition and vertical flux of sinking particlesand caused differences in export efficiency between those two basins. The composition and vertical flux of sinking particles were different in GB andLD. In GB, particulate organic carbon (POC) flux was 18 % lower in theshallowest trap (40 m) than in the deepest sediment trap (at 180 m).Particulate nitrogen (PN) and Coomassie stainable particle (CSP) fluxesdecreased with depth, while particulate organic phosphorus (POP), biogenicsilicate (BSi), chlorophyll a (Chl a) and transparent exopolymeric particle(TEP) fluxes peaked within the core of the OMZ (110 m); this coincided withthe presence of manganese oxide-like (MnOx-like) particles aggregated withorganic matter. In LD, vertical fluxes of POC, PN and CSPs decreased by 28 %,42 % and 56 %, respectively, from the surface to deep waters. POP, BSi andTEP fluxes did not decrease continuously with depth, but they were higher at110 m. Although we observe a higher vertical flux of POP, BSi and TEPscoinciding with abundant MnOx-like particles at 110 m in both basins, thepeak in the vertical flux of POM and MnOx-like particles was much higher inGB than in LD. Sinking particles were remarkably enriched in BSi, indicatingthat diatoms were preferentially included in sinking aggregates and/or therewas an inclusion of lithogenic Si (scavenged into sinking particles) in ouranalysis. During this study, the POC transfer efficiency (POC flux at 180 mover 40 m) was higher in GB (115 %) than in LD (69 %), suggesting thatunder anoxic conditions a smaller portion of the POC exported below theeuphotic zone was transferred to 180 m than under reoxygenated conditionspresent in GB. In addition, the vertical fluxes of MnOx-like particles were2 orders of magnitude higher in GB than LD. Our results suggest thatPOM aggregates with MnOx-like particles formed after the inflow ofoxygen-rich water into GB, and the formation of those MnOx–OM-rich particles mayalter the composition and vertical flux of POM, potentially contributing toa higher transfer efficiency of POC in GB. This idea is consistent withobservations of fresher and less degraded organic matter in deep waters ofGB than LD.

biogeosciences

Composition and vertical flux of particulate organic matter to the oxygen minimum zone of the central Baltic Sea: impact of a sporadic North Sea inflow