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Deposition, return flux, and burial rates of nitrogen and phosphorus in the sediments of two high-Arctic fjords

Koziorowska K., Kuliński K., Pempkowiak J.

Oceanologia

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2018

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No. 60 (4)

431--445

EN

The aim of this study was to determine the burial rates of nitrogen (N) and phosphorus (P) in the sediments of two high-latitude fjords: Hornsund and Kongsfjorden (Spitsbergen). Both deposition to sediments and the return flux from sediments to the water column of the various species of these elements were, therefore, quantified. The burial rate was then calculated as the difference between deposition and return flux. The required concentrations of N and P species were measured in surface sediments, in pore water extracted from the sediments, and in the above-bottom water at sampling stations situated along the axes of the fjords. Annual deposition to sediments ranged between 2.3-8.3 g m−2 for N and 0.9-2.8 g m−2 for P. The nitrogen return fluxes ranged from 0.12 to 1.46 g m−2 y−1. At most stations, the N flux was predominantly of dissolved organic (about 60-70%) rather than inorganic N. The P return flux varied between 0.01 and 0.11 g m−2 y−1, with organic species constituting 60-97%. The N and P burial rates differed between fjords: 2.3-7.9 g N m−2 y−1 and 0.9-2.8 g P m−2 y−1 in Hornsund vs. 0.9-1.3 N g m−2 y−1 and 1.0-1.2 g P m−2 y−1 in Kongsfjorden. This was accompanied by a different efficiency of N and P burial – higher in Hornsund than in Kongsfjorden, in both cases. This suggests differences in the quality and quantity of N and P organic species deposited to sediments and therefore differences in the intensity of their mineralization and/or decomposition.

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Kongsfjorden and Hornsund hydrography : comparative study based on a multiyear survey in fjords of west Spitsbergen

Promińska A., Cisek M., Walczowski W.

Oceanologia

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2017

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No. 59 (4)

397--412

EN

A recent study has shown increased warming in the fjords of west Spitsbergen. Their location is critical, as they are situated along the main northward pathway of Atlantic Water (AW) which is a great source of heat to the Arctic Ocean and the fjords. In the light of ongoing warming, we aim to discuss differences between the fjords under northward transformation of oceanic waters. We compared summer hydrographic conditions in two fjords located in two opposite ends of west Spistbergen: Hornsund in the south and Kongsfjorden in the north. The study is based on high resolution CTD measurements collected during Arctic cruises between 2001 and 2015. The emphasis was put not only on differences in water temperature, salinity and water masses but also the freshwater content (FWC), AW transport and heat delivery to the fjords. In general, the water in Kongsfjorden is on average 1°C warmer and its salinity is higher by 0.5 compared to Hornsund. It is also characterized by two times greater transport of AW and heat delivery to the fjord. On the other hand, Hornsund reveals two times higher FWC. Both fjords undergo a gradual warming due to an increased presence of Atlantic origin waters. The ongoing warming is accompanied by an increase in variability of temperature and salinity dependent on the domination of the Sørkapp Current (SC) or the West Spitsbergen Current (WSC) on the West Spitsbergen Shelf (WSS). Nonetheless, Hornsund remains more Arctic-type fjord compared to Kongsfjorden, due to stronger blocking by SC.

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Comparison of bacterial production in the water column between two Arctic fjords, Hornsund and Kongsfjorden (West Spitsbergen)

Ameryk A., Jankowska K. M., Kalinowska A., Węsławski J. M.

Oceanologia

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2017

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No. 59 (4)

496--507

EN

Bacterial production and the accompanying environmental factors were measured in the water columns of two Arctic fjords during the cruise in July and August 2013. Water samples were collected at six stations located in the central part of Hornsund and Kongsfjorden. In Hornsund, where average water temperatures were 1.25-fold lower than in Kongsfjorden, the bacterial production was twice as high (0.116 ± 0.102 vs 0.05 ± 0.03 mg C m−3 h−1). Statistical analysis indicated that chlorophyll a concentration itself was not a significant factor that affected bacterial production, in contrast to its decomposition product, pheophytin, originating from senescent algal cells or herbivorous activity of zooplankton. Single and multiple regression analysis revealed that water temperature, dissolved organic carbon (DOC), and pheophytin concentration were the main factors affecting bacterial production in both fjords.