Vertical diatom flux observed in sediment traps in the Arctic Ocean with special emphasis on Melosira arctica

• Main Authors: Nöthig, Eva-Maria, Bauerfeind, Eduard, Lalande, Catherine, Shevchenko, Vladimir, Zernova, V. V.
• Format: Conference Object
• Language: unknown
• Published: 2015
• Subjects: Arctic; Arctic Ocean; Gakkel Ridge; Laptev Sea; laptev; Lomonosov Ridge; Nansen Basin; Sea ice
• Online Access: https://epic.awi.de/id/eprint/37633/; https://epic.awi.de/id/eprint/37633/1/Noethig_et_al_M_arctica_in_sediment_traps_central_AO.pdf; https://hdl.handle.net/10013/epic.45264; https://hdl.handle.net/10013/epic.45264.d001

Vertical particle flux has been investigated by means of two moored sediment trap arrays each deployed over a one-year-period from mid September to mid August in the northern Laptev Sea (close to the Lomonosov Ridge at 150m and 1550m) during 1995 -1996 and in the Nansen Basin (close to the Gakkel Ridge at 200m and 3800m) during 2011-2012, respectively. Although the moorings where deployed with a time span of 16 years in different regions of the Arctic Ocean, vertical particle flux patterns of dominating diatom species were fairly similar. In both sediment trap arrays sea ice related diatoms prevailed in the samples. Melosira arctica dominated the diatom cell flux in numbers as well as in biomass. When M. arctica started to sink down long chains were observed during the month of July. For weeks later very short chains mainly consisting of resting spores were found in the trap samples. In the deep trap in the Nansen Basin less resting spores but more slimy Melosira aggregates were found than in the trap deployed at 200m. Other large diatom species found in higher quantities were Nitzschia frigida and Fragilariopsis oceanica. Nitzschia frigida cells were sinking predominantly as single cells, however, sedimentation started earlier and with higher numbers in the Nansen Basin during 2011-2012 than 16 years before in the northern Laptev Sea. Less frequently occurring species found belong to the genus Navicula, Pseudo-nitzschia, Pleurosigma, Gyrosigma and Haslea. Generally the vertical flux of organic matter was lower in the Nansen Basin than in the northern Laptev Sea. The onset of increased algal downward transport occurred about 2 weeks earlier (June 1st) during the sampling period 2011-2012. From our findings we conclude that the progressively earlier ice melt affected more the export fluxes of biogenic matter than the ice related algal species in the region.