Short-term biogenic particle flux under late spring sea ice in the western Weddell Sea

• Published in: Deep Sea Research Part II: Topical Studies in Oceanography
• Main Authors: Michels, Jan, Dieckmann, G. S., Thomas, D., Schnack-Schiel, S. B., Krell, A., Assmy, P., Kennedy, H., Papadimitriou, S., Cisewski, B.
• Format: Article in Journal/Newspaper
• Language: English
• Published: Elsevier 2008
• Subjects: Weddell; Weddell Sea; Antarc*; Antarctica; Sea ice
• Online Access: https://oceanrep.geomar.de/id/eprint/27102/; https://oceanrep.geomar.de/id/eprint/27102/1/short-term-biogenic.pdf; https://doi.org/10.1016/j.dsr2.2007.12.019

In the framework of the “Ice Station POLarstern” (ISPOL) expedition in the western Weddell Sea, two sediment traps were deployed at 10 and 70 m water depth under a drifting ice floe in December 2004. The amount and composition of the vertical particle flux under sea ice were determined during a period of 30 days in order to investigate the influence of biological processes in sea ice and on its underside on the flux. The total mass flux was dominated by diatoms, faecal material, and aggregates, and ranged from 95.28 to 197.67 mg m−2 d−1 at 10 m depth and from 51.54 to 55.34 mg m−2 d−1 at 70 m depth. A strong increase with time of the flux of chlorophyll equivalents, biogenic silica, and faecal material was recorded during the observation period, coincident with the increase in the concentration of chlorophyll a in the bottom ice layer above the trap array. The latter suggests a concomitant increase in the amount of food available for grazers, such as krill, in the bottom ice layer and on the underside of the ice floe, resulting in an increased downward transport of ice-algal material into the water column. The sinking faecal material was dominated by krill faecal strings and contained large amounts of diatom frustule debris, as well as intact diatom frustules, mainly of the species Fragilariopsis curta and F. cylindrus. Single pronounced flux events of Phaeocystis antarctica and aggregates were also observed early in the study period. Low POC/PON and biogenic silica/POC ratios of the sinking particulate matter suggest that the material collected in the traps was relatively fresh.