Biogeochemical characterization of pennate diatom and Melosira arctica ice algal aggregates in the Central Arctic Ocean collected in summer 2011 and 2012

• Main Authors: Fernández-Méndez, Mar, Wenzhöfer, Frank, Peeken, Ilka, Sørensen, Heidi L, Glud, Ronnie N, Hendricks, Stefan, Nicolaus, Marcel, Katlein, Christian, Nöthig, Eva-Maria, Bakker, Karel, Boetius, Antje
• Format: Dataset
• Language: English
• Published: PANGAEA 2014
• Subjects: ABYSS; Algae aggregate; size; Arctic Ocean; ARK-XXVI/3; ARK-XXVII/3; Assessment of bacterial life and matter cycling in deep-sea surface sediments; AWI_BioOce; Bacterial organic carbon normalized to particulate organic carbon; Biological Oceanography @ AWI; Carbon; organic; dissolved normalized to particulate organic carbon; particulate; Carbon/Chlorophyll a ratio; Carbon/Nitrogen ratio; Chlorophyll a/chloroplastic pigment equivalents ratio; Chlorophyll a normalized to particulate organic carbon; Color description; Comment; Date/Time of event; Description; Event label; Gear; Habitat; ICE; Ice station; Ice station #1; Ice station #2; Ice station #3; Ice station #4; Ice station #5; Ice station #7; Irradiance; Latitude of event; Life stage; Longitude of event; Melt pond coverage on sea ice; Melt pond depth; Method comment; Net primary production of carbon normalized to particulate organic carbon; Nitrate; Normalized to particulate organic carbon; Number of measurements; Optional event label; Partical organic nitrogen normalized to particulate organic carbon; Phosphate; Polarstern; Arctic; Sea ice
• Online Access: https://doi.pangaea.de/10.1594/PANGAEA.832345; https://doi.org/10.1594/PANGAEA.832345

Sea-ice diatoms are known to accumulate in large aggregates in and under the sea ice including melt ponds. In the Arctic, they can contribute substantially to particle export when sinking from the ice. The role and regulation of microbial aggregation in the highly seasonal, nutrient- and light-limited Arctic sea-ice ecosystem is not yet well understood, and may vary in relation to the fate of the Arctic sea-ice cover. To elucidate the mechanism controlling the formation and export of algal aggregates from sea ice, we investigated samples taken in late summer 2011 and 2012, during two cruises to the Eurasian Basin of the Central Arctic Ocean. Dense, spherical aggregates composed mainly of pennate diatoms, and filamentous aggregates formed by Melosira arctica were found in different degradation stages, with carbon to Chlorophyll a ratios ranging from 110 to 66700, and carbon to nitrogen molar ratios of 8-35 and 9-40, respectively. Fresh sub-ice algal aggregate densities ranged between 1 and 17 aggregates/m**2, corresponding to a net primary production of 0.4-40 mg C/m**2/d, contributing 3-80% of total biomass and up to 94% of total production at a local scale. A key factor controlling buoyancy of the aggregates was light intensity, regulating photosynthetic oxygen production and flotation by gas bubbles trapped within the mucous matrix, even at low ambient nutrient concentrations. Our data was used to evaluate the factors regulating the distribution and importance of the Arctic algal aggregates as carbon source for pelagic and benthic communities.