Biogeochemical Cycling of Selenium in the Arctic Ocean

• Main Author: McQuiggan, Kyle M.
• Format: Text
• Language: unknown
• Published: ODU Digital Commons 2018
• Subjects: Arctic; GEOTRACES; Ocean; Selenium; Biogeochemistry; Chemistry; Environmental Sciences; Oceanography; Arctic Ocean; Canada; Makarov Basin; North Pole; canada basin; makarov basin; Phytoplankton; Alaska
• Online Access: https://digitalcommons.odu.edu/oeas_etds/83; https://digitalcommons.odu.edu/cgi/viewcontent.cgi?article=1083&context=oeas_etds

Changes in the global climate may have a pronounced effect on the biogeochemical cycling of trace elements like selenium (Se) in the Arctic Ocean. This study described the first quantitative examination of the biogeochemical cycle of selenium in the Amerasian Basin, providing the baseline from which future changes can be identified. Aerosol, dissolved and particulate water samples were collected for Se determinations during the U.S. GEOTRACES GN01 Arctic expedition that sampled the two parts of the Amerasian Basin in 2015: The Makarov Basin on the way to the North Pole and the Canada Basin on the return trip to Dutch Harbor, Alaska. Particulate Se concentrations were low throughout the cruise with the highest concentrations occurring at the bottom depths of the shallow shelf stations (0.06 nM). Particulate Se to particulate organic carbon atomic ratios were around phytoplankton ratios (~10-6) on the shelf, but were elevated (10-5) in the basin. Aerosol Se concentrations were low (0.01 – 0.11 nmol m-3, n=13), but enrichment factors were elevated and ranged from 1540 to 66698, suggesting distant fossil fuel combustion or local gaseous sources such as marine biogenic release of dimethyl selenide as a dominant source of aerosol Se. Generally, the depth profiles of the dissolved Se species did not resemble those of nutrient-like profiles seen in other ocean basins. Prediction of selenite and selenate concentrations using silicate and phosphate concentrations, shown to be accurate in other oceans, tended to overestimate selenate and underestimate selenite concentration throughout the Amerasian Basin. This lack of agreement suggests a slower than normal oxidation rate from selenite to selenate. Estimated fluxes of total dissolved Se indicate that 1.0 ± 0.5 x 108 mol Se enter and 1.0 ± 0.1 x 108 mol Se leave the Amerasian Basin each year. The Atlantic Ocean is the dominant factor in both input and removal of water to and from the Arctic. Therefore, it likely plays a major role in the Se budget of the Arctic and future ...