Details

Autor(en) / Beteiligte

• Mason, Robert P.
• Soerensen, Anne L.
• DiMento, Brian P.
• Balcom, Prentiss H.

Titel

The Global Marine Selenium Cycle: Insights From Measurements and Modeling

Ist Teil von

• Global biogeochemical cycles, 2018-12, Vol.32 (12), p.1720-1737

Ort / Verlag

Washington: Blackwell Publishing Ltd

Erscheinungsjahr

2018

Quelle

Wiley Online Library

Beschreibungen/Notizen

• Anthropogenic activities have increased the selenium (Se) concentration in the biosphere, but the overall impact on the ocean has not been examined. While Se is an essential nutrient for microorganisms, there is little information on the impact of biological processes on the concentration and speciation of Se in the ocean. Additionally, other factors controlling the distribution and concentration of Se species are poorly understood. Here we present data gathered in the subtropical Pacific Ocean during a cruise in 2011, and we used these field data and the literature, as well as laboratory photochemical experiments examining the stability and degradation of inorganic Se (both Se (IV) and Se (VI)) and dimethyl selenide, to further constrain the cycling of Se in the upper ocean. We also developed a multibox model for the biosphere to examine the impact of anthropogenic emissions on the concentration and distribution of Se in the ocean. The model concurs with the field data indicating that the Se concentration has increased in the upper ocean waters over the past 30 years. Our observational studies and model results suggest that Se (VI) is taken up by phytoplankton in the surface ocean, in contrast to the results of laboratory culture experiments. In conclusion, while anthropogenic inputs have markedly increased Se in the atmosphere (42%) and net deposition to the ocean (38%) and terrestrial landscape (41%), the impact on Se in the ocean is small (3% increase in the upper ocean). This minimal response reflects its long marine residence time. Plain Language Summary We measured selenium in water and particles during a cruise in the Pacific Ocean and use this data along with laboratory photochemcial experiments to examine the formation and degradation of the various Se forms in the upper ocean. We also developed a box model to examine how anthropogenic activities have changed the Se concentration throughout the ocean the potential future impacts and to highlight areas of Se biogeochemistry that need further study. Key Points Anthropogenic inputs have increased the concentration of selenium in the upper ocean in the last 40 years Photochemical degradation of methylated selenium in surface waters decreases the loss of selenium to the atmosphere via gas exchange Model results suggest that biological reduction of selenate is occurring in the surface ocean and is an important sink for oxidized selenium