Biogeosciences: Biogenic silica production and diatom dynamics in the Svalbard region during spring

The journal Biogeosciences has published the article titled “Biogenic silica production and diatom dynamics in the Svalbard region during spring”, authored by Jeffrey W. Krause1,2, Carlos M. Duarte3,4, Israel A. Marquez1,2, Philipp Assmy5,Mar Fernández-Méndez5, Ingrid Wiedmann6, Paul Wassmann6, Svein Kristiansen6,and Susana Agustí3

1Dauphin Island Sea Lab, Dauphin Island, USA; 2Department of Marine Sciences, University of South Alabama, Mobile, USA; 3King Abdullah University of Science and Technology, Thuwal, Saudi Arabia; 4Arctic Research Centre, Department of Bioscience, Aarhus University, Aarhus, Denmark; 5Norwegian Polar Institute, Tromsø, Norway; 6Department of Arctic and Marine Biology, UiT The Arctic University of Norway, Tromsø, Norway.

Abstract: 

Diatoms are generally the dominant contributors to the Arctic Ocean spring bloom, which is a key event in regional food webs in terms of capacity for secondary production and organic matter export. Dissolved silicic acid is an obligate nutrient for diatoms and has been declining in the European Arctic since the early 1990s. The lack of regional silicon cycling information precludes understanding the consequences of such changes for diatom productivity during the Arctic spring bloom. This study communicates the results from a cruise in the European Arctic around Svalbard, which reports the first concurrent data on biogenic silica production and export, export of diatom cells, the degree of kinetic limitation by ambient silicic acid, and diatom contribution to primary production. Regional biogenic silica production rates were significantly lower than those achievable in the Southern Ocean and silicic acid concentration limited the biogenic silica production rate in 95% of samples. Compared to diatoms in the Atlantic subtropical gyre, regional diatoms are less adapted for silicic acid uptake at low concentration, and at some stations during the present study, silicon kinetic limitation may have been intense enough to limit diatom growth. Thus, silicic acid can play a critical role in diatom spring bloom dynamics. The diatom contribution to primary production was variable, ranging from  < 10% to  ∼ 100% depending on the bloom stage and phytoplankton composition. While there was agreement with previous studies regarding the export rate of diatom cells, we observed significantly elevated biogenic silica export. Such a discrepancy can be resolved if a higher fraction of the diatom material exported during our study was modified by zooplankton grazers. This study provides the most direct evidence to date suggesting the important coupling of the silicon and carbon cycles during the spring bloom in the European Arctic.

Reference: 

Krause, J. W., Duarte, C. M., Marquez, I. A., Assmy, P., Fernández-Méndez, M., Wiedmann, I., Wassmann, P., Kristiansen, S., and Agustí, S. (2018): Biogenic silica production and diatom dynamics in the Svalbard region during spring. Biogeosciences, 15, 6503-6517, DOI: 10.5194/bg-15-6503-2018. [intranet]