Biogenic silica production and diatom dynamics in the Svalbard region during spring
byJeffrey W. Krause, Carlos M. Duarte, Israel A. Marquez, Philipp Assmy, Mar Fernández-Méndez, Ingrid Wiedmann, Svein Kristiansen, Susana Agusti
Krause, J. W., Duarte, C. M., Marquez, I. A., Assmy, P., Fernández-Méndez, M., Wiedmann, I., ... & Agustí, S. (2018). Biogenic silica production and diatom dynamics in the Svalbard region during spring. Biogeosciences, 15(21), 6503-6517.
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.