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MEPS prepress abstract   -  DOI:

Role of vitamin B12 in the microbial plankton response to nutrient enrichment

Esther Barber-Lluch*, Marta Hernández-Ruiz, Antero Prieto, Emilio Fernández, Eva Teira

*Corresponding author:

ABSTRACT: In order to evaluate the role of vitamin B12 availability in microbial plankton communities, 10 microcosm experiments were performed where inorganic nutrients (nitrate, ammonium and phosphate) and vitamin B12 were added, separately or in combination, to surface seawater samples drawn from an on-shelf station over an annual cycle. The responses of both autotrophic and heterotrophic microbial plankton were highly variable. Vitamin B12 addition enhanced phytoplankton biomass in early spring (March and April) and autumn (October) and bacterial biomass in winter (January) and summer (June and September). Our data reinforce the idea that inorganic nutrient limitation experienced by autotrophic and heterotrophic microbial communities is mostly dependent on the initial background nutrient conditions. The single or secondary vitamin B12 limitation of phytoplankton growth implies that the availability of this molecule might modulate the increase in primary production associated with enhanced nitrogen loads to the ocean derived from human activities. These findings may have significant implications on carbon and nutrient cycling through the planktonic microbial compartments of coastal ecosystems.