Vitamin B12 and the microbial heterotrophic and autotrophic metabolism in two regions influence by the California current.

Josue Villegas-Mendoza1, Mary Carmen Ruiz-de la Torre2, Karina Lugo-Ibarra3, Diana Rodriguez Escobar3 and Andrés Cano-Suzan4, (1)Autonomous University of Baja California, Marine Science Faculty, Ensenada, BJ, Mexico, (2)Autonomous University of Baja California, Marine Science Faculty, Mexicali, BJ, Mexico, (3)Universidad Autónoma de Baja California, Facultad de Ciencias Marinas, Ensenada, BJ, Mexico, (4)Universidad Autónoma de Baja, Facultad de Ciencias Marinas, Ensenada, BJ, Mexico
Abstract:
Vitamin B12 can be a growth regulator of phytoplankton and bacterioplankton. It is not clear how the B12 demand of the microbial communities is supplied in the microbial communities. Measurements of B12 in the ocean indicated offshore sub-picomolar concentrations and in coastal regions picomolar concentrations. In the present study, we related the coupling between the dissolved B12 and the microbial heterotrophic and autotrophic metabolism in two regions influence by the California current (a station with mesotrophic conditions and a coastal lagoon with eutrophic conditions) in which economic activities are developed. We measured hydrographic conditions (CTD, RBR maestro), bacterial and phytoplankton abundance (DAPI, Utermöhl), B12 concentration (dissolved and particulate), primary production (C13 assimilation), respiration rate of prokaryotes (Rpro) and planktonic community (Rcom) (oxygen consumption, optode DP-PSt3-YOP). Different depths were sampled (0.1%, 30% light, maximum fluorescence and 150 m) during September 2018 and March 2019. Respiratory activity was dominated by prokaryotic activity. In 2018, Rpro and Rcom were ranged between 0.9 to 13.5 and 0.9 to 7.5 µmol O2 L-1 day-1, respectively. In 2019, Rpro was three times higher (40.7 µmol O2 L-1 day-1) than to 2018. In the coastal lagoon, in 2018 Rpro and Rcom were ranged between 22.6 to 90.3 and 2.1 to 10.2 µmol O2 L-1 day-1, respectively. In 2019, B12 was added (200 and 400 pmol B12 L-1) to natural samples, data showed an increase at least 8 times (0.46 to 4.79 and 0.59 to 5.22 µmol O2 L-1 day-1) of the Rpro and Rcom, respectively. In the lagoon station phytoplankton community were represented by diatoms Pseudonutzchia australis (Chla 2.33 mg m-3, 5.6 x 104 cells ml-1) a biotoxin producer algae. Our preliminary results suggest that the respiratory activity is related to the own productivity of each examined site since the B12 availability is an essential component of dynamics of the microbial communities.
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