Relationships between Respiration Rates of Marine Microbial Communities and Physical Oceanographic Conditions of Gulf of Mexico (GM)

Diana Rodriguez Escobar, Universidad Autónoma de Baja California, Facultad de Ciencias Marinas, Ensenada, BJ, Mexico, Josue Villegas-Mendoza, Autonomous University of Baja California, Marine Science Faculty, Ensenada, BJ, Mexico, Mary Carmen Ruiz-de la Torre, Autonomous University of Baja California, Marine Science Faculty, Mexicali, BJ, Mexico and Eliana Gómez-Ocampo, Centro de Investigación Científica y Educación Superior de Ensenada, CICESE, Ecologia Marina, Ensenada, BJ, Mexico
Abstract:

The world database of aquatic respiration is limited with spatial and temporal biases (Robinson 2019). The respiration rates of the planktonic (Rcom) and prokaryotic (Rpro) community were quantified by the oxygen consumption rate using Planar Oxygen-Sensitive Spots (SP-PSt3-NAU-YOP). In 2016, during spring and fall, samples were collected (from 20 to 500 m in a gradient coastal to open ocean waters) at Perdido and Coatzacoalcos Basins in Gulf of Mexico. Bacterial abundance was determined by epifluorescence microscopy and bacterial production with 3H-leucine incorporation. We associated Rcom and Rpro with primary production (by VGPM model) and physical variables such as altimetry, temperature, salinity, and dissolved oxygen. During spring the surface temperature varied from 22 to 24 °C. We observed a higher primary production (0.5 to 1.0 g C m-2 d-1) than fall (0.2 to 0.5 g C m-2 d-1), the high surface temperature remained (30 to 31°C), and anticyclonic eddy was maintained showing lower dissolved oxygen (2.25 to 4 mL L-1) than spring (2.7 to 5.2 mL L-1). Coatzacoalcos basin showed higher respiration rates (24 μmol O2 L-1 day-1) than Perdido (5.5 μmol O2 L-1 day-1) during autumn, Rpro was three times higher than spring (7.2 μmol O2 L-1 day-1). Our results suggest that the average Rpro represents until 75 % of the Rcom (y = 1.08x + 0.33, R² = 0.90, p = 0.05). In Perdido, the respiration increased towards the coastal areas, while for Coatzacoalcos was maximum in the open ocean, and the bacterial production was associated with high respiration rates. The highest bacterial production was found in Coatzacoalcos during the fall (1.86 µg C L-1 day-1), while for spring bacterial production was relatively low (1.3 µg C L-1 day-1) suggesting that in both basins Rcom and Rpro were associated with activity of heterotrophic prokaryotes presenting a decoupling with primary production.

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