DOI: 10.5061/dryad.f1vhhmgw9
title: Data from: Microbial metabolic activity in two basins of the Gulf of Mexico influenced by mesoscale structures

description: Information on microbial metabolic activity is essential for quantifying
 carbon and energy flows through marine food webs. We quantified community
 (Rcom) and prokaryotic (Rpro) respiration rates, bacterial production
 (BP), bacterial abundance (BA), and bacterial growth efficiencies (BGE) in
 the Perdido and Coatzacoalcos basins of the Gulf of Mexico (GOM) during
 summer and winter conditions in 2016. Our results showed seasonal,
 regional, and mesoscale eddy influences on those metabolic variables. Rpro
 accounted for more than 60% of total respiration in both regions, being
 three times higher in stations influenced by a cyclonic eddy (CE) in
 September (24.1 μM O2 d-1) than in stations affected by an anticyclonic
 eddy in March (7.2 μM O2 d-1) within the Coatzacoalcos basin where the
 eddy-trapping mechanism advected biomass-enriched waters from the Bay of
 Campeche. The eddy-stirring mechanism produced horizontal and vertical
 dipole patterns of metabolic variables increasing up to one order of
 magnitude Rcom and Rpro while decreasing BGE to 25-fold from the
 southeastern to the northwestern edges in CEs. This finding indicates that
 dissolved organic matter is more actively taken up to build bacterial
 biomass on the eastern edge of CEs in the GOM, while respiration rates
 increase on the western edges. Satellite integrated primary production was
 coupled with surface respiration rates at CEs and no eddies. Bacterial
 production was mainly regulated by CEs and was about 50% higher in the
 Coatzacoalcos basin (~0.03–0.14 µmol C L-1 d-1). BP increased in zones
 with high respiration rates, suggesting that Rcom is associated with
 heterotrophic prokaryote activity in both basins. Bacterial growth
 efficiency was lower than 25% within the upper 500 m during both cruises,
 but the highest values were quantified in the euphotic zone and during the
 September cruise. Metabolic variables integrated over the water column
 showed that 40–80% of the activity occurred between the base of the
 euphotic zone and 150 m depth. Our findings contribute to a better
 understanding of the metabolic activity of the microbial communities in
 two regions of the GOM influenced by mesoscale eddies.
description: Water samples were collected with Niskin oceanographic bottles at
 five depth levels (0.1% and 30% light, maximum fluorescence, minimum
 oxygen, and 500 m) at three stations in each of the study basins, Perdido
 and Coatzacoalcos. <strong>CTD
 data</strong> Dissolved oxygen, practical
 salinity, and in-situ temperature data were acquired with a CTD instrument
 from surface to 500 m. <strong>Community and
 Bacterial Respiration Rates</strong> Water
 samples from different depth levels were incubated in triplicate in 100 mL
 BOD bottles previously rinsed with 3% hydrogen peroxide
 (H<sub>2</sub>O<sub>2</sub>) and fitted with
 oxygen-sensitive patches (SP-PSt3-NAU-YOP). Samples for assessing
 community respiration were collected directly from BOD bottles; samples
 for bacterial respiration were filtered through 1-µm pore size
 polycarbonate filters. All the bottles were incubated for 24 hours in the
 dark under a controlled temperature (18 ± 1 °C) (Bondyale-Juez et al.,
 2017).<br>Oxygen concentration at different times was recorded with
 optode sensors using the Fibox 4 system (PreSens, Regensburg, Germany)
 (Villegas-Mendoza et al., 2019). Oxygen optode sensors provide continuous
 measurements (at intervals of seconds to minutes) with high accuracy (±
 0.14–2.83 µmol and ± 1.4–283.1 µmol; 15 ppb detection limit). Bacterial
 growth efficiency was calculated as the ratio between bacterial production
 and (bacterial production plus bacterial respiration).
 <strong>Bacterial Abundance</strong>
 Bacterial abundance was determined in 10 mL samples from each
 depth; the samples were fixed with 2% formaldehyde solution. A 0.5–1.0 mL
 aliquot of the sample was incubated with DAPI and filtered immediately
 through 0.2 µm black polycarbonate filters (Poretics). Cells were counted
 with an Eclipse Ti-E inverted microscope (Nikon Instruments Inc.) and the
 image analysis software Nikon NIS-Elements (Kirchman D., 1993).
 <strong>Bacterial Production</strong>
 Bacterial production (BP) is the amount of organic carbon that
 becomes incorporated into cells per unit of time (Del Giorgio and
 Williams, 2007). It represents the potential flow of organic carbon from
 bacteria to the upper trophic levels (Azam, 1998). BP was determined by
 estimating protein synthesis with the micro-centrifugation technique
 developed by Smith and Azam (1992). Triplicate 1.5 mL water samples were
 spiked with <sup>3</sup>H-leucine (Perkin Elmer, specific
 activity 123 Ci mmol<sup>-1</sup>) and incubated for 5–7 hours
 in the dark at 18 °C; 100 μL of cold 100% TCA were spiked into the control
 replicates. Afterward, 1 mL of EcoLume liquid scintillation cocktail (MP
 Biomedicals) was added and mixed; bacterial 3H emission was measured on a
 liquid scintillation counter (Beckman LS6500). A constant 0.073 value for
 the leucine/protein fraction was used, assuming that leucine is not
 transformed into other amino acids. This value was multiplied by the
 leucine molecular weight (131.2 g mol<sup>-1</sup>), by the
 carbon-protein cell ratio (0.86), and by the isotopic dilution (2) (Smith
 and Azam, 1992). <strong>Bacterial Growth
 Efficiency</strong> Bacterial growth efficiency
 (BGE) was calculated as was reported for the Gulf of Mexico by Biddanda
 and Benner (1997). <strong>Respiration per
 Cell</strong> Respiration per cell was calculated
 by dividing the prokaryotic respiration rate by the bacterial
 abundance
 <strong>References</strong> *
 Biddanda, B., Benner, R., 1997. Major contribution from mesopelagic
 plankton to heterotrophic metabolism in the upper ocean. Deep Sea Res.
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 * Bondyale-Juez, D. R., Packard, T. T., Viera-Rodríguez, M. A.,
 & Gómez, M. (2017). Respiration: comparison of the Winkler
 technique, O2 electrodes, O2 optodes and the respiratory electron
 transport system assay. Marine Biology, 164(12), 1–11.
 https://doi.org/10.1007/s00227-017-3271-1 * Del
 Giorgio, P., Williams, P., 2007. Respiration in Aquatic Ecosystems,
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 (1992). A simple, economical method for measuring bacterial protein
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 http://scrippsscholars.ucsd.edu/fazam/content/simple-economical-method-measuring-bacterial-protein-synthesis-rates-seawater-using-3h-leucine * Villegas-Mendoza, J., Cajal-Medrano, R., & Maske, H. (2019). The Chemical Transformation of the Cellular Toxin INT (2-(4-Iodophenyl)-3-(4-Nitrophenyl)-5-(Phenyl) Tetrazolium Chloride) as an Indicator of Prior Respiratory Activity in Aquatic Bacteria. International journal of molecular sciences, 20(3), 782. https://doi.org/10.3390/ijms20030782
description: This is a contribution of the Consorcio de Investigación del
 Golfo de México (CIGOM). We thankfully acknowledge the specific request
 placed by PEMEX to the Hydrocarbon Fund to address the environmental
 effects of oil spills in the Gulf of Mexico. This study was funded by the
 Hydrocarbon Fund of Consejo Nacional de Ciencia y Tecnología – Secretaría
 de Energía, through grants No. 201441 and No. 201441, and by Secretaría de
 Educación Pública through grants SEP UABC‐PTC‐702: 511‐6/17‐8051 (to Josué
 Villegas-Mendoza) and grant PRODEP 511-6/2019.-11768 (to Eliana
 Gómez-Ocampo) (CIGoM; http://www.cigom.info/).