Dataset: Bacterial abundance, bacterial organic carbon, and total organic carbon from remineralization bioassays conducted on R/V Robert Gordon Sproul cruises along the Southern California coast during July and August 2023

ValidatedFinal no updates expectedDOI: 10.26008/1912/bco-dmo.953702.1Version 1 (2025-02-18)Dataset Type:Cruise Results

Principal Investigator: Nicholas Baetge (Oregon State University)

Scientist: Craig A. Carlson (University of California-Santa Barbara)

Scientist: Jason Graff (Oregon State University)

Scientist: Allen J. Milligan (Oregon State University)

Student: Parker Hansen (Oklahoma State University)

Student: Brian Ver Wey (Oregon State University)

Technician: Elisa Halewood (University of California-Santa Barbara)

Technician: Keri Opalk (University of California-Santa Barbara)

BCO-DMO Data Manager: Shannon Rauch (Woods Hole Oceanographic Institution)


Project: Postdoctoral Fellowship: OCE-PRF: Smoke on the water: the impacts of wildfire ash deposition on surface ocean biology (Smoke on the water)


Abstract

These data include bacterial abundance, bacterial organic carbon, and total organic carbon from remineralization bioassays conducted to assess bacterioplankton growth and DOC degradation. Experiments were conducted on cruises aboard the R/V Robert Gordon Sproul (SP2319, SP2320) between dates 2023-07-28 and 2023-08-19 along the Southern California coast. Deposition of wildfire ash on the ocean can fertilize microbial production but also has the potential to inhibit microbial growth due to hea...

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All surface seawater was collected just prior to local sunrise from a SBE-911+ Conductivity-Temperature-Depth (CTD, Sea-Bird Scientific) Niskin bottle rosette cast and then transferred or directly filtered into acid-cleaned 20-liter (L) carboys with platinum-cured silicone tubing.

Bacterial growth and dissolved organic carbon (DOC) utilization were estimated in six microbial remineralization experiments following Baetge et al (2021), in which changes in bacterioplankton cell densities, bacterial organic carbon, and TOC were measured over five day incubations. For each experiment, 3-micrometer (µm) filtered surface seawater was directly and gently gravity-filtered through a mixed cellulose ester (MCE) membrane filter (EMD Millipore, 142-millimeters (mm)) in a polycarbonate filtration cartridge (Geotech Environmental Equipment, Inc.) with platinum-cured silicone tubing. The filtrate was then filtered through a 1.2- or a 0.2-µm MCE filter (EMD Millipore, 142 mm) to generate a bacterial inoculum or DOC media, respectively. Experiments were initiated when filtrates were mixed in a ratio of 1:4 bacterial inoculum to DOC media. Mixed seawater either remained unamended or was amended with ash leachate prior to being divided into a modified acid-washed 5 L polycarbonate bottle (Biotainer, Nalgene) (Baetge et al., 2021) and a set of 18 pre-combusted 40-milliliter (ml) EPA vials. Ash leachate DOC was added to experimental treatments at a final amendment concentration of ~4 µmol C/L Bottles and vials were incubated in the dark within ± 2 degrees Celsius (C) of in situ temperatures using wine coolers (YEG-2WS24-HD, YEEGO).

For each experiment, 2 ml samples for bacterial abundance were collected daily from all incubations. Triplicate 40 ml EPA vials were preserved daily as total organic carbon (TOC )samples after acidification to a pH of < 3 with 4 N HCl. Bacterial organic carbon (BOC) samples were collected in triplicate 1 L polycarbonate bottles from the bacterial inoculum and as samples from the 5 L polycarbonate bottles on the second and fifth days of the experiment. Bacterioplankton abundance (cells/L) samples were fixed upon collection with paraformaldehyde to a final concentration of 1%, flash-frozen in liquid nitrogen, and stored at -20 degrees C. Sample volumes for BOC (micromoles C per liter (µmol C/L)) measurements were filtered through two stacked pre-combusted 0.3 µm GF/75 filters (25 mm, Advantec) in inline polypropylene cartridges (Cole-Parmer). At three experimental sites, DOC media (i.e., 0.2 µm filtrate) was also filtered to generate triplicate background correction samples to account for DOC filter adsorption (Graff et al., 2023). All filters were stored in pre-combusted 20 ml borosilicate glass vials (Wheaton) at -20 degrees C, and then later fumed for 24 hours with HCl and dried for 24 hours at 50 degrees C prior to analysis.


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Results

Baetge, N., Halsey, K.H., Hanan, E.J., Behrenfeld, M.J., Milligan, A.J., Graff, J.R., Hansen, P., Carlson, C.A., Boiteau, R.B., Arrington, E.A., Comstock, J., Halewood, E.R., Harvey, E.L., Nelson, N.B., Opalk, K., Very Wey, B. (in review). Pre-existing in situ conditions shape coastal plankton response to fire-generated ash leachate. Limnology and Oceanography
Methods

Baetge, N., Behrenfeld, M. J., Fox, J., Halsey, K. H., Mojica, K. D. A., Novoa, A., Stephens, B. M., & Carlson, C. A. (2021). The Seasonal Flux and Fate of Dissolved Organic Carbon Through Bacterioplankton in the Western North Atlantic. Frontiers in Microbiology, 12. https://doi.org/10.3389/fmicb.2021.669883
Methods

Gasol, J. M., & Morán, X. A. G. (2015). Flow Cytometric Determination of Microbial Abundances and Its Use to Obtain Indices of Community Structure and Relative Activity. Hydrocarbon and Lipid Microbiology Protocols, 159–187. https://doi.org/10.1007/8623_2015_139
Methods

Graff, J. R., Nelson, N. B., Roca-Martí, M., Romanelli, E., Kramer, S. J., Erickson, Z., Cetinić, I., Buesseler, K. O., Passow, U., Zhang, X., Benitez-Nelson, C., Bisson, K., Close, H. G., Crockford, T., Fox, J., Halewood, S., Lam, P., Roesler, C., Sweet, J., … Siegel, D. A. (2023). Reconciliation of total particulate organic carbon and nitrogen measurements determined using contrasting methods in the North Pacific Ocean as part of the NASA EXPORTS field campaign. Elem Sci Anth, 11(1). https://doi.org/10.1525/elementa.2022.00112
Methods

Halewood, E., Opalk, K., Custals, L., Carey, M., Hansell, D. A., & Carlson, C. A. (2022). Determination of dissolved organic carbon and total dissolved nitrogen in seawater using High Temperature Combustion Analysis. Frontiers in Marine Science, 9. https://doi.org/10.3389/fmars.2022.1061646