Natural oil slicks fuel surface water microbial activities in the northern Gulf of Mexico.
We conducted a series of roller tank incubations with surface seawater from the Green Canyon oil reservoir, northern Gulf of Mexico, amended with either a natural oil slick (GCS-oil) or pristine oil. The goal was to test whether bacterial activities of natural surface water communities facilitate the formation of oil-rich marine snow (oil snow). Although oil snow did not form during any of our experiments, we found specific bacterial metabolic responses to the addition of GCS-oil that profoundly affected carbon cycling within our 4-days incubations. Peptidase and β-glucosidase activities indicative of bacterial enzymatic hydrolysis of peptides and carbohydrates, respectively, were suppressed upon the addition of GCS-oil relative to the non-oil treatment, suggesting that ascending oil and gas initially inhibits bacterial metabolism in surface water. Biodegradation of physically dispersed GCS-oil components, indicated by the degradation of lower molecular weight n-alkanes as well as the rapid transformation of particulate oil-carbon (C: N >40) into the DOC pool, led to the production of carbohydrate- and peptide-rich degradation byproducts and bacterial metabolites such as transparent exopolymer particles (TEP). TEP formation was highest at day 4 in the presence of GCS-oil; in contrast, TEP levels in the non-oil treatment already peaked at day 2. Cell-specific enzymatic activities closely followed TEP concentrations in the presence and absence of GCS-oil. These results demonstrate that the formation of oil slicks and activities of oil-degrading bacteria result in a temporal offset of microbial cycling of organic matter, affecting food web interactions and carbon cycling in surface waters over cold seeps.
Department of Marine Sciences, University of North Carolina Chapel Hill Chapel Hill, NC, USA.
Kai
K
Ziervogel
Lamont-Doherty Earth Observatory, Biology and Paleo Environment, Columbia University Palisades, NY, USA.
Nigel
N
D'Souza
Marine Science Institute, University of California Santa Barbara Santa Barbara, CA, USA.
Julia
J
Sweet
Lamont-Doherty Earth Observatory, Geochemistry, Columbia University Palisades, NY, USA.
Beizhan
B
Yan
Marine Science Institute, University of California Santa Barbara Santa Barbara, CA, USA.
Uta
U
Passow
GC600; Gulf of Mexico; TEP; carbon cycle; enzyme activities; oil slick; oil snow