Natural hydrocarbon seeps occur on the sea floor along continental margins, and account for up to 47% of the oil released into the oceans1. Hydrocarbon seeps are known to support local benthic productivity2, but little is known about their impact on photosynthetic organisms in the overlying water column. Here we present observations with high temporal and spatial resolution of chlorophyll concentrations in the northern Gulf of Mexico using in situ and shipboard flow-through fluorescence measurements from May to July 2012, as well as an analysis of ocean-colour satellite images from 1997 to 2007. All three methods reveal elevated chlorophyll concentrations in waters influenced by natural hydrocarbon seeps. Temperature and nutrient profiles above seep sites suggest that nutrient-rich water upwells from depth, which may facilitate phytoplankton growth and thus support the higher chlorophyll concentrations observed. Because upwelling occurs at natural seep locations around the world1,2,3, we conclude that offshore hydrocarbon seeps, and perhaps other types of deep ocean vents and seeps at depths exceeding 1,000 m, may influence biogeochemistry and productivity of the overlying water column.
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We thank the science parties and ship’s crew of the RV Endeavor for their assistance with multiple shipboard operations. We thank O. Garcia-Pineda for his assistance in providing the TCNNA-derived database of putative natural oil seeps. We thank K. Geddes for assistance with chlorophyll extractions used in ALFA calibrations. This work is supported by The Gulf of Mexico Research Initiative’s (GOMRI) ECOGIG consortium, with additional support from NSF grant NSF-OCE-0928495 to J.P.M. and NASA grant NNX10AT99G to A.S. This is LDEO contribution number 7951, and ECOGIG contribution number 365. Data are available from the Gulf of Mexico Research Initiative Information and Data Cooperative (http://data.gulfresearchinitiative.org: R1.x132.134:0003, R1.x132.134:0005, R1.x132.139:0025, R1.x132.137:0045).
The authors declare no competing financial interests.
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D’souza, N., Subramaniam, A., Juhl, A. et al. Elevated surface chlorophyll associated with natural oil seeps in the Gulf of Mexico. Nature Geosci 9, 215–218 (2016). https://doi.org/10.1038/ngeo2631
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