On April 22, 2010, the drill platform Deepwater Horizon sank in nearly 1,200 m of water in the northern Gulf of Mexico. Since this date various estimates of oil and added chemical dispersants have been released from the site with dispersion both at the surface and at depth. The transport of this oil and dispersants has been influenced by wind-driven currents over the shelf and by the Loop Current and its derivatives offshore. To date the exact amount and paths of movement of the Horizon spill remain speculative. Since 2003, with NOAA-CSCOR funding, this group of investigators has conducted 5 summer cruises in the northern Gulf of Mexico that used high-resolution sampling to define the spatially explicit relationships between physical structure to pelagic zooplankton and fish distributions. Thus this group has one of the most comprehensive, synoptic data sets on temperature, salinity, oxygen, phytoplankton, zooplankton and fish in the northern Gulf of Mexico for conditions prior to the oil leak.
The current RAPID award will allow this group to repeat their high-resolution mapping of hydrography, oxygen, plankton and fish in the northern Gulf of Mexico. The domain of interest will include the previous survey region in the hypoxic zone west of the Mississippi Delta but also the area east of the Mississippi where more oil transport from the spill has been suggested. The cruise will take place in the late summer period because the investigators have 5 years of ?baseline? data during this season to compare the results. The measures of species diversity and abundance, biomass size spectrum, fish diets, fish growth rate potential and ecosystem models will all be extremely useful to assess the possible effects of the oil spill on the living resources of the northern Gulf of Mexico. In addition to the rapid mapping cruise on the inner to mid-shelf, this group also will send scientists on the ORV Oceanus to conduct high resolution vertical zooplankton measurements (LOPC and TAPS) and MOCNESS zooplankton tows at deeper stations and broader mapping surveys to extend our spatial coverage of the affected area. They will coordinate our zooplankton and fish measurements with other investigators assessing the biogeochemical and biological impacts of the BP oil spill. Data from previous NOAA will be deposited in the BCODMO data management facility as well as current measurements and model products.
Broader Impacts. Given the economic importance of the Gulf of Mexico commercial fisheries (about 20% of the U.S. total landings representing about $991 million) and recreational fishing (generating ~30% of the nation?s saltwater fishing expenditures and supporting nearly 25% of the nation?s recreational saltwater jobs), it is imperative that knowledge of the effects of the BP oil spill on the pelagic ecosystem be assessed. The Horn Point Laboratory and Oregon State University are part of the National Science Foundation ? Center for Ocean Sciences Education Excellence (NSF-COSEE) and Experience for Undergraduates (REU) programs. Where possible in this NSF RAPID response grant, we will involve REU undergraduate students and teachers in our proposed research program.
Our research was aimed at examining the response of the zooplankton community to the Deepwater Horizon oil spill. During mid-August to mid-September 2010, we participated in a collaborative research cruise aboard the R/V Oceanus in the northern Gulf of Mexico. During the cruise, we deployed a laser optical plankton counter (LOPC) to determine zooplankton vertical distribution and abundance in the water column and collected mesozooplankton for extraction of oil derived contaminant compounds that may have been incorporated through exposure. We sampled the area immediately surrounding the Deepwater Horizon spill location and a location to the south of the well. Our first major outcome of the research was that we found no difference between zooplankton biomass or abundance near the wellhead or offshore. Zooplankton estimates using the LOPC were comparable to those found by other researchers in the northern Gulf of Mexico. These results must be viewed with some caution as they are LOPC estimates and must be compared to net estimates of zooplankton. Our second major outcome is that we discovered oil derived compounds (polycyclic aromatic hydrocarbons (PAH)) were present in zooplankton collected from all locations we samples. We used a gas chromatograph to characterize a suite of PAHs from both zooplankton and oil collected from the Gulf of Mexico and the Deepwater Horizon riser pipe. The PAH signatures of both oil samples matched zooplankton PAH signals suggesting that the PAH compounds found within zooplankton were derived from the Deepwater Horizon spill. It was not clear from our research whether or not the PAHs found in zooplankton were readily transferred up the food web; however, our results do confirm that zooplankton were taking up these compounds for a significant time period during and after the spill.
