Award: OCE-1043248

The recent unprecedented events in the Gulf of Mexico, the MC252 oil spill in 2010 and record flooding of the Mississippi River in 2011, are likely to have far reaching impacts on many aspects of the northern Gulf of Mexico pelagic ecosystem. We collected high resolution data on the physical conditions, fish resources, and plankton populations during a cruise in September 2010 on the Louisiana continental shelf. The purpose of this was to compare the results from 2010 with earlier work we conducted in that region to determine if there were measurable impacts of the spill. In addition, we provided personnel to participate in zooplankton sampling offshore, near the site of the spill to assess the direct impact of the spill on those animals. We found that near the site of the spill, oil residues were found in zooplankton, with signatures of fresh material found in animals collected in deep water, and weathered material found in animals collected in surface water. This work was part of collaboration between a number of researchers on our team and was published in the Journal of Geophysical Letters (Mitra et al. 2012). When we compared the results from our cruise on the continental shelf to observations made during earlier work in the same region, we were not able to discern any major impacts on plankton and fish. This region includes the "Dead Zone", an area of depleted oxygen that occurs every summer on the Louisiana shelf. Data from net tows, pump and niskin bottle samples, optical plankton counters, fish trawls, and hydrographic instruments were used to compare zooplankton community structure and physical characteristics between years and across this region. We found that for the earlier data (2003-2008) the most important conditions to predict the zooplankton community were temperature and salinity in the water, and when we did analysis using the 2010 data, that same pattern was observed. Data from 10 acoustic surveys showed that pelagic fish abundance was higher near shore and decreased offshore during 2010 sampling. High densities of fish were not found in areas of low DO. These data, along with hydrographic data and acoustic surveys from 2003-2008, are now accessible through a Matlab-compatible data management system, which will be made publically available. In addition, we sampled over 50 different species of fish through 18 midwater trawl surveys at 13 stations on 6 transect lines. The most commonly observed species in 2010 was Atlantic croaker (N = 243, mean length = 140mm (range = 90-190cm)), followed by cutlassfish, longspine porgy, striped anchovy, and Atlantic bumper. Acoustic surveys and fish species data will be used along with temperature and DO data in growth rate potential models to determine areas of the northern Gulf of Mexico that provide suitable habitat for fish growth. Data from this project was submitted to the The Biological and Chemical Oceanography Data Management Office (BCO-DMO) and can be accessed at the following URL: http://osprey.bco-dmo.org/project.cfm?id=137&flag=view Last Modified: 11/13/2012 Submitted by: James J Pierson