Current Projects: Deepwater Horizon Impacts on Ichthyoplankton

Title: Resolving Deepwater Horizon Impacts on Highly Variable Ichthyoplankton and Zooplankton Dynamics in the Northern Gulf of Mexico

Funding Agency/Contractor: Gulf of Mexico Research Initiative

Duration:  January 2013 - December 2015

Background: The impacts of the Deepwater Horizon (DWH) oil spill on marine fish populations of the northern Gulf of Mexico are largely unknown. Of particular concern in the wake of the DWH event was the fate of pelagic fish eggs and larvae that were present in the water column at the time, as these are the most vulnerable life stages.

Variability in the recruitment of marine fishes to adult populations is largely related to the variability encountered in vital rates (e.g., growth) during the larval stages, therefore DWH-related impacts on ichthyoplankton may have profound effects on future recruitment and fishery yields. In order to detangle DWH impacts from the highly variable "background noise" in the marine environment, a time series that covers a wide range of environmental conditions, as well as 'baseline', impact', and 'recovery' periods is critical. Preliminary analysis of plankton samples collected during a long-term (2004-2011) survey has identified changes in both zooplankton and ichthyoplankton assemblage structures off the coast of Alabama during the DWH oil spill.

John Ransom and Dr. Jesse Filbrun tie off the MININESS to depart after a long day of sampling.
John Ransom and Dr. Jesse Filbrun tie off the MININESS to depart after a long day of sampling.
The overall goal of this study is to examine how the documented shifts in zooplankton community structure during the DWH event affected larval fish feeding, growth and condition (critical factors related to survivorship and recruitment success). Relative to fisheries oceanography and recruitment theory, the overarching question is, "Did the DWH event create a 'mismatch' scenario in the planktonic food web?” At the core of this study is access to data collected as part of a unique plankton survey that is the only source of pre-DWH zooplankton and ichthyoplankton data for the northern Gulf of Mexico region collected at high temporal (monthly sampling throughout; twice monthly during the DWH event) and spatial resolutions (three cross-shelf stations, each with vertically-discrete sampling).

Objectives: The objectives of this study are to examine larval fish feeding, growth and condition (using established methodologies) and compare these parameters among 'baseline', 'impact', and 'recovery' periods. The specific hypotheses are as follows:

H01: Diets (as determined by gut content analysis) will not differ among larval fishes collected during the May-August time periods before the spill, during the spill, and after the spill.

H02: Growth (as determined by size vs. age relationships) will not differ among larval fishes collected during the May-August time periods before the spill, during the spill, and after the spill.

H03: Condition (as determined by size vs. dry weight relationships) will not differ among larval fishes collected during the May-August time periods before the spill, during the spill, and after the spill.

Presentations from the 2014 Gulf of Mexico Oil Spill and Ecosystem Science Conference

Cruise Reports