Pelagic marine fish eggs and larvae were highly susceptible to oil spill-related pollution. Because recruitment success is largely determined by survivorship during the early life history stages, increased mortality related to the Deep Water Horizon spill could impact future year classes of marine fishes, including recreationally and commercially important species (e.g., red snapper, gag, Gulf menhaden), as well as ecologically important forage fishes (bay anchovy, striped mullet, Atlantic bumper).
Using a combination of morphometric and molecular identification techniques, we will address the following hypotheses related to ichthyoplankton assemblages:
H01: There is no difference in taxonomic richness between pre-spill and post-spill assemblages of fish eggs and larvae.
H02: There is no difference in taxonomic diversity between pre-spill and post-spill assemblages of fish eggs and larvae.
H03: There is no difference in fish egg and larval fish abundances between pre-spill and post-spill assemblages.
H04: There is no difference in fish egg and larval fish vertical distribution between pre-spill and post-spill assemblages.
Plan of Work:
Depth-discrete ichthyoplankton samples have been collected off the coast of Alabama since October 2004 (station depth = 20 m), providing a relatively long-term time series with unprecedented vertical resolution (3 m depth bins). These data will provide valuable, pre-spill information on fish egg and larval abundances, taxonomic richness, diversity and vertical distributions for comparison with samples collected during and after the spill. Due to the time limitations associated with the work plan (one year), only samples collected during one month coincident with the occurrence of oil in the study region (e.g., June or July) will be analyzed. Fish eggs and larvae from pre-spill June/July samples (2005-2009) and post-spill June/July samples (2010) will be counted and identified. Larvae will be identified to the lowest possible taxonomic level using morphometric characters. Fish eggs and any morphologically problematic larvae will be identified to species molecularly using DNA barcoding techniques (DNA sequencing of partial cytochrome c oxidase I [COI]). Plankton samples will be aliquoted as necessary to expedite ichthyoplankton processing. Statistical comparisons will be made to determine if there were any changes in taxon-specific abundances, vertical distributions and assemblage metrics (i.e., richness, diversity).