HCNSO Student Theses and Dissertations

Defense Date


Document Type


Degree Name

M.S. Marine Biology

First Advisor

Dr. Tamara Frank

Second Advisor

Dr. Tracey T. Sutton

Third Advisor

Dr. Christopher Blanar

Fourth Advisor

Dr. Bernhard Riegl


This thesis presents the results of the first multi-year study on the euphausiid assemblage in the vicinity of the Deepwater Horizon oil spill (DWHOS), covering depths down to 1000 m. There are no data on the euphausiid assemblage from this region prior to the oil spill; therefore, the data in this study were analyzed with respect to year (samples collected in 2011 vs. those collected between 2015 – 2016), and season (May vs. August) to determine if any trends were present. These results presented here show a statistically significant decrease in both abundance and biomass between 2011 and 2015 – 2016, indicating that the assemblage has been declining since 2011, along with a continued decline from May 2016 to May 2017. Seasonal effects were also present, as abundance and biomass were statistically higher in May than in August in both 2011 and 2016. In addition, the percentage of gravid females of the grouped species, Nematoscelis atlantica/microps, was also higher in May for both years, but only statistically significant in 2016. This seasonal variability may possibly be linked to food availability as a result of seasonal phytoplankton blooms. The information presented here will act as a reference point for future studies in the Gulf of Mexico (GOM), to aid in understanding how the euphausiid assemblage responds to anthropogenic events.