Grantee Research Project Results

Introduction

This project had research and community outreach components with a focus on commercial shellfish affected by the Deepwater Horizon spill in the Gulf of Mexico. The following two research projects were completed: (1) The fate of water-in-oil emulsions in estuaries and the effects of these emulsions on grass shrimp and blue crabs; (2) Effects of dispersed oil droplets on molting processes (molting, ecdysteroids, EcR/RXR complexes) on grass shrimp embryogenesis. The co-operative research was carried out by investigators at the Skidaway Institute of Oceanography – University of Georgia (R. Lee), Gulf Coast Research Laboratory at the University of Southern Mississippi (H. Perry), and the Institute of Marine and Environmental Technology at University of Maryland Center for Environmental Sciences (J.S. Chung). The community outreach phase of the project was carried out at the Marine Education Center of the Gulf Coast Research Laboratory at the University of Southern Mississippi (C. Snyder and K. Kastler) and involved members of Gulf of Mexico coastal communities. This outreach included several events and training sessions that linked ongoing oil spill research to concerns of the community about the effects of the oil spill on Gulf of Mexico shellfish.

 

Fate and Effects of Emulsions Produced after Oil Spills

A.  Stable water-in-oil emulsions, often formed after oil spills, contribute to the difficulties of cleanup due to their persistence and high viscosity (Fig. 1). Our objectives were to determine the fate and effects of these emulsions on grass shrimp (Palaemonetes pugio) and blue crabs (Callinectes sapidus) after the entrance of emulsions into estuaries. Reproductive parameters (ovary development, embryo production) of adult grass shrimp were assessed after exposure of juveniles to mesocosm sediments with emulsified oil, sediments with non-emulsifed oil and reference sediments. There was a significant reduction in grass shrimp embryo production after exposure to sediments with emulsified oil compared to shrimp exposed to reference or non-emulsifed oiled sediments (Table 1). Grass shrimp embryos exposed to pore water from emulsified oiled sediments resulted in significantly more DNA strand breaks (comet assay) and reduced embryo hatching rates compared to embryos exposed to reference or non-emulsifed oiled sediments (Table 2).

 

B.  In addition to work with oiled sediments, a histological study was conducted on juvenile blue crabs from the Gulf of Mexico (provided by H. Perry) fed food containing emulsified oil. The most notable effect was distended hemocytes with large amounts of glycoproteins in the hepatopancreas (Fig. 2). It is speculated that crabs with these distended hemocytes are less able to deal with invading microbes, since crab hemocytes are an important part of crab’s immune system.

 

C.  Changes in polycyclic aromatic hydrocarbons (PAHs) concentrations were followed in cores taken from mesocosms containing emulsified oiled sediments, non-emulsifed oiled sediments and reference sediments. PAH concentrations in emulsified oiled sediments decreased from 284 to 7 µg/g sediment in 56 days, while in the mesocosm with non-emulsifed oil the PAHs decreased from 271 to 0.2 µg/g sediment over the same time period (Fig. 3). Oiled sediments showed a typical petrogenic PAH profile with high concentrations of lower molecular weight alkylated PAHs, e.g. methylnaphthalenes and phenanthrenes. Control sediment had a low concentration of total PAHs (0.1 µg/g sediment) composed of high molecular weight pyrogenic type PAHs (4-5 ringed nonalkylated PAHs).

 

View all 8 publications for this project

Relevant Websites:

Deepwater Horizon Oil Spill: Five Years Later, Vigorous Research Continues Exit
Teens hit Maryland beach to study crabs Exit
Crabs’ birds and bees: Effects of crab sex life on Maryland industry Exit

Progress and Final Reports:

Original Abstract

2012 Progress Report

2013