Studies Assess Gulf of Mexico Fish Tissue Following Deepwater Horizon

(Top) C-IMAGE researchers collect golden tilefish bile and tissue samples to measure oil exposure. Photo by Steve Murawski. (bottom, left) Tissue, bile, and blood samples collected from Gulf of Mexico fish are stored in a cooler for later analysis. Provided by C-IMAGE. (bottom, right) C-IMAGE researchers process and collect blood, bile, liver, and tissue samples from fish captured during the 2015 Mud & Blood research cruise. Photo by Elizabeth Herdter.

(Top) C-IMAGE researchers collect golden tilefish bile and tissue samples to measure oil exposure. Photo by Steve Murawski. (bottom, left) Tissue, bile, and blood samples collected from Gulf of Mexico fish are stored in a cooler for later analysis. Provided by C-IMAGE. (bottom, right) C-IMAGE researchers process and collect blood, bile, liver, and tissue samples from fish captured during the 2015 Mud & Blood research cruise. Photo by Elizabeth Herdter.

The 2010 Deepwater Horizon incident released approximately 4.9 million gallons of oil into the northern Gulf of Mexico. A 2010 study measured oil concentrations considered toxic to marine organisms that extended at least 13 km from the spill site, and there was evidence later that West Florida Shelf waters were affected. Researchers estimate that up to 14% of Deepwater Horizon oil sank to the seafloor via a marine oil snow sedimentation and flocculent accumulation (MOSSFA) event, exposing benthic and pelagic animals and environments to toxic polycyclic aromatic hydrocarbons (PAHs) and chemical dispersants.

A lack of baseline data for many Gulf of Mexico fish hindered researchers’ abilities to conduct comparative analyses of fish health before and after the spill. Instead, they analyzed oil concentrations in fish tissue over time following the oil spill. An international research team conducted comprehensive Gulf-wide longline fish surveys from 2011– 2018, collecting 15,000 fish that represented 166 species. They evaluated biliary PAH concentrations in 2,503  fishes (91 species) since PAH metabolites in fish bile can act as a sensitive biomarker of recent or ongoing PAH exposure.

Here are four recent studies that highlight their findings, which help improve our understanding about the spill’s possible sublethal effects on fish and establish a new baseline of data that researchers can use for future studies of Gulf of Mexico fishes.

Mean biliary PAH contamination for all fishes combined declined 24% for the three years following Deepwater Horizon. However, mean biliary PAHs increased 173% for all fishes caught in 2017 combined, suggesting ongoing oil input and/or the resuspension of oil-contaminated sediments following natural disturbances (such as storms). The species with the highest total biliary PAH concentrations were yellowfin tuna, golden tilefish, and red drum that were collected from pelagic, benthic, and inshore habitats, respectively. Elevated PAH concentrations in this array of fish suggest that the oil spill affected widespread areas throughout the Gulf. These findings were published in Scientific Reports: A first comprehensive baseline of hydrocarbon pollution in Gulf of Mexico fishes. Data are publicly available through the Gulf of Mexico Research Initiative Information and Data Cooperative (GRIIDC) at doi: 10.7266/N7X34W1J.

Researchers examined 268 golden tilefish captured during the Gulf-wide surveys and assessed biliary PAH metabolites, accumulated liver PAH concentrations, and Fulton’s condition factor (uses fish weight and length to determine overall condition). They found a 178% increase in biliary PAH metabolite equivalents over six years that correlated with an average 22% decline in general health condition and a 53% decline in liver lipids, though no PAH accumulation was observed in liver tissue during the study period. These findings suggest that, while golden tilefish appear to metabolize and eliminate PAHs efficiently, the energetic cost of chronic PAH metabolization may decrease fish condition and liver lipid reserves. These findings were published in Environmental Toxicology and Chemistry: Associations between chronic exposure to polycyclic aromatic hydrocarbons and health indices in Gulf of Mexico Tilefish (Lopholatilus chamaeleonticeps) post-Deepwater Horizon. Data are publicly available through GRIIDC at doi: 10.7266/n7-g27a-x012, 10.7266/N7X34W1J.

Researchers also analyzed biliary PAH metabolites and liver PAH concentrations for 124 Gulf hake and 40 southern hake specimens collected during the Gulf-wide surveys. They found an 18% decrease in biliary PAH metabolites and a 119% increase in total liver PAH concentrations during the study period, suggesting decreasing acute PAH exposures and ongoing chronic exposures, respectively. They observed that biliary PAH concentrations did not significantly differ between hake species, and spatial analyses did not suggest that biliary metabolites and liver PAH concentrations had a direct correlation with distance from the Deepwater Horizon site. These findings were published in Environmental Toxicology and Chemistry: Hepatobiliary analyses suggest chronic PAH exposure in Hakes (Urophycis spp.) following the Deepwater Horizon oil spill. Data are publicly available through GRIIDC at doi: 10.7266/N7X34W1J, 10.7266/n7-tv8b-7h23.

The team analyzed PAH concentrations in the liver and bile of 584 groupers, representing ten species. All biometrics and health indices declined up to 65% during the first three years following the oil spill and then improved afterwards. However, liver lipids were still in decline in 2017 samples, perhaps resulting from resuspension events, inputs from natural oil seeps, riverine runoff, other spills, and leaking infrastructure. There were spatial, temporal, and species differences in PAH levels and profiles. Grouper from the West Florida Shelf, Cuban coast, and the Yucatan Shelf had a greater proportion of PAHs in their livers than the other regions likely due to non-oil industry related sources, such as marine vessel traffic. PAH liver levels in Yellowedge Grouper from the north central region showed consistent increase over time (+827% increase between 2011 and 2017), while Red Grouper from the West Florida Shelf area showed a decline (−78%), suggesting chronic oil exposure in the north central region. These findings were published in Science of the Total Environment: Chronic PAH exposures and associated declines in fish health indices observed for ten grouper species in the Gulf of Mexico. Data are publicly available through GRIIDC at doi: 10.7266/n7-0g6x-wc84, 10.7266/N7X34W1J, and 10.7266/0C3NH760

For more information, here are additional studies that analyzed Gulf of Mexico fish following Deepwater Horizon include:

By Stephanie Ellis and Nilde Maggie Dannreuther. Contact maggied@ngi.msstate.edu with questions or comments.

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This research was made possible in part by a grant from the Gulf of Mexico Research Initiative (GoMRI) to the Center for the Integrated Modeling and Analysis of Gulf Ecosystems (C-IMAGE), C-IMAGE II, and C-IMAGE III.

The Gulf of Mexico Research Initiative (GoMRI) is a 10-year independent research program established to study the effect, and the potential associated impact, of hydrocarbon releases on the environment and public health, as well as to develop improved spill mitigation, oil detection, characterization and remediation technologies. An independent and academic 20-member Research Board makes the funding and research direction decisions to ensure the intellectual quality, effectiveness and academic independence of the GoMRI research. All research data, findings and publications will be made publicly available. The program was established through a $500 million financial commitment from BP. For more information, visit http://gulfresearchinitiative.org/.

© Copyright 2010-2020 Gulf of Mexico Research Initiative (GoMRI) – All Rights Reserved. Redistribution is encouraged with acknowledgement to the Gulf of Mexico Research Initiative (GoMRI). Please credit images and/or videos as done in each article. Questions? Contact web-content editor Nilde “Maggie” Dannreuther, Northern Gulf Institute, Mississippi State University (maggied@ngi.msstate.edu).