Nearly 100 percent of red snapper sampled in the Gulf of Mexico over a six-year period by marine scientists at the University of South Florida (USF) showed evidence of liver damage, according to a study published in Aquatic Toxicology.
The study is the first to link the concentration of crude oil found in the working horses of the digestive system – liver, gallbladder, and bile – with microscopic indicators of diseases, such as inflammation, degenerative lesions and the presence of parasites. The team sampled about 570 fish from 72 locations in the Gulf between 2011 and 2017 in the aftermath of the 2010 historic Deepwater Horizon oil spill.
“The results add to the list of other species we analyzed, indicating early warning signs of an endangered ecosystem,” said Irene Ballester, PhD, first author of the study and a researcher at the USF School of Marine Sciences.
Pollster and the team of researchers studying oil pollution in Gulf of Mexico fish previously reported high levels of oil exposure in yellowfin tuna, goldfish and red drum as well.
Not only is the Gulf of Mexico exposed to hundreds of annual oil spills with long-lasting impacts like the historic one in Deep Water Horizon in 2010, but it is also routinely subjected to intense shipping traffic and collects pollutants from as far away from coasts and rivers as Mighty. Mississippi and Rio Grande.
In this study, Pollester and his team specifically looked at the most toxic components of the crude oil called polycyclic aromatic compounds, or PAHs. Sources of polycyclic aromatic hydrocarbons include old oil and gas platforms, fuel from boats and airplanes, and natural oil spills, which are cracks on the sea floor that could add millions of barrels of oil to the Gulf each year.
The presence of polycyclic aromatic hydrocarbons in the bile, which the liver produces to aid in digestion, indicates a relatively recent exposure to the oil (days to weeks). The team found that the concentration of PAHs in the yellow decreased and remained relatively stable after 2011, but noticed a sharp increase in 2017.
In general, the PAH bile “hotspots” were on the West Florida escarpment (WFS) and in the vicinity of the Deepwater Horizon spill, off the mouth of the Mississippi River. This is the site of the 2004 Taylor oil rig collapse off Louisiana, the longest oil spill in history, which is still leaking oil today. Pollster said the western Tampa hotspot in WFS could be due to shipping traffic or drainage of groundwater from the submarines.
PAHs in the liver indicate chronic (months to years) exposure to oil in fish. The team found “hot spots” for PAH liver in the northwestern Gulf of Mexico, where there are many inactive oil and gas platforms.
Pollster said that while concentrations of PAHs in the liver remained relatively stable throughout the study period, indicating that red snapper actually managed exposure to the oil, there was a turning point. Red snapper can live up to 40 years, but fish deal with oily toxins, similar to how humans deal with exposure to greasy burgers and alcohol.
Repeated exposure to the oil in fish can lead to cancer and eventual death, but it may also have non-fatal effects. Almost all (99 percent) of the red snapper samples had an average of five physical signs of liver damage. The observed changes can result from natural causes but are also well-documented secondary responses to stress that can indicate disease progression.
“We don’t know when we’re going to turn the scale,” Ballester said. Pollster said there was literally a red snapper in the group containing PAHs, but no physical signs of damage when viewed under a microscope.
It is a good thing that humans eat only the muscles of the fish, not the liver. Red snapper is still safe to eat, but Pollester stressed the need for constant monitoring. Only then can scientists keep their fingers on the pulse of fish health and know what the effects of additional oil spills might be – especially in species like snapper that are so important to the Gulf economy, she said.
“This is a unique study.” Said Steve Murawski, Ph.D., senior author of the study. Murawski, St. Petersburg Chair of Partnership in Downtown Peter R. Bitzer, at the University of St. Petersburg School of Marine Sciences, led a 10-year research effort in response to the leak. Oil in Deepwater Horizon (C-IMAGE (usf.edu)).
“There is a story that we can extract from the data,” said Morawski. “The marked decrease in oil exposure in red snapper in the few years following the Deepwater Horizon accident indicates that the high levels measured in previous years were a direct effect of the spill. Its legacy continues, and we would be wise to continue the critical research the paradox made possible by Long-term monitoring after the disaster. ”
The study was supported by the Gulf of Mexico Research Initiative and the Center for Integrated Ecosystem Modeling and Analysis (C-IMAGE I, II and II).