Deepwater Horizon oil spill's dramatic effect on stingrays' sensory abilities

November 13, 2018, Florida Atlantic University
Marine fishes, like stingrays, rely on the effective functioning of their sensory systems to survive. Exposure to crude oil could detrimentally impact their fitness, lead to premature death, and cause additional cascading effects through lower trophic levels. Credit: Stephen M. Kajiura, Ph.D./Florida Atlantic University

It has been almost a decade since the Deepwater Horizon Oil spill. Described as the worst environmental disaster in the United States, nearly 5 million barrels of crude oil oozed into the Gulf of Mexico, severely degrading the marine ecosystem immediately surrounding the spill site and directly impacting coastal habitats along 1,773 kilometers of shoreline. About 10 million gallons remain in the sediment at the bottom of the Gulf and may continue to cause severe physiological damages to marine life, including impairment of sensory systems.

Marine fishes rely on the effective functioning of their sensory systems to survive. Despite the obvious importance of their olfactory (sense of smell) system, the impact of exposure on sensory function remains largely unexplored.

Researchers at Florida Atlantic University are the first to quantify the physiological effects of whole crude oil on the olfactory function of a marine vertebrate—the Atlantic stingray, Hypanus sabinus, an elasmobranch fish. Results of the study, published in Scientific Reports, confirm that exposure to crude oil, at concentrations mimicking those measured in coastal areas following the Deepwater Horizon oil spill, significantly impaired olfactory function in the Atlantic stingray after just 48 hours of exposure. These findings suggest that exposure to crude oil could detrimentally impact fitness, lead to premature death, and cause additional cascading effects through lower trophic levels.

"Elasmobranchs are renowned for their well-developed sensory systems, which are critical to alert them of the presence of predators, prey, mates, and unfavorable environmental conditions. Any impairment of these sensory systems could have a damaging effect on their survival and fitness," said Stephen M. Kajiura, Ph.D., co- author, a professor of biological sciences in FAU's Charles E. Schmidt College of Science and director of the Elasmobranch Research Laboratory at FAU.

The Atlantic stingray, Hypanus sabinus, an elasmobranch fish, is renowned for its well-developed sensory systems, which are critical to alert them of the presence of predators, prey, mates, and unfavorable environmental conditions. Any impairment of these sensory systems could have a damaging effect on their survival and fitness. Credit: Stephen M. Kajiura, Ph.D./Florida Atlantic University

The work was conducted by Eloise J. Cave, as part of her master's degree in Kajiura's lab. Cave, who is now a Ph.D. student at the Florida Institute of Technology, employed an electro-physiological assay to test olfactory responses from stingrays held under clean water and oil-treated water. She found the oil exposed animals exhibited a smaller response, with a slower onset and longer duration.

"Unlike other in which the receptor cells are not in immediate contact with the environment such as the eye, inner ear, lateral line, and electroreceptors, the chemo-sensory cells of the are directly exposed, through the mucus, to the seawater," said Kajiura. "As a result, environmental pollutants have the ability to directly damage the receptor cells and affect olfactory function."

Although this study focused on a shallow water, coastal species, deep-water elasmobranch species may be highly susceptible to crude oil exposure. The researchers caution that deep-sea benthic species like skates—a type of cartilaginous fish that develop for prolonged periods in egg cases on the seafloor—in particular, could be continuously exposed to high concentrations of crude oil in the sediment throughout sensitive developmental periods. Also, because the metabolic rate of marine organisms declines significantly with temperature, and hence depth, deep-sea elasmobranch species have a much slower metabolic rate than shallow water species and therefore might metabolize crude oil much more slowly. This prolonged exposure could manifest as different or more severe results.

The Atlantic stingray, Hypanus sabinus, an elasmobranch fish, are abundant in near-shore coastal waters of the western Atlantic from Chesapeake Bay to Brazil and are found throughout the coastline affected by the Deepwater Horizon oil spill. Credit: Stephen M. Kajiura, Ph.D./Florida Atlantic University
"Under field conditions, animals are likely to encounter variable exposure concentrations, which may be higher or lower than the concentration used in our study," said Kajiura. "This acute has the potential to induce other physiological responses, potentially compounding the adverse effects of the altered . Even if the oil does not cause immediate or direct death, sub-lethal effects could still reduce fitness or contribute to premature death."

Crude oil contains many complex organic and inorganic compounds including heavy metals such as aluminum, manganese, cobalt, copper, zinc, and mercury. Heavy metals can block sodium and calcium ion channels in the olfactory systems of teleosts—a diverse group of ray-finned fishes—resulting in reduced olfactory responses. In addition, water-soluble fractions of crude oil have caused hyperplasia, necrosis, and lesions on the . All of these physical insults may result in reduced olfactory sensitivity to chemical stimuli.

Explore further: Gene therapy restores sense of smell in mice

Related Stories

Gene therapy restores sense of smell in mice

July 30, 2018

Re-expressing a protein critical for the detection and perception of odors restores function of the olfactory system in a genetic mouse model of lost hair-like cellular structures known as cilia, according to research published ...

A new defender for your sense of smell

September 18, 2018

New research from the Monell Center increases understanding of a mysterious sensory cell located in the olfactory epithelium, the patch of nasal tissue that contains odor-detecting olfactory receptor cells. The findings suggest ...

It smells fishy: Copper prevents fish from avoiding danger

July 4, 2013

Fish fail to detect danger in copper-polluted water. A new study, to be presented at the meeting of the Society for Experimental Biology on the 5th of July, shows that fish cannot smell a danger odor signal emitted by other ...

Recommended for you

Archaeologists discover Incan tomb in Peru

February 16, 2019

Peruvian archaeologists discovered an Incan tomb in the north of the country where an elite member of the pre-Columbian empire was buried, one of the investigators announced Friday.

Where is the universe hiding its missing mass?

February 15, 2019

Astronomers have spent decades looking for something that sounds like it would be hard to miss: about a third of the "normal" matter in the Universe. New results from NASA's Chandra X-ray Observatory may have helped them ...

What rising seas mean for local economies

February 15, 2019

Impacts from climate change are not always easy to see. But for many local businesses in coastal communities across the United States, the evidence is right outside their doors—or in their parking lots.

The friendly extortioner takes it all

February 15, 2019

Cooperating with other people makes many things easier. However, competition is also a characteristic aspect of our society. In their struggle for contracts and positions, people have to be more successful than their competitors ...

0 comments

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.