(NaturalNews) Swimming majestically in the open seas, with eyes wide on both sides of its face, the bluefin tuna gazes into... a curtain of crude oil.
When the 2010 BP oil spill contaminated the waters of the Gulf of Mexico, beautiful wild fish like the bluefin tuna were forced to face new challenges for survival. Now, researchers from the National Oceanic and Atmospheric Administration (NOAA) and Stanford University are discovering that oil pollution can elicit early heart attacks in this species of fish.
Bluefin tuna cannot escape or hide from heart-debilitating oil pollution
These fish, which can weigh up to 550 pounds and measure 6.5 feet long, are not immune from the damaging effects of oil pollution. As one of the world's largest fish species in the world, the bluefin tuna is also built for both speed and endurance. With the ability to retract their dorsal and pectoral fins, bluefin tuna can reduce drag and swim up to 43 miles per hour. Their gorgeously colored metallic blue top and silver-white bottom help keep the fish camouflaged in the open seas, from top to bottom. But what the fish can not hide from or swim faster than is a massive oil spill. In this new study, oil pollution is found to block the bluefin tuna's cardiac tissues from receiving needed calcium and potassium, causing early heart attacks.
The early die-off of these bluefin tuna in the Gulf of Mexico could mean shortages of food for those who depend on the species for survival. The oil pollution could possibly be passed upward through the food chain. Since bluefin tuna swim from the tropical Gulf of Mexico to the cold climate near Europe several times a year, the early death of these fish may spell consequences for other parts of the world. Aggressive commercial fishing is also pushing these fish closer to extinction, so the early die-offs from the oil are not helping.
Since fish don't have 3D vision, they rely on extremely acute and interrelated senses of smell and taste, which act as feelers for their environment. These senses will have to grow keener if the bluefin tuna seeks to avoid oil-contaminated water in the future.
Study shows how bluefin tuna experience heart attacks due to oil pollution
At the Tuna Research Conservation Center in California and Monterey Bay Aquarium, the researchers collected in vitro cells from the cardiac tissues of yellowfin and bluefin tuna.
In the cardiac cells, they immediately discovered traces of oil pollution or polycyclic aromatic hydrocarbons (PAHs). These PAHs block the flow of calcium and potassium ions coming and going from the fish's cell membranes. Potassium and calcium, both essential for maintenance of regular heart rate in the fish, were being blocked by the oil contamination that the fish were accumulating in their heart cells. Very minute concentrations of oil were found to disrupt this cellular nutrition process, which causes an abnormal heart beat in the fish.
Concerned for the survival of fish in general, the researchers began tagging other fish in the Gulf of Mexico to study their cardiac tissues. They found small amounts of PAHs in many species of fish, including blue marlin, swordfish and dolphinfish.
The pollution spreads, could impact humans
The Gulf of Mexico, which is one of the most diverse ocean ecosystems in the planet, has become a cesspool for aquatic life, spreading toxic PAHs into the cells of fish.
"This raises the possibility that exposure to environmental PAHs in many animals - including humans - could lead to cardiac arrhythmias and bradycardia, or slowing of the heart," professor Barbara Block, a professor of marine sciences at Stanford's Hopkins Marine Station, wrote in the study.
The authors of the study conclude, "Here, we show that crude oil samples collected from the DWH spill prolonged the action potential of isolated cardiomyocytes from juvenile bluefin and yellowfin tunas, through the blocking of the delayed rectifier potassium current (IKr). Crude oil exposure also decreased calcium current (ICa) and calcium cycling, which disrupted excitation-contraction coupling in cardiomyocytes. Our findings demonstrate a cardiotoxic mechanism by which crude oil affects the regulation of cellular excitability, with implications for life-threatening arrhythmias in vertebrates."