North America

New Study Pinpoints Effects of Oil on Tuna — and Humans

During the 2010 Deepwater Horizon oil spill that poured 4.9 billion into the Gulf of Mexico — TV images showed a thick, glowing sheen of oil clinging to the water’s surface, along with heartbreaking images of oiled pelicans and dolphins. Below the surface, another unseen, less obvious calamity was taking place.

The oil spill coincided with the peak of the spawning season for Atlantic blue fin tuna in the gulf, an Olympian of the sea known for swimming great distances across vast oceans. Now years later, the effects of the tuna’s exposure to the oil are becoming clear.

Scientists at Stanford’s Hopkins Marine Station in Monterey, where blue fin and yellow tuna are a focus of study, a newly published paper reveals that exposure to a component in the spilled oil caused heart problems in the tuna.

“What we found was one in particular - “phenanthrene,” actually blocked the excitable part of every heart beat,” Stanford scientist Barbara Block said of the petroleum component, “so it caused an irregular heartbeat that’s called arrhythmia.”

Working alongside NOAA, the scientists added crude oil to tuna heart cells which immediately caused a noticeable impact — a blockage that interrupted the rhythm of the heartbeat.

“When you put crude oil on heart cells it interrupts the beat to beat contraction,” Block said, “the physiology of the heart cell, such that it causes irregularities of heart beat.”

Inside the Hopkins campus, the Tuna Research center represents one of the few tuna research centers in North America. Inside a smattering of buildings facing the Monterey Bay, blue fin and yellow tuna up to 200 pounds swim in circular pens.

“Blue fin tuna are remarkable fish,” Block said sitting in the center’s office where images of tuna covered the walls. “They grow up to 1500 pounds — they’re capable of transoceanic migrations.”

Stanford and NOAA began their study of the oil spill’s impact on tuna at the request of the federal government following the devastating oil spill. Block said the group first dive into the study discovered the oil’s impact on embryonic tuna. The study went-on to pinpoint the main culprit — phenanthrene — which is also found in cigarette smoke, storm runoff and air pollution.

“Levels in the range of 1 to 15 parts per billion was enough to affect the larval development,” researcher Luke Gardner said, “specifically how the heart forms.”

Because the tuna center has long developed long-range tagging of tuna, the scientists were able to retroactively determine that the tuna were in the gulf at the time of the oil spill.

“So then we were able to go back in time and look at when the oil spill actually occurred,” said Stanford scientist Aaron Carlisle, “and look at how much of the blue fin spawning habitat was oiled.”

Block said what may be the study’s most compelling thought is that the workhorse tuna hearts function like human hearts — which could reveal impacts of pollution on human cardiovascular systems as well. Since the contaminant is readily found in air pollution, it could have a widespread impact on human health globally.

“We hypothesize the phenanthrene found in crude oil would also bind our hearts too,” Block said, “in such a way that we get an arrhythmia and we could also get sudden death.”

Block said next phases of the study could reveal the extent the exposure to pollution on humans — potentially revealing that components of pollution could be the smoking gun behind some heart attacks and other cardiovascular issues.

“What we’ve been studying in the tuna,” Block said, “actually relates to us.”

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