Oil spills can stop tuna hearts, say scientists

Crude oil interferes with the transfer of potassium in the heart cells of bluefin tuna, preventing their hearts from beating properly, reports a new study that has implications across the animal kingdom.

|
Gilbert Van Ryckevorsel/TAG A Giant
An Atlantic bluefin tuna gapes at a smaller fish

When the Deepwater Horizon oil rig explosion sent plumes of crude oil billowing through the Gulf of Mexico, the Atlantic bluefin tuna who breed there were at the height of their spawning season, releasing clouds of eggs and milt into the open water. As they dove up and down in giddy distraction, oil coated a fifth of their breeding grounds.

Previous spills had taught scientists that oil cripples the hearts of young fish, but until now it wasn't clear how. A study published this week reveals that crude oil blocks the transfer of potassium through heart cells, a process that regulates the beating of almost all hearts.

"The ability of a heart cell to beat," explained Barbara Block, marine sciences professor at Standford University, "depends on its capacity to move essential ions like potassium and calcium into and out of the cells quickly. This dynamic process, which is common to all vertebrates, is called 'excitation-contraction coupling.' We have discovered that crude oil interferes with this vital signaling process essential for our heart cells to function properly."

Oil disrupts the ion channel pores through which those molecules traverse cell membranes, as they go about their work of regulating heart rate and contractions.

Scientists from Stanford and the National Oceanic and Atmospheric Administration bathed tuna cardiac cells in low concentrations of crude oil, which were similar to what gulf tuna conceived during and after the 2010 spill might have encountered. Using electro-physiological techniques with names like "patch clamping" and "confocal microscopy," they recorded how ions passed through cell membranes and identified the proteins in those pathways that were affected by the chemicals in crude oil.

"The normal sequence and synchronous contraction of the heart requires rapid activation in a coordinated way of the heart cells," said Dr. Block. "Like detectives, we dissected this process using laboratory physiological techniques to ask where oil was impacting this vital mechanism."

So what happens to fish with clogged ion channels? According to the study, they suffer from slowed and irregular heartbeats that can lead to cardiac arrest.

"The protein ion channels we observe in the tuna heart cells are similar to what we would find in any vertebrate heart and provide evidence as to how petroleum products may be negatively impacting cardiac function in a wide variety of animals," said Block, noting that exposure to these hydrocarbons could lead to cardiac arrhythmias and bradycardia among many animals.

A report released last year by the National Wildlife Federation (NWF) confirmed that the gulf's dolphins, sea turtles, and many fish including the Atlantic bluefins were in fact continuing to die in record numbers three years after the 2010 spill – which is considered the worst spill in petrochemical history. And the tuna were already imperiled by overfishing, which has led to tense international haggling over appropriate fishing quotas.

"As top-level predators, [western Atlantic bluefin tuna] are indicators of ecosystem health," reported the NWF, describing how the oil spill had jeopardized an already tenuous recovery. "For species in peril, reductions of reproductive success and lower populations can be major impediments to recovery."

You've read  of  free articles. Subscribe to continue.
Real news can be honest, hopeful, credible, constructive.
What is the Monitor difference? Tackling the tough headlines – with humanity. Listening to sources – with respect. Seeing the story that others are missing by reporting what so often gets overlooked: the values that connect us. That’s Monitor reporting – news that changes how you see the world.

Dear Reader,

About a year ago, I happened upon this statement about the Monitor in the Harvard Business Review – under the charming heading of “do things that don’t interest you”:

“Many things that end up” being meaningful, writes social scientist Joseph Grenny, “have come from conference workshops, articles, or online videos that began as a chore and ended with an insight. My work in Kenya, for example, was heavily influenced by a Christian Science Monitor article I had forced myself to read 10 years earlier. Sometimes, we call things ‘boring’ simply because they lie outside the box we are currently in.”

If you were to come up with a punchline to a joke about the Monitor, that would probably be it. We’re seen as being global, fair, insightful, and perhaps a bit too earnest. We’re the bran muffin of journalism.

But you know what? We change lives. And I’m going to argue that we change lives precisely because we force open that too-small box that most human beings think they live in.

The Monitor is a peculiar little publication that’s hard for the world to figure out. We’re run by a church, but we’re not only for church members and we’re not about converting people. We’re known as being fair even as the world becomes as polarized as at any time since the newspaper’s founding in 1908.

We have a mission beyond circulation, we want to bridge divides. We’re about kicking down the door of thought everywhere and saying, “You are bigger and more capable than you realize. And we can prove it.”

If you’re looking for bran muffin journalism, you can subscribe to the Monitor for $15. You’ll get the Monitor Weekly magazine, the Monitor Daily email, and unlimited access to CSMonitor.com.

QR Code to Oil spills can stop tuna hearts, say scientists
Read this article in
https://www.csmonitor.com/Science/2014/0214/Oil-spills-can-stop-tuna-hearts-say-scientists
QR Code to Subscription page
Start your subscription today
https://www.csmonitor.com/subscribe