CHICAGO -- Local marine researchers looking into the catastrophic Deepwater Horizon oil spill have discovered why crude oil seems to impact the hearts of developing bluefin tuna, a potentially profound discovery with implications beyond the Gulf of Mexico.
Led by researchers at Monterey's Hopkins Marine Station, a paper being published Friday in the journal Science shows that byproducts of crude oil -- byproducts also found in many other pollution sources -- acts like a drug on heart cells, disrupting cardiac rhythms and even leading to heart attacks.
"The ability of a heart cell to beat depends on its capacity to move essential ions like potassium and calcium into and out of the cells quickly," said Barbara Block, a Hopkins researcher and leading expert on pelagic fish species. "... We have discovered that crude oil interferes with this vital signaling process essential for our heart cells to function properly."
Researchers presented their findings Thursday, to help kick off the American Association for the Advancement of Science's annual conference in Chicago.
The research is funded by the National Oceanic and Atmospheric Administration, Stanford University and the Monterey Bay Aquarium. It is part of ongoing studies assessing the ecological damage from the 2010 disaster.
The cellular-level process the paper puts under the microscope is common to all vertebrates, and researchers said further research should be done to see what other species are potentially impacted. Scientists examined polycyclic aromatic hydrocarbons, or PAHs, which can be found in coal tar, creosote, air pollution and storm water runoff from land.
BP, which leased the Deepwater Horizon platform, issued a statement saying the study inflates the danger crude oil poses to heart function and said tuna have biological defenses that can't be replicated in a laboratory.
"The paper provides no realistic exposure assessment, and it is scientifically inappropriate to take data from in vitro laboratory tests on isolated tuna heart cells and use it to make unsupported predictions about effects on a variety of live marine species or humans in the gulf -- effects that no one has observed or measured in the field," BP said in a statement.
The company did not directly rebut researchers' laboratory findings showing how crude oil impact heart cells.
Considered the biggest environmental disaster in U.S. history, the Deepwater Horizon spill dumped 4 million gallons of crude oil into the Gulf of Mexico. Years later, scientists continue to find deformed shrimp and fish, underweight dolphins suffering lung and liver disease, damage to deep-sea coral and more.
Fish counts down
Recent fish counts show the Atlantic bluefin tuna at 36 percent of their 1970 population baseline, though BP points out the number is up in recent years. Many other pelagic species, including yellowfin tuna, blue marlin and swordfish, also spawn in the area of the spill.
Block and Fabien Brette, a research associate in Block's lab and the study's lead author, conducted the research with NOAA's Northwest Fisheries Science Center in Seattle. The work was done at the Tuna Research and Conservation Center, jointly operated by Stanford and the Monterey Bay Aquarium.
"We've known from NOAA research over the past two decades that crude oil is toxic to the developing hearts of fish embryos and larvae, but haven't understood precisely why," said Nat Scholz, an ecotoxicology expert at the Northwest Fisheries Science Center and a study co-author. "These new findings more clearly define petroleum-derived chemical threats to fish and other species in coastal and ocean habitats, with implications that extend beyond oil spills to other sources of pollution such as land-based urban storm water runoff."
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