Dr. Jim Cowan of Louisiana State University's Department of Oceanography and Coastal Sciences, believes PAHs, weathered from leaked oil on the seabed, are likely the cause of the mutations [REF].
A 2014 study of the effects of the oil spill on bluefin tuna, published in the journal Science, clarifying the mechanics by which PAH kill fish, found that the toxins from oil spills can cause irregular heartbeats leading to cardiac arrest.