Between 2002 and 2014, six mass strandings took place in Greece, the Canary Islands and Almería in southeastern Spain, but the dead whales did not appear to be malnourished or sick. However, they displayed “abundant gas bubbles” throughout their veins, blood clots in multiple organs and microscopic hemorrhages “of varying severity” in body tissues.
Beached whales may have experienced “a fight or flight response” that overrode a key diving adaptation: the lowering of heart rate, which reduces oxygen consumption and prevents nitrogen accumulation. The result was hemorrhages and “massive bubble formation in their tissues,” de Quirós explained.
These symptoms of decompression sickness likely afflicted the whales after they were spooked by sonic blasts, according to the study.