As if fish didn’t have enough to worry about, now those near coastal areas are threatened by an unprecedented number of dead zones, says a study being published Friday in the journal Science. The number of dead zones — oxygen-deprived areas that can no longer support marine life — has doubled every decade since the 1960s, and the zones have been getting bigger and badder. Researchers counted over 400 dead zones worldwide, the combined area of which is bigger than the state of Oregon. “We can say that human activities really screwed up oxygen conditions in our coastal areas,” said Robert J. Diaz, the study’s lead author. Up where they spray all day in the sun, chemical fertilizers from farms send nitrogen-rich runoff downstream and out to sea, where it spurs the production of algae; as the algae sink to the bottom and decompose, huge amounts of oxygen are sucked up. The resulting dead zones in turn kill huge amounts of sea life. The researchers say fertilizer pollution needs to be reined in.