Ocean acidification (OA)
Ocean acidification is the long-term lowering of average global ocean pH.
As concentrations of atmospheric carbon dioxide (CO2) increase, some of this CO2 is absorbed by the ocean. This triggers chemical reactions that lead to lower pH and decreased concentration of carbonate ions in the oceans.
The current rate of change of OA is faster than at any time on record. Scientists estimate that the ocean is 30% more acidic today than it was 300 years ago, traceable to increasing levels of atmospheric CO2 from fossil-fuel combustion and land-use change.
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Harmful algal blooms (HAB)
Warmer ocean temperatures have allowed some harmful algal species to flourish. Algae-eating creatures like zooplankton, clams, oysters, mussels, and small fish eat algae can accumulate algal toxins in their tissues. The toxins are passed up the food chain to fish, birds, marine mammals, and humans as they consume the contaminated organisms. Toxic algae can be fatal when consumed in high enough quantities.
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The oceans are getting warmer
The recent increase of ocean temperatures is the greatest that has occurred in the past 1000 years, and the ocean off the coast of Alaska has warmed far more rapidly than other areas.