Ocean

Lowering the pH of seawater affects the ability of shell-building organisms to build and maintain their shells. (Russ Hopcroft/Alaska Ocean Observing System)

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.

Learn more about OA

Alexandrium is the cause behind paralytic shellfish poisoning, or PSP. (Kachemak Bay National Estuarine Research Reserve)

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.

Learn more about HAB

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.

More about our warming oceans

Juvenile pollock. (Alaska Ocean Observing System)

Warming of the upper ocean is affecting the food web, resulting in changes in fisheries and other human activities dependent on ocean productivity.

Less food for fish

Climate models project that the southern Bering Sea will see more warm years with reduced sea ice. Krill and large copepods, important food young pollock, are decreasing in number. Less food has limited survival of fish during their first winter, and multiple consecutive warm years have ultimately resulted in fewer pollock surviving to adulthood.

Salinity changes

Alaska’s ocean waters are getting less salty due to more precipitation falling as rain rather than as snow in some regions. Rain melts glaciers and sea ice, and changes freshwater input from rivers. Changes in salinity—especially a layer of fresh water at the mouth of streams—may delay or otherwise alter normal passage of salmon from the ocean into streams.

Poster: The Ocean is our Grocery Store

Download the Poster

Full size printed posters are available. Poster dimensions are approximately 2' x 3'. Please contact us to find out more.