By: Kate Good
Off the shore of Washington and Oregon low oxygen levels in the Pacific has caused the death of hundreds of Dungeness crabs. Like mammals, underwater species need oxygen to survive. In a recent study, marine researchers at Oregon State believe that the temperature increase associated with global climate change is directly linked to lowering oxygen levels in oceans.
Areas of hypoxia (lacking oxygen) are common in the deep ocean, however, it appears that areas in the Pacific, Atlantic and Indian oceans are spreading. This phenomenon can be caused by the excess of nutrients within water, causing large increases of algae growth. As algae levels rise, the ability of sunlight to penetrate water decreases along with the amount of oxygen that can be dissolved. As algae die and breakdown they consume oxygen, if the oxygen is not replaced, the result is a dead zone.
Scientists believe that as water temperatures rise, the warm water on the surface acts as a cap, inhibiting the natural circulation patterns, disallowing deep waters from reaching the surface where it can be replenished with oxygen.
There is a delicate balance between upwelling and the ocean ecosystems, as this process provides many low dwelling species with oxygen. Scientists do not yet know the future implications that will follow with mass oxygen depletion. However, the large amount of dead Dungeness crab illustrates the dire consequences of oxygen depletion.
Though hypoxia takes place in the deep ocean, humans play a large role in its occurrence. After rain, or excessive watering, the fertilizers used on agricult
ural fields, golf courses, and suburban lawns runoff into lakes and streams that lead to major bodies of water. The effect that fertilizer has on plants on land is the same with plants in the ocean, however, when underwater excessive plant growth has serious consequences.