Low oxygen levels in oceans is an issue of concern: scientists

Scientists have said that the decrease of oxygen in the oceans, especially the waters surrounding the United States’ Pacific Northwest coast, may be another change brought by the global climatic changes being felt worldwide. The issue of concern arises as piles of Dungeness crab carcasses were found in some areas off the Washington state and Oregon, 25 year-old sea stars were killed, and colonies of sea anemones were crippled. If such continues, ecosystems and food chains in the ocean will be disrupted.

The Pacific, Atlantic, and the Indian oceans have proven to have hypoxia, or low oxygen levels over sometime. But the hypoxia seems to be spreading over square miles, especially towards the surface and in some places, such as the Pacific Northwest, it is encroaching on the continental shelf within sight of the coastline.

"The depletion of oxygen levels in all three oceans is striking," said Gregory Johnson, who is an oceanographer with the National Oceanic and Atmospheric Administration in Seattle.

In some spots off the Southern California coast, oxygen levels have dropped roughly 20 percent over the past 25 years. In other regions, oxygen levels might have declined by one-third over 50 years according to scientists reports.

They state that the changes are consistent with current climate-change models. Earlier studies have proven that the oceans are becoming more acidic as they absorb more carbon dioxide and other greenhouse gases. A marine researcher at the Oregon State named Francis Chan said, “If the Earth continues to warm, the expectation is we will have lower and lower oxygen levels.”

This is mainly due to the scientific fact that the surface waters absorb oxygen into the water, while also naturally circulating and bringing the deeper waters to the surface to gain oxygen then. But as the ocean temperatures rise, they tend to become a form of a ‘cap’ and stops these natural processes from happening.

However, it is still uncertain for scientists to know how these low oxygen levels will affect the ecosystems and food chains in the sea. Some fishes may swim out of danger but bottom-dwelling species may be at risk as they mover rather slowly to stay out of these low oxygen level zones. Species like the Chinook salmon may have to divert their regions and routes of swimming and swim at shallower depths. Jellyfishes may appreciate the low-oxygen levels, and the Jumbo squid can survive the decrease in oxygen in water as well.

But a large disturbance in the ecosystem may have large biological impacts.