Lower Oxygen Levels in Oceans: Scientists Alarmed

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According to Yahoo! News, Scientists have found oxygen-depletion among Earth’s Oceans. While it is normal for the oceans to have pockets of oxygen-depleted waters, the odd and alarming trend is that these pockets have increased in size and have appeared closer to the surface; this affects the delicate balance of the ocean’s ecosystem. Could this be another trend toward the global warming climate change? Scientists are debating this answer.

Some scientists, such as National Oceanic and Atmospheric Administration (NOAA) Oceanographer Steve Bograd, are quick to blame the lower oxygen levels to global warming than to other reasons such as weather phenomena like El Nino or La Nina. Weather phenomena are shifts of weather that happen every 20 or 30 years in northern oceans.

“It’s a large disturbance in the ecosystem that could have huge biological changes,” said Bograd.

There are also scientists that believe it is too soon to tell whether or not this trend is due to global warming. Gregory Johnson, another oceanographer with the NOAA, along with other scientists has found changes in wind and ocean circulation since 2002 that have disrupted the delicate balance of up-welling and down-welling. They are now beginning to discover low-oxygen zones expanding near the shore.

“The depletion of oxygen levels in all three oceans is striking,” said Johnson. “[And] it is consistent with models of global warming, but the time frame is too short to know whether it is a trend or a weather phenomenon.”

Northerly winds pulled by Earth’s rotation cause surface water to drive away from the shore during the summer months. This process causes oxygen-poor water to surface, a process called up-welling. While the water does lack oxygen, it is rich in nutrients, fertilizing the phytoplankton that makes the Northwest’s continental shelf the richest ocean food chain in the world. Conversely, southerly winds reverse this process, called down-welling.

Areas of low oxygen, also known as hypoxia, have existed in the oceans for a long time. What alarms scientists is that these areas are rapidly expanding, and oceanographers such as Jack Barth are surprised by, “how this has become the new norm,” and scientists are, “seeing this trend year after year.”

To add to the list of things scientists are unsure of, it is uncertain how these expanding oxygen-poor areas are going to affect marine life. It is said that bottom-dwelling species are at greater risk since they are slower swimmers and less able to escape the lower oxygen levels. Though most fish can out-swim these dangers, there are some species like the Chinook salmon that may have to swim at shallower depths than they’re used to. Some species, such as various types of squid and jellyfish, can survive and even show preference to the lower oxygen levels. Though scientists are uncertain of what is to come of this trend, one thing is certain: this is definitely an alarming trend to be monitored.


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