'Death zone' reappears in the United States

Viet Phuong

Off the western coast of America the ' dead zone ' continues to expand, the lack of oxygen regularly kills or repels life in this area. Researchers believe that the ' dead zone ' is a consequence of climate change on the earth and in the future it will not be strange.

This summer, the 'dead zone' off the coast of Oregon again reappeared, this is the sixth year of this phenomenon. 'Dead zone' is a phenomenon that occurs off the Pacific Ocean in the state of Oreon, where fish and crustaceans such as shellfish or mollusks such as oysters are massively killed because they do not have enough oxygen to exist. If

Fish die in mass at the 'dead zone'.(Photo: SK & D)

The researchers' opinions are correct, this year's ' death zone ' will not be the last appearance. Oregon State University marine researcher Jane Lubchenco said: 'It seems that this year's dead zone will be a normal phenomenon in the future'.

Through a video of a robot - diving Lubchenco and her colleagues discovered a graveyard of crustacean species on the continental shelf of the continental shelf . The fishermen tell of unusual fish that appear in unusual seas - and people are guessing that the fish are looking for a way to escape the "dead zones".

The two coastal cities of Newport and Cape Perpetua are located 40km apart. Here the researchers measured oxygen content in seawater. The results show that there are samples of oxygen content equal to 1/6 of the normal value. However, the result this year was not as bad as last year. According to 'New York Times' reported last year, the 'dead zone' was larger than in previous years, even four times more than in 2002. Back then the area of ​​' death zone ' extended from the coastal area. Southern Oregon until the Olympic Peninsula peak in Washington state, over 600km long.

Climate change is the cause of changing wind regime. Dead zones form when the wind is not normal, causing water in the deep oxygen to be exposed to the surface. Thereby, nitrogen and other nutrients are distributed in the water column - this leads to the strong development of plankton. This process is very precious but leads to the consumption of large amounts of oxygen which is already small in seawater. Small animals and plants form births Plankton after death will sink to the bottom of the sea. They decompose at the bottom of the sea and this process negatively affects oxygen levels.

Lubchenco said: 'What we have seen for six years continuously shows that something very fundamental is changing the conditions in the coastal area.' Scientists believe that the change in global air circulation is the cause of this phenomenon. The so-called Jetstreams, high and fast winds on high, may have changed the wind regime off Oregon. That means the ' dead zone ' is a consequence of climate change.

The problem that researchers point out is whether this mysterious oxygen deficiency is happening every year and how it affects the ecosystem in this coastal area. Lubchenco marine biologist made a comparison: 'Marine ecosystems also need a long time to recover similar to the recovery of terrestrial ecosystems after the Mount St. volcano outbreak. Helens'.