large ‘dead zone’ in the Gulf of Oman is increasing in size,
according to scientists who warn the oxygen-scarce area is worse than
previously thought and poses a threat to the environment. But what
does that mean?
dead zone in the Arabian Sea is now the world’s biggest Oxygen
Minimum Zone (OMZ). About the size of Scotland or Florida, the dead
zone almost covers the entire Gulf of Oman, which borders Iran, Oman,
Pakistan and the United Arab Emirates.
is a dead zone?
dead zone is an area of the sea or a large body of water that’s
almost entirely devoid of oxygen. The low-oxygen areas are called
dead zones as they can’t sustain marine life. Fish, animals and
plant life in the zones suffocate as a result of low oxygen levels,
while some marine life manages to swim away from the area, leaving it
began noticing increasing areas of dead zones in the 1970s. In 2008,
405 dead zones around the world were noted by Sweden's Göteborg
in Gulf of Oman
existence of the Gulf of Oman dead zone has been known for about 50
years, but the extent of the area has only recently been confirmed
thanks to the use of underwater robots, called Seagliders.
Arabian Sea is the largest and thickest dead zone in the world. But
until now, no-one really knew how bad the situation was because
piracy and conflicts in the area have made it too dangerous to
collect data,” Dr Bastien Queste from UEA’s School of
Environmental Sciences said. “We barely have any data collected for
almost half a century because of how difficult it is to send ships
remote-controlled submarines are the size of a small person and can
spend months underwater at 1km. They were deployed by researchers
from the University of East Anglia to the Gulf of Oman for eight
team’s findings have now been published in Geophysical Research
Letters. They found a strong decrease of oxygen in the afflicted zone
compared to pre-1990 levels, and also charted how the oxygen is
spread around the area across different seasons.
research shows that the situation is actually worse than feared –
and that the area of dead zone is vast and growing. The ocean is
suffocating,” Queste said.
causes dead zones?
zones can occur naturally, but also grow as a result of excessive
nutrient pollution from human activities, the National Oceanic and
Atmospheric Administration explains. Many chemical, physical and
biological factors combine to create dead zones, but nutrient
pollutions are the primary culprit. Nitrogen and phosphorus in
fertilizers run into the water, and then act as nutrients which
algae eventually dies and decomposes in the water. This then feeds
bacteria which consume oxygen around them, depleting the supply.
Climate change has exacerbated the issue, as warmer waters contain
Gulf of Mexico is home one of the largest dead zones, which occurs
each spring when farmers fertilize their land and the rain washes the
fertilizer into rivers and into the sea. An area in the Baltic Sea is
another large dead zone.
are dead zones bad?
zones are “a real environmental problem, with dire consequences for
humans too who rely on the oceans for food and employment.” Guete
worryingly, dead zones produce nitrous oxide, which is more damaging
to the environment than carbon dioxide.
warn that computer simulations of ocean oxygen reveal levels will
decrease over the next 100 years, with oxygen minimum zones growing.
The next step for researchers is further study to determine all of
the contributing causes of the increasing dead zone.