mongabay.com logo About  |   Contact  |  Mongabay on Facebook  |  Mongabay on Twitter  |  Free newsletter
Rainforests | Tropical fish | Environmental news | Blog | For kids | Madagascar | Photos | Non-English languages | Tropical Conservation Science
SHARE:
print


New NASA image reveals the oceans' dead zones
Jeremy Hance
mongabay.com
July 22, 2010



A new image by NASA reveals the extent of the world's marine dead zones, which a study in 2008 found were doubling every decade. At that time 415 dead zones had been identified worldwide. Dead zones are regions of the ocean where dissolved oxygen has fallen to such low levels that most marine species can no longer survive. Such conditions are often seasonal.

The so-called dead zones are caused by agricultural runoff, especially nitrogen-rich fertilizers, as well as the burning of fossil fuels. Pollutants from these sources cause marine eutrophication, whereby the ecosystem receives too many nutrients, triggering massive algae blooms, which eventually die and are broken down bacteria. In breaking down the algae blooms, the bacteria consume excessive amounts of oxygen, essentially starving the marine system. Therefore the largest and most extreme dead zones occur near high populations and run-off areas for agriculture fertilizers.

There are a few places in the world where low-oxygen waters are naturally occurring, such as the Bay of Bengal and southern Africa's Atlantic west coast. Species in these regions have evolved greater resilience to low oxygen conditions, however even these areas are threatened by anthropogenic sources of nutrients.




Created by satellite, the red circles on this map show the location and size of many of our planet’s dead zones. Black dots show where dead zones have been observed, but their size is unknown. Darker blues in this image show higher concentrations of particulate organic matter, an indication of the overly fertile waters that can culminate in dead zones. Image courtesy of NASA. Click on image to enlarge.








Related articles

Climate change, ocean acidification may doom jumbo squid

(12/15/2008) Ocean acidification — driven by rising carbon dioxide levels in the atmosphere — may hurt the Humboldt squid, report researchers writing in the journal Proceedings of the National Academy of Sciences.


Marine 'dead zones' double every decade

(08/14/2008) Dead zones have spread across the ocean at alarming rates. Currently 415 sites, usually along coastlines, have shown signs of seasonal to persistent hypoxia—a severe lack of oxygen. In a new essay in Science, researchers Robert Diaz and Rutger Rosenberg argue that marine dead zones have "become a major worldwide environmental problem". Marine dead zones now occupy a portion of the ocean equal to that of the United Kingdom and continue to grow, doubling every decade since the 1960s and showing no sign of abating.


Ocean dead zones have nearly quadrupled since 1994

(04/03/2008) Coastal areas worldwide are suffering from over-enrichment of their waters by nitrogen and phosphorus, finds a new study from the World Resources Institute (WRI). This over-enrichment, known as eutrophication, causes numerous environmental problems, eventually devastating coastal environments. In overly nutrient-rich waters phytoplankton, micro- and macroalgae grow to excessive portions; these 'algal blooms' diminish subaquatic vegetation, damage coral reefs, and deplete populations of fish, shellfish, marine mammals, and sea birds. In the worst case scenarios the massive algal blooms form hypoxic or dead zones due to loss of oxygen in the water, essentially condemning the ecosystem.









CITATION:
Jeremy Hance
mongabay.com (July 22, 2010). New NASA image reveals the oceans' dead zones. http://news.mongabay.com/2010/0722-hance_deadzones_nasa.html


Tags:
dead zone marine crisis marine animals eutrophication jeremy hance green oceans environment fertilizers fossil fuels Photos Satellite Imagery technology

print



Environmental news index | RSS | News Feed | Twitter | Home


Advertisements:





Mongabay Store
Wildlife of Madagascar T-shirt
Wildlife of Madagascar T-shirt
Bold and Dangerous - Pygmy tyrant t-shirts
Bold and Dangerous - Pygmy tyrant
Love me before I'm gone - Gladiator frog t-shirts
Love me before I'm gone - Gladiator frog
Licking this frog may make you crazy t-shirts
Licking this frog may make you crazy




DON'T LIKE ADS? Become a mongabay supporter


WEEKLY NEWSLETTER
Email:


RECENT FEATURES
As Amazon deforestation falls, food production risesAs Amazon deforestation falls, food production rises
Biggest environmental news stories of 2011Biggest environmental news stories of 2011
The year in review for rainforestsThe year in review for rainforests
Our top nature pictures of 2011Our top nature pictures of 2011


POPULAR PAGES
Rainforests
Rain forests
Amazon deforestation
Deforestation
Deforestation stats
Why rainforests matter
Saving rainforests
Amazon rainforest
Congo rainforest
Deforestation data
Rainforest canopy

Special sections
New Guinea
Finding new species
Sulawesi
Madagascar
Borneo
REDD

News
Most popular articles
Worth saving?
Forest conservation
Cell phones in Africa
Seniors helping Africa
Saving orangutans in Borneo
Palm oil
Amazon palm oil
Future of the Amazon
Cane toads
Dubai environment
Investing to save rainforests
Visiting the rainforest
Biomimicry
Defaunation
Blue lizard
Extinction debate
Extinction crisis
Industrial deforestation
Save the Amazon
Rainforests & REDD
Brazil's Amazon plan
Avatar story
Amazon ranching

News topics
Amazon
Biofuels
Brazil
Carbon Finance
Conservation
Climate Change
Deforestation
Energy
Happy-upbeat
Indonesia
Interviews
Oceans
Palm oil
Rainforests
Wildlife
MORE TOPICS



Non-English Sites
Chinese
French
German
Indonesian
Italian
Portuguese
Spanish
Other languages

Nature Blog Network







Photos
Brazil photos
Brazil

China photos
China

Colombia photos
Colombia

Costa Rica photos
Costa Rica

Deforestation photos
Deforestation

Gabon photos
Gabon

India photos
India

Indonesia photos
Indonesia

Kenya photos
Kenya

Madagascar photos
Madagascar

Peru photos
Peru

Peru photos
Rainforest



ABOUT
Mongabay.com seeks to raise interest in and appreciation of wild lands and wildlife, while examining the impact of emerging trends in climate, technology, economics, and finance on conservation and development (more)

Help support mongabay.com when you buy from Amazon.com


CALENDARS



BOOKS BY MONGABAY AUTHORS
Rainforest book for kids Conservation in an age of mass extinction


FREE WEEKLY NEWSLETTER



HIGH RESOLUTION PHOTOS / PRINTS








Copyright mongabay 2010

Carbon dioxide (CO2) emissions generated from mongabay.com operations (server, data transfer, travel) are mitigated through an association with Anthrotect,
an organization working with Afro-indigenous and Embera communities to protect forests in Colombia's Darien region.
Anthrotect is protecting the habitat of mongabay's mascot: the scale-crested pygmy tyrant.