diver.net

DEAD ZONES ON THE RISE IN WORLD OCEANS


dive-instructors.com, the first place to look for a dive instructor


[ Follow Ups ] [ Post Followup ] [ California Scuba Diving BBS ] [ FAQ ]

Posted by on August 19, 2006 at 23:38:12:

DEAD ZONES ON THE RISE IN WORLD OCEANS – RESEARCHERS FINGER CHANGES IN OCEAN CONDITIONS, POLLUTION: The Dead Zone -- it sounds so scary that Stephen King used it as the title for his 1979 psycho-thriller novel. Unfortunately, dead zones, or large swaths of ocean habitat unable to support marine life, are an increasingly common reality that is on the rise for a variety of reasons. In August, researchers at Oregon State University identified a 70-mile stretch of Oregon’s Continental Shelf littered with the carcasses of thousands of dead crabs, worms, sea stars, urchins and other organisms too slow to evacuate, and not a fish in sight.

Readings taken off the central Oregon coast near Cape Perpetua found dissolved oxygen levels at various depths ranging between 0.08 to 0.5 milliliters per liter; anything less than 1.4 is considered hypoxic for most marine life. Other areas were found hovering just above zero, a new low for the Pacific Coast of the U.S. Dead zones first made an appearance in the Pacific Northwest in 2002, and they have been observed in every year since then. This year, however, has revealed the worst case of hypoxia ever recorded in Oregon, and the extent of the damage has been shocking.

Oregon State University marine biologist Jane Lubchenco has been a lead investigator in this unprecedented die-off. Using a remote-operated underwater vehicle to view the dead zone through on-board video screens, she has described the area as “a crab graveyard,” both “shocking and depressing.” With dissolved oxygen levels 25 times lower than the low end of normal crab, lobsters, shellfish, and other slow-moving critters are suffocating while fish are being driven out of their normal ranges to more oxygen-rich waters. Scientists are blaming coastal upwelling of cold, oxygen-deprived deep water facilitated by winds out of the north. Although these upwellings are perfectly normal, they are typically offset by southerly winds that mix the cold water from the deep with warmer water richer in oxygen. This year, however, the southerly winds have, well, gone south. Researchers are not sure why the wind patterns are shifting, but they note that these changes are consistent with predictive climate change models. Although there is no evidence directly linking the dead zone to climate change, it could serve as a preview of things to come. California, too, is experiencing a warming trend. Captain Cameron Smith of the FV Bloodbath notes, “the fish are going north, past Pt. Arena. It’s quite tough to even come close to making the 75 fish per week.”

In July, hundreds of dead or ailing purple sea urchins have been washed into tide pools at the Little Corona Marine Life Refuge in southern California. As water temperatures climbed above 75°F, oxygen levels dropped below levels needed by the sea urchins. According to Dennis Kelly, professor of marine science at Orange Coast College in Costa Mesa, possible causes include the heat wave that struck the region, tide pool exposure at low tide, naturally occurring pathogens, pollutants, and overpopulation.

Unfortunately, this is not the first time dead zones have been observed in the region. The phenomenon was first observed in 2002, and has occurred every year since. According to Jack Barth, an OSU oceanographer, the changing ocean conditions cannot be directly linked to the El Niño/La Niña cycle, and the Decadal Oscillation remains a possibility. Nevertheless, the persistent occurrence of this deadly wave of hypoxic conditions is both unsettling and baffling. The extent of this year’s die off depends on what the prevailing winds do – southerly winds could assuage the lack of oxygen; northerly winds could worsen conditions.

On the opposite side of the country, development and pollution on Skidaway Island off the Georgia coast are sucking the oxygen out of the water creating yet another marine dead zone. By taking water quality samples from the local estuary over the last 20 years, Peter Verity, a professor at the Skidaway Institute of Oceanography, has documented a steady decline in dissolved oxygen levels. As blue crabs, shrimp, oysters, and fin fish die, less evolved life forms such as jellyfish move into the area. Indeed, Verity’s sampling has shown a 70 percent increase in jellies.

Pollution sources on the island include new construction of homes, condominiums, marinas and businesses. Heavy rains regularly transport fertilizers, sewage, oil and chemical pollution from lawns, golf courses, farms, homes, hotels, condominiums, and hardscapes of human development to the waterways and estuaries of this coastal environment. Decomposing blooms of algae and bacteria release carbon dioxide into the water and absorb the oxygen that animals need to live.

In Georgia, legal battles over whether the state has the authority to regulate coastal lands have stalled efforts to limit development in areas that flow into Georgia’s marshes and wetlands, vital nurseries for marine life that are considered among the most productive in the country. Environmental regulatory agencies are waiting for larger data sets to pinpoint the source of the die offs. Spud Woodward, the assistant director of the Georgia agency, which regulates marine fisheries, has taken a similar stance as the Oregon scientists who are trying to determine whether changing conditions are a result of human activities or natural fluctuations.

Strangely, Woodward has likened the situation to the debate over global warming. But unlike global warming, the American government has accepted that human activity in the form of polluted runoff, largely from agricultural fertilizer, is the cause of massive dead zones visible from space in the Gulf of Mexico and Chesapeake Bay – only two of 150 dead zones worldwide. It is unclear how long Georgia’s coastal waters will suffer before mitigation, reduction, and prevention of coastal pollution is implemented. If it doesn’t happen soon, Verity concludes, the cost of restoration – which has reached estimates of between $18 and $28 billion – will be yet another bill passed on to the next generation of taxpayers.

For more information on the recent proliferation of dead zones see the 12 August Associated Press article reporter by Joseph B. Frazier: www.washingtonpost.com/wp-dyn/content/article/2006/08/12/AR2006081200304.html; 9 August Seattle Times article by Hal Bernton, archives.seattletimes.nwsource.com/cgi-bin/texis.cgi/web/vortex/display?slug=deadzone09m&date=20060809; the 13 August Atlanta Journal Constitution article by Stacy Shelton, www.ajc.com/search/content/auto/epaper/editions/sunday/news_44ed7c0a112b20e71041.html; and the 4 August Associated Press article www.livescience.com/animalworld/060804_ap_sea_urchins.html.



Follow Ups:


Name:
E-Mail:
Subject:
Message:
Optional Link URL:
Optional Link Title:
Optional Image URL:
Post Background Color: White     Black
Post Area Page Width: Normal   Full
You must type in the
scrambled text key to
the right.
This is required to
help prevent spam bots
from flooding this BBS.
capcha
Text Key:

      


diver.net