WiLD Blog

By Kenneth R. Weiss
Los Angeles Times Staff Writer

May 2, 2008

Oxygen-starved waters are expanding in the Pacific and Atlantic as ocean temperatures increase with global warming, threatening fisheries and other marine life, a study published today concludes.

Most of these zones remain hundreds of feet below the surface, but they are beginning to spill onto the relatively shallow continental shelf off the coast of California and are nearing the surface off Peru, driving away fish from commercially important fishing grounds, researchers have found.

The low-oxygen, or hypoxic, zones may also be connected to the Pacific coast invasion of the Humboldt, or jumbo, squid. These voracious predators, which can grow 6 feet long, appear to be taking advantage of their tolerance for oxygen-poor waters to escape predators and devour local fish, another team of scientists theorizes.

Researchers believe these phenomena are linked to subsurface layers of hypoxic water in the tropical Pacific and Atlantic oceans that have been thickening over the last 50 years, according to the analysis published today in the journal Science.

The study, led by Lothar Stramma at the University of Kiel in Germany, warns that the spread of hypoxic waters that suffocate marine life is consistent with climate models forecasting what would happen as greenhouse gases accumulate in the atmosphere.

The trend, the study points out, eerily echoes a scenario that unfolded about 250 million years ago, when 95% of life on Earth went extinct after heat-trapping carbon dioxide spewing from volcanoes warmed the planet and the oceans became stripped of oxygen.

“If you warm waters, they hold much less oxygen,” said coauthor Gregory C. Johnson, an oceanographer with the federal Pacific Marine Environmental Laboratory in Seattle. “That’s the same as a bottle of soda water. If you open it warm, it’ll fizz all over the place. If you open it cold, it will slowly fizz out as it warms.”

More importantly, Johnson said, the lighter warm water creates a cap over the colder depths, making it less likely that oxygen-enriched surface water will mix with colder water. Other biogeochemical processes also rob oxygen from deeper waters, such as the decomposition and re-mineralization of dead plankton as it settles to the seafloor.

These vast low-oxygen zones that stretch far out to sea differ from the “dead zones” at the mouth of the Mississippi River and in near-shore waters around the world. These localized low-oxygen waters typically form after fertilizer-rich river discharges produce thick blooms of algae that suck the oxygen out of water after they die and decompose.

Marine turtles almost always return to the same beach to lay their eggs. The egg-laying sites are often far from the feeding areas and the females cross several hundred kilometers of ocean with no visual landmarks. How do they manage to return to the same spot?

A study by Simon Benhamou of the Center for Functional and Evolutionary Ecology at Montpellier, France, together with other groups, shows that the marine turtles use a relatively simple navigation system involving the earth’s magnetic field, and this allows them to return to the same egg-laying site without having the ability to correct for the deflection of ocean currents. This work, published in Current Biology and Marine Ecology Progress Series, should allow better conservation strategies for this endangered species.

Every 4 years, on average, Indian Ocean green turtles (Chelonia mydas) travel hundreds of kilometers to specific egg-laying areas, where they will lay 4 to 6 successive clutches. To better understand the navigation process and the sensory channels involved in this long-distance oceanic travel, the researchers have conducted a multidisciplinary study, involving biology and physical oceanography, in two series of experiments. In the Mozambique Channel, between the east coast of Africa and Madagascar, on the beaches of the French Islands of Europa and Mayotte, they caught turtles at the beginning of their egg-laying cycle, so that the animals were strongly impelled to return to this area to complete their cycle. After having Argos transmitters fitted to their shells in order to satellite track their return journey to the beach, the animals were released in open sea, several hundred kilometers from the egg-laying site.

The first experiment was to study the navigation system of the marine turtles and discover how they detect the ocean currents: are the turtles’ movements controlled by the currents or can they use them to their benefit? The study has shown that the marine turtles’ navigation system allows them to maintain their course towards the egg-laying site wherever they find themselves. It is almost as if they were equipped with a compass pointing towards the beach in question. So they can correct any deflection they are subject to: transport by boat, ocean currents… But, unlike human navigators, they are not able to correct for ocean drift in plotting their course. So the movements recorded by the satellite are a combination of deliberate action by the turtles and the effect of currents. So it appears that the turtles’ navigation system is relatively simple and may cause them to be wander at sea for long periods during adverse ocean conditions. One turtle released 250 km from its egg-laying site on Europa traveled more than 3 500 km in two months before returning there!

In the second experiment, the researchers have studied the effect of the earth’s magnetic field on the turtles’ navigation system. They have shown, for the first time in natura, that marine turtles use the magnetic field of the earth to orientate themselves. When this field is disturbed by placing a powerful magnet on their heads, turtle navigation is not as good. But the fact that they can still return to their original egg-laying site shows that the geomagnetic field is not the only information source that they use. Researchers think the turtles may also use their sense of smell like certain sea birds or homing pigeons. This hypothesis remains to be proven…

This work should improve conservation strategies for marine turtles, an endangered, officially protected species, by providing a better understanding of how they manage these long migrations between egg-laying and feeding areas.

Note: This story has been adapted from material provided by CNRS.  http://www.wetsand.com

posted by jose E. lopez

now these days sea turtles face a far more greater danger other than extinction, Pollution; companies dumping toxic waste in the earth’s oceans forces marine life to change their habitats and find new places to live which involve bitter conditions and unsuitabe places for marine species. Our governments should try to put an end to this and regulate the oil companies to stop this act of violence against our world.

This week the New Yorker’s Elizabeth Kolbert continues her groundbreaking analysis of global climate change with a look at how human related carbon emissions are turning the ocean acidic in “The Darkening Sea: What Carbon emissions are doing to the ocean.” Kolbert’s original work in The New Yorker is spelled out in her book, Field Notes from a Catastrophe. The article is an excellent summary of the reams of scientific research that has been published widely. Kolbert’s article should be required reading for anyone who believes that San Diego’s coast will be or has been immune from the impacts of climate change and that a small population of harbor seals represents a significant threat to our coastline.

Some of Kolbert’s observations include the following:

• “The concentration of carbon dioxide in the aid today—three hundred and eight parts per million—is higher than it has been at any point inn the past six hundred and fifty thousand years, and probably much longer.

• “At the current rate of emissions growth, carbon dioxide concentration will top five hundred parts per million—roughly double pre-industrial levels—by the middle of this century.”

• Increases in carbon dioxide levels “will produce an eventual global temperature rise of between three and half and seven degrees Fahrenheit, and that this in turn, will prompt a string of disasters, including fiercer hurricanes…and the inundation of many of the world’s major coastal cities.”

• “Already, humans have pumped enough carbon into the oceans—some hundred and twenty billion tons—to produce a .1 decline in surface pH…a .1 drop represents a rise in acidity of about thirty percent.”

• “Because of the slow pace of deep-ocean circulation and the long life of carbon dioxide in the atmosphere, it is impossible to reverse the acidification that has taken place.”

Kolbert, as did Ken Weiss did in his brilliant Alerted Oceans series in the Los Angeles Times, argues that this drop in pH levels will give way to an increase in ocean slime and jellyfish that will occupy ecological niches now filled by, well, fish and the rest of the ocean food chain.

The irony here, is that while Jerry Sanders, Scott Peters and the Stepford Wife public servants at the City’s Recreation Department squander public monies on dredging projects for Children’s Pool, continue to defend the bizarre rope barrier at La Jolla Shores, and oversee San Diego’s wasteful kelp eradication program, Mother Ocean will soon be taking its revenge on San Diego. The years of defending the dumping millions of gallons of sewage into the ocean, failure to clean up Mission Bay, criminal contempt for warnings about the antiquated sewage treatment system, spending millions on sand replenishment projects, and ignoring the corruption of the Bajagua project’s blocking efforts to reduce border pollution, are now coming home to roost.

If a small population of harbor seals freaks out the anti-seal brigade in La Jolla, imagine the response to beaches filled with slime and jelly fish. It is rumored that Jerry Sanders, like President Bush believes that global climate change is a hoax. Sorry, Jerry. Let’s see you finally, for once, take some leadership on the issue that will matter most to the future of San Diego.

This represents the single biggest threat to the ocean biodiversity on a global level. The oceans are in serious trouble and it doesn’t seem like there is much the Bush administration will do to correct this or admit there is a problem. Start looking for an more algae blooms. Serge

Experts Report Oceans Turning Acidic

By ANTHONY MITCHELL
Associated Press Writer

NAIROBI, Kenya (AP) — The world’s oceans are becoming more acidic, which poses a threat to sea life and Earth’s fragile food chain, a climate expert said Thursday.

Oceans have already absorbed a third of the world’s emissions of carbon dioxide, one of the heat-trapping gases blamed for global warming, leading to acidification that prevents vital sea life from forming properly.

“The oceans are rapidly changing,” said professor Stefan Rahmstorf on the sidelines of a U.N. conference on climate change that has drawn delegates from more than 100 countries to Kenya. “Ocean acidification is a major threat to marine organisms.”

Fish stocks and the world’s coral reefs could also be hit while acidification risks “fundamentally altering” the food chain, he said.

A big thanks to Fay Crevoshay and Aida Navarro and of course our gran amigo Jorge Campos for launching this spectacular campaign today in Acapulco with the heroic sea turtle defenders of Mexico. Serge 

INTERNATIONAL HERALD TRIBUNE 

Jorge Campos launches campaign to save marine turtles
 The Associated Press

Published: October 27, 2006
ACAPULCO, Mexico. Mexico’s former star soccer player Jorge Campos, teaming up with environmentalists in this Pacific coast resort, launched a campaign Friday to protect Mexico’s endangered marine turtles.
 
 Campos, who was the assitant coach for Mexico’s 2006 World Cup team, called on President-elect Felipe Calderon, who takes office Dec. 1, to dedicate more resources to protect marine turtles along the coast of Guerrero state, where Acapulco is located.
 
 ”Turtles are worth more alive than dead,” he said, adding that the turtles could draw millions of tourists to the region.
 
 Mexico is a major nesting area for several species of sea turtles, which are protected by law. Harvesting or selling their eggs is a criminal offense, punishable by up to nine years in prison and fines.
 
 Still each year, officials seize thousands of turtle eggs at Mexican markets. The eggs are considered a delicacy.
 
 Fewer than 1,000 adult female leatherback turtles are left in Mexico’s Pacific range, down from an estimated 70,000 to 90,000 in 1980, according to the World Wildlife Fund.