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  Yahoo News 7 Dec 06
Warmed-up oceans reduce key food link
By Seth Borenstein, AP Science Writer

Yahoo News 7 Dec 06
Global warming to have major impact on ocean food web: study

PlanetArk 7 Dec 06
Global Warming Will Stifle Oceans - Scientists
Story by Jeremy Lovell

LONDON - Global warming will stifle life-giving microscopic plants that live in the surface layer of the oceans, cutting marine food production and accelerating climate change, according to a study published on Wednesday.

Phytoplankton are not only the foundation of the marine food chain, but every day they take more than 100 million tonnes of carbon dioxide out of the atmosphere, scientists from Oregon State University, NASA and four other institutions said.

But as global warming heats the surface layer of the ocean it becomes lighter and therefore separated from the cooler depths from which the phytoplankton get many of their nutrients.

This cuts their numbers, not only reducing the food in the oceans but slashing the amount of carbon dioxide they take from the air and therefore accelerating the climate warming process.

"Rising levels of carbon dioxide in the atmosphere are a key part of global warming," said lead researcher Michael Behrenfeld. "This study shows that as the climate warms, phytoplankton production goes down, but this also means that carbon dioxide uptake by ocean plants will decrease ... making the problem worse," he added.

Despite their tiny size, phytoplankton account for about half of the photosynthesis on Earth -- converting vast quantities of atmospheric carbon dioxide into organic carbon as food for the planet's marine ecosystem.

The study, published in the science journal Nature, comes from a decade-long analysis of the oceans by NASA's SeaWiFS satellite which measured the changing colours of the waters caused by changing levels of phytoplankton.

The higher the concentrations of these tiny plants, the greener the water.

The scientists -- who also came from the University of California/Santa Barbara, Princeton University, Rutgers University and the University of Maine -- found local variations but a global drop in numbers with higher temperatures.

"This clearly showed that overall ocean productivity decreases when the climate warms," Behrenfeld said. Scientists predict that global temperatures will rise by between two and six degrees Celsius by the end of the century, due mainly to carbon dioxide from burning fossil fuels for power and transport.

But they also fear that beyond two degrees of warming the planet's climate could trip the so-called feedback mechanism with the rising heat releasing even more greenhouse gases than being produced by human activities.

A comprehensive study last month by former World Bank chief economist Nicholas Stern found that acting now to tackle climate change could cost one percent of global economic output -- a figure that rises 20-fold if action is delayed.

Yahoo News 7 Dec 06
Global warming to have major impact on ocean food web: study

PARIS (AFP) - A new study of the oceans suggests that phytoplankton -- the vital first link in the food chain of the seas -- will be hugely affected by global warming.

Fisheries in the tropics and mid-latitudes could be badly hit by the loss of these micro-organisms as a result of warmer waters, the paper implies.

Phytoplankton grow in the upper layers of the ocean, needing light as well as nitrogen, phosphate and iron to grow. These nutrients come from the cold deep ocean, and are brought to the surface by currents.

Oregon State University botanist Michael Behrenfeld and colleagues pored over nearly a decade's-worth of satellite data to see how these tiny, unsung plants of the ocean surface respond to shifts in temperature.

The NASA satellite SeaWiFS uses sensors to record light that is reflected back by the ocean. Banks of phytoplankton can be spotted because they contain chlorophyll, which absorbs red and blue parts of the light spectrum. Behrenfeld's "map" of phytoplankton found that the mass underwent two big changes over the study period.

In 1997-98, phytoplankton increased, matching a period when the El Nino effect was in reverse and the seas were relatively colder. Production of phytoplankton then declined from 1999 to 2004 as El Nino went back into an extended warming cycle. There was then a rise from 2005 to 2006.

The scientists say the results clearly link the sea's surface temperature with the abundance of phytoplankton, and thus provide an excellent indicator of what could happen in a warming climate. Their paper appears in Thursday's issue of Nature, the weekly British science journal.

If -- as some simulations suggest -- global warming will lead to more frequent or permanent El Ninos, then the distribution of ocean biomass could be radically reshaped, the authors say.

The biggest victims would be tropical and mid-latitude waters. In these regions, the light is good for phytoplankton photosynthesis but warmer water also tends to "sit" on denser, colder waters, which means there will be less upwelling of the vital nutrients.

Conversely, colder, higher-latitude seas could benefit. These regions get less light, which is bad for photosynthesis, but they offer a good nutrient flow because of strong upwelling from the ocean floor.

Very often, though, these currents are so intense that the phytoplankton are drawn hundreds of metres (feet) into the ocean depths, where sunlight does not penetrate.

In the future, higher temperatures and an influx of fresh water from precipitation and melting ice may help dampen the currents, which would thus spur phytoplankton growth.

In a commentary on the research, Scott Doney, a geochemist of Woods Hole Oceanographic Institution in Massachusetts said there remained many unknowns about the future of phytoplankton.

"Ecosystems are complex and nonlinear... and unexpected phenomena may arise as we push the planet into this unknown climate state," said Doney.

Phytoplankton are not just an essential first link in the food chain on which other ocean lifeforms depend. They also absorb carbon dioxide (CO2) from the atmosphere as part of photosynthesis -- so any disruption to this process could accelerate the climate-change mechanism.

Roughly 100 million tonnes of carbon are gobbled up each day by phytoplankton, according to the Behrenfeld study. A similar amount of carbon sinks to the seafloor, through dead phytoplankton, or is gobbled up by other marine life which feed on phytoplankton.

Other factors that influence phytoplankton growth include dust blown from the land, and variations in solar radiation.

Yahoo News 7 Dec 06
Warmed-up oceans reduce key food link
By Seth Borenstein, AP Science Writer

WASHINGTON - In a "sneak peak" revealing a grim side effect of future warmer seas, new NASA satellite data find that the vital base of the ocean food web shrinks when the world's seas get hotter.

And that discovery has scientists worried about how much food marine life will have as global warming progresses. The data show a significant link between warmer water — either from the El Nino weather phenomenon or global warming — and reduced production of phytoplankton of the world's oceans, according to a study in Thursday's journal Nature.

Phytoplankton are the microscopic plant life that zooplankton and other marine animals eat, essentially the grain crop of the world's oceans.

Study lead author Michael Behrenfeld, a biological oceanographer at Oregon State University, said Wednesday that the recent dramatic drop in phytoplankton production in much of the world's oceans is a "sneak peak of how ocean biology" will respond later in the century with global warming.

"Everything else up the food web is going to be impacted," said oceanographer Scott Doney of the Woods Hole Oceanographic Institute. He was not involved in the study.

"What's worrisome is that small changes that happen in the bottom of the food web can have dramatic changes to certain species at higher spots on the food chain," Doney said.

This is yet another recent scientific study with real-time data showing the much predicted harmful effects of global warming are not just coming, but in some cases are already here and can be tallied scientifically, researchers said.

A satellite commissioned by NASA tracked water temperature and the production of phytoplankton from 1997 to 2006, finding that for most of the world's oceans when one went up the other went down and vice versa, Behrenfeld said.

As water temperatures increased from 1999 to 2004, the crop of phytoplankton dropped significantly, about 200 million tons a year. On average about 50 billion tons of phytoplankton are produced yearly, Behrenfeld said.

During that time, some ocean regions, especially around the equator in the Pacific, saw as much as a 50 percent drop in phytoplankton production, he said.

However, the satellite first started taking measurements in 1997 when water temperatures were at their warmest due to El Nino. That's the regular cyclical warming of part of the Pacific Ocean that affects climate worldwide. After that year, the ocean significantly cooled until 1999 and the phytoplankton crop soared by 2 billion tons during those two years.

"The results are showing this very tight coupling between production and climate," Behrenfeld said.

As less food is produced by phytoplankton the oceans get bluer in color, he noted. Phytoplankton, which turn sunlight into food, need nutrients such as nitrogen, phosphates and iron from colder water below, Behrenfeld said. With warmer surface water, it is harder for the phytoplankton to get those nutrients.

Other oceanographers agree with the El Nino link but said that with only a decade of data it is harder to make global warming connections.

"It's something you certainly can't ignore, because its potential is quite significant," said the Woods Hole Institute's James Yoder. "But there are some caveats because of the shortness of the record." Behrenfeld said his study verifies the physical mechanism — how phytoplankton react to warm water — that has been predicted in computer models, thus verifying dire warnings.

Another worry is that with reduced phytoplankton, the world's oceans will suck up less carbon dioxide, increasing the Earth's chief global warming gas, said NASA ocean biology project manager Paula Bontempi.

That's because phytoplankton take carbon dioxide out of the atmosphere in making food. This is at least the third significant peer-reviewed research paper in the past six months showing that long-anticipated global warming biological side effects are already happening.

Other studies looked at global warming connections to wildfires and die-offs of plant and animal species. "What you're looking at is almost an avalanche of each individual effect," said Stanford University biological sciences professor Stephen Schneider.

"As it gets warmer and as we measure more things, the evidence accumulates."
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