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CORVALLIS, Ore. - The recent agreement by nearly 200 countries to halt plans for fertilizing the world's oceans to combat global warming is prudent until more research is done, say scientists from Oregon State University who have conducted experiments with the technique.

The agreement was reached at the United Nation's Convention on Biological Diversity in Germany after days of debate, according to a report by Reuters. Fertilization proponents say adding nutrients to the oceans can trigger the growth of carbon-absorbing phytoplankton. Opponents counter that the process has not been adequately tested and could - among other side effects - lead to the proliferation of undesirable phytoplankton species.

Pete Strutton, Zanna Chase, and Burke Hales, faculty members in the College of Oceanic and Atmospheric Sciences at Oregon State, were part of an iron fertilization study in the Southern Ocean in 2002 and have conducted recent studies on algal blooms off the West Coast of the United States. Strutton said it is possible to trigger plant growth in the oceans by adding nutrients, but added that it isn't easy to control what grows and what doesn't.

"We already know that adding iron to the ocean usually alters the species composition of the phytoplankton community," Strutton said, "and it seems likely this would occur as a result of commercial applications. What if, instead of a beneficial species of phytoplankton, the fertilization inadvertently caused toxic diatoms like Pseudonitzschia to flourish?"

Strutton specializes in the study of such harmful algal blooms, including Pesudonitzschia, a species that can become toxic during certain conditions and create domoic acid. Domoic acid accumulates in the tissues of shellfish and has caused closures of clam and mussel harvests in the Pacific Northwest.

Humans who consume shellfish with high levels of domoic acid may suffer vomiting, diarrhea, disorientation and memory loss; in severe cases, domoic acid can result in comas and even death.

Iron fertilization can have other unintended consequences, Strutton said.

"As you increase phytoplankton levels, you can alter the absorption of light, potentially leading to more heating of the upper ocean and more stratification of ocean waters," he pointed out. "At the same time you are trying to enhance the growth of plant life in one area, you may be depleting nutrients nearby and affecting adjacent ecosystems."

Chase says there have been about a dozen scientific experiments involving iron fertilization, and in each one the amount of carbon absorbed by the additional plant growth has been less than expected.

"That has taken some of the wind out of the sails for iron fertilization as the silver bullet that will reverse global warming," Chase said.

The OSU researchers say they can't speak for the entire scientific community, but point out that many scientists would support the moratorium to gain time to conduct the necessary research to answer some of the tough questions about the impacts of ocean fertilization, as well as the amount of carbon that could be sequestered.

Additional small-scale studies, like those they conducted in 2002, are the right approach, Strutton said.

In their 2002 study in the Southern Ocean, Strutton, Chase, Hales and colleagues found that adding iron to the water did increase biological productivity and promote oceanic carbon dioxide uptake. The long-term effect on atmospheric CO2 was less clear, especially on a broad scale. The three OSU researchers were among nearly four dozen scientists on the research cruise, who reported their findings in Science.

The OSU researchers also have been involved in studies of natural iron fertilization in Oregon. A study they published last year described why the Pacific Ocean off Oregon is so biologically productive - a result of high amounts of iron being washed to sea from the state's numerous rivers, and a wide continental shelf to store the iron until seasonal upwelling.

That research, published by the American Geophysical Union in its journal, Geophysical Research Letters, found iron concentrations in Oregon rivers to be up to 1,000 times higher than ocean water. California, in comparison, has fewer rivers and a shallower shelf than Oregon, and is considered iron-deficient in comparison.