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Commercial ocean fertilization: a wise use of scientific discovery?

Ocean fertilization as a means to reduce or mitigate the greenhouse gas carbon dioxide (CO2) and stimulate fish production is a theory that has gained growing attention in the media and among some scientists, both pro and con. Penny Chisholm, the McAfee Professor of Engineering, is concerned that proponents of the approach ignore critical results from experiments that are aimed at studying the potential unintended consequences of ocean fertilization.

Dr. Chisholm, a professor in the Department of Civil and Environmental Engineering and the Department of Biology, is part of a National Center for Research on Ocean Carbon Sequestration sponsored by the US Department of Energy. Her role is to insure that adequate attention is given to unintentional consequences in developing hypothetical ocean fertilization scenarios.

"First and foremost, one cannot predict the results of sustained fertilization (as would be required for any lasting effect) from the short-term, small-scale scientific experiments that have been conducted," she warned.


Ocean-fertilization proposals call for taking fertilizer (for example, iron) from the land and putting it into the oceans to stimulate photosynthesis in microorganisms known as phytoplankton. Photosynthesis converts CO2 gas into organic carbon (e.g. sugars, fats and proteins), the mass of living organisms.

Worrisome uncertainties have arisen among many scientists regarding schemes to reduce CO2 in the earth's atmosphere and to stimulate fish production by increasing the growth of phytoplankton. These uncertainties are being studied by Professor Chisholm, who has said there is a "desperate need" for an open discussion of these options among scientists and stakeholders "so we can make the best use of our scientific knowledge and develop sound international agreements on the future use of the Ocean Common."

But attempts to fertilize the ocean on a large scale are already in the advanced stages of development. Dr. Michael Markels Jr., an entrepreneur, has obtained both rights and US patents to proceed with fertilization of at least 100,000 square miles of the Marshall Islands ocean area, roughly the size of Nevada.

"When applied to large areas of the barren tropical seas, ocean farming can increase the phytoplankton, the base of the food chain," Dr. Markels said. "This can result in an increase in fish catch by a factor of 400 or more. A 53,000-square-mile ocean area might see the fish catch go to 50 million tons per year. The carbon dioxide absorbed initially could exceed the production by the United States from the burning of fossil fuels." (He discusses his ocean-farming idea in this web document.)

These claims reflect a wider desire in society both to reduce global warming from elevated CO2 in the atmosphere, and to increase the food supply to support a rapidly increasing global human population. They are predicated in theory upon three small-scale recent ocean fertilization experiments that have shown that addition of iron can stimulate phytoplankton growth in high-nutrient regions of the open seas. In one, a group of oceanographers including Professor Chisholm found that the addition of iron into certain small locations in the equatorial Pacific Ocean caused the phytoplankton to suddenly grow in abundance.

However, Professor Chisholm said, "the stimulation of the phytoplankton that we saw was a result in part of the uncoupling of the food web: the natural predators of these tiny plant cells did not have time to respond to their increased food supply and keep it in check. Yes, there were more phytoplankton when iron was added, but they were different phytoplankton than were there before. The entire community shifted to a newer group of species, and we do not know what the consequences of this would be to the ecosystem in the long term. Different species at the base of the food web implies different species at the top. So if you fertilize for fish, you will probably get different fish than you intended. Will they be species that we want?"

Not all parts of the ocean lend themselves to success in these schemes, Professor Chisholm said. The equatorial and southern ocean are rich in excess nitrogen and phosphorus (two principal elements required for phytoplankton growth) but lack iron (another primary element which plankton require). The addition of iron to the ocean in those regions is thus theoretically feasible, but places like the Marshall Islands are nutrient poor, requiring the addition of another element, phosphorus, which Dr. Markels has proposed. While this might stimulate fishing and more jobs for the local Marshall Islanders, the addition of iron and phosphorus could stimulate the disastrous growth of a little-understood blue-green algae which is known to produce toxins as a byproduct of its growth.


"When we operate outside the bounds of Nature's ability to assimilate our waste, there are consequences to pay," said Professor Chisholm. "We are looking at ocean fertilization as a quick fix for burning too much fossil fuel and for overfishing. There is no quick fix. It won't work, and the side effects will open up a whole new set of environmental problems. The oceans are a tightly linked physical-chemical-biological system, and you can't tamper with one part without it resonating through the whole system.

What measures can be taken to control existing ocean fertilization proposals? "We need laws," she said. "We need to do a lot more research. We need to have models that include the whole system response and not just the carbon fixation, and right now models are not capable of having that much complexity--it's computationally impossible. We need to have free, open dialogues between all the stakeholders, including the scientists and the policy people. There's never even been a symposium on this--that's how little we've done. The only thing that will stop this is international law."

Professor Chisholm noted that fertilization of the ocean would really be intentional planetary manipulation on a global scale. "The oceans are the only frontier left. Do we want to just jump right in and make the same mistakes? I think that the whole issue has gotten much farther than it should have already simply because of lack of public awareness."

On January 25, 2000, Professor Chisholm will give an invited lecture on "The Invisible Forest: Phytoplankton and Global Climate" as part of the Capital Science Lecture Series of the Carnegie Institution in Washington, DC.

A longer version of this article originally appeared in the October 1999 issue of the CEI's newsletter, Initiatives in Environment and Sustainability.

A version of this article appeared in MIT Tech Talk on November 3, 1999.

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