‘Fix’ found for
UH scientists join in a study
to see if small ocean plants can
help absorb carbon dioxide
Increasing the number of microscopic plants in the ocean could play a role in slowing global warming, suggest experiments in the Southern Ocean reported in today's issue of Science magazine.
The Southern Ocean Iron Enrichment Experiments, which used iron to fertilize and grow microscopic plants over thousands of square miles of ocean, was run by 100 scientists from 18 institutions, including four from the University of Hawaii.
Through photosynthesis, each bloom absorbed more than 30,000 tons of carbon dioxide, a major greenhouse gas, suggesting a massive ocean fertilization program to remove it from the atmosphere might slow global warming, according to the article.
"Others have suggested this is a fix for global warming, but people are very divided on the issue," said Robert Bidigare, UH oceanography professor and director of the Marine Bioproducts Engineering Center.
The experiments were conducted to understand changes in Earth's climate during ice ages, Bidigare said.
Ken Buesseler, of Woods Hole Oceanographic Institution, and Jim Bishop, of Lawrence Berkeley National Laboratories, said in separate Science articles that removal of vast amounts of carbon dioxide from the atmosphere during ice ages could have helped cool Earth and that it might be an answer to global warming.
One of the questions was whether the carbon dioxide would return to the atmosphere or sink to the deep sea as the phytoplankton died or were consumed by microbes.
Much of the carbon dioxide sank far below the surface, Buesseler and Bishop said.
Bidigare said, however, that many scientists view a massive ocean fertilization program to remove carbon dioxide from the atmosphere as a "last ditch effort" if warming cannot be controlled with reductions in fossil fuel burning and in cutting rain forests.
But Bidigare pointed out, "If one adds iron to the ocean and has large blooms and the remains sink to the ocean floor, you have the potential of reducing oxygen content in the bottom waters, which would have deleterious effects on the fish that live down there."
Also, he said, "If you add iron to the ocean, what if you produce toxic species of algae? Unlike when a farmer goes out and fertilizes a plot of land and adds seeds, he knows what will grow up. When you add it to the ocean, anything can grow up, including toxic species. It is very uncontrolled."
UH scientists examined the amounts and kinds of phytoplankton (microscopic marine plants) and zooplankton (animals that feed on phytoplankton) that bloomed in response to the iron fertilization, Bidigare said. Bidigare said he, oceanography specialist Karen Selph and postdoctoral student Susan Brown were on the Scripps Institution vessels measuring pigments and doing microscopic examination of the cells to evaluate the phytoplankton blooms' increase. Preliminary analyses were done on the ships, with follow-up in their UH-Manoa lab.
The experiment was conducted in January and February 2002 in two square areas, each 9 miles long on a side. They were in different parts of the Southern Ocean to determine the effects of silicid acid concentrations, essential to growth of diatoms, giant types of phytoplankton.
Simulating ice-age conditions, iron concentrations of about 50 parts per trillion were added to the water, representing a 100-fold increase over natural conditions.
"The size of the bloom was spectacular, and you could see a change in the water color," Bidigare said. "It went from blue to green. ... You could really see the difference in the patch and out of the patch."
The massive blooms were visible in satellite images of the area, he said.