Professor Neil Price PHOTO: OWEN EGAN

The iron connection

BRONWYN CHESTER | Everyone knows how vital iron is to the human body. Without it, our blood cells can't pick up oxygen and without oxygen, well, we suffocate. But it was only recently that iron's equally important role in the health of the oceans was identified, and scientists continue to research the role the metal plays in regulating such important substances as carbon dioxide, the gas responsible for the creation of the greenhouse effect. (CO2, produced in excess as it is by the combustion of fossil fuels, like gasoline, collects in a circle around the earth's atmosphere, trapping and amplifying the planet's heat, hence global warming.) One of those scientists is biology professor Neil Price, whose publication in a recent edition of Nature, the British science journal, further established the link between iron and the oceans -- specifically the relationship between iron and phytoplankton. Phytoplankton are what we call algae, which we see growing on rocks in lakes at the seashore. The organism requires iron to survive and it's long been assumed that the algae sustains itself by absorbing iron that's been dissolved in surrounding water. There is enough iron to be found in waters near coastal areas but the metal is harder to come across in other parts of the ocean. So how do the phytoplankton located in those areas make do? It's a question of some importance because healthy oceans require healthy phytoplankton -- these single-cell organisms are the very foundation stone of the marine food chain. What Price -- and his colleagues Roxane Maranger and David Bird from the Université du Québec à Montréal -- was able to ascertain was that there are phytoplankton capable of eating bacteria. By munching on smaller microbes, these phytoplankton get the iron they need to carry on. In fact, they're more successful at getting enough iron for growth than those which rely solely on iron, dissolved in the surrounding water. Why? The secret is in the ocean's bacteria, for they are expert at using the low levels of dissolved iron and particulate forms and converting the latter into a form that's digestible for mixotrophic (i.e. photosynthesizing and substance-eating) phytoplankton. What's more, Ochromonas, the phytoplankton Price studied in his laboratory, also share the wealth. After assimilating roughly 30% of the iron ingested from the bacteria, the remaining 70% is "peed" out in soluble form, making it available to other phytoplankton. Why does this matter? Because the more iron is used by phytoplankton, the more growth of phytoplankton there is, the more food there is for zooplankton (plankton-eating plankton), which in turn provide food for such small animals as krill, which, in turn, feed larger sea creatures like fish and whales, and so on. Furthermore, the more phytoplankton there is, the more CO2 is absorbed from the atmosphere. What remains to be seen now is what happens to phytoplankton when iron is added to the ocean. (One theory is that "fertilizing" the ocean with iron will reduce atmospheric CO2, thus providing a solution to global warming.) In February, one of Price's four graduate students, PhD candidate Maite Maldonado, will undertake to find out when she and scientists from the United Kingdom, Australia, New Zealand and Canada set sail from Christchurch to deposit 200 kilograms of iron sulphate over a 62-square-kilometre patch of water. Price himself, who has taught at McGill since 1992, has made numerous excursions to the open seas but the demands of running a laboratory and partaking in the care of his two young children restrict his ocean-going excursions.