Dec. 22, 2003 Biologists from the Royal Netherlands Institute for Sea Research have demonstrated that desert dust promotes the growth of algae. Scientists had already assumed that the iron in desert dust stimulated algal growth, but this has now been demonstrated for the first time. The researchers have published their findings in the December issue of the Journal of Phycology.
The biologists cultured two species of diatoms in seawater originating from the iron-depleted Southern Ocean, the sea around the South Pole. The algae were supplied with dust from a desert in Mauritania and a desert in Namibia. The growth of algae which received a lot of dust was compared with that of algae which received little or no dust.
Algae that received desert dust grew considerably better than algae which did not. The researchers also discovered that algae grew less well on desert dust from Mauritania than desert dust from Namibia.
As well as establishing how much iron the dust contained, the researchers also discovered that the algae could only utilise a limited part of the dissolved iron. This was established by culturing the algae in seawater without dust, but with different concentrations of dissolved iron. The researchers could then compare the growth of the algae that received a known quantity of iron with that of the algae which grew on dust.
The researchers will use the laboratory results to predict how algae in the ocean respond to desert dust. The data obtained from these predictions will contribute to knowledge about the further development of the greenhouse effect, because algae absorb the greenhouse gas carbon dioxide and in so doing slow down the warming up of the Earth.
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