Tiny single celled plants called phytoplankton support the food chain of the world’s oceans. By locking up carbon dioxide during photosynthesis, they are also recognised as a vital component buffering the earth’s atmosphere from burning fossil fuels.

The numbers of phytoplankton are limited by the availability of sunlight and nutrients. Above 50°N in the Atlantic it had been assumed that winter turnover of water masses replenished the nutrient supply, and that the limiting factor for phytoplankton growth was a combination of grazing, and lack of silicates (a vital micro-nutrient for diatoms, pictured). Recently, however, experimental evidence, gathered by scientists at the University of Southampton, indicates that it is lack of iron, another important micro-nutrient, that is limiting the growth of phytoplankton.

Experiments elsewhere, aimed at increasing the amounts of carbon dioxide removed from the atmosphere, have tried to boost phytoplankton production by artificially adding more iron to water bodies.

From Science Daily