Dusty seas capture carbon

University of Sydney, Science Alert 7 Oct 09;

Scientists from the University's Ocean Technology Group at the Faculty of Engineering have suggested that the recent dust storms may have dramatically boosted carbon capture in Sydney Harbour and the Tasman Sea, providing an unexpected benefit to the environment.

"Nutrient rich top soil, like the three million tonnes dumped on Sydney at the end of September, contains up to one per cent as nutrients such as nitrogen and phosphates", says Professor Ian Jones, Head of the Ocean Technology Group. "After the dust is deposited on the sea surface, the nutrients dissolve in the sunlit region of the ocean and are used by the phytoplankton to multiply," he says.

Measurements taken following the dust storm at the Sydney Institute of Marine Science (SIMS) have confirmed a tripling of the phytoplankton in Sydney Harbour at Chowder Bay and in samples taken 10km offshore.

"We estimate that as a consequence of this the extra phytoplankton in the Tasman Sea will be capable of capturing eight million tonnes of carbon dioxide, about the equivalent of a year's CO2 emissions from a coal-fired one gigawatt power station, or a month's worth of emissions for the Munmorah Power Station on the Central Coast," says Professor Jones.

Professor Jones says that this carbon will slowly be exported to the deep ocean in the form of an additional two million tonnes of phytoplankton. As the phytoplankton moves through the food chain this will in turn grow extra fish, thus benefiting the fishing industry.

The recent dust storm provides strong evidence in support of the ocean nourishment principles that Professor Jones has been investigating for more than 15 years.

Previous studies led by Professor Jones have established that adding fertilizer nutrients to the sea promotes the growth of naturally occurring phytoplankton near the surface of the ocean. These investigations have shown that the quantity of phytoplankton is only limited by the shortage of nitrogen in the ocean.

For some time now the Ocean Technology Group has been planning an experiment that replicates the dust deposition in the Tasman Sea. Rob Wheen, Associate Professor in Civil Engineering says: "Our intention is to inject 2.5 tonnes of nitrogen (in the form of urea) into the upper ocean in order to increase the amount of phytoplankton in a controlled patch away from shore near the edge of the continental shelf.

"Satellite remote sensing will be used to monitor the patch of enriched water. This sensing can detect the chlorophyll in phytoplankton. We want to demonstrate safe and practical ways of broadcasting the nutrients. We see this as a precursor to larger scientific experiments in the ocean," he says.