Dust deposited from the atmosphere into the ocean has always been considered a source of nutrients for marine phytoplankton, but new research shows that the dust may also bring toxic compounds that inhibit growth of some species (Proc. Natl. Acad. Sci. USA, DOI: 10.1073/pnas.0811486106). Aerosol dust carries essential iron, phosphorus, and nitrogen to phytoplankton, tiny marine organisms that are an important part of the global carbon cycle. Adina Paytan of the University of California, Santa Cruz, and colleagues collected atmospheric aerosols from near the Gulf of Aqaba in the northern Red Sea. They added those aerosols to phytoplankton-populated seawater collected from the sea. They also conducted experiments in which they exposed different phytoplankton species to specific metals found in the aerosol dust. Their experiments showed that some aerosol dust slowed down the growth of most species tested. The researchers suggest that the apparent toxicity could stem from high copper concentrations in these specific aerosols. Paytan says models used to predict future climate changes must be refined to include not only aerosols of varying composition but also the ways different marine species respond to them.