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Methylmercury bioaccumulates in aquatic food chains and can cross the blood–brain barrier, making this organometallic compound a much more worrisome pollutant than inorganic mercury. Experimental evidence now indicates that mercury methylation by the bacterium Geobacter sulfurreducens can be greatly enhanced in the presence of the amino-acid cysteine.
The recent, dramatic retreat of many outlet glaciers of the Greenland ice sheet has raised concerns over Greenland’s contribution to future sea-level rise. Simulations with a numerical ice-flow model indicate that the recent rates of mass loss in Greenland’s outlet glaciers are transient and should not be extrapolated into the future.
