A paper in Nature this week contains worrying news for waterways.
Bacterial communities living in estuaries usually protect the sea from pollution by removing the excess nitrogen washed in from farmland. But since the 70's the amount of nitrogen removed has been falling. Now it's reversed and the riverbed bacterial community seems to be adding nitrogen to the water rather than taking it away.
Robinson Fulweiler, from Rhode Island University, has found that a reduction in plankton, which are a source of organic matter "food" for the nitrogen-removing bacteria, has led to them going on hunger strike and being replaced by less fussy bugs that excrete than than remove nitrogen compounds. "The cause may be global warming," says Fulweiler. "Plankton blooms are triggered by sunlight. In warmer weather there are more clouds, which could affect the process. Also, warmer temperatures may encourage more grazing by other organisms that consume the plankton". Either way, if this continues it may have serious implications for the marine ecosystem because excess nitrogen could trigger uncontrolled plant and toxic algal blooms at sea.