Biodiversity improves water quality in streams through a division of labor

Science Centric: Biologically diverse streams are better at cleaning up pollutants than less rich waterways, and Bradley Cardinale, an assistant professor at the U-M School of Natural Resources and Environment, says he has uncovered the long-sought mechanism that explains why this is so. Cardinale reports his findings in the 7 April edition of the journal Nature.

He used 150 miniature model streams, which use recirculating water in flumes to mimic the variety of flow conditions found in natural streams. He grew between one and eight species of algae in each of the mini-streams, then measured each algae community's ability to soak up nitrate, a nitrogen compound that is a nutrient pollutant of global concern. He found that nitrate uptake increased linearly with species richness. On average, the eight-species mix removed nitrate 4.5 times faster than a single species of algae grown alone.

'The primary implication of this paper is that naturally diverse habitats are pretty good at cleaning up the pollutants we dump into the environment, and loss of biodiversity through species extinctions could be compromising the ability of the planet to clean up after us,' said Cardinale.

Why are more diverse streams better pollutant filters? Niche partitioning, Cardinale said. In the stream experiments, each algae species was best adapted to a particular habitat in the stream and gravitated to that location - its unique ecological niche. As more algae species were added, more of the available habitats were used, and the stream became a bigger, more absorbent sponge for nitrate uptake and storage…

A stream in Kolomenskoe, shot by Nevermind2