The pristine state of unpolluted waterways may be their downfall, according to research results published in a paper this week in the journal Geophysical Research Letters.
A species of freshwater algae that lives in streams and rivers, called Didymo for Didymosphenia geminata, is able to colonize and dominate the bottoms of some of the world's cleanest waterways--precisely because they are so clear.
Didymo does so with a little help from its friends--in this case, bacteria--which allow it to make use of nutrients like phosphorus.