Jun 2, 2011 13:32 GMT  ·  By
Unpolluted river in Chilean Patagonia, among many such rivers invaded by Didymo
   Unpolluted river in Chilean Patagonia, among many such rivers invaded by Didymo

Scientists have recently determined that some of the world's most pristine and clean waterways may be at an elevated risk of suffering from the ill-effects of algal invasions. The reason for that is the fact that the waters are so clean, experts now indicate in a new study.

In other words, the very fact that these rivers are so clean is what allows algae and their bacterial minions to colonize the waters, and set up shop in these delicate ecosystems. The type of algae that carry out these invasions cannot multiply so abundantly in polluted water.

The species, called Didymosphenia geminata (or Didymo for short) lives predominately in streams and rivers, and has a symbiotic relationship with bacteria that enable it to feed on waterborne nutrients such as phosphorus.

In a paper published in this week's issue of the esteemed scientific journal Geophysical Research Letters, experts say that Didymo blooms are also called rock snot, due to their weird, uncommon looks.

More recently, they are being found in oligotrophic (low-nutrient) streams and rivers, on whose bottoms they form thick mats, explains P.V. Sundareshwar. The expert is a scientist with the South Dakota School of Mines and Technology.

He is also the lead author of the new journal entry. “In recent decades, human activities have led to many uncommon environmental phenomena. Now we have Didymo,” the investigator explains.

The alga “presents a threat to the ecosystem and economic health of these watercourses,” he adds. The organism can affect fisheries, and reduce the available levels of oxygen in the water significantly.

“This study solves the puzzle of how Didymo can produce such large blooms in low-nutrient rivers and streams,” explains Tim Kratz, a program director in the US National Science Foundation's (NSF) Division of Environmental Biology.

“It has uncovered the fascinating mechanism by which Didymo ‘scrubs' phosphorus from a stream or river, then creates a micro-environment that allows microbes to make this nutrient available for Didymo's growth,” the official adds.

The new work, which was supported by the DEB, included experts from the South Dakota State University and the US Geological Survey (USGS), in Boulder, Colorado. The study was carried out on an unpolluted mountain stream in western South Dakota, called Rapid Creek.

The investigation “has the potential to lead to discoveries that may stem this organism's prolific growth in rivers around the world. This is how science is supposed to work--research conducted at one small creek in South Dakota can be translated to places across the globe,” Sundareshwar concludes.