US mountain lakes turn green due to climate change

PARIS: Researchers at Colorado State University, on Tuesday, July 7, reported that due to global warming, the clear mountain lakes in the western United States are turning green as a result of increase in algae blooms without historical precedent. They found that concentration of algae has more than doubled in two remote mountain lakes in the past 70 years.

Their results, published in the British Royal Society Journal Proceedings B, highlight the potentially harmful effects of climate change on pristine and remote ecosystems.

Dr. Isabella Oleksy, lead researcher, Colorado State University, in conversation with Agence France-Presse (AFP), said even in relatively remote lakes located in protected areas, the evidence of disturbances in earth system caused by human involvement are visible. She added that the rapid acceleration and dominance of green algae, which were until now in low abundance in these lakes, is because of rapid warming of high elevation environments. 

The team of scientists, led by Dr Oleksy, studied algae concentrations in lakes in a mountain range about 100km from Denver, using a tool called ‘gravity corer’ to collect sediment cores without damaging the lakebed. Based on observations dating back to the 1950s, they found ‘dramatic algal abundance shifts’ in the form of green algal blooms called chlorophytes that grow in warmer temperatures. 

Dr. Olesky added that the high level of algae came as an ecological surprise which would typically be found in highly polluted areas, such as those prone to agricultural run-off, and not in unsullied mountain environments. But these changes were documented in two lakes in Colorado, so it is likely that this is not an isolated phenomenon.

The researchers admitted that the findings are not a conclusive evidence but point to climate change as driving excess accumulation of nutrients such as phosphorus and nitrogen, causing algal blooms.