The composition of cyanobacterial communities in peri-alpine lakes has become increasingly similar over the past century. Climate warming and a period of eutrophication have favoured in particular potentially toxic species which can adapt rapidly to environmental changes. These are the findings of an Eawag-led study analysing DNA extracted from sediment cores.
Cyanobacteria — also known as blue-green algae — are adaptable organisms which lie at the bottom of the food chain in lakes. Around a century ago, each lake had its own characteristic cyanobacterial assemblage. Now, according to a study by Swiss and French researchers published in Nature Ecology & Evolution, the differences between lakes are becoming less marked — from Lake Constance to Lake Geneva, and from Hallwilersee to Lago Maggiore.
Sediment cores from 10 lakes
In the study, using cores retrieved from 10 peri-alpine lakes, the scientists investigated cyanobacterial DNA from dated sediment layers. Statistical analysis of the data revealed that community composition has become increasingly uniform across all lakes over the past century, even though the number of genetically differentiable “species” has increased in some lakes. Since the 1950s, the proportion of species groups found in few lakes has declined, while the proportion of common ones (found in many lakes) has increased fourfold.