Algae species in Swiss lakes are homogenising, researchers find

The big blue (and green): Lake Zurich in summer Keystone

Swiss and French scientists report that variations of cyanobacterial communities, or algae, found in the lakes of Switzerland have become increasingly uniform. This could allow more toxic species to thrive.

The research was published Monday in the Nature Ecology & EvolutionExternal link journal and provides an overview of the evolution of cyanobacteria (blue-green algae-like organisms) in ten peri-Alpine lakes over the past century.

Analysing cyanobacterial DNA from the lakes’ sediment layers, the researchers report that since the 1950s, although the total number of differentiable species has increased, the larger trend is towards a fourfold uniformization of algae types in Swiss waters.

This could, according to lead author Marie-Eve Monchamp, bring about an increase in species that “need less light to survive – and that includes many toxic species”.

An increase in such species, such as the red-bloomed Burgundy blood alga (already dominant in Lake Zurich), could cause problems down the line for the use of lake water for drinking.

The causes of the homogenisation? Climate change, the researchers say, which then brings about the eutrophication phenomenon whereby new organisms thrive where they were usually absent.

Higher temperatures, in effect, lead to longer periods of “stable stratification”, whereby for example warmer and lighter water layers do not sink to mix with the rest of the lake liquid. This favours the emergence of dominant, homogenous, and potentially toxic cyanobacteria.

swissinfo.ch and agencies/dos