• Dirk

A toxic cocktail in mountain lakes

Updated: Apr 28

Mountains are pristine, remote, with fresh, clean air, an intact biodiversity, and a perfectly well-preserved environment. WRONG!

We are sorry to bring bad news, but our work clearly shows that there is a huge amount of different chemical molecules found in mountain lakes. Of the 470+ we looked for in our samples, we found 141. 141!!! That is a massive amount of different molecules for a presumably pristine and remote area, producing a wild chemical cocktail. Each molecule has a different toxicity, and the toxicity depends also on the sensitivity of the organism… this is so complex that there a several database out there to archive this massive amount of information (e.g. NORMAN database).

In our recent study entitled “Complex chemical cocktail, containing insecticides diazinon and permethrin, drives acute toxicity to crustaceans in mountain lakes”, we show that there is a huge range of herbicides in mountain lakes. However, in most cases the concentrations remain low and overall, chronic toxicity has not been reached in our study lakes. Despite these low concentrations, we see a link between the number of rotifer species and the algal toxicity of these molecules. The higher the toxicity, the less different species of these tiny species we find. This is for herbicides!

It is a completely different story for insecticides and other organic pollutants with a known toxicity for tiny crustaceans. The summed toxicity of these compounds add up to a CHRONIC toxicity and in some cases and times of our study they even are above ACUTE toxicity for crustaceans. Wow! Remote mountain lakes, but polluted and heavily polluted actually. We are talking about small concentrations, sometimes only nanograms (= 0.000000001 g). However, these molecules are so toxic that even in such small concentrations they impact on or kill insects, or more largely seen arthropods. Now, in our samples two molecules play a particular role: Diazinon and permethrin.

These are used as insecticides and insect repellents and they drive the toxicity in our lakes. Some of you put them on your dogs to treat them against fleas, farmers put them on livestock for protecting them from sucking insects, which could transfer diseases. The concentration of these two molecules in our lakes are surprisingly high and coincide with absence or smaller numbers of crustacean individuals in the zooplankton of our lakes. The concentration of these two molecules hence drives a change in the freshwater plankton community, disturbing the functioning of the ecosystem. More importantly, you might have thought mountain lake water is safe to drink.

Think twice now… humans have achieved a pollution level in mountain lakes high enough to kill crustaceans, and such a diverse and complex cocktail as observed in our study can have unpredictable health impacts on any other organism, including humans.

Rotifer (Lecane)

Crustacean (Chydorus)

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