Tropical blue-green algae conquer northern Germany

Invasion could change planktic communities

One of the three tropical cyanobacteria species found in lakes in northeastern Germany: Anabaena bergii. © IGB
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Climate change is already making itself felt in the local waters: Berlin scientists have discovered several tropical blue-green species, including Cylindrospermopsis raciborskii, in the lakes of northern Germany. However, the researchers discovered a surprise when they were looking for the typical poison of this blue-green algae: they were able to detect the toxin cylindrospermopsin (CYN) in local waters, but it does not come from the immigrant species, but from native blue-green algae.

Cyanobacteria or "blue-green algae" are widespread and, especially in summer, a problem with bathing lakes. Now, a team of scientists led by Claudia Wiedner from the Berlin Leibniz Institute of Freshwater Ecology and Inland Fisheries (IGB) has shown that the tropical cyanobacterium Cylindrospermopsis raciborskii has spread to the lakes of northern Germany.

The scientists see the cause of climate change as the cause. The researchers found that the tropical species in the waters of the Berlin region is more common than previously thought and that there are also other tropical cyanobacteria. Wiedner says, "We expect widespread changes in the planktic communities of our waters through this invasion of tropical species."

Poison producers identified

The researchers included experts from the ITUC, the BTU Cottbus and the Federal Environmental Agency. The team also found the typical toxin cylindrospermopsin (CYN) in local waters, but at first it was not clear if it was produced by the immigrant species. As part of a three-year project, the scientists came across the poison producers. Thus, the toxin surprisingly does not come from the tropical species but from two native "common species" (Aphanizomenon flos-aquae and A. gracile).

However, we have not been able to fully elucidate the circumstances surrounding the toxin occurrence, "says Wiedner. Important for the assessment of the hazard potential is the fact that the toxin is not bound in the cells, but freely dissolved in the water occurs. "Our research points to other, previously unidentified producers, " says the researcher. display

Advice on the monitoring of bathing waters

In addition, it should be noted that there are different proportions of genotypes within a species that are capable of producing toxins. Put simply, some organisms of one species can produce the poison, others of the same kind can not.

The ITUC scientist says the results "provide a good basis for developing concrete recommendations for monitoring bathing water and drinking water resources." Now it is important to clarify the factors that control the spread of toxin and the level of poison production.

The results of the research project and an outlook on the future development of cyanobacteria and toxins in Berlin will be presented in an international symposium organized by the Leibniz Institute of Freshwater Ecology and Inland Fisheries on April 19, 2007 in Berlin presented to our waters.

(idw - Forschungsverbund Berlin, 05.04.2007 - DLO)