Brandenburg, Land of the 3000 toxic lakes!

Toxic microorganisms that cause fish death and poison sea food are proliferating in the Baltic Sea. In the past two years, four people have died from infection by vibrion bacteria. Toxic organisms are also on the rise in lakes around Berlin, and several dogs have died from contamination at Tegel See.

Temperature increases and eutrophication are causing toxic algae and bacteria to bloom in waters worldwide1. These so-called red tides appear without warning and often linger long past expectations – killing fish and contaminating seafood. They also turn bodies of water foul-smelling and scummy and produce species of toxins that are potentially deadly to animals and humans. Furthermore, those toxic microorganisms can also reproduce in freshwater reservoirs; threatening irrigation and drinking water supplies, as is already happening in Australia2.

Recently, a dog died after swimming in Lake Tegel, Berlin; poisoned by Anatoxin-A produced by Tychonema sp., a cyanobacterium algae3. In 2017, at least 12 dogs were poisoned by the Tegel See and several of them died ‘despite intensive veterinary treatment’4. Recently, an elderly woman also died after being contaminated by toxic bacteria of the Vibrium type in the Baltic Sea5. These kinds of bacteria are usually found in tropical waters. Swimming in your local lake or the seas of Europe could soon become a potentially life-threatening activity not just for wildlife and our pets, but also for adults and children.

All together, marine and fresh waters worldwide are at risk. For example, the massive red tide of the non-toxic dinoflagellate Akashiwo sanguinea in the Pacific Northwest (United States) resulted in the largest marine bird mortality event ever documented. In 2009, over 10,000 seabird carcasses washed up on the shores of Washington state – linked to the production of foam that destroyed the waterproof characteristics of the birds’ feathers. In the US, 20 humpback whale deaths have been attributed to that toxic algal proliferation over the past decade. Many more examples can be found1:1.

In addition, chronic exposure to some toxins is a new area of concern. For example, microcystins – produced by certain species of both freshwater and marine toxic algae – have been linked to tumours, liver damage and death in humans (as well as stunted development in fish and zooplankton). Exposure to domoic acid is associated with epilepsy-like seizures in marine mammals, but very little is known about the long-term impacts on humans from this and other algal toxins1:2. Will it ultimately become life-threatening to live near the sea or lakes? While we can’t answer that question right now, we do know one thing for sure. We need to dramatically reduce our impact on aquatic ecosystems to avoid a future where our waters are toxic!


  1. Kudela et al., 2015, Harmful Algal Blooms. A Scientific Summary for Policy Makers, IOC/UNESCO Report. ↩︎ ↩︎ ↩︎

  2. Keeton, 2018, Toxic blue-green algae in irrigation waters: a public health threat to the City of Sydney?, Sydney Environment Institute. ↩︎

  3. 15 May 2019, Hund stirbt nach Bad am Tegeler See: Untersuchungen laufen, Berliner Morgenpost. ↩︎

  4. Fastner et al., 2018, Fatal Neurotoxicosis in Dogs Associated with Tychoplanktic, Anatoxin-a Producing Tychonema sp. in Mesotrophic Lake Tegel, Berlin, Toxins 10:60. ↩︎

  5. Rathke, 9 Aug 2019, Vibrionen in der Ostsee: Erster Todesfall in MV – vier weitere Infektionen, Ostsee Zeitung. ↩︎