The research aimed to understand the role of Prymnesium parvum in its broader impact on the environment and human health. Scientists hypothesized that the toxins produced by these algae, called prymnesins, would potentially interact with organic micropollutants that are also found to be present in the water samples collected during the fish kill event and could potentially pose additional risk to nontarget organisms and human water use. "The aim of the study was to find out which micropollutants are in the River Oder, how they affect aquatic organisms in the river and what threat the cocktail of algal toxins and micropollutants could pose to humans," says Prof Dr Beate Escher, lead author and environmental toxicologist at the UFZ.
The international research team used a multifaceted scientific approach on what was an opportunistic sampling of the fish kill event. Water sample analysis measured the levels of prymnesins and other pollutants in water samples from the Oder River. Toxicity testing was used to evaluate the toxic effects of the algae on traditional aquatic species, including algae, daphnids, fish embryos, and human neuronal cell lines, whilst a mixture model was performed for aquatic toxicity and in vitro neurotoxicity.Finally, researchers calculated risk levels for aquatic life, finding that the toxins significantly exceeded safe thresholds.
The resulting key findings revealed high levels of prymnesins in the Oder River during the fish kill event. This evidence strongly suggests that these toxins were the main cause of fish deaths, more so than other pollutants found in the water. The research demonstrated that micropollutants detected during the fish kill event are aquatic organisms, posing a serious threat to the health of aquatic ecosystems. The study also raised concerns about the possible health risks prymnesins could pose to humans as high in vitro neurotoxicity. Lastly, the chemical cocktail of hundreds of organic micropollutants acted together with prymnesins to cause neurotoxicity in vitro.
Professor Luisa Orsini from the University of Birmingham says the warmer temperatures and extreme weather events being experienced globally caused by climate change makes such blooms an even greater risk to inland and marine waters and the human population. She said: “The findings of this study highlight the environmental dangers posed by blooms of Prymnesium parvum. which can lead to massive fish kills and disrupt the health of aquatic ecosystems. Toxic algal blooms have become a seasonal reality for many countries, including the UK and USA, impacting drinking water supplies and bathing waters."
Dr Xiaojing Li, also from the University of Birmingham, stressed the key role that sentinel species, such as daphnids (commonly known as waterfleas), can play in predicting the risk of pollutants to humans and the environment. She said: “Daphnia is commonly used in environmental studies to help scientists quickly identify harmful chemicals in water that can affect other aquatic life. As such it acts like an early warning system for water pollution.”
The study emphasizes the need for more research on the effects of prymnesins on human health, particularly regarding the safety of drinking water and recreational water use. The research calls for improved monitoring and management strategies to reduce the impact of harmful algal blooms, safeguard aquatic life, and ensure public safety.
