What new things did we learn about golden algae at the Conference at IOŚ-PIB?

On the last day of March, the Institute of Environmental Protection-State Research Institute held a scientific conference on the problem of golden algae, titled “The Golden Algae. “Harmful blooms of Prymnesium parvum in freshwaters – consequences and mitigation measures”. The speakers were scientists and experts from both centers in Poland and abroad. The purpose of the meeting was first and foremost to exchange experiences in a wider than just domestic setting.

The speeches were organized into three thematic blocks. The first, more “technical,” involved the presentation of the results of two reports: the final report of the Team for the Development of the country. the situation in the Oder and the Joint Research Center‘s February report. The first session also covered selected aspects of water monitoring in the context of the need to control golden algae blooms. They stressed the need to expand observation to include methods directed at early detection of such threats.

The southern session was devoted to the broad ecology of the species, analyzing the conditions of its occurrence and the factors that promote toxic blooms. The session opened with a lecture by Professor R. Patiño of Texas Tech University, who presented the experience of nearly 40 years (the first recorded bloom was in 1985) of the American fight against this invasive species. It turns out that, in contrast to the situation found in Poland and other European countries, Texas blooms occur mainly in the winter-spring months, and ichthyotoxicity manifests itself outside the summer period, under conditions of moderate and even cool air temperatures (10 – 15°C). The numerous examples cited by the speaker point to a sudden change in conditions as the most likely cause of the bloom. However, there are also known examples of blooms appearing even though conditions were stable. The speakers’ subsequent presentations on the environmental conditions accompanying the algae were consistent with American observations and confirmed the complexity of the problem.

The final afternoon session covered practical issues in observation techniques and methods of controlling golden algae, including a presentation of an experiment currently underway on the Gliwice Canal using lanthanum-enriched bentonite clay. Preliminary results allow us to see this technique as an opportunity to reduce the number of P. parvum.

It’s probably inelegant to be an advocate in one’s own case (she had the pleasure of chairing the meeting), but in my opinion the conference was content-dense and interesting. The exchange of experiences with experts from outside Poland allowed us to expand our knowledge beyond our own experience. Even if it did not bring a clear-cut solution to the question of why the P. parvum bloom occurred in the Oder River in the summer of 2022, it allowed us to share the vast amount of data and knowledge we have acquired over the past months.

It leaves no doubt that the condition for the occurrence of golden algae is the availability of habitat, i.e. waters within a certain range of salinity. However, the issues of the level of nutrient availability, optimal temperature, hydrological conditions or the relationship of toxicity to salinity levels are not so clear-cut in their interpretation and still require research. It is known that nutrient availability is crucial for the occurrence of a bloom – US observations confirm that while the presence of P. parvum was found even in oligotrophic waters, blooms only occurred under eutrophic conditions. Based on analyses of data from the Oder River, it appears that the nitrogen-to-phosphorus ratio may be a promising indicator of bloom risk. With the value of weight ratios of these elements above 23, P. parvum was basically not found in the Oder River. The variability of the species’ toxicity in waters with different hydrological conditions may also prove to be an important research thread. Higher concentrations of prymnesins at lower cell counts were found in standing water bodies associated with the Oder River than in the course of the Oder River or even in canals. Considering the Polish experience with this invasive species, covering a period of only 7 months, expecting categorical conclusions at such an early stage of research seems strongly unjustified.