Tons of dead fish, mass extinction of all living organisms in the Oder, in other words, a great ecological disaster. Theories to explain this phenomenon have arisen and continue to arise. We know for sure that one of the factors wreaking havoc in the Oder is algae - the so-called golden algae. How and why did they get there? Can we do anything to avoid further blooms and an ecological crisis in the future? We ask prof. dr hab. Hanna Mazur-Marzec, Head of the Department of Marine Biotechnology at the WOiG UG, who in recent days confirmed the presence of Prymnesium parvum in the river.

- You have completed research on samples from the Oder River, confirming the presence of so-called 'golden algae' in its waters and, consequently, strong toxic compounds - ichthyotoxins. Please tell us something about this group of algae. Do we know how they found their way into the Oder River and why they caused such havoc?

- Prof. dr hab. Hanna Mazur-Marzec: - 'Golden algae' is the common name for a haptophyte, microalgae of the species Prymnesium parvum. It is a known producer of toxic compounds, including ichthyotoxins. Its appearance in such quantities, as has occurred in the Oder, always results in high mortality of fish and mussels. Its origin in the Oder will probably be the subject of numerous studies. I do not think that this question can be answered today.

- You conducted your research in the laboratory of the Department of Marine Biotechnology at the University of Gdańsk - it is supposedly one of the few places adapted for this type of research.

- I make no secret of the fact that undertaking this task, at the request of the Institute of Inland Fisheries in Olsztyn, was a big challenge for us. Mainly due to the lack of a standard which would allow us to optimise and validate the method and be a kind of reference in analyses using mass spectrometry. Besides, when we undertook this task, we did not know what toxins might be present in the samples and what standards we actually needed. For these reasons, I suggested that the selected samples be additionally analysed by a laboratory that has experience in the analysis of toxins produced by 'golden algae'. For this purpose, the samples were sent to Vienna. From the first data, I know that our results are in agreement. The choice of our Department as the analysis contractor was probably determined by the fact that we specialise in the study of toxins produced by microalgae and cyanobacteria (blue-green algae).

- Have you been able to identify the triggers of golden algae blooms and their toxicity?

- The task I undertook with my doctoral student, Robert Konkel, was precisely to analyse the material for the presence of toxins. We were able to detect compounds from the prymnesin group, three class B prymnesins to be exact. I do not exclude other toxins either, but clarification of this issue requires longer research. Prymnesins are precisely the group of toxins that cause fish deaths on a large scale. The cases described, e.g. in Texas, indicate a huge loss of natural resources in the affected waters, but also serious socio-economic effects, especially in the case of aquaculture. The primary concern, however, is the factors that caused the Prymnesium parvum to bloom. Increased salinity is very often pointed to. It may also be a combination of several factors. Finding out the root cause of this disaster is a task for hydrobiological scientists and water monitoring institutions.

- Can we somehow prevent further environmental disasters? Or will climate change, which has been so noticeable in recent years, contribute to such events and there is little we can do?

- The link between the mass emergence of toxic microalgae and climate change is often highlighted. However, such occurrences were already recorded hundreds or even thousands of years ago. Many factors (not just climate) contribute to the spread of this phenomenon. As I am active in an international group working on this problem, I am able to read the reports of researchers from different countries and continents every year. The scale of this phenomenon is large. Research facilitating the prediction and control of toxic blooms is largely funded by companies, including aquaculture owners. 

Concerning our reality: this disaster may not be such a disaster, after all, if we learn the right lessons from it, learn how to better organise environmental monitoring, and learn how to cooperate across a wide range of officials and experts responsible for the environment.

- The contaminated water is slowly approaching the estuary, perhaps it is already there. Can the toxins discovered so far harm the Baltic Sea environment in any way? 

- I am not sure if the toxins are still there. They are not permanent compounds. In addition, in a river, as in the sea, they will be diluted quickly. However, if there are reports of the presence of Prymnesium parvum in the estuary, then toxins can also be expected. A secondary cause of water contamination is decomposing fish and the accompanying bacterial growth.

- Since when have you been analysing water samples from the Oder River? What prompted you to begin this research? 

- We received the first samples last Friday (19.08). So far we have managed to analyse around 150 samples. We have been working non-stop since Saturday. We are waiting for more to arrive. The extraction procedure is quite long and multi-step. To be honest, although I was very curious about the cause of the disaster, I was reluctant to undertake the analyses. Because of the controversy that this catastrophe aroused, I decided that this was a task for a laboratory that is accredited in this area. Although I don't know if such a one exists in Poland, because so far it has not been needed. Therefore, although we already had results on Saturday indicating the cause of the fish poisoning, I waited until Monday to announce them. On Monday morning, with the help of dr Ewa Wieczerzak from the Department of Chemistry, analyses were carried out using a different type of mass spectrometer (MALDI-TOF), which also confirmed the results.

- More than 100 tonnes of dead fish have already been fished out of the river. How long will it take to rebuild this ecosystem? What will be the long-term effects of this disaster? 

- This is rather a question for ecologists. I can only say from the work I have seen that fish, especially the more 'mobile' ones, recover more quickly in the environment. Unfortunately, bivalves often die irretrievably. This is probably due to the specific nature of these organisms, non-selective 'filterers' of water. We have also been able to detect toxins in bivalves.

- Thank you for the interview.