Odra

How can the situation on the Oder River be assessed from today's perspective?

Certainly, the recent disaster must be taken as a serious warning. However, it is worth remembering that aquatic ecosystems are relatively flexible to a fairly high degree. Under right conditions, they reproduce themselves at a fairly rapid rate. So if there are no dramatic droughts, the fight against with Prymnesium parvum will prove successful we start to gradually manage discharges into the the rivers to reduce the amount of salt and create conditions for natural habitats, the first effects will be visible after just a few years. Within a decade, it will be possible to speak of an ecosystem not only restored, but also improved. But this is a very optimistic scenario. In the case of the Oder, which is a largely regulated, this is a process that would have to be spread over decades. You have to start somewhere.

At what stage is the work currently underway, what do we know today?

We have done ichthyological reports, which show up to 50%, but locally even up to 80% loss in the Oder fish population. The ecosystem losses are high, especially among molluscs, which are very important for the aquatic environment. Mussels and scads grow very slowly, and they are the ones that filter vast amounts of water. This factor will be missing from the Oder River ecosystems. In addition, mussel habitats serve as breeding grounds for some fish species, such as bitterlings, under protection. Therefore, a small number of molluscs in the ecosystem will slow the reproduction and restoration of fish populations in Oder waters. However, it is too early to make definitive conclusions. We still need to conduct thorough data analyses. The next step will be to work out the mechanisms of what has happened. The most important thing is to lay the basis so that we know what to do to prevent the phenomenon from recurring. Our Institute is working, among other things, on such details that are critical for restoring the Oder River's ecosystems. This is particularly significant, for example, in stocking, which must be executed appropriately. Besides, this year we have to look, for instance, at the spawning results. This is a natural process, accompanied by spring swells in the rivers. If, due to drought, as in 2022, there is no localised flooding, then spawning is limited or non-existent. This also impacts the abundance of individual species.

Meanwhile, the drought persists and all indications are that it will appear for another year in a row...

Well, that's just it. At the moment, and this is January, the flow in the middle Oder River remains at 110 m3 per second, which is below average. At this time of year, water resources should be recovering. Climatic conditions have a considerable impact on river ecosystems. If drought and the accompanying high air temperatures and low water levels persist, we must be prepared that it will not be easy.

What is most important from the point of view of ecosystem restoration?

In restoration work, we must undeniably consider the conditions of the shape of the riverbed. Much work is needed to care for the fish that remain in the Oder River and provide them with good conditions. Significantly, the ecosystems regenerate in different directions so that we don't create what I call 'Disneylands', namely artificial environments where one species, such as carp or bream, is king.

We want to have a natural composition of species in the Oder, one that is characteristic of this river. This is why we have carried out a thorough inventory and ongoing monitoring of the ichthyofauna. So if the right conditions are created, refugia where fish can shelter and habitats, then the restoration process, as I said earlier, occurs rapidly. If constraints arise, such as low water levels in the water level in spring, then the population of young organisms will be lower. From March to July, there is a drift phase, when many larvae in the water move downstream. So the right hydrological conditions are needed so that most of them can survive.

How substantial is water salinity reduction to these processes? What measures should be made in the first instance?

It is imperative to reduce the salinity of the river. However, as scientists, we know that it cannot be reduced to zero overnight. Prevention, i.e. reducing salinity, is essential, but the Oder River already needs to be helped now, first and foremost, by increasing the resilience of the ecosystems. From the ichthyologists' point of view, the key is to create refugia - places where fish can find shelter naturally. If we now take a bird's eye view of the river, it is more like a trough with bends, without oxbow lakes. It is enough to look at the Vistula to see the difference. A plan to create refugia on the Oder River should be in place within the year. A search is underway for areas where something can be done. Then we will have to enter the more difficult phase of optimisation, i.e. the negotiation process. When solutions are introduced, monitoring will be indispensable to see how it has worked and then transfer this experience to other areas. This process should go hand in hand with improving water quality, as there are a lot of industrial plants on the Oder. As I mentioned, a sensible compromise must be found here, reconciling economic and environmental interests.

The Oder is used for various purposes - tourism, business, and recreation. Different expectations are held by anglers, others by entrepreneurs, boaters and flood safety services, where navigability enables icebreakers to work and is crucial for the protection of residents. Is it possible to reconcile the interests of all groups?

There needs to be cooperation between many communities, and this is happening here. There needs to be an agreement between all the groups that use the rivers. Our task as a research institute is to provide evidence of applied science, i.e. factual data and knowledge that will help people from other industries to make the right decisions.

At what stage are we in the Odra case?

As of today, we have a diagnosis and extensive data, but we can talk about information and preliminary reports at this stage. Chemical and ichthyological monitoring is - and should - be continued, but it is only one of the components that improve the state of rivers. We must work in an interdisciplinary way, considering all aspects. There are many of them while researching the river. Our institute focuses on ichthyofauna. The integrated monitoring, which is being developed, requires a broader view that includes studying phytoplankton, chemical parameters and flows. The more information, the easier it will be to get a complete picture.

We are assembling a team of experts and selecting rivers that should be monitored first as part of a comprehensive system. An action plan and habitat restoration programme are already being developed. We have already made models and are analysing data from the hyper-spectral raids we did last autumn. The coming year will be a time of very intensive work.

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December 2022 saw the publication of a report on fish monitoring in Poland prepared by the Stanisław Sakowicz Inland Fisheries Institute in Olsztyn: Assessment of surface water bodies for ichthyofauna for 2022. Specialists from the institute also participated in the work of the Team for the Situation Arising on the Oder River, appointed by the Minister of Climate and Environment. Teams of scientists are still working to clarify the mechanism that contributed to the massive fish die-offs in the Oder River. Several ministries whose competences include water and fisheries management, dozens of scientists from Poland and abroad and top-class experts related to the aquatic environment have been involved. Meetings of the German-Polish expert group on the Oder are also taking place. Ongoing work is underway to develop a permanent monitoring and protection system for water ecosystems throughout Poland. As many as PLN 250 million is earmarked for this purpose. The water quality in the Oder is continuously monitored by the Central Research Laboratory of the Chief Inspectorate of Environmental Protection, and samples are taken twice a week at 20 measurement points. Tests are also carried out for Prymnesium parvum, so-called 'golden algae,' and the ichthyotoxins they produce.