A biologist told how well-fed trout can harm a pond

– Olga Nikolaevna, recently the first scientific and practical conference of the BRICS countries ended in Petrozavodsk, at which many issues related to the environmental state of our countries were discussed. One of the topics of discussion was the problem of our largest northern freshwater bodies – Lakes Onega and Ladoga, the shores of which are located in Karelia, Leningrad and Vologda regions. Tell us how these two water areas “feel”?

– Our republic monitors the situation not only of large, but also of small lakes in Karelia – in total there are more than 60 thousand of them. But the most important, of course, are Lakes Onega and Lake Ladoga, the main sources of water supply for Karelia, the Leningrad region and St. Petersburg. As for Onega, the situation here is generally assessed as normal – the water in the lake is quite clean, especially in the central part of the lake, with the exception of certain coastal areas where wastewater from industrial enterprises and populated areas ends up. As for the capital of Karelia, Petrozavodsk, there are treatment facilities for waste water from housing and communal services. But this cannot be said about a number of other cities, for which, alas, there is “no money” yet.

– If Onega is almost entirely under your control, Ladoga from the south washes the shores of the Leningrad region. What enterprises, in your opinion, need an eye there?

– On the shores of Lake Ladoga there are a number of agro-industrial enterprises, pulp and paper mills, the discharges of which, after treatment, still flow into the lake water. In general, according to our experts, the southern, “Leningrad” part of Ladoga is more polluted than the “Karelian”, northern part. Regarding Lake Onega, its southern part is also causing concern, where there is no hint of treatment facilities. This is our common headache.

– Do you have a vision of how to solve the problem? After all, millions of people need clean water from the northern lake as a source of water supply.

– There are technologies, the authorities also have understanding. At one time we raised the issue of creating a federal law on the protection of Lakes Ladoga and Onega, we talked a lot about it, but it never appeared. Today we hope that the program for the massive construction of treatment facilities will be included in the Ecology national project.

Excess nutrition is harmful even to the lake

– By the way, the question is also relevant in connection with fish production, because almost all of Russia eats Karelian fish. To be more precise, the share of Karelian trout is about 70 percent of all commercial trout in Russia,” continues Olga Bakhmet. – And often the issue of potential pollution of water bodies is related to fish farming.

– How exactly do producers pollute lakes?

– Trout cages cannot be placed in shallow lakes that are unsuitable for such activities, which very quickly become polluted by the waste of the fish itself and excess feed. I would highlight food as a separate item, since it is necessary to accurately calculate their dosage: uneaten food settles to the bottom and becomes a place for the development of pathogenic microorganisms and flowering of the lake. Ultimately, a small lake can simply be lost due to the so-called eutrophication (from the ancient Greek εὐτροφία – good nutrition).

– That is, the lake also “must monitor” its nutrition?

– It turns out that this is so – the oversaturation of water bodies with biogenic elements does not benefit it, and as a result, the business owners themselves may suffer, whose fish will get sick and die in the blooming water. We discuss these issues with trout fishermen, they hear us and have begun to consult with us, scientists, more often to determine the condition of the lakes.

– Are there “instructions” for the size of lakes in which trout can be raised?

– Certainly. 10 years ago, we prepared a list of lakes suitable for trout farming for the Ministry of Agriculture. These lakes are now mainly home to trout farms. But even in those areas that are “favorable” for growing fish, it is necessary to continue to monitor the situation in order to notice in time the negative consequences of industrial fish production. One of the ways to reduce the nutrient load on water bodies from growing fish can be the installation of a closed water supply, when the fish are kept in closed pools with a biological water purification system.

– Is it possible to breed trout in the White Sea, which is also connected to Karelia?

– It would be good to grow trout on the White Sea, some of the pollutants there could be carried into the sea as a result of tidal processes, their concentration would decrease near fish farms, and such fish could be even tastier than lake fish, but… In Unlike the Norwegians, who raise their salmon in seawater with a warm current, the White Sea is covered with ice in winter, the temperature of the sea water decreases, which leads to freezing of the gills of the farmed fish and its death. By the way, there is a unique example of how one of our farmers found a place in the Chupinsky Bay area where he grows fish in the sea in the summer, and in the winter he transfers the cages to a nearby freshwater lake. Also on the White Sea, closed water supply installations, which we discussed earlier, can be used.

“Plastic” lakes

“Recently, the waters of various reservoirs have begun to be examined for microplastic content. There are bodies of water where its concentration is simply off the charts. Does the plastic come from packaging?

– Not only. We recently began taking measurements of plastic in our lakes and came to the conclusion that its microparticles enter the water in large quantities in the same place as the main household discharges. For example, it is known that there is a lot of it in detergents, washing powders, and all household chemicals.

– Tell us how you cooperate in the field of ecology with colleagues from BRICS?

– We have great hopes for cooperation with China, which is very interested in our technologies for studying aquatic ecosystems, including their hydrophysical and hydrobiological regimes.

– So China, which is a major supplier of fish products around the world, is not an advanced country in terms of ecology?

– For many years, China has relied on the industrial use of natural resources in the sea, rivers, and lakes, paying less attention to the consequences. Now, apparently, the situation is changing. We are planning a joint symposium in November to discuss our future cooperation.

– Are there any interesting joint developments with other countries?

– Brazil has long been studying toxicological pollution of the sea coast and how certain pollutants affect aquatic organisms. Not long ago, they invited members of our research center to the University of Sao Paulo, who developed their own method for determining how small doses of pollutants can affect a living organism. They investigated the relationship between the slightest concentrations of chemicals and the cardiac system of aquatic organisms. It turns out that she reacts very quickly to pollution, so to speak, their hearts begin to beat differently. In Brazil, our collaborators proposed existing developments and are conducting joint research into the cardiovascular activity of mussels and oysters. In addition to everything, employees of the Karelian Scientific Center give lectures at the Faculty of Biology of the Brazilian University.

– Can the data obtained on oysters be extrapolated to humans?

– Certainly. We may not notice it right away, but our body, of course, reacts to the effects of various toxicants.

Concluding the water topic, Olga Nikolevna noted that, despite the problems existing in some places along the coast of Lakes Ladoga and Onega, residents of the republic can still safely drink water from reservoirs. Karelian scientists constantly closely monitor the situation with large and small lakes, monitor the slightest deterioration in the condition of reservoirs, and work in constant collaboration with trout farms. In general, scientists make sure that the water in our priceless lakes is clean. It is also important that the money needed to further maintain the cleanliness of the northern lakes is found.