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- Microplastics in the networks: Lake Baikal is threatened by an environmental disaster
Microplastics in the networks: Lake Baikal is threatened by an environmental disaster
The water of Lake Baikal is gradually being filled with microplastics, small polymer waste that enters it from small Russian rivers and the waters of the Selenga River from Mongolia, untreated industrial wastewater and household waste from natural landfills. Sunken polymer fishing nets have become another major source of pollution. It is impossible to completely clean Lake Baikal of microplastics, but cleaning nets from its bottom, as Izvestia found out, can help eliminate toxic sources of pollution.
The first chapter
A teenage girl struggles to put on a wetsuit, still wet from yesterday's dive to the bottom of Lake Baikal. Here, at Cape Tolstoy, half an hour's walk from Listvyanka on a small boat, the water and air temperature are only ten degrees. An unprepared person will get their teeth clenched from diving into this water, but not hers. This is not the first time she and her fellow divers have descended into the lake with an important mission - to find and raise polymer fishing nets from the bottom, a serious environmental threat to the country's main lake.
Fishing nets are a source of microplastics that kill aquatic ecosystems. It pollutes water by entering in the form of small particles through surface runoff. This is shown by the results of studies demonstrating the high content of microplastics in the coastal areas of tourist areas.
— Plastic thrown on the surface is the first direct threat. Modern clothing made of synthetic materials creates a large volume of fibers that enter Baikal together with wastewater. These types of microplastics are very well separated in material studies. Polymer fishing nets also make a negative contribution, because they often remain at the bottom of the lake. Collapsing, they directly fall into the water column. Over the past 5 years, there has been a one—and—a-half-fold increase in the content of microplastics in Lake Baikal, which is a real problem that needs to be addressed today," Alexander Kononov, senior researcher at the Institute of the Earth's Crust of the Siberian Branch of the Russian Academy of Sciences, Candidate of Geological and Mineralogical Sciences, tells Izvestia.
In addition to the bottom, divers explore the capes, where lost nets often wash up. Here they cling to protruding parts of the coastline, rocky underwater ledges and numerous sunken trees. They are also found on the steep western shore, where nets also accumulate.
The nets are being taken out by divers led by Mikhail Sisenkov.
— In this three-week expedition, we examined about 35 km of the lake bottom in the area of the Kruglobaikal railway and cleaned about 100 km of the coast, from Sandy Bay to Kaltuk. As a result, hundreds of kilometers of polymer networks were discovered," he explains.
Sunken nets drift away with the current for many kilometers from the primary location and often become food for fish. Then such a fish gets on the table. To prevent this from happening, it is important to collect sunken nets as quickly as possible, but this is a task for the trained.
Today, a group of divers is exploring the bottom at Cape Tolstoy. They were lucky with the weather: the morning clouds had cleared, and the sun was gliding across the surface. Mikhail and his colleagues in their gear glide across the water surface on their boots. It's about 20 meters from the shore, not far at first glance, but the depth is great: the bottom is steep and rocky. Here the group dives into the water and goes to explore the bottom.
Find and unhook
Muddy water and frequent storms on Lake Baikal often interfere with searching for nets: if the excitement is stronger than four points, events are canceled because nothing can be seen.
The most transparent water in Lake Baikal is in June. Then the lake warms up with sunlight and flowering begins, at this time little can be seen near the surface, but at a depth of 12-15 m, visibility improves. And at a depth of 20-30 m, you can already see all the foreign objects. We were lucky with the weather this year: in July, the water was no murkier than in June.
The process of collecting nets is multi-stage. First, divers find a net at the bottom, then attach it to a special buoy, which is inflated and released. Rising to the surface, he pulls out a net. But first, divers detach it from the rocky bottom, driftwood, stuck fish and sponge plants with long stems. This painstaking work can take two or three hours and is worth a lot of effort, because it often occurs at a depth of 40 meters at a temperature of +4 C.
No one can say for sure how long the process will take, it all depends on the length of the network and the complexity of the bottom.
— The network can go on forever. We picked up one of them, 200 meters long, at a depth of 200-300 m, and then we took it to the deck manually for about an hour on the ship. Several anchors had been lifted, and she was clinging to something at the bottom. The five of us worked, we barely got out. Raising any network is an unpredictable process," says Sisenkov.
Very often, divers don't even know from what depths the net is being pulled. Sometimes they catch it at a relatively shallow depth of 30-40 meters, and as a result, when they inspect it on the ship, it becomes clear that it lay at a depth of 70-80 m. Such networks seem endless.
The vast majority of nets are made in China, they are polymer, thin and soft, they tear quickly — unlike domestic ones, woven from silk threads, which are much less common here.
The Baikal epic at the time of study
At the same time, any network decomposes in water for several decades and during this time can harm the ecosystem. A group of scientists evaluates the parameters of water pollution as part of annual monitoring.
— Baikal as a water body is unique, the water has an ultra-fresh composition with a low content of macro- and micro components. There are many endemic species that affect the composition of the water and ensure its purity and safety," says scientist Alexander Kononov.
Baikal is fed by many rivers, both small mountain and large deep Selenga. The lake has a complex circulation system, thanks to which the water is saturated with oxygen and maintains a temperature regime.
Selenga River Delta
How can I determine the age of the network? If she doesn't tear when they take her out, it means she's under five years old. But if it breaks, it means 10-15 years. It is such networks that break down into microplastics and pollute the lake. Divers often lift not an entire net from the water, but many fragments, which are collected in large 50-liter bags. Usually, two or three such bags are taken out after each dive.
Scientists say that microplastics accumulate most of all in the central part of the lake, rather than on the shore, due to currents.
— This so-called microplastic spot is associated with the circulation of water in the lake: there are no such pronounced zones of circular currents in it as in the oceans, but there is still a tendency for circulation to form, including in the Selenga confluence zone, to which the authors attribute the main pollution. To be honest, it seems logical," Olesya Ilyina, an employee of the Department of General Ecology and Hydrobiology at the Faculty of Biology of Lomonosov Moscow State University, tells Izvestia.
A net can be used to cover a basketball field.
The group continues to search. Two hours later, there are two more nets on the deck — each strong, about 20 m long. This time there were no extreme finds, but it happened to get a package of meat, a bucket and even a Christmas tree. Divers are confident that there may be more strange finds in the still poorly explored southeast, between Baikalskaya and Tankhoi. There is also something interesting on the line from the village of Buguldeika to the island of Olkhon, where there was a fish factory during the Soviet era.
— The nets at the bottom of Lake Baikal are gigantic. Can you imagine a basketball court? These are approximately the areas covered by abandoned nets. On the one hand, it looks quite artistic. But when you think that it has been lying here for decades and continues to cause damage and living organisms get stuck in it... Nets have entangled the entire Baikal bottom, and it can be very difficult to pull them out," says Mikhail Sisenkov.
Переведено сервисом «Яндекс Переводчик»
