En enorm avloppsbrunn: Kan Östersjön fortfarande räddas?
Östersjön är övergödd, förorenad och full av bomber från andra världskriget, skriver Der Spiegel. Nu frågar sig dess försvarare om det är för sent att rädda havet, som är livsviktigt inte bara för de djur som lever i vattnet utan också människorna runt omkring. Tons of World War II munitions, a huge dead zone and global warming are putting the squeeze on the already highly vulnerable Baltic Sea. Can this crucial European body of water still be saved? By Johann Grolle 25 July, 2023 Uwe Krumme looks out across at the idyllic beach and the rugged cliffs behind it near Boltenhagen on the Baltic Sea in northern Germany. "People who go for walks there think they're in a perfect world," he says. "But below us, a few hundred meters from the beach, the death zone begins." He sniffs at the black-smeared tether of a buoy he has pulled up from the seabed. It smells foul, like hydrogen sulfide. Using the research boat of the Rostock Thünen Institute for Baltic Sea Fisheries, Krumme has sailed out to the telemetry field he marked out offshore from the cliff in Boltenhagen. Some 23 yellow buoys mark the 2-by-2.5-kilometer area where the marine biologist is trying to crack the riddle of the cod's decline. The stretch of coastline between Lübeck and Wismar seemed ideal for Krumme's purposes: The seabed here forms a slope that drops rapidly to a depth of 25 meters. With its sand, sea grass and stone, it provides a diverse habitat. More importantly: Local fishermen and anglers had told Krumme that this was a paradise for cod. The researcher planned to tag the fish with transmitters and study their temperature and water-depth preferences. Do they hide between rocks or burrow in the sand? But Krumme had a problem: Approval for his project took time, and by the time he finally got permission, the cod were gone. The few specimens he caught were too small for him to implant transmitters in their abdominal cavity. "We knew that things weren't good for the cod," Krumme says. But he also didn't expect everything to happen so quickly. "If someone had said 10 years ago that there would soon be no more cod in the Baltic Sea, we would have thought that person was nuts." Now the biologist will have to shift the focus of his research to plaice and flounder, which can luckily still be found here. But it is uncertain how much longer that will be the case. "The flatfish population has also declined," says Krumme. "It appears that food is getting scarce for them." The biologist, however, hasn't given up hope of finding out where the cod have gone. Since he can no longer get these answers from the fish themselves, he has sought out the help of Michael Naumann. The oceanographer from the Leibniz Institute for Baltic Sea Research in Warnemünde is on board for the trip. He's interested in the dynamics of the sea near the coast. The two researchers now want to combine biological and oceanographic expertise in the telemetry field off Boltenhagen to better understand the dynamics killing cod in the Baltic Sea. Krumme already has a theory, and initial data from Naumann appears to confirm it. The habitat for cod, Krumme explains, is limited by two parameters: They need oxygen, so they must avoid the low oxygen (anoxic) "dead zone" in the depths of the Baltic Sea. And they are cold-water fish, with metabolism that doesn't tolerate temperatures higher than 15 degrees Celsius (59 degrees Fahrenheit). June thus marks the beginning of a stressful period for cod. Their habitat is narrow on both sides in the summer: They are threatened with suffocation at the bottom, and with heat death at the top. And the danger from both sides is getting closer year by year. Global warming is causing the warm surface layer to reach deeper and deeper, and over-fertilization is causing an expansion of the anoxic death zone on the seafloor of shallow coastal regions in summer. In the worst-case scenario, the upper and lower water layers meet. "Then the trap snaps shut," says Krumme. The autumn storms, Naumann explains, further threaten the cod that survived the hard summer: When strong winds push surface water masses out to sea, deep water flows in from the seabed. But that water is anoxic, and it can mean death for the often already weakened cod. Not far from the bathers on the shore, something sinister is happening in the Baltic Sea. Climate change has set in motion changes in its ecological balance. The Baltic Sea is a one-of-a-kind body of water. Neither sea nor lake, it forms the largest body of brackish water on Earth. In the Gulf of Bothnia, into which the rivers of Finland and northern Sweden flow, the water is not much saltier than that of Lake Constance; towards the south and at greater depths, the salt content increases significantly. The Baltic Sea is regulated by the indefinite rhythm of saltwater inflows from the North Sea, making it a very dynamic, very sensitive, but very productive body of water. As far back as the times of the Hanseatic League, cod and herring nourished a rich fishing industry. But how much longer will the Baltic Sea continue to be of service to humanity? It is under more strain than almost any other sea. An average of 2,500 commercial vessels – ferries, cruise ships, tankers, container ships and leisure craft – are moving between Scandinavia, the Baltic states and the German coast at any given time. The underwater world is exposed to noise, trash and toxins. Some 85 million people live in the catchment area of this inland sea, meaning that a lot of industry, agriculture, traffic, and thus a lot of pollutants, exhaust fumes and fertilizers find their way into the Baltic Sea through wind and rivers. And while the flood of heavy metals and pesticides may now have been stemmed, the amount of nitrates, nitrogen oxides and phosphates that fertilize the Baltic Sea is still far too great. This promotes algae blooms that sink and deplete oxygen levels on the seafloor, where dead zones are spreading. There is also the danger presented by corroding World War II munitions. A total of 300,000 tons of explosives and probably up to 5,000 tons of chemical warfare agents were sunk off the German coast after the war. And efforts to restore the condition of the Baltic Sea are being counteracted by climate change. Higher water temperatures make it easier for invasive species to establish themselves. The warming can lead to the spread of new pathogens, and it encourages the proliferation of algae, which increases the number of dead zones. The pace of change is rapid. In terms of warming, the Baltic Sea is far outpacing the oceans. The water is getting 0.6 degrees warmer each decade, a rate of warming three times higher than in oceans. "We are observing a permanent heat wave," says Hamburg-based marine biologist Christian Möllmann. This is making the Baltic Sea a test case for Planet Earth. "It is a model for other coastal regions," says ecologist Thorsten Reusch of the GEOMAR Helmholtz Center for Ocean Research in Kiel. He and 26 fellow researchers wrote a widely acclaimed manifesto. In it, they declare the Baltic Sea to be a "time machine" that allows a glimpse into the future of the world's oceans. In the journal Science, the team of researchers paint a picture of a stressed body of water whose ecosystem is in disarray. But their report is nevertheless encouraging. Because, they write, the Baltic Sea is not only the most polluted, but also the best studied sea in the world. Some of the oceanographers' measurements stretch back far more than 100 years. This makes it possible reconstruct, understand and possibly control the processes in the water. According to Reusch and his colleagues, the Baltic Sea fulfills yet another superlative: They say it is also the world's best-managed sea. In fact, as early as 1974, the countries that line its coast signed an environmental agreement to protect the heavily polluted inland sea and established HELCOM, an authority based in Helsinki that monitors compliance. "A boat like this is actually made to last for an eternity," says Keld Kokholm. But for the vessel moored to the quay wall in front of him, that eternity only lasted for 15 years. "It was built in 2008, and the motor is two years old. The electronics are also top of the line." It's a shame to have to scrap something like this," he says. "But I don't want to complain. I'll earn money from it," he says. The Danish town of Grenaa on the eastern tip of Jutland, with its 14,000 inhabitants, a local museum, an aquarium, a ferry dock – and a large ship scrapping yard – is home to the cemetery for Baltic fishing. And Kokholm, the CEO and co-owner of the ship recycling company Fornaes, is the gravedigger. A large part of the fishing boats that are decommissioned in Germany, Denmark or Sweden wind up in Grenaa. There have been many in recent years. "We used to scrap six or seven fishing boats a year," says Kokholm. "This year, there were 40." By the end of September, half of the fleet of the Danish island of Bornholm will be on the books at Fornaes. Last year, it was the turn of the last two large trawl crawlers from Heiligenhafen, Germany. "There's not much left," he says. Year after year, new scrapping premiums are announced by governments to reduce fishing pressure on the Baltic herring and cod stocks. For the fishermen who collect these premiums, though, the entrance to Grenaa harbor marks the end of a family tradition that has often lasted generations. Many are filled with outrage. In their eyes, the culprits for the disaster are in Brussels. They grumble that EU bureaucrats have pushed catch limits further and further, while at the same time placing their competitors – seals and cormorants – under protection. The fact that a large part of the premiums they receive for decommissioning their fishing vessels also comes from Brussels is cold comfort to the fishermen. The radar antenna of the vessel in the quay in Grenaa has already been taken apart. A Fornaes worker is dismantling the furniture in the driver's cab. Every position light, every winch, every drum and every bracket that could still be reused is unscrewed, photographed, catalogued and then stored. More than 10,000 items are recorded on the Fornaes website. The shipyard in Grenaa operates what is perhaps the world's largest second-hand store for used marine and fishing equipment. In the past, Kokholm says, customers would often travel in person to browse the huge warehouses. But these days, Fornaes does most of its trade via the internet. The main exception are the fishermen from Morocco and Cameroon. "They come and stay in Grenaa for two weeks and, in the end, two containers full of fishing gear are shipped back to Africa." A world map in Kokholm's office show where the remains of the dying Baltic fishing industry have ended up. Red pins mark the places where Fornaes has delivered ship parts. They are especially dense in the Gulf of Guinea in Africa. After the parts are removed, everything else happens quickly. Powerful winches pull the gutted vessel ashore, where Fornaes workers finish the job with excavators and cutting torches. It takes two days until all that remains of the life at sea are a few piles sorted by materials: scrap metal, some wood – and a lot of hazardous waste. Tobias Goldschmidt is one of the architects of the shift to renewable energies in the northern German state of Schleswig-Holstein. Since he entered politics six years ago, first in a high-level ministerial job and now as environment minister in the state with the Green Party, he has been fighting on the climate change front. At some point, he realized that there is a second pressing crisis alongside the warming climate: dwindling biodiversity. "Climate change is attracting attention through disasters, through storms, floods and droughts," Goldschmidt says. "The die-out of species, on the other hand, is taking place in silence." The drama is playing out right before the minister's eyes, in the fjords of the state capital of Kiel, which his office looks out on. "The ecosystem of the Baltic Sea is not in good shape," the ministry's website says. Eutrophication, old ammunition, ship noise, pollutants and invasive species are all affecting the inland sea. In response, the minister devised a bold plan: He wants to declare this badly damaged ecosystem a national park – and turn what has effectively been treated as a dump site into a protected area. "We alone will not be able to save the Baltic Sea," Goldschmidt acknowledges. Each of the countries that borders the sea must make its contribution, he says, and Schleswig-Holstein's role should be to create a national park. The details are still a matter of negotiation. So far, it's only the "potential setting" that is clear: The large marine areas south of the Flensburg Fjord, around the mouth of the Schlei River and the Eckernförde Bay to the east of Fehmarn are all possible areas to be included in the national park. Right now, all the stakeholders are being invited to "consultations": farmers, fishermen, water sports enthusiasts and shipping and tourism associations. It's likely that Goldschmidt will face a lot of resentment during the hearings. Resistance is already forming: The fishermen want to continue to deploy their nets, sailors fear that they could be denied access to the most beautiful areas and farmers complain that the tightening of a law on the use of manure is already causing them enough trouble even without any national park. But the loudest rants are coming from the kitesurfers. The debate makes clear the strength of people’s bonds to the Baltic Sea. And that the wilderness the conservationists are so keen to preserve still has to be created in the first place. The planned conservation area, if officials do decide to go forward with it after the consultations, would be the blueprint for a national park that doesn’t yet exist. Rangers would first have to establish new habitats for the crabs, starfish, snails and fish larvae by planting sea grass beds and sinking artificial reefs. Even with all these measures, it still won't be possible to restore the Baltic Sea as it once was. Nutrient loads will remain far above natural levels for decades to come. Engine noise from nearby shipping lanes will not be banished from the protected area. More importantly: The Baltic Sea is warmer than it has ever been, and the temperature will continue to rise. For that very reason, Karen Wiltshire believes it is "essential" to establish a national park. "We need to wake up," she says. "We need more protection, and we need to designate large areas for it," says the marine ecologist with the Alfred Wegener Institute for Polar and Marine Research in Bremerhaven. She believes Goldschmidt's approach is correct. "The most important thing now is to get everyone around the table." Otherwise, fishermen, farmers, shipping and the tourism industry will just point fingers at each other. Each of the stakeholders now shares responsibility for the success of the national park project, she says. "It's about conservation, but it's also about the message that a project like this will send," Wiltshire says. Two years ago, much of the land on which the Rødbyhavn factories were built was still the Baltic Sea. Then 300 hectares (741 acres) of land were reclaimed from the sea. The sand and marl heaped up here come from the seabed, from an 18-kilometer-long trench that some of the world's largest dredgers are currently digging there. The factory is used for the manufacture of enormous concrete pipes that are to be used to assemble the Fehmarn Belt Tunnel between Rødby in Denmark and Puttgarden in Germany, one of the most expensive and largest infrastructure projects currently underway in Europe. The tunnel is composed of 89 segments, most of them 42 meters wide (138 feet) and 217 meters long. These monsters, each as heavy as seven Eiffel Towers, must be moved into the newly created harbor, pushed out into the Baltic Sea and then lowered into the trench at the bottom. A total of 3.2 million cubic meters of concrete will be used. The large construction site has been erected in an ecologically sensitive location. Species-rich reefs, sea grass meadows and brown algae forests extend through the marine area north of Fehmarn, and it is also a spawning area for herring and cod. The Fehmarn Belt is a gateway through which sea larks, starfish and bristle worms drift, and it also serves as a migration route for harbor porpoises. The terrain around Fehmarn is a centerpiece of Goldschmidt's proposed national park. Most importantly, the Belt is a vital breathing path for the Baltic Sea. About 70 percent of the water exchange with the North Sea takes place through this strait. This provides an influx of the oxygen-rich salt water that is so important for aerating the Baltic. For people, the strait between Germany and Denmark has also always been an important artery. Around 40,000 ships pass through the Belt each year, including many tankers, cruise ships and container ships. Ferries between Germany and Denmark here also run every 30 minutes. According to the current schedule, the tunnel is set to open in 2029. Its operators are expecting it to be used by 12,000 vehicles a day and allow trains to race under the water at speeds of up to 200 kilometers per hour. With the crossings at the Fehmarn Belt between Germany and Denmark and the Øresund Bridge between Denmark and Sweden, road and rail will wrap around the entire Baltic Sea. In terms of transport, this will make the Baltic a fully inland sea. And the record-breaking tunnel under the Fehmarn Belt is far from the only infrastructure project in the Baltic region. Finland and Estonia, for example, have also been exploring the idea of connecting their two capital cities with an even longer tunnel. A bridge across the Gulf of Bothnia between Sweden and Finland has even been considered. Copenhagen, meanwhile, has plans to build an artificial island with housing for 35,000 people. Intended as a bulwark against storm surges amid climate change, it will be located in the Öresund, the second route through which salt water can enter the Baltic Sea. Meanwhile, shipping traffic is increasing each year. Ports are being expanded in almost all the countries lining the Baltic. In Świnoujście, for example, on the Polish-German border, one of the largest container terminals in the Baltic Sea is to be built by the Poles, surrounded by bird and nature reserves. The energy industry is also taking its toll: With the Nord Stream 1 and 2 gas pipelines now lying unused at the bottom of the sea, there is a dispute off the island of Rügen over whether to build an LNG terminal for liquefied natural gas tankers. At the same time, new offshore wind farms are being built all around the Baltic. Can a sea withstand that kind of intensive use in the long term? The Danish state-owned company Femern A/S, which is building the Fehmarn Belt Tunnel, has emphasized the environmental compatibility of its project. The company is regularly monitoring the turbidity of the water from sediment stirred up by construction. It is also trying to ensure that noise from the dredging work doesn't exceed the limits tolerated by harbor porpoises. And after construction is completed, the company says, the seabed will be restored so that no permanent damage is done. The project managers paint a picture of a well-tended nature that can exist in harmony with man-made structures. And they appear to be prevailing with their view. At the end of last year, the Federal Administrative Court in Leipzig rejected the objections of nature conservationists to the tunnel project. In the case of large offshore wind farms, many ecologists even see a benefit to marine life. While it’s true that the construction noise harms harbor porpoises and that the rotors of the turbines are bad for birds, the mighty concrete foundations also develop into underwater oases where mussels, sponges, tunicates and sea anemones find new habitats. Cod also like to retreat here, where they are safe from the fishermen's nets. Each time Aaron Beck goes swimming on the beach at Laboe on the Kiel Fjord, he finds finger-thick rods. Initially, he thought they were fossils. Today, he knows that it is stick powder made from cellulose nitrate, once used in the propellant charge of artillery shells of the Wehrmacht, the Nazi military. There's more to the German Baltic Sea than beach chairs, lighthouses and hidden bays – it is also home to explosives and chemical weapons. At the mouth of Kiel Fjord, but also in other dumping areas, such as off the coast of Lübeck and south of Flensburg, shells, torpedoes, bazookas and other war materiel lie on the seabed, totaling an estimated 300,000 tons. Beck is a marine chemist at GEOMAR, the Kiel-based research center, where he addresses this toxic legacy of World War II in his work. As recently as March, he and his colleagues discovered several V1 rocket charges, each consisting of around a ton of explosives. The exploration of the explosive underwater dumps was initiated by Beck's GEOMAR colleague Jens Greinert. When he learned about the munitions at the bottom of the Baltic Sea in 2015, he felt the same way as most of the citizens of Kiel. "I had no idea what was on our doorstep." He wondered: Isn't something like that dangerous? Since then, the issue has been his primary focus. In order to demilitarize Germany, the Allies decided in 1945 to dispose of the legacy of the Wehrmacht in the sea. Fully loaded fishing boats and barges sailed offshore to dump the ammunition overboard, crate by crate. The timing, location and quantities of these munitions dumps can only be roughly approximated based on information provided by harbor officials. The paucity of information led Greinert to first acoustically measure the trash dumps on the seafloor using echosounders. He then used underwater robots to film the places where the World War II debris is most densely located and computed the data into 3-D images. Based on these images, experts from Germany's Explosive Ordnance Disposal Service are now examining whether the contaminated site can be salvaged and destroyed. The German government has earmarked 100 million euros for an emergency program. Next year, a pilot project will raise munitions from these dumps on the seabed for the first time. Based on Greinert's readings, the clearance team declared that much of the explosive materiel is still transportable. They are concerned about cluster bombs, however, which have a risk of exploding. It is still unclear what will happen after the munitions are salvaged. "The real problem is destroying them," Greinert explains. One idea being considered is a dedicated platform for disposal at sea. But it won't be easy: The explosive space on board must be designed to withstand a detonation of up to one ton of TNT if a worst-case scenario unfolds. How truly harmful are the munitions dumps? Chemist Beck has developed a method that allows him to detect TNT even hundreds of miles from dump sites. This allowed him to prove that the explosives are dissolving in the water and spreading throughout the sea. They are also detectable in animals. In the Bay of Kiel trace elements of explosives can be found in mussels, worms, snails and fish. They are small quantities and thus harmless to humans. Beck has calculated that critical values would only be reached if a person consumed 7 kilos (around 15 pounds) of fish a day. Still, he warns, TNT and its degradation products are carcinogenic. And the longer the metal shells corrode, the greater the amount of explosives dissolving in the water. Flatfish in the Bay of Kiel are already suffering increased liver tumors. The Helsinki Commission is something like a government for the Baltic Sea, and Rüdiger Strempel is its leader. At the same time, though, HELCOM lacks any executive power. It can issue recommendations, but it cannot enforce them. HELCOM's offices in a side wing of the congress center at the ferry pier in Helsinki are currently being renovated. But that's the least of Strempel's problems. "The Baltic Sea is doing badly," he explains, only to immediately qualify that statement. "But it's getting better." Without that optimism, it would be difficult for him to succeed in this job. There are difficulties not only on the environmental front, but also on the political one. All official HELCOM meetings are currently suspended until further notice, and relations with Russia, one of the nine member countries, are on hold because of the Ukraine war. Still, Strempel doesn't want to let that shake his optimism. "Russia is still a member of HELCOM," he assures, with a hint of defiance. He also adds: "We're able to do our work." HELCOM was founded in 1974. At the time, the Baltic Sea had the reputation of being the world's dirtiest sea. The emergency was felt to be so pressing that seven countries along the Baltic decided to embark on a unique experiment. At the time, people were becoming increasingly aware of water pollution and began cleaning up rivers and lakes. But a whole sea? Nothing like that had happened before. And yet, in the midst of the Cold War, seven mutually hostile countries – three communist and four Western capitalist – set out to jointly forge a rescue plan for the Baltic Sea. That was almost 50 years ago. Much research was done during this period under the auspices of HELCOM, many papers were written, and numerous measures were initiated and monitored. The record, however, is mixed at best. There are good things to report: Seal populations, for example, have recovered. Grey seals, Germany's largest free-living predators, weighing up to 300 kilograms and measuring 2.50 meters in length, are once again lolling about on the sandbanks in Wismar Bay. Many seabirds, such as guillemots, are also doing better. Nevertheless, it turns out that cleaning up a sea is more costly than a river or a lake. The inland Baltic Sea holds 30,000 times more water than the Müritz, Germany's second largest lake after Lake Constance. To fill it, a river like the Oder would need about a thousand years. Managing such a water body ecologically is a gigantic task. Even more so if it also requires international agreement. The most important goal on the way to a healthy Baltic Sea is the control of nutrient inputs. If large amounts of nitrogen and phosphorus continue to flow into the inland sea through more than 200 rivers, large algae blooms will grow, which in turn will lead to the expansion of the dead zone on the ocean floor. Over the decades, a massive cesspool has accumulated there. HELCOM Executive Secretary Strempel is proud to have stemmed the influx of nutrients. From peaks of up to 1 million tons of nitrogen and 70,000 tons of phosphorus, inputs have declined to the current level of about 600,000 tons of nitrogen and 25,000 tons of phosphorus per year. But that's not enough to reverse the trend. The anoxic dead zone continues to grow. Conditions in the Baltic Sea are still a long way from pre-industrial levels, when inputs were less than half of those today. The cleanup is complicated by the fact that any pollutants that enter the inland sea remain there for many years. On average, it takes 30 years for them to be washed across the Kattegat into the North Sea. Phosphorus poses a particular problem: Large amounts of the element have been embedded in sediment during decades of uncritical over-fertilization. Phosphorus clean-up is thus proving to be a Sisyphean task: As soon as the concentration in the seawater drops somewhat, the contaminated material dissolves, causing phosphorus levels to rise again. It will take decades to erase the sins of the past. Susi, Florian and 14 other third graders from the Ostseeblick elementary school in Sassnitz on the island of Rügen had quite a bit going on this morning. They learned what living fossils, barbels and anadromous migratory fish are. Most importantly, they held live sturgeon in their hands. The children were able to touch the sharp-edged bone plates on the backs of the fish. They each lent a hand to lift their firm, strong bodies out of a large plastic tub. And they then let the creatures slide down a wooden chute from the pier of Sassnitz harbor into the Baltic Sea. The sturgeons quickly disappeared into the murky water and immediately set about digging at the bottom for snails, worms or crabs, as captured by WWF divers who filmed the event. With their pointed head, protruding mouth, four tactile barbels and five rows of bony plates, sturgeons have survived largely unchanged since the time of the dinosaurs. Some sturgeons are giants. The largest specimen ever caught was reportedly 7.2 meters long. The Baltic sturgeons that once lived in the Baltic Sea didn't grow to be quite as large, but they could reach four meters in length. The last specimen born in the wild was caught off Estonia in 1996. It was a female, 2.90 meters long and 136 kilograms. They extracted 15 kilograms of roe in its ovaries. Since then, the Baltic sturgeon has become extinct in the Baltic. Female sturgeon are still kept by the Mecklenburg-Western Pomerania State Research Institute (LFA) in Born on Germany's Darss peninsula. The spawn is then nurtured for release after one year, usually after they reach 50 to 70 centimeters (20 to 27 inches) in length, into the Oder River, the Szczecin Lagoon or, as in Sassnitz, directly into the Baltic Sea. At the same time, sturgeon breeders are shipping newly hatched animals to Poland and the Baltic States, as part of an action plan for the reintroduction of Baltic sturgeon set up by HELCOM that is slated to run until 2029. LFA researcher Stefanie Felsing, who organized the stocking measure in Sassnitz, is confident that it will be possible to reintroduce the fish to the Baltic Sea. She has already been contacted by fishermen who have caught some of the tagged creatures. The scientists implant acoustic transmitters in the abdominal cavity of larger specimens. Tracking stations have now been set up around Rügen, but also elsewhere in the Baltic – near Bornholm, for example. This makes it possible to better understand how the reintroduced species reacquire their former habitats. However, the program suffered a major setback last year. The problem is that the Baltic sturgeon is an anadromous migratory fish, meaning it leaves the sea to reproduce and swims up streams, including the Oder River, in search of spawning grounds. But the Oder was hit by a catastrophic fish die-out last summer. The toxic water alga Prymnesium parvum had spread. Because of the low water level, the high temperatures and, especially, the high salinity in the Oder River, the algae found ideal conditions to grow. Hundreds of tons of dead fish were removed from the river, including dozens of sturgeon. In two nurseries operated along the Oder, almost all the offspring were destroyed. It also looks like the disaster could repeat itself in the future. The toxic algae is lurking in the sediment, waiting for favorable conditions. And those could be coming: Climate change is causing heat and droughts, and the salt comes from Polish coal mining. So far, though, the Poles have also shown little understanding for the issue. Instead of addressing the cause of the disaster, they are trying to fight the algae with hydrogen peroxide. Plans are also underway in Poland to expand the river's course. When this occurs, the speed of the flow increases, and many of the calm gravel beds that sturgeon need to spawn will disappear. Perhaps there is no longer a place for the sturgeon, these primordial creatures, in this man-made world. Perhaps the project will fail, and the stench of rot that hung over the floodplains of the Lower Oder Valley National Park last summer will become a portent of the Baltic's inexorable decline. Or perhaps the tough negotiations currently being conducted by the German and Polish governments will be prove fruitful in the end. And maybe it will be possible to reintroduce the Baltic Sea's largest fish into the ecosystem after all, so that some of the animals released into the open sea by the third-grade students will find their way to a spawning ground in the Oder, Vistula or Memel rivers in 15 years' time, when they are sexually mature. Living fossils could then become a symbol for a Baltic Sea that is getting healthier. Then, 50 years from now, the children will be able to remember that they helped save these giants from extinction. © 2023 Der Spiegel. Distributed by The New York Times Licensing Group. Read the original article at Der Spiegel.
Östersjön är övergödd, förorenad och full av bomber från andra världskriget, skriver Der Spiegel. Nu frågar sig dess försvarare om det är för sent att rädda havet, som är livsviktigt inte bara för de djur som lever i vattnet utan också människorna runt omkring. Tons of World War II munitions, a huge dead zone and global warming are putting the squeeze on the already highly vulnerable Baltic Sea. Can this crucial European body of water still be saved? By Johann Grolle 25 July, 2023 Uwe Krumme looks out across at the idyllic beach and the rugged cliffs behind it near Boltenhagen on the Baltic Sea in northern Germany. "People who go for walks there think they're in a perfect world," he says. "But below us, a few hundred meters from the beach, the death zone begins." He sniffs at the black-smeared tether of a buoy he has pulled up from the seabed. It smells foul, like hydrogen sulfide. Using the research boat of the Rostock Thünen Institute for Baltic Sea Fisheries, Krumme has sailed out to the telemetry field he marked out offshore from the cliff in Boltenhagen. Some 23 yellow buoys mark the 2-by-2.5-kilometer area where the marine biologist is trying to crack the riddle of the cod's decline. The stretch of coastline between Lübeck and Wismar seemed ideal for Krumme's purposes: The seabed here forms a slope that drops rapidly to a depth of 25 meters. With its sand, sea grass and stone, it provides a diverse habitat. More importantly: Local fishermen and anglers had told Krumme that this was a paradise for cod. The researcher planned to tag the fish with transmitters and study their temperature and water-depth preferences. Do they hide between rocks or burrow in the sand? But Krumme had a problem: Approval for his project took time, and by the time he finally got permission, the cod were gone. The few specimens he caught were too small for him to implant transmitters in their abdominal cavity. "We knew that things weren't good for the cod," Krumme says. But he also didn't expect everything to happen so quickly. "If someone had said 10 years ago that there would soon be no more cod in the Baltic Sea, we would have thought that person was nuts." Now the biologist will have to shift the focus of his research to plaice and flounder, which can luckily still be found here. But it is uncertain how much longer that will be the case. "The flatfish population has also declined," says Krumme. "It appears that food is getting scarce for them." The biologist, however, hasn't given up hope of finding out where the cod have gone. Since he can no longer get these answers from the fish themselves, he has sought out the help of Michael Naumann. The oceanographer from the Leibniz Institute for Baltic Sea Research in Warnemünde is on board for the trip. He's interested in the dynamics of the sea near the coast. The two researchers now want to combine biological and oceanographic expertise in the telemetry field off Boltenhagen to better understand the dynamics killing cod in the Baltic Sea. Krumme already has a theory, and initial data from Naumann appears to confirm it. The habitat for cod, Krumme explains, is limited by two parameters: They need oxygen, so they must avoid the low oxygen (anoxic) "dead zone" in the depths of the Baltic Sea. And they are cold-water fish, with metabolism that doesn't tolerate temperatures higher than 15 degrees Celsius (59 degrees Fahrenheit). June thus marks the beginning of a stressful period for cod. Their habitat is narrow on both sides in the summer: They are threatened with suffocation at the bottom, and with heat death at the top. And the danger from both sides is getting closer year by year. Global warming is causing the warm surface layer to reach deeper and deeper, and over-fertilization is causing an expansion of the anoxic death zone on the seafloor of shallow coastal regions in summer. In the worst-case scenario, the upper and lower water layers meet. "Then the trap snaps shut," says Krumme. The autumn storms, Naumann explains, further threaten the cod that survived the hard summer: When strong winds push surface water masses out to sea, deep water flows in from the seabed. But that water is anoxic, and it can mean death for the often already weakened cod. Not far from the bathers on the shore, something sinister is happening in the Baltic Sea. Climate change has set in motion changes in its ecological balance. The Baltic Sea is a one-of-a-kind body of water. Neither sea nor lake, it forms the largest body of brackish water on Earth. In the Gulf of Bothnia, into which the rivers of Finland and northern Sweden flow, the water is not much saltier than that of Lake Constance; towards the south and at greater depths, the salt content increases significantly. The Baltic Sea is regulated by the indefinite rhythm of saltwater inflows from the North Sea, making it a very dynamic, very sensitive, but very productive body of water. As far back as the times of the Hanseatic League, cod and herring nourished a rich fishing industry. But how much longer will the Baltic Sea continue to be of service to humanity? It is under more strain than almost any other sea. An average of 2,500 commercial vessels – ferries, cruise ships, tankers, container ships and leisure craft – are moving between Scandinavia, the Baltic states and the German coast at any given time. The underwater world is exposed to noise, trash and toxins. Some 85 million people live in the catchment area of this inland sea, meaning that a lot of industry, agriculture, traffic, and thus a lot of pollutants, exhaust fumes and fertilizers find their way into the Baltic Sea through wind and rivers. And while the flood of heavy metals and pesticides may now have been stemmed, the amount of nitrates, nitrogen oxides and phosphates that fertilize the Baltic Sea is still far too great. This promotes algae blooms that sink and deplete oxygen levels on the seafloor, where dead zones are spreading. There is also the danger presented by corroding World War II munitions. A total of 300,000 tons of explosives and probably up to 5,000 tons of chemical warfare agents were sunk off the German coast after the war. And efforts to restore the condition of the Baltic Sea are being counteracted by climate change. Higher water temperatures make it easier for invasive species to establish themselves. The warming can lead to the spread of new pathogens, and it encourages the proliferation of algae, which increases the number of dead zones. The pace of change is rapid. In terms of warming, the Baltic Sea is far outpacing the oceans. The water is getting 0.6 degrees warmer each decade, a rate of warming three times higher than in oceans. "We are observing a permanent heat wave," says Hamburg-based marine biologist Christian Möllmann. This is making the Baltic Sea a test case for Planet Earth. "It is a model for other coastal regions," says ecologist Thorsten Reusch of the GEOMAR Helmholtz Center for Ocean Research in Kiel. He and 26 fellow researchers wrote a widely acclaimed manifesto. In it, they declare the Baltic Sea to be a "time machine" that allows a glimpse into the future of the world's oceans. In the journal Science, the team of researchers paint a picture of a stressed body of water whose ecosystem is in disarray. But their report is nevertheless encouraging. Because, they write, the Baltic Sea is not only the most polluted, but also the best studied sea in the world. Some of the oceanographers' measurements stretch back far more than 100 years. This makes it possible reconstruct, understand and possibly control the processes in the water. According to Reusch and his colleagues, the Baltic Sea fulfills yet another superlative: They say it is also the world's best-managed sea. In fact, as early as 1974, the countries that line its coast signed an environmental agreement to protect the heavily polluted inland sea and established HELCOM, an authority based in Helsinki that monitors compliance. "A boat like this is actually made to last for an eternity," says Keld Kokholm. But for the vessel moored to the quay wall in front of him, that eternity only lasted for 15 years. "It was built in 2008, and the motor is two years old. The electronics are also top of the line." It's a shame to have to scrap something like this," he says. "But I don't want to complain. I'll earn money from it," he says. The Danish town of Grenaa on the eastern tip of Jutland, with its 14,000 inhabitants, a local museum, an aquarium, a ferry dock – and a large ship scrapping yard – is home to the cemetery for Baltic fishing. And Kokholm, the CEO and co-owner of the ship recycling company Fornaes, is the gravedigger. A large part of the fishing boats that are decommissioned in Germany, Denmark or Sweden wind up in Grenaa. There have been many in recent years. "We used to scrap six or seven fishing boats a year," says Kokholm. "This year, there were 40." By the end of September, half of the fleet of the Danish island of Bornholm will be on the books at Fornaes. Last year, it was the turn of the last two large trawl crawlers from Heiligenhafen, Germany. "There's not much left," he says. Year after year, new scrapping premiums are announced by governments to reduce fishing pressure on the Baltic herring and cod stocks. For the fishermen who collect these premiums, though, the entrance to Grenaa harbor marks the end of a family tradition that has often lasted generations. Many are filled with outrage. In their eyes, the culprits for the disaster are in Brussels. They grumble that EU bureaucrats have pushed catch limits further and further, while at the same time placing their competitors – seals and cormorants – under protection. The fact that a large part of the premiums they receive for decommissioning their fishing vessels also comes from Brussels is cold comfort to the fishermen. The radar antenna of the vessel in the quay in Grenaa has already been taken apart. A Fornaes worker is dismantling the furniture in the driver's cab. Every position light, every winch, every drum and every bracket that could still be reused is unscrewed, photographed, catalogued and then stored. More than 10,000 items are recorded on the Fornaes website. The shipyard in Grenaa operates what is perhaps the world's largest second-hand store for used marine and fishing equipment. In the past, Kokholm says, customers would often travel in person to browse the huge warehouses. But these days, Fornaes does most of its trade via the internet. The main exception are the fishermen from Morocco and Cameroon. "They come and stay in Grenaa for two weeks and, in the end, two containers full of fishing gear are shipped back to Africa." A world map in Kokholm's office show where the remains of the dying Baltic fishing industry have ended up. Red pins mark the places where Fornaes has delivered ship parts. They are especially dense in the Gulf of Guinea in Africa. After the parts are removed, everything else happens quickly. Powerful winches pull the gutted vessel ashore, where Fornaes workers finish the job with excavators and cutting torches. It takes two days until all that remains of the life at sea are a few piles sorted by materials: scrap metal, some wood – and a lot of hazardous waste. Tobias Goldschmidt is one of the architects of the shift to renewable energies in the northern German state of Schleswig-Holstein. Since he entered politics six years ago, first in a high-level ministerial job and now as environment minister in the state with the Green Party, he has been fighting on the climate change front. At some point, he realized that there is a second pressing crisis alongside the warming climate: dwindling biodiversity. "Climate change is attracting attention through disasters, through storms, floods and droughts," Goldschmidt says. "The die-out of species, on the other hand, is taking place in silence." The drama is playing out right before the minister's eyes, in the fjords of the state capital of Kiel, which his office looks out on. "The ecosystem of the Baltic Sea is not in good shape," the ministry's website says. Eutrophication, old ammunition, ship noise, pollutants and invasive species are all affecting the inland sea. In response, the minister devised a bold plan: He wants to declare this badly damaged ecosystem a national park – and turn what has effectively been treated as a dump site into a protected area. "We alone will not be able to save the Baltic Sea," Goldschmidt acknowledges. Each of the countries that borders the sea must make its contribution, he says, and Schleswig-Holstein's role should be to create a national park. The details are still a matter of negotiation. So far, it's only the "potential setting" that is clear: The large marine areas south of the Flensburg Fjord, around the mouth of the Schlei River and the Eckernförde Bay to the east of Fehmarn are all possible areas to be included in the national park. Right now, all the stakeholders are being invited to "consultations": farmers, fishermen, water sports enthusiasts and shipping and tourism associations. It's likely that Goldschmidt will face a lot of resentment during the hearings. Resistance is already forming: The fishermen want to continue to deploy their nets, sailors fear that they could be denied access to the most beautiful areas and farmers complain that the tightening of a law on the use of manure is already causing them enough trouble even without any national park. But the loudest rants are coming from the kitesurfers. The debate makes clear the strength of people’s bonds to the Baltic Sea. And that the wilderness the conservationists are so keen to preserve still has to be created in the first place. The planned conservation area, if officials do decide to go forward with it after the consultations, would be the blueprint for a national park that doesn’t yet exist. Rangers would first have to establish new habitats for the crabs, starfish, snails and fish larvae by planting sea grass beds and sinking artificial reefs. Even with all these measures, it still won't be possible to restore the Baltic Sea as it once was. Nutrient loads will remain far above natural levels for decades to come. Engine noise from nearby shipping lanes will not be banished from the protected area. More importantly: The Baltic Sea is warmer than it has ever been, and the temperature will continue to rise. For that very reason, Karen Wiltshire believes it is "essential" to establish a national park. "We need to wake up," she says. "We need more protection, and we need to designate large areas for it," says the marine ecologist with the Alfred Wegener Institute for Polar and Marine Research in Bremerhaven. She believes Goldschmidt's approach is correct. "The most important thing now is to get everyone around the table." Otherwise, fishermen, farmers, shipping and the tourism industry will just point fingers at each other. Each of the stakeholders now shares responsibility for the success of the national park project, she says. "It's about conservation, but it's also about the message that a project like this will send," Wiltshire says. Two years ago, much of the land on which the Rødbyhavn factories were built was still the Baltic Sea. Then 300 hectares (741 acres) of land were reclaimed from the sea. The sand and marl heaped up here come from the seabed, from an 18-kilometer-long trench that some of the world's largest dredgers are currently digging there. The factory is used for the manufacture of enormous concrete pipes that are to be used to assemble the Fehmarn Belt Tunnel between Rødby in Denmark and Puttgarden in Germany, one of the most expensive and largest infrastructure projects currently underway in Europe. The tunnel is composed of 89 segments, most of them 42 meters wide (138 feet) and 217 meters long. These monsters, each as heavy as seven Eiffel Towers, must be moved into the newly created harbor, pushed out into the Baltic Sea and then lowered into the trench at the bottom. A total of 3.2 million cubic meters of concrete will be used. The large construction site has been erected in an ecologically sensitive location. Species-rich reefs, sea grass meadows and brown algae forests extend through the marine area north of Fehmarn, and it is also a spawning area for herring and cod. The Fehmarn Belt is a gateway through which sea larks, starfish and bristle worms drift, and it also serves as a migration route for harbor porpoises. The terrain around Fehmarn is a centerpiece of Goldschmidt's proposed national park. Most importantly, the Belt is a vital breathing path for the Baltic Sea. About 70 percent of the water exchange with the North Sea takes place through this strait. This provides an influx of the oxygen-rich salt water that is so important for aerating the Baltic. For people, the strait between Germany and Denmark has also always been an important artery. Around 40,000 ships pass through the Belt each year, including many tankers, cruise ships and container ships. Ferries between Germany and Denmark here also run every 30 minutes. According to the current schedule, the tunnel is set to open in 2029. Its operators are expecting it to be used by 12,000 vehicles a day and allow trains to race under the water at speeds of up to 200 kilometers per hour. With the crossings at the Fehmarn Belt between Germany and Denmark and the Øresund Bridge between Denmark and Sweden, road and rail will wrap around the entire Baltic Sea. In terms of transport, this will make the Baltic a fully inland sea. And the record-breaking tunnel under the Fehmarn Belt is far from the only infrastructure project in the Baltic region. Finland and Estonia, for example, have also been exploring the idea of connecting their two capital cities with an even longer tunnel. A bridge across the Gulf of Bothnia between Sweden and Finland has even been considered. Copenhagen, meanwhile, has plans to build an artificial island with housing for 35,000 people. Intended as a bulwark against storm surges amid climate change, it will be located in the Öresund, the second route through which salt water can enter the Baltic Sea. Meanwhile, shipping traffic is increasing each year. Ports are being expanded in almost all the countries lining the Baltic. In Świnoujście, for example, on the Polish-German border, one of the largest container terminals in the Baltic Sea is to be built by the Poles, surrounded by bird and nature reserves. The energy industry is also taking its toll: With the Nord Stream 1 and 2 gas pipelines now lying unused at the bottom of the sea, there is a dispute off the island of Rügen over whether to build an LNG terminal for liquefied natural gas tankers. At the same time, new offshore wind farms are being built all around the Baltic. Can a sea withstand that kind of intensive use in the long term? The Danish state-owned company Femern A/S, which is building the Fehmarn Belt Tunnel, has emphasized the environmental compatibility of its project. The company is regularly monitoring the turbidity of the water from sediment stirred up by construction. It is also trying to ensure that noise from the dredging work doesn't exceed the limits tolerated by harbor porpoises. And after construction is completed, the company says, the seabed will be restored so that no permanent damage is done. The project managers paint a picture of a well-tended nature that can exist in harmony with man-made structures. And they appear to be prevailing with their view. At the end of last year, the Federal Administrative Court in Leipzig rejected the objections of nature conservationists to the tunnel project. In the case of large offshore wind farms, many ecologists even see a benefit to marine life. While it’s true that the construction noise harms harbor porpoises and that the rotors of the turbines are bad for birds, the mighty concrete foundations also develop into underwater oases where mussels, sponges, tunicates and sea anemones find new habitats. Cod also like to retreat here, where they are safe from the fishermen's nets. Each time Aaron Beck goes swimming on the beach at Laboe on the Kiel Fjord, he finds finger-thick rods. Initially, he thought they were fossils. Today, he knows that it is stick powder made from cellulose nitrate, once used in the propellant charge of artillery shells of the Wehrmacht, the Nazi military. There's more to the German Baltic Sea than beach chairs, lighthouses and hidden bays – it is also home to explosives and chemical weapons. At the mouth of Kiel Fjord, but also in other dumping areas, such as off the coast of Lübeck and south of Flensburg, shells, torpedoes, bazookas and other war materiel lie on the seabed, totaling an estimated 300,000 tons. Beck is a marine chemist at GEOMAR, the Kiel-based research center, where he addresses this toxic legacy of World War II in his work. As recently as March, he and his colleagues discovered several V1 rocket charges, each consisting of around a ton of explosives. The exploration of the explosive underwater dumps was initiated by Beck's GEOMAR colleague Jens Greinert. When he learned about the munitions at the bottom of the Baltic Sea in 2015, he felt the same way as most of the citizens of Kiel. "I had no idea what was on our doorstep." He wondered: Isn't something like that dangerous? Since then, the issue has been his primary focus. In order to demilitarize Germany, the Allies decided in 1945 to dispose of the legacy of the Wehrmacht in the sea. Fully loaded fishing boats and barges sailed offshore to dump the ammunition overboard, crate by crate. The timing, location and quantities of these munitions dumps can only be roughly approximated based on information provided by harbor officials. The paucity of information led Greinert to first acoustically measure the trash dumps on the seafloor using echosounders. He then used underwater robots to film the places where the World War II debris is most densely located and computed the data into 3-D images. Based on these images, experts from Germany's Explosive Ordnance Disposal Service are now examining whether the contaminated site can be salvaged and destroyed. The German government has earmarked 100 million euros for an emergency program. Next year, a pilot project will raise munitions from these dumps on the seabed for the first time. Based on Greinert's readings, the clearance team declared that much of the explosive materiel is still transportable. They are concerned about cluster bombs, however, which have a risk of exploding. It is still unclear what will happen after the munitions are salvaged. "The real problem is destroying them," Greinert explains. One idea being considered is a dedicated platform for disposal at sea. But it won't be easy: The explosive space on board must be designed to withstand a detonation of up to one ton of TNT if a worst-case scenario unfolds. How truly harmful are the munitions dumps? Chemist Beck has developed a method that allows him to detect TNT even hundreds of miles from dump sites. This allowed him to prove that the explosives are dissolving in the water and spreading throughout the sea. They are also detectable in animals. In the Bay of Kiel trace elements of explosives can be found in mussels, worms, snails and fish. They are small quantities and thus harmless to humans. Beck has calculated that critical values would only be reached if a person consumed 7 kilos (around 15 pounds) of fish a day. Still, he warns, TNT and its degradation products are carcinogenic. And the longer the metal shells corrode, the greater the amount of explosives dissolving in the water. Flatfish in the Bay of Kiel are already suffering increased liver tumors. The Helsinki Commission is something like a government for the Baltic Sea, and Rüdiger Strempel is its leader. At the same time, though, HELCOM lacks any executive power. It can issue recommendations, but it cannot enforce them. HELCOM's offices in a side wing of the congress center at the ferry pier in Helsinki are currently being renovated. But that's the least of Strempel's problems. "The Baltic Sea is doing badly," he explains, only to immediately qualify that statement. "But it's getting better." Without that optimism, it would be difficult for him to succeed in this job. There are difficulties not only on the environmental front, but also on the political one. All official HELCOM meetings are currently suspended until further notice, and relations with Russia, one of the nine member countries, are on hold because of the Ukraine war. Still, Strempel doesn't want to let that shake his optimism. "Russia is still a member of HELCOM," he assures, with a hint of defiance. He also adds: "We're able to do our work." HELCOM was founded in 1974. At the time, the Baltic Sea had the reputation of being the world's dirtiest sea. The emergency was felt to be so pressing that seven countries along the Baltic decided to embark on a unique experiment. At the time, people were becoming increasingly aware of water pollution and began cleaning up rivers and lakes. But a whole sea? Nothing like that had happened before. And yet, in the midst of the Cold War, seven mutually hostile countries – three communist and four Western capitalist – set out to jointly forge a rescue plan for the Baltic Sea. That was almost 50 years ago. Much research was done during this period under the auspices of HELCOM, many papers were written, and numerous measures were initiated and monitored. The record, however, is mixed at best. There are good things to report: Seal populations, for example, have recovered. Grey seals, Germany's largest free-living predators, weighing up to 300 kilograms and measuring 2.50 meters in length, are once again lolling about on the sandbanks in Wismar Bay. Many seabirds, such as guillemots, are also doing better. Nevertheless, it turns out that cleaning up a sea is more costly than a river or a lake. The inland Baltic Sea holds 30,000 times more water than the Müritz, Germany's second largest lake after Lake Constance. To fill it, a river like the Oder would need about a thousand years. Managing such a water body ecologically is a gigantic task. Even more so if it also requires international agreement. The most important goal on the way to a healthy Baltic Sea is the control of nutrient inputs. If large amounts of nitrogen and phosphorus continue to flow into the inland sea through more than 200 rivers, large algae blooms will grow, which in turn will lead to the expansion of the dead zone on the ocean floor. Over the decades, a massive cesspool has accumulated there. HELCOM Executive Secretary Strempel is proud to have stemmed the influx of nutrients. From peaks of up to 1 million tons of nitrogen and 70,000 tons of phosphorus, inputs have declined to the current level of about 600,000 tons of nitrogen and 25,000 tons of phosphorus per year. But that's not enough to reverse the trend. The anoxic dead zone continues to grow. Conditions in the Baltic Sea are still a long way from pre-industrial levels, when inputs were less than half of those today. The cleanup is complicated by the fact that any pollutants that enter the inland sea remain there for many years. On average, it takes 30 years for them to be washed across the Kattegat into the North Sea. Phosphorus poses a particular problem: Large amounts of the element have been embedded in sediment during decades of uncritical over-fertilization. Phosphorus clean-up is thus proving to be a Sisyphean task: As soon as the concentration in the seawater drops somewhat, the contaminated material dissolves, causing phosphorus levels to rise again. It will take decades to erase the sins of the past. Susi, Florian and 14 other third graders from the Ostseeblick elementary school in Sassnitz on the island of Rügen had quite a bit going on this morning. They learned what living fossils, barbels and anadromous migratory fish are. Most importantly, they held live sturgeon in their hands. The children were able to touch the sharp-edged bone plates on the backs of the fish. They each lent a hand to lift their firm, strong bodies out of a large plastic tub. And they then let the creatures slide down a wooden chute from the pier of Sassnitz harbor into the Baltic Sea. The sturgeons quickly disappeared into the murky water and immediately set about digging at the bottom for snails, worms or crabs, as captured by WWF divers who filmed the event. With their pointed head, protruding mouth, four tactile barbels and five rows of bony plates, sturgeons have survived largely unchanged since the time of the dinosaurs. Some sturgeons are giants. The largest specimen ever caught was reportedly 7.2 meters long. The Baltic sturgeons that once lived in the Baltic Sea didn't grow to be quite as large, but they could reach four meters in length. The last specimen born in the wild was caught off Estonia in 1996. It was a female, 2.90 meters long and 136 kilograms. They extracted 15 kilograms of roe in its ovaries. Since then, the Baltic sturgeon has become extinct in the Baltic. Female sturgeon are still kept by the Mecklenburg-Western Pomerania State Research Institute (LFA) in Born on Germany's Darss peninsula. The spawn is then nurtured for release after one year, usually after they reach 50 to 70 centimeters (20 to 27 inches) in length, into the Oder River, the Szczecin Lagoon or, as in Sassnitz, directly into the Baltic Sea. At the same time, sturgeon breeders are shipping newly hatched animals to Poland and the Baltic States, as part of an action plan for the reintroduction of Baltic sturgeon set up by HELCOM that is slated to run until 2029. LFA researcher Stefanie Felsing, who organized the stocking measure in Sassnitz, is confident that it will be possible to reintroduce the fish to the Baltic Sea. She has already been contacted by fishermen who have caught some of the tagged creatures. The scientists implant acoustic transmitters in the abdominal cavity of larger specimens. Tracking stations have now been set up around Rügen, but also elsewhere in the Baltic – near Bornholm, for example. This makes it possible to better understand how the reintroduced species reacquire their former habitats. However, the program suffered a major setback last year. The problem is that the Baltic sturgeon is an anadromous migratory fish, meaning it leaves the sea to reproduce and swims up streams, including the Oder River, in search of spawning grounds. But the Oder was hit by a catastrophic fish die-out last summer. The toxic water alga Prymnesium parvum had spread. Because of the low water level, the high temperatures and, especially, the high salinity in the Oder River, the algae found ideal conditions to grow. Hundreds of tons of dead fish were removed from the river, including dozens of sturgeon. In two nurseries operated along the Oder, almost all the offspring were destroyed. It also looks like the disaster could repeat itself in the future. The toxic algae is lurking in the sediment, waiting for favorable conditions. And those could be coming: Climate change is causing heat and droughts, and the salt comes from Polish coal mining. So far, though, the Poles have also shown little understanding for the issue. Instead of addressing the cause of the disaster, they are trying to fight the algae with hydrogen peroxide. Plans are also underway in Poland to expand the river's course. When this occurs, the speed of the flow increases, and many of the calm gravel beds that sturgeon need to spawn will disappear. Perhaps there is no longer a place for the sturgeon, these primordial creatures, in this man-made world. Perhaps the project will fail, and the stench of rot that hung over the floodplains of the Lower Oder Valley National Park last summer will become a portent of the Baltic's inexorable decline. Or perhaps the tough negotiations currently being conducted by the German and Polish governments will be prove fruitful in the end. And maybe it will be possible to reintroduce the Baltic Sea's largest fish into the ecosystem after all, so that some of the animals released into the open sea by the third-grade students will find their way to a spawning ground in the Oder, Vistula or Memel rivers in 15 years' time, when they are sexually mature. Living fossils could then become a symbol for a Baltic Sea that is getting healthier. Then, 50 years from now, the children will be able to remember that they helped save these giants from extinction. © 2023 Der Spiegel. Distributed by The New York Times Licensing Group. Read the original article at Der Spiegel.