“Eutrophication of the Baltic Sea remains the greatest threat to its ecosystems,” say ecologists. Microplastic pollution is also becoming increasingly significant, and the upcoming challenges associated with the construction and operation of offshore wind farms are expected. On one hand, there is the emission of plastic pollutants and, on the other, noise pollution that negatively impacts organisms reliant on echolocation. The Baltic Sea’s porpoise population, already critically endangered with only about half a thousand individuals remaining, is particularly vulnerable to these threats.
The Baltic Sea’s susceptibility to external factors stems primarily from its shallow depth. Its average depth is 52 m, compared to the Adriatic Sea’s average depth of 252 m and the Black Sea’s depth of 1,253 m. The Baltic Sea is also low in salinity and home to over 80 million people residing in its catchment area.
“The most serious threat is still eutrophication, or overfertilization of the Baltic waters, caused by farmers’ excessive use of fertilizers, which then wash into the sea,” says Dr. Andrzej Ginalski, head of the marine team at the WWF Poland Foundation, in an interview with Newseria.
Eutrophication occurs as a result of excessive amounts of nitrogen and phosphorus in the water, sourced from sewage, industry, air deposition, and agriculture. The primary sources of biogenic substances to the Baltic Sea are rivers, particularly those located in Poland. In 2020, during the “Our Baltic” conference, a declaration was signed by the ministers of the Baltic Sea countries pledging to a greater involvement of each country in actions for marine environment protection. This included funding to improve water conditions from the EU Common Agricultural Policy, and reviewing programs to effectively reduce the flow of nitrates from agricultural sources.
“But there are also a number of other threats, including overfishing of commercially caught fish, bycatch, which is the accidental entanglement of protected species in nets, and underwater noise pollution emitted by various vessels,” lists Dr. Andrzej Ginalski.
According to WWF Poland’s report last year, the Baltic Sea is one of the most trafficked seas in the world, and maritime traffic is growing. The main sources of pollution are the emission of exhaust gases and dusts into the air and the discharge of sewage from passenger ships, contributing to the Baltic’s eutrophication. Shipping is also the most frequent source of underwater noise pollution, produced by passenger ferries, commercial or fishing fleets, and motor-powered recreational vessels. This pollution is particularly important, as it is most often generated in shallow coastal waters, or near the natural habitats of critically endangered porpoises.
“Efforts made so far to protect seas and oceans are bearing fruit. An example can be the decreasing eutrophication of the Baltic, mainly thanks to the mass construction of sewage treatment plants, among others, on Polish rivers,” says the head of the Marine Team at the WWF Poland Foundation. “However, we observe various other pressures that did not exist before. Current actions are valid, but they are insufficient. We also need new actions in the face of new threats.”
One of these is wind power plants that will be built in the Baltic Sea in the coming years. The companies building them assure that they limit the interference of both the process and the power plants themselves in the environment, but the challenge remains.
“Wind farms are desired since they do not emit carbon dioxide. However, they can cause noise and vibrations that may be felt by marine mammals. We have the only whale representative in the Baltic Sea, the porpoise, which uses echolocation to navigate space. Excessive underwater noise causes it to lose its way. An insoluble problem, which is still little talked about, is the plastic from wind power plants themselves entering the sea. A direct example of the negative impact of wind farms is the physical death of birds and bats that collide with the turbine blades,” says Dr. Andrzej Ginalski.
Increasing plastic pollution is also a significant threat to Baltic ecosystems. The concern is less with large plastics and more with microplastics, which are very difficult to filter out of the water.
“Perhaps macroplastic is more newsworthy, there are already known locations in the oceans with so-called large garbage islands where human-emitted waste accumulates over large areas, but these are wastes that are relatively easy to fish out and neutralize. The much more difficult problem is microplastic, because its particles are much harder to fish out. We already know that they are absorbed by organisms and scientists found it practically in all organisms, including the human body. This means that humans, being the last link in the food chain, are also exposed,” concludes the WWF Poland expert.
According to UN Trade and Development Conference data, out of the 369 million tons of plastic waste produced per year, about 11 million tons end up in the oceans. If the trend continues, this number will triple by 2040. Analyses by the Marine Institute – National Research Institute indicate that fibers and microplastics classified as plastic fragments are the dominant types of microplastics in sediments along the Polish coast.
WWF points out that plastic represents about 70% of all waste in the Baltic Sea. The most common garbage found on coastal beaches includes food packaging, bottles, caps, various plastic elements, as well as industrial waste such as foils and tapes. Another source of plastic and deadly marine threat is ghost nets, in which animals entangle themselves. Moreover, the Baltic holds approximately 50,000 tons of ammunition containing toxic combat agents, sunk after World War II.
