Water is the recipient of pollutants and environmental impacts are thus often first noticed on life in water. There are several examples of this in the Baltic Sea. One example is the effect of PCBs. During the 1970s and 80s the Grey seal of the Baltic Sea were threatened by extinction. It was show that elevated levels of PCB in the animals made them sterile. It was also shown that the PCB came from the fish that the seal eat. The same effect could be expected also to influence also humans. Thus PCB was banned and the concentrations in the seals have since lowered and the seal population increased.
The brackish water in the Baltic Sea has been there for about 3000 year only. The brackish water is a hinder for many both marine and fresh water species so the Baltic Sea is thus relatively species poor. On the other hand those species that manage to survive in the environment are often found in great numbers. This makes the Baltic Sea less robust as damaged or extinct species may not be replaced by other species.
The Baltic Sea has been studied for a long time. These records allow us to extensively study its ecology. The effects of excess nutrients, excess fertilizers and exhaust of power production and car traffic have been studied carefully.
Fishing in the Baltic Sea has always been important. However, today the catches of salmon and cod have decreased dramatically due to over fishing. the means to improve the situation includes both regulation and environmental protection.
Bird life in the Baltic Sea rich. There is a larger share than anywhere else of migrating birds. Some birds use the basin as a summer dwelling ground while others use the ice free waters of the southern Baltic Sea as their over wintering refuge.
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