The Baltic Sea is often called the world's sweetest sea. Marine salinity ranges from 1 ‰ in the northern part up to 6-8 ‰ in the central part. In 40 - 70 m depth the salinity is 15-20 ‰. By comparison, the world ocean average salinity is 35 ‰. This makes the Baltic Sea so unique.

 The Baltic Sea waters are characterized by the salinity decreases with increasing distance from the North Sea. At the Danish coast of the Baltic Sea salinity is similar to the salinity of the North, while the Gulf of Bothnia in the northern part of the water is no longer taste the salt and the lives of freshwater species. Thanks to the marine nature of the living species in other seas would be hard to find, for example porpoises. The Baltic Sea is almost completely closed and there insufflate mostly freshwater from rivers and precipitation. The relatively small water circulation to the Baltic Sea are particularly at the risk. For more than a quarter, or 100 000 km ² has no higher any of life forms - it is due to the fact that the bottom water immiscible layer above the existing water table and there is no oxygen. This part of living only in anaerobic organisms.

However, not only in a small water circulation is attributable to the fact that 100 000 km ² dont have higher life forms. Nordic and Baltic region is suitable for agricultural development. To improve the yield, farmers are using fertilizers and reaching groundwater often flows into rivers, lakes and seas. The high in phosphorus, which flow into the sea, is to blame for the fact that for several years cyanobacteria in the Baltic Sea is a particularly suitable place for the flowering stage. On algal developing factors are considered water temperature above 16 degrees Celsius, stagnant water, no wind and a high time of organic matter and high phosphorus concentrations. Although cyanobacteria must be located in the Baltic Sea, the flowering intensity has reached a critical threshold.

 At the end of July cyanobacterial bloom begins to step up to the Sweden - large areas with flowering cyanobacteria was initially seen at the island of Gotland and Stockholm archipelago. However, according to WWF provided information, cyanobacteria is covered 90% of the Baltic Sea surface, or nearly 377,000 square km wide area. Cyanobacteria now stretches from the Finnish coast of the Curonian dunes to the long held by Germany, Rugen Island and is clearly visible from space.

What is the direct impact of cyanobacteria in the Baltic Sea? As I said that one fourth of the Baltic Sea is the so-called dead zone. Cyanobacteria do not allow plants access to sunlight for photosynthesis to help begin to grow.  After swimming at the place where cyanobacteria can be found, the body can occur in skin redness and rashes can be symptoms of eye irritation in the lining, and a general weakness. At a later time may develop health problems such as nausea, vomiting, abdominal pain, diarrhea, spontaneous muscle contractions, dermatitis, minor skin burns and allergic nature of the disease.  In water, which detected the presence of potentially toxic algae, it is prohibited to swim, to engage in water sports, during which the human body can be direct contact with the water to catch fish, as well as the use of water for livestock watering. I should also mention that after blooming cyanobacteria sink the sea bed and increase the dead zone areas, especially liberates hydrogen sulfide. The rapid emergence of these areas affects fish populations, thus, the fish quota quantity.

What causes blue-green algae?

  More nutrients means that plants grow better. Phytoplankton and filamentous algae benefit under these conditions. Too much   phytoplankton in the water makes the water muddily so that light cannot reach the seabed. Consequently, plants cannot live as deep as in   clear water.

  The increased amount of phytoplankton, sooner or later fall to the seabed and are broken down by animals and bacteria that consume oxygen.

  The lack of oxygen release phosphorus to the water, that has been stored in bottom sediments, while the nitrogen is converted to nitrogen gas and disappears into the air. The large excess of phosphorus in water favors cyanobacteria - or blue-green algae, which they also called.

  The blue-green algae have a unique ability to pick up nitrogen gas. This means both that the nitrogen will return to the water body and the oxygen consumption of the bottoms will be even greater since most of these blooms fall to the seabed. Over shorter or longer periods, there will be a lack of oxygen in coastal areas and in the depths of the open sea.  All the animals that live there will die or flee.

Latvian Health Inspection specialist Normunds Kadiķis, at his last interview said that not all cyanobacteria are toxic to humans, animals and nature. However, we must not gamble, so it is necessary to define these areas and to monitor water quality in inland waters in the Baltic Sea overall.

The policy of Baltic Sea

According to World Wildlife Fund the first what we need is:

• First, much closer monitoring of the subsidies paid to European Union (EU) common agricultural policy. Creation of subsidies regulation and monitoring, which could prevent the excessive use of fertilizers in agriculture, thus reducing the leakage, including into the sea. Partly, but very formal, it is done now. However, the results are far from the desired - the requirements are too low, the real-agricultural activities are not monitored and violations are not punished. This is an opportune moment to start solving the problem because the EU will shortly be made in agricultural policy review. 
• Second, the prime ministers of the Baltic Sea States has another opportunity to act in good of marine. Autumn 2007 was adopted in the Helsinki Commission (HELCOM) Baltic Sea Action Plan. It is designed to create a common platform to combat eutrophication in the Baltic Sea and other problems. But experience shows that the HELCOM Member States are lukewarm implementation of the joint commitment. Therefore, it is essential that all countries are involved in the Prime Ministers of the Baltic Sea Action Plan, ensuring the highest level of support the Ministry's activities. 
• Third, an effective way to control the use of minerals is taxation. Of tax revenues be returned to farmers to improve farming practices and environmental performance. Environmentally friendly agricultural practices to continue to develop and popularize the whole Baltic Sea region. Since some of the problems is not possible to resolve the individual farm level, the Government should take the initiative to promote better agricultural practices in the landscape level, such as wetlands, fresh water systems and other buffer restoration and creation. Buffer zone absorbs manure, halting its further Running, thus preserving the lakes, rivers and sea.

Also, HELCOM has estimated that the Baltic Sea water treatment cost three billion euros a year. Given that the EU Baltic Sea States farmers are paid annually to 11.6 billion, three billion is a tiny amount to save one of the world's most uniquely seas.

Photos and text of "What causes blue-green algae?' is from Baltic sea 2020.

Main picture from Ecoop