What causes blue-green algae? Since the 40th century, the supply of the major nutrients nitrogen and phosphorus increased manifold, which has caused extensive ecological changes, mostly as a consequence of human activities around the Baltic Sea. An industrialized agriculture and inadequate wastewater treatment are two major causes of eutrophication, as we see the results of each summer by the bloom of 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. |
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