Extraction of nutrients in situ from the sea
The eutrophication is one of the most serious problems of the Baltic Sea. There are two main nutrients causing eutrophication, nitrogen (N) and phosphorous (P). The Baltic Sea now contains four times as much nitrogen and eight times as much phosphorus as it did in the early 1900s. The eutrophication leads to algal blooms, which in turn leads to reduced amounts of dissolved oxygen in the water with dead sea beds as a result. Once the unwanted nutrients have ended up in the sea, there are ways of extracting them. Although it is difficult to do this in any significant scale, physical filtration and extraction as well as mussel farming can decrease the local effects of eutrophication.
This section is closely related to the oil spill section, in which methods for extracting algae can be found.