övergödningen

Övergödningen, or eutrophication in English, is a process where a body of water becomes overly enriched with minerals and nutrients, primarily nitrogen and phosphorus. This enrichment leads to excessive growth of algae and aquatic plants. When these organisms die, their decomposition by bacteria consumes large amounts of dissolved oxygen in the water. This depletion of oxygen can create hypoxic (low oxygen) or anoxic (no oxygen) conditions, making it difficult or impossible for fish and other aquatic organisms to survive.

The primary sources of excess nutrients are often anthropogenic, meaning human-caused. Agricultural runoff carrying fertilizers and animal waste is a major contributor. Sewage treatment plants, even when functioning properly, can release nutrients. Industrial wastewater and stormwater runoff from urban areas also play a role. Natural sources, such as decaying organic matter and atmospheric deposition, also contribute but are typically less significant in causing widespread overgödning.

The consequences of övergödningen can be severe, including fish kills, loss of biodiversity, and shifts in aquatic ecosystems. Algal blooms, especially those caused by cyanobacteria (blue-green algae), can produce toxins harmful to wildlife and humans. The aesthetic quality of lakes and rivers can also be degraded, impacting tourism and recreation. Addressing övergödningen typically involves reducing nutrient inputs from all sources through improved agricultural practices, enhanced wastewater treatment, and better land management.