rehevöitymisessä

Rehevöityminen, often translated as eutrophication, is a process where a body of water becomes overly enriched with nutrients, primarily nitrogen and phosphorus. This excess nutrient load stimulates the excessive growth of algae and aquatic plants. When these organisms die, their decomposition by bacteria consumes large amounts of dissolved oxygen in the water.

The primary sources of nutrient enrichment are often anthropogenic, including agricultural runoff containing fertilizers, untreated or inadequately treated sewage, and industrial wastewater. Natural processes can also contribute to nutrient loading, but human activities have significantly accelerated the rate of eutrophication in many aquatic ecosystems worldwide.

The consequences of eutrophication can be severe. Reduced oxygen levels, known as hypoxia or anoxia, can lead to the death of fish and other aquatic organisms, creating "dead zones." The dense algal blooms can block sunlight from reaching submerged vegetation, hindering its growth. Furthermore, some algal blooms, termed harmful algal blooms (HABs), can produce toxins that are dangerous to wildlife, livestock, and humans.

Mitigation strategies for eutrophication focus on reducing nutrient inputs. This includes improving wastewater treatment, implementing sustainable agricultural practices like reduced fertilizer use and better manure management, and controlling urban runoff. Restoration efforts can also involve removing excess nutrients or restoring habitats that help filter water.