rehevissä

Rehevissä is a term used in Finnish environmental science and ecology to describe an over-enriched state of an aquatic ecosystem, particularly lakes and coastal waters. This eutrophication process is characterized by an excessive accumulation of nutrients, primarily phosphorus and nitrogen, which fuels the rapid growth of algae and aquatic plants. These blooms can drastically alter the water's physical and chemical properties, leading to a decline in biodiversity and overall ecosystem health.

The increase in primary productivity due to abundant nutrients results in dense algal blooms that can cover the water surface. This reduces light penetration, hindering the growth of submerged aquatic vegetation. When these blooms eventually die and decompose, the process consumes large amounts of dissolved oxygen in the water. This oxygen depletion, or hypoxia, can create conditions that are lethal to fish and other aquatic organisms, leading to fish kills and a shift in the species composition towards those tolerant of low oxygen levels.

Rehevissä conditions are often caused by human activities, such as agricultural runoff containing fertilizers and animal waste, as well as untreated sewage discharge and industrial wastewater. Natural factors can also contribute, but anthropogenic sources are usually the dominant drivers of severe eutrophication. The consequences of rehevissä extend beyond the immediate aquatic environment, impacting recreational activities, fisheries, and the aesthetic value of water bodies. Management strategies focus on reducing nutrient inputs from various sources, including improved wastewater treatment, sustainable agricultural practices, and land-use planning.