Leväkasu

Leväkasu is a Finnish term that broadly refers to the phenomenon of algal blooms occurring in bodies of water. These blooms are characterized by a rapid increase in the population of algae, often leading to a visible discoloration of the water, such as green, blue-green, or even reddish hues. The term can encompass both naturally occurring and human-induced algal blooms.

The primary cause of excessive algal growth, or eutrophication, is often an overabundance of nutrients, particularly nitrogen and phosphorus, entering the water. These nutrients can originate from various sources, including agricultural runoff containing fertilizers, wastewater treatment plant discharge, and industrial emissions. In natural conditions, a certain level of algal growth is normal and forms the base of the aquatic food web. However, when nutrient levels become too high, the algae multiply at an unsustainable rate.

Consequences of severe leväkasu can be detrimental to aquatic ecosystems. As the algae multiply, they can form thick mats that block sunlight from reaching submerged aquatic vegetation, hindering its growth. When the dense algal bloom eventually dies, its decomposition by bacteria consumes large amounts of dissolved oxygen in the water, creating hypoxic or anoxic conditions that can be fatal to fish and other aquatic organisms. Some types of algae can also produce toxins, posing risks to human and animal health if the water is consumed or comes into contact with skin.