What impact does didymo have on freshwater ecosystems?

Didymo, or Didymosphenia geminata, is a type of algae often referred to as "rock snot" due to its filamentous texture. Its presence in freshwater ecosystems can significantly reduce biodiversity. This occurs because didymo can form dense mats on the substrate of rivers and streams, which smother native aquatic plants and disrupt habitats for various species.

When didymo proliferates, it can outcompete other algae and aquatic plants for space and resources, leading to a decline in species that rely on those habitats and food sources. The dominance of didymo can alter the composition of the ecosystem, negatively affecting overall biodiversity as fewer species are able to thrive in environments overtaken by this algae. The shift in species composition can have cascading effects throughout the food web, impacting fish populations and other organisms that depend on a diverse range of species for survival. Thus, the impact of didymo is primarily detrimental to the ecosystem, supporting the assertion that it reduces biodiversity.