Image shows the exposed litoral zone after water level regulation in Mjøsa, one of Norway's largest regulatory reservoirs. Photo: Knut Andreas Eikland.

More flexible production of hydropower will cause the water level in the reservoirs to change more strongly and faster. In many cases, this has proven to be at the expense of the environment and the organisms in the reservoirs. Environmental DNA makes it possible to look for microscopic traces in nature to find out which species live there. It opens the door to obtaining more knowledge also about the smallest species – the meiofauna, which consists of invertebrates smaller than 1 millimeter and single-celled organisms.

Affects the fish's nutrition

– The meiofauna affects the nutritional basis of fish and larger invertebrates in lakes. Therefore, it is important to include these smallest species in studies and monitoring of hydropower reservoirs. To put it simply; better knowledge of the ecosystem provides better opportunities for sustainable use of natural resources, says researcher Markus Majaneva.

In a pilot study in HydroCen, the researcher from the Norwegian Institute for Natural Research (NINA) has used environmental DNA to map which species are found in a small selection of hydropower reservoirs. The purpose has been to see whether the regulation of the water level in the reservoirs affects species diversity, compared to the diversity in unregulated lakes in the same area.

The water is regulated according to the market

Most of the water reservoirs in Norway are natural lakes, but the water level is regulated to allow the power producers to control production according to the market. This flexibility in power production leads to more frequent, larger and faster changes in the water level compared to the natural variations.

– Previous studies have shown that larger benthic animals, such as insects, molluscs and crayfish, are negatively affected by these changes, but we know little about the effect they have on the smallest organisms. Results from the pilot study will show how species diversity in the meiofauna is affected by the regulation of the water level, says Majaneva.

The meiofauna consists of a number of tiny organisms that cannot be seen with the naked eye. Some of these are A. Rotifers (Rotifera) Luo Y, Segers H, B. Flatworm (Turbellaria) Eduard Solà, C. Tardigrades/ water bears (Tardigrada) Willow Willow Gabriel, Goldstein Lab, D. Gastrotrich (Gastrotricha) by Giuseppe Vago, E. Roundworm (Nematoda) by Bob Goldstein. 

They are small, but there are many

These small organisms consist of rotifers, crustaceans, water fleas, nematodes and all single-celled organisms. They are a group with many species that are often very numerous and play an important role in the food web of the ecosystem in the reservoirs. Because of their size, it has been difficult to identify species and monitor them effectively.

Flexible operation of hydropower plants gives increased profit to the hydropower industry, but flexibility must be weighed against negative effects on the environment. With more knowledge, the industry can adjust its operating patterns, so that flexible operation has a lower environmental footprint. DNA-based identification of species that are difficult to recognize in other ways makes it possible to map and monitor these species as well. This means that we can get a holistic view of the status of an ecosystem, for example a reservoir, or measure total species diversity before and after changes in the operation of a reservoir.