ARKHANGELSK, March 5. /TASS/. Scientists of the Laverov Federal Research Center for Integrated Arctic Studies (Arkhangelsk) of the Russian Academy of Sciences' Urals Branch will study for the first time hydro-chemical parameters of the Karasozero lake system in the Arkhangelsk Region’s Pinega District, senior researcher at the Center’s eco-analytical research laboratory Ksenia Titova told TASS.

"The Pinega District is interesting due to the karst rocks that rise to the surface. When they are eroded by precipitation, chemical compounds from gypsum and anhydrite are getting into the lakes. This process changes actively the local reservoirs' water mineralization and composition. This explains the district’s calcium sulfate waters with very high mineralization. These are purely natural processes caused by the geological structures. The Karasozero system is an interesting model object: reservoirs with this type of water are rare. The Arkhangelsk Region is known for typically bicarbonate-calcium reservoirs," she explained.

The research includes studying the chemical composition of waters, identification of factors influencing the chemical composition formation, and assessment of the reservoirs' environmental conditions. Scientists plan seasonal sampling of water and sediments. Earlier, the Karasozero lakes were studied mainly from the point of view of geology and biodiversity.

Hydrogen sulfide and fish

In anaerobic conditions, for example, when oxygen levels drop under ice, sulfates coming from karst rocks can transform into hydrogen sulfide, scientists say. Hydrogen sulfide is harmful to fish. Local residents note that when hydrogen sulfide accumulates in shallow lakes, fish would migrate to neighboring reservoirs through a system of rivers and streams.

Scientists have found a significant content of hydrogen sulfide in collected winter samples. Additionally, the Karasozero system’s waters have low levels of organic matter, and nevertheless, the Pinega District’s lake system is considered rich in fish.

Scientists recommend that fishermen make not one, but, if possible, several ice holes in winter fishing areas so that more oxygen could get into the lake.