The State of the Lake-river System Affected By Mineral Production

The current state of four water bodies in the upper and middle reaches of the River Kenti system, Western Karelia, affected by long-term industrial potassium-sulphate pollution, is assessed. The upper water body of the system, Lake Kostomukshskoye, is supplied by waste water from an iron mining concentration plant. Lakes Okunevoye, Poppalijärvi and Koivas are located downstream. Analysis of some hydrochemical indices and phyto- and zooplankton communities has shown that as the distance from the pollution source increases, the hydrological regime is stabilized, species diversity increases and the quantitative indices of the biotic constituent of the lake-river system grow. For example, the total mineralization value decreases from 632 дo 45 mg/l, the concentrations of major polluting agents, such as K+ and Na+ ions, decline by an average of two orders of magnitude and the medium reaction passes from alkaline (pН 7.7) to neutral (pН 6.8). The species composition of the phytoplankton varies from 18 to 23 species of six 6 divisions. The number of zooplankton taxa increases from 15 to 24 and average quantitative indices grow from 0.048 g/m3 (1.1 thousand individuals/m3) to 0.368 g/m3 (10.3 thousand individuals/m3), respectively. The data obtained were compared with earlier results

Contribution of the Baikal Amphipod to the Feeding Pattern of Perch in the Littoral Zone of Lake Onega

Abstract. The seasonal feeding pattern of juvenile perch in Petrozavodsk Bay of Lake Onega was studied. It was shown that in the fourth to sixth years of their life, a benthic type of feeding predominates. The fish that inhabit the littoral zone feed actively on the Baikal amphipod, a new food item. During the summer-autumn season, the colonizer accounts for over 50% of the biomass in the stomach of juvenile perch. The invasion of Lake Onega by the Baikal amphipod has thus led to changes in the structure of littoral communities and the availability of a new food item for the fish. Considering the resistance of the Baikal amphipod to unfavorable environmental factors, it is important to study its spatial expansion and the possible penetration of this amphipod via tributaries to other water bodies in the Lake Onega Lake catchment area. Keywords: freshwater ecosystem, perch, trophic interactions, Baikal amphipo

The impact of fish farming on the Tarasmozero Lake ecosystem, Onega Lake basin

The Tarasmozero Lake ecosystem (Onega Lake basin), affected by fish farming was assessed prior to and after the construction of a rainbow trout farm. Lake Tarasmozero receives waste water from the farm. The results of our studies show that when the farm began operating, phosphorus and nitrogen concentrations in the water have increased, affecting aquatic organisms and their environment. It was shown that phytoplankton is now dominated by diatoms, zooplankton species, characteristic of eutrophic water bodies, have appeared, and amphipods now make up the bulk of zoobenthos’ biomass. This evidence indicates that Lake Tarasmozero gradually passes from an oligotrophic type to a mesotrophic type

Contribution of the Baikal Amphipod to the Feeding Pattern of Perch in the Littoral Zone of Lake Onega

. The seasonal feeding pattern of juvenile perch in Petrozavodsk Bay of Lake Onega was studied. It was shown that in the fourth to sixth years of their life, a benthic type of feeding predominates. The fish that inhabit the littoral zone feed actively on the Baikal amphipod, a new food item. During the summer-autumn season, the colonizer accounts for over 50% of the biomass in the stomach of juvenile perch. The invasion of Lake Onega by the Baikal amphipod has thus led to changes in the structure of littoral communities and the availability of a new food item for the fish. Considering the resistance of the Baikal amphipod to unfavorable environmental factors, it is important to study its spatial expansion and the possible penetration of this amphipod via tributaries to other water bodies in the Lake Onega Lake catchment area. Keywords: freshwater ecosystem, perch, trophic interactions, Baikal amphipo