Diversity of littoral zoobenthos in Lake Arakhley (Transbaikalia) during the arid phase

There is little data available on the zoobenthos of the Baikal region’s eastern periphery water bodies in low-water years. The taxonomic diversity of zoobenthos of the littoral zone of a deep lake (Arakhley, Transbaikalia) was studied in an extremely low-water year, 2017. The zoobenthos of the lake littoral zone was represented by 44 taxa. Chironomids accounted for 41% of the zoobenthos taxonomic diversity, 14% each – gastropods and leeches. The taxonomic diversity of the littoral zoobenthos in different parts of the lake varied from 19 to 24 taxa and averaged 22.3 ± 1.97 taxa. The relationship between taxonomic diversity and depth in Lake Arakhley is described by polynomial dependence. Deviations from the relationship identified at the periphery of vegetation thickets were due to the ecotone effect. Obtained data shows the state of zoobenthos taxonomic diversity under conditions of climate aridization and the reduction of littoral sandy habitats.

Do abundance and percentage of dipteran larvae and Oligochaeta indicate low water quality in streams and lake littoral?

The presence of chironomids and/or oligochaetes is generally considered to be an indication of poor status of freshwater. Non-chironomid dipterans show unclear trends. The abundance and percentage of these groups are rarely used as potential indicators. We attempted to determine whether these metrics reveal freshwater quality in lowland streams and lake littoral (Northern Europe, Baltic ecoregion, Estonia). The water quality was assessed based either on the water itself or on macroinvertebrates, fish, macrophytes, phytobenthos (in streams only) and/or phytoplankton (in lakes only). As expected, the high abundance and high percentage of chironomids and ceratopogonids indicated low quality of water in lakes. The high percentage of chironomids indicated low water quality also in streams. The high percentage of oligochaetes indicated low water quality in lakes. However, their high abundance (but not the percentage) was unexpectedly a symptom of high water quality in streams and to a lesser extent in lakes. In these cases, oligochaetes were represented by rheophilic, rather than saprophilic species. The abundance of simuliids (but not the percentage) and the richness of dipteran families indicated high water quality in streams. We suggest that the obtained results will allow better use of the indicative potential of freshwater macroinvertebrates.

Diatom biodiversity in the lake littoral of Rara Lake, a high altitude lake in the Himalaya of western Nepal

Diatoms were investigated in the littoral of Rara Lake, Nepal, to investigate the impact of land use, substratum type and season. Species composition and diversity differed between areas, seasons and between stones, sediment and macrophytes. Both communities on stones and on sediment differed between the settlement and forested areas, but communities on stones showed the greatest differentiation between land use types.

Kolme kertomusta järviemme tilasta

Finland is officially marketed as a land of a thousand clean lakes, but people’s concerns on negative trends is common. We used questionnaires and interviews to gather information on people’s experiences on how lakes have been changed, and compared the experiences with limnological research results and administrative lake classifications. Both human observations and limnological evidence detected negative changes in lake ecosystem quality during the past 30-50 years, whereas the administrative lake classification considered lakes to be mainly in good/excellent quality. In addition, small lakes with severe ecosystem changes reported by people, were seldom covered by classification. People’s observations and limnological measurements revealed independent and identical information on the trends in water quality, whereas much of the official lake classification is based on inadequate data and lack of observations on lake littoral areas. Thus, we suggest that people’s everyday experiences should be collected and analyzed more systematically in lake quality assessment processes.