№ 5 (2021)
Статьи
Influence of environmental factors onto reproductive characteristics of Daphnia galeata from Lake Baikal
Аннотация
The influence of various factors onto the reproductive characteristics of the cladoceran Daphnia galeata Sars, 1863 Lake Baikal was studied. With an increase in the concentration of available feed, the size of the body, average fertility, the size of the brood and the proportion of egg-bearing females increase. At high temperatures, significantly greater fecundity and the proportion of egg-bearing females were noted; other features did not change significantly with temperature increase. Under the conditions of strong turbulence, the fertility and the proportion of egg-bearing females are lower than under the conditions of low turbulence. The presence of a predator with an increase in the concentration of feed and temperature results in the decrease in the size of crustaceans and in the increase of the proportion of egg-bearing females.
1175-1181
Quantitative development and structure of zoobenthos in channels on the left margin of the Selenga River delta
Аннотация
There are only a few studies on zoobenthos in the delta of the Selenga River located at the junction of Lake Baikal and its largest tributary. The present work provides the results of research on zoobenthos in the southern (left) Selenga delta channels in 2002. Baikal amphipods and bivalves are widespread up to the upper delta. The direction and velocity of the water flow in the delta induced change of a river zoobenthos complex for a limnophilous one. Baikal amphipods are responsible for high quantitative indicators of zoobenthos in the southern channels of the delta. Low parameters of quantitative development of zoobenthos were registered during summertime. Organic matter from the catchment area of the Selenga River provides trophic resources for zoobenthos. Amphipods, bivalves and oligochaetes are involved in the transformations of suspended, sedimented and buried fractions of allochthonous matter. The authors obtained evidence on maintenance of the principal properties of the delta ecosystem as an ecotone at the time of research.
1182-1185
Water quality and zooplankton community of the Eme River, Umuahia, Southeast Nigeria
Аннотация
Aquatic ecosystems and biota are often adversely affected by anthropogenic activities. Consequently, zooplanktons have been used to monitor anthropogenic impacts because of their sensitivity to their environment. Water quality and zooplankton community of the Eme River, Umuahia, was assessed between December 2017 and November 2018. The study was carried out in six stations in relation to human activities. Human activities in the watershed were dominated by sand mining. A quantitative filtration method was used for the zooplankton sample collection while standard sample collection and analytical methods were used for the water samples. The zooplankton species recorded were 27 while the most abundant zooplankton group was Rotifera. A known pollution indicator, Daphnia pulex, had the highest number of individuals. The effects of human activities in the watershed were reflected in the results of some of the physicochemical parameters of the river. The zooplankton assemblage and community structure also reflected the effects of human activities in the river. Combined effects of human activities and season contributed to the relatively low zooplankton abundance recorded particularly in some downstream stations. The impacts of sand mining on water quality and zooplankton were more remarkable in the downstream stations (4 – 6) where the activity was intense while a large number of children swimming and related activities during the dry season had some impacts in station 1. The dominance of indicator and tolerant species indicated that the river was undergoing eutrophication. Sand mining among other observed anthropogenic activities was a major contributor to the nutrient enrichment in the river. The major water quality parameters influencing the zooplankton community structure was revealed by canonical correspondence analysis.
1186-1194