Field observations, laboratory experiments and a literature survey were conducted to evaluate the habitat characteristics of Eurytemora lacustris (POPPE 1887), a freshwater calanoid copepod species. Combined effects of temperature and oxygen concentration in the deep water of thermally stratifying lakes seem to be the ultimate factors governing the occurrence of the species throughout its home-territory. E. lacustris is largely restricted to relatively deep lakes (>30 m) providing a hypolimnetic refuge characterised by low temperatures (<~10°C) and oxygenated water during summer. Therefore, although the species is spread over much of Europe it was only found in a small number of lakes. Long-term records in different lakes revealed E. lacustris to be perennial with relatively high biomasses occurring from May to September. During thermal stratification on average 87% of the nauplii and 72% of the copepodite biomass was found in hypolimnetic waters colder than 10°C. Diurnal vertical migration was observed for the copepodid stages, but the migration amplitude clearly decreased from May to September. The migration amplitude was significantly related to light intensity. According to its special habitat requirements, E. lacustris might be considered a glacial relict sensitive to temperature increase and oxygen depletion. IntroductionThe distribution of a given species within its home-territory largely depends on the species' ecological requirements and the extent to which these needs are satisfied by a certain biotope. As a result of the co-evolution between environment and biota, plants, animals and micro-organisms are restricted to particular geographical regions and habitats (ILLIES, 1971). Some species might be abundant in many places while others are rare and characterised by a scattered distribution (ILLIES, 1978). With respect to lakes, chemical and physical features of the habitat such as temperature, oxygen concentration and solar radiation are as important as biological factors like food supply and predation (THIENEMANN, 1928;LINDEMAN, 1942; STRAŠKRABA, 1980;ZARET, 1980). Eurytemora lacustris (POPPE, 1887), a calanoid freshwater copepod, can be found in lakes throughout an area reaching from the Boreal highlands of northern Norway south to the Black Sea and from the Central European lowlands to the eastern parts of the Caspian reInternat. Rev. Hydrobiol. 90
Investigating the mechanisms behind the impact of heavy metal pollution on aquatic ecosystems is urgently required. Due to increasing growth in the mining sector, pollution has become a serious threat to water resources and aquatic biodiversity and is causing unfavorable environmental changes and human health hazards. The aim of the present study was to investigate and assess the environmental risks of heavy metal pollution of river ecosystems in the Lake Sevan and Debed River catchment basins in Armenia, and a thorough study of their qualitative and quantitative parameters. Water samples were taken from the risky river sites of the Sevan and Debed basins in May and August 2013 and 2014. Investigations showed that due to mining and metallurgical industrial activities and the insufficient management of industrial waste and wastewater, the river ecosystems in these territories were exposed to heavy metal pollution, the degree of which in some sites of the Sotq, Masrik (Lake Sevan catchment basin), Debed, Alaverdi, Akhtala, and Chochkan (Debed River catchment basin) rivers may have posed health risks to aquatic life as well as to humans (at least in the case of river water used for drinking purposes). The results of a phytoplankton community study revealed that a decrease in the species diversity of planktonic algae in the investigated rivers was mainly conditioned by the impact of heavy metal pollution induced by mining and metallurgical industrial activities in the Lake Sevan and Debed River catchment basins.
Email address:lus-ham@yandex.ru (Hambaryan L. R.), marinen3@yahoo.com (Nalbandyan M. A.), ani-poghosyan@live.com (Poghosyan A. M.) To cite this article:Hambaryan L. R., Nalbandyan M. A., Poghosyan A. M. Vol. 4, No. 3-1, 2015, pp. 44-50. doi: 10.11648/j.ajep.s.2015040301.18 Abstract: This paper is related to the study of hydro chemical characteristics and the phytoplankton of the river Masrik. For planktonic study, algae were selected from 3 sampling sites: two from tributaries of the river and one from the river Masrik. Hydro chemical monitoring includes 9 sampling points. The study includes the spring of 2014 and the summer of 2013. According to the hydro chemical research of water, the pH ranged from 6.5-7.3. In 2014, the pH was lower compared with the spring of the previous year. Among tested anions, in some areas, relatively high level of sulfates were reached 80 -120 mg /L. Total hardness ranged from 0,6-5,6 mg-eqv /L, and the total mineralization -was ranged from 60 to 430 mg /L. Studies of heavy metals revealed a relatively high content of lead, nickel and chromium in water. Visual assessment revealed a significant organic pollution of Masrik river, which confirmed by high levels of BOD5 in water in 2014. In Masrik river mainly 3 groups of algae were detected: diatoms, green and blue-green. Dominant group was diatoms. Dominated types of algae were β-mezosaprobs (about 53%), which indicated the average level of organic pollution of the river. As a part of the green algae Spirogira sp. was found. The maximum number of phytoplankton in the investigated areas was 16,854,000 cells / L, and the biomass was 162g /m3, the minimum rates -respectively 464 000 cells /l in and 2.8 g/m3 for biomass. In water samples well developed whorls algae of the genus Chara were found, which presence indicates anthropogenic pollution. Thus, in a more acidic environment, the presence of high levels of organic pollution creates favorable conditions for the growth and development not only phytoplankton such as algae, but also for macrophytes, which indicates the reduction of ecological status of rivers.
A modern study of the Arpa River and its tributaries allows evaluating the ecological state of the ecosystem according to phytoplankton development indicators and comparing it with previous data. It is known that modified control of hydrosystems for hydropower stations changes quantitative and qualitative indicators of water, which increases anthropogenic impact on the diversity of hydrobionts. In order to mitigate the environmental risks and improve the ecosystem self-cleaning it is necessary to carry out continuous monitoring and rapid assessment of the change in the composition of microalgae indicators.
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