Особливості фітопланктону водойм міських лісопаркових зон

Анотація

PHYTOPLANKTON SPECIFICS IN URBAN PARKLAND WATER-BODIES

V. I. Shcherbak, O. V. Kravtsova

Forest-park areas used by society for recreational purposes are an integral part of urban landscapes. Diverse aquatic ecosystems of both natural and artificial origin are important elements of these areas. But at the same time, most of them have various degrees of human impact, in particular, caused by recreation, amateur fishing, green tourism, etc.

Phytoplankton is the main biotic component of these aquatic ecosystems, which, accordingly, is a representative biological indicator of their present state, water quality and anthropogenic load rating.

The purpose of the study was to determine the specifics of qualitative, quantitative and informational diversity of phytoplankton, its dominant complex, water quality, to conduct bioindicative analysis of water-bodies located in parkland areas of some Ukrainian cities: Kyiv and Zhytomyr.

The material of the study included phytoplankton of Lake Babyne, located in the woodland park of Trukhanov island of Kyiv, and the pond of the botanical garden of the Zhytomyr National Agroecological University (ZNAEU).

Investigation of qualitative and quantitative diversity of phytoplankton of these water-bodies was conducted during vegetation seasons (spring-autumn) 2016-2017.

Sampling of algae was carried out at the fixed sites twice a month. Phytoplankton samples were conserved, concentrated, and processed in the laboratory by generally accepted methods in hydrobiology with allocation of dominant species complex and calculation of information diversity with using Shannon index. We measured water temperature, dissolved oxygen content, pH, and mineralization.

Significant differences were found between the content of oxygen dissolved in water and the saturation of water with oxygen in the water-bodies under study. Thus, the oxygen content in Babyne lake was within the range of 1,5-12,8 mg O₂/dm³ (9,2 at an average), and in the botanical garden – 4,3-19,0 (11,8) mg O₂/dm³. Water saturation with oxygen is 12,1-141,6% (100,9%) and 58,3-211,1% (128,0%), respectively.

The mineralization of water was much lower in Babyne Lake, its value ranged from 134 to 234 ppm (an average of 171 ppm). In the pond of the botanical garden it was 167 - 421 (296) ppm.

262 species of algae, including 268 infraspecies taxa were identified in phytoplankton of the water-bodies under study. We found 8 divisions, 13 classes, 31 orders, 50 families and 103 genera, among which Bacillariophyta, Chlorophyta and Euglenophyta dominated. The phytoplankton of Lake Babyne was represented by 188 species (189 infraspecies taxa), and of the pond in the botanical garden of ZNAEU - 164 species (167 inraspecies taxa).

The leading taxa at the class level were Euglenophyceae, Bacillariophyceae, Chlorophyceae and Zygnematophyceae, of the orders Euglenales, Sphaeropleales, Desmidiales, Naviculales and Euglenales. Among the leading genera one should note: Trachelomonas Ehrenb., Lepocinclis Perty, Navicula Bory, Desmodesmus (Chodat) An et al., Staurastrum Meyen Emend. Pal-Mordv., Euglena Ehr., Cosmarium Corda ex Ralf, Pinnularia Ehrenb., Peridiniopsis Lemmerm.

The number of phytoplankton in the water-bodies during the spring-autumn period varied widely: in Babyne Lake from 0,32 to 10,67, and in the pond of the botanical garden - from 0,16 to 11,39 million cells / dm³.

Significant biomass maxima in Babyne Lake were not marked. Whereas in the phytoplankton of the pond in the botanical garden, biomass peaks in the spring (21,04-21,76 mg / dm³) were mainly due to the development of dinophyta, eugena and green algae. The peaks of phytoplankton development (biomass reaching 21,17-124,45 mg / dm³) were caused by vegetation of desmids in summer.

The bioindicative characteristics inherent to desmids make it possible to conclude that a significant portion of them in the phytoplankton of the botanical garden is an indicator of the water-body swamping.

The structure-forming units in formation of the number and biomass of phytoplankton were streptophyta, diatoms, green and eugena algae. The dominant complex (according to biomass of phytoplankton) was represented by dinophyta, diatoms, green and streptophyta algae. At the same time, the dominance of blue-green algae was characteristic of Babyne Lake, and Euglenophyta - for a pond in the botanical garden of ZNAEU. There was a change in the complexes of dominant species of phytoplankton depending on the season during the studied period.

The informational diversity of phytoplankton calculated according to the Shannon index for both water-bodies varied within the range of 0,35-4,43 bits / s and did not differ significantly.

Saprobiological assessment of water quality showed the presence of insignificant organic contamination in the pond of the ZNAEU botanical garden. β-mezosaprobs dominated in the water-bodies according to the conducted bioindicative analysis. The water-bodies belong to the class of "moderately polluted" waters according to the index of saprophytics (2,03 ± 0,22 for Babine lake, 1,90 ± 0,05 for the pond in the botanical garden).

    Thus, the results of the research show that in the forest park areas both in a large city and a much smaller regional center, the phytoplankton of the water-bodies located there is characterized by high qualitative, quantitative and informational diversity and indicate low degree of organic pollution.

    We believe that formation of effective measures for protection of water objects located in forest park areas is an important direction for improving the ecological state of large cities of Ukraine and it will have a positive impact on the urban community.