Species Diversity of the Dniester River Zooplankton Communities in 2013 – 2015

IX-th International Conference of Zoologists, 12-13 October 2016 207 SPECIES DIVERSITY OF THE DNIESTER RIVER ZOOPLANkTON COMMUNITIES IN 2013 – 2015 Olga Jurminskaia, Liubovi Lebedenco, Igor Subernetkii Institute of Zoology, Academy of Sciences of Moldova, Chisinau, Republic of Moldova [email protected] The aim of the work was to study the species diversity of zooplankton in the different sectors of the Dniester River within the boundaries of the Republic of Moldova. Sampling of zooplankton was carried out in the littoral zone of the river at a depth of 1.0 – 1.5 m. A total of 99 quantitative zooplankton samples were collected seasonally during 2013 - 2015 by filtering 100 liters of water through a plankton net (mesh size 55 μm) at 11 stations of the Dniester River and Dubossary reservoir: Naslavcea, Valcinet, Soroca, Camenca (Dniester River, medial sector), Erjovo, Goiani, Cocieri (Dubossa- ry reservoir), Vadul lui Voda, Varnita, Suclea, Palanca (lower sector of the Dniester River). The main taxonomic groups of zooplankton (Rotatoria, Copepoda, Cladocera) have been identified according to Kutikova (1970), Kutikova & Starobogatov (1977), Negrea (1983), Naberejnyi (1984), Tsalolihin (1994) and Alekseev (1995) with using a stereo zoom Discovery V8 ZEISS and a microscope Micmed-2 LOMO. Species diversity (SD) is one of the most important characteristics of biotic communities that reflect the complexity of its specific structure. Presently more than 30 different indices are proposed for evaluation of various aspects of diversity. The sim- plest indicator of α-diversity (species richness) is the total number of taxa (W), but its value depends on the sample size and number of samples. Nevertheless, indicator W can be suitable as SD index in cases the size and number of samples is the same for every sampling station, as it was in this study (fig. 1). Figure 1. The species richness of zooplankton (in 100 liters of water) along the Dniester River longitudinal profile: Ns – Naslavcea, Vc – Valcinet, Sr – Soroca, Cm – Camenca, Ej – Erjovo, Gn – Goiani, Cr – Cocieri, V-V – Vadul lui Voda, Vn – Varnita, Sc – Suclea, Pl – Palanca Sustainable use, protection of animal world and forest 208 management in the context of climate change The differences and similarities along a range of habitat can be assessed using β indexes: β-diversity or β-similarity. One of the common approaches to the assessment of β-diversity is a comparison of species composition in different communities: the smaller common species → the higher β-diversity → the lower β-similarity. The ob- tained lists of zooplankton taxa have been compared, and Sorensen similarity coefficient (Cs) has been calculated for: 1) the Dniester River medial sector and the Du- bossary reservoir; 2) the Dubossary reservoir and the lower sector; 3) the medial and the lower sectors of the river (Table 1). Table 1 Similarity matrix of the Dniester River different sectors based on zooplankton communities Year/ 2013 2014 2015 sector 1* 2 3 1 2 3 1 2 3 1 0.368 0.238 0.400 0.474 0.426 0.456 2 0.368 0.458 0.400 0.609 0.426 0.464 3 0.238 0.458 0.474 0.609 0.456 0.464 *1 – Dniester River medial sector, 2 – Dubossary reservoir, 3 – Dniester River lower sector Conclusions The total taxonomic spectrum of the Dniester River fluvial zooplankton (sampling 2013 – 2015) is represented by 92 taxa and 6 larval stages of copepods (nauplii and copepodids of suborders Cyclopoida, Calanoida and Harpacticoida). The significant variability of species richness has been recorded during these years, caused by the different habitat factors. The growing season of 2013 is characterized by the most reduced composition of zooplankton (43 taxa). The most favourable for zooplankton communities was 2014 (63 taxa). The highest variability of zooplankton structure along the Dniester River longitudinal profile was recorded in 2015 (Fig. 1). Pollution and eutrophication of water bodies and water courses leads to a simplification of the structure of aquatic communities that is reflected in the reduction of their diversity (Alimov, 1995). In this respect it should be noted two sites of the Dniester River with significant anthropogenic impact on the habitat: Soroca and Suclea. In both cases, the load on the ecosystem is caused by discharges untreated wastewaters (urban zone So- roca) or insufficiently treated wastewaters (urban zone Bender - Tiraspol). Two types of water ecosystems can be determined on the studied zone of the Dniester River: lotic habitat in the sectors Naslavcea - Camenca and Vadul lui Voda – Palanca, and relatively lentic habitat in the Dubossary reservoir where flow velocity decreases to 0.1 m/s. The spatial heterogeneity increases the species diversity. One would expect that the similarity coefficient will decrease along the spatial gradient of the river and will be higher for neighboring sectors, as it was registered in 2013 (Table 1). But this trend is not always an unambiguous for compared stations, if a water body includes different types of ecosystems, that it is demonstrated in the similarity matrix for the sampling of 2014 and 2015. Acknowledgements: the research was carried out within the framework of the Na- tional project 15.817.02.27A..

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