686 Bulgarian Journal of Agricultural Science, 24 (No 4) 2018, 686–697 Current state of phytoplankton in Batak reservoir (Southwestern Bulgaria) Kostadin Dochin1*, Velika Kuneva2, Angelina Ivanova1, and Ivan Iliev3 1Department of Aquaculture and Water Ecosystems, Institute of Fisheries and Aquaculture, 248 Vasil Levski Str, 4003 Plovdiv, Bulgaria 2Department of Mathematics and Informatics, Faculty of Economics, Agricultural University, 12 Mendeleev Blvd, 4000, Plovdiv, Bulgaria 3Department of Biochemistry and Microbiology, Faculty of Biology, University of Plovdiv, 24 Tsar Assen St, 4000 Plovdiv, Bulgaria *E-mail: [email protected] Abstract Dochin, K., Kuneva, V., Ivanova, A., & Iliev, I. (2018). Current state of phytoplankton in Batak reservoir (South- western Bulgaria). Bulgarian Journal of Agricultural Science, 24(4), 686–697 The aim of the present study was to update the current status of the phytoplankton composition in Bulgarian reservoir with high social, environmental and economic importance such as the Batak reservoir and to analyze its relationship with the total bacterial count (TVC) and the environmental factors. A total of 106 phytoplankton taxa were identifi ed for the study period. Class Bacillariophyceae was presented by the highest number of species (34) followed by divisions Chlorophyta (26) and Cyanoprokaryota (17). The maximum of species diversity was established in the samples from September at the station situ- ated near the dam wall (S1) with the lowest number being detected in July at the same station. The phytoplankton abundance (PhN) and biomass (PhB) has reached their maximum in September with highest values in the epilimnion samples with a steep decrease in depth of the reservoir. Seasonally and spatially waters were dominated by the diatoms Tabellaria fenestrata var. asterionelloides Grunow, Fragilaria crotonensis Kitton, green algae Pandorina morum (O.F.Müller) Bory, and Desmodesmus communis (E. Hegewald) E. Hegewald. Aphanizomenon fl osaquae Ralfs ex Bornet & Flahault is presented with relatively high numbers. A Woronichinia naegeliana (Unger) Elenkin bloom was established in November at the tail of the reservoir. Signifi - cant positive correlations were established between phytoplankton abundance and the nitrogen forms, total phosphorus, with negative correlations between PhN and TVC. According to cluster analysis, the surveyed stations are grouped into two separate clusters each with similar spatial and seasonal characteristics. The stations at the dam wall and at the tail of the reservoir are characterized by the highest hierarchical distance. Keywords: phytoplankton; abundance; biomass; algal bloom; TVC; Batak reservoir Introduction ral changes in its structure are essential for metabolism in water systems (Calijuri et al., 2002; Crossetti and Bicudo, Phytoplankton is the fi rst of the communities to respond 2008). The community reacts to changes in the environment to environmental changes based on a variety of factors of with alteration in its qualitative and quantitative composi- different origins (Wilk-Wozniak et al., 2013), so the tempo- tion which makes it suitable for an environmental indica- Current state of phytoplankton in Batak reservoir (Southwestern Bulgaria) 687 tor (Cabecinha et al., 2009). Dam building along the rivers main morphometric characteristics are present in Table 1. leads to changes in the water current and have a strong im- Currently, the reservoir is used for cage aquaculture, tourism pact on phytoplankton composition (Dembowska, 2009). and as a drinking water supply. The fi rst study on the phytoplankton in Batak reservoir was conducted by Naidenov (1964). Later the processes of Тable 1 formation of the community are described along with the Morphometrical characteristics during the investigation description of the main characteristics of the water body period of the Batak reservoir (Saiz, 1973, 1977). Two annual maximums in the com- Year 2015 munity development have been described with green algae Resеrvoir name Batak (IBW1316) having the highest biomass and diatoms being the most Altitude (m) 1107 abundant. According to Saiz (1977) water level directly af- Water volume (m3) 310 x 10-6 fects the phytoplankton dynamics, and the water tempera- Tributary Matnitsa River ture has a signifi cant infl uence on its temporal dynamics. Source Matnitsa River The altitude and the depth of the reservoir also play a major Built 1959 role in the community composition (Beshkova, 1996). A Location South Bulgaria number of studies established an increase in the species di- Outfl ow (m3) 124.8 versity along the longitudinal axis of the reservoirs in the Catchment area (km2) 463.29 direction from the dam wall to the tail of the water bodies Station 1 (Wall) (Beshkova, 1996; Traykov, 2005; Belkinova et al., 2007; GPS coordinates (42°00.877′N) (024°11.948′E) Tsanev and Belkinova, 2008; Belkinova et al., 2012). Ac- Station 2 (Cages) cording to Dochin (2014), Dochin and Stoyneva (2014, GPS coordinates (41°57.371′N) (024°10.948′E) 2016), in Kardzhali and Dospat reservoirs, where the big- Station 3 (Island) gest Bulgarian net-cage farms are situated, there is a clear GPS coordinates (41° 57.704′N) (024°10.094′E) dependence between the phytoplankton abundance and the Station 4 (Tail) organic matter content with highest described values near GPS coordinates (41°57.965′N) (024°12.390′E) the cage farms and around the dam walls. The Batak res- ervoir is one of the largest in Bulgaria. It is included in the list of water bodies for drinking water supply. In the same Water sampling time, it has been used for cage aquaculture for more than Samples for phytoplankton, microbiological and physi- 10 years and other recreational activities and the microbio- cochemical analysis were collected from four sites in the logical and physicochemical water quality does not meet aquatory of the reservoir (Figure 1). The water samples for the requirements of the EU Water Directive (2000/60/EC). phytoplankton physicochemical analysis were collected by In recent years the data regarding the algal fl ora, a main Niskin-Type water sampler 5 L model (Hydro-Bios Ap- environmental indicator, in Batak reservoir is scarce which paratebau GmbH, Germany) from the epi-, meta- and hy- sets the objective of the present study to analyze the current polimnion at each site. The phytoplankton samples were state of phytoplankton in the reservoir and analyze its con- processed by standard methods of fi xation with formalin to nection with microbiological indicators for water quality fi nal concentration 4% and further sedimentation (ISO 5667- and environmental factors. 1:2006/AC:2007; ISO 5667-3:2003/AC:2007). The samples for determination of the total count of viable bacteria (TVC) Materials and Methods were collected from the superfi cial layer (0.5 m below the surface), metalimnion and the bottom layer (1 m above the Study area sediment) using MICROS water sampler (Hydro-Bios Ap- Batak Reservoir (IBW1316) is part of the largest water paratebau GmbH, Germany). TVC, determined at 22°C, was cascade Dospat-Vacha. It is situated in the Western Rhodope expressed as colony forming units per liter (cfu.l-1). Mountains, Southern Bulgaria near the town of Batak on the river Matnitsa (Michev and Stoyneva, 2007). According Physicochemical analysis to Belkinova and Gecheva (2013), it is designed as heavily Water temperature (ТMP) and dissolved oxygen (DO) modifi ed water body in oligotrophic conditions and based on were measured in situ with an oxygen meter (WTW OXY the Bulgarian topology it refers to the mountain and semi- 1970i). Electrical conductivity (Cond.) and рН were measured mountain lake types. The reservoir was built in 1959 and its with WTW conductivity meter (Cond3310/SET) and WTW 688 Kostadin Dochin, Velika Kuneva, Angelina Ivanova, and Ivan Iliev standard analytical methods (ISO 8467:1993; ISO 5664:1984; ISO 7890-1:1986; ISO 6878:2004) as described by Iliev et al. (2017). Total phosphorus (TP mg.L-1) concentration was mea- sured by Phosphate Cell Test (114543, Merck Millipore). Phytoplankton analysis Phytoplankton abundance (PhN) was determined by direct microscope counting on Bürker chamber (Laugaste, 1974). The counting was carried out individually (cell, fi la- ment or colony). The numbers (PhN) are expressed as x10– 6cells.L–1. The biomass (PhB) is expressed as mg.L–1. The species composition was determined by light microscopy at magnifi cation x400 on Carl Zeiss, Axioscope 2, using stan- dard taxonomic literature with the critical use of AlgaeBase (Guiry and Guiry, 2017). Diatoms were identifi ed after Cox (1996). The cell was used as the main counting unit and the biomass was estimated by the method of stereometrical ap- proximations (Rott, 1981; Deisinger, 1984). Statistical analysis Statistical analysis was performed with SPSS 13 (IBM an- alytical). The experimental data were processed by correlation analysis to establish and evaluate the relationship between the tested parameters, expressed by Pearson’s correlation coeffi - cient. A hierarchical cluster analysis (Ward, 1963; Duran and Odelle, 1977) was used to identify the similarity between the Fig. 1. Map of the Batak reservoir with his position in samples tested and their grouping on the basis of important Bulgaria and location of the sampling sites indicators. The Euclidean distance was used as a measure of similarity. To avoid differences in dimensions of the surveyed pH-meter (315/SET) respectively. Ammonium (NH4-N), ni- indicators, the data was previously standardized. The