Phytoplankton blooms in front of cape Galata (Black Sea) during the period 2008-2017

D. Klisarova*, D. Gerdzhikov
Institute of Fish Resources, 4 Primorski Blvd., 9000 Varna, Bulgaria
(Manuscript received 7 November 2019; accepted for publication 21 January 2020)

Abstract. The aim of the study was to identify the peculiarities of the development of phytoplankton blooms (annual and seasonal dynamics) in front of cape Galata, Bulgarian Black Sea coast in the period 2008-2017. In that area up to 30 nautical miles (nm), from 6 stations (G-1, G-3, G-5, G-10, G-20 and G-30, respectively at 1, 3, 5, 10, 20 and 30 nm from the coast), 187 phytoplankton samples were collected. A total of six phytoplankton species were recorded, developing with the following blooming concentrations: Emiliania huxleyi, Oscillatoria sp., Merismopedia sp., small Flagellates (Cryptophyceae), Prorocentrum cordatum (minimum) and Pseudo-nitzschia delicatissima. It was found that the reported in previous periods trend of increasing phytoplankton biomass in front of cape Galata had already changed. Compared to the observed quantities in the period 1993-2007, the current phytoplankton values in the surface layer (up to 30 nm in front of cape Galata) were 1.63 times lower in abundance and 5.60 times lower in biomass.

Influence of biomanipulation on the living communities and the water quality in the Strezhevo hydroecosystem, R. Macedonia

  1. R. Nastova*, V. Kostov, N. Gjorgovska, V. Levkov

Institute of Animal Science, “Ss Cyril and Methodius” University of Skopje, Bul. Ilinden 92a, 1000 Skopje, Republic of Macedonia

(Manuscript received 21 June 2017; accepted for publication 16 January 2018)

Abstract. The aim of this study was to investigate the influence of the biomanipulation on the living communities and water quality in the Strezhevo hydroecosystem, Republic of Macedonia in which a problem with increase of primary organic production has occurred. The biomanipulatory intervention in water bodies is used to prevent the development of macrophyte vegetation. It is achieved by direct influence on the increased development of phytoplanktonic production and macrophytes by gradual and controlled introduction of grass carp (Ctenopharyngodon idella). The study was conducted in the period June-September 2012 in two earthen ponds (A and B), situated in Strezhevo Lake with 100 specimens of grass carp/pond with average individual mass of 4 kg and age of 3–5 years. The following were monitored: water – temperature (oC), pH, dissolved oxygen (O2 mg/l) and saturation (%); grass carp – length (mm), weight (kg), Fulton and Clark coefficients of fattening, consumption of added in ponds fresh vegetable mass (kg), consisting of Ceratophyllum demersum (hornwort) (95%) and Potamogeton pusillus (small pondweed) (5%). Based on the results obtained, the meliorative ability of this species with high density of the stock was evaluated as very favourable. At optimal temperature, oxygen regime and pH conditions of water, this herbivore fish species consumed the present macrophytic vegetation very intensively, and in the case of its absence, also the additional share of fresh herbal mass, showing certain selectivity towards particular water vegetation species. Thus, grass carp maintains an optimal composition of the macrophytic communities in the hydroecosystem.

Taxonomic composition of phytoplankton in Black Sea area in front of the Cape Galata (2008-2016)

D. Klisarova, D. Gerdzhikov

Institute of Fish Resources, 9000 Varna, Bulgaria
(Manuscript received 13 August 2017; accepted for publication 3 October 2017)

Abstract. In this article have been investigated the taxonomic structure of the phytoplankton communities developing in the Black Sea area in front of the Cape Galata. For the period 2008 – 2016, relatively high species diversity was found (161 species). Throughout the most of the year dominated class Dinophyceae (up to 54.17%). The number of phytoplankton species decreased with distance from the shore, but the percentage participation of the group of peridineas and diatoms in the general taxonomic composition grew. Only in class Prymnesiophyceae increased biodiversity was registered in the high seas

Investigation of the biota of Burgas Bay, Black Sea

D. Klisarova*, E. Petrova, D. Gerdzhikov, S. Stoykov

Institute of Fish Resources, 4 Primorski, 9000 Varna, Bulgaria
(Manuscript received 23 March 2016; accepted for publication 30 May 2016)

Abstract. Burgas Bay is the largest one on the Bulgarian Black Sea coast. Industrial plants along the coast as well as ports for liquid and solid cargoes create conditions of anthropogenic pressure on hydrobionts in that area. Macrozoobenthos and phytoplankton samples were collected under a specific scheme in connection with the construction of the Burgas-Alexandroupolis oil pipeline, at stations located around the designated places for unloading tankers. During the study period (2009 – 2010), 88 phytoplankton species distributed in 13 classes were identified and over 50 species of benthic species distributed in four main groups: Polychaeta, Mollusca, Crustacea and the mixed group Diversa.


Application of up-to-date environmental indices for assessment of seawater

D. Klisarova*, D. Gerdzhikov, E. Petrova

Institute of Fish Resources, 4 Primorski, 9000 Varna, Bulgaria
(Manuscript received 23 March 2016; accepted for publication 26 May 2016)

Abstract. The paper discusses the indices for assessment of the ecological status of seawater which are applied in the studies of algae and macrozoobenthic communities in the Bulgarian Black Sea territorial waters. They are applicable to contemporary environmental assessments in accordance with the European directives on environmental protection. Presented are also studies carried out in recent years on marine plants and bottom organisms and the resulting conclusions. The result was that we identified the ecological status of the marine ecosystem on BQE phytoplankton, macrophytobenthos and macrozoobentos from “moderate” to “good” in the period of investigation.


Assessment of Bulgarian Black Sea coastal water using the biological quality element phytoplankton

D. Petrova*, D. Gerdzhikov

Institute of Fish Resources, 4 Primorski, 9000 Varna, Bulgaria

Abstract. The aim of this paper was to study and assess the quality of Bulgarian Black Sea coastal water using the biological quality element phytoplankton communities, according to the requirements of the Water Framework Directive (WFD EU, 2000) and the developed reference values. A total of 134 species of microalgae were identified among which dominated the complex Bacillariophyceae/Dinophyceae (72.39 %). There was an improvement of the ecological status in three to six points from September to November 2011 (Krapetz, Shabla, Kamchiya, Dvoynitsa, Nessebar, Sozopol). This was due to the better characteristics of the phytoplankton community referring to Shannon index, number of species, Sheldon index, %MEC, DE% and Chl-a. Phytoplankton blooms were recorded in Krapetz, Varvara and Nessebar in September and in Albena, Varna-North, Sarafovo and Rosenets in November. Studies conducted have contributed to contemporary assessment of the water status in the one-mile area within the National Environmental Monitoring System (NEMS).



Ecological assessment of the phytoplankton community in the Bulgarian Black Sea coastal waters

D. Petrova, G. Kostadinova, D. Gerdzhikov
Abstract. The purpose of this article was to study and make an ecological assessment of the phytoplankton community in the Bulgarian Black Sea coastal waters for the period 2008 – 2010. Taxonomic distribution in the phytoplankton community is traced and analyzed on the basis of 389 quantitative and qualitative seawater samples. Dominant and subdominant phytoplankton species, qualitative and quantitative monthly and seasonal dynamics of the main groups in phytoplankton have been identified as well as their importance for the ecological status of the Black Sea ecosystem. The obtained results for phytoplankton demonstrated a comparative reduction of the trophic degree of the Bulgarian coastal waters, dominating natural factors of the environment over the anthropogenic ones and the present status of “good” and “very good” of the researched coastal area, according to the explored parameters. The phytoplankton annual development is accordingly with the climatic conditions. Also three seasonal phytoplankton successions were defined throughout the year.


Contemporary assessment of the development of the genus Chaetoceros in the Bulgarian coastal waters

D. Petrova, D. Gerdzhikov, G. Kostadinova
Abstract. The genus Chaetoceros Ehrenberg of class Bacillariophyceae is widespread and abundant in species in the Black Sea phytoplankton. The aim of the article was to study its distribution in water and to analyzed its contemporary involvement in the formation of qualitative and quantitative composition of phytoplankton, the season dynamics of genus during the hydro-biological year and its role in the ecology of the Bulgarian Black Sea coastal water area for the period 2008 – 2010. It was found out that the highest species diversity, abundance and biomass of the genus were in the autumn and spring – a bimodal pattern of annual growth. 20 species and forms were registered of the genus Chaetoceros. They formed up to 1/3 of the taxonomic composition of Diatoms and 1/10 of all phytoplankton species. “Blooms” of representatives of the genus Chaetoceros in the researched period were not registered.


Ecological status of Varna Bay through the state of phytoplankton, macrozoobenthos and macrophytes during the autumn of 2011

D. Petrova, E. Petrova, D. Gerdzhikov, V. Vachkova, R. Bekova
Abstract. The paper assessed the ecological status of Varna Bay during the autumn of 2011, according to the assessment of biotic components phytoplankton, macrozoobenthos and macrophytes in accordance with the requirements of the European Water Framework Directive WFD EU (2000). The state of Varna Bay is assessed as “good”.odbutton