State of Environment Report 2001 - 2006/7 CHAPTER 5 THE STATE OF PHYTOPLANKTON (D. Nesterova et al.) D. Nesterova Odessa Branch, Institute of Biology of the Southern Seas, NASU, Odessa, Ukraine S. Moncheva Institute of Oceanology, Bulgarian Academy of Sciences, Varna, Bulgaria A. Mikaelyan1, A. Vershinin1 and V. Akatov2 1 P.P.Shirshov Institute of Oceanology RAS, Moscow, Russia 2 Maykop State Technological University,Maykop, Russia L. Boicenco National Institute for Marine Research and Development "Grigore Antipa" (NIMRD), Constanta, Romania Y. Aktan3 and F. Sahin4 3 Marine Sciences, Faculty of Fisheries, Istanbul University, Istanbul, Turkey 4 Sinop University, Fisheries Faculty, 57000 Sinop, Turkey T. Gvarishvili Georgian Marine Ecology and Fisheries Research Institute (MEFRI), Batumi, Georgia 5.1. Introduction Phytoplankton as the foundation of marine trophic chain is among the best indicators for assessment of the state of eutrophication. Nutrient enrichment/eutrophication often gives rise to shifts in phytoplankton species composition (e.g. from diatoms to dinoflagellates) and an increase in the frequency and/or magnitude and/or duration of phytoplankton (including nuisance/potentially toxic) blooms. The present chapter analyzes the recent trends of changes in phytoplankton species composition and then highlights main features of its contemporary state along the Black Sea shelf waters. The assessments are based on the evaluation of historical data as well as those collected during the present decade within the framework of various international and regional field campaigns as well as national monitoring programs. 173 CHAPTER 5 THE STATE OF PHYTOPLANKTON (D. Nesterova et al.) 5.2. Species composition Data compiled by many sources documented 750 phytoplankton species in the Black Sea (Ivanov 1965, Pitsyk 1950, Sorokin, 2002). Owing to considerable differences in hydrological and hydrochemical properties, phytoplankton composition differed considerably in different parts of the sea. In particular, the shallow, less saline and heavily euthrophied northwestern part of the sea sustained large number of brackish and freshwater species as compared with other parts (Ivanov, 1967). Northwestern and Crimean shelves: A summary of the lists of phytoplankton species studied in 1973-2005 in the northwestern Black Sea shelf (NWS) (Nesterova, 1998; Guslyakov and Terenko, 1999; Nesterova and Terenko, 2000; Terenko, 2004; Nesterova and Terenko, 2007) showed that phytoplankton is represented by 697 species and interspecies pertaining to 11 phyla (Table 5.1). During 1973 - 2005, diatoms and dinophytes constituted main species as observed prior to 1973, but their ratio has changed in comparison to 1950s (Ivanov, 1967). The diatom species decreased from 48.3% to 34.9%, while dinophytes increased from 20.4 % to 28.5 %. Freshwater green algae species increased from 16.7% to 22.5%, while blue-green algae remained around 5-6%. Due to revised phytoplankton composition, representatives of new phyla of Cryptophyceae Hillea fusiformis, Prasinophyceae Pterosperma cristatum, Pt. jorgensenii and a Choanoflagellida Bicosta spinifera species appeared. An increase in the species diversity of dinophytes was noted in 1973 - 1993 when 36 new species were listed in the NWBS (Nesterova, 1998). Later, 48 species were added to the list of which 37 were new to the Black Sea (Terenko, 2004; 2005). The dinophytes included potentially toxic species Alexandrium psedogonyaulax, Cochlodinium polykrikoides, Gyrodinium cf. aureolum (Terenko, 2005, 2005 a) as well as a new species (Prorocentrum ponticus) and a new variety (Prorocentrum micans var. micans f. duplex) (Krakhmalniy and Terenko, 2002). Similarly, new green algae appeared as the genera Monoraphidium (M. contortum, M. obtusum) and Scenedesmus (Sc. polyglobulus). At present, the number of marine and marine-brackish species decreased from 60.3% to 50.5%. Simultaneously, there has been an increase in freshwater and freshwater-brackish species - 49.5% and 39.7%, respectively. The bulk of phytoplankton abundance and biomass is represented by a massive development of a small group of species in certain seasons. In the 1950s - 1960s, it was 41 species (Ivanov, 1967), and increased to 85 species in the past two decades (Black Sea, 1998). Besides the usual representatives as Skeletonema costatum, Cerataulina pelagica, Chaetoceros socialis, Leptocylindrus danicus, Prorocentrum cordatum, Pr.micans, other species like Leptocylindrus minimus, Chaetoceros insignis, Gyrodinium cornutum, cryptophytes Hillea fusiformis, coccolithophorides Emiliania huxleyi, freshwater diatoms Skeletonema subsalsum, Stephanodiscus hantzschii, blue-green algae of the genera Gleocapsa Merismopedia have entered into the NWBS phytoplankton bloom events. Common species including Heterocapsa triquetra, Scripsiella trochoidea were found in the NWBS in 1957-1961 (Ivanov, 1963). Besides, typical summer - autumn phytoplankton species like Thalassionema nitzschioides, Chaetoceros curvisetus were observed in 1950 - 1960, while Pseudosolenia calcar avis tended to decrease in frequency and abundance (Nesterova, 1987). 174 State of Environment Report 2001 - 2006/7 Table 5.1. Taxonomic composition of Black Sea phytoplankton in Ukraine waters Phyla Northwestern part Southeastern coast of Crimea 1954-60* 1973-05** 1938-59*** 1979-98**** Bacillariophyceae 180 243 73 63 Dinophyceae 76 199 39 69 Cryptophyceae - 8 3 - Chlorophyceae 62 158 4 3 Cyanophyceae 24 37 4 2 Prymnesiophyceae 9 25 19 - Chrysophyceae 4 6 5 27 Dictyochophyceae 5 7 - - Prasinophyceae - 2 - - Euglenophyceae 12 11 - 1 Choanoflagellidea - 1 - - Total 372 697 125 165 *- Ivanov (1967); **- Nesterova (2006); Nesterova, Terenko, 2007; ***- Proshkina- Lavrenko (1955) and Ivanov (1965); **** - Senichkina et al. (2001) Phytoplankton species in the southeastern coast of Crimea during the 1940-1960s included 125 species and interspecies taxa from 5 algal phyla (Table 5.1) (Stroykina, 1950; Koshevoy, 1959; Mironov, 1961). In more recent years (1979-1998), it increased to 165 species and varieties, which all indicated some changes in taxonomic composition. In contrast to the previous phase, dinophytes increased from 31.2 % to 41.8 and chrysophytes from 4% to 15.1%, while diatoms decreased from 58.4% to 38.1%. The species diversity of coccolithophorids rose to 74 new species which were common for the whole Black Sea, while 21 species were observed for the first time. Compared to 211 species and varieties of planktonic algae recorded in the Sevastopol Bay in 1948 (Senicheva, 2000), there were 84 species in 1996 - 1997 and 173 species and varieties in 2001 - 2004. The latter was represented by 11 classes and 2 taxonomic groups; small flagellate algae and olive green cells. The basis of species diversity was similar to that of the NWBS and mainly composed of diatoms (45%), dinophytes (35%), and also Prasinophyceae (11%) (Polikarpov et al., 2003). The composition of dominant species of Skeletonema costatum, Leptocylindrus danicus, Chaetoceros socialis near Sevastopol for a period of 65 years has not undergone significant changes (Polikarpov et al., 2003). Pseudo-nitzschia delicatissima was an exception replacing Cerataulina pelagica in 2001 - 2004. Changes have been noted mainly in the composition of subdominant species replacing the dinophyte algae of the genera Glenodinium, Protoperidinium, Prorocentrum for Prymnesiophyceae genera of Syracosphaera and Emiliania. At the same time new diatom species have been encountered along the coast of Crimea, and a new variety has been described as Chaetoceros diversus var. papilionis (Senicheva, 2002) as well as dinophytes and silicoflagellates (Kuzmenko, 1966; Senichkina, 1973). Western Black Sea shelf: The revision of phytoplankton check-list in 1980-2005 documented 544 species distributed among 8 classes (Fig. 5.1) which indicated more than two-fold increase as compared to 230 species listed in the 1954-1980 period. Although a part of this change was related to improved sampling strategy, microscope 175 CHAPTER 5 THE STATE OF PHYTOPLANKTON (D. Nesterova et al.) quality, frequency and regions of sampling, changing environmental conditions and introduction of exotic species also played a role (Moncheva, Kamburska, 2002). Diatoms (212 species) and dinoflagellates (162 species) constituted bulk of the phytoplankton pool; the Dinophyceae species contribution rose to about 40% of the total number, e.g. an increase of more than 3 times. The same also applies to other classes; for example, species from Cryptophyceae and Choanoflagellates groups have not been reported at all before 1980s. The presence of rare and new Bacillariophyceae (Thallasiotrix longissima, Th. antarctica Lioloma elongatum, L. pacificum,Triblionella acuminate), Dinophyceae (Ceratium furca var. bergii, Ceratium furca var. eugramma, Cochlodinium archimedes, C. citron, Kofoidinium lebourae), a number of Gymnodinium species (Gymnodinium canus, G. cintum, G. dominans, Gymnodinium fuscum etc.) Gyrodinium (Gyrodinium spirale), and numerous Cryptophyceae (mainly from genus Chroomonas, Cryptomonas, Rhodomonas, Leucocryptos etc), Chlorophyceae (Kirchneriella, Trochiscia, Treubaria), Chrysophyceae (Braarudosphaera bigelowi, Octactis octonaria, Calciosolenia granii v. cylindrotheca, etc.), and different microflagellates add significantly to the diversification of phytoplankton assembly. Most of the species listed above are mixo-heterothrophs, that might have important functional bearings at ecosystem level (Moncheva et