The Zooplankton of the Danube-Black Sea Canal in the First Two Decades of the Ecosystem Existence Victor Zinevici, Laura Parpală, Larisa Florescu, Mirela Moldoveanu
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Travaux du Muséum National d’Histoire Naturelle © 30 décembre «Grigore Antipa» Vol. LVI (2) pp. 227–251 2013 DOI: 10.2478/travmu-2013-0017 THE ZOOPLANKTON OF THE DANUBE-BLACK SEA CANAL IN THE FIRST TWO DECADES OF THE ECOSYSTEM EXISTENCE VICTOR ZINEVICI, LAURA PARPALĂ, LARISA FLORESCU, MIRELA MOLDOVEANU Abstract. This paper reports the invasive subspecies Podonevadne trigona ovum (Zernov, 1901), as dominant in the Danube-Black Sea Canal. In the first two years of the existence of the anthropogenic ecosystem (1985-1986) the zooplankton summarizes only 72 species. Over two decades it recorded the presence of 127 species. As a result of nutrient accumulation, in 2005, the zooplankton abundance has significantly increased, reaching 330 ind L-1, followed by an evident growth of biomass (2285 μg wet weight L-1). In 2005, the productivity registered 731.8 μg wet weight L-1/24h. Résumé. Le présent papier rapport l’existence de la sous-espèce envahissante Podonevadne trigona ovum (Zernov, 1901), dominante dans le canal Danube – Mer Noire. La sous-espèce appartient à l’ordre Onychopoda, et elle a une origine Caspienne. Dans les premières deux années qui suit l’apparition de cet écosystème anthropogénique (1985-1986), le zooplancton a été reprèsenté par 72 espèces; après deux décennies, le nombre d’espèces a augmenté à 127. A la suite d’accumulation de nutriments, en 2005 l’abondance du zooplancton a augmentée de manière significative, atteignant 330 ind L-1, suivie d’une augmentation marquée de la biomasse (2285 mg s.um. L-1). En 2005, la productivité du zooplancton a enregistré 731,8 mg mat.hum. L-1/24h. Key words: Danube - Black Sea Canal, species richness, abundance, biomass, productivity, invasive species. INTRODUCTION The need to develop continental shipping, shortening of waterways and ensuring water supply to urban, industrial or agricultural centers, caused the appearance of man-made basins in the last 4-5 centuries. Much larger navigable canals were built beginning with the 19th century. In this category the Caledonian Canal (Scotland, 97 km), Erie (584 km), Illinois (154 km) or Intracoastal Waterway (4800 km) (United States), the Volga-Don (101 km), Volga-White Sea, 227 km (Russia or Black Sea-Dnieper-Bug-Baltic Sea (Ukraine and Belarus) can be mentioned (www.waterwayguide.com; www.scottishcanals. co.uk.; www.european-waterways.eu). In the hierarchy of the major channels of Earth, the Danube-Black Sea Canal occupies the third position, after Suez and Panama. It represents a significant segment of the important European waterways which ensures, together with the Danube River and the Danube-Main-Rhine Canal (171 km) the link between the Black Sea and the North Sea (www.geografialumii.ro). Having a series of benefits to human society, the canals can generate, at the same time, important ecological disorders. By passing geographical barriers for millions of years old, they make possible the spread of some species into new ecosystems. In favourable environmental conditions, the alien species can get invasive characteristics by changing the structure and trophic relationships of the indigenous communities and ultimately, causing damage of an economic nature (Marlene, 1990; Rivier, 1998; Zinevici et al., 2011). 228 VICTOR ZINEVICI, LAURA PARPALĂ, LARISA FLORESCU, MIRELA MOLDOVEANU For example, the construction of the Volga-Don Canal allowed the expansion of invasive organisms of the Caspian Sea to the Sea of Azov and the Black Sea. A similar phenomenon has been found in the Central Europe after opening the Main – Danube Canal that connect the Danube basin and the Black Sea to the Rhine and the North Sea. Other Ponto-Caspian species arrived in the Baltic Sea basin and later in the American Great Lakes after building a complex system of channels that links Volga, the Don, Dnieper, Bug, Vistula, Oder, Elba, Ladoga, Onega, connecting the Baltic Sea with the Black Sea and the Caspian Sea (Reid & Orlova, 2002; Alexandrov et al., 2007; Grigorovich et al., 2002). Strong invasive phenomena generated by the building of some canals were produced also in the marine environment. The creation of the Suez Canal caused the migration from the Indian Ocean and Red Sea into the Eastern part of the Mediterranean Sea over 300 species (Galil, 2000; Goren & Aronov, 2002; Briggs, 2007). The phenomenon is known as “lessepsian migration” (after the name of Ferdinand de Lesseps, the designer of the channel). It is estimated that approx. 17% of invasive marine species were transported through the channels (Galil et al., 2007). In Romania, 67 invasive species were reported (60% marine and 40% freshwater species) (Skolka & Preda, 2010). Among these, Mnemiopsis leidyi Agassiz, 1865 has produced a true collapse of the Black Sea ecology (Faasse & Bayha, 2006). More invasive species (185) have penetrated in the last decades of the 20th century in the Great Lakes. Dreissena polymorpha (Pallas, 1771), Bythotrephes longimanus Leydig, 1860 and Cercopagis pengoi (Ostroumov, 1891) produced important ecological changes and economic damage (Johannsson et al., 1991; Cohen & Carlton, 1998; Therriault et. al., 2002). The intrusion of the immigrants in aquatic basins is achieved mainly on passive way (69%), through anthropogenic vectors (ballast water and biofuel), complementary through aquaculture (6%), fish keeping, birds and aquatic animals (10%) (Ruiz & Carlton, 2003; Molnar et al., 2008; Minchin et al., 2009). The vessel traffic in the Danube-Black Sea Canal, the contact with the Black Sea waters, its interaction with the Sea of Azov and the presence of seabirds, running extensive movements in the area of the two marine pools have created conditions for the appearance of the zooplankton species in channel originating in the Caspian basin (Zinevici et al., 2011). As a result of the extensive effects induced by some invasive species, most ecological research aimed, mainly, at their ecology and interaction with some native species and less at the diversity or the community production. These aspects bring a touch of originality of this article. MATERIAL AND METHODS The spatial analysis reveals the presence of two branches. The main (64 km) is located between the fluvial port of Cernavodă (Danube km 299) and the maritime port Agigea. Riverbed width varies within the limits of 120-140 m, and the average depth is 7 m. The secondary branch (31 km) is located between the Poarta Albă port (km 35 of main branch) and Midia seaport. The secondary channel width varies within the limits of 80-90 m and minimum depth is 5.5 m (Fig. 1). The water circulation and navigation are provided by 4 locks fitted with separate enclosures for every sense of movement. One of the locks is situated in the contact zone of the Danube waters with the main branch of the Canal, another is THE ZOOPLANKTON OF THE DANUBE-BLACK SEA CANAL 229 11 Năvodari Danube 1Cernavodă 2 9 10 Cernavodă lock 8 3 4 Ovidiu lock 5 7 Black Sea 6 Medgidia Agigea 12 13 Agigea lock Fig. 1 - The map of the Danube - Black Sea Canal with the indication of the sampling sites (1985 – 1986: 5, 12, 13; 2005: 1-11). located on the secondary branch, and the other two are located in the area of contact with the Black Sea. The water flows in the ranges of the two branches, between 0.3-0.9 mc/s and 0.13-0.23 mc/s, respectively. The water storage capacity is approximately 36 millions mc. Samples were collected in 1985, 1986 and 2005. Scientific data originated in two projects, one conducted during 1985-1986, the other in 2005. Most sampling points coincide, in 2005 (Fig. 1). Sampling was done seasonally in 13 sites (three in 1985 and 1986 and 11 in 2005) (Fig. 1, tab. 1). For this purpose a Patalas-Schindler device was used (5 l). For each sample 50 l throughout the water column were taken. The samples were concentrated by filtering through a gauze planktonic net with a mesh size of 65 µm. The sample preservation was made with 4% formaldehyde solution. Species were identified with an inverted Zeiss microscope using identification keys for ciliates (Foissner et al., 1991, 1992, 1994), testaceas (Bartoš, 1954; Grospietsch, 1972), rotifers (Ruttner-Kolisko, 1974; Rudescu, 1960), cladocerans (Negrea, 1983; Table 1 Sampling sites of zooplankton. No st. Canal km Period Geographic landmark Canal section 1 64+000 2005 Cernavodă Danube – Black Sea 2 61+000 2005 Upstream Cernavodă lock Danube – Black Sea 3 47+600 2005 Mircea Vodă Danube – Black Sea 4 40+000 2005 Medgidia Danube – Black Sea 5 37+900 1985 - 1986, 2005 Medgidia Danube – Black Sea 6 28+700 2005 Poarta Albă Danube – Black Sea 7 23+000 2005 Basarabi Danube – Black Sea 8 20+700 2005 - Poarta Albă – Năvodari 9 15+100 2005 - Poarta Albă – Năvodari 10 10+000 2005 Downstream Ovidiu lock Poarta Albă – Navodari 11 2+000 2005 Năvodari Poarta Albă – Năvodari 12 0+000 1985 - 1986 Upstream Agigea lock Danube – Black Sea 13 - 1985 - 1986 Black Sea Agigea Zone 230 VICTOR ZINEVICI, LAURA PARPALĂ, LARISA FLORESCU, MIRELA MOLDOVEANU Rivier, 1998; Smirnov, 1996; Benzie, 2005), copepods (Damian-Georgescu, 1963, 1966, 1970; Dussart & Defaye, 2001). The analysis of abundance, biomass and productivity was assessed at species level. The results were presented by systematic groups, trophic levels (herbivorous zooplankton - c1 and predator zooplankton - c 2) and total zooplankton. The abundance was expressed in ind L-1, biomass in µg wet weight L-1and productivity in μg wet weight L-1/24h. In order to concentrate the great volume of data, the analysis of zooplankton was made, in most cases, for the whole ecosystem (mean values). In turn, for the evaluation of the spatial dynamics of the invasive Podonevadne trigona ovum, the data analysis was detailed on the 13 stations.