HR: 1400h
AN: OS23B-17    [Abstracts]
TI: The Contemporary State of Development of Free-living Nematodes of the Northwestern Black Sea
AU: * Kulakova, I
EM: ibss@paco.net
AF: : Odessa Branch, Institute of Biology of Southern Seas, National Academy of Sciences of Ukraine, 37 Pushkinskaya St., Odessa, 65125, Ukraine
AB: The work was carried out on samples taken during an expedition on the Black Sea Western shelf (Bulgarian, Romanian, Ukrainian) in October, 2003 in the framework of the UNDP-GEF Black Sea, Ecosystem Recovery Project. Nematodes due to specific biological characteristics (high productivity, short life cycles) quickly respond to environmental changes by reducing species diversity, increasing abundance and decreasing biomass. Our studies have confirmed this. For the western Black Sea shelf 67 nematode species of 6 orders have been recorded. Of the 12 groups of meiobenthos encountered on the western Black Sea shelf the frequency of the dominating group of nematodes made up 93.8-100%. Results show that quantitative and qualitative characteristics of nematodes in the study areas on the Black Sea shelf are heterogeneous. This is due to hydrological conditions. The Bulgarian and Romanian zone have great depths (from 15 to 125m), while 15-45m depths prevail on the Ukrainian shelf. Each shelf has specific sediment type. As observed earlier sediment type and depth determine the quantitative and qualitative characteristics of nematodes. For the Bulgarian and Romanian shelves there is a tendency for increasing diversity from shallows to deep water. On the Ukrainian shelf the species composition of nematodes is higher at small depth. Quantitative characteristics of nematodes increase from the Bulgarian to the Ukrainian shelf. The nematode fauna on the Bulgarian shelf has the greatest species similarity with that the Romanian. Under the influence of river runoff the species diversity is low in those areas of close proximity. In more distant areas the diversity increases. Key species communities are formed under the influence of the abiotic environmental factors and interrelations between organisms. The study of these key communities around which other species assemble is interesting. Sabatieria abissalis dominates among all key species on the Bulgarian shelf transects making up 37-50% of density of colonization. Besides Sabatieria abissalis on the Romanian shelf transects (35% of density), Sabatieria pulchra occurs from 12 to 35%. Sabatieria pulchra dominates on the Ukrainian shelf. Literature data have shown that the ecological niches of these close related species diverge spatially. Sabatieria abissalis prefer to inhabit the upper layers of sediment with adequate oxygen, while Sabatieria pulchra inhabits sediment layers with low oxygen content in silt sediments. At deep water stations where the anthropogenic load is less, k-dominance curves for species biomass and abundance (ABC curves) showing stable unpolluted nematode communities. The amount of dominating species increased with Sabatieria abissalis prevailing. The results of this study illustrate the part played by nematodes in the formation of quantitative parameters of meiobenthos in this area. This kind of meiobenthos is the most suitable for practical biological monitoring of the Black Sea. The increase or decrease in nematode species diversity gives evidence of the state of meiobenthos communities.
DE: 4815 Ecosystems, structure, dynamics, and modeling (0439)
SC: Ocean Sciences [OS]
MN: 2007 Joint Assembly