Preliminary data on free-living marine nematode distribution in the northern part of the Sea of Japan

Natalia P. FADEEVA, Natalia L. DEMCHENKO

Far East State University, Vladivostok, 690600, Russia, nfadeeva@mail.primorye.ru

The northern part of the Sea of Japan is the most productive and sensitive to modern negatative anthropogenic activity zone. Qualitative samples of meiobenthos were collected during expedition to Tatarskyi Strait from June to August 2001 from the depth of 12-160 m. Nematofauna abundance ranged from 2 to 1350 individuals per 10 cm² in Tatarskyi Strait and 278-933 individuals per 10 cm² in Chichacheva Bay. The taxonomic list of species of free-living marine nematodes of northern part of the Sea of Japan includes about 80 species. Nematodes of the genus Setosabatieria, Metasphaerolaimus, Neotonchoides, Camacolaimus, Leptolaimus, Prochaetosoma and other are recorded for the first time in this region. Nematode communities were identified using classification and ordination techniques. The identified communities were characterized in connection with species composition, density, diversity, size structure and feeding type. Deposit feeders (80%) were most dominant in all communities followed by omnivore/predators, that is explained by the muddy nature of the sediment. Epistrate feeders had the lowest abundance (11%). Contemporary status and anthropogenic impact tendencies in the coastal nematofauna are described. Main anthropogenic factors impacting the habitats of these animals are determined.

Biodiversity of Free Living Marine Nematodes From Tropical Brazilian Ecosystems

Verônica da FONSÊCA- GENEVOIS¹, Nic SMOL², Virág VENEKEY¹, Alessandra Prates BOTELHO¹

¹Departmento de Zoologia, Universidade Federal de Pernambuco, Av. Prof. Moraes Rêgo s/n, Cidade Universitária, 50000-000, Recife-PE, Brasil, meiofaunabrasil@hotmail.com

²PINC, University of Gent, Ledeganckstraat, 35; B-9000, Gent, Belgium, nic.smol@UGent.be

Free living aquatic nematodes from Brazil were described for the first time in 1950s by Gerlach (1954; 1956a, b; 1957a, b). These papers represented an important taxonomic contribution as 113 new species were described. Only since the 90s the free-living aquatic nematodes from Brazil were again studied by Brazilian researchers from different institutes, such as Medeiros (1997), Moellmann (2003), Pinto (2003) at the South and Southeast areas of Brazil. In this work a great variety of tropical ecosystems, most of them from North and Northeast of Brazil were considered, such as sandy beaches (Bezerra, 2000), salt ponds (Silva, 2001), Roccas atoll (Netto, 1999), estuaries (Rodrigues, 2002; Castro, 2003), tidal (Esteves, 2002), beach-rocks (Maranhão, 2003), upwelling region (Fonsêca-Genevois, 2001; Santos, 2002; Nunes, 2003) and algae banks (Da Rocha, 2003). Considering nematodes spatial distribution to-day a list of 203 nematode genera were registered, within them 125 are new records to Brazil. Only the genera Daptonema, Spirinia and Theristus were common to all the ecosystems. The highest number of nematode genera was found at the unique upwelling region of the Brazilian coast.

Marine nematode assemblages and zonation patterns on European (un)disturbed sandy beaches

Tom GHESKIERE, Steven DEGRAER, Magda VINCX

Marine Biology Section, Biology Department, Ghent University, Gent, Belgium, tom.gheskiere@UGent.be

The European coastline consists for more than 30 % of sandy beaches. In spite of their rather barren and desert-like view, these sandy coastlines harbour a highly diverse fauna and flora. On the other hand these beaches are subjected to strong anthropogenic pressure (e.g. pollution, eutrophication, coastal fisheries and tourism), which has substantial impact on the interstitial life and functioning of the sandy beach ecosystem. In contrast to the well-documented tropical sandy beaches, little is known about the structural and functional diversity of the different benthic components. This study aims to get an idea about the structural and functional diversity of the free-living marine nematodes of three European sandy beaches (i.e. Belgium, Poland and Italy). Nematodes are very suitable for monitoring and are used in the second part of this study to compare and evaluate the diversity between "disturbed" and "undisturbed" sandy beaches. In order to document the structural and functional diversity of the nematofauna of the above-mentioned beaches, quantitative samples along transects have been collected on both disturbed and undisturbed parts of the beaches. Nematodes species were processed and identified at species level and further analysed by means of statistical and multivariate techniques. Around 250 species of free-living marine nematodes in total have been recognized on these beaches of which several species are new to science. Nematode zonation patterns, in close relation with the morphodynamics of the beaches, have been detected as well.

The seasonal changes of free-living nematodes from the deep part of the White Sea

Maria A. MILJUTINA

Department of Biology, Moscow State University, Moscow 119899, Russia, dmilutin@mtu-net.ru

Seasonal changes in quantity, diversity and distribution of free-living nematodes were described for deep part of the White Sea at the depth of 270 m. Nematodes were collected in July and October, 1998, in May and November, 1999. Nematodes were the most abundant group among other metazoans (about 70% of all metazoans). The rate of nematodes in spring and summer was about 65%, while in autumn and winter - 74%. The maximum density of nematodes was found in October (825000 specimens per m² within 5-cm columns of sediment). Vertical distribution in sediments varied in seasons too. In May and July the most of nematodes concentrated in upper fist centimeter of sediment, in October and November - in the second centimeter. Four species of nematodes: Sabatieria ornata, Filipjeva filipjevi, Microlaimus sp. and Sphaerolaimus gracilis, were the most numerous in all samples. The dominating species differed from season to season because of great seasonal changes in Sabatieria ornata abundance (the number of specimens per 1 m² in July was 160191, in October - only 19108). Abundance of other numerous species changed less. However a peak of quantity of Microlaimus sp. and Sphaerolaimus gracilis (in July) occurred too. Filipjeva filipjevi had two peaks of high abundance - in July and in November. (INTAS grant No. 96-1359).

Nematode community structure in Vrangel Bay (Nakhodka Bay, Sea of Japan)

Olga N. PAVLYUK¹, Yulia A. TREBUKHOVA¹, Vladimir M. SHULKIN²

¹Institute of Marine Biology FEB RAS, Vladivostok, 690041, Russia, opavlyuk@imb.dvo.ru

²Pacific Institute of Geography FEB RAS, Vladivostok, 690041, Russia

One of the largest deep-water ports in Russia is situated in Vrangel Bay. Since 1973 till the present time the bottom dredgings are being carried out there. In 1989 and 1995 the structural changes in the soft bottom communities were studied with the exception of meiofauna. In 2001 there was conducted a study of meiobenthos and its main group - free-living marine nematodes. The main aim of this research was to investigate the species composition and quantitative distribution of nematode community structure according to the grain size composition and sediment concentrations of heavy metals. The soft bottom meiofauna in Vrangel Bay was dominated by nematodes (50-80%). Density of nematode population was higher in muddy sediments than in muddy sands. On the whole, 48 nematode species were found. Dorylaimopsis peculiaris, Viscosia stenostoma, Axonolaimus seticaudatus, Metasphaerolaimus japonicus and Pseudosteineria inaequispiculata were dominated in sandy sediments, while muddy sediments were dominated by Sabatieria pulchra, S. palmaris, Metalaimus pumilus, Sphaerolaimus limosus and Oncholaimium ramosum. There was found an insignificant correlation between the abundance of two species (S. pulchra, S. palmaris), grain size composition and concentrations of lead. However, metal concentrations determining in Vrangel Bay were not high enough to influence on species composition and community structure of nematodes.

Nematode communities from the Vostok Bay (Sea of Japan)

Olga N. PAVLYUK, Yulia A. TREBUKHOVA

Institute of Marine Biology FEB RAS, Vladivostok, 690041, Russia, opavlyuk@imb.dvo.ru

Nematode communities were studied in relation to the sediment granulometry in Vostok Bay (Peter the Great Bay). There were found 8 types of the bottom sediments. In general, nematode diversity and total abundance were regulated by sediment granulometry. The greatest nematode population density was found in fine-grained sand (130 thousands specimens/m²). Extremely low abundance was recorded in fine gravel with an admixture of mixed-grained sand (10 thousands specimens/m²). In total, 89 nematode species were found at all stations in Vostok Bay. The species diversity indices were the highest in silted medium fine-grained sand (H=4.9; e=2.5). In this biotope we registered 64 nematode species totally. The following species were dominated there: Metachromadora itoi, Dorylaimopsis peculiaris, Viscosia stenostoma, Phanoderma platonovae and Axonolaimus seticaudatus. The lowest species diversity indices (H=1.49; e=0.76) were  recorded in fine gravel with an admixture of mixed-grained sand, dominated by Dorylaimopsis peculiaris and Axonolaimus seticaudatus. There were found only 4 species. One should notes the structure of nematode communities from Gaydamak Bay, which is situated in Vostok Bay. The bottom sediments are represented there by heterogeneous silt and characterized by high concentrations of heavy metals and petroleum hydrocarbons. A number of the nematode species was impoverished and submitted by the one species, Oncholaimium ramosum. O. ramosum can tolerate the whole range of organic contaminants, which are not toxic and may be used for nutrition. At the exit from the bay the composition of the species was more varied. Thus, changes in nematode communities were correlated with the sediment structure and, in the case with Gaydamak Bay, with high concentrations of heavy metals and petroleum hydrocarbons.

A comparison of the nematode communities associated with cold-water and tropical coral rubble

Maarten RAES¹, Johan KEMPS², Ann VANREUSEL³

Marine Biology Section, Ghent University, 9000 Gent, Belgium, ¹maarten.raes@UGent.be, ²johan.kemps@UGent.be, ³ann.vanreusel@UGent.be

The great variety of species in local areas of coral reefs is legendary, although huge differences in local and regional biodiversity do occur. Recently, much attention is going to the description of the composition and dynamics of faunal communities associated with cold-water corals (mainly Lophelia pertusa (Linnaeus, 1758)). Logically, these coral communities should be subject to analogous processes that result in high habitat complexity (and therefore higher biodiversity) in tropical coral reefs. It was already suggested for macro- and megafauna that cold-water corals rival their tropical counterparts in terms of species richness and diversity. For the first time ever, attention goes to the meiofauna associated with cold-water coral rubble and associated substrates (sponge skeletons of Aphrocallistes bocagei Schultze, 1886) from the Porcupine Seabight (North Atlantic). The nematode community is discussed in terms of biodiversity, community structure and preferences for the different substrate types. This information is compared with that of the community associated with tropical coral rubble from the South Kenya coast, an area with very different environmental conditions. Despite of these enormous differences, some parallels between the 2 communities could be drawn. In this context, the role of the 2 closely related families of epifaunal nematodes Epsilonematidae and Draconematidae is striking: although seldom found in deep-sea environments, these two families were represented by a large number of individuals on cold-water coral rubble from a depth of 1005 m.

Nematode population in a detached kelp accumulation in the White Sea

Alexey V. TCHESUNOV¹, K.A. FILIPPOVA¹, Vadim O. MOKIEVSKY²

¹Department of Invertebrate Zoology, Faculty of Biology, Moscow State University, Moscow, Russia, tchesunov@mtu-net.ru

²P. P. Shirshov Institute of Oceanology, Russian Academy of Sciences, Moscow, Russia

Nematodes were studied in a long-term accumulation of detached kelp situated at depth 18 m near Karelian Coast. The stack consists of fronds of brown algae Laminaria and Alaria originating from a belt of growing plants hereabouts. The stack was tens meters both long and wide and 2 m high. Upper layer of the stack was well aerated and formed by fresh and even living fronds. Middle layer was anoxic and made up by small pieces of thallii covered by cyanobacteria. Bottom layer was anoxic black semi-liquid organic material. There were totally 40 nematode species found in the accumulation. Living detached algae support nematode community with dominant species normally inhabitating alive macrophytes in the sublittoral zone of the White Sea. Nematode community in dead algae at various stages of decomposition is characterized by strong dominance of bacterivorous Geomonhystera sp. and low percentages of other phytal and benthic species. Geomonhystera sp. is related to common G. disjuncta but differs by much larger size and viviparity. Generally, the nematode diversity decreases and the total nematode abundance increases along the stages of plant decomposition. (RFBR grant No. 03-04-49152).

Nematode population in the coastal seasonal ice of the White Sea

Alexey V. TCHESUNOV*, Darja A. PORTNOVA

¹Department of Invertebrate Zoology, Faculty of Biology, Moscow State University, Moscow, Russia, *tchesunov@mtu-net.ru

Abundant nematode populations have been registered in the coastal seasonal ice in Kandalaksha Bay of the White Sea. Ice as a continuous covering appears to the end of November and lasts about six months growing up to 1-1.5 m thick. Ice disappears entirely in the beginning of June. First nematodes were observed in December or in January. Total abundance of nematodes increases gradually from January to May. Almost all specimens were always confined to the lower layer of the ice blocks. This nematode population is significantly more diverse than one in drifting ices of the open Arctic Ocean. The community includes Theristus melnikovi and Cryonema crassum, both known as specific inhabitants of the drifting Ocean ice. Both species are represented by all juvenile and adult stages. C. crassum is documented to have egg clutches with developing embryos within ice. A significant portion of the nematode community is made up by other three or four species of the family Monhysteridae. The latter are not yet identified because they are represented only by juvenile specimens. With melting ice, the ice-dwelling nematodes disappeared. Theristus melnikovi, Cryonema crassum and other ice-dwelling Monhysteridae were found in summer and autumn seasons neither in bottom sediments nor in fouling in that area. (RFBR grant No. 03-04-49152).

© Russian Society of Nematologists, Institute of Marine Biology FEB RAS, 2002