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Workshop -International Cooperation on Investigation and Reseaich of Manne Natuial Kesource ano l:nvtlonnienl-^ COMPOSITION AND DIVERSITY OF FREE LIVING MARINE NEMATODE ASSEMBLAGES IN THE WEST SEA, VIETNAM N)»n Xuan Ouang ''^''',Ann Vanreusel^ Nic Smol^, Nguyen Ngoc Chau*, Nguyen Vu Thanh^ ; Department of Environmental Management and Technology, Institute of Tropical Biology 85 Tran Quoc Toan, District 3, Ho Chi Minh city, Vietnam (*) Corresponding author E-mail: nxquang@scientist.com Marine Biology Section, Biology Department, Ghent University, Krijgslaan 281 S8 B-9000 Ghent, Belgium Postgraduate Inlemational Nematology Course, Vakgroep Biologie, Ledeganckstraat 35, B-9000 Gent, Belgium Department of Nematology, Inslitute of Ecology and Biological Resources, Vietnamese Academy of science and Technology 18 Hoang Quoc Viet, Cau Giay, Hanoi, Vietnam Abstract: The structure of.free living marine nematode assemblages in the West Sea, Vietnam was firstly carried out in October 2007 The objectives of this research are originally lo find out the composition, densities and biodiversity of the nematode communities in The West Sea The primitive results of research from sampling stations showed that 93 genera of 22 families, orders of phylum Nematoda were recorded lo present in this area In nematode communities of West Sea, order Monhysterida present as highest dominant in the number of genera (27 genera or 29% of total) Chromadorida are also high with 15 genera (or 16.1% of total), Triplonchida is lowest number of genus in the communities Genera Daplonema develop dominantly in two stations T2 and T5 In the other stations, this position was replaced by Thalassomonhystera in Tl, Terschellingia in T3, Vasostoma in T4, Gomphionema in T6 and Neochromadora in T7 Genera richness ranges from 11-44 genera and densities range 40 -180 inds/100 gram sediment In each sampling stations, number of genera and densities are not equal, they went high in some stations as T2, T3 and T6, T7 but fell lowest in station T4 The nematode assemblages seems increase densities from the East to the West The biodiversity indices as Margalef (d), Shcmon - Weiner (H) were calculated lo show a scenario with high diversity in which d index ranging from 2.84 4.81 and H'ranging from 2.71 - 8.26 I Introduction Researches on nematode assemblages in the sea along the coast like Kenji Kito (1982), Magda (1985, 1990), Magda et al (1990), and many publications of free living marine nematode in Vietnam as Doan Canh and Nguyen (2000); Lai et al Ngo Xuan Quang Hpi thao khoa hoc - Hpp tac Quflc tg digu tra nghign cim tai nguygn va mfli tnrflng bign (2005); Nguyen & Nguyen (2004); Nguyen & Gagarin (2004a); Gagarin & Nguyen (2004b), Gagarin and Nguyen (2005), But there is no publication mentioning about nematode assemblages in the West Sea of Vietaam The West Sea is the sea area in the South-West Vietnam, partly belonging to Gulf of Thailand, along the coast of provinces Ca Mau and Kien Giang, Vietnam Recently, the catching, aquaculture, economic activities in coastal provinces as Ca Mau, Kien Giang have a number of the impacted to benthic marine environment This paper just aims to present an original general scenario of the Nematode community in sampling field from offshore of Ca Mau coast to near Phu Quoc Island Material and Methods Sampling field trip: Nematode samples were collected in the October 2007 in the West Sea along the coast of provinces Ca Mau and Kien Giang toward from the East to the West (The coordinates and sampling map in the Fig 1) ^ ^ ^ Coordinates y X «.«Sai.i Tl T2 T3 T4 T5 T6 T7 104.376082 104.669925 104.765749 104.775999 104.494044 104.501178 104.455861 8.727778 8.834485 9.00032 9.336494 9.503449 9.99921 10.210765 Tab 1: The coordinates of sampling stations Fig 1: Sampling map Samples collected from boat using a Ponar grab, which weighs 13.7 kg and cover a surface area of 230mm by 250mm The grab is 150mm high In each station one grab was collected subsample for nematode analysis The samples were taken at each station about 100 gram of sediment was collected, no replication took place since it was focused on the qualitatively characterization of the community composition All samples were fixed in hot formalin 4% at 60°C Samples were sieved through a 38 pm mesh and extracted by flotation with Ludox-TM50 (specific gravity of 1.18) Each time, 200 nematodes were used for making slides and identification All nematodes were identified to genus level using a high magnification microscope Olympus BX41, BX5I and with the helps of the taxonomy literatures for identification nematode of Wieser (1956, 1959); Ngo Xuan Quang 393 Workshop- "Intemational Cooperation on Investigation and Research of Marine Natural Resource and Environment" Plan and Warwick (1983); Piatt and Warwick (1988); Warwick, Piatt and Somerfield, (1998) and Lorenzen (1994) Data analyses Data were analyzed using univariate and multivariate techniques The abundance, composition, Margalef diversity, Shannon-Wiener diversity (logj) Hill's (1973) diversity numbers of the order 0, I, and
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