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Harmful algal blooms: mechanisms, monitoring, and prevention in a rapidly changing world
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Population genetic structure of domoic acid producing diatom Nitzschia navis-varingica (Bacillariophyceae) in the Western Pacific region
Wednesday 9th @ 1130-1150, Multifunction Hall
Suh Nih Tan* , Bachok Marine Research Station, Institute of Ocean and Earth Sciences, University of Malaya
Chui Pin Leaw, Bachok Marine Research Station, Institute of Ocean and Earth Sciences, University of Malaya
Haifeng Gu, Third Institute of Oceanography, Xiamen
Changping Chen, School of Life Sciences, Xiamen University
Yuichi Kotaki, School of Marine Biosciences, Kitasato University
Yahui Gao, School of Life Sciences, Xiamen University
Chunlei Gao, Research Center of Marine Ecology, First Institute of Oceanography, Qingdao
Hong Chang Lim, Tunku Abdul Rahman University College
Sing Tung Teng, Faculty of Resource Science and Technology, Universiti Malaysia Sarawak
Po Teen Lim, Bachok Marine Research Station, Institute of Ocean and Earth Sciences, University of Malaya
Presenter Email: danielle_tsn0421@hotmail.com |
| Nitzschia navis-varingica is a pennate diatom that widely distributed in the Western Pacific region. This species, like some species of Pseudo-nitzschia, produces domoic acid (DA) and the isomers. While DA is known to be responsible for Amnesic Shellfish Poisoning (ASP) by Pseudo-nitzschia in marine mammals and humans, no poisoning cases have been related to N. navis-varingica thus far. Previous studies have demonstrated wide distributions of N. navis-varingica in the tropical and subtropical mangrove areas of Western Pacific. However, genetic relationships among the populations throughout this large geographic locality have not been assessed. In this study, a total of 322 strains of N. navis-varingica were isolated and identified based on the frustule morphology by electron microscopy and genetic characterization of the nuclear large subunit ribosomal gene (LSU rDNA). The LSU rDNA data set revealed high sequence homogeneity among all strains examined (0 to 0.9%). To understand the population dynamics of N. navis-varingica in the Western Pacific region, genetic diversity of N. navis-varingica was investigated using the ITS2 rDNA marker. The ITS2 phylogenetic inferences identified eight distinct clades, with high sequence heterogeneity ranging from 0.5 to 9.7%; analysis of haplotype diversity recovered 44 haplotypes. Our results showed strong gene flow among N. navis-varingica populations in the Western Pacific region (AMOVA, total percentage of variation = 0.48095). However, isolates from Vietnam and Japan formed a distinct haplotype H3 (FST, 0.4 to 1.00) suggesting possible genetic structuring between the water bodies of northwestern Pacific and the South China Sea (SCS). It is speculated that ocean current circulations (e.g. SCS currents and Kuroshiro current) may play a role in this allopatric differentiation of N. navis-varingica.
Keywords: N. navis-varingica; DA; LSU rDNA; ITS2 rDNA; Population structure
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