Killing potential protist predators as a survival strategy of the newly described dinoflagellate Alexandrium pohangense |
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| Institution: | 1. School of Earth and Environmental Sciences, College of Natural Sciences, Seoul National University, Seoul 08826, Republic of Korea;2. Advanced Institutes of Convergence Technology, Suwon 16229, Gyeonggi-do, Republic of Korea;3. Department of Marine Biotechnology, Kunsan National University, Jeonbuk 54150, Republic of Korea;1. Department of Marine Sciences, University of Connecticut, 1080 Shennecossett Road, Groton, CT 06340, USA;2. National Oceanic and Atmospheric Administration, National Marine Fisheries Service, Northeast Fisheries Science Center, Milford Laboratory, 212 Rogers Avenue, Milford, CT 06460, USA;1. Library of Marine Samples, Korea Institute of Ocean Science and Technology, Geoje 656-830, Republic of Korea;2. South Sea Institute, Korea Institute of Ocean Science and Technology, Geoje 656-830, Republic of Korea;3. Department of Life Science, Hanyang University, Seoul 133-791, Republic of Korea;4. Pukyung National University, Busan 608-737, Republic of Korea;5. National Fisheries Research and Development Institute, Busan 619-705, Republic of Korea;6. Korea Basic Science Institute, Jeju 690-140, Republic of Korea;1. School of Earth and Environmental Sciences, College of Natural Sciences, Seoul National University, Seoul 151-747, Republic of Korea;2. Advanced Institutes of Convergence Technology, Suwon, Gyeonggi-do 443-270, Republic of Korea;3. Biological Institute, Section of Marine Biology, University of Copenhagen, Universitetsparken 4, DK-2100 Copenhagen K, Denmark;1. Graduate School of Fisheries Sciences, Hokkaido University, 3-1-1 Minato-cho, Hakodate, Hokkaido 041-8611, Japan;2. Tokyo Institute of Technology, School of Environment and Society, 2-12-1-M1-4 Ookayama, Meguro, Tokyo 152-8552, Japan;3. National Research Institute of Fisheries Science, 2-12-4 Fukuura, Kanazawa, Kanagawa 236-8648, Japan;4. Australian Antarctic Division,203 Channel Highway, Kingston, Tasmania, 7050, Australia;1. School of Earth and Environmental Sciences, College of Natural Sciences, Seoul National University, Seoul 08826, Republic of Korea;2. Advanced Institutes of Convergence Technology, Suwon, Gyeonggi-do, 16229, Republic of Korea;3. Brain Korea 21, School of Earth and Environmental Sciences, College of Natural Sciences, Seoul National University, Seoul 08826, Republic of Korea;1. School of Earth and Environmental Sciences, College of Natural Sciences, Seoul National University, Seoul 08826, Republic of Korea;2. Advanced Institutes of Convergence Technology, Suwon, Gyeonggi-do, 16229, Republic of Korea;3. Water and Eco-Bio Corporation, Kunsan National University, Kunsan 54150, Republic of Korea;4. Department of Marine Biotechnology, Kunsan National University, Kunsan 54150, Republic of Korea;5. Marine Biodiversity Institute of Korea, Seochun-gun, Chungchungnam-do, 33662, Republic of Korea |
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| Abstract: | Blooms caused by some species belonging to the dinoflagellate genus Alexandrium are known to cause large-scale mortality of fish. Thus, the dynamics of these species is important and of concern to scientists, officials, and people in the aquaculture industry. To understand the dynamics of such species, their growth and mortality due to predation need to be assessed. The newly described dinoflagellate Alexandrium pohangense is known to grow slowly, with a maximum autotrophic growth rate of 0.1 d?1. Thus, it may not form bloom patches if its mortality due to predation is high. Therefore, to explore the mortality of A. pohangense due to predation, feeding on this species by the common heterotrophic dinoflagellates Gyrodinium dominans, Gyrodinium moestrupii, Luciella masanensis, Noctiluca scintillans, Oxyrrhis marina, Oblea rotunda, Polykrikos kofoidii, and Pfiesteria piscicida, as well as by the ciliate Tiarina fusus, was examined. None of these potential predators was able to feed on A. pohangense. In contrast, these potential predators were killed and their bodies were dissolved when incubated with A. pohangense cells or cell-free culture filtrates. The survival of G. moestrupii, O. marina, P. kofoidii, and T. fusus on incubation with 10 cells ml?1 of A. pohangense was 20–60%, while that at the equivalent culture filtrates was 20–70%. With increasing A. pohangense cell-concentration (up to 1000 cells ml?1 or equivalent culture filtrates), the survival rate of G. moestrupii, O. marina, P. kofoidii, and T. fusus rapidly decreased. The lethal concentration (LC50) for G. moestrupii, O. marina, P. kofoidii, and T. fusus at the elapsed time of 24 h with A. pohangense cells (cultures of 11.4, 13.3, 1.6, and 3.3 cells ml?1, respectively) was lower than that with A. pohangense filtrates (culture filtrates of 35.5, 30.6, 5.5, and 5.0 cells ml?1, respectively). Furthermore, most of the ciliates and heterotrophic dinoflagellates in the water collected from the coast of Tongyoung, Korea, were killed when incubated with cultures of 1000 A. pohangense cells ml?1 and equivalent culture filtrates. The relatively slow growing A. pohangense may form blooms by reducing mortality due to predation through killing potential protist predators. |
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| Keywords: | Allelopathy Harmful algal bloom Feeding Filtrate Graze Red tide |
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