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Harmful algal blooms: mechanisms, monitoring, and prevention in a rapidly changing world
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The emerging threat of toxic microalgae Coolia spp. in Hong Kong waters
P-B1-15
Meng Yan* , State Key Laboratory in Marine Pollution, City University of Hong Kong, Hong Kong, China; Research Centre for the Oceans and Human Health, City University of Hong Kong Shenzhen Research Institute, Shenzhen, China
Priscilla T.Y. Leung, State Key Laboratory in Marine Pollution, City University of Hong Kong, Hong Kong, China; Research Centre for the Oceans and Human Health, City University of Hong Kong Shenzhen Research Institute, Shenzhen, China
Jiarui Gu, State Key Laboratory in Marine Pollution, City University of Hong Kong, Hong Kong, China; Department of Chemistry, City University of Hong Kong, Hong Kong, China
Xin Li, State Key Laboratory in Marine Pollution, City University of Hong Kong, Hong Kong, China; Department of Chemistry, City University of Hong Kong, Hong Kong, China
Veronica T.T. Lam, State Key Laboratory in Marine Pollution, City University of Hong Kong, Hong Kong, China
Tak-Cheung Wai, State Key Laboratory in Marine Pollution, City University of Hong Kong, Hong Kong, China; Research Centre for the Oceans and Human Health, City University of Hong Kong Shenzhen Research Institute, Shenzhen, China
Sam K.F. Yiu, State Key Laboratory in Marine Pollution, City University of Hong Kong, Hong Kong, China
Paul K.S. Lam, State Key Laboratory in Marine Pollution, City University of Hong Kong, Hong Kong, China;Research Centre for the Oceans and Human Health, City University of Hong Kong Shenzhen Research Institute, Shenzhen, China; Department of Chemistry, City University of Hong Kong, Hong Kong, China
Presenter Email: mengyan@cityu.edu.hk |
| The emerging threat of benthic and epiphytic toxic algae (BETA) to marine ecosystems has attracted worldwide attention. Seawater temperature is one of the major factors influencing the growth and distribution of BETA. Coolia are one of the cosmopolitan group of BETA, and are potentially toxic. There are four species of Coolia reported in Hong Kong waters, i.e., C. malayensis, C. canariensis, C. tropicalis, and C. palmyrensis. This study have examined the potential toxicities of these four species of Coolia, with particular focus on the toxic effect of algal extracts on the lethality of Artemia larvae and hemolysis rate on erythrocytes of local reef fishes. Our results showed that the lipid-soluble fraction of the extracts were lethal to Artemia larvae, with C. malayensis causing the highest mortality rate among the four. The water-soluble extracts from all the four Coolia spp. have induced significant hemolysis in ten species of reef fish. In-depth comparative study on physiological and molecular responses, toxicity, and toxin production under treatment of different seawater temperatures were performed for two selected species, i.e., C. malayensis (a tropical species) and C. canariensis (a temperate species). Coolia monocultures were exposed to seven temperatures i.e., 16, 18, 20, 22, 24, 26 and 28 degree C before sampled for determinations of growth curves, photosynthesis efficiency, amount of phaeo-pigments, toxicity, toxin levels, plus elucidation with transcriptional responses. Coolia malayensis showed the best growth under 24 degree C while its photosynthesis was steady across the range of temperatures. The growth rate of C. canariensis was peaked at 20 degreeC. Lower temperatures, i.e., 16 and 18 degree C inhabited its growth and photosynthesis. The amount of phaeo-pigments reached the highest at 26 degree C for both C. malayensis (3.06 ug/ml) and C. canariensis (15.61 ug/ml), but the level reached the lowest at 20 degree C for C. malayensis (0.90 ug/ml) and at 16 degree C for C. canariensis (2.76 ug/ml). The 48h LC50 values of C. malayensis on lethality of Artemia larvae decreased as temperature increased, indicating the algae being more toxic under higher temperatures. The okadiac acid (OA) analogue was detected in the lipid-soluble extracts of C. malayensis using LC-MS/MS analysis, and the relative amounts detected were significantly correlated to their toxicities. With more upcoming results on toxin analysis and transcriptome profiles, we could gain further insight on possible mechanisms that associated with algal growth and toxin production with respect to the temperature effect. |
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