Allelopathic effects of mixotrophic dinoflagellate Akashiwo sanguinea on co-occurring phytoplankton: the significance of
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Allelopathic effects of mixotrophic dinoflagellate Akashiwo sanguinea on co-occurring phytoplankton: the significance of nutritional ecology* YANG Yeyin1, #, HUANG Bozhu1, 2, #, TANG Yingzhong3, XU Ning1, ** 1
Department of Ecology/Key Laboratory of Eutrophication and Red Tide Prevention of Guangdong Higher Education Institutes,
2
Guangdong Environmental Monitoring Center, Guangzhou 510308, China
Jinan University, Guangzhou 510632, China 3
Key Laboratory of Marine Ecology and Environmental Sciences, Institute of Oceanology, Chinese Academy of Sciences, Qingdao 266071, China
Received Mar. 25, 2020; accepted in principle May 5, 2020; accepted for publication May 21, 2020 © Chinese Society for Oceanology and Limnology, Science Press and Springer-Verlag GmbH Germany, part of Springer Nature 2020
Abstract Blooms of Akashiwo sanguinea frequently break out around the world, causing huge economic losses to the aquaculture industry and seriously damaging coastal ecosystems. However, the formation mechanisms of A. sanguinea blooms remain unclear. We investigated the allelopathic effects of A. sanguinea on multiple phytoplankton species, explored the mode of allelochemicals action and the way of nutrient factors regulation of the allelopathic activity. Results show that strains of A. sanguinea could inhibit the growth of co-occurring phytoplankton including Scrippsiella trochoidea, Phaeocystis globosa, and Rhodomonas salina, but inhibition of Prorocentrum micans was not obvious. The inhibition rates on phytoplankton were positively correlated with the cell densities of A. sanguinea. The highest inhibition rate of 94% on R. salina was for A. sanguinea CCMA256 culture of 2 000 cells/mL at 72 h. We observed that cells of S. trochoidea, Ph. globosa, and R. salina were lysed when co-cultured with A. sanguinea, with the shortest time for S. trochoidea. Additionally, the growth rates of A. sanguinea were promoted by coculturing with S. trochoidea, Ph. globosa, and R. salina. Four components of A. sanguinea culture were all able to inhibit growth of R. salina: the strongest inhibitory effect was found in the sonicated culture, followed by whole-cell culture, filtrates of sonicated culture, and filtrate culture. The crude extract of A. sanguinea culture also lysed cells of R. salina, and the inhibition rates on R. salina increased with the increasing dose of crude extract. It was shown that both nutrient enrichment and nitrogen꞉phosphorus ratio imbalance enhanced remarkably the allelopathic activity of A. sanguinea. The highest inhibition rate on R. salina of 70% occurred in A. sanguinea JX13 treatment at 2 000 cells/mL under high nutrient condition in 48 h. In JX14 treatment at 2 000 cells/mL for N꞉P of 10꞉1, the inhibition rate increased by 1.7 times of that for N꞉P of 20꞉1. In addition, the allelopathy of A. sanguinea could not only be a competitive strategy but also a nutrition strategy, playing an important role in formation and/or maintenance of blooms of the mixotrophic dinoflagellate A. sanguinea. Keyword: Akashiwo sanguinea; h
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