多不饱和醛是硅藻细胞损伤后分泌的有机毒素, 能够抑制桡足类的生殖和幼体发育, 继而降低浮游动物对硅藻的摄食压力。但是有关多不饱和醛对浮游植物的毒性效应研究较少。选取东海原甲藻(Prorocentrum donghaiense)、双突角毛藻(Chaetoceros didymus)和小普林藻(Prymnesium parvum)进行毒性实验, 将处于指数生长期的藻细胞置于不同浓度的癸二烯醛中, 观察浮游植物在细胞生长及光合作用方面对癸二烯醛的响应, 从而评估多不饱和醛对藻类的影响。结果表明, 浓度为1 mg·L-1的癸二烯醛即可对东海原甲藻产生显著的抑制作用; 当癸二烯醛浓度达到5 mg·L-1时, 东海原甲藻和双突角毛藻细胞的生长以及光合作用均受到极显著抑制; 当癸二烯醛浓度达到10 mg·L-1时, 3种浮游植物的生长完全受到抑制, 细胞密度、Fv/Fm、Yield值以及rETR均在24小时内降至0。研究结果表明, 癸二烯醛显著抑制了浮游植物的生长及光合作用, 但是不同藻类对癸二烯醛的毒性响应存在种间差异。多不饱和脂肪醛的产生有利于硅藻在营养盐缺乏时抑制其它浮游植物的生长, 从而保证自身的生物量积累。
Polyunsaturated aldehydes (PUAs) are cleaved from fatty acid precursors by enzymes activated within seconds of diatom cell wounding. These aldehydes are responsible for a suite of physiological dysfunctions during egg development, hatching and morphogenesis in larvae of copepods, therefore relieving the grazing risks. However, few studies have investigated the allelopathic effect of PUAs on phytoplankton. We explored whether the production of reactive volatile aldehydes can be linked to their ability to cause growth and photosynthesis failure in phytoplankton. Prorocentrum donghaiense, Chaetoceros didymus and Prymnesium parvum were exposed to 2E, 4E-decadienal (DEC) at different concentrations, and the growth and photosynthesis were monitored frequently. We did not find any negative effect of DEC at 0.5 mg·L-1 on the growth and photosynthesis of phytoplankton. However, DEC at 1 mg·L-1 inhibited the cell abundance and Fv/Fm of P. donghaiense but had no effect on C. didymus and P. parvum. The growth and photosynthesis of all three selected phytoplanktons were depressed significantly with DEC at 5 mg·L-1, whereas cell density, Fv/Fm, yield and rETR decreased to 0 with PUAs at 10 mg·L-1. PUAs clearly inhibited the growth and photosynthesis of phytoplankton. However, the response of phytoplankton to PUAs is species-specific. Diatom-derived PUAs can suppress the growth of competitive phytoplankton under nutrition-limited conditions, thereby supporting the biomass accumulation of diatoms.
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