Deblois Charles P, Juneau Philippe
Department of Biological Sciences, TOXEN, Ecotoxicology of Aquatic Microorganisms Laboratory, Université du Québec à Montréal, Succ. Centre-Ville, Montréal, Québec, Canada.
J Phycol. 2012 Aug;48(4):1002-11. doi: 10.1111/j.1529-8817.2012.01191.x. Epub 2012 Jun 25.
Blooms of Microcystis aeruginosa (Kützing) Kützing occur frequently in many freshwater ecosystems around the world, but the role of environmental factors in promoting the growth and determining the proportion of toxic and non-toxic strains still requires more investigation. In this study, four strains (toxic CPCC299 & FACHB905 and non-toxic CPCC632 & FACHB315) were exposed to high light (HL) condition, similar to light intensity found at the surface of a bloom, to evaluate their sensitivity to photoinhibition. We also estimated their capacity to recover from this HL stress. For all strains, our results showed an increased inhibition of the photosynthetic activity with HL treatment time. When comparing the extent of photoinhibition between strains, both toxic strains were more resistant to the treatment and recovered completely their photosynthetic capacity after 3 h, while non-toxic strains needed more time to recover. For toxic strains, the rETR under HL was higher compared to the rETR under low light (LL) control condition despite 50% photoinhibition. This suggests that the detrimental effect of high light (HL; up to 2 h) is outweighed by their higher photosynthetic potential. This conclusion did not stand for non-toxic strains, and indicates their preference for LL environment. We also demonstrated that a LL/HL cycle induced a 259% increase in cell yield for a toxic strain and a decrease by 22% for a non-toxic strain. This also indicates that toxic strains have higher tolerance to HL in a fluctuating light environment. Our data demonstrated that difference of sensitivity to HL between strains can modify the competitive outcome between toxic and non-toxic strains and may affect bloom toxicity.
铜绿微囊藻（库茨）库茨藻华在世界各地的许多淡水生态系统中频繁出现，但环境因素在促进其生长以及决定有毒和无毒菌株比例方面所起的作用仍需更多研究。在本研究中，将四株藻（有毒的CPCC299和FACHB905以及无毒的CPCC632和FACHB315）置于高光（HL）条件下，类似于藻华表面的光照强度，以评估它们对光抑制的敏感性。我们还估计了它们从这种高光胁迫中恢复的能力。对于所有菌株，我们的结果表明，随着高光处理时间的延长，光合活性受到的抑制增加。在比较菌株之间的光抑制程度时，两种有毒菌株对处理的耐受性更强，3小时后完全恢复了光合能力，而无毒菌株需要更多时间才能恢复。对于有毒菌株，尽管有50%的光抑制，但高光条件下的相对电子传递速率（rETR）高于低光（LL）对照条件下的rETR。这表明高光（长达2小时）的有害影响被它们更高的光合潜力所抵消。这一结论不适用于无毒菌株，表明它们更偏好低光环境。我们还证明，低光/高光循环使一种有毒菌株的细胞产量增加了259%，而一种无毒菌株的细胞产量下降了22%。这也表明有毒菌株在波动光照环境中对高光具有更高的耐受性。我们的数据表明，菌株之间对高光敏感性的差异可以改变有毒和无毒菌株之间的竞争结果，并可能影响藻华毒性。
