College of Oceanography, Hohai University, 1 Xikang Road, Nanjing, 210098, China; Jiangsu Key Laboratory for Biodiversity and Biotechnology, School of Biological Sciences, Nanjing Normal University, 1 Wenyuan Road, Nanjing, 210023, China.
Jiangsu Key Laboratory for Biodiversity and Biotechnology, School of Biological Sciences, Nanjing Normal University, 1 Wenyuan Road, Nanjing, 210023, China.
Chemosphere. 2019 Feb;216:203-212. doi: 10.1016/j.chemosphere.2018.10.116. Epub 2018 Oct 18.
Morphological defense is assumed to be an effective anti-grazer strategy in phytoplankton. Scenedesmus obliquus, a globally widespread freshwater chlorophyte, can form colonies in response to the infochemicals of herbivorous zooplankton and survive in coexistence with grazers. However, the inducible defense response is often disturbed by abiotic or biotic factors, especially under the increasing global warming and environmental pollution. In this study, two nonlethal environmental factors, namely, elevated temperature and environmentally relevant Zn concentrations, decreased colony formation of S. obliquus induced by Daphnia grazing infochemicals. Elevated temperature (30 °C) reduced the inducible colony size and shortened the maintenance time of defensive colonies. Decreased colony size was detected with increased Zn concentration. Colony formation was inhibited even at low Zn concentration (0.131 μmol L), which neither retarded growth nor affected photosynthesis. Warming promoted the inhibition effect of Zn on inducible colony formation of S. obliquus. Warming also enhanced Zn toxicity, which caused the growth rate of S. obliquus to be hindered by high Zn concentrations at elevated temperature. Specially, S. obliquus which formed inducible colonies under the condition of Daphnia infochemicals had higher tolerance to Zn toxicity and thus likely exerted protective effects against heavy metals. The results indicated the combined effects of global warming and heavy-metal pollution result in more severe impact on the inducible defense of S. obliquus.
形态防御被认为是浮游植物应对食草动物的一种有效策略。斜生栅藻是一种广泛分布于全球的淡水绿藻，能够对草食性浮游动物的信息素做出反应形成群体，从而与食草动物共存。然而，诱导防御反应常常受到非生物或生物因素的干扰，特别是在全球变暖和环境污染加剧的情况下。在这项研究中，两种非致死性环境因素，即高温和环境相关浓度的 Zn，降低了桡足类动物放牧信息素诱导的斜生栅藻群体的形成。高温（30°C）降低了诱导形成的群体大小，并缩短了防御性群体的维持时间。随着 Zn 浓度的增加，检测到群体大小减小。即使在低 Zn 浓度（0.131 μmol/L）下，群体形成也受到抑制，而这种浓度既不会减缓生长，也不会影响光合作用。变暖促进了 Zn 对斜生栅藻诱导群体形成的抑制作用。变暖还增强了 Zn 的毒性，导致在高温下高 Zn 浓度会阻碍斜生栅藻的生长速率。特别是在桡足类动物信息素条件下形成诱导群体的斜生栅藻对 Zn 毒性的耐受性更高，因此可能对重金属表现出保护作用。研究结果表明，全球变暖和重金属污染的综合影响对斜生栅藻的诱导防御产生了更严重的影响。
