云南高山湖泊浮游甲壳动物对紫外辐射的适应机制

Strong ultraviolet (UV) radiation can make a negative impact on aquatic organisms, and aquatic organisms will produce different adaptive performance to ultraviolet radiation. Previous studies demonstrated that crustacean zooplankton can adapt to underwater ultraviolet radiation through diel vertical migration (DVM) or accumulation of UV protective compounds. The latter mechanism was often reflected in the process of the lab experiment, and it is still unclear whether this mechanism exit in the natural lakes. Our preliminary investigation showed that crustacean zooplankton containing UV protective compounds still have DVM behavior. Thus, we make a hypothesis that the crustacean zooplankton containing UV protective compounds may not be enough to prevent the damage from ultraviolet radiation of surface layer in lakes with higher ultraviolet radiation, and have to rely on DVM to adapt to UV radiation of surface layer. We select the alpine lakes in Yunnan as the study site and combine the methods of field investigation and simulation experiments. Based on the investigation of DVM behavior of crustacean zooplankton, we will analyze its relationship with environmental factors and the UV protective compounds. We also judge the impact of UV radiation on crustacean zooplankton containing the UV protective compounds through the simulation experiments. Our aim will reveal the adaptation mechanisms of crustacean zooplankton to UV radiation. The obtained results will lead to better understanding of the effect of the global increase in UV radiation on crustacean zooplankton.

强紫外辐射会对水生生物产生不利的影响，水生生物为了应对紫外辐射会产生不同的适应性。以往研究认为浮游甲壳动物通过昼夜垂直迁移或积累抗紫外物质来适应水下紫外辐射，而抗紫外物质积累的适应机制多是从室内实验获得的，是否在野外存在尚不清楚。我们前期调查发现有抗紫外物质的浮游甲壳动物依然存在昼夜垂直迁移行为，因此，本研究假设在水下紫外辐射较强的湖泊中，浮游甲壳动物抗紫外物质的积累可能不足以抵御表层水下紫外辐射，而必须依赖昼夜垂直迁移适应水下紫外辐射。本项目选择云南高山湖泊作为研究地点，采用野外调查和模拟实验相结合的方法，在调查浮游甲壳动物昼夜垂直迁移规律的基础上，分析其与环境因子及抗紫外物质的关系，通过模拟实验分析紫外辐射对含有抗紫外物质的浮游甲壳动物的影响程度。本研究的目的是揭示浮游甲壳动物对紫外辐射的适应机制，结果有助于认识全球变化造成的紫外辐射增强对浮游甲壳动物的影响。

强紫外辐射会对水生生物产生不利的影响，水生生物为了应对紫外辐射会产生不同的适应性。以往研究认为浮游甲壳动物通过昼夜垂直迁移或积累抗紫外物质来适应水下紫外辐射，而抗紫外物质积累的适应机制多是从室内实验获得的，是否在野外存在尚不清楚。因此，本研究假设(1) 高山湖泊中浮游甲壳动物存在昼夜垂直迁移（DVM）行为与水中DOC和CDOM含量有关, 即含量高的湖泊浮游甲壳动物没有DVM行为，反之就有; (2) 在水下紫外辐射较强的高山湖泊，含有抗紫外物质的浮游甲壳动物不能完全适应表层水下紫外辐射，仍需要DVM行为来适应这种环境，浮游甲壳动物夜晚到表层是为了获取更多高质量的食物。本研究通过对云南高山湖泊水环境与浮游甲壳动物的调查分析，结果表明：（1）浮游甲壳动物DVM行为与DOC和CDOM含量有关。树线上湖泊DOC和CDOM含量显著低于树线下的，造成紫外衰减深度不同，树线上湖泊紫外辐射强度1%的深度为2-3 m，树线下仅为30-50 cm，因此树线上湖泊浮游甲壳动物存在DVM行为，而树线下湖泊无此行为。（2）在水下紫外辐射较强的湖泊，含有抗紫外物质的浮游甲壳动物仍需要DVM行为来适应这种环境。（3）黑海、圣母湖、木梆海哲水蚤体内所含的游离态虾青素、酯化态虾青素十月份均高于七月份。两个月份游离态虾青素、虾青素酯均为木梆海哲水蚤含量最高，黑海哲水蚤含量最低。黑海、圣母湖、木梆海哲水蚤体内虾青素均以虾青素酯为主，虾青素酯所占虾青素总量的比例均大于50%。（4）木梆海游离虾青素和虾青素酯的浓度以及游离虾青素的比率从无节幼体到成体阶段都有所增加。虾青素酯在各发育阶段均占主导地位。悬浮物中不饱和脂肪酸占总脂肪酸的比例不到1%，但占哲水蚤总脂肪酸的50%以上。总脂肪酸含量与总虾青素、游离虾青素和虾青素酯浓度呈正相关。通过本项目的研究，揭示了浮游甲壳动物对紫外辐射的适应机制，结果有助于认识全球变化造成的紫外辐射增强对浮游甲壳动物的影响。