Bleaching of Symbiotic Algae (Zooxanthellae) and their Invertebrate Hosts: Causes and Mechanisms

珊瑚礁和其他无脊椎动物的色素、珊瑚和其他无脊椎动物的色素的漂白，即共生甲藻的丧失，已经成为热带海洋生态系统中的一个世界性问题，一些研究人员将其与全球变暖联系在一起。漂白的结果在加勒比海、印度-太平洋和其他热带海洋地区具有潜在的破坏性环境、生态和经济影响。尽管有一些实验工作表明，漂白涉及高于平均温度和光照的因素，但涉及漂白的机制尚不清楚。这个项目将检验三个假设。1.自然界中的漂白是由高温胁迫和高能蓝光(可能是380-400 nm之间的UV-A)共同作用引起的。初步证据表明，虽然高温单独会导致漂白，但高温处理期间的自然光暴露会通过降低温度阈值和在给定温度下漂白的时间来加剧这种影响。这项研究将确定光的哪种成分对这种影响负责，并确定其作用机制。早期关于漂白的理论认为光起了主要作用，但实验证据尚未支持这一论点。与高能量波长的蓝光(可能还有一些近蓝色波长的UV-A，它们不被珊瑚中发现的紫外线保护色素吸收)有关的潜在有害化学变化不仅与漂白的现场观察一致，而且得到了实验室和野外初步实验的支持。2.温光诱导漂白的机理涉及叶绿体中叶绿素-蛋白质缔合的不可逆解离。高温和光照对藻类的有害影响包括与叶绿体中的反应中心相关的叶绿素-蛋白质复合体不可逆转地分离或失活。电子传递活性和最终的碳固定活性显著降低。3.高光和高温会导致吸收紫外线的“保护性”色素减少。不同波长的光和高温在确定紫外线屏蔽颜料浓度方面的作用以及它们与光合作用速率的关系将被确定。这些假设将在实验室和野外实验中使用培养的和新分离的虫黄藻和完整的宿主进行验证。

Bleaching, the loss of symbiotic dinoflagellates)="zooxanthellae" hereafter) of their pigments, of reef corals and other invertebrates has become a world-wide problem in tropical marine ecosystem, linked by some researchers to global warming. The results of bleaching have potentially devastating environmental, ecological and economic effects in the Caribbean, IndoPacific, an other tropical marine areas. Though there is some experimental work showing involvement of both higher than average temperature and light, the mechanisms involved in bleaching are not well understood this project will test three hypotheses. 1. Bleaching in nature is caused by high temperature stress coupled with high energy blue light (and possibly UV-A between 380-400nm). Preliminary evidence shows that while high temperature alone will induce bleaching, natural light exposure during high temperature treatment exacerbates the effect by lowering the temperature threshold and time to bleaching at a given temperature. this study will determine which component of light is responsible for this effect and the mechanisms of action. Early theories on bleaching had light playing a major role, but experimental evidence has not yet supported this contention. Potentially harmful chemical alterations associated with high energy wavelengths of blue light (and possibly some near-blue wavelengths of UV-A, that are not adsorbed by UV-protecting pigments found in corals) are not only consistent with field observations of bleaching, but are also supported by both laboratory and field-based preliminary experiments. 2. The mechanisms of temperature-light induced bleaching involves the irreversible dissociation of the chlorophyll-protein associations in the chloroplast. The harmful effects of high temperatures and light on algae include the irreversible separation or inactivation of the chlorophyll-protein complexes associated with reaction centers in the chloroplast. Electron transport activity and eventually carbon fixation decrease markedly. 3. High light and temperatures cause decreases in "protective" pigments which absorb ultraviolet light. The role of different wavelengths of light in conjunction with high temperature in determining concentrations of UV-screening pigments will be determined as well as their relationship with photosynthetic rates. These hypotheses will be tested using cultured and freshly isolated zooxanthellae, and intact hosts both in the laboratory and in field-based experiments.