Ultraviolet Light and Temperature Effects on Reef-Building Corals

最近对1987年加勒比地区大规模珊瑚白化事件的解释表明，海面温度升高和紫外线穿透增强是主要因素。该项目将通过进行一系列实验来调查这一假设，这些实验旨在划分紫外线和温度对珊瑚生长和存活的相对影响。适当的紫外线照射实验水平将基于下列数据：1)1989年记录的长期紫外线通量测量；2)评估增强紫外线照射影响的初步实地实验；3)将在热带清澈海水中进行的紫外线测量。实验珊瑚（环纹蒙氏珊瑚和拉玛基珊瑚）将在户外的紫外线透明丙烯酸水族箱中接受两种紫外线照射：1)环境紫外线通量，基于先前长期监测（对照）获得的值，以及2)最大紫外线通量，模拟1987年白化事件期间发生的情况(基于确定导致珊瑚应激的紫外线水平的初步实地实验结果，或在处理方面，珊瑚将受到三种受控温度制度：28摄氏度（对照）、30摄氏度和31摄氏度（1987年加勒比海珊瑚礁记录的最高或接近最高温度），持续时间长达两个月。将通过量化菌落颜色、叶绿素浓度、虫黄藻密度、有丝分裂指数和珊瑚组织中紫外线阻挡色素浓度的变化来评估处理效果（使用HPLC）。第二个实验将分离UV-A和uv -B的不同和综合效应。除了这些实验外，我们还将在开曼群岛的大开曼岛（美国国家海洋和大气管理局水瓶座栖息地项目所在地）建立一个长期的紫外线监测项目，并将这些发现与观察到的沿深度梯度的珊瑚礁珊瑚中紫外线色素浓度的种内和种间差异联系起来。这些数据将构成一个重要的基线，可用于记录由于平流层臭氧持续消失而造成的紫外线水平的年和年变化。

Recent explanations for the 1987 Caribbean-wide, mass coral bleaching event suggest that increased sea surface temperatures and enhanced ultraviolet light penetration were major contributing factors. This project will investigate this hypothesis by conducting a series of experiments designed to partition the relative effects that UV light and temperature have on coral growth and survivorship. Appropriate experimental levels for UV irradiation will be based on data derived from: i) long-term UV flux measurements recorded in 1989, ii) preliminary field experiments assessing effects of enhanced UV exposures, and iii) UV measurements to be taken in clear tropical oceanic waters. Experimental corals (Montastrea annularis and Agaricia lamarcki) held outdoors in UV-transparent acrylic aquaria will be subject to two UV light regimes: 1) ambient UV flux, based on values obtained form prior long-term monitoring (controls), and 2) maximum UV flux simulating the conditions that occurred during the 1987 bleaching event (based on results from preliminary field experiments identifying UV levels leading to coral stress, or on treatment, corals will be subjected to three controlled temperature regimes: 28oC (control), 30oC and 31oC (peak or near- peak temperatures recorded on reefs in the Caribbean during 1987) for up to two months. Treatment effects will be assessed by quantifying changes in colony color, chlorophyll concentration, zooxanthellae densities, mitotic indices and the concentrations of UV blocking pigments form coral tissues (using HPLC). A second experiment will separate the differential, and combined, effects of UV-A and -B. In addition to these experiments, we will establish a long- term UV monitoring program on Grand Cayman Island, Cayman Island (site of the NOAA Aquarius habitat program) and will relate these findings to observed intra- and interspecific differences in concentrations of UV pigments in reef corals along a depth gradient. These data will constitute an important baseline that can be used to document yearly and decadal changes in UV light levels resulting from continued deletion of stratospheric ozone.