锌胁迫下两种鹿角珊瑚虫黄藻荧光值的变化

Heavy Metal Zinc Stress on the Photosynthesis of Zooxanthellae of Two Acropora Corals

以海南三亚鹿回头珊瑚礁区生长的花鹿角珊瑚（Acroporaflorida）和浪花鹿角珊瑚（Acroporacytherea）为研究对象，通过实验室模拟金属锌的胁迫环境，利用叶绿素荧光仪测试两种珊瑚虫黄藻在不同浓度硫酸锌胁迫下的叶绿素荧光参数。实验结果显示：（1）当珊瑚暴露在相对低浓度锌（105．6ug／L）条件下，枝条较细的浪花鹿角珊瑚的最大光化学产量（Fv／Fm）和最大电子传递速率（rETRmax）快速下降；较粗的花鹿角珊瑚前6天无明显反应，但到第8天时其几，砌和rETRmax亦开始显著下降；（2）当珊瑚暴露在相对高浓度锌（599．4ug／L）条件下时，两种鹿角珊瑚颜色均快速变浅，第2天即大面积露出白色骨骼，Fv／Fm下降到0-3以下，不再对光强产生响应，指示珊瑚已死亡。实验结果揭示了珊瑚虫黄藻光合作用对重金属胁迫的响应过程，表明锌污染对造礁珊瑚虫黄藻光合能力有严重的抑制作用，从而影响到珊瑚生长，高浓度的锌使虫黄藻光合作用快速衰减直至停止，导致珊瑚短时间内死亡。

Chlorophyll fluorescence parameters of zooxanthellae of coral Acorpora florida and A. cytherea growing at indoor tank environment were measured by using PAM fluorometry to investigate their response to heavy metal Zinc（Zn）stress. Both corals are branch species, but the branches ofA. cytherea are thinner than those of A. florida. In this experimental study, they were subjected to Zn concentration at levels of 105.6ug/L and 599.4ug/L, respectively, and the results show that： （1）When the two species of corals were exposed to relative lower Zn concentration （105.6ug/L） environment, the thin-branch coral A. cytherea quickly showed obviously stressed signals, with its Fv/Frn and rETRmax decreasing rapidly; while the similar rapid decline of the fuorescence parameters of the thick-branch coral A. florida started from the seventh day and they showed only slightly decline within the first 6 days. （2） When the two species of corals were exposed in higher level of Zn （599.4ug/L） environment, both corals discolored soon and most part of their surface showed white skeleton （bleached） in the second day. They no longer had any response to light, and their Fv/Fm dropped to below 0.3, which means corals were dead. This experiment study indicates that heavy metal Zinc pollution has obvious stress on the photosynthesis of coral symbiotic algae by lowering their efficiency of photosynthesis of PS II and even killing the corals.