Department of Ecology, Environment and Plant Sciences (DEEP), Stockholm University, 106 91, Stockholm, Sweden.
Institute of Oceanography (IO), Nha Trang, Vietnam.
Environ Sci Pollut Res Int. 2018 May;25(14):13360-13372. doi: 10.1007/s11356-016-8320-7. Epub 2017 Jan 22.
The combined effects of the herbicide glyphosate and elevated temperature were studied on the tropical staghorn coral Acropora formosa, in Nha Trang bay, Vietnam. The corals were collected from two different reefs, one close to a polluted fish farm and one in a marine-protected area (MPA). In the laboratory, branches of the corals were exposed to the herbicide glyphosate at ambient (28 °C) and at 3 °C elevated water temperatures (31 °C). Effects of herbicide and elevated temperature were studied on coral bleaching using photography and digital image analysis (new colorimetric method developed here based on grayscale), chlorophyll a analysis, and symbiotic dinoflagellate (Symbiodinium, referred to as zooxanthellae) counts. All corals from the MPA started to bleach in the laboratory before they were exposed to the treatments, indicating that they were very sensitive, as opposed to the corals collected from the more polluted site, which were more tolerant and showed no bleaching response to temperature increase or herbicide alone. However, the combined exposure to the stressors resulted in significant loss of color, proportional to loss in chlorophyll a and zooxanthellae. The difference in sensitivity of the corals collected from the polluted site versus the MPA site could be explained by different symbiont types: the resilient type C3u and the stress-sensitive types C21 and C23, respectively. The additive effect of elevated temperatures and herbicides adds further weight to the notion that the bleaching of coral reefs is accelerated in the presence of multiple stressors. These results suggest that the corals in Nha Trang bay have adapted to the ongoing pollution to become more tolerant to anthropogenic stressors, and that multiple stressors hamper this resilience. The loss of color and decrease of chlorophyll a suggest that bleaching is related to concentration of chloro-pigments. The colorimetric method could be further fine-tuned and used as a precise, non-intrusive tool for monitoring coral bleaching in situ.
研究了除草剂草甘膦和升高温度对越南芽庄湾热带鹿角珊瑚（Acropora formosa）的综合影响。这些珊瑚是从两个不同的珊瑚礁中收集的，一个靠近受污染的鱼场，一个在海洋保护区（MPA）内。在实验室中，将珊瑚的分枝暴露于环境（28°C）和升高 3°C 的水温（31°C）下的除草剂草甘膦中。使用摄影和数字图像分析（这里开发的基于灰度的新比色法）、叶绿素 a 分析和共生虫黄藻（Symbiodinium，称为共生藻）计数来研究除草剂和升高温度对珊瑚白化的影响。所有来自 MPA 的珊瑚在暴露于处理之前在实验室中开始白化，这表明它们非常敏感，而与从污染程度较高的地点收集的珊瑚相反，这些珊瑚更具耐受性，并且对温度升高或单独使用除草剂没有白化反应。然而，联合暴露于这些胁迫因子会导致颜色显著丧失，与叶绿素 a 和共生藻的丧失成正比。从污染地点和 MPA 地点收集的珊瑚对这些胁迫因子的敏感性差异可以用不同的共生体类型来解释：有弹性的 C3u 型和应激敏感的 C21 和 C23 型。升高温度和除草剂的累加效应进一步证明了在存在多种胁迫因子的情况下，珊瑚白化会加速。这些结果表明，芽庄湾的珊瑚已经适应了持续的污染，对人为胁迫因子更具耐受性，而多种胁迫因子则阻碍了这种恢复力。颜色的丧失和叶绿素 a 的减少表明白化与氯色素的浓度有关。比色法可以进一步进行微调，并用作原位监测珊瑚白化的精确、非侵入性工具。
