防晒霜的使用日益广泛，其中添加了纳米氧化锌（nZnO）、纳米二氧化钛（nTiO2）等纳米材料作为防晒剂的物理防晒霜以较高的安全性及较小的皮肤渗透性受到人们的青睐，其产量和使用量逐渐占据市场主导地位。但物理防晒霜会随着沿海娱乐活动释放到海洋环境中，而其对近岸海域重要生态系统的影响尚不清楚，目前已引起广泛的关注。本论文以近海珊瑚礁生态系统中的常见种纽扣珊瑚（Zoanthus.sp）作为受试生物，研究物理防晒霜进入海洋环境后，在环境浓度下对纽扣珊瑚的毒性效应及其潜在机理。 试验结果表明，物理防晒霜对纽扣珊瑚的展开行为抑制效应与暴露浓度和暴露时间相关，当暴露浓度为10 mg/L时，24 h抑制率可达96.7%。当进一步探究物理防晒霜对纽扣珊瑚各生理指标的影响时发现：10 mg/L物理防晒霜能显著降低纽扣珊瑚的含水率；受胁迫的纽扣珊瑚与虫黄藻（Zooxanthella）的共生关系遭到破坏，大量共生虫黄藻脱离寄主呈游离状，且10 mg/L物理防晒霜胁迫下虫黄藻的光系统Ⅱ最大光化学量子产量（Fv/Fm）下降；高浓度物理防晒霜使珊瑚兴奋性神经递质谷氨酸（Glu）的清除受阻，指示原始的网状神经系统功能受到影响；当暴露于中（2.5 mg/L）、高（10 mg/L）浓度时，1 d内即可刺激珊瑚产生大量黏液。通过对纽扣珊瑚受胁迫后的恢复功能进行探索发现，纽扣珊瑚长期处于高浓度胁迫下恢复功能会受损，生存环境的改善也难以使其完全修复。 进一步探索物理防晒霜造成上述毒性效应的潜在机理。初步认为，在本论文添加浓度范围内水体浑浊度的变化不是纽扣珊瑚触手展开受抑制的主要原因。从致毒因子的角度分析，物理防晒霜中的两种主要无机防晒剂nZnO、nTiO2对珊瑚的毒性差异明显。nZnO的毒性显著大于nTiO2，nTiO2在环境浓度范围内（小于400 μg/L）对纽扣珊瑚的影响有限，而nZnO防晒剂在水中溶解产生的Zn2+易被富集在纽扣珊瑚体内进而产生一系列毒性反应，是物理防晒霜对纽扣珊瑚产生毒性的主要因子，值得引起重视。 本文较为全面地剖析物理防晒霜胁迫对纽扣珊瑚的毒性，分析了物理防晒霜使用量的激增对近岸海洋重要生态系统可能带来的影响及其作用机制，为防晒霜这一新型污染物的生态毒理研究和环境治理提供参考。
As sunscreens become increasingly widely used, physical sunscreens in which nano materials such as nano-zinc oxide (nZnO) and nano-titanium dioxide (nTiO2) are added as inorganic UV-filters are favored by people for their higher safety and smaller skin penetration than chemical sunscreens. The production and use of physical sunscreens gradually occupy the dominant position in the market. However, physical sunscreens will be released into the marine environment with coastal recreational activities. Their impact on important ecosystems in coastal waters is unclear, and has attracted widespread attention. In this paper, the common button coral Zoanthus sp. in the offshore coral reef ecosystem was used as the test organism to study the toxic effects and potential underlying mechanisms of the physical sunscreen at the environmental concentration after entering the marine environment. The results showed that the behavioral inhibition effect of physical sunscreen on the Zoanthus sp. was concentration- and time-dependent. When the exposure concentration was 10 mg/L, the 24-h inhibition rate can reach 96.7%. When further investigating the effect of physical sunscreen on the various physiological parameters of Zoanthus sp., it was found that: the moisture content of the Zoanthus sp. was significantly reduced after exposing to 10 mg/L physical sunscreen; the symbiotic relationship between the Zoanthus sp. and Zooxanthella was destroyed, and a large number of symbiotic zooxanthellae were released from the host, moreover, the Fv/Fm of zooxanthellae was reduced after 10 mg/L physical sunscreen exposure; high concentration (10 mg/L) of physical sunscreen hindered the removal of coral excitatory neurotransmitter glutamate (Glu), indicating that the function of the original reticular nervous system was affected; When exposed to medium (2.5 mg/L) and high (10 mg/L) concentrations, corals can be stimulated to produce large amounts of mucus within 1 d of exposure. By exploring the recovery function of Zoanthus sp. under stress, it was found that the recovery function of Zoanthus sp. under high concentration stress for a long time will be damaged, and the improvement of the living environment cannot make it completely repaired. Then, we further investigated the underlying mechanism of the above toxic effects of physical sunscreens. Primarily, the change of turbidity in the concentration range was not considered as the main reason for inhibiting the tentacle expansion of Zoanthus sp.. But our results demonstrated that the two main inorganic UV-filters (nZnO and nTiO2) in physical sunscreens had significant differences in toxicity to corals. The toxicity of nZnO was significantly greater than that of nTiO2. nTiO2 had a limited effect on Zoanthus sp. within the environmental concentration range (less than 400 μg/L). While Zn2+ produced during the dissolution of nZnO UV-filter in water was easily enriched in Zoanthus sp. and then produced a series of toxic reactions. It was the main factor of physical sunscreen's toxicity to Zoanthus sp., which deserves attention. This paper analyzed the toxicity of physical sunscreen on Zoanthus sp. in a relative comprehensive manner, and analyzed the possible impact of the surge in the use of physical sunscreen on important coastal marine ecosystems and its mechanism, which provided a reference for the ecotoxicological research and environmental treatment of sunscreen.
