Department of Zoology and Environmental Management, University of Kelaniya, Kelaniya 11600, Sri Lanka.
Department of Zoology and Environmental Management, University of Kelaniya, Kelaniya 11600, Sri Lanka.
Ecotoxicol Environ Saf. 2021 Mar 15;211:111891. doi: 10.1016/j.ecoenv.2021.111891. Epub 2021 Jan 25.
Tropical freshwater ecosystems are increasingly influenced by chemical stressors including heavy metals posing threats to biodiversity. Adequate ecotoxicity data are not available for native tropical freshwater species for deriving water quality guidelines and for conducting ecological risk assessments. Objectives of this study were (i) to generate freshwater ecotoxicity data for cadmium (Cd) and copper (Cu) for tropical temperature exposures using standard laboratory bioassays with selected freshwater species and (ii) to derive ecotoxicity thresholds (protection concentrations, PC) for tropical freshwater life based on 'tropical temperature-specific exposure' ecotoxicity data. Estimated final chronic toxicity values of the six species tested in the study indicate that the most sensitive species was the crustacean, Moina macrocopa for both metals while the algae Chlorella vulgaris and the plant Lemna perpusilla showed highest tolerance to Cd and Cu respectively. Tropical temperature-specific exposure (25-30 °C) was used as the decision criterion for deriving ecotoxicity thresholds of Cd and Cu for protection of tropical freshwater life based on species sensitivity distribution analysis of the final chronic toxicity data sets which included published toxicity data of selected species in addition to the six species tested in this study. The derived PC99, PC95, PC90 and PC80 values for protection of tropical freshwater life under chronic exposure are 0.5, 1.2, 1.9 and 3.5 μg/L for Cd and 0.34, 0.84, 1.4 and 2.6 μg/L for Cu respectively. These derived threshold chronic values (PC99 and PC95) indicate that the established freshwater quality guidelines based on temperate species for Cu may not provide sufficient protection of the freshwater species in the tropics while the available freshwater guidelines for Cd would provide adequate protection for the tropical freshwater species. The tropical freshwater ecotoxicity thresholds derived in this study may be used with some caution as reference points for site specific ecological risk assessments in the tropics.
热带淡水生态系统越来越受到包括重金属在内的化学胁迫因子的影响，这些胁迫因子对生物多样性构成了威胁。对于本土热带淡水物种，没有足够的生态毒理学数据来制定水质准则和进行生态风险评估。本研究的目的是：(i)使用选定的热带淡水物种的标准实验室生物测定法，生成关于热带温度暴露下镉(Cd)和铜(Cu)的淡水生态毒理学数据；(ii)根据“热带温度特定暴露”的生态毒理学数据，为热带淡水生物确定生态毒性阈值(保护浓度，PC)。在本研究中测试的 6 种物种的最终慢性毒性值表明，甲壳类动物 Moina macrocopa 对这两种金属最敏感，而藻类 Chlorella vulgaris 和植物 Lemna perpusilla 对 Cd 和 Cu 的耐受性最高。基于物种敏感性分布分析，使用热带温度特定暴露（25-30°C）作为决策标准，从最终慢性毒性数据集推导 Cd 和 Cu 的生态毒性阈值，该数据集除了本研究中测试的 6 种物种外，还包括选定物种的已发表毒性数据。在慢性暴露下，为保护热带淡水生物而推导的 PC99、PC95、PC90 和 PC80 值分别为 0.5、1.2、1.9 和 3.5μg/L 用于 Cd，0.34、0.84、1.4 和 2.6μg/L 用于 Cu。这些推导的阈值慢性值（PC99 和 PC95）表明，基于温带物种制定的铜的淡水水质准则可能无法为热带淡水物种提供充分的保护，而现有的镉淡水准则将为热带淡水物种提供足够的保护。本研究中推导的热带淡水生态毒性阈值可以谨慎用作热带特定地点生态风险评估的参考点。
