College of Environmental and Resource Sciences, Shanxi University, Taiyuan, 030006, PR China; Shaanxi Key Laboratory of Land Consolidation, Xi'an, 710064, PR China; Shanxi Sino-Environmental Hongda Monitoring Technology Co. Ltd., Taiyuan, 030032, PR China.
College of Environmental and Resource Sciences, Shanxi University, Taiyuan, 030006, PR China.
Ecotoxicol Environ Saf. 2020 Apr 15;193:110359. doi: 10.1016/j.ecoenv.2020.110359. Epub 2020 Feb 22.
Earthworms as ecosystem engineers partially improve soil properties by egesting casts. Our previous study confirmed that soil pollution affects the physico-chemical properties of earthworm casts. It is still unclear whether the biological properties (e.g. cellulase, urease, and acid and alkaline phosphatase activities, as well as microbial biomass carbon) of casts are affected by foreign substances in soil. The present study aimed to investigate the effect of phenanthrene (PHE) on the biological characteristics of earthworm (Eisenia fetida) casts. Furthermore, correlations between cast properties and the digestive and antioxidant systems were explored by the determination of digestive enzyme (urease, protease, acid and alkaline phosphatase) activities, antioxidant indexes [superoxide dismutase (SOD), catalase (CAT), and peroxidase (POD)], as well as malondialdehyde (MDA) content. Exposure at a range of PHE doses (0, 2, 5, 10, and 20 mg kg) for 15 d resulted in the following observations: (1) Compared with urease, as well as acid and alkaline phosphatase activities, cellulase activities in both soil and casts were sensitive to PHE, and could potentially act as biomarkers to provide early-warning signals for soil pollution. (2) Microbial biomass carbon in casts was modified, but with no clear pattern. (3) Cellulase and POD activities, as well as MDA content in earthworms, increased with elevated exposure to PHE in soil. Protease, SOD, and CAT activities exhibited a biphasic dose response to PHE, while acid and alkaline phosphatase activities were inhibited under treatment conditions. (4) Correlation analysis suggested that microbial biomass carbon in casts significantly and positively correlated with cellulase and acid phosphatase activities of earthworms, but negatively correlated with protease activities. A significant but weak negative correlation between alkaline phosphatase activities in casts and POD activities was also observed. Based on these results, we concluded that PHE content in soil modified some biological properties of casts, by partially affecting the earthworm's digestive and antioxidant systems. This study advances our knowledge of earthworm ecology in polluted soil by providing a better understanding of their ecological functions.
蚯蚓作为生态系统工程师，通过排泄蚓粪部分改善土壤性质。我们之前的研究证实，土壤污染会影响蚯蚓粪的理化性质。但目前尚不清楚土壤中的外来物质是否会影响蚓粪的生物特性（如纤维素酶、脲酶、酸性和碱性磷酸酶活性以及微生物生物量碳）。本研究旨在研究菲（PHE）对蚯蚓（Eisenia fetida）粪生物特性的影响。此外，通过测定消化酶（脲酶、蛋白酶、酸性和碱性磷酸酶）活性、抗氧化指标[超氧化物歧化酶（SOD）、过氧化氢酶（CAT）和过氧化物酶（POD）]以及丙二醛（MDA）含量，探讨了粪特性与消化和抗氧化系统之间的相关性。在 15 天的时间里，蚯蚓暴露在一系列 PHE 剂量（0、2、5、10 和 20mg/kg）下，结果如下：（1）与脲酶以及酸性和碱性磷酸酶活性相比，土壤和粪中的纤维素酶活性对 PHE 更为敏感，可能作为生物标志物，为土壤污染提供预警信号。（2）粪中的微生物生物量碳发生了变化，但没有明显的规律。（3）土壤中 PHE 浓度升高，蚯蚓的纤维素酶和 POD 活性以及 MDA 含量增加。蛋白酶、SOD 和 CAT 活性对 PHE 表现出双相剂量反应，而酸性和碱性磷酸酶活性在处理条件下受到抑制。（4）相关分析表明，粪中的微生物生物量碳与蚯蚓的纤维素酶和酸性磷酸酶活性呈显著正相关，但与蛋白酶活性呈负相关。还观察到粪中碱性磷酸酶活性与 POD 活性之间存在显著但较弱的负相关。基于这些结果，我们得出结论，土壤中 PHE 含量通过部分影响蚯蚓的消化和抗氧化系统，改变了一些粪的生物特性。本研究通过更好地了解蚯蚓在污染土壤中的生态功能，为蚯蚓生态学在污染土壤中的研究提供了新的认识。
