Biomass reduction of Salvinia molesta exposed to copper sulfate pentahydrate (CuSO4.5H2O)

Copper in the aquatic ecosystem may remain adsorbed or be incorporated into the biomass and undergo biomagnification causing unwanted effects to aquatic macrophyte communities. This study evaluated the biomass reduction of Salvinia molesta (Mitchell) exposed to copper sulphate pentahydrate (CuSO4.5H2O) under laboratory conditions. Approximately 20.5 g of fresh mass (FM) of S. molesta (0.74 g dry matter, DM) were placed in glass tanks with different concentrations (n = 3) of CuSO4.5H2O as follows: 0.0; 2.0; 4.0; 6.0; and 8.0 mg L-1 for 28 days. The dry mass was determined after each seven-day interval over 28 days and submitted to repeated ANOVA measures, followed by a Tukey test (P<0,05). The results show that macrophyte increased until the seventh day of exposure in all treatments. After this period, the biomass of S. molesta decreased; but there was no significant difference between treatments with copper, except for the 8.0 mg L-1 treatment. The copper treatments decreased the S. molesta biomass an average of 43.2% (0.50 g DM) after 28 days. At the end of the experiment, copper absorption in the treatments with 6.0 and 8.0 mg L-1 was on average 77.9% higher than in the treatments with 2 and 4 mg L-1. The treatments with 6.0 and 8.0 mg L-1 reached their maximum bioaccumulation capacity after 14 days. The results show that contamination of the aquatic environment at concentrations above 2 mg L-1 Cu2+ can reduce the S. molesta biomass by approximately 43%.

水生生态系统中的铜可吸附于环境介质中，或被生物组分富集并发生生物放大作用，对水生大型植物群落造成不良影响。本研究于实验室条件下，评估了暴露于五水硫酸铜（CuSO4·5H2O）中的巨槐叶萍（Salvinia molesta (Mitchell)）的生物量变化情况。实验选取约20.5 g鲜重（Fresh Mass, FM）的巨槐叶萍（对应干物质0.74 g，Dry Matter, DM），置于装有不同浓度五水硫酸铜（每组重复数n=3）的玻璃水族箱中，铜浓度设置为0.0、2.0、4.0、6.0及8.0 mg·L⁻¹，暴露时长为28天。每7天为一个测定周期，于28天内依次测定其干重，并采用重复测量方差分析（repeated ANOVA measures）辅以Tukey检验进行统计学分析（显著性阈值P<0.05）。结果显示，所有处理组的植物生物量均在暴露第7天时达到峰值；此后巨槐叶萍生物量出现下降，但除8.0 mg·L⁻¹处理组外，其余铜浓度处理组间无显著统计学差异。实验至28天时，各铜处理组的巨槐叶萍生物量平均降低了43.2%（对应干物质0.50 g）。实验结束时，6.0和8.0 mg·L⁻¹处理组的铜吸收量较2.0与4.0 mg·L⁻¹处理组平均高出77.9%。6.0和8.0 mg·L⁻¹处理组在暴露14天后即达到最大生物富集能力。本研究结果表明，当水生环境中Cu²+浓度高于2 mg·L⁻¹时，可使巨槐叶萍生物量降低约43%。