Effects of algal bloom growth and decay on the copper complexing capacity of seawater
The release of copper-complexing ligands during algae growth and decay was studied by anodic stripping voltammetry and molecular spectroscopy techniques through simulation experiments and field investigations.The algae included Skeletonema costatum,Prorocentrum donghaiense,and Ulva prolifera,which are the common predominant species of algal blooms in the coastal areas of China.The simulation experiments results showed significant release of organic ligands during the initial and decay periods of Skeletonema costatum and Prorocentrum donghaiense,while in the exponential growth stage the release seemed relatively weak.During Ulva prolifera blooms,the released organic ligands increased the copper complexing capacity(CuCC)of the seawater in the enclosed seawater up to 2.82 times that of the external area.In addition,the field data indicated that the accumulation and degradation of Ulva prolifera increased CuCC by 37.81%in the green tide area.The increase in CuCC during algae bloom was attributed to the labile dissolved organic matter,such as protein-like substances directly secreted by algae,while at the end of the growth,it was attributed to the relatively inert byproducts such as humic substances.sublethal copper stress accelerated the U.prolifera degradation as well as the release of organic ligands,resulting in the CuCC 2.78 times higher than the control group.Meanwhile,the free Cu2+in the system were effectively complexed,reducing to 6.27%of the initial level at the end of the cultivation,which significantly reduced the biological toxicity of Cu2+.
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