Ecological safety assessment of an allelopathic algaecide against Alexandrium catenella

The blooms of Alexandrium catenella are a long-outstanding issue in the world, causing severe impacts on the local marine environment and the aquaculture industry. Our previous studies have also shown that mango peel extracts (MPE) could effectively inhibit the growth of A. catenella under controlled laboratory conditions. However, it remains unknown whether using MPE to control A. catenella-induced harmful algal blooms (HABs) in aquaculture environments will cause the release of intracellular phycotoxins into the surrounding environment, potentially affecting aquatic organisms. Additionally, the potential impact of MPE itself on aquatic life is another concern. The objective of this study was to clarify these issues primarily by assessing the ecological safety of MPE. The intracellular and extracellular paralytic shellfish toxins (PSTs) contents of A. catenella was measured throughout the experimental period using liquid chromatography tandem time-of-flight mass spectrometry (LC-TOFMS). The results showed that MPE reduced the PSTs contents in A. catenella, while no significant fluctuation was observed in the extracellular PSTs contents. Meanwhile, MPE exhibited varying degrees of inhibitory effects on the four HABs species selected in this study but promoted the growth of three of the four bait algae. The recorded results regarding the survival rate, water clearance rate, and growth rate of aquatic organism exposed to MPE showed no significant different between the control group and the experimental group. This study clarified that using MPE to govern HABs in aquaculture environments would not affect the growth of cultured organisms and demonstrated that MPE has species-specific antialgal properties. These findings contribute to a better understanding of the potential of MPE as an algaecide.