Abstract: The outbreak of crown-of-thorns starfish (Acanthaster planci, CoTS) poses a significant threat to the health of coral reef ecosystems. Artificial removal is identified as one of the most practical and effective method for addressing local outbreaks of CoTS. The marine environmental impact of discarding captured CoTS inactivated and return to the sea is currently unknown. In this study, an in situ experiment was conducted to assess the ecological and environmental effects of boiling inactivation method of crown-of-thorns starfish. The treatment resulted in decomposition of CoTS tissues required 2 days for decomposition after boiled inactivation, with the decomposed bones taking on a granular form. On the 9 th day after returning the CoTS to the sea, 63.20% of carbon, 62.18% of nitrogen, and 44.17% of phosphorus were released into the water, resulting in an increase of (0.08 ± 0.06)mg·L-1 in carbon concentration, 0.08 ± 0.08 mg·L-1 in nitrogen concentration, and an decrease of 0.01 mg·L-1 in phosphorus concentration. In addition, the dominant bacteria on the surface of the inactivated CoTS mainly belong to the Proteobacteria, Cyanobacteria, Actinobacteria and Bacteroidetes. The dominant genera were Sphingomonas of Bacteroidetes, and Ruegeria, Pelomonas, Nautella and Tenacibaculum of Proteobacteria, which are associated with the decomposition of the CoTS. After boiling and inactivating, the CoTS remains decomposes quickly and can directly release nutrients. The small amount of inactivated CoTS does not have significant adverse effects on the environment, making it a relatively economical and eco-friendly way to deal with outbreaks of CoTS.

Key words: Crown-of-thorns starfish, Outbreak, Coral, Marine environment, Ecological effect