Effects of lowered seawater pH on the early life history of Crown-of-Thorns starfish

Crown-of-Thorns starfish (COTs), Acanthaster planci is known as one of the most significance threats in coral reef ecosystem. During the COTs outbreak it caused extensive coral mortality and consequently lead to habitat loss... [ view full abstract ]

Crown-of-Thorns starfish (COTs), Acanthaster planci is known as one of the most significance threats in coral reef ecosystem. During the COTs outbreak it caused extensive coral mortality and consequently lead to habitat loss of other reef-associated organisms. It is important to investigate the environmental tipping point on COTs early life history stages to understand the limits for normal development of this starfish. In this study, the effects of projected ocean acidification conditions (pH: 7.4 & 7.8) were tested on fertilization success and larvae development rate of the COTs. The larvae development rate was investigated by measured the length and width of the larvae on 4^th and 14^th day of the experiment. The results showed that lowered seawater pH has no significance impact on the fertilization success rate. However, larvae size in the lowered pH treatments were significantly smaller than the control treatment (pH: 8.1). Length and width of COTs in lowered pH 7.8 and 7.4 treatments were 40%-46% and 28%-47% smaller than the samples in control treatment, respectively. These findings indicated that COTs larvae may survived ocean acidification conditions. But, larvae growth rate may delayed and their size reduced in the lowered pH seawater conditions.