1:45 PM - 3:15 PM
[O11-P94] Competition for survival between soft corals and hard corals observed on Kikai Island
Keywords:soft coral, hard coral
(Introduction)
Corals are broadly classified into hard corals and soft corals, which compete with each other for space. This study aimed to investigate whether soft corals only use overgrowth as a method of attack and which type of coral tends to dominate in such competition. Previous research has shown that soft corals can gain an advantage through allelopathy in spatial competition.
(Methods)
In August and September 2024, surveys were conducted at two sites on Kikai Island, Kagoshima Prefecture. The line intercept transect method was used to observe a 25-meter section of the reef and assess substrate composition. Points where hard and soft corals were in direct contact and competing were identified, and the species involved, outcomes, and methods of dominance were recorded. Soft corals observed included Sarcophyton (commonly known as leather coral) and Sinularia species.
(Results)
The substrate survey showed hard corals made up 30% and soft corals 15%, indicating hard corals were more abundant. In competitive interactions, Favia corals (hamasango) won all 7 observed matches against soft corals. However, Sarcophyton soft corals were stronger than many hard corals, excluding Favia.
(Discussion)
With 7 wins for hard corals and 6 for soft corals, hard corals showed a slight competitive advantage. Favia was particularly strong, but due to its large size and proximity to the sea surface, it is more prone to bleaching from rising temperatures. Although Favia grows slowly, its sturdy structure may contribute to its competitive success. Sarcophyton was considered to be stronger than other hard corals. Soft corals, with their flexible and expansive bodies, are likely to rely on overgrowth as a primary attack strategy. Given their resistance to bleaching, soft corals may become more dominant as ocean temperatures continue to rise.
Corals are broadly classified into hard corals and soft corals, which compete with each other for space. This study aimed to investigate whether soft corals only use overgrowth as a method of attack and which type of coral tends to dominate in such competition. Previous research has shown that soft corals can gain an advantage through allelopathy in spatial competition.
(Methods)
In August and September 2024, surveys were conducted at two sites on Kikai Island, Kagoshima Prefecture. The line intercept transect method was used to observe a 25-meter section of the reef and assess substrate composition. Points where hard and soft corals were in direct contact and competing were identified, and the species involved, outcomes, and methods of dominance were recorded. Soft corals observed included Sarcophyton (commonly known as leather coral) and Sinularia species.
(Results)
The substrate survey showed hard corals made up 30% and soft corals 15%, indicating hard corals were more abundant. In competitive interactions, Favia corals (hamasango) won all 7 observed matches against soft corals. However, Sarcophyton soft corals were stronger than many hard corals, excluding Favia.
(Discussion)
With 7 wins for hard corals and 6 for soft corals, hard corals showed a slight competitive advantage. Favia was particularly strong, but due to its large size and proximity to the sea surface, it is more prone to bleaching from rising temperatures. Although Favia grows slowly, its sturdy structure may contribute to its competitive success. Sarcophyton was considered to be stronger than other hard corals. Soft corals, with their flexible and expansive bodies, are likely to rely on overgrowth as a primary attack strategy. Given their resistance to bleaching, soft corals may become more dominant as ocean temperatures continue to rise.