Abstract:
Populations of the subtropical coral Alveopora japonica Eguchi,
1965 are expanding, likely in response to changes in coastal
water conditions caused by human activities and climatic factors. To uncover the causes of population increase, we propose the
establishment of a long-term monitoring station to
comprehensively assess the drivers of population dynamics.
Therefore, the aim of this study was to obtain baseline
information on A. japonica in Oedo at Jeju Island (Korea) by
documenting benthic composition and characteristics of A.
japonica populations at different depths. In Oedo, the distribution
of A. japonica is mainly restricted to 15-m depth where a high
density of colonies was observed (410 ± 123 colonies m −2 ). These
colonies consist predominantly of small colonies with individual
or few polyps and are associated with a vertical shift in benthic
composition and interactions. Indeed, comparing results with
shallower waters where A. japonica is absent and geniculate
coralline algae dominate (66.5 ± 2.2% at 5-m and 60.5 ± 2.7% at
10-m depth), a contrasting pattern emerges at 15-m depth. Here,
crustose coralline algae make up the majority of the substrate at
56.1 ± 3.4%. These possible biotic drivers are discussed in
conjunction with other abiotic factors such as temperature to
explain the benthic community composition in Oedo. Given the
current benthic structure and accessibility of the study area, Oedo
proves to be an ideal sentinel site for monitoring the effects of
anthropogenic disturbances, especially global warming, on
temperate marine ecosystems.
