Jeong Ha Kim1, Kwon Mo Yang1, Seokwoo Hong1, Junsu Kim1, Daniela Macias1,1Dong Mun Choi1,2
1Department of Biological Sciences, Sungkyunkwan University, Suwon, Republic of Korea, 2Marine Bio-Resources Research Unit, Korea Institute of Ocean Science and Technology, Busan, Republic of Korea
Correspondence: Jeong Ha Kim, jhkbio@skku.edu
Deforestation has been a major concern in the Korean coastal ecosystems, and Mesocentrotus nudus, the dominant sea urchin species, was regarded as a major cause, appearing >8 inds/m2 in barren sites. This study was started with testing the various feeding habits of M. nudus, followed by field manipulative experiments to examine i) the possibility of seaweed bed recovery by controlling urchin density, ii) the speed of recovery and deforestation in a bi-directional test, iii) the threshold density of sea urchins, and iv) the functional recovery of restored forest. M. nudus’ most preferred food choice was Undaria pinnatifida among the six common seaweed species tested, but the choice switched to Grateloupia elliptica depending on their past feeding history. Barren rocks recovered to the level of existing natural forests within 1.5 years by controlling urchin density only, and the effect of further exclusion of other herbivores was not significant in quantitative perspectives. On the other way of phase shift, deforestation took 1.0 year when existing forests were exposed to the urchin density of barren state. The threshold density of M. nudus between the two phases was 2.5 inds/m2 in this study for the case of mostly annual seaweeds with a high seasonality. Regarding the functional recovery measured by trophic structure and food web stability, it took 2 years to reach the nearby natural forest level with the first year of restoration not an intermediate stage toward the completion, but a transient over-shooting state. Conclusive notes and discussion are addressed in the presentation.