Recovery Pattern and Seasonal Dynamics of Kelp Species, Ecklonia cava Population Formed Following the Large-scale Disturbance

Abstract

Seasonal dynamics of kelp forest-forming algae, Ecklonia cava population formed following the large-scale disturbance by Typhoon 'Bolaven' in August 2012 were investigated in Jeju Island, Korea. Morphological characteristics, recruits density, mortality rate, total density and biomass were monitored bimonthly from June 2013 to June 2015. Total and longest blade lengths, and individual weight of E. cava showed distinct seasonal trends. Stipe length increased from winter to spring, but did not show increase or reduced from summer to autumn. This indicates that morphological characteristics of E. cava are mainly affected by the change of blades. The optimal temperature for E. cava growth was about 15-18°C during winter to spring while the growths were inhibited at the water temperature above 20°C during summer. E. cava exhibited very low recruitment during spring-summer. However, high recruitment was observed on April 2015 when canopy cover was very low due to low density. This indicates that recruitment of E. cava was controlled not by seasonal effects but by physical factors such as canopy and space. The mortality rate of juvenile plants was highest due to their unstable settlement. By June 2015, 34 months after the disturbances, E. cava was almost recovered to the pre-disturbance population size structure. These results suggest that recovery of kelp forest following the large-scale disturbance requires a

Impact of Super Typhoon ‘Hinnamnor’ on Density of Kelp Forest and Associated Benthic Communities in Jeju Island, Republic of Korea

“…Large typhoons severely impact marine ecosystems; for instance, macroalgal communities in California have been shown to take several months to more than a decade to regain their original state of stability [30]. Around Jeju Island, Kim et al [31] reported a recovery time of 34 months for a typhoon-damaged E. cava population. Currently, some studies focus on the decline of E. cava populations due to climate change.…”

Environmental impact on marginal coastal benthic communities within the Jeju Island, South Korea temperate transition zone

“…Indeed, temperate kelps, such as E. cava, are heat-sensitive (Wernberg et al, 2011(Wernberg et al, , 2016 (Supplementary Table 2) and, like hard corals, may be limited by water temperature in winter. The optimal water temperature for E. cava growth during winter is 15-18°C, while water temperatures above 20°C in summer can inhibit growth, although promoting reproductive potential (Yokohama et al, 1987;Kim et al, 2016). At SS, mean SST in February and May were nearly 15°C and 17°C, respectively, lying within the range of E. cava's optimal temperature.…”

Threats to a Temperate Kelp Forest Species, Ecklonia cava, through Tropical Fish Herbivory Associated with Sea Surface Warming in the East China Sea

“…On the other hand, E. cava has been reported to have the lowest growth at high elevated temperatures (>25 °C), so the summer season of 2023 would have been even more adverse for this species [1,11]. In addition, high pressure of herbivory potentially will inhibit E. cava reproduction, as the maturation of E. cava with sorus is known to peak around October and spore release occurs during the fall season in Korean waters [21]. The significant increase in rabbitfish feeding on local kelp forests coincides with the sea surface warming around the northern East China Sea and the Korean Peninsula, which was recorded along with a strengthened positive SST anomaly from August to November 2023 (Figure 1).…”

“…On the other hand, E. cava has been reported to have the lowest growth at high elevated temperatures (>25 • C), so the summer season of 2023 would have been even more adverse for this species [1,11]. In addition, high pressure of herbivory potentially will inhibit E. cava reproduction, as the maturation of E. cava with sorus is known to peak around October and spore release occurs during the fall season in Korean waters [21].…”

“…So far, large-scale mortality of the E. cava population around the Korean Peninsula has been reported due to typhoon occurrence and to herbivores such as gastropods and echinoderms; however, the impacts of tropical herbivore fish on the population in this region have not yet been reported [21,22]. The evidence in overgrazing of temperate kelp species by tropical herbivory has already been identified in Japan and in the Mediterranean, but information on specific mechanisms that facilitate this shift is still scarce [23,24].…”