To examine the effects of increased CO 2 concentration and seawater temperature on the photosynthesis and growth of forest forming Ecklonia cava (Laminariales, Phaeophyta), sporophytic discs and gametophytes were cultured under three pCO 2 concentrations (380, 750, 1000 ppm), four temperatures (5, 10, 15, 20 o C for sporophytes; 10, 15, 20, 25 o C for gametophytes), and two irradiance levels (40, 80 µmol photons m −2 s −1) for 5 days. Photosynthetic parameter values (ETR max , E k , and α) were generally higher as sporophytic discs were grown under low temperature and increased CO 2 concentration at 750 ppm. However, photosynthesis of Ecklonia sporophytes was severely inhibited under a combination of high temperature (20 o C) and 1000 ppm CO 2 concentration at the two photon irradiance levels. The growth of gametophytes was maximal at the combination of 380 ppm (present seawater CO 2 concentration) and 25 o C. Minimal growth of gametophytes occurred at enriched pCO 2 concentration levels (750, 1000 ppm) and high temperature of 25 o C. The present results imply that climate change which is increasing seawater temperature and pCO 2 concentration might diminish Ecklonia cava kelp beds because of a reduction in recruitments caused by the growth inhibition of gametophytes at high pCO 2 concentration. In addition, the effects of increased temperature and pCO 2 concentration were different between generations-revealing an enhancement in the photosynthesis of sporophytes and a reduction in the growth of gametophytes.

In total, 86 macroalgal species were identified, including 12 green, 19 brown, and 55 red algae; 67 species at Heuksando and 70 species at Hongdo, were observed. Annual seaweed biomass was 252.44 g dry wt / m 2 at Heuksando and 217.67 g dry wt/m 2 at Hongdo. The dominant seaweed in importance value (IV > 15) differed between the sites: Sargassum thunbergii at Heuksando and Corallina pilulifera at Hongdo. The vertical distribution pattern of seaweeds from the upper to lower intertidal zones at Heuksando was Gloiopeltis spp., Ulva spp.-S. thunbergii, S. fusiforme, Hildenbrandia rubra-S. thunbergii, C. pilulifera. On the rocky shore of Hongdo, seaweed zonation was distinct: Porphyra yezoensis, Gloiopeltis spp., Ulva spp.-C. pilulifera, S. fusiforme, Myelophycus simplex-Chondrus ocellatus, C. pilulifera, and Carpopeltis affinis. Annual seaweed coverage, richness index (R), evenness index (J'), and diversity index (H') values were greater at Hongdo (41.35%, 12.82, 0.59, and 2.50 respectively) than at Heuksando (31.54%, 11.93, 0.44, and 1.87 respectively), which may indicate that the seaweed community at Hongdo is more stable relative to the one at Heuksando.

Seasonal variability in the marine seaweed community structure was examined in the intertidal zones at nine study sites in Hallyeohaesang National Park, on the southern coast of Korea from March to October 2014. A total of 145 seaweeds were indentified, comprising 15 green, 41 brown and 89 red algae. Coarsely branched seaweeds were the dominant functional group, comprising 58.95% in species number, whereas filamentous, sheet, thick leathery, crustose and jointed calcareous forms comprised 2.63-17.72% each. The seaweed biomass averaged 358.00 g dry wt/ m 2 and it was maximal at Somaemuldo (847.64 g dry wt/m 2 ) and minimal at Gamam (56.51 g dry wt/m 2 ). Based on biomass, the dominant and subdominant seaweeds were Ulva australis at Gamam, Sargassum thunbergii at Sangju, Ulva australis and S.fulvellum at Neukdo, S.horneri at Dala-Bijindo-Somaemuldo, S. thunbergii at Dapo, and Corallina pilulifera at Songdo. Community indices were as follows: dominance index (DI), 0.43-0.71; richness index (R), 8.26-16.50; evenness index (J'), 0.36-0.54; and diversity index (H'), 1.57-2.19. In conclusion, we found that both biomass and the community structure of seaweeds in Hallyeohaesang National Park were similar to those in other studies of the Southern Sea along the Korean peninsula, and that Hallyeohaesang National Park is a relatively favorable habitat for seaweeds. Future studies should examine the changes in seaweed composition and biomass as they relate to climate change and environmental pollution.Key words: Biomass, Community structure, Seaweed, Hallyeohaesang National Park This is an Open Access article distributed under the terms of the Creative Commons Attribution Non-Commercial Licens (http://creativecommons.org/licenses/by-nc/3.0/) which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited.

The effects of temperature on spore release, growth and photosynthetic efficiency of Lithophyllum yessoense and Hildenbrandia rubra were examined. L. yessoense was collected at Galnam and H. rubra was collected at Gyeokpo, Korea. The experimental temperatures were different for spore release (10, 15, 20℃), sporeling growth (10, 15, 20, 25, 30℃) and photosynthetic efficiency (10, 15, 20, 25℃). All other culture conditions were the same: 34 psu, 12:12 LD and 50 μmol photon m -2 s -1 . Spore liberation was maximal at 10℃ for L. yessoense and at 20℃ for H. rubra. After 14 days, the surface area of L.yessoense was 0.031 mm 2 at 25℃ and for H. rubra was 0.032 mm 2 at 20℃. Sporelings of L. yessoense were a dark-red color and grew in a round shape. In contrast, H. rubra was bright pink and changed from a round shape in the early growth stage to later become flabelliform. Photosynthetic efficiency was highest between 20-25℃ in both species. In conclusion, L. yessoense and H. rubra display different physiological features based on the optimal temperatures for spore release and sporling growth.

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