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This study quantified the spatial variation of endophyte infections in wild populations of commercially important Chondrus ocellatus in Korea. We examined the variation of infection across four locations, two tidal heights and life-history stage (gametophyte vs tetrasporophyte). One hundred and fifty fronds were collected from the upper and lower C. ocellatus zones and microscopic examinations were conducted to determine their infection symptoms. Our results showed that the percentage of C. ocellatus populations infected by endophytic algae were very high, ranging from 58 to 99%, in all populations examined. Endophyte infection severity of Hakampo and Manripo populations was significantly greater in the lower Chondrus zones but it was significantly higher in the upper zone of Jungdori population. Tetrasporophytic fronds were more susceptible to infection by endophytic algae than gametophytic fronds. Also, the infection symptoms were more severe in the middle and basal parts of the fronds than in the apical parts. The findings of this study are very informative data for the endophyte abundance in the field population of commercial C. ocellatus.

Five polyketides, paralactonic acids A-E (1-5) were isolated from Paraconiothyrium sp. SW-B-1, an endophytic fungus isolated from the seaweed, Chondrus ocellatus Holmes. Their structures were determined by various spectroscopic methods, predominantly by 2D NMR spectroscopic analyses. The absolute configurations of compounds 1-5 were determined by comparison of the experimental and calculated ECD spectra. Compound 5 showed moderate antibacterial activity and restored the growth of a mutant yeast strain inhibited by hyperactivated Ca2+-signaling.

The growth, reproduction, gametophyte(G)/tetrasporophyte(T) ratio, and diseases of Chondrus ocellatus populations were examined at 3 sites (Samcheok, Youngduk, Pohang) of East coast and at 2 sites (Hakampo, Manripo) of West coast in between July and August, 2013. Average plant lengths were 6.10~9.69 cm and it was minimum at Manripo and maximum at Pohang population. In general, average plant length and weight of C. ocellatus were greater on East coast than West coast populations. The proportion of vegetative plant was between 26.7~66.7 %, and G/T ratio of total plants including vegetative plants after testing resorcinol method was 3:2 on the East coast where is gametophyte dominant area. However, G/T ratio was 1:1 at Hakampo and 1:2.3 at Manripo representing tetrasporophyte dominance. In the present study, Korean C. ocellatus have various diseases (white colour and green colour), an endophytic alga(Ulvella sp.), and many epiphytic macroalgae and diatoms. Healthy C. ocellatus plants were about 20~40 % in summer population and most of plants had disease. Chondrus ocellatus had a filamentous green alga, endophytic Ulvella sp. which was not identified. The endophyte is easily observed in C. crispus growing in Europe and Canada and it is recognised as a pathogen destroying population and reducing yield of C. crispus. Thus more interest and research on the endophytic algae and disease of C. ocellatus are required.

The species composition and variation of marine plants at Saguenjin in the east coast of Korea were investigated monthly from October 2008 to December 2009. As a result, 92 species of marine plants identified, 91 species were seaweeds (7 green algae, 22 brown algae, 62 red algae) and 1 were sea grass. Dominant species in importance value were melobesioidean algae, Ulva pertusa and Phyllospadix iwatensis. The vertical distribution of algae were characterized by melobesioidean algae, U. pertusa at 3 m depth, melobesioidean algae, P. iwatensis and U. pertusa at 5 m depth and melobesioidean algae, Chondrus ocellatus and Prionitis cornea at 10 m depth.

1. The mucilage of Chondrus ocellatus Holmes has been investigated by the partial methanolysis method. 2. A new disaccharide, the structure of which is shown to be 4-O-β-D-galactopyranosyl-3,6-anhydro-D-galactose, has been isolated in the form of its dimethylacetal and methyl β-glycoside in a good yield. 3. The disaccharide has been named carrabiose. 4. It has been suggested that 1→3′ linked carrabiose represents the repeating unit for the most part of the carbohydrate of the Chondrus mucilage.