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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.

To examine optimal growth conditions of the edible green alga Caulerpa okamurae, thalli of this species were cut into erect frond (3 cm long) and stolon (5 cm long) fragments. They were cultured in combinations of four temperatures (15, 20, 25, and 30 °C), three irradiances (20, 40, and 80 μmol photons m−2 s−1), four daylengths (8, 12, 16, and 24 h), and seven salinities (15, 20, 25, 30, 35, 40, and 45 psu). After 12 days, maximal relative growth rates (RGRs) for erect fronds (6.78% day−1) and stolons (7.02% day−1) occurred at 25 °C and 40 μmol photons m−2 s−1. At 30 °C, growth differences were found; negative growth for erect fronds and positive growth for stolons, with an average RGR of 1.96% day−1. A daylength of 16 h and salinity of 30 psu were needed for maximal growth of erect fronds and stolons. Stolon exhibited a greater tolerance to high and low temperatures and low salinity than erect fronds. Thalli weight of C. okamurae was increased by increments of stolon length, new erect fronds, and new ramuli. In conclusion, C. okamurae should be cultivated in summer with high seawater temperature (25 °C) and long daylength, in waters of 30 psu, and at a water depth providing 40 μmol photons m−2 s−1. These physiological and growth pattern data are informative for the successful development of commercial cultivation of C. okamurae.