Eun Kyoung Hwang

Artificial seed production and cultivation of the edible brown alga, Sargassum fulvellum (Turner) C. Agardh: Developing a new species for seaweed cultivation in Korea

Sargassum fulvellum is a brown alga recently introduced to the seaweed cultivation industry in Korea. There is current interest in the commercial scale of aquaculture of this species. For the artificial seeding and cultivation of this alga, growth and maturation were investigated from September 2002 to August 2003. Indoor culture experiments for maturation induction were also conducted at temperatures of 5, 10, 15, 20 and 25 ∘C and irradiances of 20, 50, 80 and 100 μmol photons m−2 s−1 under 16:8 h (L:D) photoperiod. Within a given culture test range, higher temperature and irradiance levels favoured the maturation of receptacles in S. fulvellum. Using temperature and irradiance control for thalli, artificial seed production of this species could be done one month earlier than thalli matured in nature. Under natural condition, receptacle formation of the plants began in February, and the eggs were released from March to April. For mature thalli of 200 g wet wt., artificial seeding was complete enough for attachment on seed strings of 100 m. Mean production obtained from the artificial seeding technique in situ was 3.0 kg wet wt m−1 of culture rope during the cultivation period.

The occurrence of pinhole disease in relation to developmental stage in cultivated Undaria pinnatifida (Harvey) Suringar (Phaeophyta) in Korea

Infection rates of pinhole disease in farmed Undaria pinnatifida (Harvey) Suringar were examined between November 2002 and April 2003 at an Undaria farm at Wando on the southwestern coast of Korea. The growth stages of U. pinnatifida can be defined as: a growth phase from December to the end of February, and a decay phase from March to April. There was a significant increase in the level of infection with pinhole disease (measured as the number of pinholes per cm2) between December and April (P < 0.01). Infection progressed from the upper part of the frond in December to the basal part in April. The infection rate of pinhole disease in relation to growth phase on farms over time is limited by the harvest of the seaweed crop at the end of the cultivation period in April. The midrib, sporophyll and stipe showed no signs of infection at any time during the cultivation period. The reduced physiological activity and tissue aging that occurred over time in the sporophytic life phase is the probable cause of the increasing infection rate of the disease.

Seasonality of epiphytic development of the hydroid Obelia geniculata on cultivated Saccharina japonica (Laminariaceae, Phaeophyta) in Korea

The occurrence of encrusting colonies of the hydroid Obelia geniculata on farmed Saccharina japonica was examined between December 2007 and July 2008 at a Saccharina farm at Wando on the southwestern coast of Korea. The growth stages of S. japonica can be divided into two phases: an active growth phase from February to the end of May and a decay phase from June to July. There was a significant increase in the level of incrustation by colonies on fronds (measured as the percentage of fronds with encrusting colonies) between February and July (p < 0.05). The encrusting colonies occurred first on the upper part of the frond in February and progressed to the basal part in July. The abundance of encrusting colonies in relation to the growth phase on farms over time was limited by the harvest of the seaweed crop at the end of the cultivation period in July. The stipes and holdfasts of fronds showed no signs of infestation at any time during the cultivation period. The extent of the infestation appeared to be related to a combination of factors. These could be reduced physiological activity and subsequent tissue aging that occurred simultaneously in the sporophytic life phase of Saccharina frond, and a rapid increase in reproduction and growth of O. geniculata coinciding with rising seawater temperature.

Cultivation of a hybrid of free-living gametophytes between Undariopsis peterseniana and Undaria pinnatifida: morphological aspects and cultivation period

The kelp Undariopsis peterseniana is warm-water-tolerant, and consequently, there is currently considerable interest in developing commercial cultivation techniques for this species in Korea. U. peterseniana plants have been successfully transferred to the northern coast of Korea beyond their original habitat in Jeju Island (33°30′08.65″N, 126°55′39.02″E). In this study, we cultured a hybrid kelp consisting of a cross between free-living gametophytes of U. peterseniana and U. pinnatifida in an attempt to extend the culture period of Undaria which is an important species for both the abalone industry and for commercial seaweed mariculture for human food applications. Morphological characters and cultivation period were compared between the parent thalli and the hybrid. The cultivation experiment was conducted in Wando, on the southern coast of Korea (34°26′18.68″N, 127°05′43.88″E). The morphological characteristics of the hybrid thalli were intermediate between the two species having shallow pinnated blades and a reduced reproductive organ. Hybrid thalli showed faster growth rates, 1.5 times greater biomass, and a longer cultivation period than the parent thalli. The hybrid strain possessed characteristics that indicate it could be used as an alternative kelp source to supply the abalone feed industry.

Bloom of a Filamentous Green Alga Cladophora vadorum (Areschoug) Kützing and Nutrient Levels at Shangrok Beach, Buan, Korea

A filamentous green alga Cladophora vadorum (Areschoug) Kutzing, bloomed at Shangrok Beach, Buan, Republic of Korea, in September 2015. This alga is currently distributed worldwide. Concentrations of total nitrogen (TN), total phosphorus (TP), dissolved inorganic nitrogen (DIN), and dissolved inorga...