Chonnam National University - Guemo-ri

Restoration Project

Chonnam National University - Guemo-ri

Restoration Objective:

Restoration of seaweed beds is desirable as the loss of seaweed beds results in the decline of fishery resources and coastal water quality. Construction of artificial seaweed beds has become a popular method of maintaining natural ecosystems. The objective of this paper was to determine the effectiveness of artificial Sargassum beds in helping to restore barren grounds in the coastal areas of Jeju Island.

Site Selection Criteria:

A 3-5m deep seafloor in an embayed coast was chosen as the site for intermediate cultivation of germlings. The selected location was calm, and its gravel bottom was flat enough to stabilize the protective nets for the substrata. Then, the cultured germlings were transplanted to barren grounds near a village fishing place that previously had seaweed present.

Cause Of Decline:

Seaweed beds have been declining due to multiple anthropogenic factors. Hypotheses for causes of seaweed declines include high water temperatures caused by the El Niño phenomenon, low nutrition from the Kurushio current, water pollution and excessive grazing by invertebrates and fishes. The loss of seaweed habitat reduces important habitats and spawning beds for fisheries species, and reduces coastal biodiversity.

Key Reasons For Decline:


Scientific Paper

Sargassum bed restoration by transplantation of germlings grown under protective mesh cage

J.T. Yoon, S.M. Sun, G. Chung
Journal of Applied Phycology, Vol. 26.

Site Observations:

Observation Date

25th Dec 2007 – 23rd Feb 2008

Action Summary:

Fertilized eggs of Sargassum fulvellum and Sargassum horneri were induced from receptacles of mature plants and adhered to concrete block substrata. When the germlings that settled on the artificial substrata had grown to 3–5mm in indoor cultures, they were moved to the ocean for intermediate cultivation under seed-cultivating nets to prevent damage from grazing animals. After the germlings had grown to 25–50cm, the artificial substrata with settled germlings were taken out from the protective cage and transplanted on the barren grounds along the coast of Jeju Island.

Lessons Learned:

The method of culturing in the lab, then growing in the field with protection before transplanting to barren grounds showed some merit. The Sargassum near the edges of concrete blocks was partially eaten by herbivores which infers providing extra protection in this vulnerable life stage increases transplantation success. There was a lack of reporting of survival rate, but the 'formation of a marine forest' indicates the project was highly successful.

Project Outcomes:

The germlings settled on the artificial substrata grew faster in the sea than indoors and were 2–5cm by August. Most germlings in the protective cage were free from damage by fish, while the gastropod Cerithideopsilla cingulata caused minute damage to S. horneri germlings. Because of the flat concrete blocks, even the Sargassum holdfasts were occasionally exposed and eaten by the mollusc. S. fulvellum suffered less damage than S. horneri; and the damage was limited to the soft upper part of the plants. Individuals free from the animal grazing damage grew to 14–29 cm by late October. The growth of S. horneri was slow compared to S. fulvellum in the early stage, while the plants showed rapid growth from two months post-transplantation and were free from grazing damage. Most of the Sargassum had grown to over 300 cm by 6 months post-transplantation, and were forming a marine forest community at the transplant sites.

Nature of Disturbance:

Once Sargassum germlings were transplanted to barren grounds, some of the plants were immediately damaged by inhabitant grazing animals such as Astralium haematragum, Batillus cornutus, Chlorotoma lischkei and Anthocidaris crassispina. The thalli and holdfasts of the plants growing on the edges of concrete blocks were easily damaged by the grazing animals, and damage lasted for at least 1 month.

Key Reasons For Decline:


Area of Restoration (Ha)


Indicator Data:


Ending Value:

Starting Value:

Presence / Absence of Kelp