Conservation of macroalgal beds
海洋生物資源科学部門・海洋共生学分野・海藻学教室の紹介です
Recently, the reduction of macroalgal beds has been reported in many parts of the world, which is termed as isoyake in Japan. Isoyake is defined as "a phenomenon in which, in the shallow coastal area, macroalgal beds decrease or disappear significantly beyond the range of their phenology, resulting in a poor vegetation state. When isoyake occurs, the seafloor becomes simple state (Figs. 7-9), and the ecosystem collapses. As a result, biodiversity declines and coastal fisheries are severely damaged. In some cases, sea urchins are dominant, but they are usually not target for fishing. This is because sea urchins are unable to develop gonads that we usually eat when the urchins cannot feed enough. However, sea urchins can survive in poor vegetation conditions because of their high tolerance to starvation.
Although there are various factors reported for the reduction of macroalgal bed, the state devoid of macroalgae maintains due to abnormal balance of macroalgae and herbivores. To restore the state of isoyake, it is necessary to manipulate the balance.
Isoyake has been known for a long time in Japan. The reduction of macroalgae beds was documented in the late 18th century, and isoyake was discussed in "kaisou gensyou ron" in a textbook titled
kaisan shokubutsu gaku
(1911) written by Kichisaburo Endo. However, whether due to increased human activity or environmental change, the number of reports of Isoyake has increased dramatically in recent years. Restoration
of seaweed beds is necessary to maintain the biodiversity of coastal areas and rich coastal fisheries.