World of Underwater Forest

Sargassum horneri (Kumamoto Pref)
Can you imagine a world of underwater forests?

Underwater forests, also known as "Moba" in Japanese, are highly dense communities of seaweed (including seagrass) and are recognized as one of the most productive ecosystems in the coastal areas worldwide. In Japan, we can find a diverse range of seaweed forests, including kelp (Laminaliales) and Sargassum (Fucales) with over 1500 species of seaweed. These forests provide three-dimensional habitats for marine organisms and support their biodiversity.

These communities are strongly influenced by a variety of eco-environmental factors such as light, temperature, nutrients, wave motion, and grazers. However, the continued changes in the coastal environment, caused by climate change and human activities, may lead to the degradation of this habitat and result in the loss of biodiversity. In fact, the area of Japanese seaweed/seagrass communities has decreased by around 40% in the past 30 years, and the species composition of seaweed has also changed throughout Japan. Subtropical seaweeds have been observed in the transitional area between temperate and subtropical regions of southern Japan.

To conserve the biodiversity of coastal ecosystems, further studies on seaweed ecology and diversity are strongly needed.


Saccharina japonica


Eggs of squid in Sargassum bed