Seaweed Farming 'Expands Ecosystems': First Quantitative Proof from Surveys in 6 Coastal Areas. 'GOOD SEA Future Report Vol. 2' Released
Good Sea released a report proving seaweed farming expands ecosystems. A survey across 6 Japanese coastal areas showed it increases biomass, species count, and forms new food chains.
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- 📰 Published: April 13, 2026 at 20:00
- 🔍 Collected: April 13, 2026 at 16:35
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General Incorporated Association Good Sea (Representative Director: Shogo Arai, Headquarters: Nerima-ku, Tokyo, hereinafter 'Good Sea') has released the 'GOOD SEA Future Report Vol. 2', which verifies the impact of seaweed farming on marine ecosystems.
This survey was conducted with the support of The Nippon Foundation to quantitatively verify the impact of seaweed farming on surrounding biological communities in six coastal areas across Japan. The results revealed that seaweed farming not only increases biomass and the number of species, but also plays a role in forming and expanding ecosystems by establishing a food chain within the cultivated seaweed beds*.
*Cultivated seaweed beds: Environments formed by cultivating seaweed in the ocean using ropes and baskets. This is a concept advocated by Good Sea, functioning to enhance biodiversity and restore/nurture marine ecosystems by growing seaweed suitable for the specific area.
Background
In recent years, the progression of 'Isoyake' (marine desertification) and the severe decline of seaweed beds have become serious issues across Japan. Seaweed is a crucial foundation supporting marine ecosystems, functioning not only for water purification and carbon fixation but also as habitats and food resources for fish and shellfish. On the other hand, while seaweed farming is widely considered 'good for the environment', there have been limited quantitatively verified cases regarding exactly how it impacts these ecosystems.
Given this background, Good Sea has been continuously conducting surveys since fiscal 2023 to scientifically verify the impact of seaweed farming on ecosystems.
Survey Overview
In fiscal 2024, surveys were conducted targeting cultivated seaweed beds in six coastal areas nationwide. In each area, cultivated beds and control zones were established to compare changes in biological communities.
[Ecosystem Survey Overview]
■ Survey Period
October 2024 – July 2025
■ Survey Locations
6 coastal areas nationwide
- Hakodate City, Hokkaido (Saccharina japonica)
- Ishinomaki City, Miyagi Prefecture (Wakame)
- Nishi-Izu Town, Shizuoka Prefecture (Tosakanori)
- Imabari City, Ehime Prefecture (Hijiki, Futomozuku)
- Shimonoseki City, Yamaguchi Prefecture (Futomozuku)
- Amakusa City, Kumamoto Prefecture (Mirin)
■ Survey Scale
Conducted a total of 27 surveys across 6 areas and 6 seaweed species in cultivated beds.
Main Survey Results
1. Increase in Biomass and Species Count in All Areas
For diatoms, epifauna, and fish, both the biomass and the number of species increased inside the cultivated seaweed beds compared to the outside.
Diatoms: Up to 11.2 times (species) / Up to 48 times (amount)
Epifauna: Up to 14 times (species)
Fish: Up to 9 times (species)
2. Sequential Increase from Microorganisms to Fish
A structural sequential increase was confirmed: the presence of seaweed increased diatoms as an attached substrate, which led to an increase in epifauna feeding on them, and subsequently an increase in fish preying on the epifauna.
3. Establishment of a Food Chain within Cultivated Beds
Stomach content analysis confirmed that fish prey on epifauna by 12-36%, and epifauna consume diatoms by 8-37%. This indicated that an independent food chain is established within the cultivated seaweed beds.
4. Seaweed Farming 'Expands Ecosystems'
The survey results indicated that seaweed farming does not drastically alter the structure of the ecosystem, but rather plays a role in increasing and expanding the existing biological communities.
About Educational Activities and Content Publication
Coinciding with the release of these survey results, Good Sea has published explanatory articles on its website to help the public broadly understand the survey details and the role of seaweed. Good Sea is committed to spreading an understanding of marine ecosystems not only through surveys and research but also through such information dissemination and educational activities.
In addition to explaining the survey results, these articles introduce the relationship between seaweed and ecosystems, as well as the background of aquaculture technology in a way that is easy for the general public to understand.
This survey was conducted with the support of The Nippon Foundation to quantitatively verify the impact of seaweed farming on surrounding biological communities in six coastal areas across Japan. The results revealed that seaweed farming not only increases biomass and the number of species, but also plays a role in forming and expanding ecosystems by establishing a food chain within the cultivated seaweed beds*.
*Cultivated seaweed beds: Environments formed by cultivating seaweed in the ocean using ropes and baskets. This is a concept advocated by Good Sea, functioning to enhance biodiversity and restore/nurture marine ecosystems by growing seaweed suitable for the specific area.
Background
In recent years, the progression of 'Isoyake' (marine desertification) and the severe decline of seaweed beds have become serious issues across Japan. Seaweed is a crucial foundation supporting marine ecosystems, functioning not only for water purification and carbon fixation but also as habitats and food resources for fish and shellfish. On the other hand, while seaweed farming is widely considered 'good for the environment', there have been limited quantitatively verified cases regarding exactly how it impacts these ecosystems.
Given this background, Good Sea has been continuously conducting surveys since fiscal 2023 to scientifically verify the impact of seaweed farming on ecosystems.
Survey Overview
In fiscal 2024, surveys were conducted targeting cultivated seaweed beds in six coastal areas nationwide. In each area, cultivated beds and control zones were established to compare changes in biological communities.
[Ecosystem Survey Overview]
■ Survey Period
October 2024 – July 2025
■ Survey Locations
6 coastal areas nationwide
- Hakodate City, Hokkaido (Saccharina japonica)
- Ishinomaki City, Miyagi Prefecture (Wakame)
- Nishi-Izu Town, Shizuoka Prefecture (Tosakanori)
- Imabari City, Ehime Prefecture (Hijiki, Futomozuku)
- Shimonoseki City, Yamaguchi Prefecture (Futomozuku)
- Amakusa City, Kumamoto Prefecture (Mirin)
■ Survey Scale
Conducted a total of 27 surveys across 6 areas and 6 seaweed species in cultivated beds.
Main Survey Results
1. Increase in Biomass and Species Count in All Areas
For diatoms, epifauna, and fish, both the biomass and the number of species increased inside the cultivated seaweed beds compared to the outside.
Diatoms: Up to 11.2 times (species) / Up to 48 times (amount)
Epifauna: Up to 14 times (species)
Fish: Up to 9 times (species)
2. Sequential Increase from Microorganisms to Fish
A structural sequential increase was confirmed: the presence of seaweed increased diatoms as an attached substrate, which led to an increase in epifauna feeding on them, and subsequently an increase in fish preying on the epifauna.
3. Establishment of a Food Chain within Cultivated Beds
Stomach content analysis confirmed that fish prey on epifauna by 12-36%, and epifauna consume diatoms by 8-37%. This indicated that an independent food chain is established within the cultivated seaweed beds.
4. Seaweed Farming 'Expands Ecosystems'
The survey results indicated that seaweed farming does not drastically alter the structure of the ecosystem, but rather plays a role in increasing and expanding the existing biological communities.
About Educational Activities and Content Publication
Coinciding with the release of these survey results, Good Sea has published explanatory articles on its website to help the public broadly understand the survey details and the role of seaweed. Good Sea is committed to spreading an understanding of marine ecosystems not only through surveys and research but also through such information dissemination and educational activities.
In addition to explaining the survey results, these articles introduce the relationship between seaweed and ecosystems, as well as the background of aquaculture technology in a way that is easy for the general public to understand.