Seaweed Aquaculture 'Expands Ecosystems': First Quantitative Demonstration Across 6 National Sea Areas. 'GOOD SEA Future Report Vol. 2' Released.

General Incorporated Association GOOD SEA (Representative Director: Shogo Arai, Headquarters: Nerima-ku, Tokyo) has released 'GOOD SEA Future Report Vol. 2,' which verifies the impact of seaweed aquaculture on marine ecosystems. This study, supported by The Nippon Foundation, quantitatively examined the effects of seaweed aquaculture on surrounding biological communities in six sea areas nationwide. The results revealed that seaweed aquaculture plays a role in forming and expanding ecosystems, not only by increasing biomass and species count but also by establishing food chains within the aquaculture beds. Aquaculture beds (養殖藻場): An environment formed by cultivating seaweed in the sea using ropes or cages. This concept, advocated by General Incorporated Association GOOD SEA, involves growing seaweed suitable for the specific sea area to enhance biodiversity and restore/foster marine ecosystems. Background: In recent years, 'isoyake' (barren grounds) has been progressing across Japan, and the decrease in seaweed beds has become a serious issue. Seaweed is a crucial foundation supporting marine ecosystems, functioning in water purification, carbon sequestration, and as habitat and food resources for marine organisms. However, quantitative verification of how seaweed aquaculture affects these ecosystems, despite being considered 'good for the environment,' has been limited. Against this backdrop, GOOD SEA has continuously conducted scientific studies since fiscal year 2023 to verify the ecological impact of seaweed aquaculture. Survey Implementation Overview: In fiscal year 2024, surveys were conducted on seaweed aquaculture beds in six sea areas nationwide. In each sea area, aquaculture beds and control areas were set up to compare changes in biological communities. [Ecosystem Survey Implementation Overview] ■ Survey Period: October 2024 - July 2025 ■ Survey Locations: 6 sea areas nationwide: Hokkaido Hakodate (Makonbu), Miyagi Ishinomaki (Wakame), Shizuoka Nishiizu (Tosakanori), Ehime Imabari (Hijiki, Futomozuku), Yamaguchi Shimonoseki (Futomozuku), Kumamoto Amakusa (Mirin). ■ Survey Scale: 27 surveys conducted across 6 sea areas and 6 species in aquaculture beds. Main Survey Results: 1. Biomass and species count increased in all sea areas. In all categories (diatoms, epifauna, fish), both biomass and species count increased more within the aquaculture beds than outside. Diatoms: Max 11.2x (species count) / Max 48x (biomass). Epifauna: Max 14x (species count). Fish: Max 9x (species count). 2. Chain-like increase from microorganisms to fish. Due to the presence of seaweed, diatoms increased as an attachment substrate, followed by an increase in epifauna feeding on them, and further an increase in fish preying on epifauna, confirming a stepwise increase in biological communities. 3. Food chain established within aquaculture beds. Gastric content analysis confirmed that fish consumed 12-36% epifauna, and epifauna consumed 8-37% diatoms. This indicates the establishment of an independent food chain within the aquaculture beds. 4. Seaweed aquaculture 'expands ecosystems.' The survey results showed that seaweed aquaculture does not significantly alter the structure of ecosystems but rather plays a role in increasing and expanding existing biological communities. Excerpt from the report (p.21): Schematic diagram of the food chain within aquaculture beds. A stepwise food chain is formed, starting with diatoms attached to the seaweed surface, followed by epifauna consuming them, and then fish preying on epifauna. Excerpt from the report (p.29): Summary of survey results conducted in 6 sea areas nationwide. It was confirmed that seaweed aquaculture increases biological communities such as diatoms, epifauna, and fish, and establishes food chains within the aquaculture beds. Seaweed aquaculture was shown to expand ecosystems rather than change them. Awareness Activities and Content Release: In conjunction with the release of these survey results, GOOD SEA has published explanatory articles on its website to broaden understanding of the survey content and the role of seaweed. GOOD SEA is working to expand understanding of marine ecosystems not only through research but also through information dissemination and awareness activities.