Establishing an Oceanic Environment in Space: A “Core-Biome” for Isolated Ecosystems

This study aims to establish an oceanic environment suitable for space as a critical component of the terrestrial ecosystem, termed the "Core-Biome." The Core-Biome represents an essential habitat for supporting human life in isolated environments. Among terrestrial ecosystems, the ocean remains the last frontier to be replicated in space due to the following challenges; difficulties in managing saline water in closed systems it is unsuitable for direct consumption or agricultural irrigation, challenges in maintaining water quality, essential for cultivating aquatic organisms, and the complexity of identifying primary producers within the ocean ecosystem. In our study, we aim to cultivate corals in a closed ecosystem by introducing three distinct species: Porites cylindrica (a common species found in the Okinawa region), Acropora tenuis (known for its thin branches and resilience to shock compared to other Acropora species), and Acropora intermedia (a branching Acropora species commonly found near Iriomote Island). We established a closed aquarium system where water is recycled using a protein skimmer and a calcium reactor, with partial water replacement when necessary. Growth rates for each coral species were measured under controlled conditions, maintaining a uniform temperature of 27°C and a diurnal light cycle. Dissolved oxygen levels were sustained solely through photosynthesis by coral-associated zooxanthellae. The material balance, optimal growth conditions, and key findings from this study will be presented at the conference.