Microalgae are the backbone of many aquaculture systems, serving as a primary feed for fish, shellfish, and other marine species. However, traditional indoor cultivation methods require controlled environments, leading to high costs and energy consumption. Could outdoor farming of microalgae provide a more sustainable and affordable solution?
Seychelles, with its abundant sunlight and warm tropical climate, offers a promising setting for outdoor microalgae cultivation. A recent experiment done by the Aquaculture Research team tested whether microalgae species like Tetraselmis spp. and Chaetoceros muelleri could thrive in outdoor conditions. The results suggest that with the right balance of light and temperature management, outdoor production could become a feasible and cost-effective alternative.
Why is Microalgae Important for Aquaculture?
Microalgae serve as a primary food source in hatcheries, supplying essential lipids, proteins, and vitamins. They are particularly vital for:
- Fish larvae – providing nutrients for healthy growth.
- Shellfish (oysters, clams, mussels) – supporting filter-feeding species.
- Shrimp and crustaceans larvae – improving survival rates in early development.
However, cultivating microalgae indoors requires sophisticated equipment, controlled lighting, and stable temperatures—driving up operational costs. Outdoor cultivation, on the other hand, takes advantage of natural sunlight and warm climates, potentially offering a more sustainable approach.
Figure1. Containerized indoor microalgae cultivation setup at the Seychelles Fisheries Authority, Providence
Why grow microalgae outdoors?
Seychelles, located near the equator, enjoys stable high temperatures and abundant sunlight throughout the year. These conditions are similar to the controlled environments used in indoor microalgae production, making outdoor farming a feasible option.
By moving microalgae production outdoors, aquaculture farms in Seychelles could:
✅ Reduce energy costs
✅ Lower their carbon footprint
✅ Increase accessibility for small-scale farmers
✅ Improve overall sustainability of seafood production
Figure 2. Experimental setup: The plastic tank on the left holds carboys for the cooled treatments with ambient sea temperature water flowing through, while the tank on the right holds carboys for the uncooled treatments.
Key Research Findings: What Works Best?
A study conducted at the Seychelles Fisheries Authority tested two important microalgae species:
- Chaetoceros muelleri – a diatom commonly used in sea urchin, oyster and sea cucumber hatcheries.
- Tetraselmis spp. – a green microalga rich in essential fatty acids for fish and shrimp.
The experiment evaluated various environmental conditions, comparing:
- Shaded vs. Unshaded tanks (to measure the effects of direct sunlight).
- Cooled vs. Uncooled systems (to regulate water temperature).
- Outdoor vs. Indoor control groups (to compare growth efficiency).
The Best Conditions for Growth
- Chaetoceros muelleri thrived outdoors in unshaded-cooled conditions, reaching 887,000 cells/ml, even outperforming indoor cultures.
- Tetraselmis spp. grew best indoors at 28.9°C, but outdoor cooling systems could make outdoor cultivation viable.
- Direct sunlight helped increase cell density, but temperature control was essential to avoid overheating.
- Shaded conditions slowed growth, proving that unfiltered sunlight is beneficial when temperatures are managed properly.
This means that outdoor microalgae farming in Seychelles is not only possible but can be highly productive, if cooling mechanisms are in place.
Challenges of Outdoor Microalgae Farming
While the findings are promising, some challenges need to be addressed:
⚠ Temperature fluctuations – Without cooling, high temperatures can reduce microalgae growth.
⚠ Contamination risks – Outdoor systems are more exposed to bacteria, dust, and predators.
⚠ Unpredictable weather – Unexpected storms or prolonged cloudy days can impact light availability.
Future research aims to optimize these conditions, ensuring reliable and consistent production year-round.
A Sustainable Future
Outdoor microalgae farming in Seychelles has great potential, but success depends on managing light and temperature effectively. With the right strategies, it could become a game-changer for sustainable aquaculture, benefiting both the environment and local seafood production.
References
Maria Rose, Shamira Payet, Clémentine Violette, Danilla Adonis, Aubrey Lesperance, Bas de Vos. Investigating the feasibility and conditions for outdoor microalgae cultivation in Seychelles. Under review.