Imagine a system where fish waste is turned into valuable fertilizer, and a delicious, nutritious plant thrives on it! This innovative approach is becoming a reality thanks to research on a fascinating plant called “Sea Asparagus” Salicornia ramosissima.
A study by scientists from IFAPA – El Toruño and the University of Seville aimed to implement an IMTA system with production of Senegalese sole (Solea senegalensis) and European seabass (Dicentrarchus labrax) in recirculating aquaculture systems (RAS), and hydroponically cultivated Salicornia ramosissima for the valorization of RAS effluent, promoting sustainable culture of local products in a circular blue economy model.
The scientific study explored the concept using Integrated Multi-Trophic Aquaculture (IMTA). In this system, wastewater from a recirculating aquaculture system (RAS) was converted into nutrient source for Salicornia ramosissima cultivated in two different hydroponic systems: Nutrient Film Technique (NFT) and Deep Water Culture (DWC).
The importance of halophytes
Halophytes have been used as food and inputs for pharmaceutical applications, and their cultivation has been promoted in recent decades.
These plant species have high contents of proteins, polyunsaturated n-3 and n-6 fatty acids, minerals, vitamins, and polyphenolic compounds associated with antioxidant activity and health benefits.
Salicornia ramosissima, also known as “sea asparagus,” is a halophyte, making it a perfect candidate for a new type of aquaculture system called Integrated Multi-Trophic Aquaculture (IMTA) that can be integrated with the production of marine fish in Recirculating Aquaculture Systems (RAS).
Salicornia is grown hydroponically, meaning it thrives without soil, using nutrient-rich effluent from fish rearing tanks as fertilizer.
Double victory: cleaning and growing
The research highlights two key benefits of this innovative system:
- Nutrient removal power: Salicornia acts as a natural filter, removing a significant portion of nutrients from fish wastewater. This reduces pollution and helps maintain a healthy environment for fish. The study found impressive removal rates:
Nitrate (NO3-): Up to 82.8% in DWC, 68.6% in NFT
Phosphate (PO43-): Up to 72.6% in DWC, 82.9% in NFT
Nitrite (NO2-): Up to 63.6% in DWC, 56.4% in NFT
Ammonium (NH4+): Up to 89.2% in DWC, an astonishing 94.1% in NFT
- Biomass bonanza: Salicornia thrives in this nutrient-rich environment and yields high returns. The Deep Water Culture (DWC) cultivation system proved to be particularly effective, with yields reaching a staggering 320 grams per square meter per day.
“We have obtained up to 320 grams of Salicornia ramosissima per square meter per day, which is equivalent to a cup of milk, and almost 10 kilograms per month for each tank of this size. Translated into economic value, it could assist in waste management,” says Marta Castilla.
Nutritional powerhouse emerges
Beyond its waste cleaning capacity, Salicornia itself holds exciting potential. The study analyzed the lipid profile of the plant, revealing a hidden treasure trove of essential fatty acids, including highly beneficial polyunsaturated fatty acids (PUFAs). PUFAs are crucial for human health and play a role in heart health and brain function.
Researchers also analyzed the lipid profile of Salicornia cultivated in the DWC system. They found a total lipid content ranging from 2.99% to 3.83%.
The fatty acid profile was particularly interesting. Polyunsaturated fatty acids, known for their health benefits, dominated, with alpha-linolenic acid (41%) and linoleic acid (24%) leading the way. Saturated and monounsaturated fatty acids were also present in smaller amounts.
“While plants in the first tank are well-fed, those in the last one have to activate biological mechanisms to supplement the lack of nutrients, and this causes certain beneficial compounds to be present in the plants at the end of the process in greater or lesser proportion. For example, plants subjected to nutritional stress present more Omega 3 or more glycolipids, related to antioxidant, antitumor, or anti-inflammatory activity,” explains Marta Castilla.
A sustainable future for aquaculture
This research paves the way for a more sustainable and resilient future for aquaculture. IMTA with Salicornia offers a compelling solution:
- Reduced environmental impact: IMTA helps minimize pollution in surrounding ecosystems by efficiently removing nutrients from wastewater.
- Resource optimization: Waste is transformed into a valuable resource, promoting a closed-loop system with minimal waste.
- Economic opportunities: The production of Salicornia, rich in nutrients and potentially valuable for human consumption or the pharmaceutical industry, creates new economic opportunities for aquaculture operations.
Conclusion
Research on the integration of Salicornia plants into recirculating systems for marine fish farming is a ray of hope for a more sustainable and productive future for aquaculture. By harnessing the power of nature, we can create systems that benefit both the environment and our health, while fostering economic growth.
The next step for researchers in the Sustainable Aquaculture group at IFAPA focuses on cultivating Salicornia with effluents from different aquaculture production systems. Depending on the type of fish farm, effluents may be more or less rich in nitrates or ammonia (another source of nitrogen, toxic to fish). The experts want to check if the cultivation of Salicornia ramosissima can adapt to all types of land-based fish farms, based on those currently present in the Bay of Cádiz. On the other hand, they are also studying the possibility of extending the life cycle of this plant or delaying its flowering to increase its productivity and allow farms to harvest for a longer part of the year.
The study has been funded by the Ministry of Universities, Research and Innovation and the Ministry of Science, Innovation and Universities under the Next Generation EU program. Additionally, it has received support from the European Maritime, Fisheries and Aquaculture Fund (EMFF) under the project ‘Eco-intensification of aquaculture through innovative technologies’.
Contact
M. Castilla-Gavilán
Laboratorio de Biología Marina, Departamento de Zoología, Facultad de Biología, Universidad de Sevilla, Avda. Reina Mercedes 6, Sevilla, Spain.
mcasgavilan@gmail.com
mcastilla1@us.es
Reference (open access)
Castilla-Gavilán, M., Muñoz-Martínez, M., Zuasti, E., Canoura-Baldonado, J., Mondoñedo, R., & Hachero-Cruzado, I. (2024). Yield, nutrients uptake and lipid profile of the halophyte Salicornia ramosissima cultivated in two different integrated multi-trophic aquaculture systems (IMTA). Aquaculture, 583, 740547. https://doi.org/10.1016/j.aquaculture.2024.740547
Note: Prepared based on information from the Descubre Foundation and the scientific article.
