Integrated multi-trophic aquaculture (IMTA) offers a promising approach to sustainable aquaculture by producing multiple products and improving water quality. A BARD-funded study led by Dr. Kevan Main from Mote Marine Laboratory & Aquarium in partnership with Dr. Lior Guttman from Israel Oceanographic and Limnological Research (ILOR) investigated the complex periphyton communities within IMTA systems, revealing insights that could optimize system design and enhance benefits.
Periphyton, the diverse mix of microorganisms growing on underwater surfaces, plays a crucial role in aquatic ecosystems. It serves as a vital food source for various organisms, including invertebrates, tadpoles, and some fish. Furthermore, periphyton can absorb contaminants, effectively removing them from the water column and limiting their spread in the environment. Its sensitivity to pollutants also makes it a valuable indicator of water quality, with changes in the periphyton community reflecting broader environmental impacts. Periphyton has even been used extensively in research, such as pollution-induced community tolerance studies.
This research focused on how the presence of halophytes and different system designs influence the structure of these periphyton communities within IMTA systems. Beyond its general ecological importance, controlling periphyton composition in aquaculture offers exciting possibilities. Manipulating the periphyton community could optimize nutrient cycling within the system, potentially reducing off-flavors in fish production. Additionally, the periphyton itself could become a valuable secondary product, harvested and used as feed for other animals.
The study compared periphyton communities in three different recirculating IMTA systems, some with halophytes and others without. Interestingly, the system design and/or season had a greater impact on the periphyton community structure than the presence of halophytes. Systems continuously fed with fish effluent were dominated by arthropods, fungi, and Pseudomonadota. In contrast, systems initially seeded with fish effluent and then maintained with sterile seawater showed a predominance of diatoms, roundworms, Bacteroidota, and Cyanobacteria.
While the study identified the presence of taxa associated with off-flavor production, fish disease, and nitrogen cycling, it’s important to note that these were only predicted functions, not confirmed.
This research highlights the significant influence of various factors on periphyton community structure. By carefully adjusting these factors, it may be possible to manipulate the microbial composition of periphyton in ways that maximize its benefits.
This could lead to increased nutrient content, enhanced nitrogen cycling, improved oxygen supplementation, and potentially the development of periphyton as a valuable feed source within IMTA systems, further boosting their efficiency and sustainability.
Given the study’s focus on nutrient cycling and oxygen supplementation, do you foresee any opportunities to scale up this research to larger or commercial aquaculture operations? If so, what are the biggest challenges to scaling up?
Dr. Main: “Yes. Research should continue at larger scale, potentially in collaboration with commercial aquaculture operations. The biggest challenge to scale up seems to be minimizing the surface area of the biofilter and improving the efficiency in periodic harvesting methods. This may be achieved by increasing the provided area of the plastic net substrate for periphyton (e.g., through enlarging the effective depth for growing periphyton in the biofilter) and by reducing the frequency and time required to harvest periphyton. “
What are the potential practical applications of this study for aquaculture operators? How could these insights help in optimizing system design for better water quality, increased efficiency, or reduced costs?
Dr. Main and Rr. Guttman: “The developed biofilter is simple to operate and can be applied, at a low cost, to improve water quality in various aquaculture operations. The periphyton requires only plastic nets substrate to grow on, nutrients from the fish culture, and light. The combination of periphyton with other biofilters (i.e., halophytes) can significantly improve the performance of recirculating aquaculture systems. The insights from the current research assist end users in applying the technology in their farm, according to their knowledge of the chemical content of N and P in the discharged effluent.”
Read the recent publication: https://www.sciencedirect.com/science/article/pii/S0044848625000961?via%3Dihub
