Potential of innovative marine aquaculture techniques to close nutrient cycles

Aquaculture is an established technique for producing marine species. However, it creates large amounts of nutrient-rich waste. Therefore, it is worth examining the methods available to use these nutrients and close the nutrient cycle. This review covers research activities of different saline water methods for food production. These are Integrated Multi-Trophic Aquaculture (IMTA), Biofloc Technology (BFT) and marine aquaponics. IMTA combines on- and offshore aquaculture with macroalgae and filter feeder production. Commercial implementations have been achieved but are not widely used. Especially shrimp are suitable for cultivation in saline BFT systems. Few commercial deployments exist. There is a well-established market for the products of IMTA and BFT systems. Marine aquaponics is increasingly being tested as part of an expansion of Recirculating Aquaculture Systems (RAS) and BFT systems, but commercial implementations are not known. Moreover, there is no established market for the resulting salt-tolerant plants (halophytes). Market prices and popularity were evaluated to assess the economic potential of the different plant and aquaculture species farmed with IMTA, BFT and marine aquaponics. There are established markets for well-known products, but therefore the competition is greater. Niche products are offered occasionally, but often achieve top prices. Closing nutrient cycles and increasing saline water usage for food production as well as high product diversity are necessary to mitigate the increasing pressure on freshwater resources and to be able to feed the growing world population. Therefore, IMTA, BFT and marine aquaponics are promising techniques for reducing pressure on freshwater resources and improving food supply.