WWW.WAS.ORG • WORLD AQUACULTURE • SEPTEMBER 2024 45 The large-scale production of macroalgae can be considered low-cost and easy to manage, as it does not require investments in feed, electricity, large amounts of land, or fertilizers (Chopin et al. 2001)especially where activities are highly geographically concentrated or located in suboptimal sites whose assimilative capacity is poorly understood and, consequently, prone to being exceeded. One of the main environmental issues is the direct discharge of significant nutrient loads into coastal waters from openwater systems and with the effluents from land-based systems. In its search for best management practices, the aquaculture industry should develop innovative and responsible practices that optimize its efficiency and create diversification, while ensuring the remediation of the consequences of its activities to maintain the health of coastal waters. To avoid pronounced shifts in coastal processes, conversion, not dilution, is a common-sense solution, used for centuries in Asian countries. By integrating fed aquaculture (finfish, shrimp. Macroalgae are often used as bioremediators when integrated with the cultivation of other aquatic species. This integration helps minimize the accumulation of inorganic and organic compounds in semi-intensive and intensive fish and shrimp production systems, where only the target species are fed (Troell et al. 2009)”ISSN”:”00448486”,”abst ract”:”The marine aquaculture sector is growing rapidly. Offshore aquaculture installations have been drawing increasing attention from researchers, industry and policy makers as a promising opportunity for large-scale expansion of the aquaculture industry. Simultaneously, there has also been increased interest in both land-based and nearshore aquaculture systems which combine fed aquaculture species (e.g. finfish. The cultivation of species from different trophic levels in the same system is called Integrated Multitrophic Aquaculture (IMTA) (Chopin et al. 2012). In this system, the waste produced by the main species can be reused by organic and inorganic consumer species to form new biomass with added economic value. The major challenges in adopting integrated systems include difficulties faced by producers regarding legislation, obtaining green certification, lack of governmental incentives, and the need for skilled labor for management practices (Khanjani et al. 2022)and its prominent role has been proven in supplying food for the growing world population. The expected growth of aquaculture requires the development of responsible and sustainable approaches, technologies, culture systems, and practices. The integrated multitrophic aquaculture (IMTA. The inclusion of different species in production can lead to issues such as overpopulation, reduced oxygen levels due to increased biomass, and the emergence of diseases, heightening the risk of system collapse if one species is affected. Conversely, conventional systems are associated with low sustainability due to the release of effluents with high organic loads and nutrients, leading to eutrophication problems in water sources (Queiroz et al. 2020). Therefore, adopting production systems that reuse waste is necessary for sustainable and productive aquaculture practices. The use of integrated systems in intensive production makes possible a more effective use of waste alongside high stocking densities. Biofloc technology (BFT) represents an intensive system with minimal water exchange, based on maintaining water quality through the growth of a microbial community (Wasielesky et al. 2013). The use of inorganic or organic fertilizers favors the growth of chemoautotrophic and heterotrophic bacteria in the system, which use the available ammonia to form bacterial biomass or oxidize it to less toxic nitrogen compounds (Ferreira et al. 2021). In addition to the benefits of managing water quality and biosafety parameters, the biofloc system can also be a supplementary food source for cultivated organisms, as bacterial biomass contains proteins, lipids, vitamins, and micronutrients (Khanjani et al. 2023). However, due to minimal water exchange, the increase in ammonia levels from animal excretion and its transformation to nitrite and then to nitrate through bacterial oxidation leads to accumulations in the BFT system (Brandão et al. 2021). This nutrient availability is advantageous for the inclusion of macroalgae in the system. As primary producer species, macroalgae absorb nutrients, benefiting from nitrogenous compounds and carbon dissolved in the water for their growth, thus helping to treat the water by forming biomass with added economic value (García-Poza et al. 2020). Nevertheless, the distinct characteristics of the biofloc system present challenges for the inclusion of macroalgae, demanding adjustments in production management without harming the system. For example, the high production and accumulation of suspended solids pose a challenge because of the reduction in light levels and the deposition of flocs on the photosynthesizing lamellae. Therefore, studies focusing on the effect of organic load on macroalgae biomass production and viable management methods are crucial for the development of efficient integrated systems. Aiming to determine the viability of macroalgae production in an integrated system with biofloc, several studies have been conducted to evaluate their growth, nutrient absorption, and nutritional quality in BFT systems integrated with fish and shrimp. Progress in the production of the macroalga Ulva spp. in an Integrated Multitrophic Aquaculture with biofloc System Andrezza Carvalho, Alessandro P. Cardozo, Rafaela Crespo, Marcelo Tesser, Geraldo Foes, Dariano Krummenauer, Gamze Turan, Wilson Wasielesky Jr. and Luis H. Poersch (CONTINUED ON PAGE 46)
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