## 4 Biomass Availability for MAA Production  
The potential application of algae as a source of commercial bioactive compounds requires high biomass availability (Figure 4). The global production of macroalgae has tripled during the past 20 years, reaching 32.4 million tons per year. The most cultivated red algae in the world are _Eucheuma_ spp., _Gracilaria_ spp. (for phycocolloid extraction), and _Porphyna_ spp. (for human consumption), cultured mainly in China and Indonesia [78; 79]. Algae can be cultured in combination with fish and other aquatic organisms, under integrated multitrophic aquaculture (IMTA) systems, in which the inorganic nutrients (mainly nitrogen and phosphorous) from the fish pond effluents can be used for algae to grow and produce high-value biocompounds.  
High production of MAAs has been reported in algae grown in IMTA using fishspond effluents [49; 65; 80; 81]. _A. vermiculophyllum_ and _G. cornea_ were grown under different concentrations of nutrients obtained from fishspond effluents and high concentration of nitrogenous compounds, such as chlorophyll and phycobiloproteins, was observed. The highest yield of MAAs was obtained when _G. cornea_ was grown in fishspond effluents under natural light (sunlight) [81]. Piego-Cortes et al. [65] cultivated _Rhodymenia pseudopalmuta_ under high concentrations of ammonium (around 78.2 to 99.5 uM) using fishspond effluent in IMTA cultivation. The MAA content was five-fold higher compared to wild populations (grown in the natural environment under concentrations around 0.17 uM ammonium). Based on the data obtained, the authors presented an estimation of production for 100 m\({}^{2}\) of surface, totaling 941 g DW in 100 m\({}^{-2}\) d\({}^{-1}\) of biomass and 1167 mg of MAAs (yield of 1.24 mg MAAs g\({}^{-1}\) DW). In another study, _A. vermiculophyllum_ was grown for one year in tanks under natural light and addition of fishspond effluents. The MAA content varied seasonally; the highest values were observed in April (about 3.13 mg g\({}^{-1}\) DW). According to the results of this study, a total amount of 71.33 g MAA year\({}^{-1}\) could be produced in 100 m\({}^{2}\)[49].  
Figure 4: Scheme of the most important source of biomass for MAA production.  
Alternatively, algae biomass can be obtained from very productive coastal areas, e.g., algae from nutrient-enriched areas due to upwellings, as reported in Brazilian or Southern Iberian Peninsula coasts [35; 47]. Haroun et al. [82] also reviewed the potential biotechnological use of Macaroneian seaweeds, either wild-collected or cultivated. In this way, algal blooms and invasive species can be a natural source of MAAs. Some authors studied the possible use of these species as source of bioactive compounds, such as _A. armata_, _Sargasum muticum_, _Caulerpa cylindracaea_, _A. vermiculophyllum_, or _Grateulopia turuturu_[83; 84; 85; 86; 87]. The utilization of these species presents two opportunities: (1) high availability of biomass and (2) mitigation of their negative effects, through biomass collection, contributing to ecosystem restoration and sustainability. In relation to red algae, Pinteus et al. [85] reviewed different bioactivities of _A. armata_ for possible applications, including MAAs, and Felix et al. [86] analyzed the extraction of UV-absorbing and antioxidant compounds from _G. turuturu_. Recently, an extensive guide was published on the biotechnological uses of _Sargassum_ spp. accumulated biomass in the Caribbean coast [88].