## 2 Screening of MAAs  
Several authors studied the presence/concentration of MAAs in different red algae species and its geographical or seasonal variations. Navarro et al. [2] summarized in a book chapter the MAA content of different species from different geographic locations: Huovinen et al. [42] studied the MAA concentration in macroalgae from southern Chile, obtaining the highest content in _Pyropia columbina_ (previously, _Porphyra columbina_) (7.2-10.6 mg g\({}^{-1}\) DW), followed by _Bostrychia_ sp. (4.7 mg g\({}^{-1}\) DW), _Gelidium_ sp. (2.2-6.8 mg g\({}^{-1}\) DW), and _Mazzella laminaroides_ (2.1-4.8 mg g\({}^{-1}\) DW). Briani et al. [43] studied macroalgae from the Brazilian coast and also obtained the highest MAA content in the genus _Porphyra (Pyropia acanthophora_, 5.2-6.6 mg g\({}^{-1}\) DW), followed by _Laurencia carabica_ (2.2-3.6 mg g\({}^{-1}\) DW). Karsten et al. [44] studied different species found in tropical mangroves and observed a high content in species from the genus _Bostrychia_ (3-12 mg g\({}^{-1}\) DW) and _Sticusibmonia_ (6 mg g\({}^{-1}\) DW). More recently, Lalezerie et al. [45] analyzed the photoprotective compounds in several red algae species from Britanny (France), obtaining the highest concentrations in _Bostrychia scorpioides, Porphyra dioica, Agarolyton vermiculophyllum_ (as _Gracilaria vermiculophyllum_) and _Vertebra lanosa_. The MAA content of species from southern Spain was also analyzed, obtaining high values in _Porphyra umbilicalis_ (2.6-10 mg g\({}^{-1}\) DW) and _Bangia atropurpurea_ (5 mg g\({}^{-1}\) DW), followed by _Feldmanophycus russiae, Chondarcanthus acicularis, Gelidium_ sp. and _Osmundea pinmatifida_ (1.5-3 mg g\({}^{-1}\) DW) [46; 47; 48]. Seasonal variation of MAAs has been reported in red macroalgae. _A. vermiculophyllum_ from \"Ria de Aveiro\" (Portugal) showed a high MAA content in spring, due to the nitrogen (N)-enriched waters [49]. Guiheneuf et al. [50] observed an increase in the MAA content of different red algae (_Palmaria palmata, Chondrus crispus_, and _P. dioica_) in spring, induced by the increasing daily light and irradiance. Lalezerie et al. [51] also observed a high seasonal variability in _P. palmata_, with a higher content of MAAs in April and May, due to the light increase. In addition, short-term variation has been also reported (hourly and daily variations) [52; 53; 54]. For example, under days with ozone depletions in Patagonian, a rapid increase in myc-glycine was detected in _P. columbina_[53]. Korbee-Peinado [55] analyzed species from different orders and observed some patterns in the MAA content: the highest values were observed in Bangiales (_Porphyra_ spp. and _Bangia_ sp. ), followed by Bonnemaisonales (_Asparagopsis_ spp.) and Gelidialies (_Gelidium_ sp. ), whereas the lowest content was observed in Corallinales. Rhodophyta algae can be classified into three groups according to the concentration of MAAs: (1) species without the capacity to synthetize MAAs or with very low content of MAAs (<1 mg g\({}^{-1}\) DW) (e.g., Corallinales or Plocamiales); (2) species with low content of MAAs (1-2 mg g\({}^{-1}\) DW) (e.g., Rhodymeniales or Ceramiales); and (3) species with a high content of MAAs (>2 mg g\({}^{-1}\) DW) (e.g., Bangiales, Gelidiales, Gracilariales) [56; 21]. In most cases, the quantity and quality of MAAs can vary depending on the environmental factors [57; 58; 59; 60]. Within these orders, some species stand out, such as _Porphyra_ spp., _B. atropurpurea_ (Bangiales), and _Gelidium pusillum_ (Gelidiales) [55]. Some authors published databases of MAAs. Sinha et al. [20] summarized the MAA data obtained in fungi, cyanobacteria, phytoplankton, macroalgae, and animals. More recently, Sun et al. [21] collected the MAA values observed in marine macroalgae over the past 30 years (1990-2019), and confirmed that 572 species of marine macroalgae contained MAAs (45 species of Chlorophyta, 41 species of Phaeophyceae, and 486 species of Rhodophyta).