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Beach-cast marine algae are a potential biomass for several biofunctional products and occur in large volumes in some coastal regions due to natural current processes or drifting algae like pelagic Sargassum. Antioxidant activity and chemical composition of methanolic and aqueous extracts from fifteen beach-cast marine algae from the Brazilian Coast were evaluated. In general, the highest antioxidant activities were found in extracts from brown macroalgae followed by the extracts of red algae, and the lowest activities were detected in the green beach-cast algae. The concentrations of phenolic compounds and carbohydrates exhibited a positive correlation with the antioxidant activities of the tested extracts. To the best of our knowledge, this is one of the few worldwide studies concerning beach-cast seaweeds and antioxidant activity and related antioxidant metabolites. This study suggests that these algae are potential sources for obtaining extracts with antioxidant properties, rich in phenolic compounds and sulfated carbohydrates. Beach-cast macroalgae are unused biomass and the beneficial utilization of this biomass for prospection of natural products and functional foods is suggested.

Seaweeds are a source of antioxidants and pigments, which can be used as functional ingredients for food, cosmetic, pharmaceutical, and industrial applications. As fresh seaweed has a large amount of water, it usually goes through a drying process in order to be commercialized, which facilitates transportation and storage and also increases shelf time. However, the drying procedures can change the chemical composition and antioxidant properties of seaweeds. Thus, the aim of this study was to evaluate the antioxidant properties and pigment and protein content of four Brazilian macroalgae (Gracilariopsis tenuifrons, Pterocladiella capillacea, Sargassum stenophyllum, and Ulva fasciata) suitable for use as functional bioproducts after processing with three different drying procedures (freeze-drying, oven-drying and silica-drying), using a fresh frozen treatment as control. Among the studied species, S. stenophyllum presented the highest antioxidant activity. For this species, freeze-drying was the procedure with the highest activity in the Folin-Ciocalteu and metal chelating assays, while for the ABTS, DPPH, and FRAP assays, no significant differences were observed between freeze-drying and silica-drying. Freeze-drying also showed low reduction of photosynthetic pigments in G. tenuifrons, P. capillacea, and U. fasciata and was the method that best-preserved protein content in the four species. In general, the antioxidant potential and pigment and protein content for the studied algae decreased in the following order: fresh frozen (control) > freeze-dried > silica-dried > oven-dried. Freeze-drying was the procedure that presented the lowest alteration in functional properties, as the low temperature prevents the degradation of heat-sensitive compounds. In addition, freeze-drying is a vacuum process and the absence of oxygen prevents oxidation reactions of functional ingredients.

In Brazil species of Gracilaria play a social and economic role in some poor communities of the northeastern coast. Considering that these algae are typically consumed after depigmentation and drying, little is known about the chemical composition and nutritional value after processing. In the present study dried and depigmented samples of Gracilaria birdiae (GB), Gracilaria caudata (GC), Gracilaria domingensis (GD), and a commercially available sample of G. birdiae (C-GB), provided by a local community, were studied as a source of valuable compounds and as nutritional supplements. In nutritional terms, the dietary fiber and mineral contents of the studied algae were higher than those of the traditional foods in the standard Brazilian diet. The results suggest that these algae have functional properties and consequently may be used as a source of nutraceutical. GB and GC showed a high antioxidant potential, similar to that of some staple foods (e.g., cereals and legumes), but lower than that of rich-antioxidant foods (e.g., berries and nuts). The polysaccharides from both G. birdiae samples (GB and C-GB) showed a low sulfation degree and higher yields, suggesting that they are a good source of agar. GB was also rich in mycosporine-like amino acids (MAAs), mainly porphyra-334. In contrast, C-GB contained the lowest values of MAAs and antioxidants. The reduction in these compounds may compromise the use of C-GB for other purposes such as cosmetic production. However, the sample of C-GB showed the highest potential as a source of dietary fiber and agar. In general, the analyzed species are alternatives to traditional foods and a source of valuable compounds.

Periphyton has been recognized as an important element in aquatic food chains due to its role in primary production. More recently, it has been used as bioindicator of contamination in reservoirs since biofilm analysis can support in understanding the impacts of bottom-up contaminants to the reservoirs. Copper (Cu) is one of these pollutants which has been used as an algicide; it accumulates in the sediment and can be released to the water column, causing harm to various aquatic organisms, including the periphytic biofilm. In this work periphyton cultivated in the laboratory was exposed to copper, using concentrations from 0.013 to 0.15 mg Cu L−1 over 15 days under controlled conditions (temperature, light, and oxygenation). Different physical-chemical and ecological parameters were measured in order to describe the effects of Cu on the community, which included alterations in ash-free dry mass and chlorophyll concentration, as well as an earlier photosynthetically light saturation point. The results reflected different ecological behavior with modifications in the community composition and greater cyanobacteria dominance like abundance of species with mucilage as the Cu concentration increased. Furthermore, some species of diatoms were not found when the water was contaminated with Cu. This disturbance in the ecological composition of periphyton affects significantly the food chain due to the unpalatability of tolerant species and/or the bioaccumulation of Cu which may be transferred to other organisms potentially causing toxicity to primary consumers.

High levels of irradiance may affect the growth and development of photosynthetic organisms, changing concentrations of carotenoids and chlorophylls. These changes may indicate different photoprotection strategies. In this study, gametophytic apical portions of Gracilariopsis tenuifrons were cultivated under controlled laboratory conditions for 1 week, at different light irradiances: 60 (control), 600, and 1,000 μmol photons m−2 s−1. Growth rate, amount, and composition of pigments were analyzed daily. Color of seaweeds exposed to 600 and 1000 μmol photons m−2 s−1 varied along the days, from red to yellowish, suggesting a decrease in vital processes as photosynthesis and growth. However, no decrease in biomass was observed. Actually, there was an increase at growth rates for the algae kept under higher light intensities. The main registered pigments were chlorophyll a, β-carotene, and zeaxanthin. β-carotene and chlorophyll a levels were lower in algae exposed to high light intensity. In treatment exposed to 600 μmol photons m−2 s−1, this reduction was 42 and 35 %, respectively, while in those exposed to 1000 μmol photons m−2 s−1 the values were 55 and 50 % lower than the control. The lower levels of these pigments may be associated with the reduction in energy harvesting by the photosynthetic complexes-antennae, in an effort to dissipate the high excitation impinged over the photosynthesis system as a whole. For zeaxanthin levels, a 20 % increase was observed in the beginning of the experiment, which was followed by a drop to the initial levels, suggesting the role of this pigment in this alga’s photoprotection process.

The red macroalga Porphyra C. Agardh is one of the most ecologically successful genera that lives in the upper intertidal zone. Biochemical, physiological, and morphological acclimation strategies allow their growth and distribution as well as a quick recuperation between tidal regimens. Studies of Porphyra are poorly developed in Chile, and management and exploitation proposals need to be supported by biological and ecophysiological approaches. This study evaluated seasonal and latitudinal physiological performances of Porphyra spp. via maximum quantum yield (F v / F m), pigments, proteins, phenolic compounds, and antioxidant activity in order to describe how algae can acclimate to their environment and to provide insights to their management and use. Sampling was done at three costal sites in Chile between 25°S and 34°S between winters 2010 and 2011. A total of four different morphotypes were identified (one in the north, one in the center, and two in the south locations) and evaluated separately. Results showed seasonal and latitudinal patterns for all ecophysiological variables studied, with a general tendency of decrease in F v / F m, pigments, and soluble proteins during spring–summer seasons accompanied by an increase in the antioxidant capacity. Latitudinal differences were observed with a tendency of higher values for ecophysiological traits in central and southern morphotypes. Phenology patterns were different between an annual population in the north location and a perennial one for central-south populations. The taxonomic clarity should be evaluated in order to better understand if there exists intraspecific (dependent on morphology) or interspecific variation.

Nitrate is one of the most important stimuli in nitrate reductase (NR) induction, while ammonium is usually an inhibitor. We evaluated the influence of nitrate, ammonium or urea as nitrogen sources on NR activity of the agarophyte Gracilaria chilensis. The addition of nitrate rapidly (2 min) induced NR activity, suggesting a fast post-translational regulation. In contrast, nitrate addition to starved algae stimulated rapid nitrate uptake without a concomitant induction of NR activity. These results show that in the absence of nitrate, NR activity is negatively affected, while the nitrate uptake system is active and ready to operate as soon as nitrate is available in the external medium, indicating that nitrate uptake and assimilation are differentially regulated. The addition of ammonium or urea as nitrogen sources stimulated NR activity after 24 h, different from that observed for other algae. However, a decrease in NR activity was observed after the third day under ammonium or urea. During the dark phase, G. chilensis NR activity was low when compared to the light phase. A light pulse of 15 min during the dark phase induced NR activity 1.5-fold suggesting also fast post-translational regulation. Nitrate reductase regulation by phosphorylation and dephosphorylation, and by protein synthesis and degradation, were evaluated using inhibitors. The results obtained for G. chilensis show a post-translational regulation as a rapid response mechanism by phosphorylation and dephosphorylation, and a slower mechanism by regulation of RNA synthesis coupled to de novo NR protein synthesis.