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Microalgae have shown a great potential as a source of bioactive compounds, such lipidic compounds as fatty acids and carotenoids, with recognized benefit for human health. Their synthesis is directly affected by culturing conditions, but, as photosynthetic organisms, microalgae are greatly influenced by light, particularly light quality and irradiance, responsible for growth regulation and activation of biochemical pathways. Therefore, the aim of this work was to maximize biomass and high added-value compound productivity by Scenedesmus obliquus M2-1, using different light irradiances of two previously selected light sources for the production of antioxidant compounds: monochromatic red light (R) and a mixture of 40% of blue and 60% of red light (BR). Four irradiances (50, 100, 150, and 200 μmolphotons m−2 s−1) were accordingly evaluated for both light sources, upon productivity of biomass, fatty acids, carotenoids, and total antioxidant compounds. Changes in light quality and irradiance influenced these aforementioned productivities. Optimal condition for biomass productivity was 150 μmolphotons m−2 s−1, regardless light quality, for both sources. On the other hand, when the production targets carotenoids, polyunsaturated fatty acids, and/or total antioxidant capacity, the optimal condition was found to be at 200 μmolphotons m−2 s−1 under BR light.

Seaweeds such as Ascophyllum nodosum are essential components of coastal ecosystems, being frequently relevant both ecologically and economically. The current increasing demand for seaweed biomass must be compatible with sustainable management practices of these resources. This study aims to provide supporting evidence for the establishment of management plans for “edge populations” (at their distributional limits) with commercial interest using, as a model, the southernmost population of A. nodosum in Europe (which occurs on the northern coast of Portugal). In this study, standing stock, biomass renewal and seasonal and spatial patterns of occurrence of this Ascophyllum unexploited population were assessed in order to evaluate harvesting potential. A total of 16 patchily distributed and variable sized beds, covering an area of 112,126 m2, were delimited during late summer/autumn of 2016, providing a standing stock of 30,952.12 kgdw. The abundance of these populations was stable over time (2005–2010), although small-scale spatial variations and changes in individual biomass due to seasonal loss could be identified. However, the potential biomass renewal as estimated for this whole population was 290.3 kgdw year−1, representing only 0.94% of the calculated standing stock. Based on these results, the importance of considering the population’s renewal potential is highlighted in addition to individual phenotypic traits when managing harvesting. Specifically, given the vulnerability and ecological relevance of the studied population, the recommendation herein is to avoid harvesting of this species at its southernmost location in Europe.

Cyanobacteria-based pigments, such as carotenoids and phycobiliproteins, have emerged in the last few years as products with great economical interest. However, only the production of a few strains has been optimized for large-scale productions. As photosynthetic components, pigments have their synthesis modulated by abiotic factors, such as pH, temperature and salinity, which can lead to a huge impact on cyanobacteria production. This work aimed the optimization of biomass and pigments production by Cyanobium sp. LEGE 06113, using a factorial Box-Behnken design for three abiotic factors—temperature (20–30 °C), pH (6.0–9.0) and salinity (NaCl, 10–30 g L−1). Biomass, photosynthetic activity, carotenoid and phycobiliprotein productivity and antioxidant capacity of acetonic and aqueous extracts were measured over time and plotted into quadratic models. Results revealed that temperature and pH had a more significant impact than salinity on Cyanobium sp. metabolism and it was possible to determine a significant quadratic model for all evaluated parameters. According to the factorial modelling, the optimal condition for biomass, carotenoids and phycobiliprotein productivity was obtained at 20 °C, pH 9.0 and 10 g L−1 of NaCl, as subsequently confirmed in experimental trials, with an observed productivity of 127.12 ± 1.30 mgDW Lculture−1 day−1 for biomass; 2.04 ± 0.51 mgcarot Lculture−1 day−1 for total carotenoids; and 4.14 ± 0.71 mgphyco Lculture−1 day−1 for total phycobiliproteins. This work was co-funded by the national founding from FCT (UIDB/04423/2020 and UIDP/04423/2020); by the Atlantic Interreg Projects, Enhance MicroAlgae, high added value industrial opportunities for microalgae in the Atlantic Area (EAPA_338/2016), and by the BLUEHUMAN, BLUE biotechnology as a road for innovation on human’s health aiming smart growth in Atlantic Area (EAPA_151/2016).

Dietary inclusion of IMTA-cultivated Gracilaria vermiculophylla was evaluated in rainbow trout. Growth and feed efficiency were determined in fish fed 0 % (CTRL), 5 % (G5), and 10 % (G10) of the red seaweed for 91 days. Carotenoid concentration (skin and muscle), immunological parameters, and intestinal morphology were also evaluated. G10 group showed the lowest final body weight, with feed and protein efficiency ratios being significantly lower than the CTRL. Although protein intake was similar among groups, G10 diet induced the lowest protein retention and gain probably due to its smallest intestine diameter and lowest villi height. Fish fed G10 diet displayed higher carotenoid content in the skin (16.7 μg g−1) when compared with the CTRL group, but a lower concentration was registered in the flesh (0.23 μg g−1). Instrumental color showed that fillets were more luminous (L*), less yellowish (b*), and more reddish (a*) with seaweed inclusion and the lowest chrome intensity (C*) in the G10 group confirmed the lowest muscle carotenoid content in these fish. G5 diet enhanced the innate immune response of rainbow trout inducing the highest peroxidase, alternative complement (ACH50), and lysozyme activities. The inclusion of Gracilaria meal in diets for rainbow trout is possible up to 5 %, but a higher inclusion level impairs growth.

The potential of rearing the red seaweed Mastocarpus stellatus (Stackhouse) Guiry, a carrageenophyte, as a biofilter in a pilot-scale, integrated multi-trophic aquaculture (IMTA) system was investigated. From April to June, M. stellatus, collected from a population in the north of Portugal was cultivated in 1200-L tanks in two consecutive, 4-week experiments with nutrient-enriched waters derived from fish tanks. The stocking density of 3 kg m−2 provided the best yields, ranging from 29.6 g dw m−2 day−1 in April–May to 38.9 g dw m−2 day−1 in June. In the April–May period, a linear increase in the yields was found at higher densities. M. stellatus growth rates during April–May period did not diverge significantly between stocking densities and reached a mean relative growth rate of 3.09 ± 0.90 % day−1 in April–May and 4.02 ± 0.43 % day−1 in June at 3 kg m−2. In June, the increase in stocking density negatively affected the growth rates (3

Increasing levels of a mixture of Ulva spp. produced in an integrated multi-trophic aquaculture (IMTA) system were evaluated in Nile tilapia juveniles for partial replacement of dietary fish meal. A control diet (CTRL) was compared with three experimental diets containing 10 % (U10), 15 % (U15), and 20 % (U20) of Ulva spp. meal. Triplicate groups of fish (13 g initial body weight) were fed each diet for 63 days at 26 °C. Nutrient apparent digestibility coefficients and nitrogen retention efficiency did not vary significantly among diets. By the end of the trial, all groups of fish more than tripled their initial body weight. Specific growth rate and final body weight of U10 diet were similar to CTRL and significantly higher than U15 and U20 diets. Increasing Ulva dietary incorporation levels significantly increased feed conversion ratio (FCR), from 1.0 (CTRL) to 1.4 (U20). Fish fed with U10 diet had the highest protein efficiency ratio and nitrogen retention efficiency allowing this fish to growth and reach a final body weight similar to the CTRL group. Protein content was highest in fish fed with the CTRL diet, whereas the highest lipid content was observed in fish fed with U20 diet. The results show that the incorporation of IMTA-produced Ulva meal in Nile tilapia diets is possible up to 10 % without compromising growth performance, protein utilization, and protein retention of juveniles. The high capacity of Nile tilapia to digest all experimental diets suggests that Ulva meal is a practical partial replacement for fish meal in Nile tilapia diets.

Macroalgae drive the biodiversity and functioning of many shallow benthic ecosystems. Besides their key role in coastal ecosystems, they are rich sources of a wide variety of unique molecules with high impact in food science, pharmaceutical industry and public health. Carotenoids and chlorophylls present in three kelp species—Laminaria ochroleuca, Saccharina latissima and Saccorhiza polyschides—were determined by high-performance liquid chromatography coupled to a diode array detector. The effect of different harvesting times, depths and growth conditions (wild vs. aquaculture) on pigment qualitative and quantitative profiles was assessed. Stipes, blades and whole macroalgae were studied. In spite of the considerable variability observed amongst all samples, fucoxanthin was evidently the main carotenoid. Overall, the relative contents of carotenoids were significantly higher than those of chlorophylls. In addition, the cultivation of macroalgae in an integrated multi-trophic aquaculture system appears to increase pigment levels. Altogether, the results demonstrate the complexity of the influence of species-specific and environmental factors on pigment composition and reinforce that macroalgae cultivation systems may provide an interesting approach to optimize the production of some valuable metabolites. © 2016, Springer Science+Business Media Dordrecht. The authors thank Diogo Silva, Patrícia Oliveira and Tânia Pereira (CIIMAR/CIMAR) for assistance in the cultivation and collection of the algae material. This work received financial support from the National Funds (FCT/MEC, Fundação para a Ciência e Tecnologia/Ministério da Educação e Ciência) through projects UID/QUI/50006/2013 and UID/Multi/04423/2013, co-financed by the European Union (FEDER under the Partnership Agreement PT2020) and from the SeaweedStar/E*6027 (EUROSTARS) project. To all financing sources the authors are greatly indebted. Fátima Fernandes (SFRH/BPD/98732/2013), Mariana Barbosa (SFRH/BD/95861/2013) and Andreia P. Oliveira (SFRH/BPD/96819/2013) thank FCT/MEC for the grants. Isabel C. Azevedo (SEAWEEDTECH/BPD/2011/02) thanks SeaweedTech/ES466813 project (Norwegian Research Council) for the grant.

The present study evaluated the effects of the inclusion of three seaweeds, Gracilaria vermiculophylla (GRA), Porphyra dioica (POR), and Ulva spp. (ULV), as dietary ingredients for Nile tilapia (Oreochromis niloticus) juveniles, on the growth performance, body composition, and gut histology. Three experimental diets (GRA, POR, and ULV) were formulated to replace 10 % of whole diet by each of the three seaweeds. A control diet (CTRL) was used, without inclusion of any seaweed. Diets were fed to triplicate groups of 25 Nile tilapia juveniles, with an average body weight (ABW) of 12.1 g, in an 84-day trial. At the end of the trial, growth performance was significantly reduced (P