Low molecular weight carbohydrate patterns of mangrove macroalgae from different climatic niches under ocean acidification, warming and salinity variation.

Ocean acidification has increased due to the enhanced solubility of CO2 in seawater. Mangrove macroalgae in tropical and subtropical coastal regions can benefit from the higher availability of CO2 for photosynthesis and primary production. However, they can be negatively affected by the simultaneously occurring warming and increased salinity in estuaries. Thus, we analyzed the isolated effects of ocean acidification and the interactive effects of increased temperature and salinity on the low molecular weight carbohydrate (LMWC) contents of the mangrove red macroalgae Bostrychia montagnei and Bostrychia calliptera from Brazilian tropical and subtropical populations. Specimens from both climatic niches were tolerant to pH decreased by CO2 enrichment and enhanced their LMWC contents under increased availability of CO2. Specimens from both climatic niches also accumulated their dulcitol and sorbitol contents to cope with warming and salt stress. Nevertheless, temperature of 34 °C was lethal for tropical macroalgae, while 29 °C and 31 °C were lethal for subtropical B. calliptera under salinity of 35. Tropical and subtropical B. montagnei synthesized dulcitol (5-110 mmol kg-1 dry weight) and sorbitol (5-100 mmol kg-1 dry weight) as osmoregulatory, energy and thermal protection compounds, whereas tropical and subtropical B. calliptera synthesized mainly dulcitol (10-210 mmol kg-1 dry weight). Although digeneaside has an energy function in Bostrychia spp., it is not an osmolyte or thermal protection compound. Our data demonstrated that both tropical and subtropical Bostrychia spp. benefit from ocean acidification by CO2 enrichment, increasing their LMWC contents. However, warming and increased salinity in estuaries will be detrimental to them, even they producing protective metabolites. Multifactorial approaches are recommended to investigate whether negative effects of increased temperature and salinity nullify positive effects of ocean acidification on these Bostrychia species/populations.

Ocean warming and increased salinity threaten Bostrychia (Rhodophyta) species from genetically divergent populations.

Increased greenhouse gas concentrations in the Earth's atmosphere have resulted in global change, such as ocean warming and sea level rise. Increased salinity in estuaries is expected as a result of sea level rise and warming. Thus, we analysed the interactive effects of increased temperature and salinity on multiple physiological responses of Bostrychia montagnei and B. calliptera from two biogeographic provinces, Tropical Southwestern Atlantic (TSA) and Warm Temperate Southwestern Atlantic (WTSA). Macroalgae were cultured under three salinities (15, 25 and 35 PSU) and three temperatures: mean sea surface temperature (SST: 27 °C for TSA and 24 °C for WTSA), an RCP8.5 ocean warming scenario (SST + 5 °C), and a maximum temperature to test the algal upper thermal tolerance limits (RCP8.5 + 2 °C). Macroalgae from both localities decreased their growth under increased temperature and salinity. RCP8.5 + 2 °C was lethal for both macroalgae from TSA. RCP8.5 and RCP8.5 + 2 °C at 35 PSU were lethal for B. calliptera from WTSA, due to the interactive effects between increased temperature and salinity. Overall, increased salinity decreased the effective quantum yield and relative electron transport rate in algal photosynthesis. Our results demonstrated that the macroalgae synthesized proteins, carbohydrates (polysaccharides and low molecular weight carbohydrates), and antioxidants to tolerate detrimental temperatures and salinities. Our results also demonstrated that the macroalgae adjusted their pigment contents (phycobiliproteins, total carotenoids, and chlorophyll a) for efficient light-harvesting under thermal and saline stress. Our findings suggest that ocean warming and increased salinity in estuaries will be detrimental to B. montagnei and B. calliptera populations from both biogeographic provinces, especially to those from TSA that already live closer to their upper thermal tolerance limits.

Insights into agar and secondary metabolite pathways from the genome of the red alga Gracilaria domingensis (Rhodophyta, Gracilariales).

Gracilariales is a clade of florideophycean red macroalgae known for being the main source of agar. We present a de novo genome assembly and annotation of Gracilaria domingensis, an agarophyte alga with flattened thallus widely distributed along Central and South American Atlantic intertidal zones. In addition to structural analysis, an organizational comparison was done with other Rhodophyta genomes. The nuclear genome has 78 Mbp, with 11,437 predicted coding genes, 4,075 of which did not have hits in sequence databases. We also predicted 1,567 noncoding RNAs, distributed in 14 classes. The plastid and mitochondrion genome structures were also obtained. Genes related to agar synthesis were identified. Genes for type II galactose sulfurylases could not be found. Genes related to ascorbate synthesis were found. These results suggest an intricate connection of cell wall polysaccharide synthesis and the redox systems through the use of L-galactose in Rhodophyta. The genome of G. domingensis should be valuable to phycological and aquacultural research, as it is the first tropical and Western Atlantic red macroalgal genome to be sequenced.

Sulfated polysaccharide from the red algae Gelidiella acerosa: Anticoagulant, antiplatelet and antithrombotic effects.

A sulfated polysaccharide from the red algae Gelidiella acerosa (GaSP) was obtained through enzymatic extraction and subjected to chemical characterization by HPSEC, elemental microanalysis, FT-IR and NMR spectroscopies. The GaSP anticoagulant activity was investigated through APTT and PT tests and platelet aggregation assessed by turbidimetry. The antithrombotic and hemorrhagic activities were evaluated by venous thrombosis and hemorrhagic tendency models, respectively. FT-IR and NMR demonstrated that GaSP is a sulfated agaran. HPSEC and elemental microanalysis revealed a peak molar mass of 284.8 kDa and a degree of sulfation of 0.63, respectively. This molecule prolonged the coagulation time in 2.1 times and inhibited the platelet aggregation by 45%. Furthermore, it showed significant dose-dependent antithrombotic effect of 40%, 64% and 80% at 0.1, 0.5 and 1 mg/kg, respectively, without hemorrhage. These results suggest that GaSP has promising antithrombotic.

Seaweeds: an opportunity for wealth and sustainable livelihood for coastal communities.

The European, Canadian, and Latin American seaweed industries rely on the sustainable harvesting of natural resources. As several countries wish to increase their activity, the harvest should be managed according to integrated and participatory governance regimes to ensure production within a long-term perspective. Development of regulations and directives enabling the sustainable exploitation of natural resources must therefore be brought to the national and international political agenda in order to ensure environmental, social, and economic values in the coastal areas around the world. In Europe, Portugal requires an appraisal of seaweed management plans while Norway and Canada have developed and implemented coastal management plans including well-established and sustainable exploitation of their natural seaweed resources. Whereas, in Latin America, different scenarios of seaweed exploitation can be observed; each country is however in need of long-term and ecosystem-based management plans to ensure that exploitation is sustainable. These plans are required particularly in Peru and Brazil, while Chile has succeeded in establishing a sustainable seaweed-harvesting plan for most of the economically important seaweeds. Furthermore, in both Europe and Latin America, seaweed aquaculture is at its infancy and development will have to overcome numerous challenges at different levels (i.e., technology, biology, policy). Thus, there is a need for regulations and establishment of "best practices" for seaweed harvesting, management, and cultivation. Trained human resources will also be required to provide information and education to the communities involved, to enable seaweed utilization to become a profitable business and provide better income opportunities to coastal communities.

Effect of depth on growth and pigment contents of the macroalgae Gracilaria bursa-pastoris

The effects of environmental parameters on biomass, growth and pigment content of the red seaweed Gracilaria bursa-pastoris (S.G. Gmel.) P.C. Silva was investigated under field conditions in Thau Lagoon (France). The seaweed was cultivated in cages placed at three depths (1.0, 2.0 and 4.0 m) over a one-year period. The results showed elevated biomass and growth values in the spring and autumn, when temperature, light and photoperiod values were similar. The highest specific growth rates (SGR) were obtained at 1.0 m (4.95±0.29% day-1) and 2.0 m (4.45±0.33% day-1). At a depth of 4.0 m, the seaweed never exceeded 2% day-1 and obtained null values in the summer. The concentrations of phycoerythrin (RPE) and chlorophyll (CHL a) showed maximum values in the winter and minimum values in the summer. This evolution was related to water temperature, light intensity and nitrogen content in the algal tissue. The results obtained in this study show that the water depth influenced the growth and pigment composition of G. bursa-pastoris.

Antioxidant activity and chemical composition of the non polar fraction of Gracilaria domingensis (Kützing) Sonder ex Dickie and Gracilaria birdiae (Plastino & Oliveira)

Gracilaria domingensis (Kützing) Sonder ex Dickie and Gracilaria birdiae (Plastino & Oliveira) (Gracilariales, Rhodophyta) are seaweeds that occur on the Brazilian coast. Based on their economic and pharmaceutical importance, we investigated the antioxidant activity of the methanolic, ethyl acetate and hexane extracts of both species. The hexane extracts display a high antioxidant activity and comparative analyses indicated G. birdiae as the most active species. Chemical investigation of these fractions showed several carotenoids and fatty acids, as well as cholesterol and sitosterol derivatives. HPLC-DAD analysis of G. birdiae showed violaxanthin (0.04 μg.mg-1 of dry material), antheraxanthin (5.31 μg.mg-1), aloxanthin (0.09 μg.mg-1), zeaxanthin (0.45 μg.mg-1) and β-carotene (0.37 μg.mg-1) as the major carotenoids. G. domingensis showed a similar carotenoid profile, however, with much lower concentration than G. birdiae. Gas chromatography coupled to mass spectrometry was used to determine other nonpolar compounds of these seaweeds. The main compounds detected in both studied species were the fatty acids 16:0; 18:1 Δ9; 20:3 Δ6,9,12, 20:4 Δ5,8,11,14. We found no specificity of compounds in either species. However, G. birdiae, presented higher contents of carotenoids and arachidonic acid than G. domingensis.

Use of geographic information systems (GIS) to identify adequate sites for cultivation of the seaweed Gracilaria birdiae in Rio Grande do Norte, Northeastern Brazil

This study was designed to select potential areas for cultivation of the seaweed Gracilaria birdiae Plastino & E.C. Oliveira (Gracilariales, Rhodophyta) on the coast of Rio Grande do Norte state, Brazil. The Geographic Information System (GIS) and multi-criteria evaluation (MCE) were used to identify the most suitable areas. The Analytical Hierarchical Process (AHP) was applied to establish MCE weights, thereby generating viable areas for species cultivation. From a total of 3316.82 ha, around 53.67% (1780.06 ha) were indicated as highly suitable areas, 40.93% (1357.58 ha) as moderately suitable and 5.40% (179.18 ha) as scarcely suitable for seaweed cultivation. Seven areas (1084.62 ha) are located on the northern coast and 20 (2232.20 ha) on the eastern coast. The results show that GIS can be used as an effective instrument for selecting seaweed cultivation areas.

Influence of tourist activity on the diversity of seaweed from reefs in Maracajaú, Atlantic Ocean, Northeast Brazil

The worldwide increase in recreational activities and marine tourism is reason for concern due to its impact on reef environments. In order to assess the effect of tourism on the reef area in Maracajaú (Northeast Brazil), a study was conducted based on the presence of different seaweed species. A region of intense tourist activity was chosen, and another where tourism is prohibited. Result comparison used richness (S), biomass, diversity (H), and dominance (D), as well as an analysis of similarity between samples. Both areas exhibited differences in specific composition, biomass, diversity, richness and seaweed dominance. The highest values for biomass, richness and diversity were recorded in the tourism-free region, while the greatest dominance rates were found in the area of intense tourist activity. The latter was characterized by the dominant presence of Caulerpa racemosa (Forsskål) J. Agardh (Chlorophyta) and turf algae. These characteristics are a clear indication that the reef area subject to heavy tourist activity is undergoing degradation.

Seasonal changes in the pigment composition of natural population of Gracilaria domingensis (Gracilariales, Rhodophyta)

The concentrations of phycobiliproteins (phycoerythrin and phycocyanin), chlorophyll-a and total soluble proteins were determined monthly in three strains (red, green and brown) of Gracilaria domingensis (Kützing) Sonder ex Dickie, collected from natural populations on the coast of Rio Grande do Norte, Brazil. In all the strains, pigment and protein concentrations were higher in the months of less sunlight and greater nitrogen availability and decreased gradually with increased sunlight and decreased nutrient concentration. The red strain showed higher concentrations of phycoerythrin and total soluble proteins. The difference in the concentration of biochemical components over the course of the year indicates species acclimation to different environmental conditions.

Analyses of photoprotective compounds in red algae from the Brazilian coast

Qualitative and quantitative studies of mycosporine-like amino acids (MAAs) in three species of the genus Gracilaria Greville (G. birdiae, G. domingensis and G. tenuistipitata) were performed. A simple and efficient extraction procedure based on ethanol was described. HPLC, UV and mass spectrometry experiments revealed different profiles between extracts obtained from one species cultivated in the laboratory (G. tenuistipitata) and two species collected in their natural environment (G. birdiae and G. domingensis). The levels detected in the latter two species were approximately 150 times higher than in the species cultivated in vitro. This study revealed that G. birdiae and G. domingensis present a potential source for economical exploration of MAAs.

Macrolgae as an indicator of the environmental health of the Pirangi reefs, Rio Grande do Norte, Brazil

The coral reefs of Pirangi beach have suffered the impact of anthropic actions, mainly those related to tourism. To evaluate these effects, algal samples were collected at nine stations, distributed along the reef fringe. The macrobenthic community (algae/coral) was identified through photographic methods. A total of thirty species of algae, five species of coral, and one species of mollusk were identified. In areas of intense tourist activity, small algae were predominant, while in areas without human interference, foliose algae were predominant. Cluster analysis of the organisms revealed a pattern in spatial distribution into five zones: (1) a submerged zone with very diverse flora, (2) a zone with a predominance of Caulerpa racemosa, (3) a zone with high coverage of Sargassum vulgare, (4) a trampled zone with bare spaces, small algae and Zoanthus sociatus, and (5) a zone with predominance of Palythoa caribaeroum. The results show that human disturbances of the natural order can result in a different distribution model for benthic organisms in reefs. Moreover, these results allow us to infer that the area studied has undergone changes resulting from human activities and that the differences in biological composition can be used as an important indicator of the health of the Pirangi reef.

Phenology of an agarophyte Gracilaria birdiae Plastino and E.C. Oliveira (Gracilariales, Rhodophyta) in Northeastern Brazil

The reproductive phenology and thallus length of Gracilaria birdiae were studied over a period of 12 months in a natural bed in Northeastern Brazil. Fertile specimens of G. birdiae were observed during the entire study period. Tetrasporophytes were the most common with an annual mean of 80.1±5.6 percent, followed by cystocarpic plants (9.3±3.4 percent), male gametophytes (8.3±3.6 percent) and infertile plants (2.2±3.4 percent). Only male gametophytes and infertile plants showed a variation in occurrence frequency during the year (p<0.05). With respect to thallus length, a distinct seasonal variation was observed for all reproductive stages (p<0.05), with the highest values recorded during the rainy season (March to August) and the lowest in the dry season (September to February). The results demonstrate that the size of individuals in this population is significantly affected by the periodic changes in the environment caused by rainfall regimes and hydrodynamism.

Study on biofiltration capacity and kinetics of nutrient uptake by Gracilaria cervicornis (Turner) J. Agardh (Rhodophyta, Gracilariaceae)

The absorption efficiency and kinetic parameters (Vmax, Ks and Vmax:Ks) of the seaweed Gracilaria cervicornis for the nutrients NH4+, NO3- and PO4(3-) were evaluated. Absorption efficiency was measured by monitoring nutrient concentrations for 5 h in culture media with initial concentrations of 5, 10, 20 and 30µM. Kinetic parameters were determined by using the Michaelis-Menten formula. Absorption efficiencies for this algae were greater in treatments with lower concentrations, as evidenced by a reduction of 85.3, 97.5 and 81.2 percent for NH4+, NO3- and PO4(3-), respectively. Kinetic parameters show that G. cervicornis exhibits greater ability to take up high concentrations of NH4+ (Vmax=158.5µM g dw-1 h-1) and low concentrations of PO4(3-) (Ks=5µM and Vmax:Ks=10.3). These results suggest that this algal species has good absorption capacity for the nutrients tested and may be a promising candidate as a bioremediator of eutrophized environments.