Gracilaria Caudata Research Articles

Thermal tolerance of the red alga Gracilaria caudata reveals ecotypes for the Brazilian coast

Thermal tolerance of the red alga Gracilaria caudata reveals ecotypes for the Brazilian coast

Macroalgal diversity along an environmental gradient in a saltwork

Environmental physicochemical variation results in changes in the coastal biota. Macroalgae in saltworks have been poorly investigated regarding their distribution and the environmental factors that modulate the community. Thus, this study aimed to analyze the spatial distribution of macroalgae in a saltwork and the environmental parameters that drive them. Macroalgae were collected at 17 sampling points, where several environmental parameters were also determined. The sampling area was split into four sectors (S1, S2, S3, and S4) according to the recorded environmental gradient. An increase in salinity, temperature, and dissolved inorganic nitrogen was recorded from S1 (the sector closest to the sea) to S4 (the sector farthest from the sea), whereas depth showed an inverse pattern. A total of 31 macroalgal taxa were recorded in the saltwork. The highest number of macroalgal taxa (i.e., 27) was registered in S1. Macroalgal richness decreased in S2, S3, and S4. The most frequent genera in this study were Gracilaria sp. (Rhodophyta) and Caulerpa sp. (Chlorophyta), both with four species. Ochrophyta was only represented by Canistrocarpus cervicornis. Based on a redundancy analysis (RDA), increasing salinity, temperature, nitrite, and nitrate negatively affected the occurrence of macroalgae, whereas increasing pH positively affected the articulated calcareous macroalgae Amphiroa fragilissima and Jania sp., as well as the calcified Acetabularia sp. and the fleshy macroalgae Hypnea pseudomusciformis, Gracilaria caudata, and Ceramium sp. Increasing depth also positively affected the occurrence of macroalgae. In this study, it was possible to determine the distribution of macroalgae along an environmental gradient in a saltwork. The observed differences were driven by environmental changes, mainly in salinity, depth, and temperature.

Influence of the invasive bivalve Isognomon bicolor on the native community found in northeast Brazilian coast

The Caribbean bivalve Isognomon bicolor (C. B. Adams, 1845) is currently among the main invasive species along the Brazilian coast. The present study evaluated the co-occurrence, influence, and relationship of the native macrobenthic community with I. bicolor. The study was performed on samples collected from two sandstone reefs located in Northeast Brazil. We observed that the macrobenthic community differed significantly across reefs, zones, and seasons. The higher density of I. bicolor in the lower intertidal zone (347.7 ind/m² ± 800.8) was one of the main differentiation factors of zonation. The results indicated that the evenness of the community and some gastropods had a negative effect on I. bicolor. We found a negative correlation between the co-occurrence of I. bicolor with the macroalgae Hypnea sp. and Gracilaria caudata J. Agardh 1852 and the microgastropod Eulithidium affine (C. B. Adams, 1850). This study provides data on the relationship between I. bicolor and the native community of sandstone reefs, which could be applied to monitor the expansion of I. bicolor to the Northeast region of Brazil.

Metabolome of Cadmium Stressed Gracilaria caudata (Rhodophyta)

We report here the effects of cadmium on the metabolome of the macroalga Gracilaria caudata. The IC50 of 3 mg/L (12 µM) was obtained after 48 hrs exposure and induced lower photosynthesis efficiency. Threshold concentrations determined by the Brazilian Environmental Council (CONAMA) in marine waters (0.04 mg/L) and effluent discharge (0.2 mg/L) were also tested, and the latter changed photosynthetic efficiency similarly to IC50. A total of 43 metabolites were identified, including monosaccharides, carboxylic acids, and amino acids. By an unsupervised PCA, we identified significative alterations in the metabolome by the IC50. An OPLS-DA analysis showed that Cd2+ exposure caused the variation of 20 metabolites, mainly glyoxylate-related, ascorbate, floridoside and proline. Five metabolic pathways altered by Cd2+ showed an accumulation of amino acids, carbon metabolism intermediates and antioxidant responses to Cd2+. We recommend a review of the toxicity parameters and methods that guide environmental policies on cadmium levels in Brazilian marine waters.

Sulfated polysaccharide extracted from seaweed Gracilaria caudata attenuates acetic acid-induced ulcerative colitis

Marine macroalgae have high concentrations of sulfated polysaccharides (PLS) studies have demonstrated their antioxidant and anti-inflammatory effects. Certain structural features of PLS such as the formation of sulfate clusters are essential for their biological activities. PLS extracted from Gracilaria caudata have shown therapeutic potential and can be considered an alternative for the treatment of inflammatory bowel disease (IBD) such as ulcerative colitis (UC). The study objective is to evaluate an anti-inflammatory action of Gracilaria caudata PLS on acetic acid-induced intestinal damage in UC model in mice. Mice were treated with PLS from Gracilaria caudata 1.0, 3.0, and 10.0 mg/kg, intraperitoneally (ip) or dexamethasone 2.0 mg/kg, subcutaneously (sc) to determine the best dose of PLS to elicit an anti-inflammatory effect on UC. Colonic-tissue samples were collected for macroscopic analysis, wet weight, microscopic, and biochemical (MPO, GSH, MDA, NO3NO2, cytokine levels and Western blotting for iNOS) features. Treatment with PLS attenuated the colonic inflammatory process during the course of UC by reducing the macroscopic and microscopic scores and reducing the wet weight of the colon. Additionally, there was a reduction in MPO enzyme activity, GSH consumption, and reduction in MDA, NO3/NO2 and pro-inflammatory cytokine (IL-1β and TNF-α) concentrations and reduction in iNOS expression. This study indicates that Gracilaria caudata PLS have anti-inflammatory action on acetic acid-induced UC by reducing inflammatory infiltrate, oxidative stress, pro-inflammatory cytokine action, and iNOS expression. The data suggest that PLS have therapeutic potential against IBD such as UC.

Codominant inheritance of polymorphic color mutant and characterization of a bisexual mutant of Gracilaria caudata (Gracilariales, Rhodophyta)

The red alga Gracilaria caudata is one of the main agarophytes exploited on the Brazilian coast. A greenish-brown mutant was found growing side-by-side with the common red wild type in a natural population. In this work, we tested the hypotheses that the greenish-brown phenotype has a recessive nuclear inheritance and less fitness (growth, photosynthesis, number of apices, secondary attachment percentage, and number of cystocarps) under laboratory conditions when compared with the red phenotype. Crosses between plants of the same color (red or greenish-brown) showed tetrasporophytic and subsequent gametophytic generations with parental phenotype. However, heterozygous tetrasporophytes, obtained from crosses between plants with different colors, showed a brown phenotype. From their progeny, we concluded that the brown phenotype is due to a monolocus Mendelian genetic system with two codominant alleles. Bisexual gametophytes were found in the progeny of tetrasporophytic color mutants, which is an unusual and poorly known characteristic in the life cycle of Gracilariales. Red female gametophytes (rd genotype) presented better performance in relation to the greenish-brown female gametophytes (gb genotype): growth rates (rd = 17.14 ± 1.36, gb = 13.81 ± 0.95); number of apices (rd = 41.05 ± 6.35, gb = 16.00 ± 5.47); secondary attachment percentage (rd = 68.75 ± 23.93, gb = 25 ± 0.00); and number of cystocarps (rd = 38.61, gb = 18.81). Our results explain the maintenance of the greenish-brown mutant and the predominance of red specimens in natural population. The life cycle was completed in 5 months, one of the shortest times reported for Gracilaria, highlighting the importance of the species as a possible model organism for reproductive studies and in selecting strains for use in mariculture.

Integration of Fenton's reaction based processes and cation exchange processes in textile wastewater treatment as a strategy for water reuse

The remediation of a real textile wastewater aiming its reuse in the textile industry was carried out by integrating two processes: (i) a chemical or electrochemical advanced oxidation process (AOP or EAOP) based on Fenton's reaction for organics degradation, and (ii) a cation exchange process using marine macroalgae for removal of the iron acting in the Fenton's reaction based processes. Four AOPs/EAOPs at acidic pH 2.8 were tested: Fenton, photo-Fenton with ultraviolet A (UVA) radiation (PF/UVA), electro-Fenton (EF) and photoelectro-Fenton with UVA radiation (PEF/UVA). These processes provided very high color removals. After a running time of 45 min, the color removals were 68–95% for the Fenton process, 76–94% for the EF process, 80–98% for the PF/UVA process and 85–100% for the PEF/UVA process. In contrast, the mineralization was negligible for all the processes, indicating the generation/presence of persistent colorless compounds. The PF process was selected as first treatment stage due to its ability for color removal and related lower costs. A set of six marine macroalgae (Gracilaria caudata, Gracilaria cervicornis, Ascophyllum nodosum, Fucus spiralis, Laminaria hyperborea and Pelvetia canaliculata) were tested for iron uptake. Laminaria hyperborea showed the highest ion exchange capacity and affinity for iron species. Its application allowed the removal of all the iron acting in the PF process (3.4 mg/L). The textile wastewater resulting from the application of PF process followed by cation exchange with Laminaria hyperborea was successfully reused in scouring, bleaching and dyeing processes.

Sulfated polysaccharide from Gracilaria caudata reduces hypernociception and inflammatory response during arthritis in rodents

Polysaccharide from marine alga Gracilaria caudata has potential health benefits, such as anti-inflammatory, gastroprotective and antidiarrheal effects. Here, we investigated the effect of a sulfated polysaccharide from G. caudata (SP-GC) on hypernociception and inflammatory response in arthritis models. The animals received SP-GC (3, 10 or 30 mg/kg) 1 h before tibio-tarsal injection of zymosan. Hypernociception, histopathology, edema, vascular permeability, myeloperoxidase (MPO) activity, cell influx, interleukin (IL)-1β and nitric oxide (NO) levels were evaluated in acute phase. In another protocol, animals received SP-GC (30 mg/kg) 2 h post-complete Freund's adjuvant (CFA). Hypernociception, edema and arthritis index were determined in acute, sub-chronic and chronic phases. Rota-rod test measured the motor performance. SP-GC significantly reduced, in a dose-dependent manner, the zymosan-induced hypernociception with maximal effect at 30 mg/kg. The microscopic inflammation, joint edema, MPO activity, cell influx, IL-1β and NO levels were also reduced by SP-GC. In the CFA-induced arthritis, SP-GC inhibits the hypernociception, edema and arthritic index in acute, sub-chronic and chronic phases. SP-GC did not alter the motor performance of animals. In conclusion, SP-GC exerts protective effect in models of arthritis due to the modulation of cell influx, IL-1β and NO levels, culminating in the reduction of hypernociception and edema.

Polysaccharide from Gracilaria caudata protects the human esophageal mucosal barrier: A differential topical effect and structural dependence

This study aimed to evaluate the in vitro protective effect of topical treatment with a native sulfated polysaccharide of G. caudata (SP-Gc), hydrolyzed (H-SP-Gc), or desulfated (D-SP-Gc) polysaccharide of Gracilaria caudata in esophageal biopsies obtained from GERD patients. Biopsies were obtained from nonerosive reflux disease (NERD) patients and from erosive esophagitis patients. Then, the biopsies were mounted in an Ussing chamber to measure the basal transepithelial electrical resistance (TEER). The effect of mucosal exposure to an acid solution on TEER was analyzed with or without different concentrations (1, 0.3 or 1%) of SP-Gc, H-SP-Gc, or D-SP-Gc, precoated on the mucosa. Basal esophageal mucosal electrical resistance was significantly lower in erosive esophagitis than from NERD. Mucosal samples precoated with native SP-Gc (1%) significantly prevented TEER drop induced by an acidic solution in NERD, but this effect was not observed in erosive esophagitis. Topical application of D-SP-Gc showed no difference compared to native SP-Gc. However, when treated with chemically-modified SP-Gc, the protective effect observed with native SP-Gc was lost. The present study indicated that SP-Gc protects the human esophageal mucosal barrier in NERD patients. This effect is dependent on the structure but is independent of the presence of sulfate.

Macromolecule extracted from Gracilaria caudata reduces inflammation and restores hepatic function in nimesulide-induced hepatic damage

Seaweeds are a source of novel bioactive compounds such as sulfated polysaccharides (PLS) that are not found in plants, but that may confer health-promoting properties. Sulfated polysaccharides extracted from seaweeds have several biologically beneficial effects. The PLS extracted from the red alga Gracilaria caudata are known to have anti-inflammatory, antinociceptive, and gastroprotective activities. The present study aimed to evaluate the hepatoprotective effect of PLS obtained from G. caudata on a nimesulide-induced liver damage model. Hepatic lesions were induced in mice by oral doses of nimesulide (200 mg kg−1) administered once daily for 5 days. Once a day, 30 min after administration of nimesulide, PLS was administered intraperitoneally at concentrations of 2.5, 5, and 10 mg kg−1. Subsequently, blood was collected for biochemical tests and the liver was removed to evaluate inflammatory parameters. Administration of PLS at the dose of 10 mg kg−1 led to a significant reduction in hepatic injury, liver weight/animal weight ratio, the levels of a neutrophil migration marker (myeloperoxidase), pro-inflammatory cytokines (interleukin-1β and tumor necrosis factor-α), nitrate and nitrite, oxidative stress markers, and hepatic function markers. As per our results, the PLS extracted from G. caudata was able to modulate the inflammatory response in nimesulide-induced hepatic damage in addition to re-establishing the hepatic homeostatic functions.

Dual influence of terrestrial and marine historical processes on the phylogeography of the Brazilian intertidal red alga Gracilaria caudata

In this study, we explored how past terrestrial and marine climate changes have interacted to shape the phylogeographic patterns of the intertidal red seaweed Gracilaria caudata, an economically important species exploited for agar production in the Brazilian north-east. Seven sites were sampled along the north-east tropical and south-east sub-tropical Brazilian coast. The genetic diversity and structure of G.caudata was inferred using a combination of mitochondrial (COI and cox2-3), chloroplast (rbcL) and 15 nuclear microsatellite markers. A remarkable congruence between nuclear, mitochondrial and chloroplast data revealed clear separation between the north-east (from 03°S to 08°S) and the south-east (from 20°S to 23°S) coast of Brazil. These two clades differ in their demographic histories, with signatures of recent demographic expansions in the north-east and divergent populations in the south-east, suggesting the maintenance of several refugia during the last glacial maximum due to sea-level rise and fall. The Bahia region (around 12°S) occupies an intermediate position between both clades. Microsatellites and mtDNA markers showed additional levels of genetic structure within each sampled site located south of Bahia. The separation between the two main groups in G.caudata is likely recent, probably occurring during the Quaternary glacial cycles. The genetic breaks are concordant with (i) those separating terrestrial refugia, (ii) major river outflows and (iii) frontiers between tropical and subtropical regions. Taken together with previously published eco-physiological studies that showed differences in the physiological performance of the strains from distinct locations, these results suggest that the divergent clades in G.caudata correspond to distinct ecotypes in the process of incipient speciation and thus should be considered for the management policy of this commercially important species.

Brazilian native species of Gracilaria (Gracilariales, Rhodophyta) as a source of valuable compounds and as nutritional supplements

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.

Sulfated polysaccharides from the marine algae Gracilaria caudata prevent tissue damage caused by ligature-induced periodontitis.

Sulfated polysaccharides (PLS) extracted from the marine algae of the genus Gracilaria showed biological activity in different inflammatory models, except for periodontitis. Thus, this study aimed to evaluate the effectiveness of the treatment with PLS from Gracilaria caudata in ligature-induced periodontitis. 40 animals distributed into 5 groups were used (the control group (unligated), the ligated untreated group, and the ligated groups treated with 2.5, 5.0 and 10.0 mg/kg of PLS with intraperitoneal injection, respectively). After 20 days of treatment, the animals were killed and the following parameters were evaluated: Gingival Bleeding Index (GBI), Probing Pocket Depth (PPD), Myeloperoxidase (MPO) activity, Alveolar Bone Loss (ABL) for periodontal tissues; histopathological examination of gingival and liver tissues (Steatosis score); glutathione and malondialdehyde concentrations in the liver, serum levels of alanine aminotransferase and aspartate aminotransferase. The data revealed that treatment with 2.5 mg/kg of PLS showed the best anti-inflammatory effects with reduction of GBI, PPD and MPO activity, as well as oxidative stress and steatosis in liver. Our results indicated that the adjunct treatment with PLS from Gracilaria caudata could prevent the periodontal and hepatic tissue alteration caused by periodontitis.

A novel antioxidant sulfated polysaccharide from the algae Gracilaria caudata: In vitro and in vivo activities

Marine red macroalgae are natural sources of sulfated polysaccharides, water-binding molecules used in the food industry as thickeners, stabilizers and gelling agents. Sulfated polysaccharides extracted from the red seaweed Gracilaria caudata also show biological activities with potential therapeutic effects against diseases associated with oxidative stress; hence, it is possible that they may be used as nutraceuticals and/or food additives. This study aimed to obtain the sulfated polysaccharides from G. caudata (SP-Gc) through enzymatic extraction and to determine their chemical structure and antioxidant potential. Inductively Coupled Plasma-Optical Emission Spectrometry showed that SP-Gc have 0.9% of sulfur atoms and a degree of sulfation of 0.14%. An average molecular mass of 116.51 kDa was determined through gel permeation chromatography. The SP-Gc structure as an agar-type galactan was determined by Fourier transform infrared (FTIR) spectroscopy and nuclear magnetic resonance (NMR) spectroscopy (13C and 1H). The in vitro antioxidant activity of SP-Gc was determined through the following tests: ferrous ion chelating ability and total antioxidant capacity. The results indicated that SP-Gc have significant antioxidant activity in a concentration-dependent manner. The in vivo antioxidant activity of SP-Gc was evaluated in an oxidative stress model induced by 2,2′-azobis(2-methylpropionamidine) dihydrochloride (ABAP) in rats pretreated with SP-Gc (3 and 10 mg/kg). Catalase (CAT) and superoxide dismutase (SOD) levels were measured and all doses increased CAT and SOD activity. These results demonstrate that SP-Gc may be used as hydrocolloids, due to their characterization as agar, and as nutraceuticals, due to their antioxidant activity.

Physiological responses of the red algae Gracilaria caudata (Gracilariales) and Laurencia catarinensis (Ceramiales) following treatment with a commercial extract of the brown alga Ascophyllum nodosum (AMPEP)

Extracts of brown algae are used commercially for agricultural crops due to their plant growth-promoting effects and they can also be applied to help improve seaweed cultivation. Gracilaria caudata is commercially exploited as a raw material for agar production in Brazil, and Laurencia catarinensis is a source of halogenated terpenoids with several biological activities. Investigations to understand the development of seaweeds of biotechnological interest are required in order to improve their cultivation and the sustainability for biomass production on an industrial scale. The aim of the present study was to evaluate the effects of Ascophyllum/Acadian marine plant extract powder (AMPEP), a commercial, water-soluble extract of the brown alga Ascophyllum nodosum, on the growth, branching development, and pigment content of G. caudata and L. catarinensis. Four concentrations of AMPEP (0, 0.1, 1.0, and 5.0 mg L−1) were added to sterilized seawater (seawater+AMPEP), and to a medium comprised of half-strength von Stosch solution (VSES/2+AMPEP). Experiments were performed under conditions of 23 ± 2 °C, a light:dark cycle of 14:10 h, salinity at 32 psu, and photon flux densities of 60 ± 10 μmol photons m−2 s−1. Data were analyzed by one-way ANOVA, followed by a posteriori multiple comparison, Student-Newman-Keuls’ test. Treatments of seawater+AMPEP at concentrations of 0.1 and 1.0 mg L−1 stimulated the growth rates of G. caudata when compared to the control. However, the effects of seawater+AMPEP and VSES/2+AMPEP on the branching architecture of the thalli were not significant for either species. Concentrations of phycoerythrin, phycocyanin, allophycocyanin, and chlorophyll-a in L. catarinensis were stimulated by the highest concentration of VSES/2+AMPEP (i.e., 5.0 mg L−1). This is the first study to report the stimulatory effect of AMPEP on the phycobiliprotein contents of selected red algae. Furthermore, seawater+AMPEP in concentrations of 0.1 and 1.0 mg L−1 stimulated growth rates of G. caudata, which could be applied in its large-scale cultivation. The results obtained for G. caudata and L. catarinensis, an agar-producing and a terpenoid-producing species, respectively, contributed to extending the knowledge of the beneficial uses of a brown seaweed-derived extract with biostimulatory properties for use with cultivated, economically important red algae.

Gracilaria caudata (Gracilariales, Rhodophyta) is reproductively compatible along the whole Brazilian coast

Gracilaria spp. are economically important for the production of agar. The distribution of ecotypes of Gracilaria caudata all along the Brazilian coast raises questions regarding whether they are undergoing speciation and are possibly reproductively incompatible. Therefore, in the present work, we selected different female and male gametophytes of G. caudata from three populations along an extended Brazilian coastline (from 3° to 23° S) to perform crossing tests and observe possible reproductive barriers. In addition, we tested post-zygotic isolation, by following meiosis, the production of haploids, and the reproduction of haploids, in the progeny of these inter-population crosses. DNA sequences of the mitochondrial cytochrome c oxidase subunit 1 gene (COI) were used to determine relationships among all gametophytes employed in the crosses and to understand inheritance of mitochondria. The crosses showed interfertility between all populations tested. Neither pre- nor postzygotic isolation was seen in G. caudata from Brazil. Individuals with haplotypes that differ by 1–5 bp (0.15–0.79% divergences) in COI were reproductively compatible. In conclusion, the exchange of genetic material among populations from a wide geographic distribution allows consideration of G. caudata as a biological species.

Effects of extracts and isolated molecules of two species of Gracilaria (Gracilariales, Rhodophyta) on early growth of lettuce

Crude extracts using hexane, dichloromethane, methanol, 80% methanol or water of two agarophytes (Gracilaria caudata and Gracilaria domingensis) and their phase partitions were evaluated on early growth of lettuce. Hexane, methanol, 80% methanol and aqueous extracts of G. caudata and dichloromethane and aqueous extracts of G. domingensis were biostimulants. Palmitic acid, the major compound of non-polar extracts and phase partition, showed a significant stimulant activity in the concentrations tested (ranging from 0.49 mM to 1.95 mM), increasing 83% of lettuce root length, comparing to control, at the highest concentration. The promoting effect of the aqueous extracts is probably related to the presence of agaran, a typical hydrocolloid polysaccharide from red algae, which is mostly an exclusive constituent of these extracts. The agarans of G. domingensis and G. caudata promoted an increase in lettuce root length of 60% and 40%, respectively (both at 1 mg·mL−1 of extract). Differences in the effects promoted by these two agarans are probably related to the different content of sulfate groups (higher for polysaccharide from G. domingensis). These results suggest that structural features of agaran-type polysaccharides can elicit distinct responses. To the best of our knowledge, this is the first report on the identification of compounds with biostimulating potential from Gracilaria.

Application of ecofriendly cation exchangers (Gracilaria caudata and Gracilaria cervicornis) for metal ions separation and recovery from a synthetic petrochemical wastewater: Batch and fixed bed studies

Red macro-algae Gracilaria caudata and Gracilaria cervicornis were used as cation exchangers for transition metals (copper, nickel and zinc) from a synthetic petrochemical wastewater. Scarce information is available in the literature about the use of red algae as natural cation exchanger and the effect of multicomponent aqueous matrix on the treatment performance. In the present work, the transition metals separation and recovery were evaluated considering the matrix effect. The ion exchange capacities for both red algae were near 1.2 mEq/g, which corresponds to the total amount of light metals present on the surface of raw algae. A heterogeneous model, considering 3 inflection points, was developed to enable the identification and quantification of the functional groups present on the biomass surface and the results obtained are in agreement with the total amount of light metals obtained by biomass digestion. Equilibrium and kinetic experiments were conducted using both raw algae and calcium loaded G. cervicornis. Cation exchange equilibrium was described by a Langmuir multicomponent model. The equilibrium affinity constants for the functional groups increases in the following order: nickel < zinc ≪ copper. G. cervicornis showed a higher selectivity for the transition metals present in the synthetic petrochemical wastewater and it was used in the following tests. Calcium loaded G. cervicornis showed a higher affinity to copper than for zinc and nickel. Biomass regeneration was evaluated using several eluents (ultrapure water and 0.1 M solutions of hydrochloric acid, nitric acid, sulfuric acid, sodium chloride, calcium chloride and sodium hydroxide) and regenerant solutions (0.5 M solutions of calcium chloride and sodium chloride). Cation exchange breakthrough curves obtained from a column packed with raw G. cervicornis, led to a useful capacity of 0.25 and 0.24 mEq/g for the first and second operation cycles. A mass transfer model, considering a linear driving force model for intraparticle diffusion, was able to predict well the ion exchange process for all species studied at batch and packed bed systems. A treatment strategy using a column system in series was proposed to increase the treated water volume using G. cervicornis as a natural cation exchange resin, being possible the recovery of transition metals from separate solutions.

Ecotypes of Gracilaria caudata (Gracilariales, Rhodophyta): physiological and morphological approaches considering life history phases

On the Brazilian coast, the red alga Gracilaria caudata J. Agardh is exploited for agar production. In view of its economic importance for potential mariculture, this work aimed to elucidate and characterize ecotypes along an extended Brazilian coastline by evaluating the effects of irradiance (70 and 150 μmol photons m−2 s−1) on the number of differentiated branches, growth rates (GRs), photosynthesis parameters, and pigment content of female gametophytes and tetrasporophytes from three distinct geographical areas: Ceara State (CE), Bahia State (BA), and Sao Paulo State (SP). Compared to low irradiance, high irradiance promoted higher GRs and a greater number of differentiated branches, as well as maximum electron transport rate (ETRmax) and maximum photosynthesis (P max) in both phases. However, irrespective of population or irradiance, tetrasporophytes had higher ETRmax (3.30 μmol e− m−2 s−1) than gametophytes (2.54 μmol e− m−2 s−1), corroborating the hypothesis that tetrasporophytes have better physiological performance than gametophytes, implicating correspondingly better adaptive abilities. Under high irradiance, regardless of the period of cultivation (14 or 28 days), strains from CE presented the highest GR (15% day−1) when compared to strains from SP (14% day−1) and BA (13% day−1). CE strains also had the highest number of differentiated branches and P max. Based on these results, we suggest that CE strains are the best candidates for future experimental mariculture tests. Importantly, overall differences in physiological performance among the strains from different populations give evidence of intraspecific diversity, thus supporting the hypothesis of ecotypic differentiation and allowing this study to define different G. caudata ecotypes.

Effects of cytokinins on physiological and biochemical responses of the agar-producing red alga Gracilaria caudata (Gracilariales, Rhodophyta)

The red alga Gracilaria caudata J. Agardh (Gracilariales) is commercially exploited in Brazil as a source of raw material for agar production, and its cultivation is needed for sustainable biomass production to avoid overexploitation of natural populations. The objective of the present study was to evaluate the effects of aromatic and isoprenoid-derived cytokinins under two photon flux densities (PFDs) on growth rates, formation of lateral branches, pigment content (chlorophyll a and phycobiliproteins), and total soluble proteins in G. caudata. Aromatic cytokinins (benzylaminopurine, BA, and kinetin, K) and isoprenoid cytokinins (2-isopentenyladenine, 2iP, cis-zeatin, and trans-zeatin) were tested at 50 and 100 μmol photons m−2 s−1, temperature of 23 ± 1 °C, and light:dark cycle of 14:10 h. Cytokinins were added to the ASP 12-NTA synthetic medium (salinity 30 PSU, pH 8.0) in concentrations ranging from 0.0 to 50.0 μM. Growth rates of G. caudata were not affected by addition of isoprenoid and aromatic cytokinins. Zeatins (cis and trans forms) and BA at the concentrations of 0.5 and/or 5.0 μM stimulated the branch formation at 100 μmol photons m−2 s−1. In general, concentrations of isoprenoid cytokinins showed negative correlation with total soluble proteins and pigment contents at both PFDs. On the other hand, aromatic cytokinins did not affect protein contents, and K inhibited the pigment contents in both PFD levels. In conclusion, our results indicate that the isoprenoid and aromatic cytokinins and PFD levels did not affect the growth rates of G. caudata, but influence the branching and contents of pigments and total soluble proteins. Moreover, aromatic cytokinins and zeatins stimulated branch formation, which is a morphogenetic process useful for micropropagation of G. caudata, and could improve its cultivation in the Brazilian coast.