Chemical Composition, Antioxidant, and Antitumor Activity of Fucoidan from the Brown Alga Dictyota dichotoma.

Brown macroalgae are a rich source of fucoidans with many pharmacological uses. This research aimed to isolate and characterize fucoidan from Dictyota dichotoma var. dichotoma (Hudson) J.V. Lamouroux and evaluate in vitro its antioxidant and antitumor potential. The fucoidan yield was 0.057 g/g algal dry wt with a molecular weight of about 48.6 kDa. In terms of fucoidan composition, the sulfate, uronic acid, and protein contents were 83.3 ± 5.20 mg/g fucoidan, 22.5 ± 0.80 mg/g fucoidan, and 26.1 ± 1.70 mg/g fucoidan, respectively. Fucose was the primary sugar component, as were glucose, galactose, mannose, xylose, and glucuronic acid. Fucoidan exhibited strong antioxidant potential that increased by more than 3 times with the increase in concentration from 0.1 to 5.0 mg/mL. Moreover, different concentrations of fucoidan (0.05-1 mg/mL) showed their ability to decrease the viability of Ehrlich ascites carcinoma cells in a time-dependent manner. These findings provided a fast method to obtain an appreciable amount of natural fucoidan with established structural characteristics as a promising compound with pronounced antioxidant and anticancer activity.

Protective Effect of a Fucose-Rich Fucoidan Isolated from Saccharina japonica against Ultraviolet B-Induced Photodamage In Vitro in Human Keratinocytes and In Vivo in Zebrafish.

A fucose-rich fucoidan was purified from brown seaweed Saccharina japonica, of which the UVB protective effect was investigated in vitro in keratinocytes of HaCaT cells and in vivo in zebrafish. The intracellular reactive oxygen species levels and the viability of UVB-irradiated HaCaT cells were determined. The results indicate that the purified fucoidan significantly reduced the intracellular reactive oxygen species levels and improved the viability of UVB-irradiated HaCaT cells. Furthermore, the purified fucoidan remarkably decreased the apoptosis by regulating the expressions of Bax/Bcl-xL and cleaved caspase-3 in UVB-irradiated HaCaT cells in a dose-dependent manner. In addition, the in vivo UV protective effect of the purified fucoidan was investigated using a zebrafish model. It significantly reduced the intracellular reactive oxygen species level, the cell death, the NO production, and the lipid peroxidation in UVB-irradiated zebrafish in a dose-dependent manner. These results suggest that purified fucoidan has a great potential to be developed as a natural anti-UVB agent applied in the cosmetic industry.

Emission of volatile halogenated compounds, speciation and localization of bromine and iodine in the brown algal genome model Ectocarpus siliculosus.

This study explores key features of bromine and iodine metabolism in the filamentous brown alga and genomics model Ectocarpus siliculosus. Both elements are accumulated in Ectocarpus, albeit at much lower concentration factors (2-3 orders of magnitude for iodine, and < 1 order of magnitude for bromine) than e.g. in the kelp Laminaria digitata. Iodide competitively reduces the accumulation of bromide. Both iodide and bromide are accumulated in the cell wall (apoplast) of Ectocarpus, with minor amounts of bromine also detectable in the cytosol. Ectocarpus emits a range of volatile halogenated compounds, the most prominent of which by far is methyl iodide. Interestingly, biosynthesis of this compound cannot be accounted for by vanadium haloperoxidase since the latter have not been found to catalyze direct halogenation of an unactivated methyl group or hydrocarbon so a methyl halide transferase-type production mechanism is proposed.

Intracellular localization and induction of a dynamic RNA-editing event of macro-algal V-ATPase subunit A (VHA-A) in response to copper.

A V-ATPase subunit A protein (VHA-A) transcript together with a variant (C793 to U), which introduces a stop codon truncating the subunit immediately downstream of its ATP binding site, was identified within a Fucus vesiculosus cDNA from a heavy metal contaminated site. This is intriguing because the VHA-A subunit is the crucial catalytic subunit responsible for the hydrolysis of ATP that drives ion transport underlying heavy metal detoxification pathways. We employed a chemiluminescent hybridization protection assay to quantify the proportion of both variants directly from mRNA while performing quantification of total transcript using Q-PCR. Polyclonal antisera raised against recombinant VHA-A facilitated simultaneous detection of parent and truncated VHA-A and revealed its cellular and subcellular localization. By exploiting laboratory exposures and samples from an environmental copper gradient, we showed that total VHA-A transcript and protein, together with levels of the truncated variant, were induced by copper. The absence of a genomic sequence representing the truncated variant suggests a RNA editing event causing the production of the truncated VHA-A. Based on these observations, we propose RNA editing as a novel molecular process underpinning VHA trafficking and intracellular sequestration of heavy metals under stress.

Brown algae and their multiple applications as functional ingredient in food production.

Brown algae are considered one of the resources that can contribute to transforming our global food system by promoting healthier diets and reducing environmental impact. In this sense, this review article aims to provide up-to-date information on the nutritional and functional improvement of brown algae when they are applied to different food matrices. Brown algae present sulfated polysaccharides (alginates, fucoidans, and laminarins), proteins, minerals, vitamins, dietary fibers, fatty acids, pigments, and bioactive compounds that can positively contribute to the development of highly nutritious food products, as well as used reformulate products already existing, to remove, reduce, increase, add and/or replace different components and obtain products that confer health-promoting properties. This review demonstrates that there is a tendency to use seaweed for the production of functional foods and that the number of commercially produced products from seaweed is increasing, that is, seaweed is a sector whose global market is expanding.

Algal Carotenoids: Chemistry, Sources, and Application.

Recently, the isolation and identification of various biologically active secondary metabolites from algae have been of scientific interest, with particular attention paid to carotenoids, widely distributed in various photosynthetic organisms, including algal species. Carotenoids are among the most important natural pigments, with many health-promoting effects. Since the number of scientific studies on the presence and profile of carotenoids in algae has increased exponentially along with the interest in their potential commercial applications, this review aimed to provide an overview of the current knowledge (from 2015) on carotenoids detected in different algal species (12 microalgae, 21 green algae, 26 brown algae, and 43 red algae) to facilitate the comparison of the results of different studies. In addition to the presence, content, and identification of total and individual carotenoids in various algae, the method of their extraction and the main extraction parameters were also highlighted.

Nutritional, bioactive compounds content, and antioxidant activity of brown seaweeds from the Red Sea.

Introduction: Brown seaweeds are excellent sources of bioactive molecules with a wide range of pharmacological effects, whose content can vary depending on several factors, including the origin and the environment in which the algae grow. Methods: This study aimed to estimate 19 compounds regarding primary and secondary metabolites of eight brown macroalgal species from a clean Egyptian Red Sea coast. A proximate analysis, pigment, phenolic compounds, and vitamin contents were determined. In addition, the energy content and antioxidant activity were estimated to explore the potential application of algae as functional foods to encourage the species' commercialization. Results: Based on the chemical composition, Polycladia myrica was the most valuable species, with a comparatively high protein content of 22.54%, lipid content of 5.21%, fucoxanthin content of 3.12 µg/g, ß-carotene content of 0.55 mg/100 g, and carbohydrate content of 45.2%. This species also acts as a great source of vitamin C, flavonoids, tannins, phenol content and total antioxidant capacity. Discussion: The antioxidant activity of the selected algae indicated that its phenol, vitamin and pigment contents were powerful antioxidant compounds based on the structure-activity relationships. This result was verified by the strong correlation in statistical analysis at the 95% confidence level. From a worldwide perspective and based on the obtained results, these brown species may be reinforced as an essential line in future foods.

Antimicrobial activity of some macroalgae of the Veracruzano Reef System (SAV), Mexico.

The study of macroalgae antimicrobial agents is limited to Mexico and scarce in the Veracruzano Reef System (SAV). It is necessary to devote efforts towards this field of applied phycology. The aim was to evaluate the antimicrobial activity of some phyla of Rhodophyta, Chlorophyta and Ochrophyta from SAV. Methanolic extracts from 23 marine macroalgae species (7 Chlorophyta, 4 Phaeophyta and 12 Rhodophyta) from the Veracruzano Reef System (SAV) (Mexico) were evaluated for antimicrobial activity. Antibacterial and antifungal activity were assessed by agar diffusion and agar dilution methods. The differences between mean values obtained for experimental groups was done by analysis of variance (ANOVA multifactorial model), p-values of 0.001 or less were considered statistically significant. Two new records are recognized for SAV (Laurencia gracilis and Sebdenia flabellata) and Compsothamnion thuioides for the Gulf of Mexico coasts. 16 species showed antibacterial activity, of which Caulerpa sertularioides, Ulva lactuca and Laurencia obtuse had significant activity on Gram-positive bacteria. 43.7% belong to the phyla Chlorophyta (7 species), 50% Rhodophyta (8 species) and 6.25% Ochrophyta (1 species). This indicates that the extracts of the algae of the Rhodophyta and Chlorophyta are the ones that showed the greatest activity. Regarding the yeasts, 16.6% of the total algae collected were active in the different yeast strains. 43.7% belongs to Chlorophyta species and for Rhodophyta were 60%. The macroalgae with the highest antifungal activity were: Cymopolia barbata, Ulva lactuca and Laurencia gracilis. The macroalgae of the Veracruzano Reef System present antimicrobial activity. This study is the first investigation of macroalgae's bioactive components from SAV, where they could be sources for future medical applications.

Anti-colorectal cancer effects of seaweed-derived bioactive compounds.

Seaweeds are classified as Chlorophyta, Rhodophyta, and Phaeophyta. They constitute a number of the most significant repositories of new therapeutic compounds for human use. Seaweed has been proven to possess diverse bioactive properties, which include anticancer properties. The present review focuses on colorectal cancer, which is a primary cause of cancer-related mortality in humans. In addition, it discusses various compounds derived from a series of seaweeds that have been shown to eradicate or slow the progression of cancer. Therapeutic compounds extracted from seaweed have shown activity against colorectal cancer. Furthermore, the mechanisms through which these compounds can induce apoptosis in vitro and in vivo were reviewed. This review emphasizes the potential utility of seaweeds as anticancer agents through the consideration of the capability of compounds present in seaweeds to fight against colorectal cancer.

Green extraction of proteins, umami and other free amino acids from brown macroalgae Ascophyllum nodosum and Fucus vesiculosus.

Seaweeds are a valuable potential source of protein, as well as free amino acids (FAAs) with umami flavour which are in high demand by the food industry. The most commonly used flavouring agents in the food industry are chemically synthesised and therefore are subject to concerns regarding their safety and associated consumer resistance. This study focuses on the effects of extraction time (1 and 2 h) and solvents (0.1 M HCl, 1% citric acid and deionised water) on the extraction of protein and FAAs including umami FAAs from Irish brown seaweeds (Ascophyllum nodosum and Fucus vesiculosus). Extraction yields were influenced by both the extraction solvent and time, and also varied according to the seaweed used. Both seaweeds investigated were found to be good sources of protein, FAAs including umami FAAs, demonstrating potential application as flavouring agents in the food industry. Overall, the use of green solvents (deionised water and citric acid) resulted in higher recoveries of compounds compared to HCl. The results of this study will facilitate the use of more sustainable solvents in industry for the extraction of proteins and flavouring agents from seaweed.

Proximate Analysis of Selected Macroalgal Species from the Persian Gulf as a Nutritional Resource.

Nowadays the exploration and utilisation of food and feed from marine origin is becoming more important with the increase of human population. Macroalgae are rich in nutritious compounds, which can directly be used in human and animal feed industries. The current study presents the screening of chemical components of eight macroalgae species, Sargassum boveanum, Sirophysalis trinodis, Hypnea caroides, Palisda perforata, Galaxaura rugosa, Caulerpa racemose, Caulerpa sertularioides and Bryopsis corticolans from the Persian Gulf. The results revealed that the eight studied algal species possess high protein (14.46% to 38.20%), lipid (1.27% to 9.13%) and ash (15.50% to 49.14%) contents. The fatty acids and amino acids profile showed the presence of essential fatty acids and amino acids with high nutritional value. Phaeophyta species, S. boveanum and S. trinodis, showed the highest value of ash content and polyunsaturated fatty acids while Chlorophyta species, C. racemose, C. sertularioides and B. corticolans, showed the highest level of lipid and protein contents. Rhodophyta species, G. rugosa and P. perforata, showed the highest essential amino acid content. In conclusion, this study demonstrates the potential of the studied marine species as a nutritional source for human and animal uses.

A study of the chemical diversity of macroalgae from South Eastern Australia.

Macroalgae are a rich source of biologically active chemical diversity for pharmaceutical and agrichemical discovery. However, the ability to understand the complexities of their chemical diversity will dictate whether these natural products have a place in modern discovery paradigms. In this study, we examined the relationship between secondary metabolite production and biological activity for a cohort of 127 macroalgae samples collected from various locations across South Eastern Australia. Approximately 20% of the macroalgae samples showed high levels of chemical diversity and productivity, which also correlated strongly with bioactivity. These "talented" species represent sustainable sources of metabolites that may be readily harvested for large-scale production. At a taxonomic level, significant differences in metabolite production and diversity were observed between Chlorophyta, Rhodophyta and Phaeophyta. For each talented species, the cometabolite pattern was unique to that species, with closely related species within the same genus displaying very different profiles. Despite over 50years of investigation, we estimate that more than two-thirds of the chemical diversity of macroalgae remains unknown to science. By understanding the physicochemical properties and distribution patterns of metabolites, it is possible to make reasoned judgements about sustainable sourcing of macroalgae for biodiscovery.

Early development and substrate twine selection for the cultivation of Sargassum muticum (Yendo) Fensholt under laboratory conditions.

The phaeophyte macroalgae Sargassum muticum is under investigation as a cultivation crop within its native range in SE Asia, alongside other members of the Sargassum genus. During the critical hatchery phase, germlings are grown to ≥ several millimeters ready for outplanting. By optimising the growth medium and twine substrate used for the germling attachment, hatcheries can become more efficient and cost-effective. An 8-week replicated laboratory experiment investigated these factors. It found that adding 0.125 mL L-1 of saturated germanium dioxide during the first week increased mean germling size by 23% (p < 0.005), whereas additional nutrients in the form of F/2 medium made no difference (p > 0.05). Six twine substrates were also tested: jute, cotton, polyamide/cotton, polyester, polyvinyl alcohol and polypropylene. Sargassum muticum grew similarly well on all, although attachment success during the first week was highest on the rougher natural fibres, particularly jute. A negative density-dependent effect of germling density on growth was seen across all materials, with the highest growth seen on the materials with the lowest germling density. Jute is recommended as a highly suitable substrate for hatchery cultivation in this species, although the initial density should be carefully controlled to prevent intraspecific competition.

Metal Concentrations in Wild-Harvested Phaeophyta Seaweed from the Atlantic Ocean (Canary Islands, Spain).

Seaweeds are being consumed more often worldwide and are a source of essential minerals, fiber, vitamins, amino acids, and various bioactive compounds that have many beneficial effects on human health. However, marine pollution and the high capacity of seaweed to absorb metals may mean this food can also be dangerous to human health. The concentrations of some trace elements (B, Ba, Fe, Ni, Li, and V) and toxic metals (Al, Cd, and Pb) were determined in various species of wild seaweeds in the Phaeophyta group of brown algae from the Atlantic Ocean. Inductively coupled plasma atomic emission spectrometry revealed high concentrations of Al (256 mg/kg dry weight), Pb (3.92 mg/kg dry weight), and Cd (0.20 mg/kg dry weight) in Padina pavonica. Pb contributed the most to the tolerable daily intake (TDI) of toxic metals in these samples; 57.2 and 45.3% of the TDI for Pb was found in 5 g of dehydrated P. pavonica and Halopteris scoparia, respectively. This percent contribution is half of the recommended TDI for this metal, which is 34.24 µg/day; therefore, high consumption of these species is discouraged. The maximum TDIs established by various institutions for the other metals were not exceeded from the daily consumption of 5 g of the other dehydrated seaweeds evaluated in this study.

Actividad citotóxica y antiproliferativa de un extracto rico en fucoidan de Lessonia trabeculata sobre células de adenocarcinoma mamario murino 4T1

Introducción. Los tumores neoplásicos se caracterizan por su invasividad y metástasis. Las células neoplásicas tienen heterogeneidad genética, por lo cual pueden desarrollar resistencia a los quimioterápicos. Por esta razón, las plantas continúan siendo una fuente importante de nuevos productos anticancerígenos. Objetivo. Evaluar la actividad citotóxica y antiproliferativa de un extracto rico en fucoidan de Lessonia trabeculata nativa (EFLt) sobre la línea celular de adenocarcinoma mamario murino, triple negativo 4T1. Métodos. La citotoxicidad y la IC50 se determinaron en monocapas de 4T1 empleando el reactivo MTT. Para demostrar la actividad antiproliferativa se aplicaron los métodos de cierre de herida y anticlonogénico utilizando las IC50 del EFLt y Dox (doxorubicina). El cierre de herida fue evaluado mediante barrido de tiempos discretos; el efecto anticlonogénico fue evaluado 7 días postratamiento mediante el conteo de colonias y se determinó la fracción de sobrevivencia. Adicionalmente, se evaluaron la citotoxicidad y actividad antiproliferativa combinando las IC50 de EFLt y Dox. El porcentaje de migración y conteo de colonias se realizó con el programa ImageJ. Resultados. La IC50 del EFLt (950 μg/mL) produjo 56% de citotoxicidad, 80,3% de inhibición de la migración celular, 68% de inhibición en la formación de colonias. La IC50 de Dox fue 0,5 μg/mL. Conclusiones. El EFLt ejerce citotoxicidad dependiente de la concentración y tiene efecto antiproliferativo sobre 4T1. Se requiere continuar los ensayos en modelos de mayor complejidad que permitan esclarecer el potencial antitumoral del EFLt.

Introduction. Neoplastic tumors are characterized by invasiveness and metastasis. Neoplastic cells are genetically heterogeneous and can develop resistance to chemotherapeutic agents. For this reason, plants continue to be an important source of new anticancer products. Objective. To determine the cytotoxic and antiproliferative activity of a fucoidan-rich extract of native Lessonia trabeculata (EFLt) on the tripe negative murine mammary adenocarcinoma cell line 4T1. Methods. Cytotoxicity and IC50 were determined in 4T1 monolayers using the MTT reagent. To demonstrate antiproliferative activity, "wound" closure and anticlonogenic methods were applied using the IC50 of EFLt and Doc (doxorubicin). "Wound" closure was evaluated by discrete times sweep to determine percentage inhibition of cell migration; the anticlonogenic effect was evaluated by colony counting 7 days after treatment and the survival fraction was determined. In addition, cytotoxicity and antiproliferative activity were evaluated by combining the IC50 of EFLt and Dox. Percent migration and colony counts were performed using ImageJ software. Results. The IC50 (950 μg/mL) of EFLt was 56% cytotoxicity, 80,3% inhibition of cell migration, 68% inhibition of colony formation.The ICof Dox was 0,5 μg/mL. Conclusions. EFLt exerts concentration-dependent cytotoxicity and antiproliferative effect on 4T1. Further studies in more complex models are needed to elucidate the anti-tumor potential of EFLt.

Analysis of the Total Level of Flavonoids in the Brown Algae ( Phaeophyceae ) Extract as Analgesic and Anti-Inflammatory Drugs

Abstract Objective: To determine the total level of flavonoids in brown algae extract Padina sp., Sargassum sp., and Turbinaria sp., which could serve as an analgesic and anti-inflammatory drug. Material and Methods: This is an experimental study with a one-shot case study research design. The study sample consisted of three species of brown algae, namely, Padina sp., Sargassum sp., and Turbinaria sp. The study samples were obtained from Saugi Island, Pangkep, Regency. The sampling method used was convenience sampling. The total flavonoid level in the three extracts of brown algae samples was determined at three concentrations (150 ppm, 300 ppm, and 450 ppm) with three replicates. The analysis used a colorimetric method, a spectrophotometer and aluminium chloride as the reagent. Results: The total level of flavonoids in Padina sp. was the highest at 0.894 ± 0.027%, compared to the levels of 0.786 ± 0.075% in Sargassum sp. and 0.745 ± 0.016% in Turbinaria sp. Conclusion: Padina sp. had the highest total flavonoid levels compared to Sargassum sp. and Turbinaria sp. Flavonoid compounds from brown algae have the potential to be used as analgesic and anti-inflammatory drugs.

Inter-population differences in inherited copper tolerance involve photosynthetic adaptation and exclusion mechanisms in Fucus serratus.

• A comparative study of copper (Cu) toxicity and tolerance in three populations of Fucus serratus was conducted by examining Cu2+ effects on various physiological parameters. • Chlorophyll fluorescence, oxygen evolution, copper content, and relative growth rate of embryos and adults were measured on Cu2+ -exposed material. • Algae naturally exposed to elevated total Cu concentration (CuT ), were more Cu2+ resistant than those from clean sites, as indicated by higher embryo and adult growth rates and lower copper contents. The Cu2+ tolerance of F. serratus is at least partly inherited and relies partly on metal exclusion. • There were inhibitory effects of Cu2+ on oxygen exchange rates in both tolerant and non-tolerant algae. By contrast to sensitive algae, the maximum efficiency of photosystem II (Fv /Fm ), maximum fluorescence (Fm ) and zero fluorescence (Fo ) of resistant algae were unaffected by Cu2+ , whereas decreased quantum yield (ΦPSII) and increased nonphotochemical quenching (NPQ) were most pronounced in resistant algae. Inhibitory effects of Cu2+ on ΦPSII may result in the excitation energy being dissipated through xanthophyll-dependent quenching mechanisms in tolerant algae. In nontolerant algae, lower energy dissipation may result in chlorophyll degradation.

Sublethal stress in the intertidal zone: tidal emersion inhibits photosynthesis and retards development in embryos of the brown alga Pelvetia fastigiata.

The effect of tidal emersion on survivorship, photosynthesis and embryonic development was studied in 8 h old zygotes and 7 d old embryos of the intertidal brown alga Pelvetia fastigiata (J. Ag.) DeToni. Zygotes and embryos were outplanted for single low tides in the intertidal zone on the central coast of California (U.S.A.) during June, 1990. Both zygotes and embryos exhibited close to 100% survival when outplanted beneath the canopy of adult P. fastigiata. Embryos (7 d old) also exhibited high survival when outplanted in a red algal turf, the microhabitat where most successful recruitment occurs. However, zygotes (8 h old) experienced high mortality (65-90%) when outplanted in the turf microhabitat. Embryos and zygotes that survived emersion experienced sub-lethal stress that temporarily impaired light-saturated photosynthesis when plants were reimmersed in seawater. The effects of sub-lethal stress were more pronounced in 8 h old zygotes than 7 d embryos, and more severe in the turf microhabitat than beneath the adult Pelvetia canopy. Zygotes outplanted in the red algal turf did not re-establish net photosynthesis until at least 6 h after re-immersion. Photosynthesis was less inhibited in 8 h old zygotes outplanted beneath the adult Pelvetia canopy, and recovered to control (non-emersed) levels within 3 h of re-immersion. Embryos (7 d old) were able to achieve positive net photosynthesis immediately on re-immersion after emersion in the turf or canopy microhabitats. Emersion also retarded the rate of embryonic development in 8 h old zygotes, delaying the formation of primary rhizoids, which help to attach the plant to the substrate. For example, at 19 h post-fertilization, 75% of control (non-emersed) zygotes had developed rhizoids, compared to 3% and 30% for zygotes outplanted in the turf and canopy microhabitats. The different emersion responses of 8 h old zygotes and 7 d old embryos appeared to be related to their ability to tolerate cellular dehydration. Overall, our data suggest that the effects of sub-lethal stresses may have been underestimated in studies of intertidal ecology.

Discrimination between12C and13C by marine plants.

The natural abundance13C/12C ratios (as δ13C) of organic matter of marine macroalgae from Fife and Angus (East Scotland) were measured for comparison with the species' ability to use CO2 and HCO 3- for photosynthesis, as deduced from previously published pH-drift measurements. There was a clear difference in δ13C values for species able or unable to use HCO 3- . Six species of Chlorophyta, 12 species of Phaeophyta and 8 species of Rhodophyta that the pH-drift data suggested could use HCO 3- had δ13C values in the range -8.81‰ to -22.55‰. A further 6 species of Rhodophyta which the pH-drift data suggested could only use CO2 had δ13C values in the range -29.90‰ to-34.51‰. One of these six species (Lomentaria articulata) is intertidal; the other five are subtidal and so have no access to atmospheric CO2 to complicate the analysis. For these species, calculations based on the measured δ13C of the algae, the δ13C of CO2 in seawater, and the known13C/12C discrimination of CO2 diffusion and RUBISCO carboxylation suggest that only 15-21% of the limitation to photosynthesisin situ results from CO2 diffusion from the bulk medium to the plastids; the remaining 79-85% is associated with carboxylation reactions (and, via feedback effects, down-stream processes). This analysis has been extended for one of these five species,Delesseria sanguinea, by incorporating data onin situ specific growth rates, respiratory rates measured in the laboratory, and applying Fick's law of diffusion to calculate a boundary layer thickness of 17-24 µm. This value is reasonable for aDelesseria sanguinea frondin situ. For HCO 3- -using marine macroalgae the range of δ13C values measured can be accommodated by a CO2 efflux from algal cells which range from 0.306 of the gross HCO 3- influx forEnteromorpha intestinalis (δ13C=-8.81‰) in a rockpool to 0.787 forChondrus crispus (δ13C=-22.55‰). The relatively high computed CO2 efflux for those HCO 3- -users with the more negative δ13C values implies a relatively high photon cost of C assimilation; the observed photon costs can be accommodated by assuming coupled, energy-independent inorganic carbon influx and efflux. The observed δ13C values are also interpreted in terms of water movement regimes and obtaining CO2 from the atmosphere. Published δ13C values for freshwater macrophytes were compared with the ability of the species to use CO2 and HCO 3- and again there was an apparent separation in δ13C values for these two groups. δ13C values obtained for marine macroalgae for which no pH-drift data are available permit predictions, as yet untested, as to whether they use predominantly CO2 or HCO 3.

Unusual distribution of floating seaweeds in the East China Sea in the early spring of 2012.

Floating seaweeds play important ecological roles in offshore waters. Recently, large amounts of rafting seaweed have been observed in the East China Sea. In early spring, juveniles of commercially important fish such as yellowtail accompany these seaweed rafts. Because the spatial distributions of seaweed rafts in the spring are poorly understood, research cruises were undertaken to investigate them in 2010, 2011, and 2012. Floating seaweed samples collected from the East China Sea during the three surveys contained only Sargassum horneri. In 2010 and 2011, seaweed rafts were distributed only in the continental shelf and the Kuroshio Front because they had become trapped in the convergence zone of the Kuroshio Front. However, in 2012, seaweed was also distributed in the Kuroshio Current and its outer waters, and massive strandings of seaweed rafts were observed on the northern coast of Taiwan and on Tarama Island in the Ryukyu Archipelago. Environmental data (wind, currents, and sea surface height) were compared among the surveys of 2010, 2011, and 2012. Two factors are speculated to have caused the unusual distribution in 2012. First, a continuous strong north wind produced an Ekman drift current that transported seaweed southwestward to the continental shelf and eventually stranded seaweed rafts on the coast of Taiwan. Second, an anticyclonic eddy covering northeast Taiwan and the Kuroshio Current west of Taiwan generated a geostrophic current that crossed the Kuroshio Current and transported the rafts to the Kuroshio Current and its outer waters. Such unusual seaweed distributions may influence the distribution of fauna accompanying the rafts.