Digital library

  • A critical review of analytical methods used for the chemical characterisation and quantification of phlorotannin compounds in brown seaweeds

    Introduction: Phlorotannins, the phenolic compounds found in brown seaweeds, are a unique and diverse class of compounds showing a huge potential for food and pharmaceutical applications.

    Objective: This review will give an account of the colorimetric assays used and a discussion of their quantitative and qualitative analytical shortcomings. It will also discuss other more complex and modern analytical chemistry methods that are currently being developed to study phlorotannins. The purpose of this review is to increase awareness of these bioactive compounds and promote further development of robust analytical methods for use in biology, food science, pharmacology and biomedical and cosmeceutical sciences.

    Results: Whilst the biological activity and huge commercial potential of the phlorotannins has been widely reported throughout the literature, the chemical structures and reactivity of these compounds is still not well understood. The phlorotannin content of seaweed is usually characterised using colorimetric assays. However, although these methods give a reasonable overall estimation of the total phenolic content, they lack precision and specificity.

    Conclusion: This review highlights the strengths and weaknesses of commonly used colorimetric assays. Novel techniques are highlighted using more selective chemistry to identify this class of compounds.

    Author(s): Pamela J. Walsh, Gary N. Sheldrake, Katerina Theodoridou, Lauren Ford

  • A critical review of biochemical conversion, sustainability and life cycle assessment of algal biofuels

    The increasing global demand of biofuels for energy security and reduction in climate change effects generate the opportunity to explore new biomass sources. Algae is a very promising source of biomass in this context as it sequester a significant quantity of carbon from atmosphere and industrial gases and is also very efficient in utilizing the nutrients from industrial effluents and municipal wastewater. Therefore cultivation of algal biomass provide dual benefit, it provides biomass for the production of biofuels and also save our environment from air and water pollution. The life cycle assessment (LCA) of algal biofuels suggests them to be environmentally better than the fossil fuels but economically it is not yet so attractive.

    Author(s): Stig Irving Olsen, Anoop Singh

  • A Critical Review of the Abilities, Determinants, and Possible Molecular Mechanisms of Seaweed Polysaccharides Antioxidants

     Oxidative stress induces various cardiovascular, neurodegenerative, and cancer diseases, caused by excess reactive oxygen species (ROS). It is attributed to the lack of sufficient antioxidant defense capacity to eliminate unnecessary ROS. Seaweeds are largely cultivated for their edible and commercial purposes. Excessive proliferation of some seaweeds has occurred in coastal areas, causing environmental and economic disasters, and even threating human health. Removing and disposing of the excess seaweeds are costly and labor-intensive with few rewards. Therefore, improving the value of seaweeds utilizes this resource, but also deals with the accumulated biomass in the environment. Seaweed has been demonstrated to be a great source of polysaccharides antioxidants, which are effective in enhancing the antioxidant system in humans and animals. They have been reported to be a healthful method to prevent and/or reduce oxidative damage. Current studies indicate that they have a good potential for treating various diseases. Polysaccharides, the main components in seaweeds, are commonly used as industrial feedstock. They are readily extracted by aqueous and acetone solutions. This study attempts to review the current researches related to seaweed polysaccharides as an antioxidant. We discuss the main categories, their antioxidant abilities, their determinants, and their possible molecular mechanisms of action. This review proposes possible high-value ways to utilize seaweed resources. 

    Author(s): Xian Sun, Zhiwei Liu

  • A decade of change in the seaweed hydrocolloids industry

    Seaweed hydrocolloid markets continue to grow, but instead of the 3–5% achieved in the 1980s and 1990s, the growth rate has fallen to 1–3% per year. This growth has been largely driven by emerging markets in China, Eastern Europe, Brazil, etc. Sales of agar, alginates and carrageenans in the US and Europe are holding up reasonably well in spite of the recession. However, price increases to offset costs in 2008 and 2009 have begun to have a dampening effect on sales, especially in markets where substitution or extension with less expensive ingredients is possible. These higher prices have been driven by higher energy, chemicals and seaweed costs. The higher seaweed costs reflect seaweed shortages, particularly for carrageenan-bearing seaweeds. The Philippines and Indonesia are the dominant producers of the farmed Kappaphycus and Eucheuma species upon which the carrageenan industry depends and both countries are experiencing factors limiting seaweed production. Similar tightening of seaweed supplies are beginning to show up in brown seaweeds used for extracting alginates, and in the red seaweeds for extracting agar. The structure of the industry is also undergoing change. Producers in China are getting stronger, and while they have not yet developed the marketing skills to compete effectively in the developed world markets, they have captured much of their home market. China does not produce the red and brown seaweeds needed for higher end food hydrocolloid produc- tion. Stocking their factories with raw material has led to the supply problems. Sales growth continues to suffer from few new product development successes in recent years; although some health care applications are showing some promise, i.e., carrageenan gel capsules and alginate micro-beads.

    Author(s): Harris J. Bixler, Hans Porse

  • A descriptive chemical analysis of seaweeds, Ulva sp., Saccharina latissima and Ascophyllum nodosum harvested from Danish and Icelandic waters

    This study aimed to discuss the chemical composition of three seaweed species commonly found in Nordic countries and its potential use in feed rations for pigs and calves. Two brown seaweeds Ascophyllum nodosum, Saccharina lastissima and a green seaweed Ulva sp. harvested from Danish and Icelandic waters were analyzed for proximate, amino acids, minerals, fatty acids and non-starch polysaccharides composition. All studied seaweeds contained low protein concentrations (i.e. 11.4–15.9 g/100 g DM). The ratio of essential amino acids (EAA) to non-essential amino acids (NEAA) was similar in all studied seaweeds (0.81−0.87). Ulva sp. had the highest ash concentration (48.2–54.4 g/100 g DM), followed by S. latissima (39.9 g/100 g DM) and A. nodosum (29.5 g/100 g DM). The most abundant macrominerals in the seaweeds were Ca, K and Na. Iodine was the most abundant micromineral in brown seaweeds (1.4–2.1 g/kg DM). Moreover, Ulva sp. had the highest Fe (5.1–8.0 g/kg DM), Mn (10.5 g/kg DM) and inorganic As (0.008 g/kg DM) concentrations. Ascophyllum nodosum had the highest crude fat concentration (3 g/100 g DM) and the highest concentration of polyunsaturated fatty acids (FAs) (37.9 g/100 g FA). Eicosapentaenoic acid (EPA) concentration was the highest in A. nodosum (7 g/100 g FA) followed by S. latissima (5 g/100 g FA) and Ulva sp. (2 g/100 g FA). Furthermore, concentration of α-linolenic acid, a precursor for EPA, was the highest in Ulva sp. (6.2–14.6 g/100 g FA). Total dietary fiber concentration was higher in the brown seaweeds (27.8–42.6 g/100 g DM) compared to the green seaweeds (17.9–21.5 g/100 g DM), where S. latissima had the highest soluble dietary fiber concentration. The high concentrations of ash and fiber may limit inclusion levels of the analyzed whole seaweeds in feed rations, mainly due to dilution of other nutrients in the feed, reduced digestibility of the feed and possible toxicities (i.e. high inorganic As). On the other hand, high concentrations of essential and valuable microminerals including I, Cu, Fe, Mn, Se were also detected in the studied seaweeds. High soluble dietary fiber concentration in S. latissima can be of interest as a fermentable substrate for probiotic bacteria. The easily digestible nutrients including, crude protein and fat were low in the seaweeds. However, the protein, fat, ash and dietary fiber fractions of the studied seaweeds were characterized by high concentrations of EAA, EFA, essential microminerals and interesting monomers of functional polysaccharides, respectively; which indicate possibilities for future use of seaweed-extracts in feed rations.

    Author(s): L. E. Hernandez-Castellano, J.V. Nørgaard, M. Vestergaard, A. Bruhn, J. J. Sloth, J. Sehested, M.R. Weisbjerg, M.E. van der Heide, M.B. Samarasinghe

  • A direct comparison of the performance of the seaweed biofilters, Asparagopsis armata and Ulva rigida

    The tetrasporophyte of Asparagopsis armata has been previously established as a novel seaweed biofilter for integrated land-based mariculture. The species growth and biofiltration rates were much higher than the values described in the literature for Ulva spp., the most common seaweed biofilter. However, a validation of the advantage of one species over the other requires a study of the performances of these two species in the same system at the same time. In this work, we compared the biofiltration performance and biomass yield of A. armata and Ulva rigida cultivated in the effluents of a fish farm in southern Portugal. Comparisons were performed at different water renewal rates and in two seasons of the year. The maximum total ammonia nitrogen (TAN) removal rates were similar for both species in December (2.7 and 2.8 g TAN m–2 day–1 for U. rigida and A. armata, respectively) and higher for A. armata (6.5 g TAN m–2 day–1 ) than for U. rigida (5.1 g TAN m–2 day–1 ) in May. Higher differences were observed when estimating the nitrogen biofiltration through the organic nitrogen yield (N yield) of the biomass produced, particularly in May. This estimate is directly related with the biomass yield and the N content in the tissue which were always higher for A. armata than for U. rigida. In December, the maximum biomass yields were 71 g dry weight (DW) m–2 day–1 for A. armata and 44 g DW m–2 day–1 for U. rigida, while in May, the yield of A. armata was 125 g DW m–2 day–1 and of U. rigida was 73 g DW m–2 day–1 . This study confirmed that A. armata is indeed a more efficient biofilter than U. rigida. To the best of our knowledge, the production rates reported here are the highest ever reported for macroalgae cultivated in tanks.

    Author(s): Leonardo Mata , Andreas Schuenhoff, Rui Santos

  • A FLORISTIC ANALYSIS OF THE MARINE ALGAE AND SEAGRASSES BETWEEN CAPE MENDOCINO, CALIFORNIA AND CAPE BLANCO, OREGON

    The biogeographic area between Cape Mendocino, California and Cape Blanco, Oregon spans over 320 km and is characterized by prominent coastal headlands that act as genetic and species barriers for marine organisms. Because of a lack of a current macroalgal species list for this area, this study aimed to (i) compare patterns of intertidal macroalgal species composition for the poorly described coastline at four sites, and to (ii) compile a macroalgal and seagrass flora based on current findings and historical records. Collections were made in the spring and summers of 2010 and basic ecological habitat attributes for each species were recorded. Similarities in the macroalgal composition across the four sites were investigated using hierarchical clustering based on a presence/absence matrix for each species. A total of 162 species of marine macroalgae (103 Rhodophyta, 33 Heterokontophyta, Phaeophyceae, and 26 Chlorophyta) and 2 species of seagrasses (Anthophyta) were identified. The sites formed a latitudinal gradient of similarity; the two northern sites clustered together as did the two southern sites. Across all four sites, more than half of the taxa were found in the low intertidal. The iv within site comparison of taxa based on zonation revealed that Crescent City differered from the other three sites. One near-endemic species, Cumathamnion sympodophyllum M.J. Wynne & K. Daniels, and one invasive species, Sargassum muticum (Yendo) Fensholt were found. Combined with historical accounts, the macroalgal flora between the Capes consists of 322 macroalgal taxa (201 Rhodophyta, 70 Heterokontophyta, Phaeophyceae, and 51 Chlorophyta) and 4 species of seagrasses. The results indicate a relatively high area of biodiversity of 134 species per degree latitude. The Cheney ratio designation is a cold-temperate flora with closer affinities to Oregon and Washington than to southern California. In comparison to historical records by Dawson and Doty, seven new records were found. Furthermore, Dawson and Doty’s floras list 87 species that were not found, the discrepancy laying either in sampling efficiency or recent range shifts. This study was a first attempt to characterize the marine flora between Cape Mendocino and Cape Blanco and suggests that the capes act as a biogeographic barrier and important transition zone for some species of macroalgae in the Northeast Pacific.  

    Author(s): Simona Augyte

  • A global assessment of offshore mariculture potential from a spatial perspective

     Mariculture accounts for about one-half of total aquaculture production by weight. About one-half of the mariculture production consists of aquatic plants, with the remainder being fish and invertebrates. Nearly all of mariculture is inshore. In contrast, offshore mariculture, which is practised in the open sea with significant exposure to wind and wave action and with equipment and servicing vessels operating in severe sea conditions from time to time, is in its infancy and production is almost exclusively of fish and shellfish. There is an impetus for mariculture to move to the unprotected waters of the open sea. Issues at the local level include competition for space, water quality problems, and a negative public perception of mariculture’s environmental and aesthetic impacts. At the global level, there is concern for food security with expanding population along with the conviction that the potential of the world’s oceans to supplement the food supply is vastly underutilized. Prospecting for suitable locations is a critical part of spatial planning for offshore mariculture’s near-future development. Thus, the objectives of this technical paper are to provide measures of the status and potential for offshore mariculture development from a spatial perspective that are comprehensive of all maritime nations and comparable among them, to identify nations not yet practising mariculture that have a high offshore potential for it, and to stimulate interest in detailed assessments of offshore mariculture potential at national levels.Estimates of offshore mariculture potential are based on key assumptions about its near-future development: offshore mariculture will develop within exclusive economic zones (EEZs), will mainly use culture systems modified from inshore mariculture, and will mainly employ species with already proven culture technologies and established markets. These assumptions set the stage for the identification of analytical criteria. Thus, EEZs were used as spatial frameworks to define the limits of national offshore mariculture development. Potential was defined by the depth and current speed limits on offshore cages and longlines, the cost-effective area for offshore mariculture development, and the favourable conditions for grow-out of representative species: cobia (Rachycentron canadum), Atlantic salmon (Salmo salar) and blue mussel (Mytilus edulis), and integrated multitrophic aquaculture (IMTA) of the last two species. Verification and comparison with existing mariculture showed that, despite the limitations of the data, the results are indicative of offshore mariculture potential within the specified criteria.Offshore mariculture potential is large. At present, 44 percent of maritime nations with 0.3 million kilometres of coastline are not yet practising mariculture. About half of the mariculture nations have outputs of less than 1 tonne/kilometre of coastline. About one-half of inshore mariculture production consists of aquatic plants, but there is little production of plants offshore. Scenarios using 5 and 1 percent of the area meeting all of the criteria for each of the three species showed that development of relatively small offshore areas could substantially increase overall mariculture production. Improvements in culture technologies allowing for greater depths and increased autonomies, as well as the further development of free-floating or propelled offshore installations, would add greatly to the area with potential for offshore mariculture development. Remote sensing for the sustainable development of offshore mariculture is included as Annex 3 to this publication in recognition of the importance of remote sensing as a source of data for spatial analyses to assess potential for offshore mariculture, and also for zoning and site selection as well as for operational remote sensing to aid mariculture management.

    Author(s): James McDaid Kapetsky, José Aguilar-Manjarrez, Jeff Jenness

  • A Green Algae Mixture of Scenedesmus and Schroederiella Attenuates Obesity-Linked Metabolic Syndrome in Rats

    This study investigated the responses to a green algae mixture of Scenedesmus dimorphus and Schroederiella apiculata (SC) containing protein (46.1% of dry algae), insoluble fibre (19.6% of dry algae), minerals (3.7% of dry algae) and omega-3 fatty acids (2.8% of dry algae) as a dietary intervention in a high carbohydrate, high fat diet-induced metabolic syndrome model in four groups of male Wistar rats. Two groups were fed with a corn starch diet containing 68% carbohydrates as polysaccharides, while the other two groups were fed a diet high in simple carbohydrates (fructose and sucrose in food, 25% fructose in drinking water, total 68%) and fats (saturated and trans fats from beef tallow, total 24%). High carbohydrate, high fat-fed rats showed visceral obesity with hypertension, insulin resistance, cardiovascular remodelling, and nonalcoholic fatty liver disease. SC supplementation (5% of food) lowered total body and abdominal fat mass, increased lean mass, and attenuated hypertension, impaired glucose and insulin tolerance, endothelial dysfunction, infiltration of inflammatory cells into heart and liver, fibrosis, increased cardiac stiffness, and nonalcoholic fatty liver disease in the high carbohydrate, high fat diet-fed rats. This study suggests that the insoluble fibre or protein in SC helps reverse diet-induced metabolic syndrome.

    Author(s): Senthil Arun Kumar, Marie Magnusson, Leigh C. Ward, Nicholas A. Paul, Lindsay Brown

  • A guide to phylotranscriptomic analysis for phycologists

    Phylotranscriptomics is the study of phylogenetic relationships among taxa based on their DNA sequences derived from transcriptomes. Because of the relatively low cost of transcriptome sequencing compared with genome sequencing and the fact that phylotranscriptomics is almost as reliable as phylogenomics, the phylotranscriptomic analysis has recently emerged as the preferred method for studying evolutionary biology. However, it is challenging to perform transcriptomic and phylogenetic analyses together without programming expertise. This study presents a protocol for phylotranscriptomic analysis to aid marine biologists unfamiliar with UNIX command-line interface and bioinformatics tools. Here, we used transcriptomes to reconstruct a molecular phylogeny of dinoflagellate protists, a diverse and globally abundant group of marine plankton organisms whose large and complex genomic sequences have impeded conventional phylogenic analysis based on genomic data. We hope that our proposed protocol may serve as practical and helpful information for the training and education of novice phycologists.

    Author(s): Seongmin Cheon, Sung-Gwon Lee, Hyun-Hee Hong, Hyun-Gwan Lee, Kwang Young Kim, Chungoo Park

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