Digital library

  • A Community Approach Removing Invasive Algae to Restore Native Ecosystems

    While the diversity and beauty of plants on land are easily seen by us, we may often overlook their aquatic counterparts hidden beneath the sea. Algae, photosynthetic plants ranging from microscopic phytoplankton to larger seaweeds, live in fresh and seawater and fulfill a variety of important functions, including the production of oxygen and the provision of habitat and food. Although limu, various species of seaweed native to Hawai‘i, are an integral part of the environment, the rapid spread of invasive algae over recent decades has raised concern for the future health of limu and their ecosystems.

    Originally, multiple species of invasive algae were purposely brought to Hawaiʻi for commercial aquaculture projects, while others were introduced unintentionally over time by ship fouling. Many of these alien species flourish in high-runof environments characterized by excessive nutrient concentrations and sedimentation. As invasive alien algae (IAA) spread, they cause a cascade of ecological and economic damage. Research has recognized IAA as particularly problematic for Hawaiian reefs as they smother coral reefs and native algal communities, permanently altering natural habitats and reducing biodiversity. Two areas particularly hard hit on Oʻahu were Kāneʻohe Bay and Maunalua Bay.

    Author(s): Paula Moehlenkamp

  • A comparative assessment of microwave assisted (MAE) and conventional solid-liquid (SLE) techniques for the extraction of phloroglucinol from brown seaweed

    Brown seaweeds are rich in polyphenols with a basic building block of 1,3,5-trihydroxybenzene (phloroglucinol) and were investigated as a bioresource for the extraction of polyphenols for biopolymers and bioproducts. Spe- cies of seaweed with high contents of polyphenols were identified through meta-analysis and selected for the comparative assessment of the extraction efficiency of polyphenols using microwave assisted (MAE) vs. conven- tional solid-liquid (SLE) extraction. Out of ten species from Australia and New Zealand screened by SLE, Carpophyllum flexuosum (8.6%) and C. plumosum (7.5%) had the highest contents of polyphenols and were select- ed for MAE along with commercially available Ecklonia radiata. C. flexuosum was identified as the key species for extraction of polyphenols, with a 70% increase in yield using optimized MAE (aqueous, biomass:solvent ratio 1:30, 160 °C, 3 min) compared to SLE. The cell-wall bound fraction of polyphenols in brown seaweed may be larg- er than previously thought and is accessible through MAE.

    Author(s): Marie Magnusson, Alexander K.L. Yuen, Rui Zhang, Jeffrey T. Wright, Richard B. Taylor , Thomas Maschmeyer, Rocky de Nys

  • A comparative assessment of the activity and structure of phlorotannins from the brown seaweed Carpophyllum flexuosum

    The extraction and antioxidant activity of phlorotannins from the brown seaweeds Carpophyllum flexuosum, Carpophyllum plumosum and Ecklonia radiata was investigated to identify an optimised extraction process for novel anti-oxidant extracts. Subsequently, the composition of the most active phlorotannin extracts was de- termined. Microwave assisted extraction (MAE) using water was the most efficient extraction process with shorter processing times and a higher purity product than obtained with any of the other methods tested. MAE resulted in the fast, effective decomposition of the cellular structure, as identified through scanning electron microscopy (SEM), and this related directly to the efficiency of extraction. Phlorotannins extracted from C. flexuosum by MAE had the strongest antioxidant activity (62.1 mg gallic acid equivalents (GAE)/g dw of sea- weed) and more than 5.5-fold greater 2, 2-diphenyl-1-picrylhydrazyl (DPPH) radical scavenging ability than ascorbic acid after 7-day incubation periods at 30 °C and at 60 °C. Six major chemical species of phlorotannin, belonging to the fuhalol group, were identified within the MAE extract using NMR and HPLC-MS. The results confirm phlorotannins from C. flexuosum to be promising natural, bio-derived and bio-compatible antioxidants, while identifying the most effective method to extract the constituents and retain antioxidant activity.

    Author(s): Rui Zhang, Alexander K.L. Yuen, Marie Magnusson, Jeffrey T. Wright, Rocky de Nys, Anthony F. Masters, Thomas Maschmeyer

  • A Comparative Study of the Yield and Physical Properties of Agar-agar from Different Blends of Seaweeds

    The agar agar obtained from Gracilaria verrucosa growing in commercial quantities in Chilka Lake, Orissa was found to be having an yield of 23% and gel strength of 41 gm/cm . In order to exploit this agarophyte for the same with other agarophytes like Gelidlella acerosa and Gracilaria edulis in three different proportions was studied.

    Author(s): Chennubhotla, V S Krishnamurthy, Najmuddin, M, Nayak, Bidyadhar

  • A comparison of physiological responses between attached and pelagic populations of Sargassum horneri under nutrient and light limitation

    Large-scale Sargassum blooms have been increasingly observed in coastal zones in recent years. Sargassum horneri (Turner) C. Agardh blooms (pelagic) have been observed in Jeju Island (Korea) and the southwest of the Korean Peninsula, causing serious problems for seaweed and abalone farms as well as for fisheries, tourism and recreational industries. The present study explored the physiological responses of attached and pelagic S. horneri populations cultivated under different nutrient concentrations (HN: 50 μM of nitrogen and 5 μM of phosphorus; LN: 5 μM of nitrogen and 0.5 μM of phosphorus) and photosynthetically active radiation (PAR) (H-PAR: 250; MPAR: 150; L-PAR: 50 μmol photons m− 2 s − 1 ) for 25 days. Relative growth rates (RGR) were significantly lower in the pelagic population than that in the attached population. All thalli from the pelagic population died within 20 days. Chlorophyll a and c, and carotenoids were significantly higher at HN than at LN, and decreased as PAR increased for both populations. For the attached population, photosynthetic rate, tissue nitrogen, and carbon and nitrogen removal were also significantly higher at HN than at LN. These results suggest that high nutrient and lower PAR increased the biomass accumulation of attached populations in coastal areas. Nutrient limitation and high PAR may accelerate senescence of the pelagic populations while traveling on the sea surface from their point of origin.

    Author(s): Menglin Bao, Ji-Sook Park, Hailong Wu, Hyuk Je Lee, Sang Rul Park, Tae-Hoon Kim, Young Baek Son, Tae Hee Lee, Charles Yarish, Jang K. Kim

  • A comparison of two rearing sites of the giant kelp Macrocystis integrifolia in Sitka Sound, Alaska

    In order to test the suitability of a site for the rearing of Macrocystis integrifolia. ten sporophytes were transplanted from a wild patch at Whiting Harbor. Sitka. Alaska. to a site located behind the Sheldon Jackson College salmon hatchery in Sitka. Growth and survival were compared at the locations from April 4 to May 28. 1987. Growth at Whiting Harbor was significantly greater than growth at Sheldon Jackson College (SJC). A freshwater lens at the SJC site is thought to have impaired growth of the upper blades on the plants. For this reason the SJC site is not suitable for M. integrifolia. 

    Attempts were made to artificially culture M. integrifolia at the SJC facility. Culturing from spore release through gametophyte stages to maturation and zygote fertilization was successful. However. culturing of the new sporophytes was not successful.

    Author(s): Samuel H. Rabung

  • A comprehensive insight from microalgae production process to characterization of biofuel for the sustainable energy

    The present article reviews about the algae isolation, microalgae growth, types of cultivation, oil extraction, biodiesel characterization and the advantage of microalgae biomass and its other applications. A detailed review was undertaken on various microalgae harvesting methods, types of oil extraction and biodiesel production. The merits and demerits of open pond systems and photo-bioreactors cultivation are discussed briefly. The various microalgae species and its lipids used for biodiesel production were presented and compared with conventional feedstocks. This article also discusses the key process parameter for in-situ transesterification for biodiesel production such as molar ratio, stirring rate, moisture, reaction time, catalyst type and temperature. The fundamental characterization of the biodiesel and physiochemical properties such as flash point, cetane number, density, kinematic viscosity, pour and cloud point and calorific value were studied and compared with the results of conventional diesel. This study reports that oil from microalgae can be a suitable alternative than edible oils due to ease of growth, separation, and high lipid content. The properties of microalgae biodiesel meet ASTM standards. Overall, algae are not only a potential source for biofuel but can also be used in wastewater treatment, food additives, carbon sequestration, heath care, cancer treatment and aquaculture all of which are discussed in this review.

    Author(s): C.N. Kowthaman, P. Senthil Kumar, V. Arul Mozhi Selvan, D. Ganesh The present article reviews about the algae isolation, microalgae growth, types of cultivation, oil extraction, biodiesel characterization and the advantage of microalgae biomass and its other applications. A detailed review was undertaken on va

  • A comprehensive review on the factors affecting thermochemical conversion efficiency of algal biomass to energy

    Algae are one of the most viable feedstock options that can be converted into different bioenergies viz., bioethanol, biobutanol, biodiesel, biomethane, biohydrogen, etc. owing to their renewable, sustainable and economic credibility features. Algal biomass to fuel biorefining process is generally classified into three categories as chemical, biochemical and thermochemical methods. The present article aims to provide a state-of-the-art review on the factors affecting the thermochemical conversion process of algal biomass to bioenergy. Further, reaction conditions of each techniques (torrefaction, pyrolysis, gasification and hydrothermal process) influence biochar, bio-oil and syngas yield were discussed. Reaction parameters or factors such as reactor temperature, residence time, pressure, biomass load/feedstock composition, catalyst addition and carrier gas flow affecting process efficiency in terms of product yield and quality were spotlighted and extensively discussed with copious literature. It also presents the novel insights on production of solid (char), liquid (bio-oil) and gaseous (syngas) biofuel through torrefaction, pyrolysis and gasification, respectively. It is found that the energy intensive drying was more efficient mode involved in thermochemical process for wet algal biomass. However other modes of thermochemical process were having unique feature on improving the product yield and quality. Among the various factors, reaction temperature and residence time were relatively more important factors which affected the process efficiency. The other factors signposted in this review will lay a roadmap to researchers to choose an optimal thermochemical conditions for high quality end product. Lastly, the perspectives and challenges in thermochemical conversion algae biomass to biofuels were also discussed.

    Author(s): Arivalagan Pugazhendhi, Thangavel Mathimani, Chandramohan V.P., Pritam Das

  • A Conceptual Framework for Marine Agronomy

    Between the late 1960s and the early 1980s, several generations of phycologists in Hawaii and the Philippines, associated with M. S. Doty, contributed to developing a new approach, and to advance concepts in marine agronomy. This study reviews the approach and the main concepts contributed. Integrating these contributions with others, a basic conceptual framework for marine agronomy is presented.

    Author(s): B. Santelices

  • A continuous-flow and on-site mesocosm for ocean acidification experiments on benthic organisms

    Mesocosm experiments conducted for ecological purposes have become increasingly popular because they can provide a holistic understanding of the biological complexities associated with natural systems. This paper describes a new outdoor mesocosm designed for CO2 perturbation experiments of benthos. Manipulated the carbonate chemistry in a continuous flow-through system can be parallelized with diurnal changes, while irradiance, temperature, and nutrients can vary according to the local environment. A target hydrogen ion activity (pH) of seawater was sufficiently stabilized and maintained within 4 h after dilution, which was initiated by the ratio of CO2-saturated seawater to ambient seawater. Specifically, pH and CO2 partial pressure (pCO2) levels gradually varied from 8.05–7.28 and 375–2,691 μatm, respectively, over a range of dilution ratios. This mesocosm can successfully manipulate the pH and pCO2 of seawater, and it demonstrates suitability for ocean acidification experiments on benthic communities.

    Author(s): Ju-Hyoung Kim , Eun Ju Kang, Keunyong Kim, Kwang Young Kim

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