Numerous studies have documented declines in the abundance of reefbuilding corals over the last several decades and in some but not all cases, phase shifts to dominance by macroalgae have occurred. These assessments, however, often ignore the remainder of the benthos and thus provide limited information on the present-day structure and function of coral reef communities. Here, using an unprecedentedly large dataset collected within the last 10 years across 56 islands spanning five archipelagos in the central Pacific, we examine how benthic reef communities differ in the presence and absence of human populations. Using islands as replicates, we examine whether benthic community structure is associated with human habitation within and among archipelagos and across latitude. While there was no evidence for coral to macroalgal phase shifts across our dataset we did find that the majority of reefs on inhabited islands were dominated by fleshy nonreef-building organisms (turf algae, fleshy macroalgae and non-calcifying invertebrates). By contrast, benthic communities from uninhabited islands were more variable but in general supported more calcifiers and active reef builders (stony corals and crustose coralline algae). Our results suggest that cumulative human impacts across the central Pacific may be causing a reduction in the abundance of reef builders resulting in island scale phase shifts to dominance by fleshy organisms.
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The signatories to this letter commend the JSA for its work on the National Aquaculture Research and Development Strategic Plan and agree with its vision and recognition of aquaculture as a strategic priority for the U.S. However, we suggest that recent aquaculture developments and global trends call for emphasis on a sector of marine aquaculture that is inadequately recognized in this plan. Specifically, we refer to the farming of marine macroalgae or seaweeds.
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The demand in Chile for carrageenophytic algae has increased strongly during the last 3 years, with emphasis on Gigartina skottsbergii, a species representing landings of 32 438 t (wet) during 1996. Various sources of information indicate that this species is being over-exploited and therefore the development of cultivation technologies is needed to support the local carrageenan industry. In this study we summarize currently available information on laboratory, outdoor tank and open sea culture of G. skottsbergii. The results indicate that viable spores of G. skottsbergii can be obtained, mainly during winter, with germination rates of both tetraspores and carpospores, up to 40%. Germlings of G. skottsbergii were succesfully transplanted from the laboratory to outdoor tanks, where they displayed survival values higher than 80% during spring. Experimental trials in the field indicate that G. skottsbergii can be cultivated on rope systems, with tissue fragments used as inoculum. This last result suggests that regeneration from fragments is an alternative method for propagation and massive cultivation of G. skottsbergii in Chile.
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Thermochemical techniques are being operated for the complete conversion of diverse biomasses to biofuels. Among the feedstocks used for thermochemical processes, algae are the promising biomass sources owing to their advantages over other feedstocks such as biomass productivity, renewability and sustainability. Due to several advantages, algal biomass is considered as a source for third generation biofuel. This review work aims to provide a state-of-the-art on the most commonly used thermochemical methods namely torrefaction, pyrolysis, and gasification processes. Furthermore, the production of biofuels from algal biomass was comprehensively articulated. Different algal strains used in thermochemical techniques and their conditions of operation were compared and discussed. The yield and quality of solid (char), liquid (bio-oil) and gaseous (syngas) products obtained through thermochemical methods were reviewed and analysed to understand the efficacy of each technique. End product percentage, quality and advantages of the torrefaction, pyrolysis, and gasification were summarized. It is found that the biofuel produced from the torrefaction process was easy to store and deliver and had higher utilization efficiency. Among the existing thermochemical methods, the pyrolysis process was widely used for the complete conversion of algal biomass to bio-oil or char. This study also revealed that the gasification (supercritical) method was the most energy efficient process for conversion of wet algal biomass. The reactor used in the thermochemical process and its subprocess was also highlighted. This study revealed that the fixed bed reactor was suitable for small scale production whereas the fluidized bed reactor could be scaled up for industrial production. In addition to that environmental impacts of the products were also spotlighted. Finally, the perspectives and challenges of algal biomass to bioenergy conversion were addressed.
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Biofuels from algae are considered as promising alternatives of conventional fossil fuels, as they can eliminate most of the environmental problems. The present study focuses on all the possible avenues of biofuels production through biochemical and thermochemical conversion methods in one place, bringing together both microalgae and macroalgae on the same platform. It provides a brief overview on the mechanism of different biofuel production from algae. Factors affecting the biofuel process and the associated challenges have been highlighted alongwith analysis of techno-economic study available in literature. Undoubtly, biodiesel is the center of attraction among other biofuels. However, their routes and process need to be optimized in order to bring the minimum fuel selling price (MFSP) of biodiesel competitive. Technological challenges have not been overcome to make biofuel production process energetically and commercially viable. Macroalgae are low in lipid content. Therefore, the use of macroalgae is restricted for gaseous fuels or fermentative methods of liquid biofuels production. Anaerobic digestion of algal biomass is easy and seems promising as the process is simple in terms of engineering and infrastructure requirement. Hydrogen production by microalgae through biophotolysis seems interesting as it directly converts the solar energy into hydrogen. However, the process has not been scaled-up till today. Hydrothermal liquefaction (HTL) is more promising due to handling of wet biomass at moderate temperature and pressure and conversion of whole biomass into high quality oil. However, HTL process is energy intensive.
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To reduce greenhouse gas emissions and to prevent their devastative impacts of human health and the environment, bioenergy carriers have been at center of attention to supply global energy demand. Microalgae as solar energy-driven factories could efficiently convert carbon dioxide to a variety of hydrocarbons that can be used as biofuels. With the aim of realizing the current status of algal biofuels, respective patents were surveyed in this chapter using various databases, i.e., World Intellectual Property Organization, United States Patent and Trademark Office, and European Patent Office database. Information derived from the aforementioned databases was categorized into three: upstream, mainstream, and downstream strategies. The upstream strategies included patents on selection of algal strain and genetic engineering approaches while the main- stream strategies reviewed and discussed innovations pertaining to improving algal cultivation systems, production media and nutrients supply, and CO2 supply. Finally, in the downstream strategies section, the inventions aimed at enhancing harvesting and dewatering of microalgae cells and lipid extraction were presented.
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In the coming decades, continued population growth, rising meat and dairy consumption and expanding biofuel use will dramatically increase the pressure on global agriculture. Even as we face these future burdens, there have been scattered reports of yield stagnation in the world’s major cereal crops, including maize, rice and wheat.
Here we study data from B2.5 million census observations across the globe extending over the period 1961–2008. We examined the trends in crop yields for four key global crops: maize, rice, wheat and soybeans. Although yields continue to increase in many areas, we find that across 24–39% of maize-, rice-, wheat- and soybean-growing areas, yields either never improve, stagnate or collapse.
This result underscores the challenge of meeting increasing global agricultural demands. New investments in underperforming regions, as well as strategies to continue increasing yields in the high-performing areas, are required.
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The hazardous effects of current nanoparticle synthesis methods have steered researchers to focus on the development of newer environmentally friendly and green methods for synthesizing nanoparticles using nontoxic chemicals. The development of environmentally friendly methods of nanoparticle synthesis with different sizes and shapes is one of the pressing challenges for the current nanotechnology. Several novel green approaches for the synthesis of AuNPs have been explored using different natural sources, such as plants, algae, bacteria, and fungi. Among organisms, algae and blue–green algae are of particular interest for nanoparticle synthesis. Gold nanoparticles (AuNPs) have a range of applications in medicine, diagnostics, catalysis, and sensors because of their significant key roles in important fields. AuNPs have attracted a significant interest for use in a variety of applications. The widespread use of AuNPs can be accredited to a combination of optical, physical, and chemical properties as well as the miscellany of size, shape, and surface composition that has been adopted through green synthesis methods.
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Concerns about fossil fuels depletion has led to seek for new sources of energy. The use of marine biomass (seaweed) to produce biofuels presents widely recognized advantages over terrestrial biomasses such as higher production ratio, higher photosynthetic efficiency or carbon-neutral emissions. In here, interesting seaweed sources as a whole or as a residue from seaweed processing industries for biofuel production were identified and their diverse composition and availability compiled. In addition, the pretreatments used for seaweed fractionation were thoroughly revised as this step is pivotal in a seaweed biorefinery for integral biomass valorization and for enabling biomass-to-biofuel economic feasibility processes. Traditional and emerging technologies were revised, with particular emphasis on green technologies, relating pretreatment not only with the type of biomass but also with the final target product(s) and yields. Current hurdles of marine biomass-to-biofuel processes were pinpointed and discussed and future perspectives on the development of these processes given.
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With a view to find out the feasibility of culturing G. Edulis in Minicoy lagoon, experiments Have been started since 1989 and encouraging results were obtained, with a maximum Production value of 7.1 fold increase over the initial seed material introduced in the coir ropes Or nets in 60 days time. From these results it can be Inferred that the grazing of the crop by fishes as reported previously was mainly responsible for the low production values In the earlier Instances. Neverthless grazing has been observed during this year also is some of the ropes, but this particular culture rope which escaped the attack by fish and other organisms has given an idea about the real culture potential of the seaweed G. Edulis in Minicoy Lagoon. Hence this clearly suggests that attempts at preventing grazing of the crop by fishes and other organisms must be taken up in future in seaweed farming to derive maximum benefits.
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Marine Agronomy Group, CAFNRM, UH-Hilo
200 W. Kawili st., HI 96720, USA
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Funding for this web portal is provided by the World Wildlife Fund and the University of Hawaii-Hilo.