Responses of marine benthic microalgae to elevated CO<inf>2</inf>

Increasing anthropogenic CO2 emissions to the atmosphere are causing a rise in pCO2 concentrations in the ocean surface and lowering pH. To predict the effects of these changes, we need to improve our understanding of the responses of marine primary producers since these drive biogeochemical cycles and profoundly affect the structure and function of benthic habitats. The effects of increasing CO2 levels on the colonisation of artificial substrata by microalgal assemblages (periphyton) were examined across a CO2 gradient off the volcanic island of Vulcano (NE Sicily). We show that periphyton communities altered significantly as CO2 concentrations increased. CO2 enrichment caused significant increases in chlorophyll a concentrations and in diatom abundance although we did not detect any changes in cyanobacteria. SEM analysis revealed major shifts in diatom assemblage composition as CO2 levels increased. The responses of benthic microalgae to rising anthropogenic CO2 emissions are likely to have significant ecological ramifications for coastal systems. © 2011 Springer-Verlag

Valorisation to biogas of macroalgal waste streams: a circular approach to bioproducts and bioenergy in Ireland

© 2016 The Author(s) Seaweeds (macroalgae) have been recently attracting more and more interest as a third generation feedstock for bioenergy and biofuels. However, several barriers impede the deployment of competitive seaweed-based energy. The high cost associated to seaweed farming and harvesting, as well as their seasonal availability and biochemical composition currently make macroalgae exploitation too expensive for energy production only. Recent studies have indicated a possible solution to aforementioned challenges may lay in seaweed integrated biorefinery, in which a bioenergy and/or biofuel production step ends an extractions cascade of high-value bioproducts. This results in the double benefit of producing renewable energy while adopting a zero waste approach, as fostered by recent EU societal challenges within the context of the Circular Economy development. This study investigates the biogas potential of residues from six indigenous Irish seaweed species while discussing related issues experienced during fermentation. It was found that Laminaria and Fucus spp. are the most promising seaweed species for biogas production following biorefinery extractions producing 187–195 mL CH4 gVS−1 and about 100 mL CH4 gVS−1 , respectively, exhibiting overall actual yields close to raw un-extracted seaweed

New DNA sequences from bacteria converting phenol into acetate under strict anaerobic conditions

This work reports new fragments of DNA sequences related to microbes able to degrade phenol into acetate under strict anaerobic conditions. For this purpose, anaerobic digesting sludge was acclimatised to degrade phenol, then heat treated and in turn used as fermentative sludge. The resulting microbial community was able to convert phenol into acetate under anaerobic conditions (kinetic constants: 0.396 ± 0.01 and 0.345 ± 0.04 mg of compound L -1 day-1 and molecular analyses revealed that only bacteria were present in the final sludge and thus methanogens were eliminated. The bacteria were mainly Gram-negative sporeforming rods, belonging to the Deltaproteobacteria class and had a tendency for aggregation. These are also phenotypically related to organisms thriving at extreme environments. Cloning, temperature gradient gel electrophoresis (TGGE) and probe matching of a short 16S DNA fragment revealed that these new microbes are evolutionary related to, and share 90% of similarities with, Desulfovibrio sp

Drama as a mediator

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Comparison between a two-stage and single-stage digesters when treating a synthetic wastewater contaminated with phenol

Phenol is a pollutant found in many industrial wastewaters, which diminishes biogas formation in anaerobic digesters. In this study, a two-stage (acidogenic and methanogenic) anaerobic digester (TSAD) was compared to a single stage digester (SSD), in treating a synthetic wastewater contaminated with phenol. Both systems were operated in batch-dilution and semi-continuously at 35°C, and were loaded with a synthetic wastewater containing a constant concentration of readily biodegradable organic matter and an increasing concentration of phenol. The TSAD had greater biogas production, and its acidogenic reactor fermented the readily biodegradable matter without inhibition by accumulation of phenol (up to 1 450 mg∙ℓ-1). The acidogenic reactor also prevented inhibition of biogas formation in the second phase (methanogenic), by holding phenol and fast produced organic acids. Batch TSAD is a potential wastewater treatment option to decontaminate streams containing readily biodegradable matter contaminated with phenol. This system enhances biogas production and allows better control of the acidogenic and methanogenic phases.(undefined