An increase in abundance of potentially toxic dinoflagellates in the Santos channel, located in a highly urbanized and eutrophic estuarine complex, was reported in the literature. Prediction of such occurences is essential, but phytoplankton community structure in dynamic estuarine systems are difficult to analyze. In the present work, we attempted to discuss microphytoplanktonic community in relation to physical variables looking for shifts in composition, in time scales of 25 hours. To achieve our goal two surveys were performed on anchored stations during 25 hours (two complete tidal cicles) in the Santos channel, during November 2005 and March/April 2006. Diatom community enhanced in periods of lower current velocity (tide peaks) during dry season, probably due to lower stratification after tidal runs and light availability, while dinoflagellates enhanced after rainfall events, probably due to a higher haline stratification and an increase in dissolved nutrients. The occurrence in high density of Pseudo-nitzschia "seriata" and Prorocentrum minimum reinforces the necessity of a constant monitoring program in the region.
This research evaluated the effect of flooding on the microphytobenthos community structure in a microbial mat from a tropical salt flat. Field samples were collected during four consecutive days: on the first three days the salt flat was dry, on the fourth day it was flooded by rain. In order to evaluate the community maintained in flood conditions, samples from this area were collected and kept in the laboratory for 10 days with sea water. The results of total abundance of microphytobenthos varied from 4.2 × 10 8 to 2.9 × 10 9 organisms L -1 , total density increased one order of magnitude under the effect of water for both situations of precipitation in the salt flat and in experimental conditions, an increase due to the high abundance of Microcoleus spp. Shannon index (H') was higher during the desiccation period. Our data suggest that changes in the abundance of organisms were due to the effect of water. The dominance of the most abundant taxa remained the same under conditions of desiccation and influence of water, and there is probably a consortium of microorganisms in the microbial mat that helps to maintain these dominances.Keywords: microphytobenthos, cyanobacteria, Microcoleus spp., hypersaline environment. Resposta da comunidade de microalgas bentônicas à inundação em uma planície hipersalina tropical ResumoEsse trabalho avaliou os efeitos da inundação na estrutura da comunidade microfitobentônica de um tapete microbiano em uma planície hipersalina tropical. As amostragens foram realizadas no campo durante quatro dias consecutivos: nos três primeiros dias o local estava seco e no quarto dia foi inundando com chuva. Para avaliar a comunidade mantida em condições de inundação, foram coletadas amostras dessa região, sendo mantidas em laboratório por 10 dias com água do mar. Os resultados mostraram que a abundância total do microfitobentos variou de 4.2 × 10 8 a 2.9 × 10 9 organismos L -1 , a densidade aumentou em uma ordem de grandeza com a influência da água, tanto na planície hipersalina como nas condições experimentais, um aumento que foi devido às maiores abundâncias de Microcoleus spp. O índice de Shannon (H') foi mais elevado durante o período de dessecação. Nossos dados sugerem que as mudanças na abundância dos organismos foram devidas ao efeito da água, a dominância dos táxons mais abundantes permaneceu a mesma durante as condições de dessecação e inundação, e possivelmente existe um consórcio entre os microrganismos do tapete microbiano no qual eles ajudam a manter essa dominância.Palavras-chave: microfitobentos, cianobactérias, Microcoleus spp., ambientes hipersalinos.
Natural environments with frequent drainage experience drying and rewetting events that impose fluctuations in water availability and oxygen exposure. These relatively dramatic cycles profoundly impact microbial activity in the environment and subsequent emissions of methane and carbon dioxide. In this study, we mimicked drying and rewetting events by submitting methanogenic communities from strictly anaerobic environments (anaerobic digestors) with different phylogenetic structures to consecutive desiccation events under aerobic (air) and anaerobic (nitrogen) conditions followed by rewetting. We showed that methane production quickly recovered after each rewetting, and surprisingly, no significant difference was observed between the effects of the aerobic or anaerobic desiccation events. There was a slight change in the microbial community structure and a decrease in methane production rates after consecutive drying and rewetting, which can be attributed to a depletion of the pool of available organic matter or the inhibition of the methanogenic communities. These observations indicate that in comparison to the drying and rewetting events or oxygen exposure, the initial phylogenetic structure and the organic matter quantity and quality exhibited a stronger influence on the methanogenic communities and overall microbial community responses. These results change the current paradigm of the sensitivity of strict anaerobic microorganisms to oxygen exposure.
As a result of rapid development in China and the growth of megacities, large amounts of organic wastes are generated within relatively small areas. Part of these wastes can be used to produce biogas, not only to reduce waste-related problems, but also to provide renewable energy, recycle nutrients, and lower greenhouse gases and air polluting emissions. This article is focused on the conditions for biogas solutions in Guangzhou. It is based on a transdisciplinary project that integrates several approaches, for example, literature studies and lab analysis of food waste to estimate the food waste potential, interviews to learn about the socio-technical context and conditions, and life-cycle assessment to investigate the performance of different waste management scenarios involving biogas production. Xiaoguwei Island, with a population of about 250,000 people, was chosen as the area of study. The results show that there are significant food waste potentials on the island, and that all studied scenarios could contribute to a net reduction of greenhouse gas emissions. Several socio-technical barriers were identified, but it is expected that the forthcoming regulatory changes help to overcome some of them.
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