Most tropical evergreen rain forests are characterised by varying degrees of precipitation seasonality that influence plant phenology and litterfall dynamics. Soil microbes are sensitive to soil water:air ratio and to nutrient availability. We studied if within-year seasonality in precipitation and litterfall-derived nutrient input resulted in predictable seasonal variation in soil bacterial diversity/microbial functional groups in an Amazonian forest. We characterised the spatio-temporal dynamics of microbial communities from the plot to the stand scales and related them to precipitation seasonality and spatial variability in soil characteristics. Community composition and functional diversity showed high spatial heterogeneity and was related to variability in soil chemistry at the stand level. Large species turnover characterised plot level changes over time, reflecting precipitation seasonality-related changes in soil nutrient and moisture regimes. The abundance of decomposers was highest during the rainy season, characterised also by anaerobic saprophytes and N2-fixers adapted to fluctuating redox conditions. In contrast, Beijerinckiaceae, likely derived from the phyllosphere, were found at higher abundances when litter inputs and accumulation were highest. We showed that in a mildly seasonal rain forest, the composition of soil microbial communities appears to be following canopy phenology patterns and the two are interlinked and drive soil nutrient availability.

Flávio J. Luizão é pesquisador do Instituto Nacional de Pesquisas da Amazônia e desenvolve pesquisas na área de biogeoquímica e ciclagem de nutrientes. Hillândia Brandão da Cunha é pesquisadora titular do Inpa, desenvolve atividades voltadas para a caracterização hidrobiogeoquímica de ambientes lóticos, lênticos e qualidade das águas superficiais e águas subterrâneas na Amazônia. Carlos Alberto Quesada é pesquisador do Inpa. Desenvolve pesquisas com ciclos biogeoquímicos e interações entre os solos e a dinâmica florestal na Amazônia. José A. Marengo é pesquisador do Centro de Ciência do Sistema Terrestre (CCST), do Instituto Nacional de Pesquisas Espaciais (CCST-Inpe), é membro do IPCC e é membro dos comitês científicos de vários programas internacionais (IAI, IGBP) e nacionais (Painel Brasileiro de Mudanças Climáticas, INCT-Mudanças Climáticas) Alex V. Krusche é professor do Centro de Energia Nuclear na Agricultura, da USP, coordenador da Rede Beija-Rio de pesquisas em rios da Amazônia e do projeto brasileiro do Belmont Forum sobre segurança hídrica.

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Pulse‐type perturbation through excreta by animals creates a mosaic of short‐term high nutrient‐load patches in the soil. How this affects microbial community composition and how long these impacts last are important for microbial community dynamics and nutrient cycling. Our study focused on the short‐term responses to N by bacterial communities and ‘functional groups’ associated with the N cycle in a lowland evergreen tropical rainforest. We applied a single urea pulse, equivalent to urine‐N deposition by medium‐sized mammals to simulate N enrichment and changes in soil N availability, and analysed soil bacterial communities using molecular methods, before and after urea application. Urea addition increased mineral N availability and changed bacterial community composition, from phylum to operational taxonomic unit levels, however, taxon richness and diversity were unaffected. Taxa involved in the physiologically “narrow” processes of nitrification (e.g. Nitrosospira) and denitrification (e.g. Phyllobacteriaceae, Xanthomonadaceae and Comamonadaceae) increased their relative abundance, while N2‐fixers (e.g. Rhodospirillales, and Rhizobiales) decreased after treatment. While a temporal legacy on both community composition and functional group profile was observable 58 and 159 days after treatment, at the latter date bacterial communities were already tending towards pre‐treatment composition. We suggest that pulse‐type perturbation by mammal urine that occurs on a daily basis has strong short‐term effects on patch dynamics of soil microbiota and N availability. Such a spatio‐temporally dynamic soil environment enhances overall microbial richness and diversity, and contributes to the apparent temporal resilience of community composition. A http://onlinelibrary.wiley.com/doi/10.1111/1365-2435.12998/suppinfo is available for this article.

Phycodnaviruses have a significant role in modulating the dynamics of phytoplankton, thereby influencing community structure and succession, nutrient cycles and potentially atmospheric composition because phytoplankton fix about half the carbon dioxide (CO2) on the planet, and some algae release dimethylsulphoniopropionate when lysed by viruses. Despite their ecological importance and widespread distribution, relatively little is known about the evolutionary history, phylogenetic relationships and phylodynamics of the Phycodnaviruses from freshwater environments. Herein we provide novel data on Phycodnaviruses from the largest river system on earth—the Amazon Basin—that were compared with samples from different aquatic systems from several places around the world. Based on phylogenetic inference using DNA polymerase (pol) sequences we show the presence of distinct populations of Phycodnaviridae. Preliminary coarse-grained phylodynamics and phylogeographic inferences revealed a complex dynamics characterized by long-term fluctuations in viral population sizes, with a remarkable worldwide reduction of the effective population around 400 thousand years before the present (KYBP), followed by a recovery near to the present time. Moreover, we present evidence for significant viral gene flow between freshwater environments, but crucially almost none between freshwater and marine environments.

The objective of the study was to evaluate the water quality of Tupé beach and to classify it according to the standards and criteria determined by the Resolution of the National Environment Council nº 274/2000 and 357/2005. Water collections were carried out for five consecutive weeks in two seasonal periods (high and low water), using the technique of multiple tubes and portable equipment. Point one on Tupé beach was classified as unsuitable in the dry season and the other points were classified as suitable for both periods. In general, the physical and chemical parameters were within the standards established by the current environmental resolution. It is worth mentioning the regional characteristics of each study region, such as the acidity of the waters of the Negro river. There was no significant difference between points at Tupé beach, with p = 0.6198.

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RESUMO -O estudo foi conduzido em uma bacia hidrográfica experimental de primeira ordem de aproximadamente 3,5 km 2 localizada próximo ao km 16 da estrada secundária ZF-02, do km 60 da rodovia BR-174 que liga Manaus -Boa Vista. O principal objetivo foi quantificar o balanço dos nutrientes Ca +2 , Mg +2 Na + , K + e NO 3 através da entrada via precipitação e saída via deflúvio. As coletas de água e os cálculos do fluxo de nutrientes foram feitos em base mensal por um período de um ano. Observou-se que as concentrações iônicas apresentaram pouca variação ao longo do tempo. As maiores concentrações na precipitação ocorreram em função do acúmulo de aerosóis na atmosfera, após um período longo sem chuva. Aparentemente a vegetação exerceu influência mais evidente sobre o nitrato em relação aos demais nutrientes. O fluxo dos nutrientes foi variável, onde principalmente a entrada total destes deu-se em função de eventos individuais de chuva de grande magnitude. O balanço em kg.ha -1 .ano -1 foi positivo para todos os nutrientes com os seguintes ganhos líquidos: Ca +2 (2,33); Mg +2 (1,66); Na + (2,07); K + (l,80) e NO 3 (5,84). Palavras-chave: balanço dc nutrientes, bacia hidrográfica, Amazônia Central.Balance of the Nutrients Ca +2 , Mg +2 , Na + , K + e NO 3 on a First Order Catchment Covered with Natural Vegetation in Central Amazonia.ABSTRACT -The study was conducted on a first-order catchment of about 3.5 km 2 located on an experimental site 16 km west of the Manaus -Boa Vista highway, and 60 km north of Manaus. The main purpose was to quantify the balance of the nutrients Ca +2 , Mg +2 Na + , K and NO 3 through the comparison of the values of rainfall input versus streamflow output. Water sampling and nutrient flux determinations were carried out on a monthly basis for a one year period. Ionic concentrations showed low variation along the period. The highest concentrations in the rainfall were related to the accumulation of aerosols in the atmosphere, after a long rainless period. The vegetation exerted, apparently, more influence on nitrate, over the other nutrients. The nutrient flux varied, where their total input was attributed to with the following net gain values: Ca +2 (2,33); Mg +2 (1,66); Na + (2,07); K + (1,80) and NO 3 (5,84).