Potential changes in bacterial metabolism associated with increased water temperature and nutrient inputs in tropical humic lagoons

Temperature and nutrient concentrations regulate aquatic bacterial metabolism. However, few studies have focused on the effect of the interaction between these factors on bacterial processes, and none have been performed in tropical aquatic ecosystems. We analyzed the main and interactive effects of changes in water temperature and N and P concentrations on bacterioplankton production (BP), respiration (BR) and growth efficiency (BGE) in tropical coastal lagoons. We used a factorial design with 3 levels of water temperature (25, 30 and 35 °C) and 4 levels of N and/or P additions (Control, N, P and NP additions) in five tropical humic lagoons. When data for all lagoons were pooled together, a weak interaction was observed between the increase in water temperature and the addition of nutrients. Water temperature alone had the greatest impact on bacterial metabolism by increasing BR, decreasing BP, and decreasing BGE. An increase of 1°C lead to an increase of ~ 4% in BR, a decrease of ~ 0.9% in BP, and a decrease of ~ 4% in BGE. When data were analyzed separately, lagoons responded differently to nutrient additions depending on DOC concentration. Lagoons with lowest DOC concentrations showed the strongest responses to nutrient additions: BP increased in response to N, P and their interaction, BR increased in response to N and the interaction between N and P, and BGE was negatively affected, mainly by the interaction between N and P additions. Lagoons with the highest DOC concentrations showed almost no significant relationship with nutrient additions. Taken together, these results show that different environmental drivers impact bacterial processes at different scales. Changes of bacterial metabolism related to the increase of water temperature are consistent between lagoons, therefore their consequences can be predicted at a regional scale, while the effect of nutrient inputs is specific to different lagoons but seems to be related to the DOC concentration

A IMPORTÂNCIA DAS MACRÓFITAS AQUÁTICAS NO CICLO DO MERCÚRIO NA BACIA DO RIO TAPAJÓS (PA)

Studies about the mercury (Hg) cycle in the Amazon region indicate that deforestation is a main source of Hg to aquatic systems. The atmospheric Hg deposits in soil have a great affinity with Iron (Fe) and Aluminum (Al) oxyhidroxides that are carried to waters by runoff during rainy season. Constituting the fine particulate matter (FPM), Hg is accumulated in aquatic macrophytes roots, a main site of methylmercury (MeHg) production, permitting biomagnification of the neurotoxic MeHg. During wet season, the organic material, humic and fulvic acids and Hg associated to clayed sediments from inundated forest seem to intensify biotic and abiotic Hg methylation. The reducing and acidic conditions may facilitate the bioavailability of the reactive Hg and a higher transference of the produced MeHg is expected as a function of microbial activity and diversity. During the dry season, Hg may return to the atmospheric and terrestrial systems as a consequence of macrophyte decomposition.Os estudos sobre o ciclo do mercúrio (Hg) na região amazônica durante os últimos 20 anos indicam que a atual fonte de contaminação do meio aquático é o desmatamento. O Hg que se deposita no sistema terrestre tem grande afinidade com os oxihidróxidos de Ferro (Fe) e Alumínio (Al), que são carreados por lixiviação durante o período de chuvas. Esses elementos integram o material particulado fino (MPF) e são acumulados em raízes de macrófitas aquáticas, principal local de formação do metilmercúrio (MeHg), composto neurotóxico biomagnificado na cadeia trófica. Durante o período de cheia, a inundação da floresta fornece material orgânico, ácidos húmicos e fúlvicos e Hg junto com sedimentos argilosos, que formam um ambiente favorável à metilação biótica e abiótica do Hg. As condições reduzidas e de pH ácido podem favorecer a biodisponibilidade do Hg e a diversidade e atividade de microrganismos podem intensificar o processo de transferência trófica do MeHg produzido. Durante o período de seca, as macrófitas se decompõem e o Hg, possivelmente, retorna aos sistemas atmosférico e terrestre.

Rarity of monodominance in hyperdiverse Amazonian forests.

Tropical forests are known for their high diversity. Yet, forest patches do occur in the tropics where a single tree species is dominant. Such "monodominant" forests are known from all of the main tropical regions. For Amazonia, we sampled the occurrence of monodominance in a massive, basin-wide database of forest-inventory plots from the Amazon Tree Diversity Network (ATDN). Utilizing a simple defining metric of at least half of the trees ≥ 10 cm diameter belonging to one species, we found only a few occurrences of monodominance in Amazonia, and the phenomenon was not significantly linked to previously hypothesized life history traits such wood density, seed mass, ectomycorrhizal associations, or Rhizobium nodulation. In our analysis, coppicing (the formation of sprouts at the base of the tree or on roots) was the only trait significantly linked to monodominance. While at specific locales coppicing or ectomycorrhizal associations may confer a considerable advantage to a tree species and lead to its monodominance, very few species have these traits. Mining of the ATDN dataset suggests that monodominance is quite rare in Amazonia, and may be linked primarily to edaphic factors

Persistent toxic substances in the Brazilian Amazon: contamination of man and the environment

The organochlorine insecticide DDT was extensively used in Brazil since 1945, both for agricultural purposes and for vector control measures. In 1986 its uses were forbidden in agriculture and in 1997 it was also phased-out in vector controls programs. However, the presence of DDT in urban and forested soils, breast milk and aquatic biota is still common, especially at the Amazon region. The results gathered since the middle of the 90s indicate that environmental contamination with this pesticide is still relatively high. Due to the high fish consumption by traditional riverside populations, human breast milk may represent an important source of DDT exposure to newborns. New results on DDT and PCBs in red dolphin (Inia geoffrensis), an endemic aquatic mammal of the Amazon region, is also reported

A preliminary study of mercury exposure and blood pressure in the Brazilian Amazon

BACKGROUND: Fish is considered protective for coronary heart disease (CHD), but mercury (Hg) intake from fish may counterbalance beneficial effects. Although neurotoxic effects of methylmercury (MeHg) are well established, cardiovascular effects are still debated. The objective of the present study was to evaluate blood pressure in relation to Hg exposure and fish consumption among a non-indigenous fish-eating population in the Brazilian Amazon. METHODS: The study was conducted among 251 persons from six communities along the Tapajós River, a major tributary of the Amazon. Data was obtained for socio-demographic information, fish consumption, height and weight to determine body mass index (BMI), systolic and diastolic blood pressure, and Hg concentration in hair samples. RESULTS: Results showed that overall, systolic and diastolic blood pressure, were relatively low (mean: 113.9 mmHg ± 14.6 and 73.7 mmHg ± 11.0). Blood pressure was significantly associated with hair total Hg (H-Hg), age, BMI and gender. No association was observed between fish consumption and blood pressure, although there were significant inter-community differences. Logistic regression analyses showed that the Odds Ratio (OR) for elevated systolic blood pressure (≥ 130 mmHg) with H-Hg ≥ 10 μg/g was 2.91 [1.26–7.28], taking into account age, BMI, smoking, gender and community. CONCLUSION: The findings of this preliminary study add further support for Hg cardiovascular toxicity

Limited carbon and biodiversity co-benefits for tropical forest mammals and birds

The conservation of tropical forest carbon stocks offers the opportunity to curb climate change by reducing greenhouse gas emissions from deforestation and simultaneously conserve biodiversity. However, there has been considerable debate about the extent to which carbon stock conservation will provide benefits to biodiversity in part because whether forests that contain high carbon density in their aboveground biomass also contain high animal diversity is unknown. Here, we empirically examined medium to large bodied ground-dwelling mammal and bird (hereafter "wildlife") diversity and carbon stock levels within the tropics using camera trap and vegetation data from a pantropical network of sites. Specifically, we tested whether tropical forests that stored more carbon contained higher wildlife species richness, taxonomic diversity, and trait diversity. We found that carbon stocks were not a significant predictor for any of these three measures of diversity, which suggests that benefits for wildlife diversity will not be maximized unless wildlife diversity is explicitly taken into account; prioritizing carbon stocks alone will not necessarily meet biodiversity conservation goals. We recommend conservation planning that considers both objectives because there is the potential for more wildlife diversity and carbon stock conservation to be achieved for the same total budget if both objectives are pursued in tandem rather than independently. Tropical forests with low elevation variability and low tree density supported significantly higher wildlife diversity. These tropical forest characteristics may provide more affordable proxies of wildlife diversity for future multi-objective conservation planning when fine scale data on wildlife are lacking

Sequence-independent characterization of viruses based on the pattern of viral small RNAs produced by the host. [Corrigendum]

published erratum2016 Apr 202016 01 21importedErratum for : Sequence-independent characterization of viruses based on the pattern of viral small RNAs produced by the host. [Nucleic Acids Res. 2015

Unraveling Amazon tree community assembly using Maximum Information Entropy: a quantitative analysis of tropical forest ecology

In a time of rapid global change, the question of what determines patterns in species abundance distribution remains a priority for understanding the complex dynamics of ecosystems. The constrained maximization of information entropy provides a framework for the understanding of such complex systems dynamics by a quantitative analysis of important constraints via predictions using least biased probability distributions. We apply it to over two thousand hectares of Amazonian tree inventories across seven forest types and thirteen functional traits, representing major global axes of plant strategies. Results show that constraints formed by regional relative abundances of genera explain eight times more of local relative abundances than constraints based on directional selection for specific functional traits, although the latter does show clear signals of environmental dependency. These results provide a quantitative insight by inference from large-scale data using cross-disciplinary methods, furthering our understanding of ecological dynamics