Carolina Joana da Silva

Cyanobacteria enhance methylmercury production: A hypothesis tested in the periphyton of two lakes in the Pantanal floodplain, Brazil

The toxic potential of mercury (Hg) in aquatic systems is due to the presence and production of methylmercury (MeHg). Recent studies in tropical floodplain environments showed that periphyton associated with the roots of aquatic macrophytes produce MeHg. Periphyton communities are the first link in the food chain and one of the main MeHg sources in aquatic environments. The aim of this work was to test the hypotheses that the algal community structure affects potential methylation, and ecologically distinct communities with different algal and bacterial densities directly affect the formation of MeHg in the roots of macrophytes. To evaluate these, net MeHg production in the roots of Eichhornia crassipes in relation to the taxonomic structure of associated periphytic algae was evaluated. Macrophyte root samples were collected in the dry and flood season from two floodplain lakes in the Pantanal (Brazil). These lakes have different ecological conditions as a function of their lateral hydrological connectivity with the Paraguay River that is different during times of drought. Results indicated that MeHg production was higher in the flood season than in the dry season. MeHg production rates were higher in the disconnected lake in comparison to the connected lake during the dry season. MeHg production exhibited a strong positive co-variation with cyanobacteria abundance (R(2)=0.78; p<0.0001 in dry; R(2)=0.40; p=0.029 in flood) and with total algal biomass (R(2)=0.86; p<0.0001), and a negative co-variation with Zygnemaphyceae (R(2)=0.50; p=0.0018) in the lake community in dry season. This indicates that ecological conditions that favour the establishment and development of cyanobacteria are associated with higher rates of methylation in aquatic systems. This suggests that cyanobacteria could be a proxy for sites of MeHg production in some natural aquatic environments.

Conhecimento ecológico tradicional sobre plantas cultivadas pelos pescadores da comunidade Estirão Comprido, Pantanal matogrossense, Brasil

Ethnoecological study dealing with Traditional Ecological Knowledge (TEK) on plants cultivated by fishermen at Community Estirao Comprido, Cuiaba River, Barao de Melgaco, Pantanal matogrossense, Brazil. Twenty two fishermen were interviewed to elaborate a free list on the plants. The list was analyzed through: Smiths salience index, cultural consensus analysis, similarity and dissimilarity with multidimensional scaling, and stacking technique. The software ANTHROPAC 4.0 was used for the data statistical treatment. Based on the Smiths salience index, we identified six ruptures in the cultural domain of cultivated plants, concentrating on 116 ethnospecies. Orange and maize were most frequently cited and ranked first in the free list; they are in the first rupture of the free list with Smith index of 0.728 and 0.711, respectively. The cultural consensus analysis indicated that TEK on cultivated plants characterizes a consensus and concentrates on 18 ethnospecies. Stacking analysis evidenced that knowledge on plants is related to their different usage types. In this context, the usage and management possibilities emphasized in the present study can contribute to the development of public polices for conserving the ecological and cultural biodiversity.

Waterscape determinants of net mercury methylation in a tropical wetland.

The periphyton associated with freshwater macrophyte roots is the main site of Hg methylation in different wetland environments in the world. The aim of this study was to test the use of connectivity metrics of water bodies, in the context of patches, in a tropical waterscape wetland (Guapore River, Amazonia, Brazil) as a predictor of potential net methylmercury (MeHg) production by periphyton communities. We sampled 15 lakes with different patterns of lateral connectivity with the main river channel, performing net mercury methylation potential tests in incubations with local water and Eichhornia crassipes root-periphyton samples, using (203)HgCl2 as a tracer. Physico-chemical variables, landscape data (morphological characteristics, land use, and lateral connection type of water bodies) using GIS resources and field data were analyzed with Generalized Additive Models (GAM). The net Me(203)Hg production (as % of total added (203)Hg) was expressive (6.2-25.6%) showing that periphyton is an important matrix in MeHg production. The model that best explained the variation in the net Me(203)Hg production (76%) was built by the variables: connection type, total phosphorus and dissolved organic carbon (DOC) in water (AICc=48.324, p=0.001). Connection type factor was the best factor to model fit (r(2)=0.32; p=0.008) and temporarily connected lakes had higher rates of net mercury methylation. Both DOC and total phosphorus showed positive significant covariation with the net methylation rates (r(2)=0.26; p=0.008 and r(2)=0.21; p=0.012 respectively). Our study suggests a strong relationship between rates of net MeHg production in this tropical area and the type of water body and its hydrological connectivity within the waterscape.

From Rainforests to Drylands: Comparing Family Farmers’ Perceptions of Climate Change in Three Brazilian Biomes

Risk perceptions influence individual and collective adaptive responses to climate hazards. Up to now, the majority of literature addressing climate change perception and adaptation has been location-specific. Such an approach is limited with respect to the construction of a generalized theory around why and how people perceive and act towards climate change risks. This chapter seeks to contribute to overcome this limitation by offering a cross-sectional study of climate change risks perceptions among smallholder farmers settled in three contrasting biomes in Brazil: the Amazon (rainforest); the Caatinga (semi-arid); and the Cerrado (savanna). By articulating regional, local and micro scales of comparison, common traits in the perception of climate variability are identified. It is not intended, at this stage, to validate particular theories of climate change, but rather to contribute to a better understanding of climate change as a trans-regional and socially embedded environmental phenomenon. This study shows that, in spite of existing perceptive barriers, smallholders settled in dramatically different contexts share perceptions about risks linked to the following phenomena: (i) changes in the timing of seasons, (ii) decrease in rainfall levels; (iii) temperature rises. Moreover, there are specific adaptation strategies to climate change, like the timing of seeding, which appear to be addressed independently by smallholders of the three biomes. Public policies intended to support adaptive measures and the increase of food security must take subjective risk perception into account within the cultural and environmental contexts of the actors involved.

Non-lethal sampling for mercury evaluation in crocodilians.

Mercury (Hg) is a ubiquitous environmental contaminant that poses potential threats to ecosystems due to its toxicity to humans and wildlife. The development of non-lethal sampling techniques is a critical step for evaluation of Hg in threatened species in tropical floodplain environments, where most of Hg found is the result of land use and gold mining activities, and more methylation sites are available. We evaluated the spatial and seasonal effectiveness of caudal scutes and claws to estimate Hg bioaccumulation in crocodilians (Caiman yacare), in the scarcely documented Pantanal. Hence, we investigated the potential for Hg bioaccumulation in top predators according to its proximity to mining sites, and in water bodies with different hydrological characteristics and connectivity with the main river during two phases of the flood pulse (dry and flood). The highest Hg concentrations were detected in caimans captured close to mining activities, in claws (2176 ng g(-1) ww) and caudal scutes (388 ng g(-1) ww). THg concentration in claws was related to the flood season and its mean concentration was thirteen fold higher than Hg concentration in scutes during whole year. Both tissues were found to be effective as non-lethal sampling techniques for measuring Hg bioaccumulation in reptiles over time. Nevertheless, claw tissue seems to have a more consistent result, since its constitutional chemical characteristics makes it a better indicator of spatial patterns that influence on Hg exposure.

Efeito da inundação lateral sobre a distribuição da vegetação ripária em um trecho do rio Cuiabá, MT

Hydrological and phytosociological studies were conducted in a 550 m topographic profile installed perpendicularly to the Cuiaba River, in the municipality of Rosario Oeste, MT, Brazil, in order to analyze the influence of flooding on riparian vegetation distribution. A backwater hydrological model under a subcritical regime was fitted allowing the establishment of a hydrological series in the study area. From this series, the recurrence intervals for the area were obtained. The results suggested that the banks of the main channel, the secondary channel and its lateral dike, the flood plain, and the terrace are flooded at every ∼1 - 1.7 years, ∼1.77 - 2.8 years, ∼3 years, and from ∼3.25 to ∼39 years, respectively. The species Combretum leprosum Mart. (Combretaceae) presented the greatest VI in the bank of the main channel; Callisthene fasciculata (Spr.) Mart. (Vochysiaceae) presented the greatest VI in the bank of the main channel and in the terrace; and Licania parvifolia Huber (Chrysobalanaceae), Cariniana estrellensis (Raddi) Kuntze. (Lecythidaceae), and Vochysia divergens Pohl. (Vochysiaceae) in the flood plain. The results indicated that flooding frequency and especially the flooding time are the main determinative ecological factors of plant species distribution along the topographic profile.

Seasonal changes in peryphytic microbial metabolism determining mercury methylation in a tropical wetland

Mercury (Hg) methylation, a key process in the biogeochemical cycle of Hg, is mainly attributed to sulfate-reducing bacteria and methanogenic Archaea. However, environmental regulation by these groups has not yet been ascertained in tropical environments, especially in respect to the seasonal flood flooding. This work evaluated the variation of net methylmercury production potential in relation to biological characteristics of the periphyton, environmental factors, and flood pulse seasons. Our results indicate that there is a seasonal change between metabolic groups as main Hg methylators, sulfate-reducing bacteria in the dry season and methanogenic Archaea in the flood season. In addition, there was a positive relationship between dissolved organic carbon (DOC), phosphorus, cyanobacteria biovolume, and periphytic Hg methylation potential. These results shed a new light on MeHg production plasticity, mediated by landscape and flood pulses in tropical wetlands, as well as on ecological relationships within the periphyton.

Conhecimento ecológico tradicional da ictiofauna pelos quilombolas no Alto Guaporé, Mato Grosso, Amazônia meridional, Brasil

The objective of this research was to study the traditional ecological knowledge (TEK) related to fishing among the ethnic group self-identified as quilombola people, and it included analysis of factors influencing the cultural consensus and techniques used in artisanal fishing. Twenty-four men and seven women from the Retiro, Boqueirão, Casalvasco and Manga quilombo communities participated. Sampling methods included snowball, free listing, and participant observation. The results include a list of 47 ethnospecies (46 fish and one reptile). The cultural consensus is composed of: Hoplias malabaricus, Cichla sp., Pseudoplatystoma fasciatum, Astronotus ocellatus, Satanoperca pappaterra, Brycon cephalus, Piaractus mesopotamicus, P. corruscans, Pimelodus sp., Colossoma macropomum, Pygocentrus nattereri, Mylossoma aureum, Astyanax sp., and Leporinus freiderici. While the wealth of knowledge tended to be greater among people who resided temporarily in other Brazilian states, this was not related to the age of the interviewees. The maintenance and transmission of TEK stems from daily contact with fish and the river, from childhood on, as well as observation of group fishing practices. TEK is part of their identity and represents a valuable cultural heritage. Participation by these social actors in decision-making and management plans for protected areas is necessary.

Rivers shape population genetic structure in Mauritia flexuosa (Arecaceae)

Abstract The Mauritia flexuosa L.f. palm is known as the “tree of life” given its importance as fundamental food and construction resources for humans. The species is broadly distributed in wet habitats of Amazonia and dry habitats of the Amazon and Orinoco river basins and in the Cerrado savanna. We collected 179 individuals from eight different localities throughout these habitats and used microsatellites to characterize their population structure and patterns of gene flow. Overall, we found high genetic variation, except in one savanna locality. Gene flow between populations is largely congruent with river basins and the direction of water flow within and among them, suggesting their importance for seed dispersal. Further, rivers have had a higher frequency of human settlements than forested sites, contributing to population diversity and structure through increased human use and consumption of M. flexuosa along rivers. Gene flow patterns revealed that migrants are sourced primarily from within the same river basin, such as those from Madeira and Tapajós basins. Our work suggests that rivers and their inhabitants are a critical element of the landscape in Amazonia and have impacted the dispersal and subsequent distribution of tropical palm species, as shown by the patterns of genetic variation in M. flexuosa.

GENETIC DIVERGENCE AMONG Passiflora cristalina Vanderpl & Zappi. GENOTYPES BASED ON FLOWER AND FRUIT CHARACTERISTICS

O presente trabalho teve como objetivo avaliar a divergencia genetica entre genotipos de Passiflora cristalina e quantificar a contribuicao relativa de 30 caracteres de flores e frutos, auxiliando o resgate e a caracterizacao, visando a preservacao e o uso em futuros programas de melhoramento. Foram avaliados 150 frutos e 150 flores coletados em 15 genotipos com ocorrencia natural, no municipio de Alta Floresta, MT. A caracterizacao dos genotipos foi realizada mediante 30 caracteres morfologicos de flores e frutos, sendo 21 destes para flor e 9 para fruto. Os dados foram avaliados utilizando as metodologias dos componentes principais e do agrupamento obtido pelo metodo UPGMA, a partir da matriz de dissimilaridade (distância euclidiana media), com auxilio do programa Genes. Pela analise dos componentes principais, verificou-se que os tres primeiros componentes explicam 52,11% da variacao acumulada. As caracteristicas que mais contribuiram para discriminacao dos genotipos foram peso fresco do fruto, comprimento do estigma, comprimento dos filamentos da corona, largura do fruto, largura da petala e peso da polpa, sendo estes caracteres mais responsivos para selecao dos genotipos de P. cristalina. As menores contribuicoes para a diversidade foram obtidas dos caracteres largura da antera, largura da bractea e comprimento do fruto. Por meio do metodo de agrupamento UPGMA, foi possivel constatar que uma grande divergencia genetica entre os genotipos analisados, uma vez que todos os genotipos se agruparam acima de 50% de dissimilaridade. Com esse estudo, foi possivel identificar os genotipos 4; 5 e 9 como os mais divergentes e, consequentemente, os mais indicados para cruzamentos em futuros programas de melhoramento e de conservacao genetica da especie.