Navegando por Autor "Moreira, Francisco Wagner Araujo"

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Assessing the impacts of mining activities on zooplankton functional diversity.
(2016) Moreira, Francisco Wagner Araujo; Leite, Mariangela Garcia Praça; Fujaco, Maria Augusta Gonçalves; Mendonça, Fellipe Pinheiro Chagas; Campos, Larissa Paraguassú; Sant'Anna, Eneida Maria Eskinazi
Mining activities generate countless environmental impacts, including heavy-metal contamination, sorting and increased turbidity. In aquatic ecosystems these impacts can drastically affect the initial links of the food chain, such as zooplankton. Methods: To evaluate how the different mining activities can influence the structure and functional diversity of zooplankton, we investigated the geochemical characteristics of the water and sediment in two small impoundments impacted by different mining activities (kaolin and iron extraction). We also explored zooplankton composition, species diversity and functional diversity (feeding guilds taxa). Results: As expected, the water and the sediment of both of the reservoirs showed high concentrations of trace elements, particularly Al, Ba, Fe, Mg, Mn, Sr and Zn. Zooplankton biomass and diversity were markedly reduced (< 12 μg.DW.L-1 and H’ < 1.5, respectively), and negatively correlated with turbidity and total suspended solids. Small microphages dominated the trophic composition of zooplankton, and an alternation of trophic guilds was not observed, since the dynamics of raptorial organisms was essentially linked to the temporal fluctuation of a single species of rotifer (Polyarthra cf. dolichoptera). Conclusions: In addition to changes in the aquatic habitat and zooplankton composition, the functional niches were also affected by the mining impacts. The use of the functional diversity analysis can emerge as a valuable approach to understand how zooplankton communities respond to drastic environmental changes.
Composition, body-size structure and biomass of zooplankton in a high-elevation temporary pond (Minas Gerais, Brazil).
(2016) Moreira, Raquel Aparecida; Rocha, Odete; Santos, Renata Martins dos; Dias, Emerson Silva; Moreira, Francisco Wagner Araujo; Sant'Anna, Eneida Maria Eskinazi
Small ponds are vital inland water bodies, recognized as small repositories of freshwater biodiversity, but neglected in terms of conservation. Although high-elevation ponds are difficult to sample and monitor, it is important to extend their study, in view of their importance to aquatic biodiversity. The aim of this study was to analyze the composition, size structure biomass and diversity of zooplankton community in a temporary pond (Lagoa Seca) of a low-alpine area in the southern part of Serra do Espinhaço mountain in Minas Gerais State, Brazil. Three ecological aspects were analyzed: (I) the taxonomic composition of the zooplankton assemblage, (II) the size structure and biomass of the main groups in the zooplankton community and (III) whether the morphometric characteristics and biomass of the zooplankton result from the dominance of the microzooplankton, as expected in habitats subjected to frequent and strong disturbances, such as temporary ponds. Zooplankton samples were taken during the rainy period (October 2010 to January 2011) in different mesohabitats, from the shallowest areas covered by emergent macrophytes to the open water area covered mainly by submerged macrophytes. The zooplankton community consisted of a small number of taxa (29). Rotifera showed the highest richness, with 21 taxa recorded, of which the most constant species were the cosmopolitan Lecane lunaris, L. obtusa and Lepadella patella. Among the Cladocera, Bosmina freyi and Moina minuta were the pelagic species recorded. The other cladoceran species observed are associated with littoral vegetation, and represented mainly by Alona ossiani, Chydorus pubescens, Ephemeroporus tridentatus and Ilyocryptus spinifer. The zooplankton biomass was very low (the maximum dry weight, observed at the peak of the rainy period in January was 62 μg.m-3). The zooplankton community was dominated by the microzooplankton, with the maximum body length below 900 μm. This assemblage was very changeable in the short term, both in numerical density and size structure, probably because of the highly variable hydrological regime of the pond. The results from zooplankton composition, including the first record of the rotifer Microcodon clavus to Minas Gerais state and the second in Brazil, highlighted the important role that high-elevation temporary ponds can play as aquatic biodiversity reserves. These unique ecosystems deserve greater efforts of research and monitoring, including studies of their hydrological patterns, biological diversity, and adaptive mechanisms of the zooplankton community.
Impacts of mining in artificial lake of Iron Quadrangle-MG : past marks and changes of the present.
(2019) Campos, Larissa Paraguassú; Leite, Mariangela Garcia Praça; Moreira, Francisco Wagner Araujo; Mendonça, Fellipe Pinheiro Chagas; Sant'Anna, Eneida Maria Eskinazi
A locus of intense mining activity since the seventeenth century, the Iron Quadrangle, corresponds to one of the most important mineral provinces in the world. Located in Minas Gerais, Brazil, it keeps in its territory marks of past mining activities still in expansion. Such changes, recorded in water bodies of the region’s watersheds, impact not only locally, but also reach adjacent ecosystems as well as those located downstream of mining companies. In this situation, an artificial lake is found in the upper course of the Mata Porcos creek sub-basin. The area was once an old place of gold exploration in the eighteenth and nineteenth centuries, and is currently influenced by active iron mining and inactive iron–manganese mining upstream. With the aim of evaluating this reservoir and contributing to the understanding of lentic systems under the influence of mining, this study analyzed the physical and chemical characteristics of sediments from the bottom of this lake, identifying the possible contributions of anthropic origin. Sediment samples were collected at nine points along two hydrological years and then submitted to granulometric, mineralogical and geochemical analyses. The geochemical signature of this lake is marked by As, Fe and Mn elements associated with both the local geological substrate and anthropic activities undertaken in the surroundings. Due to the high As concentrations, distribution maps were made using the IDW interpolation method to understand the distribution of this potentially toxic element that has a strong correlation with gold mining practiced for more than 300 years at the site.
Influência da mineração nos aspectos limnológicos e estrutura da comunidade zooplanctônica de barragens artificiais da Bacia do Ribeirão Mata Porcos (MG).
(2013) Moreira, Francisco Wagner Araujo; Sant'Anna, Eneida Maria Eskinazi
A mineração exerce um papel fundamental na economia dos principais países. Contudo, as preocupações frente aos impactos causados pela exploração mineral, com destaque aos recursos hídricos é, com frequência, um dos aspectos de conflito mais eminentes na interface mineração e sociedade. Este estudo foi realizado em barragens afetadas por rejeitos originários de atividades minerárias, compreendendo os aspectos limnológicos e a composição e distribuição espacial do zooplâncton em três sistemas localizados no Quadrilátero Ferrífero (MG). Foram selecionados três ambientes com características distintas: uma barragem sob efeito direto da extração de caulim (Barragem Caulim), outra barragem sob influência da mineração de ferro (Barragem Ferro) e uma terceira considerada sem entrada direta de rejeitos minerários (SEDR). Do ponto de vista limnológico, os reservatórios Caulim e Ferro apresentaram extrema redução sazonal da transparência da água com valores sempre inferiores a 1m (Secchi). Não foi observada estratificação térmica nos lagos, e a biomassa algal foi bastante reduzida (máximo de 13 μg/l), com oscilação sazonal entre os estados oligotróficos e mesotróficos. Os indicadores quantitativos da comunidade zooplanctônica apontaram para uma baixíssima diversidade de espécies (< 1,5 H’) em todas as barragens, o que indica efeitos de impacto difusos, além dos efeitos diretos da mineração. Foi observada ainda uma redução expressiva da densidade zooplanctônica (máximo de 55ind/l), especialmente na barragem Caulim, onde a densidade máxima observada não ultrapassou 25ind/l. A distribuição vertical do zooplâncton apresentou em geral, um padrão comum às barragens, sendo observado um distanciamento entre os máximos zooplanctônicos e os picos verticais de biomassa algal. Esses resultados indicam que os efeitos de atividades minerárias podem afetar substancialmente a comunidade zooplanctônica, reduzindo não apenas sua estrutura taxonômica, mas principalmente a possibilidade de aproveitar habitats mais favoráveis ao seu desenvolvimento, como aqueles associados aos locais de máxima disponibilidade alimentar. Esses padrões podem ter potenciais efeitos sobre a estrutura da cadeia trófica aquática.