Macro-scale (biomes) differences in neotropical stream processes and community structure

The definition of conservation strategies and ecological assessment schemes requires understanding ecosystem patterns over multiple spatial scales. This study aimed to determine if macro-scale structural and functional (processes) patterns associated with stream ecosystems differed among three neotropical biomes (Cerrado, Amazon, Atlantic Forest). We compared the aquatic communities (benthic invertebrates and hyphomycetes) and processes (decomposition rates, primary production and biofilms growth and aquatic hyphomycetes reproduction rates-sporulation) of Cerrado stream sites (neotropical savannah) against those of stream sites in the connecting biomes of the Atlantic Forest and Amazon (rainforests). We expected that, contrary to the biome dependency hypothesis the community structure and processes rates of streams at the biome-scale would not differ significantly, because those ecosystems are strongly influenced by their dense riparian forests, which have a transitional character among the three biomes. Fifty-three stream sites were selected covering a wide range of geographic locations (Table 1), from near the Equator (2° S) in the Amazon, to intermediate latitudes in the Cerrado (12-19° S), and latitudes closer to the tropic of Capricorn in the Atlantic Forest (19º-25° S). We found that: 1) at the abiotic level, the aquatic ecosystems of the three biomes differed, which was mostly explained by large-scale factors such as temperature, precipitation and altitude; 2) functional and structural variables did not behave similarly among biomes: decomposition and sporulation rates showed larger differences among biomes than invertebrate and aquatic hyphomycete assemblages structure; 3) invertebrate assemblages structure differed between the rainforests and Cerrado but not between rainforests (Amazon and Atlantic Forest) whereas aquatic hyphomycetes were similar among all biomes; 4) biofilm growth and algae concentration in biofilms of artificial substrates were highly variable within biomes and not significantly different between biomes. Overall, aquatic ecosystem processes and community structure differed across biomes, being influenced by climatic variables, but the variation is not as pronounced as that described for terrestrial systems. Considering the potential use of these functional and structural indicators in national-wide ecological assessments, our results indicate the need to define different reference values for different biomes, depending on the variable used. The approach followed in this study allowed an integrative analysis and comparison of the stream ecosystems across three tropical biomes, being the first study of this kind. Future studies should try to confirm the patterns evidenced here with more sites from other areas of the three biomes, and especially from the Amazon, which was the least represented biome in our investigation. © 201

Plant litter dynamics in the forest-stream interface: Precipitation is a major control across tropical biomes

Riparian plant litter is a major energy source for forested streams across the world and its decomposition has repercussions on nutrient cycling, food webs and ecosystem functioning. However, we know little about plant litter dynamics in tropical streams, even though the tropics occupy 40% of the Earth's land surface. Here we investigated spatial and temporal (along a year cycle) patterns of litter inputs and storage in multiple streams of three tropical biomes in Brazil (Atlantic forest, Amazon forest and Cerrado savanna), predicting major differences among biomes in relation to temperature and precipitation regimes. Precipitation explained most of litter inputs and storage, which were generally higher in more humid biomes (litterfall: 384, 422 and 308 g m-2 y-1, storage: 55, 113 and 38 g m-2, on average in Atlantic forest, Amazon and Cerrado, respectively). Temporal dynamics varied across biomes in relation to precipitation and temperature, with uniform litter inputs but seasonal storage in Atlantic forest streams, seasonal inputs in Amazon and Cerrado streams, and aseasonal storage in Amazon streams. Our findings suggest that litter dynamics vary greatly within the tropics, but point to the major role of precipitation, which contrasts with the main influence of temperature in temperate areas. © 2017 The Author(s)

Produtividade bacterioplanctônica e fitoplanctônica nos ecossistemas aquáticos do trecho médio da bacia do Rio Doce MG.

This research had as major objective to quantify the existent relationships between bacterioplankton and phytoplankton production rates, determining the importance of these communities on the carbon fixation and organic matter transfer in rivers and lakes of the middle stretch of the Rio Doce basin in Minas Gerais state (southeast Brazil) during dry and rainy periods of the years 1999-2001. The concentrations of carbon, nitrogen and phosphorus and the N/P ratios were used to evaluate possible relationships between productivity and trophic status based in diel, seasonal, and annual patterns. This thesis was divided into 5 chapters approaching mainly phytoplankton and bacterial production rates in rivers and lakes of Rio Doce basin. The testing hypothesis is that production rates varies seasonally (dry and rainy periods) thus resulting in changes of the BP/PP ratios, as a consequence of changes in the inputs of allochthonous matter (nutrients) being also affected by distinct internal loads during these periods. The study was conducted in 8 rivers of the middle stretch of Rio Doce basin and in 7 lakes of the Rio Doce State Park and surrounding area, during dry and rainy periods from 1999 to 2001. The ecosystems presented a wide trophic status (from oligo to eutrophic), as well as bacterioplantonic (0.005 5.7 mg C.m-3.h-1) and phytoplanctonic (0.01 747.5 mg C.m-3.h-1) production rates. For the lotic environments, seasonality and nutrient concentration were considered the most important factors for productivity. Significant positive correlations were obtained between phosphorus concentrations and bacterial production rates. For the lentic environments seasonality was only evident for bacterial production rates with high N/P ratios, suggesting phosphorus limitation in most of the lakes. Bacterial production in spite of presenting lower values than the ones recorded for phytoplankton could be an important carbon source mainly within deep layers and more eutrophic ecosystems.Universidade Federal de Sao CarlosEsta pesquisa teve como objetivo principal quantificar as relações existentes entre as taxas de produção bacterioplanctônica e fitoplanctônica, determinando a importância dessas comunidades na fixação de carbono e transferência de matéria orgânica em rios e lagos do trecho médio da bacia do Rio Doce-MG, nos períodos de chuva e seca. As concentrações de carbono, nitrogênio e fósforo e as razões N/P na água, foram usadas para avaliar possíveis relações entre produtividade e grau de trofia, com base em padrões diários, sazonais e anuais. O trabalho foi dividido em 5 capítulos que abordam principalmente a produção primária e bacteriana em rios e lagos do médio Rio Doce. A hipótese central testada é que a produção primária varia sazonalmente resultando em alteração da relação PB/PF em função, principalmente, do aporte de matéria orgânica alóctone sendo também influenciada pela carga interna de nutrientes. Os estudos foram realizados em 8 rios do trecho médio da bacia do Rio Doce e em 7 lagos do Parque Estadual do Rio Doce e área de entorno, durante os períodos de seca e chuva de 1999 a 2001. Os ambientes apresentaram uma ampla variação trófica (oligo a eutróficos), assim como das taxas de produção bacterioplantônica (0,005 5,7 mg C.m-3.h-1) e fitoplanctônica (0,01 747,5 mg C.m-3.h-1). Para os ambientes lóticos, sazonalidade e a concentração de nutrientes foram considerados fatores importantes para a produtividade. Correlações positivas e estatisticamente significativas foram obtidas entre as concentrações de fósforo e os valores de produção bacteriana. Para os ambientes lênticos a sazonalidade ficou evidente apenas para a produção bacteriana com destaque para as elevadas razões N/P, sugerindo uma limitação por fósforo na maioria dos lagos. A produção bacteriana apesar de apresentar sempre menores valores pode ser considerada uma importante fonte de carbono principalmente nas maiores profundidades e nos ambientes mais eutrofizados

A review on the availability of ecological data aiming new researches in Peri Lagoon

The increase in population as well as the water resource demand has been intensifying the human influence in Peri Lagoon basin. A review on the availability of data concerning the ecology of Peri Lagoon was made, aiming at the development of new researches to understand the functioning of this ecosystem. This information can contribute to the elaboration of a conservation proposal and sustainable use of the Lagoon in the future. High cyanobacteria density (Cylindrospermopsis raciborskii) was detected in the Lagoon waters, which happens to be a risky situation for the ecosystem’s health and consequently for the population. The review highlights a lack of available information about the dynamics, functioning and structure of aquatic communities, as well as their relationships with the surrounding area and the infl uence of abiotic factors. Series of continuum data with respect to time are also considered to be lacking. Educational, political and social practices in environmental conservation are necessary, aiming at the management and sustainable use of Peri Lagoon basin. These practices will guarantee water resource quality and availability for the current and future generations

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http://dx.doi.org/10.5007/2175-7925.2008v21n2p133O aumento do contingente populacional, bem como da demanda pelo recurso hídrico, têm intensificado as ações humanas na região da bacia da Lagoa do Peri. Este trabalho realizou uma revisão da disponibilidade de dados ecológicos da Lagoa do Peri, visando o direcionamento de novas pesquisas para a compreensão do funcionamento do ambiente. Estas informações podem contribuir na elaboração de uma futura proposta de conser- vação e uso sustentável da Lagoa. Alta densidade de cianobactérias Cylin- drospermopsis raciborskii foi diagnosticada nas águas da Lagoa, e apresenta-se como situação de risco para a saúde do ecossistema e conseqüen- temente da população. Destacam-se lacunas a respeito da dinâmica, funcionamento e estruturação das comunidades aquáticas, suas relações com o entorno e a influência de fatores abióticos. Séries de dados contínuos ao longo do tempo também são informações ausentes. Percebese a necessidade de medidas educacionais, políticas e sociais na conservação do ambiente, voltadas para o manejo e uso sustentável da bacia da Lagoa do Peri. Estas práticas garantirão a qualidade e disponibilidade do recurso hídrico para esta e as futuras gerações.A review on the availability of ecological data aiming new researches in Peri lagoon. The increase in population as well as the water resource demand has been intensifying the human influence in Peri Lagoonbasin. A review on the availability of data concerning the ecology of Peri Lagoon was made, aiming at the development of new researches to understand the functioning of this ecosystem. This information can contribute to the elaboration of a conservation proposal and sustainable use of the Lagoon in the future. High cyanobacteria density (Cylindrospe- rmopsis raciborskii) was detected in the Lagoon waters, which happens to be a risky situation for the ecosystem’s health and consequently for the population. The review highlights a lack of available information about the dynamics, functioning and structure of aquatic communities, as well as their relationships with the surrounding area and the influence of abiotic factors. Series of continuum data with respect to time are also considered to be lacking. Educational, political and social practices in environmental conservation are necessary, aiming at the management and sustainable use of Peri Lagoon basin. These practices will guarantee water resource quality and availability for the current and future generations

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http://dx.doi.org/10.5007/2175-7925.2008v21n1p139A Lagoa da Conceição é um dos principais focos turísticos da Ilha de Santa Catarina, sendo conseqüente alvo de modificações de origem antrópica. Pesquisas têm caracterizado e avaliado a gravidade de seus principais contaminantes. Neste trabalho foi feita uma revisão da disponibilidade de dados relacionada à ecologia da Lagoa, visando direcionar novas pesquisas e estudos complementares para compreensão da dinâmica do ambiente e para seu uso sustentável. A Lagoa recebe influencia de esgotos domésticos, metais pesados e ocupação desordenada. A influência das águas marinhas é mais observada nas regiões próximas ao canal da Barra, que leva a diminuição das concentrações de alguns nutrientes e alterações das comunidades. Averiguou-se a falta de dados contínuos e de longa duração sobre a dinâmica das comunidades aquáticas, produtividade do ambiente, ciclos do nitrogênio e fósforo e das concentrações de clorofila. O padrão de circulação da Lagoa, assim como a influência do Canal da Barra, são informações importantes para compreensão do funcionamento do ecossistema. Nota-se extrema necessidade de um programa de monitoramento periódico e contínuo de dados físicos, químicos e biológicos para avaliar as alterações no ambiente. Estas informações serão muito importantes para futuras propostas de educação ambiental, recuperação e para a preservação da Lagoa.Conceição Lagoon: a review on the availability of ecological data aiming new researches on the ecosystem. Conceição Lagoon is one of the major touristic centers on Santa Catarina Island and, as a consequence, it has been subjected to great changes by anthropogenic actions. Research has characterized and evaluated the magnitude of the main contaminants in the Lagoon. A review on the availability of data concerning the ecology of the Lagoon was made, aiming at the development of new researches and complementary studies to better understand the dynamics of this ecosy- stem and to achieve its sustainable use. The Lagoon receives the influ- ence from sewage waste, heavy metals and disordered land occupation. The effect of sea water is strongest nearby Barra Channel, which gene- rates  a decrease in the concentration of some nutrients and a distur- bance  in the aquatic communities. A lack of continuous and long-lasting data on community dynamics, environmental productivity, nitrogen and phosphorus cycles and chlorophyll concentration was observed. Circulation patterns in the Lagoon, as well as the influence of the Barra Channel, are essential information for a proper understanding of the ecosystem’s functioning. A periodic and continuous monitoring program on physical, chemical and biological data is extremely necessary in order to evaluate the environmental changes. This information will be of great importance for future proposals concerning environmental education, restoration and preservation related to the Lagoon