Search

Changes in equilibrium states in shallow lakes are associated with disturbances and resilience. The study evaluated the structure and composition of phytoplankton functional groups in two lakes, Lagoa do Paó (turbid waters) and Santa Lúcia (clear waters). Monthly collections of limnological variables and phytoplankton occurred between August 2014 and June 2015 in the pelagic region. The lakes shared five functional groups: K, S1 , X1 , W2 and P, formed by coccoid and filamentous cyanobacteria, coccoid chlorophytes and euglenophytes, and desmids, respectively. The canonical correspondence analysis evidenced a clear separation, highlighting the groups TD, N, W2 and S1 in Santa Lúcia and functional groups composed of potentially toxic cyanobacteria in Lagoa do Paó (SN, Lo), indicating that the submerged macrophyte coverage can act promoting the phosphorous stabilization in the sediment in Santa Lúcia, reducing its contribution to the water column and inhibiting the dominance of the mentioned species. Temperature, pH, phosphorus and light attenuation coefficient influenced the occurrence of H1 , SN, S1 , W2 , X1 , D, and Lo , in the Lagoa do Paó. The composition and structure of the functional groups responded in the two lakes with some functional groups associated with toxic cyanobacteria occurring exclusively in Lagoa do Paó, having also been observed the sharing of some functional groups.

O estado trófico dos lagos geralmente é dependente da concentração de fósforo na água, que por sua vez é influenciado pelo teor desse nutriente no sedimento, mas nem todo fósforo sedimentar está disponível, requerendo quantificação das frações através de fracionamento químico. Nesse sentido, o trabalho objetivou quantificar as frações disponíveis do fósforo utilizando fracionamento químico do sedimento superficial, em reservatórios de usos múltiplos de brejos de altitude. A pesquisa foi executada na bacia hidrográfica do Rio do Canto (BHRC) (-6°55’52,31”S, 35°42’33,91”W e -6°58’41,26”S, -35°42’37,07”W), região do brejo de altitude de Areia (Paraíba, Brasil), durante os meses de novembro e dezembro de 2014. Mediu-se o potencial hidrogeniônico, potencial de oxi-redução, a granulometria, teores de matéria orgânica, ferro alumínio, cálcio e as frações de fósforo sedimentar usando o protocolo SMT. Os dados foram submetidos à análise de componentes principais. A fração biodisponível, correspondente ao fósforo orgânico e não apatítico representou entre 15 a 38% do teor de fósforo total quantificado no sedimento dos reservatórios monitorados na BHRC. Os resultados indicam a seguinte ordem crescente de biodisponibilidade de fósforo para os reservatórios monitorados na BHRC: R7

This opinion article examines the main consequences of the current environmental crisis in Brazil, including dismantling of environmental policies and protection of conservation areas, absence of m...

A eutrofização, impacto qualitativo na água, eventualmente de origem antrópica, caracteriza-se pelo enriquecimento do meio aquático por nutrientes, principalmente fósforo. A Lagoa do Paó, ambiente lêntico no município de Alagoa Grande, Paraíba, recebe grande parte da carga de esgoto da zona urbana. Objetivou-se no presente estudo monitorar a qualidade da água, o índice de estado trófico e os teores de fósforo desse ambiente. Realizaram-se coletas de água de julho a dezembro de 2015, em um ponto central da lagoa. Determinaram-se a transparência, o pH, a condutividade elétrica, o oxigênio dissolvido, teores de fósforo total e ortofosfato da água. Obtiveram-se dados relativos à precipitação pluviométrica do período estudado. Foi calculado também o índice de estado trófico. Os resultados evidenciaram a predominância de águas túrbidas, com valores de transparência inferiores a 0,2 m e elevada condutividade elétrica, com valores superiores a 1.000 µS/cm. O pH manteve-se alcalino e o oxigênio dissolvido exibiu baixas concentrações, apresentando na maioria dos meses de estudo desconformidades com os padrões da legislação vigente. Observaram-se altos teores de fósforo total e ortofosfato, classificando o ambiente como eutrófico. Os resultados mostram influência das ações antrópicas sobre o ecossistema, as quais comprometem a qualidade da água e seus usos múltiplos.

Historically, the reduction in water quality has been associated with changes in land use, especially changes in urbanization and expansion of agricultural frontiers. The objective of this study was to understand the characteristics of the diatomological community and the use and occupation of the soil around three reservoirs (Arara, Rio do Canto and Araçagi) and natural lagoon (Lagoa do Paó) (Northeast Brazil). Land use was determined using high spatial resolution satellite images. Abiotic variables of water and total phosphorus, organic matter and diatoms in surface sediments were analyzed. Abiotic variables and assemblages of diatoms were analyzed using Principal Component Analysis (PCA). Four types of land use have been identified, associated with anthropogenic change and intensive use of the landscape. The PCA separated the reservoirs by trophic status based on the total phosphorus in the water. 24 taxa of diatoms distributed in 12 genera and 10 families were identified in the sediment. Our results indicate the occurrence of planktonic, epiphytic and benthic diatoms adapted to different trophic gradients

Barbosa LG, José Carlos Lopez JC, Morais M, Amorim CA. 2022. Limnology of Drylands – SIL Working Group Report. SILnews 79

Aim The study analyzed the potential use of the phytoplankton functional groups as an environmental bioindicator in aquatic ecosystems of Brazilian semiarid region. Methods Using data collected over five years of a natural lagoon and two reservoirs, we evaluate the relationship between functional groups and environmental conditions through the multivariate approach. The Q index was applied to assess ecological status in these ecosystems. Results In Panati, the temporary and natural lagoon, the partial habitat desiccation and presence of macrophytes reflected in the less nutrients concentrations and phytoplankton composition, with high biomass of coccoids Chlorophyceae, diatoms and desmids (functional groups J, MP and N, respectively). Taperoá and Soledade reservoirs presented high cyanobacteria contribution, however the biomass and contribution of cyanobacteria in Taperoá (SN, S1) were lower than in Soledade. In this reservoir, cyanobacteria were more abundant, alternating in dominance (LO, M, LM, SN, S1). According to tendencies revealed by Redundancy Analysis (RDA), the main driving abiotic factors on the phytoplankton functional groups were pH, nutrients and light availability. As expected, phytoplankton composition directly influenced the Q index result, showing mostly bad to tolerable conditions in Soledade, medium to good in Taperoá and good to excellent in Panati. Conclusions The Q index was a good tool to assess the water quality and ecological status in aquatic ecosystems from the Brazilian semiarid region, reflecting the influence of natural control mechanisms on the harmful cyanobacteria blooms in temporary ecosystems. Resumo: Objetivo O estudo analisou o potencial uso dos grupos funcionais do fitoplâncton como bioindicador ambiental em ecossistemas aquáticos do semiárido brasileiro. Métodos Usando dados coletados de uma lagoa natural e dois reservatórios ao longo de cinco anos, avaliamos a relação entre grupos funcionais e condições ambientais por meio de uma abordagem multivariada. O índice Q foi aplicado para avaliar o estado ecológico desses ecossistemas. Resultados Em Panati, uma lagoa temporária e natural, a dessecação parcial do habitat e presença de macrófitas aquáticas refletiram nas menores concentrações de nutrientes e na composição do fitoplâncton, com alta biomassa de Chlorophyceae cocóides, diatomáceas e desmídias (grupos funcionais J, MP e N, respectivamente). Os reservatórios Taperoá e Soledade apresentaram alta contribuição de cianobactérias, no entanto a biomassa e a contribuição de cianobactérias em Taperoá (SN, S1) foram menores do que em Soledade. Nesse reservatório, as cianobactérias foram mais abundantes, alternando em dominância (LO, M, LM, SN, S1). De acordo com as tendências reveladas pela análise de redundância (RDA), os principais fatores abióticos atuantes sobre a estrutura dos grupos funcionais do fitoplâncton foram o pH, os nutrientes e a disponibilidade de luz. Como esperado, a composição do fitoplâncton influenciou diretamente o resultado do índice Q, mostrando condições ruins a toleráveis em Soledade, médias a boas em Taperoá e boas a excelentes em Panati. Conclusões O índice Q mostrou-se uma boa ferramenta para avaliar a qualidade da água e o estado ecológico de ecossistemas aquáticos do semiárido brasileiro, refletindo a influência de mecanismos naturais de controle sobre o florescimento de cianobactérias prejudiciais em ecossistemas temporários.

In northeastern Brazil, the drought history has been well documented, reflecting a resilient population with a robust regional identity. Last year, in response to the need to perpetuate water access and reduce scarcity, the Brazilian government implemented a program called the Program One Million Cisterns (P1MC). Considering that the need for water resource perpetuation can impact traditional knowledge transmission between generations, this study aimed to analyze the knowledge regarding rock pools in a small village located in a semiarid region in Brazil. The interviews addressed questions about the traditional knowledge, use, and management of rock pools. The abiotic and biological water variables were collected to establish the population's knowledge status. Our results identified that the use and management of rock pools were reduced after implementing P1MC. Despite the historical relevance of these ecosystems, their use was abandoned by most of the inhabitants, except for domestic use. Therefore, the transmission of traditional knowledge regarding rock pools have decreased between generations, compromising hydric security and representing a serious socio-economic risk for a region characterized by extreme droughts.

The Andalusian International University held a workshop entitled Temporary wetlands’ future in drylands under the projected global change scenario in March 2020 in Baeza, Spain, with 26 participants from 10 countries. The workshop objectives were to promote international cooperation and scientific exchange on the conservation and protection of temporary wetlands. The participants highlighted the extreme conditions that temporary and permanent wetlands, ponds, and shallow lakes are currently facing and predicted a dismal future for these systems due to climate change. To foster a holistic view of these ecosystems, the workshop included wetland watersheds. It was concluded that the main threats are those affecting water quality and quantity as well as egg-seed banks, species population dynamics, and food webs. The inherent characteristics of waterbodies in drylands, including high resilience and resistance to harsh conditions, are already negatively impacted by direct human actions and climate change. Another threat is the time lag between scientific warnings about threats and the social and political concern leading to mitigating actions. Thus, more effective actions to protect and conserve temporary wetlands are essential. Research networks could help stimulate the necessary conservation actions, but the global recession due to the COVID-19 pandemic will pose a challenge as economies are burdened with urgent expenditure. This special issue of the journal Inland Waters is the outcome of the workshop presentations and is composed of the ensuing papers on wetlands in drylands. This work was supported by UNIA. Universidad Internacional de Andalucia [grant number: UNIA-WORKSHOP-2019]; Centro de Estudios Avanzados en Ciencias de la Tierra [grant number: CEACTIERRA-2020]. SB was supported by the PONDERFUL project (Pond ecosystems for resilient future landscapes in a changing climate) funded by European Union's Horizon 2020 research and innovation programme under grant agreement No. 869296. EJ was supported by the TUBITAK researchers program BIDEB 2232 (project 118C250). TZ was supported by the Israel Water Authority.

An undescribed diaptomid copepod probably belonging to a new Mastigodiaptomus species has been discovered and was very abundant in El Junco Lake (San Cristóbal Island, Ecuador) from 1966 until 2004. The species was not found in samples from 2007, 2008 or 2018. The loss of this key species from the lake coincides with the illegal introduction of Nile tilapia to El Junco Lake in 2005 and its subsequent eradication in 2008. The disappearance of this biogeographically and ecologically important copepod population may be explained by direct mechanisms of predation and competition, by a combination of both processes, and by indirect mechanisms linked to alterations in the lake ecosystem. The effects of fish eradication using rotenone may have contributed to the loss of the diaptomid population and to preventing its recovery. This article discusses the search for sources of propagules for recolonization and possible reintroduction scenarios and procedures.

BackgroundMemory is a collective ownership based on facts and past events. Aristotle and Agostinho were the first philosophers to investigate it, including the dimensions of time and memory inhabited by man. Northeastern Brazil has a rich cultural history linked to water scarcity in the region, one of the main limiting factors to the development of rural populations. Among alternative sources, temporary ecosystems known as rock pools have been used as rainwater storage in arid and semiarid regions around the world. Considering the hypothesis that the arrival of perennial water sources can impact memory transmission between generations, this study aimed to analyze the popular knowledge about rock pools, a traditional and ancient water source.MethodsInformation about the use and management of rock pools in the Brazilian semiarid region was collected by interviewing residents from a small city near an inselberg. The interviews presented specific questions about the structure, characteristics, traditional knowledge, use and management of rock pools. During sampling, 20 rock pools were visited by two key informants, i.e., those with more experience and knowledge about these ecosystems.ResultsOur results identified that the use and management of rock pools were reduced after the Brazilian government implemented the One Million Cisterns Project. Therefore, despite the historical relevance of these water bodies, their uses were forgotten by most of the inhabitants and those from neighboring locations, remaining for domestic use.ConclusionsResults about traditional knowledge indicated that the generation interviewed still remembers such method. However, with the presence of cisterns, the transmission of traditional knowledge about rock pools has decreased between the families and generations, presenting a serious social risk for a region characterized by extreme and prolonged droughts.

Reservoirs provide valuable services to human beings, especially in arid, semi-arid, and Mediterranean regions affected by water scarcity. The present effort aims to study the environmental descriptors of variation and the main factors influencing phytoplankton composition, structure, and diversity in five reservoirs in Santiago Island, Cape Verde, a region affected by water availability. Five campaigns took place from 2016 to 2020 to sample phytoplankton and measure environmental variables according to standard analytical methodologies. Environmental results (17 water physicochemical variables, air temperature, and precipitation) revealed that reservoirs differ in the geological influence variables. The high levels of P and N in water seem to be related to Land Use/Land Cover and are responsible for water-quality degradation. Cyanobacteria dominated the phytoplankton community and posed high risk levels, especially considering that the identified taxa are potential producers of different toxins. Taxa responsible for this dominance were not the same in all reservoirs, emphasizing the dominant role of local habitat factors on community composition and diversity. Overall, the results reveal the importance of defining integrated management plans/strategies for the set of five studied reservoirs, since the processes influencing variation in the phytoplankton community are temporal-scale dependent, with similar biogeographic patterns.

Drought is an important driver of change in aquatic ecosystems and generally acts as a filter to select biological traits capable of persisting under severe environmental circumstances. Drylands are highly vulnerable to climate change and increases in climate variability. Consequently, an increase in the processes of eutrophication, salinization, and habitat desiccation may be observed in response to the loss of the hydrological connectivity. The International Network on Limnology of Drylands (INLD) was created with the overall goal of understanding the functioning and conservation status of aquatic ecosystems in drylands globally. INLD was made official in 2016 through the International Society of Limnology. Its objectives are to (1) assess the current state of biological diversity in dryland aquatic ecosystems, (2) evaluate the multiple environmental stressors acting in drylands, and (3) develop models to predict effects of global change on drylands. This special issue, Limnology of Drylands, consists of 10 manuscripts focused on the effects of environmental pressures, including global warming, on the biodiversity and distribution of aquatic communities in drylands.

Allochthonous or autochthonous disturbances may change waterbodies from a clear to a turbid state, increasing the availability of nutrients and promoting blooms of harmful cyanobacteria. Submerged macrophytes may play an important role in alleviating the adverse effects of phosphorus resuspension and release from bottom sediments. We assessed the effects of allochthonous disturbances (rainfall and wind) on phosphorus release by constructing models using data from 2 shallow lakes with contrasting steady states. Using partial least squares path modeling, we examined submerged macrophytes, phytoplankton, and possible drivers of their abundance. In the clear-water lake, the concentrations of total phosphorus (TP) had the greatest direct influence on the macrophyte percentage of volume infested and phytoplankton biomass, followed by concentrations of TP in the sediment. In the turbid lake, the TP concentration in the water was the most important factor affecting phytoplankton biomass directly, followed by disturbances on TP concentration in the sediment and euphotic zone. Our models support the hypothesis that submerged macrophyte coverage acts as a stabilizing force to prevent the proliferation of cyanobacteria and stabilize the clear-water phase in semiarid lakes. However, potential mutual inhibition mechanisms between the submerged macrophyte Nitella cernua and the cyanobacterium Microcystis aeruginosa need to be better addressed for restoration purposes in lakes with shallow clear waters.

Environmental laws are necessary to governance and a sustainable use of nature resource. Brazil federal environmental laws have been improved in the last 50 years, with significant advances in legal provisions and monitoring systems. However, the recent dismantling of legal environmental framework by the Bolsonaro administration has led to increase of human pressure on biodiversity and ecosystems. The purpose of this article is to present some environmental impacts in Brazil due to the dismantling of environmental laws. To address this, some examples we gathered and established a timeline of Brazilian environmental laws to allow a perspective of temporal dismantling. Among the environmental impacts related to the dismantling of environmental policies are the increase in deforestation in the Amazon, the release of pesticides, and the lack of actions to minimize the effects of oil spill. In conclusion, the current Brazilian federal govern is dismantling environment laws, and the consequent lack of environmental governance in the country, will result in severe negative impacts to the biodiversity and human well-being.

In semi-arid regions, eutrophic waters and stable climatic conditions favor the dominance of cyanobacteria, with frequent blooms. In this study, we hypothesized that the biomass of cyanobacteria will be higher during the dry period and assessed toxic cyanobacteria and cyanotoxins in the Argemiro de Figueiredo Reservoir (Paraiba, Brazil). We conducted 22 samplings between August 2007 and July 2009 at three sites (PC, confluence of tributaries; PNC, net cages; and PD, dam site). Significant seasonal and spatial differences were not observed for abiotic variables; however, reduction in pH, electrical conductivity, alkalinity, and dissolved oxygen occurred only during overflow events in the reservoir. Filamentous cyanobacteria were dominant mainly in the dry period, accounting for 90 % of the total biomass; six of eight dominant or co-dominant species of cyanobacteria were observed to be potential producers of toxins. Planktothrix agardhii (Gomont) Anagnostidis & Komarek was dominant at PC, PNC, and PD and formed perennial blooms, and microcystin-LR was identified in 14 of 16 blooming events. Thus, we suggest that stable conditions, availability of nutrients, and a reduced light regime during the dry period favors blooms of cyanobacteria.

Adaptive strategies of desmids in two tropical monomictic lakes were studied in relation to morphometric differences. The study aimed at evaluating desmids' strategies during inter-annual succession patterns in two tropical lakes (Dom Helvecio and Carioca) in southeast Brazil. From monthly samples of freshwater algae collected during five consecutive years (2002–2006) from the two lakes, the desmids were classified according to size, life form, and life strategies (competitive, stress tolerant, and ruderal). Our results indicated that Lake Carioca (19o45′20″S, 42o37′12″W), a small, shallow, turbid, and mesotrophic system showed dominance of invasive/opportunistic taxa (C) and R-strategists (Staurastrum species 50 μm) and tolerant to stress (S) species (Staurastrum and Staurodesmus species >20 μm). A significant number of desmids from the lakes had low MLD (≤20 μm), low volume ( 1). Consequently, C-strategist species were abundant and formed a group having great adaptive value in the lakes, with higher resilience and capacity to change composition after the turnover period. Stratification stability and atelomixis were the main driving forces to sustain high desmid biomass in these two lakes, despite the greater macrophyte richness and great water column depth at Lake Dom Helvecio and the main factor influencing richness and contribution of complex forms.

The hydrological periods drive the structure and organization of aquatic communities in semiarid regions. We hypothesize that a decrease of the precipitation during the dry period will favor the development of the periphytic algal community, leading to higher richness and density in this period. To test this hypothesis, we investigated the changes in the periphytic algal community structure in three shallow and eutrophic ecosystems of the Brazilian semiarid. The sampling was performed between 2007 and 2010 at two-mensal intervals. The sampling of periphytic algal was performed in aquatic macrophytes and rocks. The abiotic variables were analyzed simultaneously. Dominance in diatoms, cyanobacteria and chlorophytes, respectively, was observed in two periods. In the dry period, waters were alkaline and had high concentrations of nitrate and total phosphorus associated with the highest densities of Bacillariophyceae. In the rainy period the water was warmer, oxygenated and high concentrations of ammonia and soluble reactive phosphorus with diatoms remained dominant but with reduced density, while cyanobacteria and chlorophytes increased. Overall, periphytic algal community composition no responded to changes in the hydrological periods. However, the hydrological periods altered the dynamics of periphytic algal community, supported by the alternation of the most representative classes (diatoms and cyanobacteria) between the hydrologic periods. Our data suggest that the morphometric and chemical and physical characteristics of lentic aquatic ecosystems studied were more important in the dynamics of periphytic algal community than the hydrological periods and types of substrates. Resumo Os períodos hidrológicos impulsionam a estrutura e organização das comunidades aquáticas em regiões semiáridas. Nós hipotetizamos que uma diminuição da precipitação durante o período seco irá favorecer o desenvolvimento da comunidade de algas perifíticas, levando a uma maior riqueza e densidade nesse período. Para testar esta hipótese, nós investigamos as mudanças na estrutura da comunidade de algas perifíticas em três ecossistemas rasos e eutróficos do semiárido brasileiro. As amostragens foram realizadas entre 2007 e 2010 em intervalos de bimensais. A amostragem das algas perifíticas foi realizada em macrófitas aquáticas e rochas. As variáveis abióticas foram analisadas simultaneamente. A dominância de diatomáceas, cianobactérias e clorófitas, respectivamente, foi observada em todos os períodos. No período seco, as águas foram alcalinas com altas concentrações de nitrato e fósforo total associado às maiores densidades de Bacillariophyceae. Durante o período chuvoso as águas apresentaram-se mais quentes, oxigenadas e com altas concentrações de amônia e fósforo reativo solúvel. As diatomáceas permaneceram dominantes, mas com densidade reduzida, enquanto as cianobactérias e clorofíceas aumentaram. No geral, a composição da comunidade de algas perifíticas não respondeu as mudanças nos períodos hidrológicos. No entanto, os períodos hidrológicos alteraram a dinâmica da comunidade de algas perifíticas, apoiados pela alternância das classes mais representativas (diatomáceas e cianobactérias) entre os períodos hidrológicos. Nossos dados sugerem que as características morfométricas, químicas e físicas dos ecossistemas aquáticos lênticos estudados foram mais importantes na dinâmica da comunidade de algas perifíticas do que os períodos hidrológicos e tipos de substratos.

Phytoplankton functional groups structure and species abundance vary according to environmental conditions. The present study investigated the natural and anthropogenic stressors that affect phytoplankton functional group biomass in a Brazilian semiarid region reservoir (Argemiro de Figueiredo reservoir). Sampling occurred between August 2007 and July 2009 on a bi-monthly basis for the first year, and in a monthly basis for the last two years. There were three collection points (PC: river confluence; PNC: near the cages; PD: dam site). The water environment analysis of abiotic variables included: temperature, transparency, coefficient of vertical light attenuation, dissolved oxygen, pH, electrical conductivity, alkalinity, dissolved inorganic nitrogen, and reactive soluble phosphorus. Phytoplankton samples were collected into a Van Dorn bottle, and were then preserved in acetic lugol and were quantified using an inverted microscope to determine phytoplankton density and biomass; the identified species were assembled in functional groups. The data were explored by canonical correspondence analysis. Individual analyses were made to test the temporal and spatial variability of the data and the factors that interfered most with the biotic and abiotic variables. Functional groups S1, SN, and K, consisting of filamentous Planktothrix agardhii (Gomont) Anagnostidis & Komárek, Cylindrospermopsis raciborskii (Woloszynska) Seenaya & Subba Raju, and the coccoid Aphanocapsa incerta (Lemmermann) Cronberg & Komárek, respectively, dominated the dry months when the water was warm, turbid, and alkaline. The overflow reservoir served as a natural disturbance reducing the phytoplankton biomass to less than 50 % and the dominance of cyanobacteria, promoting the domain of functional groups F, M, MP, Lo, and X2. The nutrient inputs from intensive fish farming, associated with a low local depth (Zmax = 7.7 m) close to the cages (PNC), resulted in a significant human disturbance that increased the prevalence of functional groups S1, SN, and K, which are composed primarily of cyanobacteria. We concluded that, in reservoirs, overflow events are natural disturbances that have the ability to reduce phytoplankton biomass and alter the structure of local communities, and that intensive fish farming is an anthropogenic disturbance that increases the availability of nutrients and stimulates an increase in biomass of the functional groups that include cyanobacteria. Furthermore, the functional groups of phytoplankton were reliable control of environmental conditions in the reservoirs of tropical semiarid regions. Rev. Biol. Trop. 65 (3): 1129-1141. Epub 2017 September 01. ResumenLa estructura de grupos funcionales del fitoplancton y la abundancia de especies varían de acuerdo con las condiciones ambientales. Este estudio investigó los estresores naturales y antropogénicos que afectan la biomasa de grupos funcionales de fitoplancton en una represa (la represa de Argemiro de Figueiredo) en una región semiárida de Brasil. La recolecta de datos fue entre agosto 2007 y julio 2009 de forma bimensual durante el primer año, y de forma mensual durante los últimos dos años. Estos se recolectaron en tres sitios (PC: confluencia del río; PNC: cerca de las jaulas; PD: sitio de la represa). El análisis de las variables abióticas del agua incluyó: temperatura, transparencia, coeficiente de atenuación vertical de la luz, oxígeno disuelto, pH, conductividad eléctrica, alcalinidad, nitrógeno inorgánico disuelto y fósforo reactivo soluble. Las muestras de fitoplancton fueron recolectadas en una botella Van Dorn, y fueron preservadas en lugol acético y cuantificadas utilizando un microscopio invertido para determinar la densidad y la biomasa del fitoplancton, las especies identificadas fueron agrupadas en grupos funcionales. Los datos fueron explorados mediante un análisis de correspondencia canónica. Los análisis individuales fueron hechos para probar la variabilidad espacial y temporal de los datos y los factores que más interfieren con las variables bióticas y abióticas. Los grupos funcionales S1, SN, y K, incluyen las algas filamentosas: Planktothrix agardhii (Gomont) Anagnostidis & Komárek, Cylindrospermopsis raciborskii (Woloszynska) Seenaya & Subba Raju, y algas cocoides: Aphanocapsa incerta (Lemmermann) Cronberg & Komárek, respectivamente dominando los meses cálidos cuando el agua estuvo caliente, turbia y alcalina. El desbordamiento de la reserva funciona como una alteración natural, reduciendo la biomasa del fitoplancton a menos de un 50 % y la dominancia de cianobacterias, promoviendo el dominio de los grupos funcionales F, M, MP, Lo y X2. La llegada de nutrientes debido a la pesca intensiva, asociado con una baja profundidad local (Zmax = 7.7 m), cerca de las jaulas (PNC), resulta en una alteración humana significativa que incrementa la prevalencia de los grupos funcionales S1, SN y K, los cuales están compuestos principalmente por cianobacterias. Concluimos que, en las represas, eventos de desborde son perturbaciones naturales que tienen la habilidad para reducir la biomasa del fitoplancton y alterar la estructura de las comunidades locales, y que la pesca intensa es una alteración antropogénica que incrementa la disponibilidad de nutrientes y estimula el incremento de la biomasa de los grupos funcionales que incluyen las cianobacterias. Además, los grupos funcionales de fitoplancton fueron controles confiables de las condiciones ambientales en las represas de las regiones semiáridas tropicales.

O presente estudo objetiva identificar os grupos funcionais e as espécies descritoras presentes em mesocosmos com piscicultura. O estudo foi realizado no período de janeiro a maio de 2010, com amostragens realizadas em intervalos quinzenais na subsuperfície. As variáveis abióticas obtidas foram: temperatura, transparência da água, zona eufótica, condutividade elétrica, oxigênio dissolvido, pH, n-amoniacal, nitrato, nitrito, fósforo total, fósforo reativo solúvel. Os grupos funcionais foram agrupadas com base nas características ecológicas/adaptativas. Os resultados demonstram que as condições ambientais presente nos mesocosmos favoreceram principalmente espécies R-estrategistas, que apresentam elevado MDL e adaptação às condições ambientais de corpos aquáticos do semiárido, dado seus baixos requerimentos de luz e por serem aptas a explorarem ambientes com águas misturadas. Os grupos funcionais refletiram as mudanças experimentadas pela comunidade algal, fornecendo importantes informações sobre a ecologia dos ambientes, sendo notória a presença de grupos típicos de lagos rasos eutróficos.

AIM: chemical stratification and the patterns of light limitation and nutrients of two natural lakes, one shallow and the other one deep, were comparatively evaluated, both lakes located in the southeast Brazil. METHODS: pH, electrical conductivity, dissolved oxygen, total dissolved solids and nutrients were monthly collected during 5 consecutive years at the vertical profile of the two lakes. RESULTS: multivariate analysis indicated that the long thermal stratification period favored the occurrence of chemical stratification in the two lakes. However, in the deeper lake the stratified thermal profile with high hypolimnetic nutrient concentration, electrical conductivity, total dissolved solids and redox potential indicated that the mixing was not complete even during the annual circulation period, suggesting a slight meromixis and a high chemical stability at the hypolimnion. In the shallower lake, high light attenuation and high availability of nitrogen forms (mainly N-NH4) and phosphorus was observed along the water column, even during stratification. In the deeper lake, N and P co-limitation and low light attenuation coefficients were detected. CONCLUSION: thermal and chemical stratification patterns indicated that the Carioca lake is a shallow, turbid, nutrient rich, whereas the Dom Helvecio lake is a deep, clear, oligotrophic system with a tendency towards meromixis and the isolation of solutes in the hypolimnion. Consequently, meromixis was compared to a "hypolimnetic memory", which was defined, in the case of the deeper lake, as the maintenance of the chemical stratification along the years, during the lake thermal circulation period. OBJETIVO: a estratificação química e os padrões de limitação por luz e nutrientes foram avaliados comparativamente em dois lagos naturais, sendo um raso e o outro profundo no sudeste do Brasil. MÉTODOS: as amostragens de pH, condutividade elétrica, oxigênio dissolvido, sólidos totais dissolvidos e nutrientes foram realizadas mensalmente, durante cinco anos consecutivos no perfil vertical dos dois lagos. RESULTADOS: as análises multivariadas indicaram que o longo período de estratificação térmica favoreceu a ocorrência de estratificação química nos dois lagos. No entanto, no lago mais profundo, o perfil térmico estratificado, com elevadas concentrações hipolimnéticas de nutrientes, condutividade, sólidos totais dissolvidos e potencial redox indicaram que a mistura não foi completa mesmo durante o período de circulação anual, sugerindo uma leve meromixia e alta estabilidade química no hipolímnio. No lago mais raso, elevada atenuação de luz e alta disponibilidade das formas nitrogenadas (principalmente N-NH4) e fosfatadas foram observadas em toda a coluna d'água, mesmo durante a estratificação. No lago mais profundo, foram observadas co-limitação por N e P e baixas coeficientes de atenuação da luz. CONCLUSÃO: os padrões de estratificação térmica e química indicaram que a lagoa Carioca é um lago raso, de rápida circulação com águas túrbidas, rico em nutrientes, enquanto o lago Dom Helvécio é um lago profundo, de águas claras, oligotrófico, com tendência à meromixia e ao isolamento de solutos no hipolímnio. Nesse contexto, a meromixia foi comparada a uma "memória hipolimnética" que foi definida, no caso do lago mais profundo, como a persistência da estratificação química ao longo dos anos durante o período de sua circulação térmica.

A floristic survey of the class Euglenophyceae in Panati Lake (7º11'14" S and 36º49'52" W) is presented. The samples were collected between November 2005 and April 2007 along the margins of the lake, and a total of 29 taxa were collected, described, and illustrated, comprising 11 specifics and 18 infraspecifics, with five typical and 13 non-typical varieties. The genus Trachelomonas showed the greatest richness (13 taxa), followed by the genus Lepocinclis (seven taxa). All of the 29 taxa cataloged had been previously reported for Brazil, most with wide geographical distributions, but all were new records for Paraíba State, and 25 new for northeastern Brazil - reflecting the need for more taxonomic studies of the Euglenophyceae in these locations.

O presente trabalho teve como objetivo caracterizar e estudar o comportamento germinativo das sementes de Bauhinia variegata L. var. candida e variegata, e Bauhinia forficata Link var. forficata. O delineamento foi inteiramente casualizado, com 4 repetições. Os tratamentos utilizados em Bauhinia variegata foram: água a 97 ºC até esfriar, água a 70 ºC durante 1 e 2 minutos, ácido sulfúrico durante 1, 2 e 3 minutos, escarificação mecânica e sementes intactas (controle); e em Bauhinia forficata, escarificação mecânica, imersão em ácido sulfúrico durante 5 e 10 minutos, armazenamento de sementes intactas durante seis meses, ácido sulfúrico durante 5 minutos e sementes recém-colhidas (controle). Tratamento com escarificação mecânica reduz a dormência das sementes de Bauhinia forficata e aumenta a porcentagem de germinação de Bauhinia variegata var. cândida e a velocidade de germinação das sementes Bauhinia variegata var. variegata. Tratamentos com ácido sulfúrico durante um minuto aumentam a velocidade de germinação das sementes Bauhinia variegata var. variegata e, por 10 minutos, reduzem os mecanismos de dormência das sementes de Bauhinia forficata. O armazenamento e a imersão das sementes de Bauhinia forficata Link var. forficata em ácido sulfúrico aumentam a germinação. A termoterapia a 97 ºC determina a morte das sementes de Bauhinia variegata var. variegata.

For many decades, polymorphism and its consequences have only been studied from the taxonomic point of view. Presently, interest has switched to the environmental causes of morphological variation and its consequences in the form and essence of the species. This study aimed at evaluating desmids morphological modifications of Staurastrum rotula Nordstedt during inter-annual succession patterns in two warm monomitic tropical lakes: Dom Helvécio (19°45′- 19°48′45″S, 42°33′45″W) and Carioca (19°45′20″S, 42°37′12″W). The effect of thermal stability and light and nutrients availability was based on samples collected monthly from January 2002 to December 2006 compared the morphological modifications. Results indicated that morphological variation, asexual reproduction, theratological forms, mucilaginous envelope and fungal infection were highest in Lake Dom Helvécio and coincided with the biomass increase of species with complex morphology between September and March (stratification period). The Zmix oscillation, wind and rainfall occurring at the end of the mixing period and beginning of the stratification were suggested as autochthonous and allochthonous disturbance agents, respectively, identified as inducers of asexual reproduction and consequently of the morphological variation. It was suggested that incidence of parasitism may act as a potential controlling agent for the Staurastrum rotula population size. It was concluded that morphological variation represents accidents in the original form, i.e. in the desmid species essence, promoting the existence of ecoforms, not of new infraspecific taxa.

CNPq - Conselho Nacional de Desenvolvimento Científico e Tecnológico FAPEMIG - Fundação de Amparo à Pesquisa do Estado de Minas Gerais CAPES - Coordenação de Aperfeiçoamento de Pessoal de Nível Superior Outra Agência Grande parte dos ambientes de água doce tropicais já enfrentaram algum tipo de distúrbio causado por ações antrópicas, como a eutrofização e a exploração desses recursos hídricos para captação de água utilizada na agricultura e pecuária, entre outros. Atualmente estes distúrbios estão sendo amplificados a medida que os efeitos das mudanças climáticas se fazem mais presentes, como as alterações nos padrões de chuva e na intensidade da luz solar incidente sobre o planeta, especialmente em ambientes tropicais. Tais alterações provocam consequências em todo o metabolismo e funcionamento aquático, assim como na estrutura das comunidades aquáticas. Neste contexto, é essencial o entendimento das alterações nos ciclos biogeoquímicos e nas comunidades planctônicas frente a estas mudanças ambientais. Desta forma, este trabalho teve como objetivos: 1) investigar, através de um experimento de mesocosmos in situ, a resposta das comunidades planctônicas frente a adição de nutrientes, matéria orgânica alóctone e sombreamento, e a interação destas adições, em um lago tropical (Lagoa Carioca, Médio Rio Doce, MG) circundado por Mata Atlântica; e 2) avaliar as mudanças em diferentes parâmetros da qualidade de água da lagoa Carioca após uma considerável perda de volume ocasionada por recentes mudanças nos padrões regionais de chuva. Nos mesocosmos, observamos respostas na composição do plâncton em poucos dias de experimento, com alterações na estrutura e densidade desta comunidade. A adição de nutrientes favoreceu a dominância de espécies fitoplanctônicas oportunistas, como Chlorella sp. e a adição de matéria orgânica ocasionou a substituição na dominância de Pseudanabaena catenata por Aphanocapsa elachista. Para o zooplâncton, houve a substituição da dominância do grupo Copepoda para Rotifera em todos os mesocosmos, e os grupos zooplanctônicos foram associados à transparência da água (coeficientes de atenuação difusa da radiação solar) e bacterioplâncton. A perda de volume do lago, por sua vez, causou impactos severos em muitos dos parâmetros observados. O lago se tornou menos transparente e com maiores concentrações de nutrientes na coluna d’água. Observou-se um aumento significativo na concentração de nitrogênio, nutriente essencial no processo de eutrofização. As propriedades ópticas indicaram que o escurecimento da lagoa parece ter ocorrido devido ao aumento na concentração de carbono orgânico dissolvido e pela entrada de matéria orgânica alóctone principalmente durante o verão, quando ocorre a entrada de grande quantidade de água nas fortes chuvas desta estação. Ainda assim, estas chuvas aconteceram sem periodicidade demarcada, e não foram suficientes para elevar os níveis de água perdidos pela lagoa durante a estação seca. Este estudo apresenta as modificações na qualidade da água e na estrutura e composição do plâncton frente a impactos frequentemente observados em lagos tropicais, como eutrofização, alterações no uso do solo (que alteram a qualidade e quantidade da matéria orgânica alóctone que entra nos ecossistemas aquáticos), e variabilidade na pluviosidade regional, que pode ser extrapolado para outros ambientes aquáticos e servir de subsídio para estratégias de conservação. The majority of freshwater ecosystems in the tropics have already faced disturbances caused by direct or indirect human actions, as eutrophication and exploitation of hydric resources to using water in agriculture or pasture, for example. Nowadays, those disturbances are becoming amplified with the increase of climate change effects, as changes in rain patterns, and the intensity of sunlight incident on the planet. Such modifications cause consequences in the metabolism and functioning of the lake. In this context, it is crucial the understanding of biogeochemical cycles alterations and plankton communities. Thus, this work aimed to: 1) investigate the response of planktonic communities through a mesocosms experiment with the addition of nutrients, allochthonous organic matter and shading, and the interaction of these additions in a tropical lake (Carioca Lake, Middle Rio Doce), surrounded by Atlantic forest; and 2) evaluate changes in different parameters of water quality of Carioca Lake after a considerable volume loss caused by recent changes in regional rain patterns. In mesocosms experiment, we observed responses in plankton composition after a few days of experiment, with alterations on structure and density of this community. The nutrients addition favored the dominance of phytoplankton opportunistic species, as Chlorella sp., and the organic matter addition provoked a substitution in dominance of Pseudanabaena catenata to Aphanocapsa elachista. In zooplankton, we observed the dominance substitution of Copepoda to Rotifera in all mesocosms, and the groups were associated with water transparency (diffuse attenuation coefficients of solar radiation) and bacterioplankton. On the other hand, the volume loss in the lake caused strong impacts in many of the observed parameters. The lake became less transparent and with higher nutrients concentrations in water column. We observed a significant increase in nitrogen concentration, essential nutrient in eutrophication process. The optical properties indicate that the lake darkening seems to occurred due to increasing on dissolved organic carbon concentration through the allochthonous organic matter input especially during summer, when the strong rains, common at this season, causes a massive water entrance, that also carries the organic material. Still, the rain events did not present a delimited frequency, and it was not enough to increase water levels that were lost by the lake during the dry season. This study presents the modifications in water quality and in structure and composition of planktonic community. The answers obtained in this work through simulation of eutrophication, land-use changes (that alters the quality and quantity of allochthonous organic matter in the system) and through observation on regional rainfall, can be extrapolated to development of aquatic environment conservation politics.

River damming for reservoir construction is fairly common in semi-arid regions, where water availability is limited, and constitutes a physical and chemical discontinuity affecting the ecological attributes of biological communities (Serial Descontinuity Concept theory, SDC). Modification in flow conditions, and consequently increase in residence time and matter sedimentation towards the dam region are among the main reservoir impacts in rivers. This variation may cause the development of distinct regions exhibiting different trophic and hydrodynamic characteristics, which may vary temporally, adversely influencing the establishment of biological communities. In this study, we evaluated longitudinal (lotic region upstream, transition, lacustrine region and lotic region downstream) and temporal (months without rainfalls and rainy months) variation in the attributes of the phytoplankton community (biovolume, trait abundance and functional diversity) in a river-reservoir system in Brazilian semi-arid as a function of environmental variables. Six monthly samplings were performed from October 2014 to March 2015 in eight sites. Two approaches were used: (1) spatial and temporal variation in the biovolume of phytoplankton morphology-based functional groups (MBFG) and (2) spatial and temporal variation in functional diversity and the trait abundance distribution in the studied system. A spatial gradient was recorded in which the lotic region upstream presented greater turbidity and had a greater predominance of MBFG V; The reservoir region was stratified and presented higher values of chlorophyll a and larger phytoplankton biovolume; MBFG VIII was dominant. The lotic region downstream presented higher water flow and phosphate concentration and was dominated by MBFGs VI, V and IV. The most important functional traits were aerotopes, brown pigments and flagella. The functional richness was higher in the reservoir, functional equitability did not varied according to regions and functional diversity (Rao) was lower in the reservoir. No significant temporal gradients were verified, probably due to the strong spatial gradients and pluviometric irregularities of the study period. The results indicate a discontinuity caused by the reservoir but the patterns observed in the functional diversity indices differ partially from those expected in relation to the SDC theory; this can be partialy explained by the intermittent characteristics of the semi-arid rivers, which cause a temporal discontinuity in these environments. O barramento de rios com a finalidade de construção de reservatórios de água é bem comum em regiões semiáridas, em que a disponibilidade de água é limitada, acarretando uma descontinuidade física e química que afeta os atributos ecológicos das comunidades biológicas (teoria do Conceito da Descontinuidade Serial, SDC). Um dos principais impactos de reservatórios em rios é a mudança no fluxo, e consequente aumento do tempo de retenção da água e da sedimentação de materiais em direção a barragem. Essa variação pode ocasionar a formação de distintas regiões com diferentes características tróficas e hidrodinâmicas, que podem variar temporalmente, e influenciar de forma diferenciada o estabelecimento das comunidades biológicas. Nesse estudo, foi avaliada a variação longitudinal (regiões lótica a montante, transição, lacustre e lótica a jusante) e temporal (meses com chuva e meses sem chuva) dos atributos da comunidade fitoplanctônica (biovolume, abundância de traços e diversidade funcional) em um sistema rio-reservatório, no Semiárido Brasileiro em função das variáveis ambientais. Foram realizadas seis coletas mensais no período de outubro de 2014 a março de 2015 em oito pontos amostrais. Foram utilizadas duas abordagens: (1) variação espacial e temporal do biovolume dos grupos morfológicos funcionais fitoplanctônicos (GFBMs) e (2) variação espacial e temporal da diversidade funcional e da distribuição da abundância de traços no sistema estudado. Foi registrado um gradiente espacial em que a região lótica a montante apresentou maior turbidez e teve maior predomínio do GFBM V; a região do reservatório apresentou-se estratificada e com maiores valores de clorofila a e maior biovolume fitoplanctônico; o GFBM VIII foi o dominante. A região lótica a justante apresentou maiores vazão e concentração de fosfato e foi dominada pelos GFBMs VI, V e IV. Os traços funcionais mais importantes foram os aerótopos, os pigmentos marrons e os flagelos, sendo que a riqueza funcional foi maior no reservatório, a equitabilidade funcional não variou conforme as regiões e a diversidade funcional (Rao) foi menor no reservatório. Não foram verificados gradientes temporais significativos, provavelmente em função dos fortes gradientes espaciais e da irregularidade pluviométrica do período de estudo. Os resultados indicam uma descontinuidade provocada pelo reservatório porém os padrões observados nos índices de diversidade funcional diferem em parte dos esperados em relação à teoria do SDC; isso que pode ser explicado em parte pelas características intermitentes dos rios do semiárido, que ocasionam uma descontinuidade temporal nesses ambientes. 75 f

A study was conducted concerning the interannual variability and persistence of phytoplankton species in a sub-basin of the upper Paraná River floodplain, which included a large temporal scale and several environments, during potamophasis and limnophasis periods. In the first, a long-term study was conducted, covering 12 hydrosedimentological cycles, on variability of phytoplankton biovolume and functional groups, involving the Baía River, a connected lake and a isloated lake. Was measured the influence of extreme hydrological periods, being one with a long limnophasis period and another one with a conspicuous potamophase, we analyzed the effects of these periods on the phytoplankton variability and persistence in the Baía River basin. Was evaluated the distribution and spatiotemporal dominance of cyanobacteria populations during two hydrosedimentological cycles, in the Baía river, in four connected lakes, four isolated lakes and two active channels. Established that the stability and temporal variability of biovolume and functional groups were linked to seasonal and interannual variability of limnophasis and potamophasis periods, which in turn, were related to long-term effects of climate variability and anthropogenic events. The results showed that the extension of limnophasis decresead the phytoplankton richness and influenced the pattern of dominance and persistence of species. There was also an increase of cyanobacteria in the sub-basin of the Baía River due to the lower connectivity of habitat and the highest concentrations of nutrients during limnophasis. Realizou-se um estudo acerca da variabilidade interanual e da persistência de espécies fitoplanctônicas em uma sub-bacia da planície de inundação do alto rio Paraná, que incluiu uma ampla escala temporal e diversos ambientes, durante períodos de potamofase e limnofase. Sobre as abordagens do estudo, inicialmente foi avaliado um estudo de longa duração, abrangendo 12 ciclos hidrossedimentológicos, sobre a variabilidade do biovolume e dos grupos funcionais fitoplanctônicos, envolvendo o rio Baía, um lago conectado e um lago sem conexão; A avaliação da influência de períodos hidrológicos extremos, sendo um longo período de limnofase e outro com potamofase conspícua, e analisada seus efeitos sobre a variabilidade e persistência fitoplanctônica no rio Baía, em um lago conectado e um lago sem conexão e a distribuição e dominância espaço-temporal das populações de cianobactérias durante dois ciclos hidrossedimentológicos, no rio Baía, em quatro lagos conectados, quatro lagos sem conexão e dois canais ativos. Estabeleceu-se que a estabilidade e a variabilidade temporal do biovolume e dos GFs estiveram ligadas à variabilidade sazonal e interanual dos períodos de limnofase e potamofase, que por sua vez, estiveram relacionados aos efeitos em longo prazo da variabilidade dos eventos climáticos e antropogênicos. Acrescentou que o prolongamento da limnofase interferiu negativamente na riqueza fitoplanctônica e influenciou o padrão de dominância e persistência das espécies. Observou a tendência de aumento de cianobactérias na sub-bacia do rio Baía em função da menor conectividade dos habitat e das maiores concentrações de nutrientes durante a limnofase. 109 f