ABSTRACT:The relationship between the trophic state of 39 reservoirs located in the semi-arid region of north-east Brazil and their planktonic structure was examined by a sampling survey during the 1998 drought (September to November). A total of 30 environmental and biological parameters, with special attention paid to phytoplankton, were studied once at each reservoir to obtain a synoptic view at a state scale (Pernambuco State). The application of the chlorophyll a-total phosphorus standard relationship for grades of eutrophication revealed a classification in which 90% of the sites were eutrophic-hypertrophic. Among the 202 taxa identified in the phytoplankton assemblages, the cyanobacterium Cylindrospermopsis (Wolsz.) Seenayya et Subba Raju represented more than 80% of the total phytoplankton density in 10 reservoirs and more than 50% in 17 reservoirs. The rarity of other phytoplanktonic groups in the case of the Cylindrospermopsis dominance is the most significant biological feature of these reservoirs. Although rotifers were more closely linked to hypereutrophic conditions than copepods or cladocerans, this dominant group did not seem to play an efficient role in cyanobacterial control. A statistical approach based on the analysis of cross tables (co-inertia analysis) allows us to describe species-environment relationships with a special focus on the factors governing the presence of Cylindrospermopsis. As determined by hierarchical analysis, a major group of studied reservoirs (70%) corresponded to deeper, warmer and hypertrophic reservoirs characterized by the combination of (1) low ammonia concentration, high temperature and pH values, and (2) high percentages of Cylindrospermopsis abundances. Lack of water renewal in 1998 linked to the 1997 El Niño consequences seems to be a major determinant for both trophic conditions and Cylindrospermopsis dominance in the reservoirs studied.KEY WORDS: Bacteria · Phytoplankton · Zooplankton · Cylindrospermopsis · El Niño event · Reservoirs · Co-inertia analysis Resale or republication not permitted without written consent of the publisherAquat Microb Ecol 23: [13][14][15][16][17][18][19][20][21][22][23][24][25][26][27] 2000 Cyanobacteria are recognized as a critical problem worldwide and their blooms are typical phenomena in eutrophic lakes, often linked to external nutrient enrichment (Paerl 1988). The influence of local climatological factors (e.g. wind, light intensity, temperature) can accelerate these phenomena and modify the phytoplankton structure, as cyanobacteria are strongly driven by physical factors such as local weather conditions (e.g. Tóth & Padisák 1986, Fabbro & Duivenvoorden 1996. Other factors that potentially influence the biomass and composition of phytoplankton include a stable water column with a turbulence limitation defined as a high ratio between the mixing zone and the euphotic zone (Soranno 1997). In addition, cyanobacteria are inedible prey for many zooplankton organisms because of their large colony size, their toxic effects and low...

-(Inter-annual variations in the floristic and population structure of an herbaceous community of "caatinga" in Pernambuco, Brazil). The influence of climatic variations on the herbaceous component of the "caatinga" vegetation was examined in the state of Pernambuco, Brazil. A total of 105 1 × 1 m-plots were established, of which 35 were in a level micro-habitat, 35 in a riparian micro-habitat, and 35 in a stony microhabitat. During two consecutive years all herbaceous plants in these plots were counted, measured (height and diameter), and collected for identification. The Shannon-Wiener diversity index and the equitability were calculated for each year, as well as the density, frequency, dominance, total basal area and importance index for each species. The total annual pluviometric was 819.5 and 448.8 mm in 2002 and 2003, respectively. The herbaceous flora in the study area was composed of 71 species, of which 58 were sampled in the plots. The families with the greatest species richness were Malvaceae (8 species), Euphorbiaceae (7), Poaceae (6), Convolvulaceae (4), Fabaceae (4), and Portulacaceae (4). The diversity indices were 2.66 and 3.01 nats ind -1 in 2002 and 2003, respectively. The density, frequency, dominance and importance value of herbaceous populations, as well as, the height and diameter of plants were low in the dryer year. The riparian group was the most isolated of the microhabitats examined, both in terms of its floristic and its population structure. Annual seasonal climatic variations greatly modified these populations structure during the course of this study, emphasizing the fact that longterm studies are needed in order to better understand the dynamics of the herbaceous component of the "caatinga" vegetation.Key words -"caatinga", herbaceous component, phytosociology, seasonal climate changes, species richness RESUMO -(Variações interanuais na composição florística e estrutura das populações de uma comunidade herbácea da caatinga, Pernambuco, Brasil). Objetivou-se avaliar a influência das variações climáticas sobre o componente herbáceo em uma área de caatinga de Pernambuco. Foram estabelecidas 105 parcelas de 1 × 1 m, sendo 35 dispostas em micro-habitat plano, 35 em micro-habitat ciliar e 35 em micro-habitat rochoso. Durante dois anos consecutivos todas as ervas presentes nas parcelas foram contadas, medidas (altura e diâmetro) e coletadas para identificação taxonômica. Foram calculados o índice de diversidade Shannon-Wiener, a equabilidade e os parâmetros de densidade, freqüência, dominância, área basal total e índice de valor de importância. A precipitação pluviométrica anual registrada foi de 819,5 e 448,8 mm em 2002 e 2003, respectivamente. A flora herbácea registrada nas parcelas e fora delas foi representada por 71 espécies, sendo 58 amostradas. As famílias de maior riqueza de espécies foram Malvaceae (8), Euphorbiaceae (7), Poaceae (6), Convolvulaceae (4), Fabaceae (4) e Portulacaceae (4). As diversidades foram de 2,66 e 3,01 nats ind -1 em 2002 e 2003, respectivamente. ...

Brazil has a history of blooms and contamination of freshwater systems by cyanobacterial toxins. The monitoring relevance of toxins from cyanobacteria in reservoirs for public supply is notorious given its high toxicity to mammals, included humans beings. The most recurrent toxins in Brazilian water bodies are microcystins (MC). However, the recent record of cylindrospermopsin (CyN) in northeastern Brazil, Pernambuco state, alerts us to the possibility that this could be escalating. This study reports occurrence of MC and CYN, quantified with ELISA, in 10 reservoirs, devoted to public drinking supply in northeastern Brazil. The composition and quantification of the cyanobacteria community associated with these water bodies is also presented. From 23 samples investigated for the presence of MC, and CyN, 22 and 8 out were positive, respectively. Considering the similarity of the cyanobacteria communities found in reservoirs from Pernambuco, including toxin-producing species associated to MC and CyN, we suggest that geographic spreading can be favored by these factors. These issues emphasize the need for increased monitoring of MC and CyN in drinking supply reservoirs in Brazil.

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RESUMO -(Associações fitoplanctônicas: uma ferramenta para entendimento de eventos de dominância em um reservatório tropical brasileiro). O objetivo deste estudo foi caracterizar as associações fitoplanctônicas, bem como discutir os fatores controladores determinantes da dominância algal em um reservatório eutrófico, Mundaú, Pernambuco, Brasil. As amostras foram coletadas durante dois períodos sazonais, seco (janeiro/2005) e chuvoso (junho/2005). As amostras foram coletadas nas regiões limnética e litorânea, seguidas pela identificação através de literatura específica, e preservadas com formol a 4%. No mesmo momento das coletas dos dados bióticos, alguns parâmetros abióticos como temperatura e transparência da água, oxigênio dissolvido, pH foram obtidos e, em laboratório, foram determinados o fósforo total, nitrogênio total e o Índice de Estado trófico. Os agrupamentos das associações fitoplanctônicas foram feitos a partir da classificação fitossociológica de Reynolds. O reservatório esteve limitado por nitrogênio em ambos os períodos sazonais. No período seco, este sistema apresentou água pouco oxigenada, pH alcalino e relativa turbidez quando comparado com o período chuvoso. O fitoplâncton foi representado por 70 táxons infragenéricos agrupados em 16 associações, sendo a maioria, típica de ecossistemas eutróficos. Este fato é corroborado pela análise quantitativa, os quais evidenciam a dominância de associações S, constituídas exclusivamente por cianobactérias R-estrategistas. Palavras-chave: associações fitoplanctônicas, reservatórios abastecimento d'água, nordeste do BrasilABSTRACT -(Phytoplanktonic associations: a tool to understanding dominance events in a tropical Brazilian reservoir). The aim of this study was to characterize phytoplankton associations, as well as discuss controlling factors determining algal dominance in a eutrophic tropical reservoir, Mundaú, Pernambuco, Brazil. Water samples were collected during the dry period (January/2005) and the rainy period (June/2005). The samples were collected from both limnetic and littoral regions, and the phytoplankton assemblages identified from current literature after preservation in formaldehyde 4%. At the same time as sampling was done, in situ measurements of water temperature, transparency, dissolved oxygen, and pH were also taken. Total phosphorus, total nitrogen concentration and the Trophic State Index were subsequently determined in the laboratory. Phytoplankton density (ind. L -1 ) was estimated using an inverted Zeiss microscope. Grouping of the phytoplankton associations was carried out using the Reynolds phytosociological classification. During the dry period, reservoir water showed low dissolved oxygen concentrations, alkaline pH and was relatively turbid compared to the situation during the rainy season. Reservoir water is limited by nitrogen during both seasonal periods. The Trophic State Index is classified as determining eutrophic conditions. Phytoplankton was represented by 70 infrageneric taxa grouped in 16 functional associations, wi...

This study analysed vertical and temporal variations of cyanobacteria in a potable water supply in northeastern Brazil. Samples were collected from four reservoir depths in the four months; September and December 2007; and March and June 2008. The water samples for the determination of nutrients and cyanobacteria were collected using a horizontal van Dorn bottle. The samples were preserved in 4% formaldehyde for taxonomic analysis using an optical microscope, and water aliquots were preserved in acetic Lugol solution for determination of density using an inverted microscope. High water temperatures, alkaline pH, low transparency, high phosphorous content and limited nitrogen content were found throughout the study. Dissolved oxygen stratification occurred throughout the study period whereas temperature stratification occurred in all sampling months, with the exception of June. No significant vertical differences were recorded for turbidity or total and dissolved forms of nutrients. There were high levels of biomass arising from Planktothrix agardhii, Cylindrospermopsis raciborskii, Geitlerinema amphibium and Pseudanabaena catenata. The study demonstrates that, in a tropical eutrophic environment with high temperatures throughout the water column, perennial multi-species cyanobacterial blooms, formed by species capable of regulating their position in the water column (those that have gas vesicles for buoyancy), are dominant in the photic and aphotic strata.

In estuarine systems, the distribution, composition and density of phytoplanktonic populations, their seasonal and spatial variations are controlled mainly by factors such as tolerance to salinity, luminosity, nutrients and grazing (Kinne, 1970;Santelices, 1977). The geomorphologic characteristics, the anthropogenic impacts and the variations in the weather conditions are other Determination of eutrophic areas in Mundaú/Manguaba lagoons, Alagoas-Brazil, through studies of the phytoplanktonic community Melo-Magalhães, EM.*, Medeiros, PRP., Lira, MCA., Koening, ML. and AbstractMundaú and Manguaba Lagoons (9° 34' 38"-9° 45' 30" S and 35° 44' 00"-35° 58' 13" W) are considered the largest and most productive ones in the state of Alagoas and were studied with the purpose of identifying the existence of anthropic impacts. Samples were collected at 8 stations, during low tide and flooding in rainy and dry periods, using the "Van Dorn" bottle and plankton net. In total, 155 taxons were identified, with special emphasis on Bacillariophyta and Cyanophyta divisions. The most abundant species in Mundaú Lagoon was Skeletonema cf. costatum, and in the Manguaba Lagoon, Cyclotella meneghiniana, Microcystis aeruginosa and Anabaena spiroides. The diversity ranged from 0.17 bits cell/L to 4.81 bits cell/L. The predominance of freshwater species (51%), evidenced higher influence of the limnetic flow on the two environments studied. The high values related to the phytoplanktonic density characterize the lagoons as strongly impacted environments, indicating the existence of eutrophic conditions in most of the studied stations.Keywords: phytoplankton, ecology, density, Mundaú/Manguaba lagoons. Determinação de áreas eutróficas nas lagoas Mundaú e Manguaba, Alagoas-Brasil, através de estudos com a comunidade fitoplanctônica ResumoAs lagunas Mundaú e Manguaba (9° 34' 38"-9° 45' 30" S e 35° 44' 00"-35° 58' 13" W) são consideradas as maiores e mais produtivas do Estado de Alagoas e foram estudadas com o objetivo de identificar a existência de impactos antrópicos, nos períodos chuvoso e seco, com base na composição, diversidade e densidade fitoplanctônica. Coletas de material fitoplanctônico foram realizadas em 8 estações fixas, durante maré vazante e enchente nos períodos chuvoso e seco. As amostras foram coletadas com garrafa de "Van Dorn" e rede de plâncton. Foram identificados 155 táxons destacando-se as divisões Bacillariophyta e Cyanophyta. A espécie mais abundante na laguna Mundaú foi Skeletonema cf. costatum; na laguna Manguaba foram Cyclotella meneghiniana, Microcystis aeruginosa e Anabaena spiroides. A diversidade oscilou ente 0,17 bits cell/L e 4,81 bits cell/L. A predominância de espécies dulciaquícolas, (51%) evidenciou maior influência do fluxo limnético nos dois ambientes estudados. Os altos valores da densidade fitoplanctônica caracterizam as lagunas como ambientes fortemente impactados, indicando a existência de condições eutróficas na maioria das estações estudadas.Palavras-chave: fitoplâncton, ecologia, densidade, lagun...