Natalia Felix Negreiros

O estado atual do conhecimento da diversidade dos Cladocera (Crustacea, Branchiopoda) nas águas doces do estado de Minas Gerais

O objetivo do presente trabalho e apresentar uma check list atualizada dos registros existentes para especies de Cladocera nas aguas doces do Estado de Minas Gerais que possa servir de base para os estudos em andamento ou estudos futuros dentro do escopo do Programa Biota Minas. O trabalho baseia-se numa extensa revisao da literatura incluindo recentes revisoes taxonomicas, particularmente para alguns generos da familia Chydoridae. O levantamento realizado evidenciou a ocorrencia de 94 especies de Cladocera, distribuidos em 88 corpos de agua no estado de Minas Gerais. Estes cladoceros incluem representantes de 35 generos pertencentes a 7 das 8 familias com ocorrencia nas aguas doces da regiao Neotropical. Para os Cladocera em geral, a familia com maior riqueza foi a Chydoridae (Ordem Anomopoda) com um total de 47 especies registradas, correspondendo a 50% da riqueza total dos Cladocera. As demais familias, em ordem decrescente em relacao a riqueza de especies foram Daphnidae com 16, Macrothricidae com 9, Sididae e Bosminidae com 8 especies cada, Moinidae e Ilyocryptidae com 3 especies cada. Em relacao a ocorrencia nas bacias hidrograficas do estado de Minas Gerais, os dados obtidos evidenciaram registros de especies de cladoceros em 6 das 8 bacias principais. Contudo nao ha qualquer registro para as bacias dos rios Mucuri e Paraiba do Sul. Observa-se que a maior riqueza de especies de Cladocera em algumas bacias hidrograficas como as bacias do Rio Doce com 67 especies, e a bacia do Rio Grande com 65 especies resulta muito provavelmente do maior numero de estudos realizados nas mesmas, e que por outro lado, bacias com baixa riqueza de Cladocera como as bacias do rio Pardo (9 especies) e do Rio Jequitinhonha (3 especies) ou com nenhuma ocorrencia registrada (bacias do rio Mucuri e do rio Paraiba do Sul) resultam de poucos, ou nenhum estudo, respectivamente. Conclui-se que ha necessidade de ampliacao da cobertura geografica para amostragem de corpos de agua em outras bacias, particularmente aquelas localizadas na regiao norte e nordeste do estado de Minas Gerais.

Biomass and production of Cladocera in Furnas Reservoir, Minas Gerais, Brazil

Secondary production of zooplankton, the main energy pathway in many aquatic ecosystems, is crucial to an Understanding of functioning of these systems function. In this study, we analyzed the magnitude and seasonal variations of the population density, biomass and secondary production of Cladocera in the Furnas Reservoir (Brazil). Samples were carried out monthly at 6 points in the reservoir, from August 2006 to July 2007. Main physical and chemical variables in the water column were measured in situ. Data on density, biomass and development times were obtained and used to calculate the secondary production of eight Cladocera species. The total production of Cladocera varied from 0.02 to 28.6 mgDWm-3.day-1, among the sampling sites. The highest values were recorded in spring and summer months (September to January), and were correlated to the increase in the biomass of the phytoplankton. The mean production:biomass ratio was 0.32. The level of production in Furnas Reservoir fell within the range of those reported in the literature and was of the same order of magnitude of the production values recorded for oligotrophic reservoirs. Cladocera production differed spatially inside the Sapucaí compartment and also in the temporal scale, seasonally.

Short-term thermal stratification and partial overturning events in a warm polymictic reservoir: effects on distribution of phytoplankton community

In lentic freshwater ecosystems, patterns of thermal stratification play a considerable part in determining the population dynamics of phytoplankton. In this study we investigated how these thermal patterns and the associated hydrodynamic processes affect the vertical distribution of phytoplankton during two consecutive diel cycles in a warm polymictic urban reservoir in the metropolitan region of São Paulo, Brazil. Water samples were taken and physical, chemical and biological data collected at half-meter intervals of depth along a water column at a fixed site, every 3 hours throughout the 48-hour period. Two events of stratification, followed by deepening of the thermocline occurred during the study period and led to changes in the vertical distribution of phytoplankton populations. Aphanocapsa delicatissima Nägeli was the single dominant species throughout the 48-hour period. In the second diel cycle, the density gradient induced by temperature differences avoided the sedimentation of Mougeotia sp. C. Agardh to the deepest layers. On the other hand, Pseudanabaena galeata Böcher remained in the 4.0-5.5 m deep layer. The thermal structure of the water was directly affected by two meteorological factors: air temperature and wind speed. Changes in the cell density and vertical distribution of the phytoplankton were controlled by the thermal and hydrodynamic events.

The influence of environmental factors on the seasonal dynamics and composition of Rotifera in the Sapucaí River arm of Furnas Reservoir, MG, Brazil

Seasonal fluctuations in the dynamics of the plankton rotifer populations in an oligo-mesotrophic branch of a tropical reservoir were analyzed with respect to the possible influence of environmental conditions (physical, chemical and biological), with emphasis on biological interactions. Samples were taken monthly from August 2006 to July 2007. The well-defined climatic seasons were reflected in variations of the physical and chemical properties of the water. The zooplankton community consisted mainly of Rotifera, Cladocera and Copepoda, with occasional representatives of Chaoborus brasiliensis (Diptera), Ostracoda, Protozoa and Turbellaria. Rotifera was the dominant group in zooplankton community in 5 of the 12 months of the study and were represented by 35 taxa. Redundancy analysis between the rotifer population abundances and the set of environmental variables showed significant (p < 0.05) positive correlations with the chlorophyll a in the rainy season. In the dry period, predation was probably the environmental factor that had the strongest effect on rotifer populations; in particular, the density of the cyclopoid Thermocyclops decipiens showed significant (p < 0.05) negative correlations with many of the rotifer population abundances. In addition, analysis of the co-occurrence of different rotifer species indicated strong competitive interactions between populations, during the rainy period (p < 0.001). Among the biotic environmental factors analyzed, algal biomass had an important role during the rainy period and inter-rotifer competition was also significant in these months. It was probably that predation by the cyclopoid copepod Thermocyclops decipiens determined the structure and dynamics of the rotifer populations in the Sapucai arm of the Furnas reservoir, during the dry period.

Influence of environmental quality of the tributaries of the Monjolinho River on the relative condition factor (Kn) of the local ichthyofauna

The relative condition factors (Kn) of the fishes Astyanax paranae, Phalloceros harpagos and Poecilia reticulata were used as a means of assessing the influence of environmental conditions on the well-being of sub - populations of these species, with the eventual aim of using them as bioindicators of disturbance in tributary streams of the Monjolinho River, in Sao Carlos - SP. The power-law curve generated by the length-weight relationship indicated a positive allometric growth for the three species studied. Overall, the canonical correspondence analysis (CCA) positively correlated average Kn of A. paranae with well oxygenated and oligotrophic environments, typical of conserved areas or near the natural state. For the average value of Kn obtained for Phalloceros harpagosspecies, there was no significant difference between natural and disturbed areas. However, the CCA positively correlated the mean Kn of the speciesP. reticulata from similar environments with higher trophic level, suggesting that this species is indicative of disturbance.

A search for predators and food selectivity of two native species of Hydra (Cnidaria: Hydrozoa) from Brazil

The Hydra is the most common representative of freshwater cnidarians. In general, it is found in freshwaters on every continent, with the exception of Antarctica. The aim of the present study is to gather biological and ecological data on aspects of two species of Hydra native to Brazil: Hydra viridissima and Hydra salmacidis. Predation and food selectivity experiments were performed to assess the possible predators and the prey preferences, respectively, of the two species. The results indicate that the two species of Hydra were not consumed by any of the predators that were tested, which are typical predators of invertebrates in freshwater: nymphs of Odonata Anisoptera and the phantom midge larvae of Chaoborus sp. (Insecta), adults of Copepoda Cyclopoida (Crustacea) and the small fish Poecilia reticulata. It was observed that the smaller Hydra, H. viridissima, positively selected the nauplii and copepodites of calanoid copepods and small cladocerans and rejected large prey, such as the adults of calanoid copepods and ostracods. The larger H. salmacidis, besides the nauplii and copepodites of the calanoid copepods and small cladocerans, also positively selected the large adults of the calanoid copepods. It can be concluded that both H. viridissima and H. salmacidis are most likely preyed on little or not preyed on at all in many freshwater bodies, as they are top predators in the food chain. At the same time, they are efficient predators, and a positive relationship was observed between the prey size and the Hydra species size. Food selectivity was related to prey size as well as other prey characteristics, such as carapace thickness and swimming efficiency.

Synchaeta jollyae (Shiel & Koste) (Rotifera, Synchaetidae): an overlooked species or a newcomer in Neotropical freshwaters?

Populations of Synchaeta jollyae (Shiel & Koste, 1993) (Rotifera), a species recently recorded for the first time in Brazil and South America, were analyzed in reservoirs in Southeast Brazil. Sampling was carried out monthly from August 2006 to July 2007 at Furnas Reservoir in the Rio Grande basin, state of Minas Gerais, and in four cascade reservoirs in the Tiete River basin (Barra Bonita, Bariri, Ibitinga and Nova Avanhandava) state of Sao Paulo, in June and September 2008 and in January and May 2009. Synchaeta jollyae occurred in most samples and periods. From the results obtained it is evident that S. jollyae occurs in water bodies of varied trophic status but reaches larger populations in eutrophic water bodies and during lower temperature periods. The greatest densities of S. jollyae were found in the eutrophic Bariri Reservoir, on the Tiete River, during the winter. Mann-Whitney test confirmed the significant difference between the population densities in periods of high and low temperatures, with populations reaching higher densities at lower temperatures. It is not yet possible to tell whether S. jollyae is a widely distributed species that has been overlooked in previous plankton studies in South America. Wherever these populations of S. jollyae might have originated, it appears to be a species well established and adapted to a wide range of conditions in the Neotropics.

COMPOSIÇÃO E BIOMASSA DA COMUNIDADE ZOOPLANCTÔNICA NO CANAL CUNIÃ, BACIA DO RIO MADEIRA, AMAZÔNIA

Os corpos de agua na Amazonia estao sujeitos a grandes flutuacoes no nivel de agua. Esses pulsos influenciam diretamente a composicao e abundância da comunidade zooplanctonica presente nesse ambiente. Dessa forma, o presente estudo teve como objetivo avaliar a composicao, riqueza, abundância, diversidade e biomassa das flutuacoes temporais (periodo de vazante e aguas baixas) da comunidade zooplanctonica no Canal Cunia. As amostragens foram realizadas em dois pontos no Canal Cunia nos meses de junho (vazante) e outubro (aguas baixas) de 2012. A coleta do zooplâncton foi realizada com motobomba e filtracao em rede de plâncton de 68 µm de abertura de malha. Ainda foram mensuradas as variaveis: temperatura da agua, condutividade, pH, transparencia, nutrientes totais e dissolvidos e clorofila a. Foram registradas um total de 41 especies, sendo Rotifera, o grupo com maior representatividade (16 especies) seguido por Cladocera (13 especies) e Protozoarios com 9 especies e Copepoda com quatro. Os resultados das analises das variaveis fisicas, quimicas e biologicas da agua nos dois pontos do Canal Cunia estao dentro da faixa de adequabilidade para o estabelecimento de uma comunidade zooplanctonica rica e abundante. Dentre as especies de Calanoida registradas, Rhacodiaptomus insolititus e tipica e endemica da Regiao Amazonica. Registrou-se uma variacao espacial da comunidade zooplanctonica, onde no ponto CC.02 foram registrados os maiores valores tanto de riqueza de especies quanto de densidade e biomassa. No entanto, nao se verificou uma influencia dos periodos hidrologicos na estrutura do zooplâncton do Canal Cunia. PALAVRAS-CHAVE : Riqueza de especies. Microcrustaceos. Variacao espacial. COMPOSITION AND BIOMASS ZOOPLANKTON COMMUNITY IN CUNIA WATERWAY, MADEIRA RIVER BASIN, AMAZONIA ABSTRACT The Amazonia water bodies are subject to large fluctuations in water level. These pulses directly influence the composition and abundance of zooplankton present in this environment. Thus, the present study aimed to evaluate the composition, richness, abundance, diversity and biomass of temporal fluctuations (period of ebbing and low water) of the zooplankton community in the Cunia Waterway. Samples were taken at two points in Cunia Waterway in June (ebbing) and October (low water) 2012. The sampling of zooplankton was performed with pump and filtration of plankton opening of 68 µm in mesh network. Although the variables were measured: water temperature, conductivity, pH, transparency, total and dissolved nutrients and chlorophyll a. In A total of 41 species were recorded, with rotifers like the group largest representation (16 species) followed by Cladocera (13 species) and Protozoa with nine and Copepoda with four species. The results of the analysis of physical, chemical and biological variables of the water in the two points in Cunia Waterway are within the range of suitability for establishing a rich and abundant zooplankton community. Among the calanoids species recorded, Rhacodiaptomus insolititus is typical and endemic to the Amazon region. Spatial variation of zooplanktonic community was recorded, where in the point CC.02 there were highest values of both species richness as density and biomass. However, there wasn’t recorded an influence of hydrological periods in the structure of zooplankton Cunia Waterway. KEY-WORDS : Species richness. Microcrustaceans. Spatial variation COMPOSICION Y COMUNIDAD EN zooplancton BIOMASA Cunia CANAL, MADERA DE CUENCA, AMAZON RESUMEN Los cuerpos de agua en el Amazonas estan sujetos a grandes fluctuaciones en el nivel del agua. Estos pulsos influyen directamente en la composicion y abundancia de zooplancton presente en este entorno. Por lo tanto, este estudio tuvo como objetivo evaluar la composicion, riqueza, abundancia, diversidad y biomasa de las fluctuaciones temporales (periodo de flujo y bajo el agua) de la comunidad de zooplancton en el Canal Cunia. Las muestras se recogieron en dos puntos en el Canal Cunia en junio (EBB) y octubre (bajo el agua) de 2012. La coleccion de zooplancton se realizo con bomba y filtracion red de plancton de 68 micras de malla de ancho. Aunque se midieron las variables: temperatura del agua, conductividad, pH, transparencia, totales y disueltos nutrientes y clorofila a. Un total de 41 especies se registraron, con rotiferos, el grupo con mayor representacion (16 especies), seguido de Cladocera (13 especies) y protozoos con 9 especies y Copepoda con cuatro. Los resultados del analisis de las variables fisicas, quimicas y biologicas del agua en el colon Canal Cunia estan dentro del rango de idoneidad para el establecimiento de una comunidad de zooplancton rica y abundante. Entre los calanoides registrados, Rhacodiaptomus insolititus es tipico y endemico de la region amazonica. Variacion espacial registrada de la comunidad de zooplancton, donde el punto CC.02 los valores mas altos de ambos riqueza de especies como la densidad y la biomasa se registraron. Sin embargo, hubo una influencia de los periodos hidrologicos en la estructura del zooplancton Canal Cunia. PALABRAS-CLAVE: La riqueza de especies. Microcrustaceos. La variacion espacial.

ZOOPLÂNCTON DE UM LAGO URBANO DOMINADO PELA MACRÓFITA PISTIA STRATIOTES L. (ARACEAE)

Os lagos urbanos estao submetidos a grandes impactos causados pelas atividades antropicas desenvolvidas no seu entorno, o que geralmente causa impacto sobre o corpo d’agua, entre estes estao as floracoes de cianobacterias e de macrofitas aquaticas. A distribuicao e estrutura do zooplâncton em ecossistemas de agua doce sao influenciadas pelo tipo de habitat, em especial quando criado por varias especies de macrofitas. Este rapido inventario tem como objetivo analisar qualitativa e quantitativamente a comunidade zooplanctonica que caracteriza o Lago do Parque Ecologico do Baguacu, a fim de complementar a avaliacao da qualidade da agua e detectar os efeitos das macrofitas sobre esta comunidade. Foram registradas as medidas da temperatura da agua, pH, condutividade, transparencia da agua. A concentracao de clorofila a foi determinada pelo metodo de extracao com acetona 90% a frio. O zooplâncton foi amostrado com rede de plâncton. As amostras foram fixadas com formol na concentracao final 4% e os organismos foram identificados e contados, calculando-se entao a densidade e os indices de diversidade, dominância e equitabilidade. Foram identificadas 31 especies, sendo que para Protozoa foi registrado a maior riqueza (13 especies), Rotifera e Meroplâncton (7 especies cada) e Copepoda e Cladocera (2 especies cada). A analise da comunidade zooplanctonica do Lago do PEBA revelou um padrao diferenciado na abundância e diversidade de especies para os distintos grupos taxonomicos. Os protozoarios e rotiferos dominaram tanto em termos de riqueza quanto em densidade, sendo estes favorecidos pelo micro-habitat proporcionado pelas macrofitas.