Investigações limnológicas e ictiológicas em Curuá-Una, a primeira represa hidrelétrica na Amazônia Central

Curuâ-Una Reservoir is the first hydrelectric clam of the Amazon basin and is being studied by the Instituto Nacional de Pesquisas da Amazonia (INPA), Manaus, in agreement with the Centrais Elétricas Brasileiras S/A (ELETROBRAS) and the Centrais Elétricas do Pará (CELPA). Analyses of hydrochemical, aquatic macrophyte, zooplankton (Cladocera), and fish material colected April and May, 1978, in the reservoir show the following ecological situation. The Curuá-Una River and its tributaries belong, from a chemical point of view, to the complex "clear water" group, however the Curuá-Una\'s tributaries above the dam site, are very acid and extremly poor in mineral salts, while the Curuá-Una River itself presents a higher pH and a greater concentration of salts. The dilution effect of the tributaries in the Curuâ-Una River probably surmounts the local enriching effects of soil and vegetation drainage. No pronounced temperature or chemical stratification wore observed probably because of the low retention time of the water in the reservoir, 29,1 days, which resulted in a theoretical current velocity of aproximatly 100 m/hour. The reduction in oxygen between afluent and efluent is distinct but H2S was not observed during this sampling period. Great quantities of floating aquatic macrophytes occur in the reservoir and the principal species are Eichhornia crassipes, Scirpus cubensis, Pistia stratiotes and Paspalum repens. The abundance and distribution of the plants show clear relationships with the chemical situation of the reservoir as well as with the history of the inundation period. 34 species of Cladocera belonging to 6 families were identified, however, the density of animals was very low. The distribution and standing-stock of Cladocera show differences between the collecting sites as well as a vertical stratification, 3 species, Bosminopsis deitersi, Ceriodaphnia cornuta and Ceriodaphnia reticulata, represented 53% - 99% of the total number of specimens. 62 species of fish, belonging to 14 families were collected. Some species showed preference for the reservoir area while others were found predominantly above or below. The frequency of the "piranhas" was two times greater in the reservoir while members of the Auchenipteridae were more frequent outside the reservoir. Clupeidae were found only below the dam site. The total quantitly of fish was relatively low as many specimens were small.No presente trabalho, são apresentados os resultados limnológicos elaborados durante o período de abril e maio de 1978, em Curuá-Una, a primeira represa hidrelétrica da bacia Amazônica. Foram estudadas as condições hidroquímicas, as macrófitas aquáticas, o zooplâncton (Cladocera), e a ictiofauna. A água dos afluentes da represa, de um modo geral, é extremamente pobre em sais minerais. Mesmo assim, observaram-se nítidas diferenças químicas entre os afluentes principais, A redução no teor de oxigênio, dentro da represa, foi bem pronunciada. Grandes quantidades de macrófitas aquáticas flutuantes ocorreram na represa, sendo que as principais espécies foramEichhorrhia crassipes, Scirpus cubensis, Pistia stratiotes e Paspalum repens. A abundância das plantas e sua ocorrência mostram nítidas relações com as condições hidroquímicas. As 34 espécies de Cladocera, representantes de 6 famílias, foram identificadas. O número de indivíduos, no entanto, foi relativamente baixo. Três espécies, Bosminopsis deitersi, Ceriodaphnia cornuta e Ceriodaphnia reticulata representaram entre 53 - 99% dos espécimens coletados. Sessenta e duas espécies de peixes, pertencendo a 14 famílias, foram coletadas. Observou-se uma preferência de algumas espécies pela área do reservatório, enquanto outras foram encontradas principalmente acima ou abaixo da represa. A freqüência de piranhas foi duas vezes maior na represa, do que nos locais acima ou abaixo da mesma

Sinecologia da ictiofauna da Represa de Curuá-Una, Amazônia: características hidroquímicas, climáticas, vegetação e peixes

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Nutrientes e interações aquático-forestais em um lago da planície amazônica: Uma abordagem ecológica

Aim: Catalão Lake was surveyed between 2002 and 2011 with The aim of studying seasonality of The flow of nutrients between water, sediment and aquatic macrophytes. The role of The flood pulse and The ecological mechanisms influencing The forest-water interactions in The Amazon floodplain were discussed; Methods: Catalão Lake is located in The Amazon floodplain (03° 08'-03o 14' S and 59° 53'-59° 58' W), near The confluence of The Solimões and Negro rivers, approximately 3000 m from The port of CEASA, near The city of Manaus. It is considered to be a mixed water lake because it receives white waters rich in sediments from The Solimões River and black waters with humic substances from The Negro River. Physical and chemical parameters including C, N and P levels were studied in The diverse compartments, and a flux model was developed; Results: There is a strong nutritional (C, N and P) and ionic (Na+, K+, Ca2+, Mg2+, Cl-, HCO3-, CO32- and SO42-) flow from The rivers to The lake. The highest C:N:P ratio was found in Paspalum repens which, during periods of drought, played an important role in releaseing nutrients into The water. The connectivity of The lake with The rivers ensured a high variation of transparency and nutrient content, fundamental for biological processes. A model of The nutrient flow, interaction and connectivity between ecosystems, and The influence of The hydrological cycle has been developed