Seasonal and spatial variations in limnological conditions of a floodplain lake (lake Catalão) connected to both the Solimões and Negro Rivers, Central Amazonia

Abstract

Lakes play an important role in biogeochemical, ecological and hydrological processes in the river-floodplain system. The aim of this study was to evaluate the dynamics of the limnological conditions of Catalão Lake, an Amazon floodplain lake. Thus, some of the main limnological environment variables (O 2 , temperature, pH, nutrient, electrical conductivity) of the Catalão Lake were analyzed under temporal and spacial scales. The study was conducted between November/2004 and August/2005. Sampling excursion were carried out every three months; one excursion for each of the four different hydrological periods (low water, rising water, high water and falling water). Sampling points were chosen so that it could be obtained a gradient of the distance from Negro River. Limnological profiles in Catalão Lake showed generally acidic to slightly alcaline water, with low levels of dissolved oxygen and low concentrations of soluble reactive phosphorous. The Negro River seems to exert the main influence during the rising water period, while the Solimões River is the principal controlling river during peak water. The Principal Component Analysis (PCA) grouped the seasonal collections by hydrological period, showing the formation of a north-south spatial gradient within the lake in relation to the limnological variables. Multivariate dispersion analysis based on distance-to-centroid method demonstrated an increase in similarity over the course of the hydrological cycle, as the lake was inundated in response to the flood pulse of the main river channels. However, the largest spatial homogeneity in the lake was observed in the epilimnion layer, during the falling water period. The daily analysis of variation indicated an oligomitic pattern during the years in which the lake was permanently connected to the Negro River. Although Catalão Lake receives large quantities of both black water from the Negro River and sediment-filled water from the Solimões River, the physical and chemical characteristics of the lake are more similar to those of the Solimões (várzea lake) than the Negro (blackwater lake). KEYWORDS: Hydrological regime, water quality, chemical limnology. Variações espaciais e temporais nas condições limnológicas de um lago de planície de inundação (lago Catalão) conectado aos rios Solimões e Negro, Amazônia Central RESUMOOs lagos exercem um papel importante nos processos biogeoquímicos, ecológicos e hidrológicos no sistema rio-planície de inundação. O objetivo do presente estudo foi avaliar a dinâmica das condições limnológicas do lago Catalão, um lago da planície de inundação amazônica. Algumas das principais variáveis limnológicas (por exemplo, O 2 , temperatura, pH, condutividade elétrica, nutrientes) do lago Catalão foram analisadas em uma escala temporal e espacial. O presente estudo foi realizado no período de novembro de 2004 a agosto de 2005. As amostragens foram trimestrais, com um total de quatro coletas, uma em cada fase do ciclo hidrológico (Seca, Enchente, Cheia e Vazante). Os pontos de amostragem fo...

Influência das condições do habitat sobre a estrutura de herbáceas aquáticas na região do Lago Catalão, Manaus, AM

“…No entanto, a pequena área de cobertura na AM por esta espécie pode ser um resposta a influência da conectividade hidrológica na região do Lago Catalão influenciada pelos rios Solimões e Negro que ao misturarem suas águas diluem a concentração de nutrientes na AM em relação a AB. Embora o Lago Catalão receba águas oriundas dos rios Solimões e Negro, a análise das características físicas e químicas da água indica que ele pode ser considerado um lago predominantemente de várzea da Amazônia Central (Brito et al 2014). Isso justifica a alta frequência de E. crassipes que é uma espécie abundante nas férteis várzeas, mas que possivelmente chega às águas mistas e pretas adjacentes favorecida pelos ventos e correntes, mesmo que esses não sejam os ambientes ideais para seu crescimento (Lopes et al 2011).…”

Seasonal Variation in the Distribution and Isotopic Composition of Phytoplankton in an Amazon Floodplain Lake, Brazil

“…Among the few existing studies, it is worth mentioning the research conducted by Schmidt (1973) due to its duration and scope and, among other things, the inverse relation found between the water level of the lake and the concentration of chlorophyll, a pattern frequently observed in floodplain lakes (Carvalho et al, 2001). Research on chlorophyll concentrations in the Amazon has generally demonstrated that the largest concentrations of phytoplankton usually occur in the dry season and the lowest concentrations in the flood season, as shown in the following studies: Fisher (1978) on Lake Janauacá and Rio Solimões (Amazon River), Lopes and Bicudo (2003) on lakes in the Acre river basin; Camargo and Myai (1988) on Trombetas River; Schmidt (1982) on Tapajós River; Ibañez (1998) on Lake Camaleão, and Brito et al (2014) on Lake Catalão. The concentration of chlorophyll in a lake varies according to the physiological state of the cells, the species composition, the depth, and the environment studied (Santos et al, 1999).…”

“…The hydrologic balance of Lake Catalão is greatly influenced by the relative magnitudes of the inflows of rivers Solimões and Negro, and can be described as a variable mixture of Santos et al, 2008). these chemically different sources (Brito et al, 2014;Almeida and Melo, 2011). This variable mixture results in a very particular temporal and spatial distribution of physical and chemical characteristics of the lake.…”

“…In a study based on samples collected during the dry and flood periods, an inventory of 235 taxa of phytoplanktonic algae was registered by Almeida and Melo (2011): these algae belonged to 10 classes, with the greatest diversity of species found for class Chlorophyceae, and the greatest abundance Cyanophyceae, particularly the species Synechocystis aquatilis, Synechococcus elongatus and Planktothrix isothrix. The seasonal dynamics of the phytoplanktonic biomass of Catalão Lake were characterized by Brito et al (2014) as follows: a period of low density (rising and high water period), with the average values of chlorophyll in the photic zone varying between 3.4 µg/l to 13.5 µg/l, followed by the falling and low water phases when increase in the photic zone was observed, with average chlorophyll concentrations of 12.2 µg/l to 24.7 µg/l. On the other hand, studies of reproductive ecology of fish suggest that the areas of confluence between rivers of clear or dark waters are used for the reproduction of migrating Characiform species (Leite et al, 2002).…”

“…In the pelagic region a three inch wide PVC pipe with water-tight closing mechanism was used, which allows water passage when the pipe is lowered down and is closed when the tube is pulled up. The depth to which the pipe was taken down was determined in situ as three times Secchi depth value, thus ensuring sampling within the entire euphotic zone according to extinction coefficient values estimated by Brito et al (2014). In the littoral region, water was sampled using plastic buckets and care was taken to avoid collection of sediments.…”