Phytoplankton community structure in an Amazon floodplain lake (Lago Catalão, Amazonas, Brazil)

Abstract

RESUMOEste estudo analisou os atributos da comunidade fitoplanctônica (riqueza de espécies, diversidade, equitabilidade, densidade, estrutura de tamanho e taxa de modificação da comunidade) associados com algumas características físicas e químicas de um lago de água mista (branca e preta) durante quatro semanas consecutivas na cheia e na seca, em quatro estações amostrais e três profundidades (superfície, meio e fundo). O lago apresentou diferentes características limnológicas entre os períodos de seca e cheia. O fitoplâncton foi composto principalmente por algas nanoplanctônicas, especialmente Chlorophyceae e Cyanobacteria. Em ambos os períodos, o grupo funcional X1 foi a associação predominante no que se refere à densidade de organismos. Com relação aos períodos de amostragem, os maiores valores de riqueza, equitabilidade e diversidade foram registrados no período de seca, sendo Chlorophyceae, Euglenophyceae, Bacillariophyceae e Cyanobacteria os grupos com maior número de espécies, enquanto, no período de cheia, Chlorophyceae e Cyanobacteria foram os grupos com maior riqueza de espécies. As variáveis físicas e químicas determinantes na distribuição das espécies foram oxigênio dissolvido, temperatura, condutividade elétrica e razão zona de mistura:zona eufótica.Palavras-chave: fitoplâncton, planície de inundação, lago amazônico. ABSTRACTThis study analyzed the attributes of the phytoplankton community (species richness, diversity, equitability, density, size structure and rate of community compositional change) associated with some physical and chemical characteristics of a mixed water lake (white and black water) for four consecutive weeks in the dry and rain season, in four sampling sites and at three depths (surface, middle and bottom). The presented differences in limnological characteristicas in the rainy and the dry season. The phytoplankton was composed, mainly by nanoplanktonic algae, especially Chlorophyceae and Cyanobacteria. In both periods the functional group X1 was the predominant association in terms of organism density. Considering the sampling seasons, the highest values of richness, equitability and diversity were recorded in the dry season. Chlorophyceae, Euglenophyceae, Bacillariophyceae and Cyanobacteria were the groups with the highest number of species in the dry season, while Chlorophyceae and Cyanobacteria were the groups with the highest species richness in the rainy season. The main physical and chemical variables that determine the distribution of the species were dissolved oxygen, temperature, electrical conductivity and ratio of mixing zone to euphotic depth.Key words: phytoplankton, floodplain, Amazon Lake. Estrutura da comunidade fitoplanctônica de um lago de inundação amazônico (Lago Catalão, Amazonas, Brasil) Phytoplankton community structure in an Amazon floodplain lake (Lago Catalão, Amazonas, Brazil) 113 Neotropical Biology and Conservation Estrutura da comunidade fi toplanctônica de um lago de inundação amazônico (Lago Catalão, Amazonas, Brasil)

A functional deconstructive approach to mixotrophic phytoplankton responds better to local, regional and biogeographic predictors than species

“…The Amazonian lakes, for example, presented wide variation between the hydrological periods, promoting scenarios with high temporal and spatial environmental heterogeneity. The high concentration of nutrients recorded during the dry period in this floodplain favoured the RFGs W1 and W2 (euglenophyceans), confirming their preferences for high organic matter and contribution to primary productivity (Bovo‐Scomparin & Train ; Almeida & Melo ).…”

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

“…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 the dry period, there is no water flow into the lake from the adjacent rivers, and the lake area is reduced. 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.…”

“…The < 2µm fraction (autotrophic picophytoplankton) was not sampled in this study because the major phytoplanktonic species found in Lake Catalão were more than 2µm Cyanophyceae (Almeida and Melo, 2011). Twenty liters of water were filtered through a 60 µm mesh to remove the large zooplankton represented by Copepoda and Cladocera.…”

Phytoplankton of two rivers in the eastern Amazon: characterization of biodiversity and new occurrences

“…This has been the case for the Amazon region, where few studies have addressed the phytoplankton community as a whole ( Huszar & Reynolds 1997;Ibañez 1998;Melo & Huszar 2000;Melo et al 2005a;Paiva et al 2006;Aprile & Mera 2007;Monteiro et al 2009;Pereira et al 2010;Almeida & Melo 2011). Most studies conducted in the region have examined specific taxonomic groups, such as desmids (Grönblad 1945;Förster 1963Förster , 1964Förster , 1969Förster , 1974Scott et al 1965;Thomasson 1971;Sophia & Huszar 1996;Lopes & Bicudo 2003;Melo et al 2005b;Souza et al 2007;Souza & Melo 2011) and diatoms (Diaz-Castro et al 2003;Ferrari et al 2007;Pereira et al 2012;Raupp et al 2009;Sala et al 2002;Tudesque et al 2012;Wetzel et al 2012).…”