Composition, abundance and biomass of zooplankton in Orinoco floodplain lakes, Venezuela

Abstract

Zooplankton samples were collected over a 21-month period in five fioodplain lakes of the Orinoco River in order to establish zooplankton species composition, abundance patterns, and biomass and their relationships with the patterns of inundations and lake morphometry. 60 rotifer taxa were identified. This group was generally more abundant than copepods and cladocerans (mean : 73,4 % of total zooplankton). spinulosum. Most frequent and abundant zooplankton species were euplanktonic with a dominance of filter feeders and microphagous detritivores. Mean zooplankton density in all lakes ranged from 340 ind./l to 3 486 ind./l. Biomass ranged from 71,1 ^g.l (dw) to 432,8 ^g/l. Rotifers accounted for 64,7 % of the total mean zooplankton biomass in three lakes while copepods accounted for 57,8 % of the biomass in two lakes. Both density and biomass were markedly seasonal with highest mean values at low waters. Mean density in the lakes was 100 times higher than in the Orinoco main stem. Lakes with highest variabilities in surface area and water depths showed highest zooplankton densities. The type of connection (direct or indirect) established between the lakes and the major source of the water also seemed important to interpret the productivity of fioodplain lakes.

Zooplankton variation in Fraijanes Lake (Costa Rica) during the course of one year

“…The outflow represents a source of mortality and wash out of plankton populations. This pattern of variation has been observed in other cases where the hydrological conditions change completely between dry and rainy season (Twombly, 1983;Hart, 1990;Arcifa et al, 1992;Vásquez & Rey 1992;Dejen et al, 2004, Merayo & González, 2010. But also changes in stratification, such as occur in Lake Fraijanes between wet and dry season (Umaña, 2014) are an important factor (Saunders & Lewis, 1988;Mengestou & Fernando, 1991;Panarelli et al, 2000) as this condition is highly associated with changes in weather conditions, as was also the case in Clavellinos reservoir (Merayo & González, 2010).…”

“…Studies on seasonal changes of lacustrine zooplankton composition in tropical regions had yielded different results and vary depending on the system (Hart, 1985). In some cases, it has been observed an effect of hydroclimatic variability and associated changes in turbidity, with lower densities during the rainy season, this is due to the effect of dilution and turbidity (López-López & Serna-Hernández, 1999;Twombly, 1983;Hart, 1990;Arcifa, Gomez, & Meschiatti, 1992;Vásquez & Rey, 1992;Dejen, Vijverberg, Nagelkerke, & Sibbing, 2004;Nogueira, Reis-Oliveira, & Tenorio de Britto, 2008), but also from changes in stratification (Saunders & Lewis, 1988;Mengestou & Fernando, 1991;Panarelli, Nogueira, & Henry, 2000); or changes in temperature, which also seem to correlate with changes in predation from Chaoborus and fishes in some cases (Cardoso & Marques, 2009;Jiménez-Contreras, Sarma, Merino-Ibarra, & Nandini, 2009;Arcifa et al, 2015). In the present study, the temporal variation of zooplankton in a small neotropical lake, is examined in order to know if changes in zooplankton composition could be explained by the variation in the physical condition of the lake or by changes in phytoplankton composition.…”

Diversity of floodplain copepods (Crustacea) modified by flooding: species richness, diapause strategies and population genetics

“…Flooding facilitates substantial transport of passively dispersing zooplankton. Such "washout" effects have been reported from floodplains around the world (Saunders & Lewis 1988, Vásques & Ray 1992, Michels et al 2001. Here, we examine heterozygosity and genetic distances between populations of the calanoid copepod Skistodiaptomus pallidus (Herrick) 1879 in relation to pond location on a longitudinal gradient.…”

Zooplankton biomass of reservoirs in different trophic conditions in the State of São Paulo, Brazil

“…In Brazil, studies on the zooplankton biomass of eutrophic and oligotrophic reservoirs have been undertaken by MatsumuraTundisi & Tundisi (1986), Matsumura-Tundisi et al (1989), Esteves & Sendacz (1988), Melão (1997), Melão & Rocha (2000) and Wisniewski (1998). Saunders & Lewis (1988) and Vásquez & Rey (1992) determined the zooplankton biomass of lakes in Venezuela.…”