Copepod assemblage structure (Crustacea: Copepoda) along a longitudinal environmental gradient in a tropical river-floodplain system, Brazil

Abstract

Cite as: Palhiarini, W.S. et al. Copepod assemblage structure (Crustacea: Copepoda) along a longitudinal environmental gradient in a tropical river-floodplain system, Brazil. Acta Limnologica Brasiliensia, 2017, vol. 29, e102. Abstract: Aim: In this study, we analyzed the structure of the copepod community along a longitudinal axis of the last undammed stretch of the Upper Paraná River floodplain, downstream of Porto Primavera reservoir. We hypothesized that (i) copepod assemblage would show an increase in the abundance of organisms, species richness and specific diversity with the distance from the Porto Primavera reservoir, due to the arrival of species from adjacent lakes and tributaries; (ii) copepod abundance and species richness would be higher in tributaries and adjacent lakes located at the floodplain, which show higher environmental heterogeneity and function as a species source; and (iii) spatial patterns of copepod assemblage structure are related to the environmental gradient, since copepods show a rapid response to the variation of environmental conditions. Method: Sampling was performed quarterly from August 2013 to July 2014, at the subsurface of the pelagic region. Sampling sites were located along the Paraná River, in seven of its tributaries, and in eight lakes located in its floodplain. Results: We identified 29 species belonging to two families: Cyclopidae (21 species) and Diaptomidae (eight species). On contrary of our first hypothesis, ANOVA results showed a significant decrease in copepod abundance in the downstream direction. Similarly, the tributaries showed higher values of ecological attributes in the upstream stretch. RDA results showed that in axis 1, the Paraná River and the lakes were positively correlated with conductivity, pH, temperature and suspended organic matter, characterized by the most abundant copepod species. The tributaries, on the other hand, were negatively correlated with turbidity, total nitrogen, total phosphorus and depth. Axis 2 showed a positive correlation of the Paraná River with conductivity and suspended organic matter, and a higher abundance of Argyrodiaptomus azevedoi, Notodiaptomus iheringi, N. henseni, N. cearensis 2 Palhiarini, W.S. et al.

Do changes in the water regime determine the abundance of the copepod trophic group in a Neotropical floodplain?

“…On the other hand, in extreme floods, environmental conditions are disadvantageous for the development of large populations of algae due to greater hydrodynamic instability, which can lead to a decrease in the organisms that feed on them (Baranyi et al, 2002). Furthermore, as expected in our study, the greatest abundance values for N. henseni (herbivores), T. minutus (omnivores), and T. decipiens (omnivores), have often been found in freshwater ecosystems (Ferrareze & Nogueira, 2011), mainly in the floodplain of the upper Paraná River (Lansac-Tôha et al, 2004;Palhiarini et al, 2017). The chlorophyll-a and total phosphorus, considered as parameters of productivity, had a strong positive relationship with the abundance of herbivorous copepods during 2000.…”

Damming interacts with the flood pulse to alter zooplankton communities in an Amazonian river

“…Monitoring programmes of floodplain tropical rivers should include sampling sites upstream of dams, but also several sampling sites further downstream from dams, as more widespread effects on biological communities have been detected in some studies to date (Bonecker et al., ; Braghin et al., ; Palhiarini, Schwind, Arrieira, Velho, & Lansac‐Tôha, ). In our study, the limited number of sites may have reduced our ability to detect the impacts of damming.…”