Intra and inter-annual structure of zooplankton communities in floodplain lakes: a long-term ecological research study

Abstract

Abstract:Water flow management has significantly changed the natural dynamic of floods, which are responsible for the structure and dynamic of aquatic communities in river-floodplain systems. With the aim to elaborate a conceptual framework that describes the main ecological factors associated with zooplankton community structure in the Upper Paraná River, we investigated the mechanisms that regulate the communities structure and their response to inter-annual and hydro-sedimentological variations in the floodplain and the biological factors associated with species abundance in those communities. For this we conducted samplings every six months (potamophase in March and limnophase in September) to characterize intra and inter-annual variations in community structure between 2000 and 2008. The intra-annual differences on the species richness, abundance, Shannon diversity index, and evenness, were conducted using Bayesian procedures to show probabilistic predictions of the data fit to main variation sources. Non-metric multi-dimensional scaling (NMDS), multi-response permutation procedure (MRPP), and indicator species analysis (IndVal) were run to assess and characterize the seasonality of the community structure. During high water (potamophase), hydrologic connectivity favoured exchange and dispersal of species in some lakes, increasing local diversity; during low water (limnophase), higher local productivity favoured opportunistic taxa, increasing species dominance and decreasing local diversity. Food resources and density of small-size fish were biological factors associated with the seasonal dynamic of the zooplankton community; these factors were dependent on hydrosedimentological phase (potamophase or limnophase). Water levels and limnological modifications related to water flow management have promoted replacement and impoverishment of aquatic biota in affected lakes and have indicated the ecological importance of a natural dynamic flood, which displays regular flood pulses. The conceptual model presented encompassed interactions between diverse environmental variables to more understandable mechanisms of the main sources of community variation. Rev. Biol. Trop. 60 (4): 1819-1836. Epub 2012 December 01.

Local factors affecting the testate amoeba community (Protozoa: Arcellinida; Euglyphida) in a neotropical floodplain

“…This promoted the coexistence of those able to adapt to the environmental conditions. Moreover, both the flood pulse and the dry period exerted a direct influence on the filters and established the spatial distribution of the species (Simões et al, 2012. During the low water period, the species were associated with all tested environmental variables, revealing no influence on the testate amoebae.…”

Effect of daily variation on the seasonality of testate amoebae community structure in different environments of a Neotropical floodplain

“…The lack of significance in the association between the sampling time lag and the Kendall correlation matrix suggests that an increase in depth, caused by the high-water period, is responsible for maintaining environmental conditions. These conditions favour the lower variability of the community in the highwater period (Simões et al 2012).…”

“…curs through the displacement of water masses or the ability of organisms to move between planktonic and littoral zones (Lansac-Tôha et al, 2004). This process might also be aided by water contraction in lentic ecosystems (Simões et al, 2012), reflecting the greater proximity of the littoral vegetation and planktonic zones, as well as reduction of the water column. Thus, the contribution of species associated with vegetation and sediment was greater, increasing the richness and abundance in this studied period.…”

Adjacent environments contribute to the increase of zooplankton species in a neotropical river

“…These characteristics enable the high diversity of species found in these fluvial systems (Naiman et al, 2000;Simões et al, 2012).…”

“…This idea complements the nestedness concept, because the heterogeneity and structure of the habitat influence the distribution and establishment of species and assemblage formation. Thereby, environments that are more complex support higher species richness than simpler environments (Hutchinson, 1959;Simões et al, 2012).…”