Environmental and spatial processes influencing phytoplankton biomass along a reservoirs-river-floodplain lakes gradient: a metacommunity approach

Abstract

Evaluation of the relative influences of environmental and spatial processes instructuring aquatic metacommunities is an essential first step for understandinghow these factors govern species distributions and affect spatial and temporalvariability in community structure. Such variability has many causes and conse-quences at different scales. In the case of phytoplankton metacommunities, bothspecies sorting and mass effect processes are likely to be important in structur-ing the patterns of biomass distribution on large spatial scales.2.We investigated the influences of environmental and spatial components on thephytoplankton community on a large spatial scale, consisting of a reservoirs-river-floodplain lakes gradient in a Neotropical region. Using partial redundancyanalysis, we partitioned the relative role of environmental (environmental filters)and spatial (asymmetric eigenvector maps) processes structuring phytoplanktonbiomass.3.A clear difference of the limnological conditions was observed between thereservoirs and river–floodplain lakes system. High species richness and highermean values of phytoplankton biomass were recorded in the floodplain lakes.Variation partitioning demonstrated the importance of both environmental andspatial process in phytoplankton biomass structuring. However, the relativeimportance of these processes may vary over time.4.Our results suggest that from a metacommunity perspective, the phytoplanktonbiomass of upstream reservoirs and a downstream river–floodplain lakes systemis determined by environmental conditions (species sorting process), mainly inthe floodplain lakes; and by high dispersion rates favoured by the connectivityand unidirectional flow (mass effect process), mainly between the reservoirs and the river.