Abstract
River damming causes a decrease in water current velocity which leads to an increase in richness and abundance of organisms atypical for running waters. Zooplankton is a representative example of such organisms. The influx of zooplankton from carp ponds is an additional factor that increases richness and abundance of zooplankton in rivers. We hypothesized that zooplankton dispersing from the carp ponds colonize the impoundments in river and the richness of zooplankton increase in impoundments by development of new species, not observed in the upstream. The zooplankton was collected monthly from April to September of 2013 and 2014. Sampling sites were located in the Barycz river (in the lotic sections and in the dam impoundments), as well as in its tributaries, which are the outlets of carp ponds. The most changes in zooplankton richness and abundance were observed at sites located within the dam impoundments, especially in relation to the lower values of the current velocity. Since the abundance of pelagic rotifers, cladocerans and copepods in the carp pond outlets was similar to that at lower sites in the Barycz, the influence of the carp pond outlets on the abundance in the dam and lotic sections was significant. The river itself in its impounded sections provides advantageous conditions for retention and colonization by a high abundance of zooplankton dispersing from the carp ponds, and for the development of species not occurred in the upstream, which, in turn, increases richness.
Highlights
Catchment management is one of the factors that determines the functioning of a region and comprises numerous technical measures that depend on a region’s needs, river-bed maintenance, agricultural drainage, water impoundments for fish farming or securing energy needs, flood control systems, and water retention (Jones et al, 2004; Soranno et al, 2015; Ullah, Jiang & Wang, 2018)
Lower current velocity values were observed at the dam sites than at the lotic section
Spatial changes in the zooplankton composition in the Barycz river reflected the effects of physical changes induced by the dam impoundments and by dispersion of zooplankton from the carp ponds outlets
Summary
Catchment management is one of the factors that determines the functioning of a region and comprises numerous technical measures that depend on a region’s needs, river-bed maintenance, agricultural drainage, water impoundments for fish farming or securing energy needs, flood control systems, and water retention (Jones et al, 2004; Soranno et al, 2015; Ullah, Jiang & Wang, 2018). Human-made dams are one of the most important technical measures that break the river continuum Oftentimes, they cause irreversible alterations in rivers, and distort their natural flow (Allan & Castillo, 2007). Such alterations are reflected in physicochemical and biological variables, as well as the loss and replacement of typical lotic species by typical stagnant water species. Small dams create distinct physical and ecological conditions that are relatively different from the ones found in free-flowing lotic sections. This is manifested by a reduction of current velocity, increase of water retention time and increase of nutrient content
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