Diurnal Changes of Zooplankton Community Reduction Rate at Lake Outlets and Related Environmental Factors

Abstract

The reduced zooplankton abundance at the outlet sections of lakes depends on the occurrence of preying fry. Therefore, light conditions can play a major role in the drift of zooplankton along river outlets. The aim of this study was to determine the influence of diurnal light conditions on the decline of zooplankton densities at lake outlets. Photosynthetically active radiation (PAR) levels were measured to determine their effect on the rate of reduced zooplankton abundance. Cladocerans and copepods showed a significantly greater reduction in abundance than rotifers and nauplii. A significant positive relationship was observed between the PAR levels and the reduced abundance of Asplanchna sp., small cladocerans, large cladocerans and Copepoda at the lake outlets. Among the rotifers, small pelagic rotifers drifted the farthest at all hours of the day. Large crustaceans, especially the large cladocerans and copepodites and adult copepods, had the lowest chance of dispersing over a wide area. Our results indicate that light conditions play an important role in the reduction of zooplankton abundance at lake outlets and have an indirect influence on the downstream food web.

Trophic interactions across lake–stream boundaries in mountain lakes

“…Numerous studies have shown that fish alter the flow of energy from aquatic to terrestrial food webs through the suppression of emergent aquatic invertebrates (e.g., Knight et al 2005, Finlay and Vredenburg 2007, Epanchin et al 2010). The present study shows that effects of fish on macroinvertebrate communities in streams below lakes In addition to the effects of fish on zooplankton export, the present study is consistent with a recent study suggesting that zooplankton export from lakes varies greatly over a 24 h period (Czerniawski et al 2016). Crustacean zooplankton in lakes typically migrate daily over a range of several meters or more (Pennak 1944, Dodson 1990), which would explain a diel cycle in export.…”

“…For comparisons with zooplankton mass flux based on midday synoptic sampling, macroinvertebrate biomass was estimated for each taxon in each stream reach (interval between sampling points) as the mean for the upstream and downstream sampling site for each study reach. An ANCOVA followed by model simplification (Crawley 2007) was used with these values to evaluate the interaction and independent effects of fish and zooplankton mass flux on total macroinvertebrate biomass and biomass of functional feeding groups of macroinvertebrates.…”

A comparison of the effect of beaver and human‐made impoundments on stream zooplankton

“…Therefore, the pace of changes in zooplankton structure in the Upstream and the Dam sites differs due to specific Therefore, greater alterations in the Dam sites resulted in more zooplankton drifting to the Downstream. However, it is well known that a decline in richness and density at the Downstream sites is typically due to fish predation; grazing by suspension-feeding, filter-feeding, or net-spinning macrozoobenthos; and sediments in outlet sections of slow-moving waters (e.g., Chang et al, 2008;Czerniawski, Sługocki, & Kowalska-Góralska, 2016;Lair, 2006;Taylor, 1980).…”

Changes in particulate organic matters and plankton populations in nature-like fishways: role of nature-like fish ways in water treatment

“…In shallow conditions, increased contact with stream sediments could decrease zooplankton abundance . Moreover, suspension-feeding, filter-feeding, or net-spinning macrozoobenthic organisms could also reduce zooplankton abundance (Czerniawski et al, 2016). Even within a short section of a productive river that includes zooplankton, phytoplankton, and drift food sources, macroinvertebrates and fishes could play an important role in consuming and removing the drifting particles Doi et al, 2008).…”

“…5). Generally, because of the size selection of zooplankton by fish, larger zooplankton, such as the Daphnia and Copepoda are the first to be reduced and the rotifers are the last Czerniawski et al, 2016). However, when small zooplankton species occur in high densities, then the reduction rate increases due to a higher encounter rate with predators, including benthic invertebrates (Jack and Thorp, 2002).…”