Łukasz Sługocki

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

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.

Analysis of zooplankton assemblages from man-made ditches in relation to current velocity

Abstract Because of the slow current velocity, man-made ditches may create distinct physical and ecological conditions that are suitable for the growth of zooplankton populations. However, the influence of drainage ditches on zooplankton communities has not been studied yet. This study aims to answer the following questions: i) Are man-made ditches a rich source of zooplankton? ii) What current velocity value leads to abundant zooplankton in man-made ditches? iii) Do zooplankton communities differ between man-made ditches and connected natural streams? In man-made drainage ditches with a water current lower than 0.1 m s-1, the abundance of zooplankton was greater than in the majority of streams. Sometimes this level of abundance was equivalent to the densities of zooplankton in lakes or dammed reservoirs. The presence of zooplankton in man-made ditches may be of great importance to the establishment of food webs, particularly during periods of high water levels or heavy rainfall, both of which may accelerate the water current, causing the dispersion of zooplankton along the ditches and into natural streams.

A comparison of the effect of beaver and human-made impoundments on stream zooplankton: Impoundment effect on stream zooplankton

Ecohydrology. 2018;11:e1963. https://doi.org/10.1002/eco.1963 Abstract Small human‐made dams and beaver ponds cause significant changes in the environment of small streams. The decreased current velocity and increased water retention time in these impoundments favour the development of limnetic organisms, for example, zooplankton. However, small human‐made reservoirs are regulated, deep and narrow, whereas beavers create relatively large impoundments with numerous shallow patches and their impact on the stream zooplankton communities can be different. We compared the effect of beaver ponds and small reservoirs on the zooplankton communities in streams. Three sample collection sites were established in each stream. Site 1 was approximately 100 m upstream of the water impoundment formed by the dam. Site 2 was at the dam impoundment of the stream water. Site 3 was approximately 300 m below the dam. Beaver ponds have a larger impact on the zooplankton richness and the abundance changes compared with seminatural reservoirs not maintained by people, and a much greater impact than reservoirs regularly cleaned and regulated. Beaver ponds create heterogeneous environment that favour the occurrence of a greater number of zooplankton species compared with small reservoirs. Moreover, the increase in organic matter in the downstream areas could lead to trophic changes in the stream.

Effects of beaver dams on the zooplankton assemblages in four temperate lowland streams (NW Poland)

Abstract Beaver ponds favour lentic species over the original lotic animals. The typical lentic animals are zooplankton, which can be good predictors of hydrological changes in streams caused by beaver activity. We analysed the effects of beaver dams on the zooplankton communities in small lowland streams in stream-beaver pond-stream systems. All spatial changes in the composition of zooplankton reflected the effects of physical changes introduced by the beaver dams. The rapid increase in the density of the aforementioned taxa was possible because the features typical of stagnant water reservoirs are present in beaver ponds. The number of taxa and the abundance and biodiversity of zooplankton, especially planktonic rotifers, were higher in the dam and downstream sites than in the upstream sites. Therefore, the impact of beaver ponds on the composition of zooplankton in streams below the dams is considerable, and there is an increase in the organic matter downstream, which leads to trophic changes in the stream.