Abstract
Ecological metrics and assemblages of three orders of aquatic insects (Odonata, Coleoptera and Trichoptera—OCT) in an industrial canal system affected by dredging were studied. Five sites (a river as a control site and canals) along the Vistula River in Central Poland were sampled during six sampling periods (2011 and 2013). Canonical correspondence analyses (CCA) was used to assess the influence of environmental variables on the distribution of 54 insect species in the following system of habitats—a river feeding the canals, river-fed inlet canals and outlet canals with cooling waters. Additionally, before and after control impact (BACI) was used to test for the impact of canal dredging in 2011 on the insect response metrics. Non-metric multidimensional scaling analysis differentiated insect assemblages of the three habitats and similarity percentage (SIMPER) indicated the species most responsible for the faunistic dissimilarities. Temperature was found to be a key factor governing the presence of insects in the outlet canals with cooling water. CCAs revealed that electrolytic conductivity (EC) and salinity had the greatest influence on the OCT fauna in the river and the inlet canals, whilst it was the dissolved oxygen and the level of development of aquatic plants that proved most important in the outlet canals. Modified ANOVAs showed that dredging significantly affected the mean species richness and the dominance in the canals. The changes in OCT species composition were highly informative. The comparison between tolerance patterns of the OCT orders against the five parameters (temperature, EC, total dissolved solids (TDS), pH and current) revealed that caddisflies are the most sensitive group, followed by Coleoptera while Odonata proved the most resistant. Dragonflies have the greatest potential to serve as bioindicators of industrially heated waters. The OCT fauna responded specifically to different environmental factors and stressors, it is strongly recommended to track the responses on different levels, not only metrics, but above all, species.
Highlights
Y (EPT – Ephemeroptera, Plecoptera and Trichoptera) they are frequently analyzed in the context of water quality assessment (e.g. Pollard & Yuan, 2010)
Each order of organisms contributes significantly to the general response. These results have demonstrated that caddisflies are unsuitable for detecting changes in constant temperatures above 20°C, which corresponds to the discovery of Stewart et al (2013), that the thermal tolerance of the fauna suggests 21°C as the upper thermal tolerance (UTT) for a range of sensitive freshwater insect taxa
Our research highlighted that running waters of anthropogenic origin used in industry, influenced by strong and regular transformations make up an interesting model study system
Summary
Y (EPT – Ephemeroptera, Plecoptera and Trichoptera) they are frequently analyzed in the context of water quality assessment (e.g. Pollard & Yuan, 2010). The most acceptable alternative appears to be a mixed approach, i.e. one that indicates general trends but at the same time supplies more concrete data at the level of assemblages or species This is especially apparent in the case of aquatic insects, where knowledge of the tolerance range of particular species to a given set of habitat parameters, including pollution, is difficult to acquire and far from complete: the gaps relate especially to taxa that are less common, difficult to trap or to identify (Rosenberg & Resh, 1993; Carlisle et al, 2007; Graf et al, 2008; Suriano et al., 2011). These canals were dredged during this project and this additional aspect made them highly suitable for investigating the influences of diverse environmental factors and stressors on aquatic insects in combination with environmental gradients, the high values of which are human-induced, and with the gradients associated with the structural (hydrodynamic) features of these watercourses
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