Flood pulses drive the temporal dynamics of assemblages of aquatic insects (Heteroptera and Coleoptera) in a temperate floodplain

Abstract

Summary Lowland riverine floodplains are among the most dynamic and heterogeneous of ecosystems, but many have been extensively modified. Their provision of important habitats provides a key motivation for restoring natural flow regimes (in terms of magnitude, frequency, duration, timing and rate of change of hydrological conditions). Despite general recognition that aquatic insects respond to changes in water availability, there is little agreement about the influence of flow regime components on community structure in floodplains. We analysed a 6‐year (2005 and 2007–2011) data set of aquatic insects (Heteroptera and Coleoptera) in a large Danubian floodplain characterised by pronounced hydrological variability. We hypothesised that abundance and assemblage structure would depend on flow regime components. In particular, we predicted that high‐flow events in the mainstream and concurrent high‐magnitude floods of prolonged duration would have a positive effect on diversity and abundance and that insect assemblages would differ between phases of hydrological connectivity. In addition, we assessed whether the survival of two threatened aquatic insects, Graphoderus bilineatus and Berosus geminus, depends on hydrological connectivity. Abundance and species richness of Heteroptera and Coleoptera increased during years with frequent extremely high flood pulses and prolonged flooding. Multivariate ordination showed subtle relationships between hydrological conditions, hydrological connectivity and insect assemblages with number of days in flood providing the best fit. Spring floods had a more pronounced effect on the assemblages than autumn floods. The time lag between flood occurrence and its apparent effect on aquatic insects was 17–31 days, reflecting insect life cycles. The abundance of G. bilineatus (Coleoptera: Dytiscidae) was affected by mean water level during the month preceding sampling, whereas the abundance of B. geminus (Coleoptera: Hydrophilidae) was related to the occurrence of prolonged high‐magnitude floods. The current water regime of the Danube River favours generalist species with high dispersal capacities and broad niches and food resources. Changes in flow management practices could remove the positive influence of floods on aquatic insect communities and lead to losses of threatened species that depend on these river–floodplain habitats. Our results contribute to the understanding necessary for appropriate evaluation and prioritisation of international floodplain conservation efforts.

Benthic and hyporheic macroinvertebrate distribution within the heads and tails of riffles during baseflow conditions

“…Research examining lotic environments has typically focussed on longitudinal and lateral gradients (environmental and ecological) as exemplified through the river continuum (Vannote et al, 1980;Rosi-Marshall et al, 2016) and flood pulse concepts (Junk et al, 1989;Turić et al, 2015). However, the majority of historic research has focussed on benthic habitats and communities, with little consideration of surface-groundwater interactions (Dole-Oliver & Marmonier, 1992;Boulton & Foster, 1998;Krause et al, 2011a).…”

Basic tools for setting environmental flows at the regional scale: application of the ELOHA framework in a Mediterranean river basin

“…Turić et al . () found a significant correlation ( p < 0.05) between water inflow in spring period in the month prior to sampling and Shannon's diversity index (H). In particular, frequent high‐magnitude flood pulses of prolonged duration, especially during spring, supported a higher abundance of Coleoptera and Heteroptera specimens and species richness compared with short and low‐magnitude flooding, suggesting that the occurrence of species of Coleoptera and Heteroptera may depend on the duration and intensity of flood pulses.…”

A comparison of methods for sampling aquatic insects (Heteroptera and Coleoptera) of different body sizes, in different habitats using different baits

“…Floodplains are unique habitats where sampling is dependent on the water level, which varies from month to month. Thus, food resources and the ability of species to fi nd food and colonize different habitats changes with the constantly fl uctuating water levels and is thus likely to infl uence the aquatic insect assemblages (Williams, 1996;Fairchild et al, 2003;Turić et al, 2015). In addition, in periodically fl ooded areas there is no dense vegetation and the absence of shading effects from trees affects the abundance of species and species composition of assemblages (Nilsson & Svensson, 1994;Nilsson & Söderberg, 1996;Lundkvist et al, 2001;Rundle et al, 2002;Schäfer et al, 2006).…”

“…Dytiscids are excellent swimmers (Nilsson, 1996) that capture their prey while actively swimming (Ribera et al, 1997). Hydrophiloidea are poor swimmers doi: 10.14411/eje.2017.017 changes in water levels and duration of the hydroperiod are the most important factors infl uencing the structure of the aquatic insect fauna (Schneider & Frost, 1996;Turić et al, 2015) because newly fl ooded wetlands are often nutrient-rich and may provide suitable feeding and reproduction possibilities for aquatic insects (Nilsson & Holmen, 1995;Batzer & Wissinger, 1996;Schneider, 1999;Larson et al, 2000;Wilcox, 2001). Research on aquatic insects in the Kopački rit area has increased during the last ten years.…”