The influence of antecedent floods on aquatic invertebrate diversity, abundance and community composition

Abstract

AbstractAnthropogenic alterations to flow regimes have been identified as a serious threat to river ecology. Such alterations can affect the magnitude and timing of high and low flows. It is therefore important to understand how antecedent flow conditions affect aquatic communities. However, few studies have investigated whether antecedent flow conditions cause common, generalizable and perhaps predictable changes in aquatic invertebrate communities across a range of rivers. Using 22 years of data from 66 river sites in New Zealand, we investigated (1) whether there were common relationships between the time since a recent flood and aquatic invertebrate communities within a site and (2) whether site differences in hydrology or physical habitat could explain the rate and direction of community changes. Aquatic invertebrate diversity, abundance and several aspects of community composition changed significantly with time since a flood. The rate and direction of these changes varied markedly between sites, but was at least partly explained by differences in site characteristics related to hydrological regime, physical habitat, land use and network location. Results suggested that alterations to hydrological regimes that change flood frequency will affect aquatic invertebrate diversity, abundance and community composition in many rivers. It may be possible to use site or hydrological regime characteristics to identify rivers in which aquatic invertebrate communities are more likely to change, and perhaps the direction of change. Our results also highlight the importance of accounting for recent floods in sampling programmes that compare water quality or ecosystem health over time within a site. Copyright © 2014 John Wiley & Sons, Ltd.