PERSISTING EFFECTS OF RIVER REGULATION ON EMERGENT AQUATIC INSECTS AND TERRESTRIAL INVERTEBRATES IN UPLAND FORESTS

Authors


Correspondence to: M. Jonsson, Department of Ecology and Environmental Science, Umeå University, SE-90187 Umeå, Sweden.

E-mail: micael.jonsson@emg.umu.se

ABSTRACT

River regulation can alter the structural complexity and natural dynamics of river ecosystems substantially with negative consequences for aquatic insects. However, there have been few studies of regulation effects on the export of emergent insects into terrestrial ecosystems. In northern Scandinavia, we compared emerged aquatic insect and terrestrial invertebrate biomass between four strongly regulated and four free-flowing rivers using fortnightly measurements at three upland-forest blocks in each over one summer. The biomass of emerged aquatic insects was significantly lower along regulated rivers than free-flowing rivers. Biomass in Linyphiidae, Opiliones, Staphylinidae, total Coleoptera, Formicidae and total terrestrial invertebrates was also lower along regulated rivers. Aquatic insect biomass did not explain the entire regulation effect on terrestrial invertebrates but did explain significant variations among Linyphiidae, total Coleoptera, Formicidae and total terrestrial biomass. Variations in Formicidae also explained significant variance among several terrestrial taxa, suggesting some keystone role in this group. Overall, our results suggest that river regulation affects upland-forest invertebrate communities, with at least some of these effects arising from links between aquatic emergence and terrestrial predators. The data highlight the need to consider areas beyond the riparian zone when assessing the effects of river regulation. Copyright © 2012 John Wiley & Sons, Ltd.

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