Exploring longitudinal trends and recovery gradients in macroinvertebrate communities and biomonitoring tools along regulated rivers.

Flow regime alteration by dams has been recognized as a major impact factor for aquatic communities. Spain is currently the member state of the EU with the largest number of large reservoirs. With the broad objective of diminishing the ongoing river degradation trend through the management of environmental flows and the use of biomonitoring tools, we investigated the effects of dams on stream macroinvertebrates in several regulated rivers in Spain with contrasting environmental settings. Specifically, we studied longitudinal trends in macroinvertebrate communities to test: i) if currently used biomonitoring tools and multivariate community analyses can detect hydrological impact responses and biological recovery; ii) if an applicable quantification of the recovery gradient, in terms of distance downstream from dams, can be obtained for Iberian fluvial systems; iii) if macroinvertebrate community structure respond different to flow regulation, depending on the contrasting environmental river typologies; and iv) if the type and intensity of hydrological alteration modulates the observed community responses/recovery.