Biological Quality On The Basis Of Macroinvertebrates In Dammed Habitats Of Some Estonian Streams, Central - Baltic Europe

We assessed the impacts of damming on the biological quality of Estonian streams. A total of 24 dammed sites on 22 streams were sampled. Standard samples were taken during two consecutive springs, 2009 and 2010 in three habitat locations: above dam (reservoir), immediately below dam, and at an undisturbed (reference) site nearby. To estimate biological quality, the national multimetric index (based on five pollution-sensitive and/or general quality metrics) was used. To estimate direct hydromorphological effects on macroinvertebrates, the locally adapted index, Macroinvertebrates in Estonia: Score of Hydromorphology (MESH) was employed. We found a significant decrease in the biological quality of the above-dam sites compared to the undisturbed sites (probably due to accumulation of fine sediments and lower flow velocity). Of the five ordinary quality indicators tested, only one (ASPT index) was significantly different between the below-dam sites and the undisturbed sites. However, the MESH indicated significant stress of macroinvertebrates both at the above-dam and below-dam sites, even when flow velocity and bottom type at the below-dam sites was similar to that at the undisturbed sites. At the same time, hydrochemical parameters were constant among the three habitats. ((c) 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)