Spatial variance of profundal and sublittoral invertebrate benthic communities in response to eutrophication and morphological pressures Papers collated based on and as part of the EU funded project WISER (funded by the European Union under the 7th Framework Programme, contract No. 226273) Francesca Pilotto 1, *, Gary Free 2 , Ana Cristina Cardoso 3 , Georg Wolfram 4 and Angelo G. Solimini 1 With 3 figures and 3 tables Abstract: Invertebrate communities inhabiting different lake zones are expected to respond differently to natural environmental variation and anthropogenic stressors. We used multivariate statistical methods in order to quantify the effects of eutrophication and morphological pressures on the spatial structure of the invertebrate benthic com- munities at two depth zones (profundal and sublittoral) in subalpine lakes in Italy, Germany and Austria . In both lake zones, environmental variables related to eutrophication pressures (mid-lake total phosphorus and chlorophyll- a) were signiicant in structuring the invertebrate community (permutation test: p < 0.01). Three variables relating to morphological pressures (diversity of macrophyte growth forms, sum of pressures in the lake shore, and percentage of natural land cover within a 200 m stretch from the lake shore) were signiicant (permutation test: p < 0.01) in the sublittoral zone, while in the profundal zone none of the variables included in the analysis related to morphological pressures were signiicant in structuring the invertebrate community. Variance partitioning analysis showed that profundal communities were mainly affected by eutrophication (8.6 % of total variance; p = 0.005), while in the sub- littoral zone eutrophication accounted for only 0.5 % (p = 0.04) of total variance. The effects of morphological pres- sures could be tracked only in the sublittoral zone, where it accounted for 0.8 % of total variance (p = 0.015). The spatial component was responsible for a large part of the total variance (58.7 % in the profundal, p = 0.005; 44.2 % in the sublittoral zone, p = 0.005) and had interactions with stressor variables in both lake zones. Therefore the analysis of spatial patterns should be included in assessment systems relating invertebrate assemblages to pressures. Key words: lake sublittoral zone, lake profundal zone, invertebrate community, eutrophication, morphological pressures, RDA, variance partitioning. Authors’ addresses: 1 Sapienza University of Rome, Piazzale Aldo Moro 5, 00185 Roma, Italy. 2 Environmental Protection Agency, McCumiskey House, Richview, Clonskeagh Road, Dublin 14, Ireland. 3 European Commission, Joint Research Centre, Institute for Environment and Sustainability, Via Enrico Fermi, 21020 Ispra, Italy. 4 DWS Hydro-Oekologie GmbH, Zentagasse 47, 1050 Vienna, Austria. * Author for correspondence; francesca.pilotto@uniroma1.it Fundam. Appl. Limnol. Vol. 180/2, 101–110 Article Stuttgart, March 2012 © 2012 E. Schweizerbart’sche Verlagsbuchhandlung, Stuttgart, Germany www.schweizerbart.de DOI: 10.1127/1863-9135/2012/0206 1863-9135/12/0206 $ 2.50 Introduction Despite the awareness of the need of a pressure-re- lated assessment tool, a quantitative analysis of the unique effects of different pressures on the structure and composition of lake benthic communities is still lacking. This is due to the dificulty of disentangling the signature of different explanatory variables such as those associated to natural spatial and temporal variability and those associated with different stress- eschweizerbart_XXX