Assessment of European streams with diatoms, macrophytes ...

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1768 D. Hering et al. Table 5 Correlation analyses of metrics and eutrophication/organic pollution gradients. max r 2 : the maximum r 2 of all metrics significantly correlating to a stressor gradient; 75 perc: the 75th percentile of the r 2 values of all metrics significantly correlating to a stressor gradient; share sg: the share of metrics significantly correlating to a stressor gradient, in relation to the total number of metrics used for the organism group. 0.82). The share of significantly correlating metrics was 50%, indicating that different metrics best reflect the eutrophication/ organic pollution gradients in the individual stream types. For mountain streams macroinvertebrate metrics responded more strongly to the eutrophication/ organic pollution gradient than for all lowland streams. Conversely, for stream types S05/S06 and O02 some metrics were strongly correlated [average score per taxon (ASPT) in S05/S06: r 2 ¼ 0.72; the overall strongest correlation for invertebrate metrics and eutrophication/organic pollution intensity]. Similar to macrophytes (but not diatoms) this indicates the lack of generally applicable metrics (i.e. most metrics are best suited for individual stream types). For mountain streams, fish metrics responded poorly to the eutrophication/organic pollution gradients, whilst in the individual lowland stream types one or more fish metrics explained from 40% to 70% of the variability, although none of the metrics were found to be applicable for the entire lowland stream type group. The metric ‘density of native benthic species’ correlated most strongly to the eutrophication/organic pollution gradient (stream type D03/ K02; r 2 ¼ 0.69). Land use All organism groups responded less strongly to catchment land use than to eutrophication/organic pollution gradients (Table 6; Appendix). Most diatom metrics reflected catchment land use to some degree (>80% of the metrics tested for both all mountain and all lowland streams), but correlation coefficients were weak (maximum r 2 < 0.4 in four of the six stream groups). The strongest correlation was found for the metric ‘Rott index calculated with Omnidia’ (stream type S05/S06; r 2 ¼ 0.81). At least one macrophyte metric correlated significantly to land use gradients in all stream type groups, although in five of the six stream groups the maximum r 2 was 0.2, but at the individual stream type level several metrics were more strongly related to the catchment Ó 2006 The Authors, Journal compilation Ó 2006 Blackwell Publishing Ltd, Freshwater Biology, 51, 1757–1785
Table 6 Correlation analyses of metrics and land use gradients. See Table 5 for details. land use gradient: ‘ASPT’ (stream types S05/S06, r 2 ¼ 0.66; stream types D03/K02, r 2 ¼ 0.39) and ‘Plecoptera (%)’ (stream type O02, r 2 ¼ 0.44). Fish metrics were weakly correlated to land use in mountain streams (all correlations with r 2 < 0.2), while in lowland stream types the explanatory power of the fish metrics was similar to that found for invertebrate metrics. The strongest correlations were for the metrics ‘number of lithophilic species’ (stream types S05/S06, r 2 ¼ 0.4) and ‘density of limnophilic species (n ha )1 )’ (stream types D03/K02, r 2 ¼ 0.4). Hydromorphology (reach scale) The impact of hydromorphological degradation (reach scale) on the biological metrics tested here was generally less obvious than the impact of eutrophication/organic pollution and land use (Table 7; Appendix). Diatoms showed almost no response to hydromorphological degradation on the reach scale. The metric ‘IPS’ (polluo-sensibilité) correlated most strongly (stream type O02; r 2 ¼ 0.41). Similarly, the response of macrophyte metrics to hydromorphological gradients was weak. In mountain streams, the Response of organism groups to stress 1769 best response was found for the metric ‘number of submerged species’ (r 2 ¼ 0.25), while in the lowland streams the response was restricted to single stream types. Overall, the strongest correlation was found for the metric ‘evenness (typical species)’ (stream type D03/K02; r 2 ¼ 0.4). In contrast to benthic diatoms and macrophytes, macroinvertebrates responded more strongly to hydromorphological (reach scale) gradients. In all stream types at least one metric was significantly correlated to this stress gradient, with a maximum r 2 of 0.51 (‘German Fauna Index D01’ in stream type O02). In particular the metrics ‘Ephemeroptera, Plecoptera and Trichoptera taxa (EPT)’ and the ‘German Fauna Indices’ responded strongly. By contrast, the response of fish metrics to hydromorphological gradients was restricted to lowland streams, with the metric ‘density of native benthic species (n ha )1 )’ correlated most strongly (stream type O02, r 2 ¼ 0.46) to impairment. Hydromorphology (microhabitat scale) Diatom metrics responded to alterations in microhabitat composition; however, responses were generally Table 7 Correlation analyses of metrics and hydromorphological (reach scale) gradients. See Table 5 for details. Ó 2006 The Authors, Journal compilation Ó 2006 Blackwell Publishing Ltd, Freshwater Biology, 51, 1757–1785
Page 1 and 2: Freshwater Biology (2006) 51, 1757-
Page 3 and 4: et al., 1999; Sonneman et al., 2001
Page 5 and 6: Sampling design The main stress typ
Page 7 and 8: priate for most metrics (Lorenz, Ki
Page 9 and 10: Table 4 Biological metrics included
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Page 19 and 20: Hering et al., 2004b; Lorenz et al.
Page 21 and 22: Battarbee R.W., Flower R.J., Juggin
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Page 25 and 26: Appendix Spearman rank correlation
Page 27 and 28: Appendix (Continued) All mountain s
Page 29: Appendix (Continued) Lowland stream

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