Lakes and Watercourses
Lakes and Watercourses
Lakes and Watercourses
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Class 3. Clear effects of disturbance. Substantial impact on assemblages<br />
of organisms <strong>and</strong> their habitat. The bottom fauna deviates moderately<br />
from its normal undisturbed state.<br />
Class 4. Pronounced effects of disturbance. The community deviates<br />
markedly from its undisturbed state.<br />
Class 5. Very great effects of disturbance. Only a few tolerant species<br />
occur.<br />
Reference values specific to a given locality should be used as far as<br />
possible. These may be derived in several ways. They can be estimated<br />
on the basis of historical surveys carried out in the area or they may be<br />
obtained from surveys made in similar but unaffected lakes or watercourses<br />
in the vicinity. If this is not possible, the reference values given in<br />
Table 43 may be used.<br />
TABLE 43.<br />
Reference values for differing habitats <strong>and</strong> natural geography. Reference values comprise<br />
the 25th percentile (75th percentile for O/C index) in data from lakes <strong>and</strong> watercourses<br />
included in the 1995 survey of lakes <strong>and</strong> watercourses, which, as far as possible, are<br />
unaffected. The data used is described in detail in the background report. The boundaries<br />
between the natural geographical regions are shown in Figure 3. The figures given<br />
for the profundal zone of lakes are not specific to regions.<br />
Natural geographical region<br />
Arctic/ Northern Middle Southern Boreo- Nemoral<br />
alpine boreal boreal boreal nemoral<br />
<strong>Watercourses</strong><br />
Shannon-Wiener’s diversity index 1.96 2.56 2.34 2.11 1.97 1.89<br />
ASPT-index 5.8 6.2 6.0 5.5 4.7 4.8<br />
Danish fauna index* 5 5 5 5 5 5<br />
Acidity index 6 6 6 6 6 6<br />
Littoral zone of lakes<br />
Shannon’s-Wiener’s diversity index 1.00 1.06 1.46 1.98 2.15 2.01<br />
ASPT-index 4.6 5.0 5.0 5.0 5.1 4.5<br />
Danish fauna index 3 4 4 4 4 4<br />
Acidity index 6 6 6 6 6 6<br />
Profundal zone in lakes<br />
BQI-index 2<br />
O/C-index 8.5<br />
* Reference values for regions 4, 5 <strong>and</strong> 6 have been adjusted upwards (from 4 to 5) in response to<br />
comments received from consultants, county administrative boards etc working in these regions.<br />
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