Publisher :
Place of publication :
Publication year : 2009
Thematic : Biodiversity
Language : English
Note
The Water Framework Directive (WFD)
requires the hydromorphological assessment of water
bodies, thereby acknowledging the importance of these
features in supporting biological quality elements and
providing a more complete ecological characterization
of surface water bodies. Using a dataset covering
mainland Portugal (about 300 sites spread along the
different river types) and based on the River Habitat
Survey (RHS) field methodology, our aim was to test
the spatial variation and the relative role of an array of
multi-scale habitat descriptors, in order to: (a) to
analyse their geographical variation; (b) to identify the
principal variables that express human disturbance;
and (c) to assess how three different aquatic communities
(invertebrates, fish, and macrophytes) were
related to those environmental descriptors. We found
that hydromorphological variables described by RHS
varied significantly over large geographical scales and
were more strongly associated with the principal
catchments rather than river type (derived from
climatic, geological, and typological factors). RHSderived
descriptors were of greater importance in
assessing disturbance and were closely related to land
use and vegetation on the banks and along the river
corridor, despite the considerable geographical variation.
Habitat variables were more clearly associated
with macrophytes and fish than with the benthic
macroinvertebrates, a facet of sampling design, since
the scale of biological survey for the former two
biological groups approaches the scale used to characterize
the surrounding environment. An array of
environmental variables, ranging from instream features
to bankside and river corridor land use features,
was associated with each community, making it
difficult to discern any common underlying pattern.
Based upon our findings, we propose that hydraulic
variables should be included in hydromorphological
assessment to improve both the performance of
physical indicators and the correspondence with the
demands of the WFD.
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Keywords : Microhydromys richardsoni
Encoded by : Pauline Carmel Joy Eje
