Geoscience Reference
In-Depth Information
CHAPTER 11
Can Mediterranean River Plants
Translate into Quality Assessment
Systems? Venturing
into Unexplored Territories
Ian Dodkins, Francisca Aguiar and Maria Teresa Ferreira
Forest Research Centre, Technical University of Lisbon, Portugal
Introduction
Azolla filiculoides
), whereas species associated with
oligtrophic conditions have low scores (e.g.
Nardia
compressa
). To assess the eutrophic condition of
a river section the mean of the species scores,
weighted by a cover value, is calculated. By
surveying macrophytes upstream and downstream
of a wastewater treatment works the extent of
eutrophication caused by the treatment works
can be established. In an assessment of the
MTR, Dawson
et al
. (1999) stressed that care
should be taken to ensure that the physical
habitats of the two surveys are similar when
making the comparison since physical differences
in the sites can alter the MTR score. Macrophyte
species-scoring indices appear to perform poorly
in Mediterranean rivers, which are naturally
eutrophic but have harsh ecological conditions,
with high magnitude winter spates and extended
summer droughts. Mediterranean rivers are often
ephemeral (no flow in the summer) or intermittent
(separate pools in a dry channel connected by
subsurface flow) (Argyroudi
et al
., 2008).
Within the Iberian Peninsula, regions closer to
the Atlantic coast (Lisbon, 702 mm yr
−
1
) receive
more rain annually than eastern regions (Barcelona
596 mm yr
−
1
, Valencia 429 mm yr
−
1
), although
the driest regions are in the interior, such as
Attempts to develop macrophyte indices for
assessing human impacts in Iberia suitable for
use within the Water Framework Directive (WFD)
(Council of the European Communities, 2000)
have not been very successful. It became apparent
that biological monitoring methods applied in
more northern temperate rivers of Europe were
not performing well in Mediterranean rivers.
The objective of this study was to review the
development of macrophyte biological monitoring
methods in Iberia and to examine which factors,
both
in
the
assessment
methods
and
in
the
characteristics
of
the
rivers,
may
be
limiting
the
ability
to
produce
macrophyte
indices
in
Mediterranean rivers.
The precursor of most aquatic macrophyte
monitoring methods in Europe is the Mean
Trophic Rank (MTR) system (Holmes
et al
., 1999).
It was developed in the UK for the purposes
of the Urban Wastewater Treatment Directive
(Council of the European Communities, 1991).
MTR scores each aquatic macrophyte based on an
expert opinion of the species' preference along a
perceived eutrophication gradient. Species strongly
associated with eutrophication score highly (e.g.
