Multi-scale approach using phytoplankton as a first step towards the definition of reservoirs ecological status.
Data
2009
Autores
Cortes, Rui
Cabral, João Alexandre
Lourenço, Martinho
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Resumo
The growing need to analyse the present state of ecosystems and predict their rate of change
has triggered a demand to explore species environment relationships for assessing alterations
under anthropogenic influence. The Water Framework Directive (WFD) requires the
definition of different types of water bodies which are of relevance when assessing their
ecological status. The main aim of this study was to define of the types of Portuguese
reservoirs located in the North and Centre of Portugal and to assess their ecological status
using phytoplankton as water quality indicators. In this study, sampling was carried out in
34 reservoirs during four seasons (spring, summer, autumn and winter), through a period of
8 years (1996–2004).
Two groups of reservoirs could be distinguished, from the multivariate statistical
analysis based on environmental variables and on phytoplankton assemblages: G1, lowland
reservoirs located in the main rivers (Douro and Tagus), with a very low residence time,
characterized by higher water mineral content (hardness and conductivity), higher concentrations
of nutrients (namely, nitrates), dominated by Bacillariophyta and Chlorophyta
and characterized by the presence of tolerant of poor environmental conditions species,
mainly associated with meso and eutrophic states of water bodies; G2, deeper high altitude
reservoirs, largely located in tributaries, with high residence time, presenting a specific
species composition under reference conditions, with higher species richness. The transition
from deeper and colder reservoirs (reference sites) to shallow and warmer reservoirs
(impaired sites), was evident in G2, contrarily to G1, and was mostly positively correlated to
organic pollution and mineral gradients. The results presented here are fundamental for the
development of a routine for monitoring ecological status according to the WFD.
Descrição
Palavras-chave
Phytoplankton , Ecological status , Reservoirs , Water Framework Directive , Multivariate analysis , Ecological indicators
Citação
Cabecinha E. et al, 2009