Advisor(s)
Abstract(s)
A 8-yr record of monthly observations (2000-2002 and 2007-
2011) in Azibo Reservoir were used (1) to describe crustacean
zooplankton interannual and seasonal variability; (2) to
understand the environmental forcing underlying zooplankton
dynamics. This reservoir was chosen because unlike the majority
of existing reservoirs, water level fluctuations are not very
pronounced, never exceeding 3m. Furthermore, the introduction
of pike (Esox lucius L.) in the 1990’s led to a marked reduction of
cyprinid fish abundance. Consequently, fish predatory pressure is
regarded to be too low to drive zooplankton community. Without
the interference of internal disturbances generated by extreme
anthropogenic water level fluctuations and by fish predation on
the zooplankton, this reservoir provides a good environment
for studying the reservoir general limnology, filling the lack of
long term data on this kind of aquatic ecosystems. ANCOVA and
Pearson correlation analyses indicated that total phosphorus,
Secchi depth, conductivity and pH, as well as, cyanobacteria and
diatoms abundance were significantly related to precipitation.
A seasonal cycle in zooplankton composition common to all the
years sampled was identified. This pattern consisted of a marked
separation between a winter and a summer assemblage (ANOSIM:
R=0.841; p=0.01). The winter zooplankton assemblage was
characterized by a higher abundance of Daphnia longispina/pulex.
By contrast, in summer and autumn Ceriodaphnia pulchella,
Diaphanosoma brachyurum and the copepod C. numidicus were
dominant. BIOENV analysis identified temperature, conductivity,
Secchi depth, diatoms and cyanobacteria abundance as the
environmental variables most highly forcing seasonal zooplankton
composition and species abundance. Results also provided
evidence of interannual variability in the timing of zooplankton
succession. In fact, the timing of appearance and/or annual
peak densities varied among years. These data on crustacean
zooplankton assemblage will certainly to provide a baseline
against which future changes on this reservoir can be measured,
allowing the evaluation and the prediction of the impacts of land
use modifications and of climate change on ecosystem integrity.
Furthermore, the obtained information can also be extrapolated to
other Mediterranean reservoirs.
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Keywords
Citation
Geraldes, Ana Maria; Afonso, Silvino (2014). Environmental forcing of crustacean zooplankton in a Mediterranean Reservoir (River Douro Watershed, North-western Iberia): effects on species abundance and variability. In XVII Congresso of Iberian Association of Limnology. Santander