Physical control on zooplankton distribution at the strait of Gibraltar during an episode of internal wave generation

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2010-01-01Department
BiologíaSource
Marine Ecology Progress Series, 408:79-95Abstract
We analyzed the effect of physical forcing on zooplankton biomass distribution in the
Strait of Gibraltar as a function of tidal phase. A set of 5 Longhurst-Hardy-Plankton-Recorder (LHPR)
casts were made along the main channel of the Strait during different phases of the tidal cycle to
determine how the hydrological processes taking place in the strait (mainly internal wave generation)
influenced the distribution and taxonomic composition of zooplankton biomass. A CTD coupled
to the LHPR net allowed a detailed study of the hydrological patterns created by the generation and
development of the internal waves. Plankton samples were analyzed using a semi-automatic method
for zooplankton discrimination (plankton visual analyzer) which is able to differentiate each individual
within a sample into specific taxonomic groups. The results show that the internal wave generation
on the main channel of the strait induces divergent processes causing a reduction of the zooplankton
biomass. Flow patterns within the internal waves lead to alternating bands of high and low
zooplankton biomass with varying taxonomic composition. Changes in taxonomic composition
appear to be the result of spatial differentiation between smaller (weak-swimming) and larger
(strong-swimming) taxa. This work demonstrates the necessity to consider and understand physical
processes when addressing biological patterns, especially in regions with intense hydrodynamic
regimes.
Subjects
Internal waves; Physical forcing; Zooplankton distributionCollections
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