Summary: | In order to investigate the taxonomic copepod
community structure and its relations with the climate
conditions in the Pacific Ocean, bimonthly samples
were made between February 2009 and April 2010.
Samples were collected by vertical tows between the
surface and the vicinity of the bottom with a 40 cm mouth
diameter and 335 µ mesh size standard zooplankton net.
At the beginning of the study water temperatures were
low indicating that La Niña conditions prevailed in the
bay. However, at the end of June, 2 °C warmer waters
associated with El Niño 2009-2010 arrival were detected.
These conditions persisted at least until February 2010,
and by April water temperature returned to normal. 57
copepods species were recorded, being Acartia tonsa,
Acartia lilljeborgi, Oithona plumífera, Centropages furcatus
and Nannocalanus minor the most representative
species. These five populations accounted most of the
90 % of the collected animals. Cluster and Non-Metric
Multidimensional Scaling (NMDS) methods show two
groups that seem to be associated with La Niña and
El Niño conditions. The analysis of similarities (ANOSIM)
indicated that these assemblages were different (r=0.411; p=0.01 %). Simper analysis indicated that A.
tonsa was the dominant population (85.4 %) at the end
of the 2008-2009 La Niña; this population was followed
by A. lilljeborgi (7.9 %) and Pareucalanus subtenuis (2.5
%). During the El Niño the dominance of A. tonsa disappeared
(32 %) while Oithona plumífera, Temora discaudata
and Undinula darwinii increased. At the end of El
Niño, species diversity and richness also changed. At
the end of the 2008-2009 La Niña conditions, 40 species
were recorded, while during El Niño the species
richness increased to 52 species.
|