Abstract
We determined the distribution and abundance of pelagic copepods in the eastern equatorial Pacific between the coast of Ecuador and the Galapagos Islands under oceanographic conditions associated with the weak La Nina event of 2001. In September-October 2001, negative anomalies of sea surface temperature from this event still remained in the eastern equatorial Pacific, mainly between Ecuador and the Galapagos Islands. The event allowed the incursion of the Humboldt Current farther north and of the Equatorial Undercurrent into the study area, favouring a strong Equatorial Front and upwelling processes. There was evidence of mesoscale eddies in the study area and of the presence of the South Equatorial Current going westward at about 1°N. We identified 107 copepod species and analyzed the distribution of the 10 most abundant ones: Oncaea venusta, Subeucalanus pileatus, S. crassus, S. subtenuis, Paraeucalanus attenuatus, Pleuromamma borealis, Scolecithrix danae, Clausocalanus farrani, Temora discaudata and Calanus chilensis . Copepod distribution and abundance exhibited marked latitudinal differences related to the oceanographic conditions; abundance was highest to the southeast of the Galapagos Islands. Oncaea venusta, Pleuromamma borealis, Calanus chilensis , and Subeucalanus subtenuis were the species that best defined the Equatorial Front and the upwelling process.
Highlights
Tropical systems offer an interesting example of the intensification of climate processes or changes because their boundaries expand or contract in function of such processes (Sharp, 2004)
SUMMARY: We determined the distribution and abundance of pelagic copepods in the eastern equatorial Pacific between the coast of Ecuador and the Galapagos Islands under oceanographic conditions associated with the weak La Niña event of 2001
The event allowed the incursion of the Humboldt Current farther north and of the Equatorial Undercurrent into the study area, favouring a strong Equatorial Front and upwelling processes
Summary
Tropical systems offer an interesting example of the intensification of climate processes or changes because their boundaries expand or contract in function of such processes (Sharp, 2004). It is fed in the northeast by a branch of the North Equatorial Countercurrent and in the southeast by the Humboldt Current, which flows northward from Peru before veering west towards the Galapagos Islands, forming the southern boundary of the Equatorial Front (Wooster, 1969) In this area, biological studies have focused exclusively on the chlorophyll concentration, primary production measurements, euphausiids, and the volume of zooplankton (Brinton, 1962; Arcos, 1978; Cornejo and Antezana, 1979; Jiménez and Bonilla, 1980; Jiménez, 1983; Córdova, 1989; Torres and Tapia, 2000; Torres et al, 2004)
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