Characterization of intra-, inter-annual variability SST, phytoplankton pigment concentration & zooplankton on shelf zone of Humboldt Current System Chile

Chl-a rich waters were dominated by net phytoplankton in summer but the smaller phytoplankton (<20um) contributed in equal proportion to the total during the autumn. Off northern Chile, time series analyses (December 1991 - January 1998) of female length and abundance of Calanus chilensis, a key herbivore, show large inter-annual fluctuations. Although SST shows much inter-annual variation, the seasonal signal appears as the most important in influencing its biology and its ecological response is highly dependent on SST variation.

On a year-to-year scale, the abundance of C. chilensis is associated with the annual regime of temperature but on scales longer than a year, factors other than temperature appear to regulation population size. Inter-annual variation of other demographic characteristics of C. chilensis, like female length, appear to be controlled by remote fluctuations associated with the El Nino-Southern Oscillation cycle through temperature.

Dominant copepod species appear to be transported from the coast ot the offshore through filaments and upwelling plumes, in association with phytoplankton biomass; these mesoscale features induced local changes in copepod abundance, composition and distribution.