Montecino¹, V., P. Paolini², R. Astoreca¹, M. A. Paredes¹ and J. Rutllant³

¹Dep. Ciencias Ecológicas, Fac. Ciencias, U. Chile, Casilla 653, Santiago, Chile, E-mail: clorofil@uchile.cl, ²Centro Estudios Espaciales and ³Dep. Geofísica, Fac. Ciencias Físicas y Matemáticas, U. Chile.

In situ and satellite chlorophyll-a data along the coast in north-central Chile considering multiscale environmental variability

Phytoplankton distribution in the Humboldt Current System is characterized by high temporal and low spatial variability. Changes include: responses to quasi-weekly upwelling favorable wind (UFW) events; in the nutricline depth associated with Coastal Trapped Waves (CTW’s); the seasonal cycle and interannual changes associated with the ENSO cycle. Between 18-30°S chlorophyll-a (Chl-a) maxima (minima) centered on austral summer (winter) coincide with the season of maximum (minimum) UFW’s, and although extensive filaments have been detected, higher mean Chl-a values are within 50 km of the coast.

Ship and satellite Chl-a data at both extremes of the ENSO cycle and during transitions in the last decade (since 1997 for SeaWiFS) from Antofagasta (23ºS), Coquimbo (30ºs) and Valparaíso (33ºS) suggest that, during full cycles of UFW's the phytoplankton response patterns to the cold/warm ENSO signal may be offset by opposite thermal conditions related with seasonal and/or intraseasonal (CTW’s) variabilities. However in 67% of the cases under similar ASL phase and local upwelling conditions no differences were found in ship Chl-a comparing the extreme ENSO phases. For phytoplankton patterns off north-central Chile, this approach revealed important time gaps that should guide monitoring and research efforts.

JGOFS-Chile, FONDAP-Humboldt, DID and PRODAC at U. Chile.