Production of Calanus chilensis in the upwelling area of Antofagasta, northern Chile

Abstract

Salinities, temperatures, chlorophyll a (CM a), and quantitative samples of Calanus chilensis were obtained at -17 d intervals from June 1996 to June 1997 at 3 stations in the Bay of Mejillones, northern Chile, and from 53 statlons in a broad-scale survey of surroundmg waters from 17 to 21 December 1996. Temporal variabihty in cohort structure precluded direct estimates of production from samples. However, lack of relationship of eggs per female and stage-frequency distribution with chl a in the broad survey, the apparently continuous development (and presence of adult males) during the time series, and the seasonal correlation of female body size with temperature, but not chl a, all suggest that food supply d~d not determine production rates. Therefore, temperature-dependent production was estimated, from sample biomasses and from laboratory rearings of C. chilensis and other species, as 45 mg C m-3 yr-'. This is substantially lower than comparable estimates for C. finmarchicus off eastern Canada and northeastern USA. However, broad-scale production in December 1996 was much higher than that at the 3 time-series stations. A production:biomass ratio of 45, compared with 8 for C. finmarchicus off eastern Canada, is compatible with the general view that the upwelling area off northern Chile is part of one of the world's most produchve marine systems.

Upwelling shadows at Mejillones Bay (northern Chilean coast): a remote sensing in situ analysis

“…However, since the shadow breaks apart after 4 to 7 days, zooplanktonic organisms developed inside the bay soon would mix with the rest of the population upon the beginning of the spin-down phase. This would explain sudden disappearances of the Calanus population from the bay, as noted by Escribano & McLaren (1999). Thus, the UPS seem to play an important role in the biological production of Mejillones Bay.…”

Distribución de eufáusidos en el sistema de surgencia frente a la península de Mejillones (23°S) asociada a condiciones previas y durante El Niño 1997-98

“…La concentración de clorofila-a se estimó a través de calibración in situ del fluorómetro utilizado en este estudio (Escribano y McLaren, 1999). Para analizar la influencia de la condición El Niño, se dividió la serie de tiempo en dos períodos distintos, pero conteniendo los mismos meses, no-Niño (junio 1996-enero 1997) y Niño (junio 1997-enero 1998).…”

“…El área costera de la península de Mejillones en el norte de Chile es uno de los sitios de surgencia donde su influencia induce altas tasas de producción primaria a través de todo el año (Rodríguez et al, 1991;Marín et al, 1993;Escribano, 1998). La alta producción de fitoplancton promueve un crecimiento continuo de copépodos herbívoros en esta zona (Escribano y McLaren, 1999), y a su vez sustenta elevadas abundancias de varias especies de eufáusidos en el norte de Chile (Antezana, 1978). No obstante su alta capacidad productiva, el SCH está sujeto a drásticas fluctuaciones interanuales, debido a la alternancia de eventos cálidos (El Niño) y eventos fríos (La Niña) (Arntz y Fahrbach, 1996;Escribano e Hidalgo, 2000a).…”

Evolution and biological effects of the 1997–98 El Niño in the upwelling ecosystem off northern Chile

“…We believe that these changes resulted from warmer temperatures associated with E1 Nifio conditions. The accelerating effect of temperature on copepod growth and development shortens their generation time [Escribano et al, 1998], which in C. chilensis •nay be less than 30 days in the field [Escribano and McLaren, 1999]. Higher growth rates can explain the observed increase in population size during E1 Nifio, as the number of cohorts probably increased.…”