Ra. Varela et al., A SIMULATION ANALYSIS OF VARIOUS BIOLOGICAL AND PHYSICAL FACTORS INFLUENCING THE DEEP-CHLOROPHYLL MAXIMUM STRUCTURE IN OLIGOTROPHIC AREAS, Journal of marine systems, 5(2), 1994, pp. 143-157
A detailed analysis of the Varela et al. (1992) coupled physical/biolo
gical model shows the influence of several physical and biological fac
tors on the depth and magnitude of the deep chlorophyll maximum (DCM).
We show here the importance of a careful computation of the eddy diff
usion coefficient below the thermocline for a correct estimation of th
e depth and magnitude of the DCM. We also show that light extinction i
s critical in determining the DCM depth. Atmospheric nitrate supply in
fluences the vertical phytoplankton distribution only in the upper sur
face layer, leaving unaffected the DCM. Among the biological factors c
onsidered, zooplankton grazing on large phytoplankton and heterotroph
grazing on small phytoplankton affect the DCM magnitude but not its de
pth. The large phytoplankton cells (> 20 mu M) seem to have advantages
when compared to smaller cells (< 20 mu M) when the nutrient supply i
ncreased, but small cells almost always constituted the dominant phyto
plankton fraction.