Ff. Perez et al., WATER MASSES AND PHYTOPLANKTON BIOMASS DISTRIBUTION DURING SUMMER IN THE WEDDELL SEA MARGINAL ICE-ZONE, Oceanologica acta, 17(2), 1994, pp. 191-199
This study - carried out between the Elephant and the Orkney islands -
showed that spatial variability in the marginal ice-edge zone (MIZ) w
as greater than that found in open sea. Salinity and silicate contents
point to the existence of two fronts: the first - near Elephant Islan
d - separates the Surface Antarctic Water coming from Drake Passage fr
om the winter water originating in the Weddell Sea. This water is char
acterized by its high concentrations of nitrate (> 30 mu M) and silica
tes (> 80 mu M). The second front - near the South Orkney Islands unde
rgoes the influence by a less saline water lens (< 34 %), poor in nutr
ients (N-NO3 < 24 mu M) and rich in chlorophyll (> 3.5 mg Chl a 1(-1))
. Water masses circulation reveals the existence of a series of conver
gences and divergences which alternate along MIZ, together with differ
ent haline fronts. These fronts limit three differents zones, taking i
nto account the presence of chlorophyll. In zones where the surface la
yer presents both low salinity and stability with a thickness of about
40 m, chlorophyll contents are rather high - between 1.5 and 5 mg Chl
a. m(-3). On the other hand in the mixing vertical zone, these chloro
phyll contents are low (< 0.3 mg Chl a.m(-3)) while the frontal region
separating these two zones presents intermediate values and the exist
ence of deep subsurface maximum of chlorophyll. Horizontal variability
of integrated Values (on the whole of the euphotic zone) is clearly i
nferior to the one present in surface concentrations. PON/Chl a and PO
C/PON relations show their minimum levels in the pack-ice fusion water
, as an effect of the high photosynthetic activity.