These results strongly suggest that the changes in water column stratification and vertical attenuation coefficient prevail in the initiation process of winter phytoplankton blooms.
Such winter phytoplankton blooms are responsible for the early exhaustion of phosphate from the euphotic layer. They could have consequences
on the spring plankton food web characteristics by favouring the dominance of “microbial loops” to the detriment of larger phytoplankton and
zooplankton organisms food chain (Herbland et al., 1998; Sautour et al.,
2000).
The same processes could be expected for the 1 .oire river which is the
other large river on the French Adantic coast with similar discharges intensities and a plume of great extension over the continental shelf (Lazure & Jégou, 1998).
Bibliographic references
Herbland A., Delmas D., Laborde P., Sautour B., Artigas 1..F., 1998.
Phytoplankton spring bloom of the Gironde plume waters in the
bay of Biscav: early phosphorus limitation and food web consequences. Oceanol. Acta, 21, 27
l )-291.
Lazure P., Jégpu A.M., 1998. 3D-modelling of seasonal evolution of Loire
and Gironde plumes on Biscay bay continental shelf. Oceanol. Acta,
21,165-178.
Riley G.A., 1957. Phytoplankton of the north central Sargasso Sea. Limnol. Oceanogr., 2, 252-270.
Sautour B, Artigas L.F., Delmas D., Herbland A., Laborde P., 2000.
Grazing impact of micro- and mesozooplankton during an algal
spring bloom in coastal waters off the Gironde estuary J. Plankton
Res., 22(3), 531-552.
139
Such winter phytoplankton blooms are responsible for the early exhaustion of phosphate from the euphotic layer. They could have consequences
on the spring plankton food web characteristics by favouring the dominance of “microbial loops” to the detriment of larger phytoplankton and
zooplankton organisms food chain (Herbland et al., 1998; Sautour et al.,
2000).
The same processes could be expected for the 1 .oire river which is the
other large river on the French Adantic coast with similar discharges intensities and a plume of great extension over the continental shelf (Lazure & Jégou, 1998).
Bibliographic references
Herbland A., Delmas D., Laborde P., Sautour B., Artigas 1..F., 1998.
Phytoplankton spring bloom of the Gironde plume waters in the
bay of Biscav: early phosphorus limitation and food web consequences. Oceanol. Acta, 21, 27
l )-291.
Lazure P., Jégpu A.M., 1998. 3D-modelling of seasonal evolution of Loire
and Gironde plumes on Biscay bay continental shelf. Oceanol. Acta,
21,165-178.
Riley G.A., 1957. Phytoplankton of the north central Sargasso Sea. Limnol. Oceanogr., 2, 252-270.
Sautour B, Artigas L.F., Delmas D., Herbland A., Laborde P., 2000.
Grazing impact of micro- and mesozooplankton during an algal
spring bloom in coastal waters off the Gironde estuary J. Plankton
Res., 22(3), 531-552.
139