The biological schcmc is a simplificd vcrsion representation of the pelagic ecosystem (tig. 1). Ihc model is conceptualized for a shclf sea including thc shallow sea characterized by the replenishment of the mixed
layer with nutrients from the bottom. Ciycling of three elements is
modelized: nitrogen, phosphorus and silicon. It takes into account
thrcc groups of phytoplankton, thc diatoms that contribute to thc silicon cyclc, and two group of non-siliceous phytoplankton rcprcsentecl
by dinoflagellates and nanophytoplankton. In the phytoplankton,
only the diatoms sink. Thc class of small phytoplankton allows to
take into account thc oligotrophic system of the oceanic waters, and
provides a better rcprescntation of thc ammonium consumption and
regeneration after a microphytoplanktonic bloom. Thc inorganic matter is regenerated through thc zooplankton excretion, and through
thc remineralization of dead cells and faeces.
Only a small part of this detritus remains suspended in the water
column and is immediately regenerated, thc major part sinks onto the
bottom. Thc benthic compartment simulatcs the storage, regeneration
and crosion processcs. The detritical pool on thc bottom has been introduced to store the detritus and to create the replenishment of the
water column.
Calibration and validation with in situ measurements
Temporal evolution
To calibrate and validate this model, we have uscd various data, with
several spatial and tcmporal scales. Only some rcsults arc shown here
to illustratc thc characteristics of the bay of Biscay. We will first show
the comparison with data obtained from the Réphy (network of phytoplanktonic monitoring) and the RNO (national water cjuality monitoring network).
Simulated annual cyclcs of nutrient concentrations are in the observed
rangc (fig. 2a-2e). Thc two years represented here illustrate well the seasonal cycle of nutrient concentrations. Inotganic nitrogen and inorganic
phosphoms show vem high concentrations in winter and spring, attesting the coastal water enrichment bv thc river. In summer, the nutrient
concentration dntps down, due to the river flow decrease and to the algae consumption. The phosphorus concentrations increase during
summer and autumn because of the remineralization processes, the
low primary production and thc small increasc of river flows.
Chlorophyli a has been calibrated with in situ measurements from Réphy
over the years 1994 to 1999 (fig. 2e); thc results shown hcrc are those obtained for the bay of Vilaine. Thc model reproduces well the different
level of production between the rainv years (1994, 1995 and 1998) and the
dr\- years (1996 and 1997). The amount and the onset of the spring
bloom are in good agreement with the observations. In the most productive years, spring concentrations of chlorophyll areach 8-10 milligrammes
108
layer with nutrients from the bottom. Ciycling of three elements is
modelized: nitrogen, phosphorus and silicon. It takes into account
thrcc groups of phytoplankton, thc diatoms that contribute to thc silicon cyclc, and two group of non-siliceous phytoplankton rcprcsentecl
by dinoflagellates and nanophytoplankton. In the phytoplankton,
only the diatoms sink. Thc class of small phytoplankton allows to
take into account thc oligotrophic system of the oceanic waters, and
provides a better rcprescntation of thc ammonium consumption and
regeneration after a microphytoplanktonic bloom. Thc inorganic matter is regenerated through thc zooplankton excretion, and through
thc remineralization of dead cells and faeces.
Only a small part of this detritus remains suspended in the water
column and is immediately regenerated, thc major part sinks onto the
bottom. Thc benthic compartment simulatcs the storage, regeneration
and crosion processcs. The detritical pool on thc bottom has been introduced to store the detritus and to create the replenishment of the
water column.
Calibration and validation with in situ measurements
Temporal evolution
To calibrate and validate this model, we have uscd various data, with
several spatial and tcmporal scales. Only some rcsults arc shown here
to illustratc thc characteristics of the bay of Biscay. We will first show
the comparison with data obtained from the Réphy (network of phytoplanktonic monitoring) and the RNO (national water cjuality monitoring network).
Simulated annual cyclcs of nutrient concentrations are in the observed
rangc (fig. 2a-2e). Thc two years represented here illustrate well the seasonal cycle of nutrient concentrations. Inotganic nitrogen and inorganic
phosphoms show vem high concentrations in winter and spring, attesting the coastal water enrichment bv thc river. In summer, the nutrient
concentration dntps down, due to the river flow decrease and to the algae consumption. The phosphorus concentrations increase during
summer and autumn because of the remineralization processes, the
low primary production and thc small increasc of river flows.
Chlorophyli a has been calibrated with in situ measurements from Réphy
over the years 1994 to 1999 (fig. 2e); thc results shown hcrc are those obtained for the bay of Vilaine. Thc model reproduces well the different
level of production between the rainv years (1994, 1995 and 1998) and the
dr\- years (1996 and 1997). The amount and the onset of the spring
bloom are in good agreement with the observations. In the most productive years, spring concentrations of chlorophyll areach 8-10 milligrammes
108