Ra. Varela et al., MODELING PRIMARY PRODUCTION IN THE NORTH-SEA USING THE EUROPEAN-REGIONAL-SEAS-ECOSYSTEM-MODEL, Netherlands journal of sea research, 33(3-4), 1995, pp. 337-361
The primary production module incorporated in the European Regional Se
as Ecosystem Model (ERSEM) is described in detail. It considers two ph
ytoplankton groups, diatoms and autotrophic flagellates, and four diff
erent nutrients: nitrate, ammonia, phosphate and silicate (only for di
atoms). All the related state variables and fluxes are represented in
terms of carbon, nitrogen, phosphorus and silicon. The potential carbo
n growth rate process is estimated by considering that nutrient availa
bility acts as a limitation factor on the maximum growth rate which is
itself a function of light and water temperature. Respiration, excret
ion of organic matter, lysis and sinking are the main carbon and nutri
ent loss processes. Results indicate that the model simulates well the
annual phytoplankton dynamics in the central regions of the North Sea
, underestimating primary production and chlorophyll in the southern N
orth Sea. The model gave good correlations with the main dissolved nut
rients, such as silicate, phosphate or nitrate. The primary production
module proved to be especially sensitive to the flagellate/diatom int
eraction and competitive behaviour for inorganic nutrients as well as
with regard to grazing losses. It is suggested that a major improvemen
t could be made by including a third phytoplankton group (e.g., Phaeoc
ystis) in the model structure, and that comparison with other phytopla
nkton growth schemes based on the Droop formulation is advisable.