The Oder Estuary - IOW

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describes the assimilation number which is the maximum photosynthetic rate that occurs at
optimum irradiance without influence of any other limiting factors. Maximum growth at 20 o C
equals:
µmax =1.8 per day at 20 o C
The seasonal change of the assimilation number is related to the changing temperature. That
relationship is described in the model based on experimental findings by EPPLY (1972) and
GOLDMAN & CARPENTER (1979):
f(Temp) = temp_coeff_phyt (Temp-20) temp_coeff_phyt = 1.08
For 1.08 as the value of the temperature coefficient, the Q10 value - defining an increase in
phytoplankton growth rate for an increase in temperature by 10 o C - equals 2.15 and can be
compared to the Q10 = 1.88 given by EPPLY (1972) and Q10 = 2.19 given by GOLDMAN &
CARPENTER (1979) for marine species - and Q10 = 2.08 for fresh water species.
2.3.3 Nutrient uptake by phytoplankton
The assimilation of nutrients follows Michaelis-Menten kinetics. The range of values given for half
saturation constant for nutrient uptake in literature is very wide. Values applied in the model are
within the range given by JORGENSEN (1994).
f
f
( DIN)
( PO4)
DIN
= kN = 5 mmol m
kN + DIN
3
PO4
= kP = 0.3 mmol m
kP + PO4
3
2.3.4 Light dependency of the phytoplankton growth
Light (PAR) dependency of the phytoplankton growth is described by the STEELE equation (1962):
f
PAR
Iopt
PAR
1−
Iopt
( PAR ) = × e
Iopt = for PAR >50 W m -2 equals 0.8 * PAR
for PAR ≤50 W m -2 equals 20 W m -2