Effects of Changing Environmental Conditions on Lagoon Ecology - Coastal Lagoons: Ecosystem Processes and Modeling for Sustainable Use and Development - page 199

Nutrient concentration

FIGURE 5.3 Relation between phytoplankton growth rate and nutrient concentration.

Phytoplankton takes up nutrients from the water following the Michaelis-Menten kinetics
(V = V

max S/( K s + S)). Different lines show kinetics with different K s and V max .

where Q is the nutrient content per cell ( Q = uptake rate/cell division rate) and Q

o

is the minimal nutrient content allowing cell division. Growth rate is thus dependent
on cell nutrient content which, at the same time, depends on the adaptation of cells
to nutrient concentration in water (Figure 5.4).
Implications for the luxury uptake of nutrients by phytoplankton are relevant in
nutrient-limited water, as nutrients are not homogeneously distributed in the water
column. Zooplankton, or excretion of other organisms, creates small patches of
recycled nutrients that phytoplankton can go through, taking up and storing them,

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thus providing the chance to grow even at very low nutrient concentration in the
water.

Nutrient content per cell

FIGURE 5.4 Luxury uptake: Growth rate is dependent on cell nutrient content which, at
the same time, depends on the adaptation of cells to nutrient concentration in water.