Nutrient Use and Remineralization - Freshwater Ecology: Concepts and Environmental Applications - page 317

EXAMPLE 16.1.
Uptake and Growth Calculations

Two species of phytoplankton have the following characteristics:

K s V max

(mg liter 1 ) g liter 1 h 1 ) max (day 1 ) Phytoplankton species ( Q 0 (g/g)

Anabaena 0.5 3 0.5 0.05

Scenedesmus 0.1 1 0.1 0.01

Problem 1: Which species will be the best competitor for nutrients (i.e.,
have the highest nutrient uptake rates) when nutrient concentrations are
0.01 and 0.5 mg liter 1 ?

The Michealis-Menten equation yields the following results:

0.01 mg liter 1 ) 0.5 mg liter 1 )

Phytoplankton species V (at S V (at S

Anabaena 0.059 1.5

Scenedesmus 0.091 0.83

The Anabaena will have a competitive advantage at the higher nutri-
ent concentration. The Scenedesmus will have the advantage at the lower
nutrient concentration. The curves for this and the following two problems
are presented in Fig. 16.3.

Problem 2: Which species will have the highest growth rate at [S] 0.01

and 0.5 mg liter 1 ?

0.01 mg liter 1 ) 0.5 mg liter 1 ) Phytoplankton species (at S (at S

Anabaena 0.0098 0.250

Scenedesmus 0.0091 0.0833

The Scenedesmus has the disadvantage in growth at both substrate
concentrations.

Problem 3: Which species will have the highest growth at a Q of 0.06 and
0.1 g/g?

Phytoplankton species (at Q 0.06 g/g) (at Q 0.1 g/g)

Anabaena 0.0 0.25

Scenedesmus 0.08 0.09

The Scenedesmus will have a competitive advantage at the lower cell
quota because the Anabaena cannot grow. The Anabaena will have the ad-
vantage at the higher cell quota.