lO4
1 , - - - - - - - - - - - - - ,
Ii
Lake Veere
~/\ /.',
j / ~ Y
o L.&;;;;;JL_, ..... i _ .... ~.......l'.- .... ---....:..=-----;...;...~&..;'~_, • .;.;~"1I _ __'
100
Lake Grevelingen
Venice Lagoon
200
days
300
400
macrophytes
phytoplankton (chlorophyll)
1. De Vries et al.
Fig.3.13. Biomass development of phytoplankton and macrophytes in three
lagoons. Units are relative, normalized
between 0-1; absolute levels are indicated
in Figs. 3.6, 3.9 and 3.11. Data for Lake
Grevelingen and Lake Veere derived from
Nienhuis (1992); data for Venice Lagoon
derived from Sfriso et al. (1988)
spring bloom of phytoplankton. Macroalgae only occur when the
nutrients, transferred to detritus by phytoplankton production and
mortality, are regenerated again. The new production in Lake Veere
consists of phytoplankton, whereas there is only regenerated production
of macroalgae. The macro algal biomass persists during the rest of the
year until it dies off at the end of autumn due to unfavourable
environmental conditions.
The climatic conditions in the Venice Lagoon allow a certain amount
of macro algae to survive the winter period, and this amount is probably
variable from one year to another. The initial biomass is, at least is some