244
Y Stability PropertIes In the Wauucil Sea
the particular enzymes needed for the decomposition of particular organic matter
very quickly, either by population growth of certain species, or by changes in
metabolic pathways.
In this context much has been written in the ecological literature about possible
relationships between (species) diversity and "stability". In most cases this relationship is not clear because the terms used are not unequivocal (Pimm 1984).
However, with respect to the performance of bacteria in the Wadden Sea we can
conclude that the stability properties persistence and resilience rely on the high
functional diversity of the bacteria (cf. Reise et al. 1998).
One necessary requirement for the functional diversity of bacteria to become effective is a close coupling between the compartment where remineralization takes
place and the entire system. This close coupling is ensured in the Wadden Sea by a
water body which is dynamic because of tides and swell. Tides and swell lead to
turbation on the surface of the sediment, which enables an effective exchange of
material between sediment and water. The effects of turbation are enhanced by the
effects of bioturbation caused by the infauna.
Extreme scenarios
Without bacteria, the high rate of primary production in the Wadden Sea would be
impossible because all the nutrients available would have been consumed very
quickly. Hence, all consumers, including fish, birds and seals would disappear
from the Wadden Sea. But such a scenario, i.e. a Wadden Sea without bacteria, is
extremely unlikely because of the high physiological flexibility and functional
diversity of bacteria. Extreme scenarios regarding bacteria would thus not be scenarios without bacteria, but scenarios in which bacteria exist to the virtual exclusion of any higher organisms. Such a scenario would occur after long-lasting periods of anoxic condition on the surface of the sediment; but this, as has been
pointed out above, is very unlikely because of the turbation caused by tides, swell
and storms (see above, 9.4.3).
9.5.2 Microphytobenthos and Phytoplankton
Variables of interest
As with bacteria, it is the overall physiological performance of microalgae that
matters with respect to the entire Wadden Sea, i.e. primary production. As far as
benthic algae are concerned, spatial distribution is another important variable of
interest. This distribution may be patchy because of local heterogeneities or smallscale disturbances. With phytoplankton, the body size of the different species is a
relevant variable because the consumer of the planktonic algae may prefer particular size classes (Chap. 5.1). Species composition is thus a relevant variable of
phytoplankton, which becomes even more relevant after rare extreme events (e.g.,
ice winter), when species which are not typical for the Wadden Sea become dominant for some time (Chaps. 5.1 and 7).
Y Stability PropertIes In the Wauucil Sea
the particular enzymes needed for the decomposition of particular organic matter
very quickly, either by population growth of certain species, or by changes in
metabolic pathways.
In this context much has been written in the ecological literature about possible
relationships between (species) diversity and "stability". In most cases this relationship is not clear because the terms used are not unequivocal (Pimm 1984).
However, with respect to the performance of bacteria in the Wadden Sea we can
conclude that the stability properties persistence and resilience rely on the high
functional diversity of the bacteria (cf. Reise et al. 1998).
One necessary requirement for the functional diversity of bacteria to become effective is a close coupling between the compartment where remineralization takes
place and the entire system. This close coupling is ensured in the Wadden Sea by a
water body which is dynamic because of tides and swell. Tides and swell lead to
turbation on the surface of the sediment, which enables an effective exchange of
material between sediment and water. The effects of turbation are enhanced by the
effects of bioturbation caused by the infauna.
Extreme scenarios
Without bacteria, the high rate of primary production in the Wadden Sea would be
impossible because all the nutrients available would have been consumed very
quickly. Hence, all consumers, including fish, birds and seals would disappear
from the Wadden Sea. But such a scenario, i.e. a Wadden Sea without bacteria, is
extremely unlikely because of the high physiological flexibility and functional
diversity of bacteria. Extreme scenarios regarding bacteria would thus not be scenarios without bacteria, but scenarios in which bacteria exist to the virtual exclusion of any higher organisms. Such a scenario would occur after long-lasting periods of anoxic condition on the surface of the sediment; but this, as has been
pointed out above, is very unlikely because of the turbation caused by tides, swell
and storms (see above, 9.4.3).
9.5.2 Microphytobenthos and Phytoplankton
Variables of interest
As with bacteria, it is the overall physiological performance of microalgae that
matters with respect to the entire Wadden Sea, i.e. primary production. As far as
benthic algae are concerned, spatial distribution is another important variable of
interest. This distribution may be patchy because of local heterogeneities or smallscale disturbances. With phytoplankton, the body size of the different species is a
relevant variable because the consumer of the planktonic algae may prefer particular size classes (Chap. 5.1). Species composition is thus a relevant variable of
phytoplankton, which becomes even more relevant after rare extreme events (e.g.,
ice winter), when species which are not typical for the Wadden Sea become dominant for some time (Chaps. 5.1 and 7).