Foreword
While ecology is one of the scientific disiplines that most clearly belongs to
''basic research", it also strives to serve as a predictive tool for management.
Outstanding examples of predictive ecology are Vollenweider's models on the
relationship between phosphorus load and water renewal time of lakes, and
the resulting algal biomass. The needed few and easily accessible input
parameters to very simple models provided a direct link from basic ecology
to management, and today these models are key tools for managers
worldwide to control lake eutrophication and algal blooms.
The baseline of this success is the general relation between phosphorus
concentration and phytoplankton biomass that is observed for most lakes.
While these relationships are most frequently presented in log-log diagrams,
the aquatic ecologist who replots these a linear scale may ask himself why, in
spite of the overall correlation, there is still such a variability. It is possible to
predict levels of algal biomass that may be synthesized at a given phosphorus
load. Some lakes apparently offer optimal conditions for their phytoplankton
communities, while others may support less than half the biomass at the
same phosphorus load. There are limits to growth, however, and the predictive outcome of phosphorus load decreases as the load increases. This holds
in particular for the higher trophic levels like zooplankton and fish. With
increased enrichment there are signs of decreased efficiency of energy transfer between foodweb compartments. Moreover, system stability tends to
decrease with increased load, and beyond some undefined, probably highly
site-specific limits, further enrichment may cause decreased productivity at
higher trophic levels. This "paradox of enrichment", as Rosenzweig (1971)
labelled it, is a central theme of this book. To resolve these matters, we need
to go beyond large-scale predictive models, and examine in more detail
foodweb dynamics and its relationship to nutrient cycling and ecosystem
stability. First of all, we need to know some of the basic, ecological features of
the organisms in question. Predictive modelling without reliable inputs
would be like constructing a city plan without knowing the basic demands of
the people.
Daphnia is the highly appreciated key component in freshwater ecosystems. This tiny crustacean water flea is instrumental for grazing, nutrient
recycling and transfer of energy to higher trophic levels. It is the obvious
While ecology is one of the scientific disiplines that most clearly belongs to
''basic research", it also strives to serve as a predictive tool for management.
Outstanding examples of predictive ecology are Vollenweider's models on the
relationship between phosphorus load and water renewal time of lakes, and
the resulting algal biomass. The needed few and easily accessible input
parameters to very simple models provided a direct link from basic ecology
to management, and today these models are key tools for managers
worldwide to control lake eutrophication and algal blooms.
The baseline of this success is the general relation between phosphorus
concentration and phytoplankton biomass that is observed for most lakes.
While these relationships are most frequently presented in log-log diagrams,
the aquatic ecologist who replots these a linear scale may ask himself why, in
spite of the overall correlation, there is still such a variability. It is possible to
predict levels of algal biomass that may be synthesized at a given phosphorus
load. Some lakes apparently offer optimal conditions for their phytoplankton
communities, while others may support less than half the biomass at the
same phosphorus load. There are limits to growth, however, and the predictive outcome of phosphorus load decreases as the load increases. This holds
in particular for the higher trophic levels like zooplankton and fish. With
increased enrichment there are signs of decreased efficiency of energy transfer between foodweb compartments. Moreover, system stability tends to
decrease with increased load, and beyond some undefined, probably highly
site-specific limits, further enrichment may cause decreased productivity at
higher trophic levels. This "paradox of enrichment", as Rosenzweig (1971)
labelled it, is a central theme of this book. To resolve these matters, we need
to go beyond large-scale predictive models, and examine in more detail
foodweb dynamics and its relationship to nutrient cycling and ecosystem
stability. First of all, we need to know some of the basic, ecological features of
the organisms in question. Predictive modelling without reliable inputs
would be like constructing a city plan without knowing the basic demands of
the people.
Daphnia is the highly appreciated key component in freshwater ecosystems. This tiny crustacean water flea is instrumental for grazing, nutrient
recycling and transfer of energy to higher trophic levels. It is the obvious