Environmental Engineering Reference
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Carnivore 2
limited by
Carnivore 1
availability
Carnivore 1
limited by
Herbivore
availability
Herbivore
limited by
primary
productivity
Primary
Producer
limited by
resources
Fig. 18.1 Pure bottom-up control in a four level food chain. Due to the limitations, for every level
strong competition effects apply
hierarchical levels with the concept of bottom-up control, but also the impacts of
nutrients, physical factors (e.g. temperature) and chemical factors (e.g. water pH,
dissolved oxygen). Other major physio-chemical factors that affect lake productivity
are light, water-turnover time and vertical mixing. However, it has been found in
recent years that even when all of these physical factors are taken into account, they
can only explain approximately half of the observed variability in primary produc-
tivity and the productivities of higher trophic levels. There is a lot of variation in the
production of comparable trophic levels among lakes that have the same phosphorus
input or nutrient loading. Carpenter et al. (1986) have offered the hypothesis that
much of this variation can be explained by “cascading trophic interactions”. These
are interactions that cascade down food chains, starting from the highest carnivores,
the piscivores. An increase in piscivore biomass causes a decrease in planktivore
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