Abstract:
If prey species exhibit trade-offs in their ability to utilize resources versus their ability
to avoid predation, predators can facilitate prey turnover along gradients of productivity, shifting dominance from edible to inedible prey (the keystone predator effect).
I tested this model under controlled, laboratory conditions, using a model aquatic
system composed of zooplankton as the top consumer, a diverse community of algae
as prey, and nutrients as basal resources. Nutrient manipulations (low and high) were
crossed with presence–absence of zooplankton. Results supported theoretical predictions. Algal biomass increased in response to enrichment regardless of predator
presence/absence. However, predators and nutrients had an interactive effect on algal
biomass and size structure. At the low nutrient level, algal-prey were dominated by
edible forms and attained similar biomass regardless of zooplankton presence/absence