In a lake with three trophic levels (non-native fish, zooplankton, algae), an algal bloom occurs when the small population of zooplankton declines due to the predation of the invasive fish. Which of the following describes why zooplankton are the keystone species in this scenario? a) Zooplankton are the smallest of all the herbivorous marine mammals in their communities.
b) The small population of zooplankton have an unequal effect on the marine community.
c) Marine mammals depend upon the work of zooplankton to convert sunlight into food.
d) Zooplankton help other populations survive by keeping out other herbivores.