Answer:
Zebra mussels feed on phytoplankton, which zooplankton need as a food source.
Step-by-step explanation:
The population of zooplankton in Lake Erie and the Hudson River declined due to the arrival of zebra mussels because Zebra mussels feed on phytoplankton, which is the main source food of zooplankton. So due to limited or scarcity of food in the environment, the zooplankton die due to hunger that leads to the decrease of population of zooplankton in that environment.