Zooplankton populations in lake erie and the hudson river have declined by up to 70% since the arrival of zebra mussels because zebra mussels prey exclusively on zooplankton

Zooplankton are the group of smaller animals, which live in the water bodies.

The main source of food of the zooplankton are the phytoplankton.

The zebra mussels are the small freshwater mussels, which feed on the phytoplanktons, they are native to Russia and Ukraine. in the lake of Erie, they are considered to be an invasive species.

The zebra mussels eat up a large amount of phytoplanktons, due to which the food resources for the zooplanktons are declined to a significant level.

Due to the lack of food resources, the number of zooplankton is declined.

Hence, the given blank can be filled with  zebra mussels eat the phytoplanktons, which are food resource for the zooplanktons.

halogen, any of the six nonmetallic elements that constitute group 17 (group viia) of the periodic table. the halogen elements are fluorine (f), chlorine (cl), bromine (br), iodine (i), astatine (at), and tennessine (ts).