High concentrations of toxic heavy metals in estuaries are most likely found in the select one:

a. water of the estuary

b. air above the estuary

c. estuary sediments

d. water of the adjacent ocean

e. air above adjacent land

The correct answer is c. estuary sediments.

Estuaries are under threat from human activities and they concentrate materials such as pollutants and sediments. For example, estuaries receive a high heavy-metal input from industries. Those heavy metals are most often found in the estuarine organisms and in sediments.