Question

When water used to cool machinery is returned to a river, it raises the river water temperature. this causes a sharp decline in small invertebrate populations. based on the food web, a likely consequence of this change would be?

Answer 1

Out of the following given choices;

(1) an increase in the number of clams                    

(2) a decrease in the number of water plants               

(3) an increase in the number of crabs

(4) a decrease in the number of crayfish

The answer is D. Crayfish are are freshwater crustaceans resembling small lobsters. Clams and crabs are found in marine waters. Most crayfish cannot tolerate polluted water. Crayfish feed on animals and plants, either living or decomposing, and detritus, therefore a decrease in small invertebrates in the river would decrease their food source thence consequently affect their numbers.