What would cause this change in water temperature, and how will this change most likely affect species distribution?

Think of gold fish that you get from the fair.. why cant we put them in water from the drain right away? because it kills them. so the water changing can hurt the species because its a change in habitat 

The answer to this will be from your lab notes/procedure. it would be best to ask another student who participated in the lab as we do not know what was done, what enzyme or if the temperature is celsius or fahrenheit. if i were to guess though i'd say the rate stopped due to enzyme denturing at high temperature