Explain how the carbon cycle
might be affected if
phytoplankton population were to decrease.

So basically when Phytoplankton dies it sinks to the ocean floor and takes the carbon in it's body with it.

a physical change is being made.

kelp are large brown algae that live in cool, relatively shallow waters close to the shore. they grow in dense groupings much like a forest on land. these underwater towers of kelp provide food and shelter for thousands of fish, invertebrates, and marine mammal species.

e) all of the above