Food Webs Practice

Sharks are large fish that live in the ocean. Hammerhead sharks are a part of a marine ecosystem, as shown in the food web. 
This question has three parts.
Cownose rays are an important part of the marine ecosystem.

Identify the ecological relationship (competitive, parasitic, or predatory) between cownose rays and oysters in the ecosystem. Explain your reasoning.

Describe what would most likely happen to the size of the cownose ray population (increase, decrease, or stay the same) if there were a large decrease in the phytoplankton population in the ecosystem. Explain your reasoning.

Based on the food web, describe what would most likely happen to the hammerhead shark population if the cownose rays were removed from the ecosystem. Explain your reasoning.