This is a symbiotic relationship between the Boxer crab and sea anemone.
<h3><u>Explanation</u>:</h3>
The symbiosis is a type of relationship between two species which has benifit for both the participating organisms.
Here in case of boxer crab, the crab gets the help from the sea anemone in the form of protection. The sea anemone chases the predators and thereby saves the organism from being hunted.
On the other hand, the sea anemone gets food from the crab's prey which he hunts.
So there's a benifit for both.
We can rule out small fish and grasses. My guess is that zooplankton get their energy from phytoplankton, because phytoplankton use photosynthesis to get their energy.
