Based on the ecological pyramid rule, determine how much plankton

Based on the ecological pyramid rule, determine how much plankton is needed for one dolphin weighing 400 kg to grow and exist in the Black Sea.

To solve this problem, it is necessary to create a food chain, on the basis of which a solution can be proposed. In the case of drawing up different food chains, the solution will be different.
For example: plankton – herbivorous fish – dolphin.
According to the rule of the ecological pyramid, only 10% of the matter and energy from the previous one goes to each next level (trophic).
Then for the existence of a dolphin weighing 400 kg, you need 400 * 10 = 4000 kg of herbivorous fish, and for their existence 4000 * 10 = 40,000 kg of plankton.
Once again, I draw your attention to the fact that this food chain will require 40,000 kg of plankton.