How much phytoplankton is needed for one dolphin weighing 400 kg to exist normally in the Black Sea?

1) compose a food chain: phytoplankton -> zooplankton – “non-predatory fish -> predatory fish -> dolphin;
2) using the rule of the ecological pyramid (when moving from one link in the food chain to another, energy losses are 90% and only 10% of the energy is stored by the body), we calculate the biomass of the links in the food chain;
3) phytoplankton need 4,000,000 kg.