The diversity, abundance and productivity of the main trophic groups are maintained so that the sustainability of the trophic chains is ensured, and of existing predator-prey relationships. The natural bottom-up and top-down control processes operate efficiently by regulating the transfer of energy from marine communities. The populations of the species selected as predators at the top of the trophic chain are maintained in values that ensure their maintenance in the ecosystem and existing predator-prey relationships. Eutrophication, selective extraction, or other effects deriving from human activities, occur at levels that do not put at risk the maintenance of existing trophic relationships.