Why is it important to save killer whales?

Killer whales can be useful in many ways to protect the ecosystem. They can naturally manage fish population naturally instead of relying on trawlers catching them which not only disturbs other wild life as bycatch but causes pollution. Another way is that similar to actual whales, their poo can help by enabling plants to photosynthesis the carbon and produce oxygen which can increase the oxygen levels in water if their was a sustainable population of orcas.