Sponges are among the oldest animal groups on Earth. Their ecological role is profound, but their welfare status is almost never discussed. Ocean acidification and trawling threaten sponge-dominated ecosystems.
Sponges almost certainly lack any morally relevant welfare capacity given their absence of a nervous system. Their importance in this context is ecological: the destruction of sponge gardens by bottom trawling eliminates habitat used by fish, crustaceans, and echinoderms that do have welfare-relevant experiences. Protecting sponge gardens is therefore a welfare intervention for the sentient animals that depend on them, even if sponges themselves are not moral patients. Deep-sea sponge garden protection is among the most urgent marine conservation priorities.