on land, we use net primary production as  an indicator for biodiversity, so basically, the richness of all biomass on land, but  the ocean is also a control variable. a massive food web of net primary  production from phytoplankton to the, you know, the big sharks and whales.  And, we, we, need to be able to, represent scientifically what are the,  minimum levels of keeping intact food webs in the ocean to keep the ocean functioning.  Oxygen levels, as you mentioned as well,