In the Southern Ocean , one species , the Antarctic krill , Euphausia superba , makes up an estimated biomass of around 379,000,000 tonnes , more than that of humans .
In the Southern Ocean , one species , the Antarctic krill , Euphausia superba , makes up an estimated biomass of over 500,000,000 tonnes ( 490,000,000 long tons ; 550,000,000 short tons ) , roughly twice that of the human race .