This halocline between the seawater above and the brine below has many bacterial and archaeal cells : they are chemoautotrophs , which feed on ammonia from the brine but can not function without some oxygen . The approximately 1.5 m halocline between the seawater above and brine below teems with bacterial and archaeal cells : they are chemoautotrophs , which feed on ammonia from the brine but can not function without some oxygen .