al , ▁and ▁settlement . ▁Mort ality ▁depends ▁on ▁many ▁factors , ▁such ▁as ▁pred ation , ▁competition , ▁disease , ▁par as ites , ▁and ▁phys i ological ▁str esses . ▁Sur v ival ▁and ▁mort ality ▁of ▁mer op l ank ton ▁has ▁a ▁direct ▁effect ▁on ▁adult ▁population ▁numbers ▁of ▁many ▁species . ▁▁ ▁Many ▁of ▁the ▁common , ▁well - known ▁animals ▁found ▁on ▁the ▁Great ▁Bar rier ▁Re ef ▁spend ▁time ▁as ▁free - sw imming ▁mer op l ank ton , ▁bearing ▁little ▁or ▁no ▁res embl ance ▁to ▁the ▁adult ▁they ▁will ▁become . ▁The ▁differences ▁between ▁the ▁appearance ▁of ▁lar val ▁and ▁adult ▁stages ▁led ▁to ▁much ▁confusion ▁in ▁the ▁past ▁when ▁lar val ▁forms ▁were ▁often ▁believed ▁to ▁be ▁completely ▁different ▁species ▁from ▁the ▁adult s . ▁Lar va e ▁spend ▁varying ▁amounts ▁of ▁time ▁in ▁the ▁pl ank ton , ▁from ▁minutes ▁to ▁over ▁a ▁year . ▁However , ▁just ▁how ▁long ▁these ▁tiny ▁animals ▁can ▁be ▁considered ▁truly ▁pl ank ton ic ▁is ▁under ▁some ▁debate . ▁ ▁Sp atial ▁distribution ▁ ▁Mer op l ank ton ▁species ▁composition ▁depends ▁on ▁spatial ▁distribution ▁and ▁re product ive ▁hab its ▁of ▁adult s ▁in ▁a ▁given ▁area . ▁Bi otic ▁and ▁ab i otic ▁factors ▁such ▁as ▁tid al ▁and ▁lun ar ▁cycles ▁and ▁avail ability ▁of ▁food ▁determine ▁adult ▁sp aw ning ▁sched ules , ▁in ▁turn , ▁ ▁determ ining ▁subsequent ▁mer op l ank ton ▁populations . ▁Be hav iour