Effects of Polychlorinated Biphenyls (PCBs) on a Marine Plankton Population and Sedimentation in Controlled Ecosystem Enclosures

Effects of polychlor~nated b~phenyls (PCBs) on a natural rnarlne rcosystem were studied employing controlled ecosystem enclosures (CEEs) which conta~ned 68 m ' of srdwater and the natural sea-water biota (Saan~ch Inlet, Br~tish Co lumb~a , Canada) Follotv~ng a d d ~ t ~ o ~ l of PCBs 150 { r r j I l ) to a CEE, prlmary productivity was initially reduced by PCBs to less than 30 % of the control CEE to which no PCBs had been added. Settling velocity of partlculate m a t t e ~ was ln~tlally accelerated by PCB addition, but gross sedlmenta t~on decreased due to inhib~t ion of prlmary p roduc t l~ t y . Deconlpos~t~on activity in sedlmented matter was ~ n i t ~ a l l y i n h ~ b ~ t e d by PCBs, one order of n iagn~tudc lower than that of the control, but followed by recovery to the control level w l t h ~ n 6-10 d Dras t~c and ch ron~c reduct~ons in the size of zooplankton stocks wele also a t t r~buted to PCB stress