The effects of the water soluble fractions of No. 2 fuel oil on the survival and behavior of coastal and oceanic zooplankton.

Acute effects of water-soluble fractions (WSF) of No. 2 Fuel oil on both coastal and oceanic zooplankton were studied and their LC50 for various exposure times (1 to 72h) compared. Coastal zooplankton seemed to be more resistant to the WSF than oceanic zooplankton. This difference was probable caused mainly by the dissimilar species composition of the two zooplankton populations under investigation. The evidence from this study indicates that, on a species or taxon basis, there are some species in coastal waters more vunerable to oils than among oceanic zooplankton and it is stronglyrecommended that further studies of the tolerance of both populations to various petroleum hydrocarbons be carried out at the same time. A vital staining method was used to distinguish the dead from the immobile forms. Expected variations both in the curves of mortality compared with concentration of oil are explained and a possible method to decrease variblility is suggested.