Table 1 



Effects of Liquid Aliphatic and Aromatic Hydrocarbons on the 

 Photosynthetic Rate of Phytoplankton. 



Benzene Mixed ocean culture 

 Benzene Mixed ocean culture 

 Benzene Mixed ocean culture 

 Toluene Mixed ocean culture 

 Xylene Mixed ocean culture 

 Pentane Mixed ocean culture 

 Hexane Mixed ocean culture 

 Heptane Mixed ocean culture 

 Octane Mixed ocean culture 

 Benzene Skeletonema costatum 

 Benzene Skeletonema costatum 

 Benzene Skeletonema costatum 

 Toluene Skeletonema costatum 

 Hexane Skeletonema costatum 

 Octane Skeletonema costatum 

 Decane Skeletonema costatum 



dicate that the most important sources of Ci through C5 hydrocarbons 

 are related to man's activities. These sources include ports and estu- 

 aries with their associated shipping and petrochemical activities, off- 

 shore drilling and production platforms, and ships which discharge 

 oily ballast water and/or clean their fuel tanks at sea. The water col- 

 umn several miles distant from at least one example of each of the 

 three types of sources showed several orders of magnitude higher con- 

 centrations than observed for the open Gulf. 



On a March 1974 cruise, the Texas A&M group surveyed the water 

 in and around several groups of platforms offshore Louisiana. The 

 groups farthest out, presumably the newest, showed C1-C5 dissolved 

 hydrocarbon concentrations in nearby waters generally two to three 

 orders of magnitude higher than concentrations in surface water of 

 the open Gulf of Mexico, where the latter are equilibrium concentra- 

 tions determined by the partial pressures of the various gases in the 

 atmosphere. Surface water around platforms nearer to the coast, pre- 

 sumably in place for a longer period of time than the platforms cited 

 above, had much lower levels but still one to two orders of magnitude 

 higher than open Gulf surface water. 



13 



