that this practice is, indeed, rather common in the Gulf. GC analysis 

 of one of these gas emissions (flares) gave a complex spectrum which 

 indicated carbon numbers up to at least Cio and included some aro- 

 matic components. 



On the basis of this 5 year study in the Gulf of Mexico it appears 

 that most instances of high levels of low-molecular-weight hydro- 

 carbons in the vicinity of offshore oil production activities are due to 

 this practice of underwater discharging waste hydrocarbon gases. 



Heavy Petroleum Hydrocarbons 



The group at the University of Texas Marine Science Institute find 

 that sea water when equilibrated with a sample of #2 fuel oil (API) 

 becomes toxic in varying degrees to growth of representative types of 

 microalgae including two blue-greens, a diatom, two greens, and a 

 dinoflagellate (Pulich, Winters & Van Baalen. 1974) . 



A standard petroleum containing seawater was prepared by equili- 

 bration of 1 part oil with 8 parts of sea water for 24 hours with gentle 

 mixing by a magnetic stirring bar. After equilibration the water was 

 drained by means of a stopcock at the base of the bottle. This stock 

 of oil-treated seawater contained 10-20 ppm of total hydrocarbon de- 

 pending on the oil used. The oil-treated stock seawater was diluted 

 to obtain serial concentrations. 



For a sensitive organism such as Thalassiosira pseudonana, strain 

 3H, 5 ml of stock sea water (equilibrated with fuel oil so as to contain 

 15 mg/1 of hydrocarbon) in 20 ml of growth medium is lethal. If, as 

 seems reasonable, the toxic component of the oil is 1-10% of the total 

 dissolved hydrocarbon then 40-400 ppb is toxic. This fuel oil-equili- 

 brated seawater also inhibits photosynthesis in organism 3H. For other 

 microalgae tested (e.g. 580 and PR-6), similar effects on growth and 

 photosynthesis were found but required higher concentrations of the 

 oil-equilibrated sea water. Figure 2 shows a typical series of experi- 

 ments and Table 2 is a summary of work using API #2 fuel oil. 



Water solubles from Kuwait or Southern Louisiana crudes (when 

 the straight crude was equilibrated 1 : 8 with seawater) were not toxic, 

 however specific fractions made by distillation did show some water 

 soluble toxicity. Growth experiments in open (continuously bubbled) 

 or sealed growth systems showed that most organisms were inhibited 

 by varying amounts of these two crude oils when in direct contact 

 with them. Organism 580 would not grow above 5 ul of Southern 

 Louisiana/25 ml of medium, or 10 ul of Kuwait/25 ml of medium 

 (oil in direct contact with algae) . 



15 



