investigators using different techniques and response parameters. Based on the 

 bioassays with Fucus and Laminaria, it appears that they were not as sensitive 

 to oil as some microalgae that have been studied (7), but they were similar or 

 slightly more sensitive than bioassays developed with fish and invertebrates (2, 

 3). Although the toxicity values obtained in these studies were not directly 

 apphcable to Fucus and Laminaria (Pulich used doubling times and Eisler used 

 LC50 values) similar values can be derived. 



The extreme sensitivity of the reproductive stages, i.e., eggs and sperm in 

 Fucus, and spores in Laminaria, indicate that either of these organisms might 

 become a useful bioassay tool. 



In one experiment, Fucus receptacles were allowed to stand in various 

 concentrations of oil 5 hours before being placed in moist chambers overnight. 

 After completing the experiment in the usual manner, and allowing gamete 

 release to occur in sterile seawater, the deleterious effects on the sperm were 

 not observed. However, growth of the juvenile plants was reduced, being 

 similar to that in Table 8-2, even though the zygotes were not in oil solutions 

 during or after fertilizations. Further experiments with two-week old juvenile 

 Fucus plants indicated that as the plant gets older, sensitivity to oils decreases. 

 Thus, the most critical stage of the life cycle, and the one most sensitive to oil, 

 is the reproductive phase. 



Continued development and refinement of these bioassay procedures is 

 needed, as well as a survey of other seaweeds, to see how representative these 

 results are for seaweeds in general. The development of a bioassay in a 

 flow-through system would be more representative of natural conditions. 



The deleterious effects of low-level oil pollution on the reproductive cycle 

 of these algae can easily be visualized, especially in areas of chronic pollution, 

 such as those found near harbors, marinas, and similar installations. By 

 preventing the completion of the Hfe cycle, the community structure of algae, 

 as weU as that of higher trophic levels, will be altered. Greater effort should be 

 made to examine chronic, long-term effects of oil pollution on the marine 

 ecosystem. 



REFERENCES 



1. Dawson, E.Y. 1956. How to Know the Seaweeds. Wm. C. Brown, 

 Publishers, Dubuque, Iowa. 



2. Eisler, R. 1975. Acute Toxicities of Crude Oils and Oil-Dispersant Mixtures 

 to Red Sea Fishes and Invertebrates. Israel Joum. of Zool. 24:16. 



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