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 
applicable to Fucus and Laminaria (Pulich used doubling times and Eisler used 
LC 50 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 life cycle, the community structure of algae, 
as well 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 Toxicides of Crude Oils and Oil-Dispersant Mixtures 
to Red Sea Fishes and Invertebrates. Israel Journ. of Zool. 24:16. 
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