at atmospheric pressure. The effects of 30 to 40 atmo- 

 spheres of pressure upon the rate of carbon monoxide pro- 

 duction by a pneumatophore possessing sufficient substrate 

 remains a matter of conjecture. Future studies of these 

 important and interesting organisms might well include this 

 aspect of their physiological capabilities. 



SUMMARY 



The major findings to date relevant to the effects of 

 siphonophores on sound propagation in the sea may be sum- 

 marized as follows: 



1. Volume of gases contained in siphonophore floats 



can most accurately be calculated from dimensional measure- 

 ments treating the bubble as a prolate spheroid. 



2. Sizes of floats vary,, probably depending upon age of 

 the colony; their gas volumes, determined by extrusion, 

 range from approximately 0. 5 to approximately 2. 5 mm as 

 measured at atmospheric pressure. 



3. Adjustment of gas pressures within the siphonophore 

 float closely follows the ambient pressure, suggesting that 

 release of numerous bubbles takes place during a vertical 

 migration. It is very likely that some of these released 

 bubbles will pass through a size where they will briefly 

 resonate if insonified by a particular sound frequency. 



4. Measured rate of gas production by a siphonophore 

 float was too slow to account for observations made by others 

 of rapid filling of the float. This is probably a function of 

 float condition and available substrate for gas production, 

 but may be affected by other variables as well. 



5. Measured rate of gas production in one instance was 

 rapid enough to balance total diffusive loss of CO by the 

 float, suggesting that normal floats probably sustain gas 

 secretion at some minimum maintenance level. 



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