ABSTRACT 



This report describes a marine biological fouling program conducted 

 near Thimble Shoal Channel in lower Chesapeake Bay. The results 

 of 12 months' (April 1956 to April 1957) fouling data on mine case 

 test panels are presented. 



Observations of water temperature, salinity, currents, transparency, 

 and underwater visibility were taken in conjunction with the monthly 

 observations of the fouling complex. Additional data from tide stations 

 for past years were analyzed to determine whether the environmental 

 factors for 1956-57 were within the range of averages. Apparently this 

 was not an unusual year. Therefore, the results of this study are 

 considered reliable. 



Fouling organisms began to attach in May and reached peak attach- 

 ment in August. In general, attachment was limited to periods when 

 the water temperature was above 65°F. Growth of the organisms, 

 following the period of peak attachment, continued at a rapid rate from 

 August to October. Attachment of fouling organisms from October 

 through April was practically nil. However, growth continued from 

 October through April, but at a reduced rate. 



Test panels accumulated a total of 31 ounces of growth (wet weight 

 in air) per square foot per year. The predominant fouling organisms 

 were barnacles, calcareous tubeworms, hydroids, bryozoans, jingle 

 shells, and tunicates. Attachment periods and growth of each of these 

 organisms are described in detail, and the possibility of using this 

 information to determine the length of time an object has been sub- 

 merged is discussed. The results thus obtained will be verified or 

 modified as additional information is obtained from the second 12 

 months' data at the same location. 



ACKNOWLEDGMENT 



Acknowledgment is made of the efforts of the Harbor Defense 

 Unit, Norfolk in providing the necessary services and facilities 

 which made possible the collection of the data reported herein. In 

 addition to performing its primary function, the Harbor Defense 

 Unit, Norfolk has demonstrated its value as a "Pilot Unit" for making 

 an operational evaluation of marine biological fouling to promote 

 better understanding of military oceanography and improve harbor 

 defense procedures. 



