A1.05 Same Results of Test Board Research 



1. Prevalence and DestructlvenesB . Accumulating test "board data 

 on meirine torer infestation at many hartors form the tasis for the 

 following deductions regarding the effects of local conditions, the 

 inhihiting effects of industrial pollution, and the favorahle conditions 

 found to exist in northern hartors. 



a. Effects of Local Conditions . In a given area, various 

 local conditions "besides temperature of the water may strongly affect 

 the prevalence and destructive activities of horers. The individual 

 effects of currents, degree of salinity, depth of the suhmerged 

 structure, pollution (see the following peuragraph), and other 

 factors cannot "be determined at present. However, it is laiown that if 

 certain species of horers are introduced into areas where they did not 

 previously exist, and conditions prove favorahle, lie horers will thrive, 

 multiply, and cause serious damage. 



t.^ Inhihiting Effects of Pollution . It has heen ohserved 

 that heavy pollution seems to prevent, or at least to minimize, the 

 activities of marine "borers. For example, after the removal of sewage 

 from an area previously immune to Teredo attack, a heavy onslaught of 

 the "borers was o^bserved. On the other hand, numerous sewer outlets 

 made of wood have "been totally destroyed "by Teredo. As a general riile 

 the factors unfavora'ble for "borers axlse from Industrial wastes — acids 

 and oils — rather than from domestic sewage. 



c. Favora'ble Conditions in the Arctic . As noted in 

 paragraph Al.Ol, "bprer damage in northern har"bors in Alaslia, Newfoundland, 

 and Nova Scotia may "be as rapid and severe as in southern waters. In 

 general, low temperature of the water greatly reduces the rate of 

 destruction "by Teredinidae , hut this is not true of Limnoria . The latter 

 is almost always present in the waters of many northern har"bors, as, for 

 example, at Kodiak, Alaska, where it was very active during the initial 

 three months of a recent survey and "became even more active later. 

 Again, a trace of Limnoria was found in test. "blocks at Adak, Alaska, 

 in each of four monthly examinations during' the first part of 19^8. 



2. Reports on Treated and Untreated Wood . The o"bserved results 

 of using treated and untreated wood are summarized in a., "b., and c. 

 "below for Sitka, Alaska, and Bremerton, "Vfashington. A method for 

 successfully repelling "borer attacks on hoat hulls is outlined in 

 paragraph d. 



a. Summer- cut Sitka Spruce (with "bark removed) was reported 

 to "be completely destroyed "by Teredo action at Sitka, Alaska. However, 

 the piling of the New Navy Dock at this location, which had "been treated 



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