INTRODUCTION 



Oceanographic instruments, ships' hulls, buoys, and other structures 

 submerged in the sea eventually become either heavily fouled with biological 

 growth or severely corroded. A short time after submergence such objects 

 become covered with "primary film." This film is composed of microorga- 

 nisms such as bacteria, yeast, and diatoms. 1 Following the formation of 

 primary film, larger biological organisms such as hydroids, algae, barnacles, 

 tubeworms, mussels, and bryozoans become attached to the surfaces of the 

 materials. Some of the detrimental effects to equipment caused by the 

 fouling of materials are summarized in Table 1 . 



Table 1. Effects of Fouling on Submerged Objects* 



Ship hulls 



Fouling increases resistance to motion, thereby reducing a ship's 

 speed and increasing fuel consumption. Increases frequency of 

 dry-docking periods. 



Underwater sound 

 equipment 



Fouling reduces sensitivity and sound transmission and decreases 

 effectiveness of sound gear by increasing cavitation noise. 

 Measurement of beam pattern and receiving response of fouled 

 underwater transducers show reduction of axial sensitivity 

 ranging from to 10 db in frequency intervals of 1 to 20 kHz. 



Salt water pipe system 

 in vessels, industrial power 

 plants, and desalting 

 plants 



Fouling on pipe inner surfaces reduces pipe diameter and water 

 flow. Detached organisms (mussel shells) block water flow at 

 valves, at screens, and at constricted places in pipes. 



Metallic surfaces 



Pitting occurs under shells of dead barnacles, created by oxygen 

 concentration cells. Conditions favorable to corrosion are pro- 

 duced by metabolic products — particularly acids and sulfides. 

 Sulfate-reducing bacteria promote anaerobic corrosion. 



Protective coatings 



Fouling damages coatings in several ways: when a barnacle 

 shell adhering to the coating is torn loose for any reason, the 

 underlying paint comes off with it; paint film is weakened at 

 the site of attachment due to metabolic products; the sharp 

 edges of barnacle shells cut into the coating as the animals grow, 

 eventually exposing the underlying surface. Paints are also 

 destroyed by seawater bacteria that attack the resin. 



Plastic and glass surfaces 



Windows of underwater structures and camera lenses become 

 blocked and require frequent cleaning. 



* From Reference 2. 



