64 



The Substratu7n 



to simpler substances. But when these species attack buildings, tele- 

 graph poles, and railroad ties unchecked, they cause tremendous 

 damage, often within a short time. A knowledge of their ecological 

 relations then becomes a matter of vital economic concern. Wooden 

 structures under water similarly serve as the substratum for other 

 rotting fungi, for the "shipworm" Teredo, and for other forms, which 

 are consequently also of great economic importance. It is a curious 

 fact that, although the shipworms honeycomb a piece of wood, their 

 tubes rarely run into one another and practically never break through 

 the surface of the wood to the exterior. In some way the boring 

 shipworm is able to detect when it is nearing the limit of its substratum 

 and stops itself from running out into the open. 



Woods Hole Oceanographic Institution 



Fig. 3.2. Mussels and other fouling organisms forming a crust 17 to 30 cm thick 



and weighing up to 13 kg per 1000 cm" on the bottom of a bell buoy seen as it is 



being hoisted out of the water off Cape Cod, Massachusetts. 



The hulls of ships and the surfaces of underwater structures present 

 specialized substrata in the marine environment that are used as points 

 of attachment for many kinds of fouling organisms including notably 

 algae, barnacles, mussels, and tubeworms. Even the smooth steel 

 bottoms of modern vessels and navigation buoys are rapidly attacked 

 by such plants and animals (Fig. 3.2). An understanding of the 



