Industrial waste 



The most common industrial pollutants entering 

 oyster-producing areas stem primarily from the 

 following industries: oil; paper; steel; chemicals; 

 paints; plastics; leather; and food. The character 

 of industrial waste varies with the product. 



Because of the increase in the number of oil 

 burning ships and the necessity of transporting 

 crude oil in huge tankers that occasionally break 

 and spill their cargo, oil pollution of the open sea 

 has become a difficult international problem. 

 Although federal and state laws forbid the dis- 

 charge of oil into coastal waters, many of the bays 

 and harbors of the United States are heavily 

 polluted by oil. Through surface tension oil 

 spilled on the surface of water spreads rapidly 

 into a thin film or oil slick. In muddy waters 

 suspended particles of clay and sand absorb oil, 

 coalesce, and gradually sink to the bottom. In 

 shallow waters oil laden sediment is disturbed by 

 waves, and an oil slick reappears on the surface, 

 sometimes considerable distances from the source 

 of pollution. The absence of an oil slick is not, 

 therefore, a reliable sign that water is not polluted. 

 Crude oil absorbed by sediments retains its toxicity 

 to oysters and other organisms for a considerable 

 time (Chipman and GaltsofT, 1949). 



With the expansion of the pulp and paper 

 industry along the Atlantic and Pacific Coasts, 

 pollution of coastal waters by red and black 

 liquors, the waste products of this industiy, 

 became serious. Both types of waste contain 

 toxic substances which adversely affect oyster 

 physiology. As in other types of pollution, the 

 discarded material is usually oxidizable and has 

 high oxygen demand. It is, however, only in 

 extreme instances of gross pollution that the 

 oxygen content of the water is lowered to the 

 point that it suppresses the principal physiological 

 functions. Poisons, present in trade waste, are 

 more dangerous than the high oxygen demand 

 because they directly affect the function of the 

 various organs. In spite of great variety in the 

 composition of trade wastes their toxic effect can 

 be demonstrated by constructing a toxicity curve 

 which shows how the pollutant depresses the 

 function that was selected for testing. An oyster 

 heart preparation (see ch. XI, p. 247) can be used 

 conveniently because of the great sensitivity of 

 the heart muscle to many poisons and drugs. 

 Another measurable function is the transport of 

 water by the gills for feeding, respiration, and 



discharge of excreta. This function ceases when 

 the valves are closed. The presence of pulp mill 

 pollutants reduces the number of hours the valves 

 are open in proportion to the concentration of 

 toxic substances in the water. Under normal 

 conditions and at temperatures of 60° to 70° F. 

 oysters remam open on an average of 20 to 22 

 hours a day. If the logarithm of concentration of 

 black liquor or crude oil extract is plotted against 

 the number of hours closed, the relationship can 

 be expressed by a straight line as shown in fig. 399. 

 Toxic substances of pulp mill effluents and the 

 extracts of crude oil affect the frequency of ciliary 

 beat and so interfere with the coordination of 

 ciliary motion with the result that the pumping 

 capacity of the gills is reduced. The reduction is 

 proportional to the concentration of physiologi- 

 cally active materials Cfig. 400). This type of 

 relationship was found in studies on the pollution 

 of oysters by red and black liquor and by water 

 soluble components of crude oil (Galtsoff, 1931b; 

 Galtsoff, Chipman, Engle, and Calderwood, 1947; 

 Chipman and Galtsoff, 1949). The observations 

 on crude oil are in agreement with data reported 



< 



UJ 



u 



z 

 o 



O 



0.5 



5 10 15 



HOURS CLOSED 



Figure 399. — Effect of concentration of pulp mill effluent 

 discharged into the York River on the number of hours 

 oj-sters are closed during every 24-hour period. From 

 Galtsoff, Chipman, Engle, and Calderwood, 1947. 



FACTORS .\FFECTING OYSTER POPULATIONS 



443 



