IV-353 



more wastes (Figure IV. 5. 3). Severely depressed dissolved oxygen 

 levels, which result from an excess of oxygen-consuming organic 

 wastes, affect many categories of beneficial uses. With aquatic 

 habitat damage, pollution-tolerant plants and animals replace the more 

 sensitive types. Desirable game and food fish may be completely 

 eliminated; areas of low dissolved oxygen may block the passage of 

 anadromous fish, thereby affecting the reproduction cycle. If 

 oxygen is totally depleted, noxious odors may develop, completely 

 eliminating such uses as boating, swimming, and esthetic appreciation. 



The level of dissolved oxygen in the water is one direct index of the 

 healthiness of the system. High levels generally indicate a healthy 

 system which will support a diverse biota and multiple use. The 

 lower the concentration of dissolved oxygen becomes, the sicker the 

 system is, and the less desirable it is for habitat or use. 



FLESH-TAINTING SUBSTANCES 



Another class of materials, primarily organic, which can have con- 

 siderable impact on the estuarine ecosystem, are the flesh-tainting 

 substances. Generally these materials are contained in industrial 

 waste effluents and they result in offensive tastes, odors and colors 

 of fish and shellfish. The most common culprits are the oils or 

 petroleum products. These materials in slight amounts will impart 

 an oil or kerosene flavor to a wide variety of fish and shellfish, 



