573 



tubing and galvanized water piping in our modem urban dwellings 

 subject to corrosion and leaching, releasing unknown quantities of 

 copper and zinc. 



Oil 



Because of the increase in oil pollution and the associated use of 

 oil dispersants, it is urgent that a better understanding of degradation 

 processes involving both treated and untreated oil spills be reached 

 without delay. The extent and kinds of effects exerted by oil dispersants 

 must be known so that appropriate reactions can be made when an oil- 

 spill-induced emergency occurs. For example, oil or petroleum concen- 

 tratioii, per se, at high levels is considered deleterious to the ecosystem 

 and maximum levels of oil or grease are established for estuaries. How- 

 ever, evidence from both the Torrey Canyon and Santa Barbara oil 

 spills indicate that some crudes and petroleum byproducts are excellent 

 substrates for many organisms, becoming part of an enriched food 

 chain, while others may be either poisonous or have virtually no food 

 value. Thus, one must know not only how much oil and grease is 

 present, but also their compositions and their effects on important 

 plants and animals. Much of the mortality in these accidents was caused 

 by the dispersant and not by the crude oil. 



NATURAL VARIABILITY 



A major gap in our knowledge of estuaries is an understanding of 

 natural variability. While there is a growing backlog of information 

 on natural variability within populations of certain estuarine animals, 

 the fluctuation of those parameters of the environment (such as tem- 

 perature, dissolved oxygen, sallinity, CO2, pH, turbidity, etc.), which 

 are recognized as controlling mechanisms for population distribu- 

 tions, are poorly understood. Maximum and minimum values, dura- 

 tion of excursions (period of increase, plateau, and decrease), and 

 time trends (ranging in intervals from hours to decades) in these en- 

 vironmental parameters must be intensively studied so that pollution 

 effects due to man's activity may be separated from natural environ- 

 mental fluctuations. We must also develop knowledge of the natural 

 variations in water quality that are encountered in estuarine and near- 

 shore areas in order to provide a basis for interpreting changes that 

 are brought about by human activity. Tidal flats and other estuarine 

 areas rich in various biological forms are highly productive. There is 

 a continual cycle of life, production, death, and decay in these areas 

 which apparently operates at a much higher level of activity than 

 might be encountered in fresh water systems. The magnitude of water 

 quality variations, caused by these natural effects is for the most part 

 unknown. Without knowledge of natural variations in water quality, 

 it is nearly impossible to set water quality standards. 



Range of natural variation 



An outstanding illustration of the need for understanding natural 

 variability is found in the Patuxent River, Md., estuary studies. A 

 long-term drought has resulted in an intrusion of a saline wedge into 

 the upper reaches of the river. A powerplant has been introducing 

 thermal effluents into the river. It has been impossible to distinguish 



