VI-115 



estuarlne animals, the fluctuation of those parameters of the 

 environment (such as temperature, dissolved oxygen, salinity, 

 CO2, pH, turbidity, etc.), which are recognized as controlling 

 mechanisms for pooulation distributions, are poorly understood. 

 Maximum and minimum values, duration of excursions (period of 

 Increase, plateau, and decrease), and time trends (ranging in 

 intervals from hours to decades) in these environmental parame- 

 ters must be intensively studied so that pollution effects due 

 to man's activity may be separated from natural environmental 

 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 inter- 

 preting 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, pro- 

 duction, 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, Maryland, estuary 



