Critical gaps exist in our knowledge of the life 

 history of even the most well known inshore 

 species. In particular, details of the early life are 

 lacking, and it is during this period that animals 

 appear most susceptible to environmental insults. 

 During this early period natural mortality is at its 

 highest rate and techniques for environmental 

 improvement could have their most positive effect. 

 Answers to important questions of waste disposal 

 —the timing, rate of disposal, and nature of 

 materials which may be added into the sea— all 

 depend on detailed hfe history studies. For ex- 

 ample, temperate zone species are mostly seasonal 

 spawners with egg and larvae production occurring 

 primarily in late winter and early spring. Rational 

 methods of pollution control to insure maximum 

 benefits to each user of the coastal zone almost 

 certainly must include a seasonal factor. However, 

 our knowledge is inadequate to develop this factor 

 and the most conservative stand must be taken to 

 assure appropriate protection of our Uving re- 

 sources. 



The rapid development of large power plants 

 using large quantities of water for cooling are 

 adding another dimension to the pollution prob- 

 lem in the coastal zone. The outflow from these 

 plants is of the order of 15-25° Fahrenheit above 

 the incoming water. Again, larval forms of animals 

 are usually least tolerant of such thermal shocks. 

 However, in most cases we do not know the 

 tolerance level. 



Another unknown is the effect of specific 

 pollutants on individual species at all stages of 

 their life cycles. Understanding must be gained on 

 these effects and on the long-term effects of 

 chronic low level pollution on the total ecosystem. 

 Of the eight classifications of water pollutants,'* 

 we do not understand the long-term effects of 

 some nor the thresholds of allowable concentra- 

 tion for others. 



Although any single source of pollution may be 

 innocuous, the sum total of all sources may be 

 very harmful and the combination of various 

 pollutants may have a synergistic effect. 



The long-term effects of low concentrations of 

 pollutants on estuarine organisms will require 



studies in the pathology and histology of marine 

 forms. These are little known at the present time. 

 Invertebrate pathology in particular has been 

 neglected. Nevertheless, pathological knowledge 

 and medical research techniques can contribute to 

 understanding the cause and effect relationships of 

 pollution and fish diseases. 



IV. ESTUARrWE DYNAMICS 



Advances of the past decade in instrumenta- 

 tion, signal processing theory, and computer data 

 analysis have substantially increased our capability 

 for studying estuarine circulation. Because the 

 effects of turbulent motion in an estuary are 

 usually more important than the mean values, it is 

 necessary to carry out detailed, long-term pro- 

 grams to measure the turbulent fluxes of the 

 various dissolved or suspended quantities. Because 

 of their complexity, most estuarine studies have 

 been highly empirical. With instrumentation now 

 available, currents in an estuary could be examined 

 well enough to allow a better understanding of the 



The classifications of water pollutants are discussed 

 in Chapter 4. They are BOD wastes, infectious agents, 

 plant nutrients, organic chemicals, mineral chemicals, 

 sediments, radioactivity, and thermal addition. 



Figure 3. Hydraulic model studies of Umpqua 

 River estuary, Oregon, at the U.S. Army Engi- 

 neer Waterways Experiment Station, Vicks- 

 burg, Mississippi Such models contribute to 

 the understanding of estuarine dynamics and 

 the effects of engineering modifications. (U.S. 

 Corps of Engineers photo) 



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