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can survive. The pesticide group is of particular concern in the estua- 

 rine zone. Estuaries are the terminus for most of the major river 

 systems, and as such they tend to concentrate the waterborne materials 

 carried in by the large terrestrial drainage systems. The biological 

 magnification capability of estuarine animals significantly increases 

 the hazard and destructive potential of any contributed pesticides. The 

 ultimate damage is to stress or eliminate parts of the energy conversion 

 chain in the estuarine environment. 



The addition of large quantities of heat from industrial cooling 

 water constitutes a form of pollution which must be considered. The 

 entire ecosystem may be stressed by thermal pollution. The amount 

 of damage is dependent on the resulting temperature of the environ- 

 ment and the species composition of the biotic community. The total 

 range of detriments should be carefully considered on an individual 

 basis before heat is released to the environment. Heat affects the 

 physical properties of water, the rates at which chemical and biologi- 

 cal reactions progress, and can kill living organisms. 



Man's activities may affect the rate at which the natural balance 

 of inflow, deposition, and outflow is reached by purposely or inad- 

 vertently upsetting this balance. If upstream erosion is increased due 

 to poor land management practices, the load carried in will increase. 

 Conversely activities along the coast can result in increased shore 

 erosion, removing more sediment than is contributed. The primary 

 pollutional problem from sediment, however, is from increased influx 

 and accelerated deposition. The detrimental effects of sedimentation 

 are reflected in an impairment of uses such as navigation, recreation, 

 and fish propagation. 



One of the greatest threats to the estuarine ecosystem is the ever- 

 present chance for a catastrophic spill of oil or other hazardous ma- 

 terials. The liarge volumes of petroleum and chemical products trans- 

 ported through the estuarine zone by ships, barges, pipelines, tracks, 

 and railroads present a continuing opportunity for accidental bulk 

 spills. The consequences of these spills depend on the amount and type 

 of material released and the characteristics of the receiving water. 

 They may range in magnitude from tragic loss of life to little more 

 than economic loss for the transporter. 



The effect any pollutant has on an estuarine environment depends 

 on where it goes, how strong it is, and how rapidly it is assimilated 

 or flushed out of the environment. All of these conditions depend on 

 water movement and circulation patterns which are in turn governed 

 by the relationship of tide and river flow to estuarine shape and size. 

 Physical modifications such as the dredging of new or deeper naviga- 

 tion channels, building of causeways of jetties, and even construction 

 of pier bridges can cause subtle changes in water movement that can 

 change the balance of environmental conditions in an estuarine system 

 and result in gradual undesirable changes in the ecosystem in addition 

 to direct habitat damage. 



SOURCES OF POLLUTION 



Nearly all of man's activities can result in environmental degrada- 

 tion. Pollutants and polluting conditions are very rarely unique to a 

 particular use or specific activity, but may result from man's existence 



