There is little direct evidence to serve as guidance in predicting the effects of offshore 

 removal of sand and gravel or of placing these materials for beach nourishment. The 

 information available is broadly general, incomplete, and often conflicting. It is necessary 

 to consider basic ecological mechanisms and principles plus applicable data gleaned from 

 studies of navigation, dredging, and beach fill projects. The end result, while not as precise 

 as would be hoped, turns out to be predictions based on more thorough study of principles 

 and observations. 



Two significant generalities can be stated at this point: (1) There is no objective reason, 

 uncovered in this study, why offshore dredging should not be carried out, providing it is 

 carried out with certain precautions to be enumerated; nor is there any reason discerned, 

 ecologically speaking, why the offshore material should not serve satisfactorily as beach 

 nourishment material. (2) Although the preceding statement, is couched in negative terms, 

 it is based on a comprehensive and detailed review, which has as its major shortcoming that 

 knowledge available (with few exceptions) deals with generalities, and detailed, local, 

 on-the-scene investigations must still be considered as necessary preludes (and postludes) to 

 cover local idiosyncracies and special local conditions. The remainder of this section is an 

 overview of the type of ecological data considered in evaluating effects, and predicting the 

 effects of action. It is a synthesis of material obtained from many sources and many 

 research studies made in the past 40 years. Not all of this material is documented in the 

 accompanying bibliographies, due to space hmitations. The bibhography includes a 

 selection deemed important as indicating trends, representing classic works, works with 

 above-average bibliographies, reviews, or works especially pertinent to the current problem. 

 Such a selection is necessarily subjective and reflects the mood and interests of the 

 compiler. 



There is in any ecological system a mass of obscuring detail. An attempt is made in the 

 following summary of ecological background to provide a frame for discussion to 

 emphasize the main flow. 

 2. Mainstream of Marine Coastal Ecology. 



a. The Inorganic Environment. Ecologically, the physical environment— the 

 substrate and the overlying water column with their contained characteristics— is important 

 to organisms because it provides a source of support, attachment, shelter, and food. 

 Substrate and water are important to life, as is the complex of interchanges between the 

 two. Of particular importance are interface phenomena between water-air, water -substrate, 

 and layers of substrate. 



Since sandy substrates are of chief concern here, two fundamental substrate situations 

 of great ecological importance are noted— unstable, shifting sand beds, and more stable, 

 nonshifting beds, usually with a greater admixture of silt, clay, or other material. Dredging 

 on unstable beds could be expected to have a less harmful effect, both short-range and 

 long-range, than would dredging on the nonshifting bed, though effects on shifting sand 

 areas would be more difficult to predict. 



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