In addition, where present, beach grasses are holders of the substrate. Unfortunately, 

 tourists like beaches composed of clean, clear sand, thus, the interstitial animals, which no 

 one sees and about which few are concerned, remain the primary cementing agents. 



c. Biotic Dependence on Physical and Chemical Characteristics. As elsewhere, there 

 is a strong correlation between the types of life found and the characteristics of the 

 substratum. This is marked in the lower zone of the beach that is especially rich in 

 interstitial fauna. Such sediment factors as grain size, polarization, latticework structure, 

 and even mineral content influence the fauna. In general, the smaller the sediment grains, 

 the smaller the interstices, and the smaller the individuals of the fauna. Correlated with 

 fine sand is a decreased capacity for holding oxygen. Organic content is also important in 

 settlement of the larvae of the tube-dwelling worms and other groups. The bacteria and 

 unicellular algae are usually present as films or patches on and around the sand grains. 

 Differences in available surface area and in size of interstices markedly affect these 

 organisms, which are important in primary productivity and as food for the herbivores. 



d. Ecological Effects of Deposition of Fill (Nourishment on Sand Beaches). At first 

 glance it would seem that to dump quantities of sand on top of the normal beach surface 

 would have serious consequences on the biota. Mechanical disturbance alone would seem 

 to have far-reaching disruptive qualities. But this is not entirely true. It has been shown 

 that the animals of the beaches are accustomed to change— incorporating change into their 

 daily lives. Further, most faunistic members are agile and capable of escape from or 

 lengthy resistance to adverse conditions. Moreover, migrations from adjoining sides of the 

 nourished area are likely either in the form of adult or larval organisms coming in to fill 

 empty niches. Studies of succession in areas nourished with material taken inland, show a 

 rapid invasion of fauna and little lasting harm is apparent. 



The least effect would ensue if the sand placed on the beach resembled the original sand 

 in grain size and other physical characteristics. The effects of change in profile could also 

 be important. The three zones outlined earlier, are defined not only faunistically, but in 

 relation to water levels— above water, water- land interface (alternately above and 

 submerged), and totally submerged. Altering the profile would necessarily alter the 

 proportion of surface available for each zone; hence, it would alter the proportion of fauna 

 typifying each zone, with unknown, but possibly important, effects on the environment. 



To summarize, no far-reaching or long-lasting effects from offshore dredging can be 

 foreseen, nor can detrimental effects be foreseen from deposition of offshore sediments as 

 beach fill. Further research is needed before the more subtle relationships that might prove 

 disastrous are completely known. But, in the gross view, the conclusion stands. Design and 

 monitoring of dredging operations and fill projects should receive careful attention to 

 safeguard against damage, and to continue before, during, and after studies. 

 ffl. ECOLOGICAL ENGINEERING 



If offshore sand dredging coupled with beach fill can be looked upon as a single 

 operation, designed specifically and uniquely for improvement of the coastal environment, 

 a major breakthrough could be gained in the improvement of the environment. By 



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