which includes taxonomic identification, varies from 1 to 4 hours for beach 

 samples with 25 to 75 species and 6 to 10 hours for nearshore samples with 200 

 to 300 species (Dr. R. Diaz, Virginia Institute of Marine Science, personal 

 communication, ^lay 1981) . 



VII, EFFECTS OF BEACH NOURISHMENT 



Recent studies have demonstrated that beach nourishment activities may be 

 detrimental, beneficial, or have no marked effect on the fauna, depending on 

 the local situation. The Appendix provides a listing of the most recent reports 

 on different aspects of beach nourishment and associated borrowing indicated by 

 reference numbers in the Literature Cited. Major conclusions from these reports 

 have been included in the current report to aid the manager in visualizing the 

 possible effects of such a project. 



1. Physical Effects . 



There are three major ways that beach nourishment physically impacts the 

 beach environment; the deposited material covers the existing beach sediments, 

 modifies the beach interface, and frequently increases the turbidity of the 

 nearshore area (Fig. 1). Waves and currents winnow and suspend sediments in 

 the water along a nourished beach, increasing the turbidity of the water. 

 Parr, Diener, and Lacy (1978) observed at Imperial Beach, California, that the 

 fine sediments were rapidly sorted out of deposited material and that sediment 

 grain-size distribution after about A months was comparable to that before 

 nourishment. The fine sediments were transported offshore. Courtenay, Hartig, 

 and Loisel (1980) also observed sediments that lodged against and partly 

 covered low profile coral reefs off the Florida east coast. Regardless of 

 origin, sediment movement and changes in grain-size distribution may create 

 a benthic environment that requires marine organisms to adjust or perish. 

 Pearson and Riggs (1981) stated the critical importance of matching nourish- 

 ment material to the hydraulic energies of the beach. Placed material that is 

 not in equilibrium will erode to offshore areas. 



Turbidities resulting from beach nourishment generally create only a minor 

 impact in the surf and offshore zones, except in areas of environmentally 

 sensitive resources that easily smother or are dependent on light for photo- 

 synthesis. 



2. Effects on Benthic Communities . 



The marine bottom communities on most high-energy coastal beaches survive 

 periodic changes related to the natural erosion and accretion cycles and 

 storms. However, nearshore communities are in a more stable environment and 

 are less adaptable to such perturbations. Direct burial of beach nourishment 

 material on nonmotile forms would be generally lethal, while motile animals 

 might escape injury. Some infaunal bivalves and crustaceans can migrate 

 vertically through the sediments. Maurer, et al. (1978) observed in a labora- 

 tory experiment that some benthic animals are able to migrate vertically through 

 more than 30 centimeters of sediment. However, their survival depends not only 

 on the sediment depth, but also on length of burial time, season, particle- 

 size distribution, and other habitat requirements of the animal. 



!9 



