community composition, (Wilson, 1952; McNulty, Work, and Moore, 1962; 

 Thorson, 1966; Sanders, 1968; Bloom, Simon, and Hunter, 1972; Gray, 

 1974). Jansson (1967) described grain-size distribution as the major 

 environmental parameter influencing the distribution of infaunal 

 animals. The fact that sediments within the borrow area were 

 significantly coarser than at the control stations may explain the 

 faunal differences observed. Following its excavation, the borrow pit 

 became, in effect, a new benthic habitat open to colonization by 

 Planktonic larvae, many of which are known to be highly selective for 

 various sediment parameters, including grain size. 



Faunal densities recorded in this study were generally lower than 

 those reported by Marsh, et al.(1980) for offshore areas at Hallandale 

 and Golden Beach, Florida, approximately 35 kilometers to the south. 

 Their study included samples from stations between the first and second 

 reefs, as in the present study, although their sampling area was 

 shallower (6 meters compared to 10 to 15 meters off Hillsboro Beach). 

 Moreover, sediments off Golden Beach and Hallandale were coarser than 

 at Hillsboro Beach. Marsh, et al . (1980), using a similar screen size, 

 reported faunal densities ranging from 11,305 to 17,144 individuals per 

 square meter during November-December 1977. Oligochaetes accounted 

 for 38.3 percent of the fauna collected. In our study, faunal 

 densities ranged from 1,729 to 4,381 individuals per square meter, in 

 December with oligochaetes accounting for only 1.4 percent of the 

 fauna. Thus, considerable faunal heterogeneity can occur within a 

 short length of coastline. 



It is concluded that the offshore dredging operations conducted in 

 1972 off Hillsboro Beach, Florida, caused no long-term observable 

 adverse effects, in terms of reduced numbers of species, reduced faunal 

 abundance, or reduced species diversity within the borrow area. 

 Qualitative changes in the borrow area, as indicated by cluster 

 analysis, were not considered detrimental. 



VI . SUMMARY 



The long-term ecological effects of dredging for beach restoration 

 were investigated off Hillsboro Beach (Broward County), Florida. 

 Benthic fauna were collected quarterly for 1 year, by scuba divers 

 using a hand-driven .PVC coring tube, from four offshore stations. 

 Control stations 1 and 2 represented relatively undisturbed bottom; 

 borrow stations 3 and 4 were within an area excavated 5 years 

 previously. 



At each station during the initial sampling date, three replicate 

 sediment samples were collected for analysis. Borrow stations 3 and 4 

 had significantly coarser sediments than control stations 1 and 2. 

 There was no significant difference in organic content among stations. 



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