bulkhead provides a new habitat for a 

 few sessile and marine boring organ- 

 isms, such as barnacles, hydroids, 

 gribbles, and shipworms. 



The newly created deep water zone 

 in front of a bulkhead often has a lower 

 concentration of detritus, lower phyto- 

 plankton production, and fewer benthic 

 organisms than adjacent unbulkheaded 

 areas (Massachusetts Coastal Zone Man- 

 agement Program undated b, Odum 

 1970). The turbulence and scouring 

 action in front of bulkheads from re- 

 flected wave energy often prohibits 

 vegetation from reestablishing (Gantt 

 1975, Knutson 1977) and may destroy 

 existing grass flats (Gifford 1977). 



Ellifrit et al. (1972) studied clam 

 populations in bulkheaded and adjacent 

 natural areas in Hood Canal, Washing- 

 ton. Twice as many clams were found 

 on natural beaches at three out of the 

 four sites studied. At two sites signif- 

 icantly more Japanese littleneck clams, 

 Venerupis japonica , were found in up- 

 per intertidal regions. Differences in 

 size and distribution were noted. Clams 

 in the lower intertidal regions appeared 

 unaffected by bulkheads. The authors 

 concluded that these differences pro- 

 bably were due to changes in current 

 patterns associated with bulkheads. 

 Bulkheads appeared to produce less fa- 

 vorable conditions for settling and sur- 

 vival of clam larvae and may have caus- 

 ed reduction in availability of nutrients 

 and food. 



Moore and Trent (1971) studied 

 settling, growth, and mortality of oysters 

 in two areas in West Bay, Texas. The 

 first area was a dead end canal that 

 had been created by dredging, bulk- 

 heading, and filling of a coastal marsh. 

 The second area was a dead end bayou 

 in an unaltered part of the same marsh. 

 The settling of oysters was 14 times 

 greater in the natural marsh than in 

 the canal area. Faster growth rates 

 and lower annual mortality rates charac- 

 terized oysters in the natural marsh. 

 The authors attributed these differences 

 to the poor water circulation, plankton 

 blooms, low levels of dissolved oxygen, 

 and high nutrient levels in the canals. 



Studies of shrimp in bulkheaded 



and natural estuarine habitats have 

 shown natural areas to be more produc- 

 tive (Mock 1966, Trent et al. 1976). 

 These differences have been attributed 

 to low abundance of organic detritus and 

 benthic macroinvertebrates, deeper wa- 

 ter, and loss of intertidal vegetation 

 in bulkheaded areas. 



Bulkheads also can affect fish 

 spawning, feeding, and nursery habitat. 

 For example, bulkheads have been shown 

 to alter salmon fry behavior in Puget 

 Sound, Washington (Heiser and Finn 1970, 

 Stockley 1974). Vertical bulkheads cause 

 an abrupt habitat change with few shal- 

 low water areas. Salmon fry tend either 

 to go out into deeper water when con- 

 fronted with a bulkhead or to concen- 

 trate near bulkheads and not go around 

 them. Both circumstances make salmon 

 fry extremely vulnerable to predation. 

 Stair-step design bulkheads or riprap 

 revetments on a 45 or less degree angle 

 were found to provide protective habitat 

 for salmon fry (Heiser and Finn 1970). 

 In another study, (Millikan et al. 1974) 

 bulkheads extending down below the mean 

 high waterline were found to bury and 

 destroy smelt spawning substrate in 

 Puget Sound and Hood Canal, Washington. 

 As a result of this study, State bulk- 

 head criteria for surf smelt spawning 

 beaches were modified to protect upper 

 intertidal and sand-fine gravel beach 

 areas. 



Cu mulative effects . Physical and 

 biological impacts from the construction 

 of a number of bulkheads in a coastal 

 area may have a cumulative effect, how- 

 ever, no pertinent studies were found. 

 Irregular alignment and patchy bulkhead- 

 ing along a shoreline often create ero- 

 sion pockets between bulkheads on natu- 

 ral beaches (Bauer 1975). Extensive 

 bulkheading of wetlands on the shores of 

 estuaries and bays can severely reduce 

 fish and wildlife habitat and impact es- 

 tuarine related fisheries of a whole re- 

 gion, as well as waterfowl populations. 

 For example, Lindall (1973) identified 

 bulkheading of south Florida's estuarine 

 shorelines and the resulting destruction 

 of the nursery grounds as a threat to 

 the estuarine-dependent fisheries (about 

 85% of the area's commercial fisheries) 

 of that region. Clearly, examination of 

 the physical and biological impacts of 



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