99. MACKIN, J.G., "Canal Dredging and Silting in Louisiana Bays," Puhlications 

 of the Institute of Marine Soienoe, Vol. 8, University of Texas, Austin, 

 Tex., 1962, pp. 262-312. 



The effects of dredging on oysters were studied in the shallow bays of 

 Louisiana and discussed relative to the normally high turbidities of an erod- 

 ing marsh area. Data were taken from unpublished reports of the Texas A & M 

 Research Foundation. Three case histories of dredging were followed: a hy- 

 draulic dredge depositing a spoil island, a clam dredge operating in a canal, 

 and a hydraulic dredge depositing in a half-fan circle. Turbidities beyond 

 a few hundred meters of the dredges did not exceed the natural levels and 

 experiments showed no harmful effects on the oysters that were tested. 



Experiments Indicate that dead oysters did not consume oxygen during 

 decomposition at rates much greater than live oysters. The oxygen demand of 

 sediments dispersed in dredging was relatively less than that of surface sedi- 

 ments. Oxygen depletion with dredging in Louisiana marshes was found to be a 

 relatively minor factor not responsible for mortality. 



Cores were compared microscopically in control areas, in areas receiving 

 light silt from dredging, and in areas of heavy silt deposit in spoil deposi- 

 tion. Soft silt conditions affecting the distribution of oyster reefs were 

 traced to marsh erosion, disintegration, and subsidence, with cores unmistak- 

 ably different from those in spoil deposits. 



100. MANNING, J.H., "The Maryland Soft Shell Clam Industry and Its Effects 

 on Tidewater Resources," Research Study Report 11, Maryland Department 

 of Resources and Education, Annapolis, Md., 1957. 



Hydraulic clam dredging results in: (a) Displacement and deposition of 

 measurable quantities of sediment up to about 23 meters downcurrent from the 

 dredged area; (b) essentially the complete mortality of oysters within the 

 dredged area; (c) significant mortality of oysters 8 meters downstream from 

 the dredged area; (d) possible mortality of oyster spat up to 23 meters 

 downcurrent; and (e) no mortality of oysters or spat at distances greater than 

 23 meters from the dredged area. Effective revegetation of commercially pro- 

 ductive clam bottoms is not to be expected because dredging intervals will be 

 'too frequent to permit repopulation by plants. 



101. MARSH, J. A., Jr., and GORDON, G.D., "Marine Environmental Effects of 

 Dredging and Power-Plant Construction in Piti Bay and Piti Channel, 

 Guam," Technical Report 8, Guam College Marine Laboratory, Agana, Guam, 

 May 1974. 



Effects of construction activities in Tepungan Channel and the adjacent 

 reef flats of West Piti Bay were investigated with the use of a telethermome- 

 ter, sampling programs, and dye tracer studies. The major long-term environ- 

 mental effect caused by the dredging and construction activities was the inad- 

 vertent damage to the coral community in the western end of Piti Bay. The 

 coral community has now been replaced by an algae-echinoderm community. The 

 outlook for eventual restoration of the original coral community is uncertain. 

 The biological community in the newly enlarged channel itself is rather sparse. 

 Water turbidities on the Piti reef flats have returned more or less to normal. 

 No evidence was found that operations of the Piti plant or construction activi- 



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