The impact of suspended sediment on juvenile Canaej> jnagistev, the 

 commercial crab of the central and northern Pacific coast of the United 

 States, was evaluated. Suspended-sediment concentrations covered a wide 

 range, with a maximum not exceeding the highest concentration documented 

 for dredging operations. Death was selected as the primary measured response 

 to establish the outer limits of tolerance. Only crabs 30 to 40 millimeters 

 in carapace width were studied. The absence of death in some cases does not 

 imply that the animals were not affected or that other life stages might not 

 have been killed. 



126. PEQUEGNAT, W.E., "Meiobenthos Ecosystems as Indicators of the Effects of 

 Dredging," Estuarine Eesearah^ Vol. 2, 1975, pp. 573-583. 



Critical data for assessing the long-term effects of marine dredging 

 activities on the benthos are analyzed. Meiobenthos constituents respond 

 definitely and for prolonged periods to mass sediment disruptions as evidenced 

 by changes in generation time, numbers, and diversity. Amelioration of these 

 responses may prove to be a true indicator of habitat reconstruction, in part 

 because of the close relationship of meiobenthos with sediment properties and 

 their intrinsic short-cycle properties. It was concluded that an investigation 

 of the significance of the response difference between the macrobenthos and 

 meiobenthos is needed. 



127. PFITZENMEYER, H.T., "Hydrographic and Ecological Effects of Enlargement 

 of the Chesapeake and Delaware Canal. Appendix III. Benthos of Mary- 

 land Waters In and Near C and D Canal," Report No. NRI-REF-73-113, 

 University of Maryland, National Resources Institute, Solomons, Md., 

 Sept. 1973. 



This study was undertaken to determine the seasonal occurrence and 

 biomass of species of benthic invertebrates inhabiting the C and D Canal and 

 Elk River. This information was used to assess the effects of enlargement 

 of the canal. 



128. PFITZENMEYER, H.T., "The Effects of Shallow-Water Channel Dredging on 

 the Community of Benthic Animals and Plants: Phase I. Survey of Pre- 

 viously Dredged Areas and Observation on the Physical and Biological 

 Effects," Report No. 75-69, University of Maryland, Center for Environ- 

 mental and Estuarine Studies, Solomons, Md., 1975. 



This study was designed as a preliminary investigation into the effects 

 of shallow-water channel dredging on the community of benthic animals and 

 plants. The objective of this phase was to determine through quantitative 

 means whether differences in the biota could be measured between channels and 

 corresponding reference areas. The physical qualities of the sediments at 

 each sampling station were also analyzed. No major damage was found to the 

 populations of benthic invertebrates in channels 2 to 4 years after dredging, 

 though no rooted vegetation was found in dredged areas. 



129. PFITZENMEYER, H.T., "The Effects of Shallow-Water Channel Dredging on 

 the Community of Benthic Animals and Plants: Phase II. A Study of 



43 



