Smithsonian Sorting Center, Washington, D.C., or stand on dusty shelves in the marine 

 laboratories of the world. Correlations may be made between the egg and immature stages 

 of fishes and invertebrates in the plankton, and biomasses of the adults in given areas may 

 be calculated. 



Thus, for large-scale areas, including potential dredge areas, data are available on the 

 characteristics of the overlying water masses and their biota, with some correctable data 

 on bottom-dwelling organisms. These data, however, must be supplemented with detailed 

 local studies to be useful from an engineering standpoint. More detailed or more specific 

 follow-up studies are needed. 

 3. Bottom Inhabitants and Associated Organisms. 



Bottom-dwelling organisms, from bacteria to bottom-dwelling fish would bear much of 

 the impact of dredging activities. 



Sandy offshore bottoms that support a varied biota may be divided into two categories. 

 First, there are those areas composed of shifting, usually pure, sand. This habitat is usually 

 sparsely populated by animals that are mobile, relatively wide-ranging, and agile. 

 Community structure is neither permanent nor intricate. Second, there are the more stable 

 areas, usually composed of sand with silt, mud, or detritus, where the biota is richer, more 

 varied, and more permanent. Though either catagory might be dredged this second habitat 

 is of primary concern, for it presents greater ecological problems, and is of greater 

 ecological importance. 



Associated with the sandy substrate, especially the more stable, are a host of 

 microscopic, semimicroscopic, and macroscopic organisms which are generally sessile and 

 can best be sampled with a grab. A grab is an instrument somewhat like a small 

 steamshovel bucket, which bites a predetermined volume of bottom material. Such 

 sampling is known as quantitative bottom sampling, and from it is derived an estimate of 

 bottom biomass. This estimate is often too low, but as the method is standard, it provides 

 an index for comparing different areas. Such grab-derived estimates of richness or poverty 

 of areas are available for broad comparisons from the National Oceanographic Data Center. 



The oragnisms commonly taken by the grab on sandy bottoms are annelid worms, 

 echinoderms, crustaceans, and molluscs in addition to the omnipresent bacteria, algae, and 

 protozoans. 



Most of these organisms lie on the bottom or are shallow burrowers. They serve as food 

 for higher organisms including fish, and are responsible for the presence of the higher 

 organisms. Several commercially important molluca such as surf clams and quahogs also 

 fall in this category. 



Immediately above the bottom, in the lowermost water layers, is a transition zone rich 

 in fauna, known as an ecotone. This is an area at the junction of two interfaces presenting 

 the ecological advantages of both, as the border between a field and a woodlot in a 

 terrestrial situation. Here are found many bottom-dependent fishes and crustaceans which 

 feed on the smaller burrowers, crustaceans, and smaller fish. Of these, the flounder, other 

 flatfish, crabs, and shrimp are of great importance to man. Commercial fisheries operate on 

 these sandy grounds. 



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