exported detritus could result. Net amounts of nutrients and sedi- 

 ment probably would not change significantly in areas frequently 

 inundated. In portions of salt marsh further removed from tidal 

 action, the faster movement of water on and off the marsh surface 

 may result in net losses (Copeland and Dickens, 1974). 



If the affected area is further removed from the estuary where 

 isolated ponds may exist, intramarsh circulation could be affected. 

 Depressions could connect individual water bodies and increase the 

 intermixing of their contents. Waterfowl and wading bird use would 

 be expected to increase in these new depressions with standing 

 water. At the ecosystem level, however, this increase is slight. 



The degree and significance of wildlife displacement resulting from 

 all preexploration activities is impossible to predict or quantify. 

 The point where noise and human presence may change temporary and 

 partial displacement to permanent and complete displacement is 

 unknown, but this factor should be considered during all phases of 

 activities since it extends the effects of the project beyond the 

 boundaries of the immediate site. 



4. Key attribute alterations 



The alteration which leads to the most significant impacts on the 

 ecosystem is the creation of depressions in the land surface. 

 Effects which are long term and large in areal extent may result 

 from induced changes in waterflow regimes. As discussed earlier, 

 the total area affected (and thus, the kinds and numbers of con- 

 sumers) is site specific. 



Gravity preexploration. 

 1. Activity sequence 



Gravity surveys may involve the placement of a relatively small 

 piece of equipment on the marsh surface. This unit (the gravity 

 meter) may be carried to stations by marsh buggy, boat, or foot. 

 Survey crews are not required since data need not come from predeter- 

 mined locations. It is necessary only to plot the locations of the 

 data-collection stations on a map. A small amount of vegetation is 

 trampled during the placement of the gravity meter. Several minutes 

 are required for data collection; the unit is then packed and carried 

 to the next station. The number of stations required for a gravity- 

 meter survey is less than the number of shot holes necessary for a 

 seismic survey. Two men with adequate transportation can efficiently 

 conduct a gravity-meter survey. 



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