Dredging may affect fish populations in a number of ways. Spawning sites may 

 be smothered with sediment, which either prevents spawning or covers the eggs 

 and larvae. Spawning sites also may be removed altogether, along with the 

 required vegetative cover. Increased sedimentation sometimes raises the 

 biological oxygen demand (BOD) of the water, potentially reducing available 

 dissolved oxygen to dangerously low levels. Mechanical destruction of gill 

 filaments may occur at high sediment levels. 



The exchange and transport of different types of sediment also are affected by 

 dredging. Excavation upsets local sediment transport, when coarse-grained 

 sediments are removed from local environments. Excavations of a small volume 

 of material are generally inconsequential, but continued excavation of small 

 amounts, especially on small beaches, depletes beach sediment supply. (See 

 page 2-43, "Shoreline Erosion," in chapter 2.) 



The disposal of dredge spoils is a serious environmental issue. The dumping 

 of dredge spoil on submerged bottoms may suffocate vegetated environments, 

 raise substrata to different intertidal heights, thereby affecting flora and 

 fauna, and smother benthic organisms. Fill deposits in the intertidal zone 

 are redistributed by tidal flow, increasing sedimentation on down-current 

 substrata. In addition, turbidity and the release of trapped pollutants and 

 organic matter may be additional problems. The U. S. Army Corps of Engineers, 

 in their Dredged Material Research Program, have studied some beneficial uses 

 of spoil, such as habitat creation. 



The potential impacts on the food web in the areas near dredge and disposal 

 sites include changes in nutrients and in populations of phytoplankton 

 (producers) and benthos (consumers), which in turn affect fish, bird, and 

 marine mammal populations. Cumulative impacts of projects may have long-term 

 effects on species populations. Monitoring of these ecological consequences 

 in coastal Maine has not been undertaken. 



TRANSPORTATION 



Ecological effects of transportation in coastal Maine are associated primarily 

 with right-of-way corridors for railways, roads, and airports (see 

 "Socioeconomics," chapter 2. The impacts of ports and navigation and 

 construction activities are considered under "Ports and Navigation" above). 



Some of the general impacts of roads and airports include altered surface 

 water drainage, restricted natural flow of waters, degraded air quality, and 

 loss of natural habitats. Runoff from impervious surfaces may include street 

 salt, sand, motor vehicle drippings, garbage, stagnant water, and other toxic 

 residues (Clark 1974). Roads may restrict the natural flow of water, 

 resulting in changes in habitat. In some instances, areas of forests may 

 become wetlands because of restricted flow of water. In other areas, the 

 restricted flow of water may result in altered sedimentation, which may 

 affect, for example, the benthic community in intertidal areas. Air-quality 

 impacts associated with the use of roads are primarily local in scope and 

 result from carbon monoxide and particulates. In addition, automobile travel 

 in Maine, particularly during the summer tourist season, contributes to an 

 ozone problem throughout the coastal zone (see "Air Pollution" under "Industry 

 and Population" below) . 



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