Riverine- -slow moving steam . As the topographical gradient decreases, 

 the physical and ecological characteristics of a stream change. Consequently, 

 a different set of factors must be considered to determine the impact of 

 spilled oil. In most watersheds, the slower moving water is present in the 

 lower end of the hydrological gradient, where there is a large volume of water 

 in the stream channel. 



These stream types are more commonly impacted from navigation-related 

 incidents. As a whole, slow-moving rivers are apt to be more impacted by 

 man's activities from population centers that have developed on the shorelines. 

 More typically, this type of community will support a warm water fishery, par- 

 ticularly an urban fishery. Although an oil spill on a slow-moving stream may 

 not move as a slug and have the same devastating effect as on the rapid stream 

 habitat, the impact may be determined in terms of diminished populations or 

 outright fish kills. Physical features such as backwaters and oxbow forma- 

 tions may be present, which encouraged the formation of wetlands and flood- 

 plain woodlands. 



Lacustrine--ponds and lakes . One normally thinks of ponds as being 

 smaller and shallower than lakes and having different ecological features. 

 When an oil spill occurs in a watershed that includes ponds, these ponds serve 

 as natural sumps or collection points for floating oil. The impact of the 

 accumulated oil can be drastic, particularly if it has toxic components that 

 are water soluble or increase the biomass exposure probability. 



Lakes . One usually thinks of lakes as being much larger, deeper bodies 

 of water with different, more complex physical, chemical characteristics. 

 These features create conditions that must be considered when evaluating the 

 sensitivities of the ecology and also the impact from oil spills. In large 

 lakes exposed to winds with a variety of shorelines, the impact will vary 

 with shoreline. The sensitivity relative to the effects of an oil spill also 

 will vary with shoreline types. 



Endangered Species 



Most of those aquatic species now listed on the endangered species 1 ist — 

 (Department of the Interior 1979) from the obscure Maryland darter to the Bald 

 Eagle--! ive in or depend upon the fresh water domain for their existence. 



Locally Important Species 



Although some fresh water species may not be considered endangered or 

 threatened, on a local basis, some species may be important esthetically or 

 commercially. In this latter case, these species may be especially endeared 

 to the local populace. In the NEPCO 140 Spill, the Great Blue Heron was 

 classified into this category. 



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