recolonization of some biota. Oil deposited during spring tides is 

 particularly persistent. Small amounts of oil may persist for some time in 

 areas such as rock crevices, seaweed, barnacle, or mussel beds (Nelson-Smith 

 1973). 



In combination with wave-action, the physical nature of a shore determines the 

 rate at which oil is dispersed. Rocky shores are cleansed naturally more 

 easily than sand beaches, and the cobble or gravel beaches are less easily 

 cleansed than the sand beaches. Sand and mud flats and salt marshes are the 

 least easily cleansed habitats (Owens 1978) . 



The formation of sea ice or an ice foot, which may cover up to two-thirds of 

 the intertidal zone, is characteristic of estuaries and embayments of coastal 

 Maine. These formations sometimes trap oil between the sediment and the ice, 

 where the toxic element will remain until the ice breaks up. Through wave- 

 action oil also may become trapped between layers of ice or between layers of 

 sand, creating a source of dispersal over several months. These formations of 

 ice can serve as a protective covering to the underlying sediments until the 

 spilled oil is dispersed (Owens 1978). 



Many species of bacteria, fungi, and yeasts are capable of degrading petroleum 

 hydrocarbons. Each species is limited in the types of hydrocarbon it may 

 attack. Although the rate of microbial degradation is related directly to 

 temperature (Nelson-Smith 1973), most investigators believe that the microbes 

 are limited most by dissolved oxygen, phosphates, and nitrates (Colwell et al. 

 1978). The activities of deposit-feeding benthic invertebrates have been 

 found to significantly increase the microbial degradation of petroleum 

 hydrocarbons in oiled sediments (Gordon et al. 1978). The very slow microbial 

 degradation of petroleum hydrocarbons on, in, or under a layer of ice may have 

 a considerable impact on the estuaries of Maine, which sometimes are covered 

 with ice during the greater portion of winter. 



The effects of oil on the food chain in a habitat vary. The extent of damage 

 is a function of many factors, including the toxicity of the oil, the duration 

 of exposure, environmental conditions (including temperature), time of year, 

 the physiological state of the organisms, and the degree to which the 

 organisms are subjected to other forms of stress. 



Toxic effects of oil on small benthic organisms include coating and 

 asphyxiation, ingestion, and the destruction of juveniles. Among the 

 sublethal effects are abnormal growths in soft-shelled clams, abnormal 

 development of barnacle and sea urchin larvae, delayed moulting of lobsters, 

 abnormal sexual behavior of fiddler crabs, interference with chemoreception in 

 lobsters, amphipods , and mud snails; interference with reproduction in birds, 

 and altered behavior in waterbirds (Snyder et al. 1973; and Butler et al. 

 1974). 



Communities of organisms have been impacted by oil spills. At Chedabucto Bay, 

 Nova Scotia, Thomas (1978) found lower animal diversity at sites that were 

 oiled 6 years before the sampling than at control sites that were oil-free. 

 At West Falmouth, Massachusetts, the spillage of No. 2 fuel oil completely 

 decimated the benthic fauna at severely oiled sites (Sanders 1978). 



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