eel, and the herring gull. Oil was detectable as deep as 70 cm in marsh sediments, and this is in marked contrast to previous observations that marsh sediments were uncontaminated by oil or that oil was restricted to the upper 5 to 10 cm. Burns and Teal further noted that there had been a reduction in straight chain alkanes in relation to branched chain and cyclic alkanes and aromatics since the original pollution, and that although oil was obviously taken in by organisms, there was no evidence of food chain magnification.

Repetitive or chronic oil pollution as found near an oil terminal or refinery effluent can have a decidedly harmful effect on salt marshes. Baker's experiments () indicate that more than two or three fresh oil spills a year or one or two light oilings per year with weathered oil for many years would severely reduce marsh grasses. Much of a marsh near a refinery effluent in Southampton was completely denuded by the chronic low-level pollution from the effluent (). Apparently the grasses were killed by being constantly coated with thin oil films. The loss of grass cover resulted in rapid erosion of the marsh bank.

Chronic pollution of salt marshes can have obviously serious effects, but the effects of a single oiling may be quite variable, depending in part on the factors discussed above. Although most studies have not uncovered significant effects, oils as different as the light, aromatic-rich Number 2 oil spilled at West Falmouth, and the heavy, less toxic Bunker C lost from the Arrow are clearly harmful to marsh plants and animals. The effects of oil on marsh organisms other than vascular plants have generally not been studied. Clearly, further investigations should consider the smaller, less obvious, but nonetheless integral organisms of the sediment surface. Also, the findings of Burns and Teal make chemical analysis of organisms and sediments advisable.

Mangrove swamps are not as well studied as salt marshes. Consequently, we lack the necessary basic and practical information to make conclusions about the effects of oil on these environments (see 5). Spills in Puerto Rico () and in Panama () have killed mangrove trees and associated animals. Mangrove swamps will conceivably suffer more pollution as offshore oil production in the tropics increases.