For more than a decade after the spill one could easily see an oil sheen on the surface of the water whenever underlying mud in the most heavily oiled parts of the marsh was disturbed. Yet during that decade the overall visual appearance of the marsh returned to normal. Most of the area that had been oiled was slowly reinvaded by marsh grasses and reoccupied by marsh animals and an observer unfamiliar with Wild Harbor at the time of the spill would have been unable to detect the oiled areas after 10 years. Petroleum is composed of hundreds of related chemical compounds and for purposes of discussing their fates and effects can be conveniently divided into categories of similar chemical structure and biological effect. One group includes natural compounds, including plant waxes which are found on plant leaves, while another group is more characteristic of ancient petroleum rather than modern growing plants.
Some compounds are toxic to plants or animals, and can be carcinogenic or mutagenic.
For some compound types, microbial decomposition may be importent. Studies of the fate and effects of the oil spill began immediately in 1969 with studies led by WHOI scientists Howard Sanders and Max Blumer. Neighboring amphipod crustacea migrated into the area and were also killed by the oil. Fish, lobsters, crabs, shellfish, annelid worms and snails were all killed and washed up on beaches. Shellfishing was closed over a distance of several kilometers that year and for at least 6 additional years in Wild Harbor.