The effects of oil pollution on mangroves and fisheries in Ecuador and Colombia

Abstract

The damage to mangrove communities and fisheries were studied following extensive oil pollution of the coastal areas of northern Ecuador and southern Colombia in 1976. During the acute phase of the oil spill oil covered 2–3 m vertically on the mangrove trees along the sea front, and had penetrated 20–70 m horizontally. Acute effects on the mangrove communities included defoliation of trees, mortality of sessile organisms, and migration of semi-sessile and mobile crustaceans and molluscs. Dead fishes, sea snakes and sea birds were also found. The relatively large tidal range caused considerable washing off of the deposited oil from roots and trunks, and four months later the major part of the oil on the mangrove trees had disappeared. Previously defoliated mangroves had, with some exceptions, recovered, and mobile organisms had re-entered the affected area. In some areas where mangrove had died there was erosion of the substrate. The oil spill affected the local fishery in a number of ways; for example, the absence of tuna in the region during that year suggested oil avoidance reactions in this group.