Mitigation strategies at an estuarine mangrove area affected by an oil spill

Abstract

A simulated oil spill was carried out under controlled conditions at an estuarine mangrove forest dominated by Rhizophora mangle. Two mitigation strategies were thereafter applied: addition of nutrients to restore sediments C/N and C/P ratios and addition of a commercial shoreline cleaner without further surface washing. Photosynthetic capacity of leaves, soil respiration rate, and litter disappearance rate were measured periodically to evaluate differential responses of these community functional variables to the treatments. Application of shoreline cleaner negatively affected the productive capacity of R. mangle leaves. Soil respiration rate was stimulated in all of the oiled experimental plots but to a lesser extent in those where shoreline cleaner was applied - presumably as a result of less retention of hydrocarbon fractions in the sediments. Although litter increased its dry weight by 0.4 percent as a result of hydrocarbon addition, its disappearance rate did not slow down and remained unaltered among the different treatments compared to controls. Results suggest that the studied mangrove community possesses the capability to respond to moderate, medium crude oil spills. Neither the use of a shoreline cleaner nor the addition of nutrients alone is recommended as a mitigation strategy under such conditions.