Abstract
To assess the severity of oil spills on mangroves, diagnosis of the vegetation health is crucial. Some aspects of photosynthesis such as photochemical efficiency and leaf pigment composition together with the level of oxidative stress may constitute reliable indicators for vegetation health. To test this approach 14 month old Laguncularia racemosa were contaminated with 5 L m−2 of the marine fuel oil MF-380 and treated with an oil degrading bacterial consortium in microcosms. Contamination resulted in a 20% decrease in shoot dry weight after 128 days. Photochemical efficiency, pigment content, catalase and ascorbate peroxidase remained unchanged. Multivariate ordination of DGGE microbial community fingerprints revealed a pronounced separation between the oil contaminated and the non-contaminated samples. Further studies are necessary before physiological parameters can be recommended as indicators for plant's health in oil polluted mangroves.
► L. racemosa growth rate was reduced by 20% in response to a simulated oil spill of 5 L m−2 in a microcosm. ► Photochemistry was not directly affected by the oil contamination during the 128-day experiment. ► Oil contamination changed the rhizobacterial community. ► The oil degrading bacteria consortium did not affect plant growth.
Despite the need to establish methods to diagnose the health status of mangroves little is known about the impacts of petrochemicals on mangrove plants and associated rhizosphere microorganisms.