Mangrove Oiling

Effects of Oil Pollution on the Red Mangrove,
Rhizophora mangle L.

The Comparative Ecological Risk Assessment (CERA) approach was used to determine the ecological consequences of spills of two different fuels, Fuel Oil #6 and Orimulsion. Orimulsion is an emulsified bitumen being extracted in Venezuela, that has a number of attributes making it a desirable boiler fuel for Florida Power and Light (FPL).

A part of the COSAP (Comparative Oil/Orimulsion Spill Assessment Program) project coordinated by CMEA focused on characterizing the ecological effects of these two fuels on mangroves. Accordingly a number of experiments were undertaken to elucidate the consequences of exposure of the red mangrove, Rhizophora mangle, to these two fuels. The results of two of these experiments (aerial and sediment dosing) are presented.

The aerial dosing experiment simulated the coating of seedlings by oil carried onshore during the tidal cycle. The results indicate that Fuel Oil #6 is more detrimental than Orimulsion to mangrove seedling productivity and growth.

The sediment dosing experiment simulated the effects of stranding and trapping of oil in intertidal mangrove sediments. The results indicate leaf productivity was similarly affected by both fuels. Stem growth was found to be sensitive to the exposed concentration for each fuel. Leaf length and width were reduced, indicating increased stress proportionate to the concentration of the fuel. Measurements of physiological stress, by stomatal conductance and chlorophyll a fluorescence induction techniques, confirm these results. Stomatal conductance decreased with increasing fuel concentration, and Orimulsion had a significantly greater impact at higher concentrations than Fuel Oil #6. However, adverse effects on the photosynthetic ability of the seedlings were not evident for either fuel.

From the results obtained it is concluded that direct or indirect exposure to refugee Orimulsion will not have any serious or consequential long term impact on mangroves.

Publications from this research:

Snedaker, S.C., and P.D. Biber 1995. Effect of Fuel oil No. 6 and Orimulsion on mangroves. Chp 6 in J.S. Ault and M.A. Harwell (eds) Comparative Ecological Risk Assessment, Vol 2: Technical Support Document for the Comparison of the Ecological Risks to the Tampa Bay Ecosystem from Spills of Fuel Oil No. 6 and Orimulsion. CMEA, RSMAS, Univ. Miami, FL.

Snedaker, S.C., and P.D. Biber 1996. Restoration of mangroves in the United States of America: a case study in Florida. Pages 170-188 in C.D. Field (ed) Restoration of Mangrove Ecosystems. ISME, Okinawa, Japan

Snedaker, S.C., P.D. Biber and R.J. Araujo. 1997. Oil spills and mangroves: an overview. Pages 1-18 in C.E. Proffitt (ed.) Managing Oil Spills in Mangrove Ecosystems: Effects, Remediation, Restoration and Modeling. OCS MMS 97-0003. US Dept of the Interior. Minerals Management Service, Washington, DC.

Snedaker, S.C., S.M. Smith, P.D. Biber and R.J. Araujo. 2001. Comparative effects of Orimulsion and Fuel Oil No. 6 on floating and stranded propagules, and established seedlings of Rhizophora mangle L. In N.R. Bhat, F.K. Taha and A.Y. Al-Nasser (Eds) Mangrove Ecosystems: Natural Distribution, Biology and Management. Kuwait Institute for Scientific Research.