MANGROVE LEAF TISSUE SODIUM AND POTASSIUM ION CONCENTRATIONS AS SUBLETHAL INDICATORS OF OIL STRESS IN MANGROVE TREES

ABSTRACT As part of an ongoing study of the long-term effects of the Zoe Colocotroni oil spill of March 17, 1973, in Bahia Sucia, Puerto Rico, the effects of the remaining oil on the red mangrove trees in the impact area were investigated. This study involved four sampling trips to the spill site and a reference area outside the spill zone between April 1979 and April 1981. The present study was based on the observation that stressed mangrove trees in the heavily oil-affected areas had a similar appearance to trees exhibiting stress due to hypersalinity in unoiled areas. The working hypothesis was that petroleum hydrocarbons induce stress in salt-excluding plants such as red mangroves by disrupting the ability of the roots to exclude ions from seawater. Measurements of sodium (the principal seawater cation) and potassium (a major physiological ion) were made on leaf samples taken from trees from oil-affected areas and reference areas. Sediment core samples were taken from the root zone of the trees sample...