CARBON ISOTOPIC COMPOSITION OF LEAF WAX n-ALKANES OF MANGROVE PLANTS DISTRIBUTED ALONG A LATITUDINAL GRADIENT IN BRAZIL

Summary Here we present baseline data of δ¹³C of n-alkanes (δ¹³Cn-alkanes) from leaf waxes of mangrove trees – Avicennia schaueriana, Rhizophora mangle and Laguncularia racemosa – distributed along a latitudinal gradient in Brazil. The objective was to evaluate the influence of trees physiology, local hydrology and climatic factors upon the molecular and isotopic signature of the leaf wax n-alkanes. Higher weighted average δ¹³Cn-alkanes (δ¹³CWA), average chain lenght (ACL25-35) and carbon preference index (CPI24-36) for R. mangle and A. schaueriana contrasting with lower values for L. racemosa seem to be linked to physiological characteristics of each species regarding intrinsic water use efficiency under the specific tidal flooding regime of mangrove forests. About the plant’s response to local environment influence, inverse correlations between all δ¹³Cn-alkanes values (δ¹³C₂₇, δ¹³C₂₉, δ¹³C₃₁, δ¹³C₃₃ and δ¹³CWA) and mean annual precipitation were found for the A. schaueriana samples. For the R. mangle species, a relationship between ACL25-35 and mean annual potential evapotranspiration and between CPI24-36 and mean annual temperature were observed. The different molecular and isotopic footprints of the three mangrove species presented here have potential to be used in future interpretations of n-alkanes as biomarkers in biogeochemical and paleoclimate studies near mangrove-dominated coastal regions.