Carbon isotopic composition of leaf wax n-alkanes in mangrove plants along a latitudinal gradient in Brazil

The carbon isotopic composition (delta C-13) of selected specific biomarkers provides important information on the relationship between plant species and the environment in which they developed. Here we present baseline data of delta C-13 values of individual n-alkanes (delta C-13(n-alkanes)) from leaf waxes of mangrove species - Avicennia spp., Rhizophora mangle and Laguncularia racemosa - typical of mangrove forests collected from equatorial to subtropical regions in Brazil. The objective was to evaluate the influence of tree physiology, local hydrology and climatic factors upon the molecular and isotopic signature of the leaf wax n-alkanes. Total n-alkanes concentration, average chain length (ACL2(5-35)) and carbon preference index (CPI24-36) are higher for Avicennia spp. contrasting with the lower values found for R. mangle and L. racemosa. This seems to derive from the physiological characteristics of each species with respect to the intrinsic water use efficiency under the specific tidal flooding regime of mangrove forests. For Avicennia spp. inverse correlations between delta C-13(n-alkanes) values (delta C-13(27), delta C-13(29), delta C-13(31), delta C-13(33) and delta C-13(WA)) and mean annual precipitation suggests plant response to local environmental conditions. For R. mangle species, relationships between ACL(25-35) and mean annual potential evapotranspiration, and between CPI24-36 and mean annual temperature were observed. These results indicate that delta C-13(n-alkanes) values in Avicennia spp. as well as ACL(25-3)5 and CPI24-36 in R. mangle may be useful in tracing environmental changes and, as long as preservation of reliable record in sediments is verified, may also be applied in the reconstruction of past environmental conditions. The different molecular and isotopic footprints of the mangrove species presented here have potential in future interpretations of n-alkanes as biomarkers in biogeochemical studies in mangrove-dominated coastal regions.

Automated summary

This study analyzed the baseline data of delta C-13 values of leaf wax n-alkanes from mangrove species in Brazil, revealing the physiological characteristics and environmental responses of Avicennia spp. and Rhizophora mangle. The differences in molecular and isotopic signatures of the mangrove species could potentially be used in tracing environmental changes and reconstructing past environmental conditions in biogeochemical studies in mangrove-dominated coastal regions.