1-Chloro-n-alkanes: potential mangrove and saltmarsh vegetation biomarkers

Chlorinated hydrocarbons with biological sources occur in high abundance and diversity in living organisms as well as in sedimentary environments. Although some of these compounds are potentially highly source-specific and sufficiently degradation-resistant, their capacity as sedimentary biomarkers remains under-investigated. Distinct series of long-chain 1-chloro-n-alkanes have previously been reported in three species of European saltmarsh vegetation; however, these compounds have never been further investigated in a more diverse plant population. Here we report the presence of similar series with a typical higher plant odd/even carbon number predominance in species of Australian mangrove and saltmarsh vegetation, including the black mangrove Lumnitzera racemosa, the grass Sporobolus virginicus and samphire, supporting the potential use of long-chain 1-chloro-n-alkanes as halophyte biomarkers. Based on carbon stable isotope values, which were reported here for the first time, and similarities in their distributions, we propose that the biosynthetic pathway of chloroalkanes is linked to that of other n-alkyl plant wax components.