Compound specific δD and δ13C analyses as a tool for the assessment of hydrological change in a subtropical wetland

Authors

Ding He, Southeast Environmental Research Center and Departmet of Chemistry and Geochemistry, Florida International UniversityFollow
William T. Anderson, Southeast Environmental Research Center and Earth Sciences Department, Florida International UniversityFollow
Rudolf Jaffe, Southeast Environmental Research Center and Department of Chemistry and Biochemistry, Florida International UniversityFollow

Abstract

Compound specific carbon and deuterium stable isotope values (δ¹³C and δD) and the relative abundance of mid-chain n-alkanes (Paq) were determined for a series of dominant wetland plants, a surface slough-to-ridge soil transect, and slough and ridge soil cores, to assess historical vegetation successions induced by hydrological modification in an anthropogenically impacted, subtropical wetland, the Florida Everglades, USA. A difference of as much as 3.6 and 130 ‰ in their δ¹³C and δD values was observed between the two most abundant emergent macrophyte species (Cladium and Eleocharis), respectively. A clear n-alkane δD value depletion (−130 to −167 ‰) and decreasing Paq was observed along the slough-to-ridge soil transect, likely the result of an eco-hydrological transition from slough-to-ridge dominated vegetation (Eleocharis to Cladium). In agreement with the relatively constant Paq values, the lack of significant changes in the δD depth profile for the slough core, suggest a consistent slough type of vegetation composition over time at that location. In contrast, changes of both n-alkane δ¹³C and δD values for the ridge core, especially after ~1960 AD, coincide with the expected plant successions from historically long hydroperiod (>8 months), slough type plants (Eleocharis, Utricularia, Nymphaea) to present day, shorter hydroperiod (<8 months), ridge type plants (Cladium). These δ¹³C and δD changes seem to be driven by vegetation shifts associated with hydrological change. The application of the compound-specific stable isotope determinations may strongly complement the biomarker approach for paleo-hydrological assessments in wetland ecosystems.

Comments

DOI: 10.1007/s00027-016-0473-4

This material is based upon work supported by the National Science Foundation through the Florida Coastal Everglades Long-Term Ecological Research program under Cooperative Agreements #DEB-1237517, #DBI-0620409, and #DEB-9910514. Any opinions, findings, conclusions, or recommendations expressed in the material are those of the author(s) and do not necessarily reflect the views of the National Science Foundation.

Recommended Citation

He, D., Anderson, W.T. & Jaffé, R. Aquat Sci (2016) 78: 809. doi:10.1007/s00027-016-0473-4