A quantitative and qualitative comparison of aquatic and terrestrial plant lignin phenols: Critical information for paleoecological reconstructions
Abstract
Currently, lignin phenols are used in marine and lacustrine ecosystems as proxies for terrestrial vegetation inputs. Lignins are found in all vascular plants, where they play a crucial role in conduction of water, nutrients and photosynthates through the vascular system, and where they provide structural support. Furthermore, different types of lignin phenols are found in specific types of vegetation (e.g., both syringyl and vanillyl phenols are in angiosperm wood, but only vanillyl phenols are in gymnosperm wood). The ratio of lignin phenols (e.g. syringyl:vanillyl) is indicative of the type of plant from which the lignin phenols were derived. Studies that examine lignin phenols in sedimentary archives assume that lignin phenols are derived solely from terrestrial plants, and changes in the types of lignin phenols are therefore assumed to mark changes in terrestrial vegetation. These assumptions may be flawed, however, because many aquatic plants, including those that are submerged, are vascular, yet little is known about the type and concentration of lignin phenols present in aquatic vascular plants. This knowledge is imperative to the success of paleoecological studies that utilize lignin phenols as a geochemical proxy for terrestrial vegetation. Furthermore, lignin phenols may be important targets for compound-specific radiocarbon dating, which is useful when suitable macrofossils are unavailable. Knowing the origin of the molecules used for radiocarbon dating, however, (i.e. whether they are terrestrial or aquatic) is critical to obtaining meaningful chronologies. We isolated and analyzed lignin phenol monomers from different types of aquatic vascular plants. All plants analyzed are angiosperms, but they occupy different niches in aquatic plant communities: floating, emergent and submergent. We also analyzed different parts of aquatic plants (i.e., stems and leaves). We found lignin phenols in all aquatic species that we analyzed, which highlights the need for caution when using lignin phenols in sedimentary archives to reconstruct changes in terrestrial vegetation. We determined the types of lignin phenols in each plant sample and compare the lignin phenol ratios in our samples to the database of lignin phenol ratios for terrestrial plants, with the goal of identifying characteristic differences between terrestrial and aquatic lignin phenols. This is the first report of the lignin phenol composition of freshwater aquatic plants, and is important information for studies that utilize lignin phenols to reconstruct ecological conditions.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2009
- Bibcode:
- 2009AGUFM.B33C0404T
- Keywords:
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- 0473 BIOGEOSCIENCES / Paleoclimatology and paleoceanography;
- 1055 GEOCHEMISTRY / Organic and biogenic geochemistry