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| Submitter's Name |
Savanna Barry |
| Session Name |
Poster Session - Climate Change/Hydrology |
| Poster Number |
17 |
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| Author(s) |
Savanna Barry, UF IFAS Nature Coast Biological Station (Presenting Author) |
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Thomas Bianchi,
University of Florida, Department of Geological Sciences |
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Michael Shields, University of Florida, Department of Geological Sciences |
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Jack Hutchings, University of Florida, Department of Geological Sciences |
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Charles Jacoby AND Thomas Frazer, University of Florida, Soil and Water Science Department AND University of Florida, School of Natural Resources and Environment |
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Characterizing blue carbon stocks in Thalassia testudinum meadows subjected to different long-term phosphorus supplies: a lignin biomarker approach |
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Seagrass meadows represent globally important stores of carbon. However, environmental heterogeneity in shallow, estuarine environments may shape the quantity, composition, and post-depositional processing of organic carbon stocks (Corg) in these meadows. Along a persistent gradient in total phosphorus concentrations in the water column and a parallel gradient in seagrass morphology, we measured traditional bulk carbon parameters (Corg stocks, bulk density, %Corg, Corg:N, and δ13C) and lignin biomarkers in live and dead tissue of Thalassia testudinum and in the sediments beneath the seagrass meadows. We found that Corg stocks and sources differed among systems, but consistent patterns related to extant standing stocks of seagrass and historical nutrient concentrations were not evident in sedimentary Corg. We estimated that seagrasses contributed 44–73% of the total sedimentary Corg throughout the region, with the remainder derived from allochthonous sources (e.g., phytoplankton, marsh grasses, and mangroves). The system with intermediate phosphorus concentrations and seagrass standing stock had more Corg overall, more Corg from phytoplankton, and sediments with lower bulk density, which suggested hydrodynamics played a key role in determining stocks. Phenolic acid-to-aldehyde ratios were high in fresh T. testudinum tissues, and lower values in the sediments indicated extensive leaching of acidic lignin phenols. After this initial decay and selective leaching, most of the lignin deposited in the upper layers of sediment was retained in the T. testudinum meadows, but detailed identification of sources and degradation pathways for lignins will require new indices designed for submerged estuarine sediments. |
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