Sedimentary Organic Matter Dynamics at a High-Energy Beach

Sandy sediments play a significant role in global biogeochemical processes, due to their preponderance and rapid elemental cycling. The historical assumption that little occurs in sand due to low organic matter content was challenged when it was shown that this is due to high turnover rates of organic matter driven by enhanced exchange with the water column. This study aims to inform our understanding of organic matter variation down the sediment column and through the seasons at a high-energy beach in South Carolina, by using mass loss-on-ignition (LOI) as an organic matter proxy. The measured LOI values (0.20-1.19 %) from February 2017-May 2018 reflect the low concentrations commonly associated with sandy sediments. Depth profiles exhibit increasing organic carbon concentrations with depth, as seen in other temperate-latitude sand column studies and unlike the expected decrease-with-depth pattern. Seasonal patterns reflect productivity cycles with organic matter peaks in spring and summer, as expected.