VARIABILITY IN DISSOLVED ORGANIC MATTER ACROSS SOURCES WITHIN FORESTED WETLANDS OF THE SOUTHEASTERN COASTAL PLAIN

Forested wetlands as headwaters for organic-rich ‘blackwater’ rivers. The sources of carbon in these areas generating the intense blackwater color are poorly resolved. A study conducted from May to late July 2024 examined the optical characteristics (absorbance) and DOC content of throughfall, surface water, groundwater, and soil leachate of wetlands on Hobcaw Barony (South Carolina Coastline). To highlight DOC differences between forests, 4 sites were chosen: two upland forests, one dominated by long-leaf pine (Pinus palustris) and the other by laurel oak (Quercus laurifolia), and two forested wetlands, one dominated by swamp cypress (Taxodium distichum) and the other by swamp tupelo (Nyssa biflora). DOC concentration and variability of throughfall was considerable (2-45 mg/L), but there was no significant DOC concentration difference in throughfall between tree species. Surface and groundwater were enriched with DOC (avg 24 mg/L and 74 mg/L, respectively), were variable over time and significantly different between sites. This suggests seasonality and unresolved mechanisms controlling DOC concentration between forest sites. Carbon-specific absorbance values (SUVA₂₅₄) of surface water (avg 10.3) were significantly higher than throughfall (avg 4.4), groundwater (avg 5.8), and soil leachate (avg 4.5), indicating processes alter the source’s DOC characteristic once it enters surface water. Results suggest forested wetlands contribute large volumes of colored carbon to the watershed, and further testing should examine degradation mechanisms altering carbon sources properties.

Presentation Preference: Either

Primary Presenter: Cameron Stacey, Texas A&M University (cameron.a.stacey@gmail.com)

Authors:

Cameron Stacey, Texas A&M University  (cameron.a.stacey@gmail.com)

Erik Smith, University of South Carolina  (erik@baruch.sc.edu)