Assessing Bulk Carbon and Biomarkers in Two Contrasting Bays: Blackwater River-Dominated and Particle-Dominated

Very few studies of dissolved organic matter (DOM) in coastal wetlands have been conducted. Consequently, these have been inadequately incorporated into coastal carbon budgets. Due to shifts in DOM transport from modifications in land-use and climate change, it is important differentiate between riverine and wetland sources of DOM in coastal areas. Here we investigate DOM cycling in two different bays in the Gulf of Mexico, Apalachicola Bay, FL and Barataria Bay, LA. Dissolved organic carbon (DOC), particulate organic carbon (POC), particulate nitrogen (PN), δ¹³C-POC, lignin phenols and amino acids were measured along with optical characteristics (presented elsewhere). DOC concentrations in Apalachicola and Barataria bays ranged from 181.8 to 1564.2 µM (x̅=477.2±84.2, n=21) and 213.3 to 653.1 µM (x̅=444.0±25.3, n=25), respectively. POC concentrations in Apalachicola and Barataria bays ranged from were 15.3 to 142.4 µM (x̅=62.8±8.8) and 108.3 to 357.5 µM (x̅=253.8±14.9), respectively. δ¹³C-POC values were more depleted in Apalachicola Bay (x̅-27.3‰±0.4) compared to those at Barataria Bay (x̅=-24.8‰±0.2), and C : N values were higher at Apalachicola Bay (x̅=11.6±0.5) than at Barataria Bay (x̅=7.7±0.2). The latter two parameters and lignin phenols indicated a more terrestrial source of particulate organic matter and DOM at Apalachicola Bay reflecting the importance of fluvial DOM inputs in this system. DOM bulk carbon and biomarker analyses from these two contrasting bays, blackwater river-dominated and particle-dominated, will give insight into DOM sources and sinks across the gradient of coastal wetlands and shelf waters.