## 1 Introduction  
Increasing the potential for carbon sequestration by terrestrial and aquatic ecosystems has been proposed as a solution to mitigating increased greenhouse gas (GHG) concentrations in the atmosphere. Many studies have shown that wetlands play a dominant role in the global cycling of carbon as a result of anaerobic substrates and high primary productivity [1; 2]. Approximately 20%-30% of the terrestrial total organic carbon (TOC) storage is in wetland environments [3; 4]. Degradation of wetlands has the potential to reduce terrestrial carbon stores by up to 50% within the first century of disturbance [5]; for long-term storage of carbon, wetlands must be conserved on the landscape. This paper compares rates of carbon sequestration in disturbed and reference mangrove tidal creeks in southern Florida USA and whether that disturbance affects a mangrove ecosystem's ability to mitigate human emissions of greenhouse gases to the atmosphere. We also compare sedimentation rates in these tidal creeks as important indicators of whether mangroves in this region will be able to keep up with projected sea level rise. Coastal wetlands are some of the most biologically and geochemically active regions in the biosphere [6]. They receive allochthonous material from both the terrestrial landscape and the marine environment. Globally, mangrove wetlands occupy 138,000 to 180,000 km\({}^{2}\) of terrestrial/coastal landscape [2; 7; 8; 9; 10], less than 2% of the oceanic surface area [11] and only 5% of wetlands worldwide. Mangrove forests trap suspended particulate material from the water column, accreting allochthonous sediments as well as senesced plant material, burying and sequestering carbon as a result of anoxic conditions that inhibit decomposition [12; 13; 14]. Despite their small spatial extent, mangrove ecosystems cycle and store a potentially large amount of carbon, compared to many freshwater wetlands ecosystems, as a result of their efficient trapping of suspended material by their complex rooting structures [15]. Average carbon burial rates in mangrove ecosystems are estimated to be three to ten times greater than those of northern peatlands [16]. Early estimates of organic carbon burial in mangrove ecosystems suggest they account for 15% of the total organic carbon annually sequestered in marine sediments [17; 18]. Dominant throughout tropical and subtropical regions, mangroves are limited by oceanic currents, the 20 \({}^{\circ}\)C winter isotherms, and frequency of sustained frosts in both the northern and southern hemispheres [7; 19; 20]. There is some evidence that their extent is moving poleward [21; 22]. Due to their larger global extent, research on carbon sequestration has focused on northern boreal peatlands and some temperate wetlands [1; 23]. Data on the contribution of subtropical and tropical mangrove wetlands to the global carbon budget are limited [11; 13; 24; 25]. Although soil carbon stocks in boreal regions are high, the rates of carbon accumulation are quite low [1]. Compared to northern peatlands, which sequester carbon at rates of 29 \(\pm\) 13 g-C m\({}^{-2}\). year\({}^{-1}\)[1], mangrove ecosystems have been estimated to sequester, on average, 174 g-C m\({}^{-2}\). year\({}^{-1}\)[9]. The term \"blue carbon\" has been used to focus on carbon sequestration in coastal wetlands, including seagrass beds, salt marshes, and mangrove ecosystems [14; 15]. Although research has largely ignored coastal wetlands in global inventories of carbon fluxes until recently [15], the past forty years have shown significant scientific advancements in the understanding and quantification of carbon dynamics within mangrove ecosystems. The practice of mangrove carbon quantification has grown significantly since [PERSON] [26] first theorized the outwelling hypothesis to current studies that require decadal-scale meta-analysis of organic matter burial, standing carbon pools and gross sedimentation rates [11; 12; 17; 18; 27; 28; 29].