# Impacts of Climate Change on Blue Carbon Stocks and Fluxes in Mangrove Forests
## 1 Introduction  
Mangrove forests occupy the coastal-land interface of subtropical and tropical seas and are ordinarily subjected to harsh environmental conditions that predispose these tidal ecosystems to be resilient to climate or climate-related factors, such as sea-level rise (SLR). Mangroves are naturally well adapted to rapid changes in tides, temperature, salinity, freshwater and sediment inputs, and anoxia. These drivers impose structural and functional constraints and foster adaptation and physiological mechanisms to facilitate subsistence in a harsh saline, low oxygen environment [1; 2]. Mangrove ecosystems are characterized by a rich mixture of marine, estuarine, and semi-terrestrial organisms that form unique food webs and play a plethora of roles in the coastal zone by linking food webs and the flow of energy and inorganic and organic materials and geochemical and biogeochemical cycles from the shoreline to the adjacent coastal ocean.  
Mangroves are the world's most carbon-rich ecosystems to the extent that they are considered to play a role in climate regulation and mitigation by capturing and sequestering large amounts of carbon (mostly in soils) that counterbalance anthropogenic CO\({}_{2}\) emissions [3; 4; 5]. The large amounts of carbon reflect high rates of primary production and rapid rates of soil accretion on the forest floor. Like other forested ecosystems, mangroves exchange gases with the atmosphere but like all coastal wetlands also exchange gases and dissolved and particulate materials with adjacent coastal waters. Tidal connections are complex, with variable concentrations of dissolved organic and inorganic solutes and particulates imported and exported by tides, porewater pumping, and subsurface groundwater advection [6]. Flocculation and sedimentation of fine particles is facilitated by tidal circulatory processes, such as (1) a pronounced asymmetry between ebb and flood tides,(2) friction, flow resistance and drag due to the presence of forest structures, and (3) lateral trapping and gradients due to high evapotranspiration. Several interrelated processes exert control over sediment transport and deposition, including (1) tidal pumping, (2) baroclinic circulation, (3) particle trapping in the turbidity maximum, (4) flocculation, (5) the tidal prism, and (6) microbial production of mucus [6].  
Sedimentation of particles and the long-term accretion of soils in mangroves is often rapid. Over decades, after initial colonization of a mudflat, the forest develops and the forest floor builds up further, adjusting to sea-level, subsidence, and uplift, with the net result being several meters of soil. As the forest matures, these deposits are penetrated further by extensive tree root systems, various flora and fauna, especially burrowing crabs, to the extent that mangrove deposits contribute about 30% to carbon storage on continental margins in low latitudes [7]. This sequestered carbon is now commonly referred to as 'blue carbon', being derived from a marine habitat.  
Similarly, mangroves contribute a disproportionate share of carbon to the coastal ocean, as they occupy only 1.5% of the world's subtropical and tropical coastal area, but account for 5% of net primary production and 12% of ecosystem respiration. These figures illustrate the potential of mangrove reforestation and restoration in ameliorating CO2 emissions in climate mitigation projects. After an update and critical examination of mangrove carbon stocks and pathways, an analysis and forecast will be presented as to the level of significance of mangrove blue carbon storage and cycling at national, regional, and global levels in relation to climate change.