## 5 Carbon Flow through the World's Mangrove Ecosystems and Contributions to the Coastal Ocean  
Until the availability of the empirical data referenced in Tables 1 and 2 indicating supersaturated conditions in adjacent mangrove waters, large subsurface pools of interstitial DIC and DOC implied that large amounts of dissolved carbon might be exported from the forest, possibly accounting for as much as 112-160 Tg a\({}^{-1}\) of mangrove carbon to balance the budgets constructed by [PERSON] et al. [104] (as revised by [PERSON] et al. [105]) and [PERSON] [2,10]. This discrepancy was called the \"missing carbon\". Without empirical data, [PERSON] [2] estimated DOC and DIC export by difference, resulting in estimates of 15 Tg a\({}^{-1}\) and 86 Tg a\({}^{-1}\) for DOC and DIC, respectively. Here, the mass balance model of carbon flow through the world's mangrove ecosystems constructed by [PERSON] [2] is revised, using the data in Sections 2.1-2.3 and in Table 2, and newer data for soil + root burial [3, 106], root production [107], mangrove gross primary production (GPP), POC, and DOC export [7, 10], and canopy respiration (R\({}_{\rm c}\)) [19, 66, 108, 109, 110, 111, 112, 113, 114], and extrapolated using the most recent estimate of global mangrove area [115]. The revised carbon flow model (Figure 5) shows that \(\sim\)64% of GPP is respired by the canopy with NPP vested nearly equally in the litter, wood, and belowground root production. About 41% of litter production is exported to adjacent tidal waters, and as estimated by difference, about 40% is buried and 44% incorporated and eventually decomposed in the massive soil C\({}_{\rm ORG}\) pool (5396 Tg). C\({}_{\rm ORG}\) burial (14 Tg C a\({}^{-1}\)) equates to about 12% of NPP. Of the combined total carbon mineralization (subsurface DIC production + CO\({}_{2}\) respiration at the soil surface), 25% is released at the forest floor surface in a separate process, and approximately all subsurface DIC production is exported to adjacent tidal waters in the form of DOC (\(\sim\)30%), dissolved CH\({}_{4}\) (\(<\)0.2%) and DIC (\(\sim\)70%). A considerable, but unquantified, amount of exported DIC, DOC, and CH\({}_{4}\) is derived from groundwater derived from adjacent upland [74, 75, 76, 77, 94, 103, 13, 74, 13], so it is unclear exactly how much dissolved carbon exported from mangroves is derived from soil mineralization. \begin{table}
\begin{tabular}{c c c c c c} \hline \hline
**Location** & **DIC Export** & **Alkalinity Export** & **DOC Export** & **CH\({}_{4}\) Export** & **Reference** \\ \hline Can Gio, Saigon River, southern Vietnam & \(351.6\pm 33.9\) & & \(20.6\pm 1.9\) & & \\  & \(480.0\pm 35.6\) & & \(31.0\pm 2.3\) & & \\ Can Gio, Saigon River, southern Vietnam & \(677.7\pm 79.0\) & ND & \(67.7\pm 7.9\) & ND & [98] \\  & \(612.2\pm 71.4\) & & \(60.0\pm 3.7\) & & \\  & \(338.9\pm 39.5\) & & & & \\ \hline Six mangrove estuaries, north, northeast, and southeast & \(85\) & \(116\) & & & \\  & \(22\) & \(21\) & \(7.5\pm 0.2\) & & \\  & \(-97\) & \(81\) & \(3.3\pm 0.4\) & & \\  & \(83\) & \(12\) & \(5.1\pm 0.5\) & & \\  & \(77\) & \(116\) & \(4.2\pm 0.2\) & & \\ Australia & \(-3\) & \(-1\) & & & \\ \hline Badeldaob Island, Palau & \(79\pm 28\) & \(48\pm 17\) & \(35\pm 12\) & ND & [100] \\  & \(10\pm 4\) & \(2\pm 1\) & \(8\pm 3\) & ND & [100] \\ \hline Indian Sundarbans & 202.3 & ND & \(162.1\) & ND & [101] \\ \hline Korogoro Creek, New South Wales, Australia & 687 & 23 & \(294.8\) & ND & [102] \\ \hline Harney and Shark Rivers, Florida Everglades & \(574.5\) & ND & ND & ND & [103] \\ \hline Mean \(\pm\) 1 SE & \(339.6\pm 51.5\) & \(211.5\pm 58.2\) & \(229.1\pm 78\) & \(0.66\pm 0.29\) & \\ \hline \hline \end{tabular}
\end{table} 
Table 2: _Cont._The supersaturation of mangrovewaters leads to significant CO\({}_{2}\) (40 Tg C a\({}^{-1}\)) and CH\({}_{4}\) (0.19 Tg C a\({}^{-1}\)) release to the atmosphere. The rates of soil mineralization imply that the turnover time of the entire soil CORG pool is on the order of 25 years.