Tidal Wetland Gross Primary Production Across the Continental United States, 2000-2019

We mapped tidal wetland gross primary production (GPP) with unprecedented detail for multiple wetland types across the continental United States (CONUS) at 16-day intervals for the years 2000-2019. To accomplish this task, we developed the spatially explicit Blue Carbon (BC) model, which combined tidal wetland cover and field-based eddy covariance tower data into a single Bayesian framework, and used a super computer network and remote sensing imagery (Moderate Resolution Imaging Spectroradiometer Enhanced Vegetation Index). We found a strong fit between the BC model and eddy covariance data from 10 different towers (r(2) = 0.83, p < 0.001, root-mean-square error = 1.22 g C/m(2)/day, average error was 7% with a mean bias of nearly zero). When compared with NASA's MOD17 GPP product, which uses a generalized terrestrial algorithm, the BC model reduced error by approximately half (MOD17 had r(2) = 0.45, p < 0.001, root-mean-square error of 3.38 g C/m(2)/day, average error of 15%). The BC model also included mixed pixels in areas not covered by MOD17, which comprised approximately 16.8% of CONUS tidal wetland GPP. Results showed that across CONUS between 2000 and 2019, the average daily GPP per m(2) was 4.32 +/- 2.45 g C/m(2)/day. The total annual GPP for the CONUS was 39.65 +/- 0.89 Tg C/year. GPP for the Gulf Coast was nearly double that of the Atlantic and Pacific Coasts combined. Louisiana alone accounted for 15.78 +/- 0.75 Tg C/year, with its Atchafalaya/Vermillion Bay basin at 4.72 +/- 0.14 Tg C/year. The BC model provides a robust platform for integrating data from disparate sources and exploring regional trends in GPP across tidal wetlands.