Blue carbon in freshwater / brackish marshes on the Barrier Islands of Virginia: Aboveground net primary productivity and carbon pools
Blue carbon is a relatively new concept describing carbon distributed tidally and sequestered via net production within coastal ecosystems, including sea grass beds, mangrove forests and salt-water marshes. These systems sequester carbon at least 10 times faster than terrestrial systems. Fresh to brackish wetlands that receive irregular tidal influence due to overwash and storm events have not been typically studied as blue carbon systems. My objective was to quantify carbon pools within four interdunal freshwater/brackish marshes on Hog Island, VA to determine their blue carbon potential. Marshes 1 and 2 are farthest from the ocean, below and above a trail berm respectively. Marshes 3 and 4 are closest to the ocean, below and above a trail berm respectively. Marshes 1 and 2 were hypothesized to be more accessible to overwash events than Marshes 3 and 4 and would theoretically have a higher sequestration potential. Aboveground primary production was determined via harvests throughout 2013. Belowground biomass was measured with cores in August. Soil carbon pools were also determined by cores in August. Decomposition was measured with litterbags collected throughout the year. Carbon sequestration potential was calculated as above and belowground litter production remaining after one year of decay plus sediment deposition.
No significant differences in aboveground net primary production were found among marshes (F = 1.116; p = 0.355). Values for aboveground primary production ranged from 156 g C m-2 yr-1 (marsh 3) to 284 g C m-2 yr-1 (marsh 2). Marsh 2 had significantly more belowground biomass than all the other marshes (F = 9.425; p < 0.0005). All marshes exhibited slow exponential decay (k = 0.0007, 0.002, 0.001, 0.001). Soil carbon values were highly variable with marsh 4 storing the most carbon. Carbon sequestration potential ranged from 116.6 g C m-2 yr-1 to 233.4 g C m-2 yr-1. These values do not include carbon exported from the marshes but suggest that carbon could be sequestered at high rates, similar to blue carbon systems.