Refining Carbon Sequestration Estimates of Seagrass Meadows in Tampa Bay

As of 2012, there were an estimated 14,243 ha of seagrass meadows in Tampa Bay. Seagrass meadows are the dominant blue carbon habitat in Tampa Bay, compared to the estimated 6,127 ha of mangroves and 1,779 ha of saltmarsh. However, and unlike mangroves and saltmarshes, the entirety of carbon fixation, growth and decay in seagrass meadows occurs in a submerged environment. While rates of primary production in seagrass meadows rank among the highest for any ecosystem on the planet, the organic content of sediments below seagrass meadows is typically much lower than the organic content of soils associated with mangroves and saltmarshes. This paper compares bay-wide estimates of primary production of seagrass meadows in Tampa Bay to estimates of carbon sequestration via sediment burial alone. The much greater rates of primary production found, compared to rates of carbon sequestration via burial, leads to two main conclusions – either sequestration can occur via pathways other than burial alone, or a much smaller percentage of assimilated carbon is sequestered by seagrass meadows, compared to other blue carbon habitats. Based on a combined estimate of both physical and chemical sequestration processes and pathways, the seagrass meadows of Tampa Bay appear to be able to sequester approximately 41,731 Mg C / yr, which approximates the annual carbon output of ca. 32,000 typical cars.