High productivity of benthic macroalgae, Colpomenia, on the Bahamas Banks and potential carbon export to the deep sea
Heidi
M
Dierssen, Univ. Connecticut, heidi.dierssen@uconn.edu
(Presenting)
Lisa
A
Drake, Old Dominion Univ., lisa.drake1@verizon.net
Richard
C
Zimmerman, Old Dominion Univ., rzimmerm@odu.edu
David
J
Burdige, Old Dominion Univ., dburdige@odu.edu
Much of the past research on the fate of carbon in the world’s oceans has focused on the vast open ocean regions and export of phytoplankton-associated biomass to the deep seafloor. Little attention has been paid to the contribution of continental margins, including the highly productive shallow water banks and bays, to the carbon cycle. These coastal regions, while covering less area than the open ocean, contribute disproportionately in terms of their productivity, elemental fluxes and biogeochemical cycles. Moroever, the fate of carbon produced in shallow water systems and the amount transported to the deep sea is difficult to constrain and is not considered in current biogeochemical models. The Bahamas Banks influences the carbon cycle through drawdown of carbon dioxide due to benthic productivity, release of colored dissolved organic matter onto the banks and the surrounding deep sea, carbonate production and accumulation, and biologically-mediated carbonate dissolution. This study uses remote sensing imagery to address the fate of carbon produced on the banks as ephemeral negatively buoyant benthic macroalgae. The amount of photosynthetic benthic algae on the Bahamas Banks has not been enumerated and the fate of this productivity is virtually unknown, but our results show productivity associated with Colpomenia rivals some of the most productive ecosystems including agricultural fields, tropical rainforests, great kelp forests, and seagrass meadows in which gross primary production typically exceeds 1 kg C m-2 y-1. The fate of this productivity is unknown, however, MODIS imagery suggests that much of this macroalgae may be transported off the Banks and onto the deep seafloor (>1000 m). Episodic export of this carbon may occur through lateral transport from Langmuir circulation and single export episodes may represent 0.5% of daily carbon export productivity in the global ocean.
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