The Bioavailability of Seasonally Accumulated Dissolved Organic Carbon and Its Contribution to Export in the Western North Atlantic

Abstract

Phytoplankton blooms are major sources of net community production (NCP) in the Western North Atlantic and represent important sinks for atmospheric CO2, influencing the balance of carbon between the ocean and atmosphere. The organic matter produced by these blooms are subject to a variety of food web processes that dictate the partitioning of organic carbon into the particulate and dissolved phases. Some of the dissolved organic matter (DOM) is used to fuel instantaneous bacterial carbon demand (BCD) for biomass production and respiration. The DOM that resists or escapes rapid bacterioplankton utilization can accumulate, of which a fraction can persist. This persistent DOM is subject to being exported to depths below the sunlit ocean due to winter convective mixing and thus, can represent an important export pathway for carbon produced by phytoplankton blooms. This dissertation seeks to clarify the magnitude and divers of surface DOC accumulation over the course of the annual phytoplankton bloom in the Western North Atlantic, the contribution of DOC to annual vertical carbon export (aka biological carbon pump) via deep convective overturn, and the fate of surface accumulated DOC following physical export.