GO-SHIP Repeat Hydrography: Determination of dissolved organic carbon (DOC) and total dissolved nitrogen (TDN) in seawater using High Temperature Combustion Analysis.[GOOS ENDORSED PRACTICE]

Abstract

Dissolved organic matter (DOM), operationally defined as organic matter that passes through a submicron filter, is a complex mixture of organic molecules comprised of carbon, hydrogen and oxygen as well as nitrogen, phosphorous and sulfur. Resolving the dynamics of each DOM fraction helps to elucidate the greater questions of DOM biogeochemical cycling. At ~662 ±32 Pg (1015 g) C, oceanic dissolved organic carbon (DOC) is one of the largest bioreactive pools of carbon in the ocean (Williams and Druffel, 1987; Hansell and Carlson, 1998a; Hansell et al., 2009), and is comparable to the mass of inorganic C in the atmosphere (MacKenzie, 1981; Eppley et al., 1987; Fasham et al., 2001). Perturbations in the sources or sinks of the oceanic DOC pool impact the balance between oceanic and atmospheric CO2, perhaps making it climatically significant (Ridgwell and Arnt, 2014). In addition, most of the standing stock of fixed nitrogen in the surface ocean (<200m) is in the form of dissolved organic nitrogen (DON) (Bronk, 2002; Aluwihare and Meador, 2008; Letscher et al., 2013). As such, it is important to understand the processes that control DOC and DON distribution, inventories and fluxes in the global ocean.