Determination of particulate organic carbon (POC) in seawater: The relative methodological importance of artificial gains and losses in two glass-fiber-filter-based techniques

Transparent exopolymer particles (TEP) in the deep ocean: full-depth distribution patterns and contribution to the organic carbon pool

“…The filters were kept frozen (−20°C) until analysis in the onshore laboratory. The filters were fumed overnight with HCl using the vapor method (Yamamuro & Kayanne 1995, Turnewitsch et al 2007 to remove carbonates and then dried at 60°C for 24 h. POC was quantified with an elemental analyzer (N A-1500; Fisons Instruments), using acetanilide (Thermo Electron) as a standard. The same pre-combusted (450°C for 4 h) GF/F were used for the measurement of the filter blanks.…”

The ocean carbon sink – impacts, vulnerabilities and challenges

“…Future CO 2 emission scenarios to drive climate models have been produced on empirical evidence concerning human behaviour and economics. In view of the on-going high-energy use in wealthy nations and the accelerating energy production in emerging economies (especially China and India; see Raupach et al, 2007), current and recent annual CO 2 emission rates are at the levels of the most pessimistic emission scenario as pro-C. Heinze et al: The ocean carbon sink -impacts, vulnerabilities and challenges 329 duced a few years ago for the climate projections of the Fifth Assessment Report of the IPCC (RCP scenarios;van Vuuren et al, 2011a, b;Peters et al, 2013). Considering the key role of the oceans in the global carbon budget it is therefore fundamental to broaden our knowledge on their past, present and future quantitative impact in regulating atmospheric CO 2 concentrations.…”

“…About 25 % of the particulate organic carbon (POC), which is produced in the ocean surface layer, eventually sinks through the water column (Schlitzer, 2000) with most of it being remineralized and returned to the dissolved phase already within the upper 1500 m. Normally, less than 1 % of POC reaches the open-ocean seafloor by sedimentation . In addition to POC, marine biota also produce dissolved organic carbon (DOC), which is discriminated from POC based on particle size (Turnewitsch et al, 2007). As increasingly small particles do not sink anymore through the water column but become suspended due to the increasing importance of friction for small particles, DOC is transported through the oceans like DIC as a passive tracer.…”

“…Quantification of the regional as well as global land carbon sink is associated with high uncertainties due to the direct coupling of CO 2 consumption and release on the land surface with the atmosphere in combination with the heterogeneity of the land biosphere, its constant change and different forms of land use including forestry changes. Complex soil processes like the degradation of organic material and permafrost melting processes (Schuur et al, 2009), episodic events such as fires (wild fires, peat fires; Schultz et al, 2008;van der Werf et al, 2008), and the multitude of possible reactions of land plants to different drivers (Kattge et al, 2011) make the determination of the land carbon sink difficult. Recent studies indicate that it may have been overestimated as the limiting effect of nitrogen (N) on plant growth has not yet been accounted for in most models, potentially giving too much value to the CO 2 fertilization effect, while on the other hand human-caused additions of nitrogen to the Earth system regionally enhance plant growth (Zaehle and Dalmonech, 2011).…”

“…the particle sinking velocity) can be calibrated. Datadriven diagnostic models (Usbeck et al, 2003) are important for suggesting first-order values of free parameters in dynamical process descriptions and can be implemented in complex forward models, which can be used for predictions as well. Systematic model assessment with observations and model optimization with data assimilation have made progress in recent years, but for integrated biogeochemical cycle simulations these approaches need to be extended.…”