Respiration of new and old carbon in the surface ocean: Implications for estimates of global oceanic gross primary productivity

Abstract

New respiration (Rnew, of freshly fixated carbon) and old respiration (Rold, of storage carbon) were estimated for different regions of the global surface ocean using published data on simultaneous measurements of the following: (1) primary productivity using 14C (14PP); (2) gross primary productivity (GPP) based on 18O or O2; and (3) net community productivity (NCP) using O2. The ratio Rnew/GPP in 24 h incubations was typically between 0.1 and 0.3 regardless of depth and geographical area, demonstrating that values were almost constant regardless of large variations in temperature (0 to 27°C), irradiance (surface to ~100 m deep), nutrients (nutrient‐rich and nutrient‐poor waters), and community composition (diatoms, flagellates, etc,). As such, between 10 and 30% of primary production in the surface ocean is respired in less than 24 h, and most respiration (between 55 and 75%) was of older carbon. Rnew was most likely associated with autotrophs, with minor contribution from heterotrophic bacteria. Patterns were less clear for Rold. Short 14C incubations are less affected by respiratory losses. Global oceanic GPP is estimated to be between 70 and 145 Gt C yr−1.

Strong Influence of Baseline Respiration in an Oligotrophic Coastal Ecosystem

“…The average of the two recommended approaches resulted in an annual contribution of R bl to R p of approximately 40%, indicating that R bl is an important contributor to R p in this sub-arctic estuary ( Table 3). This is in line with the results of Carvalho et al (2017), who estimated that 55% of R p in oceanic surface waters was driven by carbon older than 24 h (i.e., corresponding to R bl ).…”

“…We can currently not identify a plausible mechanism that could cause an overestimation of the respiration estimates. The R p rates observed were well within the range (0.6-225 mmol m −3 d −1 ) of published rates (e.g., Sherr and Sherr, 1996;Smith and Kemp, 2003;Preen and Kirchman, 2004;Apple et al, 2006;Caffrey et al, 2014;Carvalho et al, 2017). Wikner et al (2013) further successfully validate the optode FIGURE 5 | Conceptual figure depicting management of plankton respiration (R p ) indirectly through nutrient reductions (NR) affecting the level of primary production (PP).…”

“…Winter was the period between November to March, spring between April to May, summer between June to August and autumn the period between September to October. To apply the R bl concept, we defined contemporary primary production as PhP measured on the same day as R p , a similar time scale as used by Carvalho et al (2017). The R bl rate was estimated by using different approaches to determine when PhP was negligible (i.e., below the detection limit), and thus, R p ≈ R bl according to the definition by del Giorgio and .…”

Potential overestimation of community respiration in the western Pacific boundary ocean: What causes the putative net heterotrophy in oligotrophic systems?

“…For phytoplankton respiration, Carvalho et al () reported that the global new respiration (which is mainly contributed by phytoplankton) ranges from 10% to 30% of GPP and that the remainder of the respiration (namely, old respiration) is contributed by other groups, including phytoplankton. If phytoplankton account for part of the old respiration as well, the corresponding ratio of phytoplankton respiration to GPP would be similar to the published ratio (−35%) (Duarte and Cebrián ).…”

Contribution of Biological Effects to the Carbon Sources/Sinks and the Trophic Status of the Ecosystem in the Changjiang (Yangtze) River Estuary Plume in Summer as Indicated by Net Ecosystem Production Variations

“…The difference between gross primary production (GPP) and respiration (R) in an ecosystem is defined as the net ecosystem production (NEP) [8]. Negative NEP indicates that the ecosystem is heterotrophic, and positive NEP indicates that it is autotrophic; therefore, NEP can be used as an indicator of the trophic status, which is an important factor in the assessment of a specific ecosystem [9,10]. For example, Li [11] estimated the nutrient flux, primary production, and NEP in the Changjiang River estuary in the four seasons using the budget box model.…”