Decoupling of primary production and community respiration in the ocean: implications for regional carbon studies

Abstract

Primary production (P) and community respiration (R) were measured in vitro along 2 transects of a trans-oceanic section crossing the oligotrophic North Atlantic waters, and during a drifter experiment in the eutrophic waters of the Northwest Africa upwelling system. Our results indicate that the scales of variability of P and R are different, R being less variable than P in the 2 studies. In the first transect of the oceanic study, the mean P:R ratio was <1 (0.8), while in the second transect it was >1 (1.1), the difference being statistically significant. The cause was a significant increase in P in the second transect, which was decoupled from changes in chlorophyll a (chl a) or R. In upwelling waters, however, R was always significantly lower than P (P:R > 1), and enhancements in P were paralleled by increases in chl a but not in R. The close correlation between the P:R ratio and P (and the lack of correlation between P:R and R) supports the view that changes in P but not in R control the transition of the system from net heterotrophy to net autotrophy (in our study at P > 56 mmol C m -2 d -1 ). The observed decoupling between P and R at temporal scales of days to weeks, has strong implications for addressing metabolic balances from in vitro experiments carried out during limited field samplings. We conclude that unless the scales of variability are established for the 2 metabolic rates, and particularly for P, it will not be feasible to accurately establish regional metabolic balances at seasonal to annual scales.

Size-fractionated primary production, bacterial production and net community production in subtropical and tropical domains of the oligotrophic NE Atlantic in autumn

“…As previously reported , Arístegui & Harrison 2002, variability in integrated GPP was much higher than in CR (6-versus 2-fold). Given that bacterial biomass was clearly less than that of autotrophs in the photic layer, a balanced or even net autotrophic balance would have been expected according to trophic distribution models (Gasol et al 1997).…”

“…Resale or republication not permitted without written consent of the publisher (Fernández & Pingree 1996, Arístegui & Harrison 2002.…”

Autotrophic and heterotrophic microbial plankton biomass in the NW Iberian upwelling: seasonal assessment of metabolic balance

“…Similar threshold values of GPP have been reported for other coastal upwelling systems (Duarte et al 2001) and other coastal areas around the world (Duarte et al 2004, Duarte & Regaudie-deGioux 2009) in general, but it is considerably higher than the values reported for the oligotrophic ocean (Arístegui & Harrison 2002, McAndrew et al 2008, Duarte & Regaudie-de-Gioux 2009.…”

“…Considering the whole sampling period, the model outcome indicates that the metabolic balance of nano-and microplankton exhibited higher variability than the metabolic balance of picoplankton. This circumstance leads us to conclude that fluctuations in autotrophic biomass, mainly diatoms and nanoflagellates, and the consequent changes in primary production control the transition from net heterotrophy to net autotrophy (Duarte et al 2001, Arístegui & Harrison 2002, McAndrew et al 2007, Arbones et al 2008 in the NW Iberian upwelling.…”

Fronts at the Surface Ocean Can Shape Distinct Regions of Microbial Activity and Community Assemblages Down to the Bathypelagic Zone: The Azores Front as a Case Study

“…Recent studies have endeavored to define oceanic biomes based on microbial data (e.g., Zwirglmaier et al, 2008;Zinger et al, 2011;Gibbons et al, 2013), while other studies have shown that fronts can enhance microbial activity (e.g., Arístegui and Harrison, 2002) or delimit the distribution of the bacterioplankton community composition in surface waters (Baltar et al, 2016). However, there is almost no information on how surface frontal systems influence the distribution of microbial community composition and activity in the dark water column, which contains around 75% of the prokaryotic biomass and 50% of the prokaryotic production of the global ocean ).…”