Abstract
Abstract. This study assesses marine community production based on the diel variability of bio-optical properties monitored by two BioGeoChemical-Argo (BGC-Argo) floats. Experiments were conducted in two distinct Mediterranean systems, the northwestern Ligurian Sea and the central Ionian Sea, during summer months. We derived particulate organic carbon (POC) stock and gross community production integrated within the surface, euphotic and subsurface chlorophyll maximum (SCM) layers, using an existing approach applied to diel cycle measurements of the particulate beam attenuation (cp) and backscattering (bbp) coefficients. The diel cycle of cp provided a robust proxy for quantifying biological production in both systems; that of bbp was comparatively less robust. Derived primary production estimates vary by a factor of 2 depending upon the choice of the bio-optical relationship that converts the measured optical coefficient to POC, which is thus a critical step to constrain. Our results indicate a substantial contribution to the water column production of the SCM layer (16 %–42 %), which varies largely with the considered system. In the Ligurian Sea, the SCM is a seasonal feature that behaves as a subsurface biomass maximum (SBM) with the ability to respond to episodic abiotic forcing by increasing production. In contrast, in the Ionian Sea, the SCM is permanent, primarily induced by phytoplankton photoacclimation, and contributes moderately to water column production. These results clearly demonstrate the strong potential for transmissometers deployed on BGC-Argo profiling floats to quantify non-intrusively in situ biological production of organic carbon in the water column of stratified oligotrophic systems with recurring or permanent SCMs, which are widespread features in the global ocean.
Highlights
Primary production is an essential process in the global ocean carbon cycle (Field et al, 1998)
We assess the usefulness of the diel cycle of the bbp coefficient for deriving community production, in comparison to the cpderived estimates as a reference, and discuss the cp-derived estimates
With the bbp / Chl ratio being more sensitive to small-sized particles than the cp / Chl ratio, these results suggest that, in the subsurface chlorophyll maximum (SCM) layer, the particulate organic carbon (POC) in the small size fractions of the Ligurian and Ionian seas is more similar than that in the large size fractions
Summary
Primary production is an essential process in the global ocean carbon cycle (Field et al, 1998). M. Barbieux et al.: Biological production in two contrasted regions of the Mediterranean Sea mary production and community respiration in the ocean determines the trophic status of marine systems, i.e., whether the system acts as a source or a sink of carbon (Williams, 1993). Barbieux et al.: Biological production in two contrasted regions of the Mediterranean Sea mary production and community respiration in the ocean determines the trophic status of marine systems, i.e., whether the system acts as a source or a sink of carbon (Williams, 1993) This balance depends on the considered region and varies substantially according to spatial and temporal scales (Geider et al, 1997; Duarte and Agusti, 1998; del Giorgio and Duarte, 2002). It is necessary to develop capabilities for assessing primary production on a global scale and for characterizing and quantifying the biogeochemical functioning of marine ecosystems at smaller spatial and temporal scales (Serret et al, 1999; González et al, 2001, 2002)
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
