Abstract. This study assesses marine biological production of organic carbon 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 (c_p) and backscattering (b_bp) coefficients. The diel cycle of c_p provided a robust proxy for quantifying biological production in both systems; that of b_bp 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, yet variable, contribution to the water column production of the SCM layer (16–42%). 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, induced by phytoplankton photoacclimation and contributes moderately to water column production. These results emphasize 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.

中文翻译：

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贫营养时期地中海两个相反区域的生物生产：基于BGC-Argo轮廓浮标测得的光学性质的狄尔循环的估计

摘要。这项研究基于由两个BioGeoChemical-Argo（BGC-Argo）浮标监测的生物光学特性的狄尔变异性，评估了海洋生物生产有机碳的能力。在夏季，在两个不同的地中海系统（西北利古里亚海和爱奥尼亚中海）进行了实验。我们使用现有方法对颗粒束衰减（c _p）和反向散射（b）进行diel循环测量，得出了颗粒有机碳（POC）存量和总的社会生产量，这些颗粒已集成在表面，常绿和亚叶绿素最大值（SCM）层内。_bp）系数。c _p的diel循环提供了一个强大的代理，可以量化两个系统中的生物产量。b的_bp比较不那么健壮。取决于将测得的光学系数转换为POC的生物光学关系的选择，得出的一次生产估算值相差2倍，因此这是限制的关键步骤。我们的结果表明，对SCM层水柱产量的贡献很大（但变化很大）（16-42％）。在利古里亚海中，SCM是一个季节性特征，表现为地下生物量最大值（SBM），并具有通过增加产量来应对情节性非生物强迫的能力。相反，在爱奥尼亚海中，SCM是永久性的，由浮游植物的光适应引起，并适度地促进了水柱的产生。这些结果强调了在BGC-Argo轮廓浮标上部署透射计的强大潜力，从而可以非侵入式地进行定量在具有周期性或永久性SCM的分层贫营养系统水柱中原位生物生产有机碳，这是全球海洋中的普遍特征。