Abstract
Abstract. In the ocean, remineralization rate associated with sinking particles is a crucial variable. Since the 1990s, particulate biogenic barium (Baxs) has been used as an indicator of carbon remineralization by applying a transfer function relating Baxs to O2 consumption (Dehairs's transfer function, Southern Ocean-based). Here, we tested its validity in the Mediterranean Sea (ANTARES/EMSO-LO) for the first time by investigating connections between Baxs, prokaryotic heterotrophic production (PHP) and oxygen consumption (JO2-Opt; optodes measurement). We show that (1) higher Baxs (409 pM; 100–500 m) occurs in situations where integrated PHP (PHP100/500=0.90) is located deeper, (2) higher Baxs occurs with increasing JO2-Opt, and (3) there is similar magnitude between JO2-Opt (3.14 mmol m−2 d−1; 175–450 m) and JO2-Ba (4.59 mmol m−2 d−1; transfer function). Overall, Baxs, PHP and JO2 relationships follow trends observed earlier in the Southern Ocean. We conclude that such a transfer function could apply in the Mediterranean Sea.
Highlights
Ocean ecosystems play a critical role in the Earth’s carbon (C) cycle (IPCC, 2014)
We tested its validity in the Mediterranean Sea (ANTARES/EMSO-LO) for the first time by investigating connections between Baxs, prokaryotic heterotrophic production (PHP) and oxygen consumption (JO2Opt; optodes measurement)
From previous studies we know that Baxs in surface waters is distributed over different, mainly non-barite biogenic phases and incorporated into or adsorbed onto phytoplankton material
Summary
Ocean ecosystems play a critical role in the Earth’s carbon (C) cycle (IPCC, 2014). The quantification of their impacts of both present conditions and future predictions remains one of the greatest challenges in oceanography (Siegel et al, 2016). The biological C pump is termed for the numerous processes involved in maintaining the vertical gradient in dissolved inorganic C. This includes processes such as organic matter production at the surface, its export and subsequent remineralization. There is no consensus on C transfer efficiency estimations from field experiments, leading to an imbalance of the water column C budget (Giering et al, 2014) Resolving this imbalance is at the core of numerous studies in the global ocean, and regionally, especially in the Mediterranean Sea (MedSea). In a context of climate changes, better constraining C fluxes and the ocean C storage capacity is of crucial importance
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