Dissolved and suspended organic matter dynamics in the Cape Verde Frontal Zone (NW Africa)

Valiente, Sara; Fernández-Castro, B.; Campanero, Rubén; Marrero-Díaz, Ángeles; Rodríguez-Santana, Ángel; Gelado-Cabellero, M.D.; Nieto‐Cid, Mar; Delgado‐Huertas, Antonio; Arı́stegui, Javier; Álvarez‐Salgado, Xosé Antón

doi:10.1016/j.pocean.2021.102727

Cited by 13 publications

(21 citation statements)

References 75 publications

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“…Artificial upwelling enhanced the C:N ratio in the DOM pool from ~15 to 19-27. Initial DOC : DON values (Figure 2D) were within the range of values reported for the subtropical North Atlantic (Hansell and Carlson, 2001;Valiente et al, 2022). Subsequent increases in DOC : DON ratios as a result of artificial upwelling were similar to those observed in other experimentally-induced diatom blooms (Norrman et al, 1995).…”

Section: Increase In the Relative C Content Of Domsupporting

confidence: 82%

The importance of the dissolved organic matter pool for the carbon sequestration potential of artificial upwelling

Gómez‐Letona

Sebastián²,

Baños³

et al. 2022

Front. Mar. Sci.

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In the face of climate change there is a need to reduce atmospheric CO2 concentrations. Artificial upwelling of nutrient-rich deep waters has been proposed as a method to enhance the biological carbon pump in oligotrophic oceanic regions in order to increase carbon sequestration. Here we examine the effect of different artificial upwelling intensities and modes (single pulse versus recurring pulses) on the dynamics of the dissolved organic matter pool (DOM). We introduced nutrient-rich deep water to large scale mesocosms (~44 m3) in the oligotrophic subtropical North Atlantic and found that artificial upwelling strongly increased DOM concentrations and changed its characteristics. The magnitude of the observed changes was related to the upwelling intensity: more intense treatments led to higher accumulation of dissolved organic carbon (>70 μM of excess DOC over ambient waters for the most intense) and to comparatively stronger changes in DOM characteristics (increased proportions of chromophoric DOM (CDOM) and humic-like fluorescent DOM), suggesting a transformation of the DOM pool at the molecular level. Moreover, the single upwelling pulse resulted in higher CDOM quantities with higher molecular weight than the recurring upwelling mode. Together, our results indicate that under artificial upwelling, large DOM pools may accumulate in the surface ocean without being remineralized in the short-term. Possible reasons for this persistence could be a combination of the molecular diversification of DOM due to microbial reworking, nutrient limitation and reduced metabolic capabilities of the prokaryotic communities within the mesocosms. Our study demonstrates the importance of the DOC pool when assessing the carbon sequestration potential of artificial upwelling.

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Section: Increase In the Relative C Content Of Domsupporting

confidence: 82%

The importance of the dissolved organic matter pool for the carbon sequestration potential of artificial upwelling

Gómez‐Letona

Sebastián²,

Baños³

et al. 2022

Front. Mar. Sci.

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“…The average values of DOC in the epipelagic layer are very similar to that found in Valiente et al (2022) in the same area during summer 2017. They reported similar DOC distribution patterns with columns of relatively high values interspersed with areas of low concentration.…”

Section: Physical-biogeochemical Coupling In the Cvfzsupporting

confidence: 80%

“…A total of 9 WTs have been identified down to 1500 m: Madeira Mode Water (MMW); Eastern North Atlantic Central Water (ENACW) of 15°C and 12°C; South Atlantic Central Water (SACW) of 18°C and 12°C; Subpolar Mode Water (SPMW); Antarctic Intermediate Water (AA); Mediterranean Water (MW) and Labrador Sea Water (LSW). The thermohaline and chemical characteristics of each WT were taken from the literature (Table 1; Valiente et al, 2022).…”

Section: Optimum Multiparameter Mesopelagic Water Mass Analysismentioning

confidence: 99%

“…These mass balance equations were normalized and weighted considering the measurement error of each parameter. Since we have 9 WTs and only 5 linear mixing equations, four mixing groups (see Supplementary Figure 1) were created based on expert knowledge of the hydrography of the study area (Valiente et al, 2022). Samples in the epipelagic layer were excluded from the OMP analysis due to the non-conservative behavior of q, S, SiO 4 H 4 and NO because of exchange of mass, heat and gases with the atmosphere and intense biological activity.…”

Section: Optimum Multiparameter Mesopelagic Water Mass Analysismentioning

confidence: 99%

“…8). A fitting parameter (coefficient b) is included to model the relationship between the chemical variables (e.g., DOC, POC, CDOM, FDOM) and AOU (A ́lvarez- Salgado et al, 2013;A ́lvarez-Salgado et al, 2014;Valiente et al, 2022):…”

Section: Multiple Regression Modelsmentioning

confidence: 99%

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High-resolution variability of dissolved and suspended organic matter in the Cape Verde Frontal Zone

et al. 2022

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Distributions of dissolved (DOM) and suspended (POM) organic matter, and their chromophoric (CDOM) and fluorescent (FDOM) fractions, are investigated at high resolution (< 10 km) in the Cape Verde Frontal Zone (CVFZ) during fall 2017. In the epipelagic layer (< 200 m), meso- and submesoscale structures (meanders, eddies) captured by the high resolution sampling dictate the tight coupling between physical and biogeochemical parameters at the front. Remarkably, fluorescent humic-like substances show relatively high fluorescence intensities between 50 and 150 m, apparently not related to local mineralization processes. We hypothesize that it is due to the input of Sahara dust, which transports highly re-worked DOM with distinctive optical properties. In the mesopelagic layer (200-1500 m), our results suggest that DOM and POM mineralization occurs mainly during the transit of the water masses from the formation sites to the CVFZ. Therefore, most of the local mineralization seems to be due to fast-sinking POM produced in situ or imported from the Mauritanian upwelling. These local mineralization processes lead to the production of refractory CDOM, an empirical evidence of the microbial carbon pump mechanism. DOM released from these fast-sinking POM is the likely reason behind the observed columns of relatively high DOC surrounded by areas of lower concentration. DOM and POM dynamics in the CVFZ has turned out to be very complex, in parallel to the complexity of meso- and submesoscale structures present in the area. On top of this high resolution variability, the input of Sahara dust or the release of DOM from sinking particles have been hypothesized to explain the observed distributions.

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Activity and distribution of diazotrophic communities across the Cape Verde Frontal Zone in the Northeast Atlantic Ocean

et al. 2022

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Dissolved and suspended organic matter dynamics in the Cape Verde Frontal Zone (NW Africa)

Cited by 13 publications

References 75 publications

The importance of the dissolved organic matter pool for the carbon sequestration potential of artificial upwelling

The importance of the dissolved organic matter pool for the carbon sequestration potential of artificial upwelling

High-resolution variability of dissolved and suspended organic matter in the Cape Verde Frontal Zone

Activity and distribution of diazotrophic communities across the Cape Verde Frontal Zone in the Northeast Atlantic Ocean

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