Vertical distribution of dissolved organic carbon (DOC) in the Mediterranean Sea

2006 ◽  
Vol 31 ◽  
pp. 205-216 ◽  
Author(s):  
C Santinelli ◽  
BB Manca ◽  
GP Gasparini ◽  
L Nannicini ◽  
A Seritti
Keyword(s):  
Organic Carbon ◽  
Dissolved Organic Carbon ◽  
Vertical Distribution ◽  
Mediterranean Sea ◽  
The Mediterranean

DOM DYNAMICS IN THE MEDITERRANEAN SEA. Can a new fluorescence SENSOR contribute to its understanding?

2020 ◽  
Author(s):  
Simona Retelletti Brogi ◽  
Marta Furia ◽  
Giancarlo Bachi ◽  
Vanessa Cardin ◽  
Giuseppe Civitarese ◽  
...  
Keyword(s):  
Organic Carbon ◽  
Dissolved Organic Carbon ◽  
Mediterranean Sea ◽  
Water Column ◽  
Fluorescence Sensor ◽  
Global Ocean ◽  
Intermediate Water ◽  
Physical Processes ◽  
Open Sea ◽  
The Mediterranean

<p>The Mediterranean Sea (Med Sea) can be considered as a natural laboratory for the study of dissolved organic matter (DOM) dynamics. Despite its small size, it is characterized by the same physical processes and dissolved organic carbon (DOC) concentration and distribution as the global ocean. The Med Sea deep water DOC pool is however older than the Atlantic one and differences in the microbial loop and in DOM dynamics have been observed between the eastern (EMED) and western (WMED) basins. Fluorescence is a fast, cheap and highly sensitive tool to study DOM dynamics, it can therefor give useful information about the main processes affecting DOM distribution.</p><p>The main aims of this study were: (i) to investigate DOM dynamics in both Med Sea basins, in relation to the physical processes (e.g. vertical stratification, irradiation); and (ii) to validate the use of a new fluorescence sensor, developed in the framework of the SENSOR project (POR FESR, Tuscany Region), for the rapid, in-situ measurements of open-sea fluorescent DOM (FDOM). DOM dynamics was investigated by measuring dissolved organic carbon (DOC) and the fluorescence of FDOM. Samples were collected from surface to bottom in 26 stations during the trans-Mediterranean cruise “MSM72”, carried out on board the R/V MARIA S.MERIAN (Institut für Meereskunde der Universität Hamburg). The stations cover both the EMED and the WMED, from Gibraltar to the Crete Island.</p><p>Six fluorescent components were identified by applying the parallel factorial analysis (PARAFAC) to the measured excitation-emission matrices (EEMs). Two components were identified as marine humic-like, two as terrestrial humic-like, one as protein-like and one as polycyclic aromatic hydrocarbon-like (PAH-like).</p><p>Temperature and salinity increased moving from the WMED to the EMED. A surface minimum in salinity, was observed in the WMED, indicating the occurrence of the Atlantic Water (AW), whereas the presence of the Levantine Intermediate Water (LIW) was observed south of Crete. The vertical distribution of both DOC and humic-like FDOM was strongly affected by the water masses circulation and water column stratification. In the upper 200 m, DOC markedly increased from 50 to 80 μM moving eastward, likewise the protein-like component dominates the upper layer and increased moving from Gibraltar to Crete. In contrast, the humic-like components showed a minimum in the surface layer, and a decreasing moving eastward, probably due to photobleaching. The PAH-like component showed its maximum in correspondence with the areas characterized by intensive naval traffic. The accumulation of DOC, observed in the EMED, could be explained by a change in DOM quality, supported by the differences in FDOM.</p><p>In 2 selected stations, the fluorescence of humic-like and protein-like compounds was also measured along the water column by using the new fluorescence sensor and compared with PARAFAC results, in order to evaluate its performance for open sea waters.</p>

scholarly journals New insights into the organic carbon export in the Mediterranean Sea from 3-D modeling

2015 ◽  
Vol 12 (8) ◽  
pp. 6147-6213
Author(s):  
A. Guyennon ◽  
M. Baklouti ◽  
F. Diaz ◽  
J. Palmieri ◽  
J. Beuvier ◽  
...  
Keyword(s):  
Organic Carbon ◽  
Dissolved Organic Carbon ◽  
Mediterranean Sea ◽  
Coupled Model ◽  
Nutrient Concentrations ◽  
Biogeochemical Model ◽  
Carbon Export ◽  
Western Basin ◽  
Basin Scale ◽  
The Mediterranean

Abstract. The Mediterranean Sea is one of the most oligotrophic regions of the oceans, and nutrients have been shown to limit both phytoplankton and bacterial activities. This has direct implications on the stock of dissolved organic carbon (DOC), whose high variability has already been well-documented even if measurements are still sparse and are associated with important uncertainties. We here propose a Mediterranean Basin-scale view of the export of organic carbon, under its dissolved and particulate forms. For this purpose, we have used a coupled model combining a mechanistic biogeochemical model (Eco3M-MED) and a high-resolution (eddy-resolving) hydrodynamic simulation (NEMO-MED12). This is the first Basin-scale application of the biogeochemical model Eco3M-MED and is shown to reproduce the main spatial and seasonal biogeochemical characteristics of the Mediterranean Sea. Model estimations of carbon export are of the same order of magnitude as estimations from in situ observations, and their respective spatial patterns are consistent with each other. As for surface chlorophyll, nutrient concentrations, and productivity, strong differences between the Western and Eastern Basins are evidenced by the model for organic carbon export, with only 39% of organic carbon (particulate and dissolved) export taking place in the Western Basin. The major result is that except for the Alboran Sea, dissolved organic carbon (DOC) contribution to organic carbon export is higher than that of particulate (POC) in the whole Basin, especially in the Eastern Basin. This paper also investigates the seasonality of DOC and POC exports as well as the differences in the processes involved in DOC and POC exports.

scholarly journals Sinking microplastics in the water column: simulations in the Mediterranean Sea

Ocean Science ◽  
2021 ◽  
Vol 17 (2) ◽  
pp. 431-453
Author(s):  
Rebeca de la Fuente ◽  
Gábor Drótos ◽  
Emilio Hernández-García ◽  
Cristóbal López ◽  
Erik van Sebille
Keyword(s):  
Vertical Distribution ◽  
Mediterranean Sea ◽  
Water Column ◽  
Large Scale ◽  
Circulation Model ◽  
Small Scale ◽  
The Mediterranean ◽  
Scale Turbulence ◽  
Non Gaussian ◽  
The Vertical Distribution

Abstract. We study the vertical dispersion and distribution of negatively buoyant rigid microplastics within a realistic circulation model of the Mediterranean sea. We first propose an equation describing their idealized dynamics. In that framework, we evaluate the importance of some relevant physical effects (inertia, Coriolis force, small-scale turbulence and variable seawater density), and we bound the relative error of simplifying the dynamics to a constant sinking velocity added to a large-scale velocity field. We then calculate the amount and vertical distribution of microplastic particles on the water column of the open ocean if their release from the sea surface is continuous at rates compatible with observations in the Mediterranean. The vertical distribution is found to be almost uniform with depth for the majority of our parameter range. Transient distributions from flash releases reveal a non-Gaussian character of the dispersion and various diffusion laws, both normal and anomalous. The origin of these behaviors is explored in terms of horizontal and vertical flow organization.

scholarly journals Optical Properties and Biochemical Indices of Marine Particles in the Open Mediterranean Sea: The R/V Maria S. Merian Cruise, March 2018

2021 ◽  
Vol 9 ◽  
Author(s):  
Spyros Chaikalis ◽  
Constantine Parinos ◽  
Jürgen Möbius ◽  
Alexandra Gogou ◽  
Dimitris Velaoras ◽  
...  
Keyword(s):  
Optical Properties ◽  
Particulate Matter ◽  
Organic Carbon ◽  
Mediterranean Sea ◽  
Particulate Organic Carbon ◽  
Beam Attenuation ◽  
Median Diameter ◽  
The Mediterranean ◽  
Biochemical Indices ◽  
Beam Attenuation Coefficient

A rich data set on particulate matter optical properties and parameters (beam attenuation coefficient, volume concentration, particle size and PSD slope), accompanied by measurements of biochemical indices (particulate organic carbon, particulate nitrogen and their stable isotopic composition) was obtained from the surface to deep waters across the Mediterranean Sea, in March-April 2018. A decrease of beam attenuation coefficients, total particle volume concentrations, particulate organic carbon and nitrogen concentrations was noted towards the eastern Mediterranean Sea (EMed) in comparison to the western Mediterranean Sea (WMed). LISST-derived optical properties were significantly correlated with water mass characteristics. Overall, the most turbid water mass identified in the Mediterranean Sea was the Surface Atlantic water (AW), and the most transparent was the Transitional Mediterranean Water (TMW) in the Cretan Sea, whereas a general decrease in particulate matter concentration is observed from the WMed towards the EMed. Relatively depleted δ13C-POC values in the particle pool of the open Mediterranean Sea can be attributed to contribution from terrestrial inputs, mainly via atmospheric deposition. Throughout the entire water column, a significant positive correlation between particle beam attenuation coefficient and particulate organic carbon concentration is observed in the open Mediterranean Sea. Such relationship suggests the predominance of organic particles with biogenic origin. POC concentration and particle median diameter D50 are significantly and negatively correlated both in the WMed and the EMed Sea, confirming that small particles are POC-rich. At depth, a prominent decrease of most measured parameters was observed, with the exception of particle median diameter that increased substantially in the EMed towards the deep sea, suggesting potentially enhanced aggregation processes. The low particle size distribution slope ξ observed in the EMed, corresponding to larger particle populations, supports the above notion. Basin-wide Rayleigh-type isotopic fractionation in vertical profiles of δ15N-PN across the Mediterranean Sea, underlines the differences in the trophic characters of the two sub-basins and highlights the role of circulation changes on biogeochemical parameters and the redistribution of particulate matter as a source of nutrients in the water column.

scholarly journals New insights into the organic carbon export in the Mediterranean Sea from 3-D modeling

2015 ◽  
Vol 12 (23) ◽  
pp. 7025-7046 ◽  
Author(s):  
A. Guyennon ◽  
M. Baklouti ◽  
F. Diaz ◽  
J. Palmieri ◽  
J. Beuvier ◽  
...  
Keyword(s):  
Organic Carbon ◽  
Mediterranean Sea ◽  
Coupled Model ◽  
Phosphate Limitation ◽  
Biogeochemical Model ◽  
Carbon Export ◽  
Western Basin ◽  
Eastern Basin ◽  
Basin Scale ◽  
The Mediterranean

Abstract. The Mediterranean Sea is one of the most oligotrophic regions of the oceans, and nutrients have been shown to limit both phytoplankton and bacterial activities, resulting in a potential major role of dissolved organic carbon (DOC) export in the biological pump. Strong DOC accumulation in surface waters is already well documented, though measurements of DOC stocks and export flux are still sparse and associated with major uncertainties. This study provides the first basin-scale overview and analysis of organic carbon stocks and export fluxes in the Mediterranean Sea through a modeling approach based on a coupled model combining a mechanistic biogeochemical model (Eco3M-MED) and a high-resolution (eddy-resolving) hydrodynamic simulation (NEMO-MED12). The model is shown to reproduce the main spatial and seasonal biogeochemical characteristics of the Mediterranean Sea. Model estimations of carbon export are also of the same order of magnitude as estimations from in situ observations, and their respective spatial patterns are mutually consistent. Strong differences between the western and eastern basins are evidenced by the model for organic carbon export. Though less oligotrophic than the eastern basin, the western basin only supports 39 % of organic carbon (particulate and dissolved) export. Another major result is that except for the Alboran Sea, the DOC contribution to organic carbon export is higher than that of particulate organic carbon (POC) throughout the Mediterranean Sea, especially in the eastern basin. This paper also investigates the seasonality of DOC and POC exports as well as the differences in the processes involved in DOC and POC exports in light of intracellular quotas. Finally, according to the model, strong phosphate limitation of both bacteria and phytoplankton growth is one of the main drivers of DOC accumulation and therefore of export.

scholarly journals Organic carbon dynamics in the Mediterranean Sea: An integrated study

2012 ◽  
Vol 26 (4) ◽  
pp. n/a-n/a ◽  
Author(s):  
Chiara Santinelli ◽  
Richard Sempéré ◽  
France Van Wambeke ◽  
Bruno Charriere ◽  
Alfredo Seritti
Keyword(s):  
Organic Carbon ◽  
Mediterranean Sea ◽  
Carbon Dynamics ◽  
The Mediterranean ◽  
Integrated Study
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