Marine dissolved organic matter (DOM) represents the largest and least understood reservoir of organic carbon on the Earth. It contains about 662 Pg C, a pool almost equivalent to the atmospheric CO2. The Mediterranean Sea (Med Sea) is a low-nutrient-low chlorophyll (LNLC) area and receives different types of compounds (inorganic and organic) from the atmosphere via wet or dry deposition. In addition, it shows dissolved organic carbon (DOC) concentrations and distribution similar to those observed in the oceans, it can therefore be considered as a natural laboratory to gain information about the role of atmospheric deposition in DOM dynamics. The main goals of this study are: (i) to estimate the annual flux of atmospheric DOC, DON and DOP at the Lampedusa Island; (ii) to assess the optical properties (absorption and fluorescence) of the chromophoric DOM (CDOM) in the atmospheric depositions; (iii) to demonstrate the importance of atmospheric deposition in DOM dynamics in the Med Sea. The thesis is organized in 5 chapters. The first chapter reports the vertical distribution of optical properties (absorption and fluorescence) of CDOM for a large area of the Western Med Sea and in the Ionian Sea. The parallel factorial analysis (PARAFAC) applied to 144 fluorescence excitation-emission matrixes (EEMs) allowed for the identification of 5 components: two terrestrial humic-like, one PAH-like, one marine humic-like and one protein-like. The spectra of these components and their vertical profiles were very similar to those observed in the oceans and suggest that atmosphere can represents an important source for pollutants and humi-substances identified in CDOM pool. The second chapter presents the first data on atmospheric input of DOC at Lampedusa Island, collected from March 19th 2015 to November 3rd 2016. DOC fluxes ranged between 0.06 and 1.78 mmol C m-2 day-1, with a marked variability. A good linear relationship was found between DOC and metals. The highest peak were found in correspondence of high value of iron and phosphorus. The optical properties of CDOM in atmospheric deposition are presented and discussed in chapter 3. The PARAFAC applied to 91 EEMs validated a six-component model. The spectra of these components are similar to those observed in the open waters of the Med Sea and in the oceans. The results reported in these 2 chapters indicate that atmospheric input can be an important and up to now overlooked source of DOC and CDOM to the Med Sea. Chapter 4 focuses on atmospheric input of DOP DON and the C:N:P stoichiometric ratio. DOP fluxes ranged between 0 and 2.7∙10-2 mmol m-2 d-1, while DON ranged between 1.5∙10-2 and 0.25 mmol m-2 d-1. C:N:P molar ratios in atmospheric DOM showed a marked variability, with average values of C:N of 12, C:N of 1909 and N:P of 292. These atmospheric fluxes and elemental ratios of DOM were in good agreement with depositions occurred in the north-western Med Sea, suggesting the possibility to have an accurate estimate of atmospheric DOM input on basin scale. Chapter 5 reports data about a mesocosm experiment of dust addition, carried out in Northern Red Sea in July 2017 aimed at the understanding the effect of dust deposition on the microbial ecology and DOM dynamics. The preliminary results show an indirect effect of dust addition on DOM dynamics, the C content of dust is in fact too low to determine an increase of DOC after the addition, but the changes in the ecosystems are responsible for a marked increase in DOC 20 hours after the dust addition.

Il ruolo degli input atmosferici nella dinamica della sostanza organica disciolta: l'esempio del Mar Mediterraneo / Galletti, Yuri. - (2018 Oct 30).

Il ruolo degli input atmosferici nella dinamica della sostanza organica disciolta: l'esempio del Mar Mediterraneo

GALLETTI, YURI
2018-10-30

Abstract

Marine dissolved organic matter (DOM) represents the largest and least understood reservoir of organic carbon on the Earth. It contains about 662 Pg C, a pool almost equivalent to the atmospheric CO2. The Mediterranean Sea (Med Sea) is a low-nutrient-low chlorophyll (LNLC) area and receives different types of compounds (inorganic and organic) from the atmosphere via wet or dry deposition. In addition, it shows dissolved organic carbon (DOC) concentrations and distribution similar to those observed in the oceans, it can therefore be considered as a natural laboratory to gain information about the role of atmospheric deposition in DOM dynamics. The main goals of this study are: (i) to estimate the annual flux of atmospheric DOC, DON and DOP at the Lampedusa Island; (ii) to assess the optical properties (absorption and fluorescence) of the chromophoric DOM (CDOM) in the atmospheric depositions; (iii) to demonstrate the importance of atmospheric deposition in DOM dynamics in the Med Sea. The thesis is organized in 5 chapters. The first chapter reports the vertical distribution of optical properties (absorption and fluorescence) of CDOM for a large area of the Western Med Sea and in the Ionian Sea. The parallel factorial analysis (PARAFAC) applied to 144 fluorescence excitation-emission matrixes (EEMs) allowed for the identification of 5 components: two terrestrial humic-like, one PAH-like, one marine humic-like and one protein-like. The spectra of these components and their vertical profiles were very similar to those observed in the oceans and suggest that atmosphere can represents an important source for pollutants and humi-substances identified in CDOM pool. The second chapter presents the first data on atmospheric input of DOC at Lampedusa Island, collected from March 19th 2015 to November 3rd 2016. DOC fluxes ranged between 0.06 and 1.78 mmol C m-2 day-1, with a marked variability. A good linear relationship was found between DOC and metals. The highest peak were found in correspondence of high value of iron and phosphorus. The optical properties of CDOM in atmospheric deposition are presented and discussed in chapter 3. The PARAFAC applied to 91 EEMs validated a six-component model. The spectra of these components are similar to those observed in the open waters of the Med Sea and in the oceans. The results reported in these 2 chapters indicate that atmospheric input can be an important and up to now overlooked source of DOC and CDOM to the Med Sea. Chapter 4 focuses on atmospheric input of DOP DON and the C:N:P stoichiometric ratio. DOP fluxes ranged between 0 and 2.7∙10-2 mmol m-2 d-1, while DON ranged between 1.5∙10-2 and 0.25 mmol m-2 d-1. C:N:P molar ratios in atmospheric DOM showed a marked variability, with average values of C:N of 12, C:N of 1909 and N:P of 292. These atmospheric fluxes and elemental ratios of DOM were in good agreement with depositions occurred in the north-western Med Sea, suggesting the possibility to have an accurate estimate of atmospheric DOM input on basin scale. Chapter 5 reports data about a mesocosm experiment of dust addition, carried out in Northern Red Sea in July 2017 aimed at the understanding the effect of dust deposition on the microbial ecology and DOM dynamics. The preliminary results show an indirect effect of dust addition on DOM dynamics, the C content of dust is in fact too low to determine an increase of DOC after the addition, but the changes in the ecosystems are responsible for a marked increase in DOC 20 hours after the dust addition.
30-ott-2018
30
2016/2017
Settore BIO/07 - Ecologia
Università degli Studi di Trieste
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Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/11368/2931986
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