Papers by chiara santinelli
The authors of the manuscript by F. Madonna et al examined in detail the comments provided by the... more The authors of the manuscript by F. Madonna et al examined in detail the comments provided by the anonymous referee #1 and acknowledge his/her effort in providing comments aimed at improving the robustness of the manuscript. Below, the authors report in bold their replies to the reviewer's comments
This NCEI Accession includes discrete profile data collected during the R/V Urania cruise SESAME_... more This NCEI Accession includes discrete profile data collected during the R/V Urania cruise SESAME_IT04 (EXPOCODE 48UR20080318) in the Mediterranean Sea from 2008-03-18 to 2008-04-05. These data include dissolved inorganic carbon (DIC), total alkalinity, water temperature, salinity, dissolved oxygen, silicate, nitrate and phosphate.
Journal of Marine Science and Engineering
Estuarine processes play a key role in determining the amount and quality of land-derived dissolv... more Estuarine processes play a key role in determining the amount and quality of land-derived dissolved organic matter (DOM) reaching the oceans. Microbial-mediated reactions can affect the concentration, quality, and bioavailability of DOM within an estuary. In this study, we investigated biological DOM removal in a small estuary and its variability in two contrasting seasons (spring and autumn) characterized by natural differences in the concentration and quality of the riverine DOM. Two incubation experiments were carried out using natural DOM and heterotrophic prokaryotes community collected at the estuary in March and September. Dissolved organic carbon (DOC) concentration, DOM fluorescence, and the heterotrophic prokaryotes abundance (HPA) showed marked differences between the two seasons. These parameters were followed through time for up to two months. Despite the marked differences in the initial conditions, the DOC removal rates were surprisingly similar in the two periods (16...
Marine Chemistry, 2020
The karstic Krka River is characterized by having lower dissolved organic carbon (DOC) concentrat... more The karstic Krka River is characterized by having lower dissolved organic carbon (DOC) concentrations (~30 μM) than coastal seawater (~60 μM). This peculiarity, together with the pristine nature of this area, makes the Krka River estuary a natural laboratory where it is possible to discriminate among the different dissolved organic matter (DOM) sources (riverine, marine and produced in-situ) and to study the main processes of DOM production and removal. The hypothesis behind this work is that in winter, due to the high discharge of the river, most of the DOM has a terrestrial signature, whereas in summer autochthonous DOM compose the main fraction of the DOM pool because of the reduced discharge, the high temperature and primary production. Our data shows that DOM in the river mainly consists of terrestrial molecules, as suggested by the high chromophoric content and low spectral slope (S275–295) values, as well by the predominance of humic-like substances. DOM in the seawater featu...
The dataset includes information on dissolved organic matter concentration (DOC) and quality (CDO... more The dataset includes information on dissolved organic matter concentration (DOC) and quality (CDOM, FDOM) in the Arno River (Italy) in 2014 and 2015, together with water temperature and river discharge on the sampling dates. Weekly samples were collected from a station located in the lower part of the river, the closest point to the mouth, not influenced by seawater. Methods: Surface (upper 1m) water samples were collected in the center of the river from a bridge using an acid-washed Teflon sampler. Water temperature was measured by a portable Hanna 9033 probe (Hanna Instruments Inc., USA); Daily average river discharge are available from the Regional Hydrological Service (www.sir.toscana.it); Samples for DOM analyses were collected into acid-washed polycarbonate bottles (Nalgene) and kept refrigerated and in the dark until filtration. Samples were filtered through a 0.2 μm pore size filter (Whatman Polycap, 6705-3602 capsules) and dispensed into 3 x 60 ml acid-washed polycarbonate (Nalgene) bottles, used as analytical replicates. DOC, CDOM, and FDOM were immediately measured after filtration. DOC was measured by high-temperature catalytic oxidation using a Shimadzu Total Organic Carbon analyzer (TOC-Vcsn). The instrument performance was verified by comparison with DOC Consensus Reference Waters (Hansell, 2005) (CRM Batch #13 nominal concentration of 41-44 μM; measured concentration 42.3 ± 0.9 μM, n=88) Absorbance spectra (230 to 700 nm) were measured using a Jasco UV-visible spectrophotometer (Mod-7850) with a 10 cm quartz cuvette. Fluorescence excitation-emission Matrixes (EEMs) were obtained using the Aqualog spectrofluorometer (Horiba). Excitation ranged between 250 and 450 nm at 5 nm increment, emission was recorded between 212 and 620 nm every 0.8 nm with an integration time of 5 seconds. The EEMs were subtracted by the EEM of Milli-Q water and corrected for the inner-filter effect. Rayleigh and Raman scatter peaks were removed by using the monotone cubic interpolation and EEMs were normalized by the integr [...]
Le attivita di campionamento ed acquisizione dati svolte durante la campagna CISAS_2 si inserisco... more Le attivita di campionamento ed acquisizione dati svolte durante la campagna CISAS_2 si inseriscono in seno al progetto “Centro internazionale di studi avanzati su ambiente ed impatti su ecosistema e salute umana (CISAS)” del CNR. L’obiettivo principale del progetto CISAS e la comprensione dei processi e dei meccanismi di trasferimento di alcuni contaminanti convenzionali (metalli pesanti, POPs, radionuclidi, ecc.) e di alcuni contaminanti emergenti (PDBE, composti farmaceutici di nuova generazione, ecc.) dall’ambiente inteso come l’insieme di atmosfera-suoli-acque sotterranee-matrici marine (acque e sedimento) all’ecosistema e all’uomo. Le aree di indagine del progetto sono i Siti di Interesse Nazionale (SIN) di Priolo, Milazzo-Pace del Mela e Crotone che, per specificita e modalita di impatto antropogenico sull’ambiente, l’ecosistema e la salute umana, coprono un ampio spettro di tipologie di interesse. La campagna oceanografica CISAS_ 2 e stata dedicata alla caratterizzazione amb...
Marine Chemistry, 2021
Most of the ocean is deep with the majority of its volume (> 80%) lying under a depth greater ... more Most of the ocean is deep with the majority of its volume (> 80%) lying under a depth greater than 1000 m. Deep-ocean substrates input is mainly supplied as organic matter (in particulate and/or dissolved forms) by physical and biological processes. Bioavailable dissolved organic carbon (DOC) is mainly consumed in surface water by prokaryotes, while most of DOC in the deep ocean is recalcitrant. Deep-sea prokaryotes are known to be adapted to degrade complex substrates. In this study, we investigate the utilization of HMW-DOC on the short temporal scale (10–15 days) by deep-sea prokaryotes maintained at in situ high-pressure conditions. Deep-sea prokaryotic natural assemblages were collected in the Mediterranean Sea in two contrasting hydrological conditions (water column stratification and deep-water formation period conditions). The experimental results were coupled with a cell-quota model, in order to quantify the kinetics of HMW-DOC degradation and its impact on the prokaryot...
Trace metal (TM) concentrations in water samples collected in the Arno River, its main tributarie... more Trace metal (TM) concentrations in water samples collected in the Arno River, its main tributaries and estuarine transect were measured in order to evaluate anthropogenic influence, TM dynamics and a potential impact on the coastal sea. A downstream increase of concentration for most of TM was observed in the river, whereas a (near)conservative behavior was registered for the majority of dissolved TM in estuarine salinity gradient.
The paper by Santinelli et al. presents results of Dissolved Organic Carbon (DOC) measurements in... more The paper by Santinelli et al. presents results of Dissolved Organic Carbon (DOC) measurements in the Tyrrhenian area of the western Mediterranean Sea (MS), together with data from models and satellite observations. The overall goal is to explore the impact of the surface circulation on carbon dynamics in the western MS. According to the abstract, the main result is the quantification of the annual DOC input by the advection of Atlantic water (AW) in the Tyrrhenian area (TYS) of 8.8-37.9 10ËĘ12 g DOC yr-1.
Frontiers in Chemistry
The determination of copper (Cu) speciation and its bioavailability in natural waters is an impor... more The determination of copper (Cu) speciation and its bioavailability in natural waters is an important issue due to its specific role as an essential micronutrient but also a toxic element at elevated concentrations. Here, we report an improved anodic stripping voltammetry (ASV) method for organic Cu speciation, intended to eliminate the important problem of surface-active substances (SAS) interference on the voltammetric signal, hindering measurements in samples with high organic matter concentration. The method relies on the addition of nonionic surfactant Triton-X-100 (T-X-100) at a concentration of 1 mg L−1. T-X-100 competitively inhibits the adsorption of SAS on the Hg electrode, consequently 1) diminishing SAS influence during the deposition step and 2) strongly improving the shape of the stripping Cu peak by eliminating the high background current due to the adsorbed SAS, making the extraction of Cu peak intensities much more convenient. Performed tests revealed that the addit...
Water
In the dark ocean, the balance between the heterotrophic carbon demand and the supply of sinking ... more In the dark ocean, the balance between the heterotrophic carbon demand and the supply of sinking carbon through the biological carbon pump remains poorly constrained. In situ tracking of the dynamics of microbial degradation processes occurring on the gravitational sinking particles is still challenging. Our particle sinking simulator system (PASS) intends to mimic as closely as possible the in situ variations in pressure and temperature experienced by gravitational sinking particles. Here, we used the PASS to simultaneously track geochemical and microbial changes that occurred during the sinking through the mesopelagic zone of laboratory-grown Emiliania huxleyi aggregates amended by a natural microbial community sampled at 105 m depth in the North Atlantic Ocean. The impact of pressure on the prokaryotic degradation of POC and dissolution of E. huxleyi-derived calcite was not marked compared to atmospheric pressure. In contrast, using global O2 consumption monitored in real-time in...
Deep Sea Research Part I: Oceanographic Research Papers
Journal of Marine Science and Engineering
Photodegradation is a natural process that strongly affects the chromophoric fraction of dissolve... more Photodegradation is a natural process that strongly affects the chromophoric fraction of dissolved organic matter (DOM), especially in surface water of the oceans. In the euphotic zone, the concentration and quality of DOM are mostly dependent on primary production by phytoplankton. The effect of photodegradation on algal DOM has not been investigated as much as on terrestrial DOM. In this study, we explored the effect of different spectral regions (i.e., full sun spectrum, visible light, 295–800 nm, 305–800 nm, and 320–800 nm) on algal exudates by Emiliania huxleyi, a ubiquitous coccolithophore. The optical properties (absorption and fluorescence) of algal DOM were investigated before and after irradiation with the different spectral regions. The absorption and fluorescence spectra were compared before and after irradiation. The results showed an increase in the effect of photobleaching with increasing irradiation energy for all of the absorbance indices. Similarly, the protein-lik...
Atmospheric fluxes of dissolved organic matter (DOM) were studied for the first time at the Islan... more Atmospheric fluxes of dissolved organic matter (DOM) were studied for the first time at the Island of Lampedusa, a remote site in the Central Mediterranean Sea (Med Sea), close to the Sahara desert, between March 19 th 2015 and April 1 st 2017. The main goals of this work are: to quantify total atmospheric deposition of DOM in this area and to evaluate the impact of dust deposition on DOM dynamics in the surface waters of the Mediterranean Sea. Our data show high variability in DOM deposition rates without a clear seasonality and allow to estimate a dissolved organic carbon (DOC) input from the atmosphere of 120.7 mmol DOC m-2 y-1. Over the entire time-series, the average dissolved organic phosphorous (DOP) and dissolved organic nitrogen (DON) contributions to the total dissolved pools were 40% and 26%, respectively. The data on atmospheric elemental ratios also show that each deposition event is characterized by a specific elemental ratio, suggesting a high variability in DOM composition and the presence of multiple sources. This study indicates that the organic substances transported by Saharan dust at Lampedusa site mainly have natural origin, especially from sea spray and that Saharan dust can be an important carrier of organic substances, even if the load of DOC associated with dust is highly variable. Our estimates suggest that atmospheric input has an impact to the Med Sea larger than to the global ocean and that DOC fluxes from the atmosphere to the Med Sea can be up to 6-fold larger than river input. Longer time series, combined with a modelling effort, are therefore mandatory in order to investigate the response of DOM dynamics in the Med Sea to the change in aerosol deposition pattern due to the effect of climate change. the atmosphere via both wet and dry deposition (Iavorivska et al., 2016). At the global scale, wet deposition transfers about 306-580 Tg DOC yr-1 to the surface of the Earth (Willey et al., 2000; Kanakidou et al., 2012). These values correspond to almost half of the DOC delivered to the oceans by rivers annually (IPCC, 2014). Atmospheric deposition can therefore affect regional C cycling, radiative forcing, and human health (Yan and Kim, 2012; Decina et al., 2018). In addition, the expected increase in ocean stratification due to the global warming will enhance the impact of atmospheric inputs in the surface ecosystem (Kanakidou et al., 2012). The potential magnitude of atmospheric DOC inputs to open waters and the importance of its role in the carbon cycle highlight the need for a better and robust estimation of DOC deposition. In the last years, a few studies have reported data on atmospheric deposition of DOC to the Med Sea. Total (dry + wet) atmospheric deposition was studied in NorthWestern Med Sea in 2006 (Pulido-Villena et al., 2008) and in 2015 (Djaoudi et al., 2018) with contrasting results. In the first study, the highest DOC flux was observed in correspondence with a Saharan dust storm, suggesting a combination of heterogeneous reactions between organic matter and mineral dust in the troposphere. In the second study, the Saharan rain event coincided with a minimum in DOC input, suggesting the presence of an aerosol poorly enriched in organic matter (Djaoudi et al., 2018). These studies were conducted in coastal areas affected by human activities. Direct measurements of total OC (TOC) in rainwater were performed at the Crete Island (Eastern Mediterranean; Economou and Mihalopoulos, 2002). This study did not take into consideration dry deposition. None of the papers cited has studied atmospheric inputs in remote sites, far from possible pollution sources and/or large cities. The main goals of this study are: (1) to quantify total atmospheric deposition of DOC, DON and DOP at the island of Lampedusa, representative of the remote marine environment of the central Med Sea; (2) to investigate the contribution of natural and anthropogenic sources in atmospheric DOC; (3) to estimate the impact of atmospheric deposition on marine ecosystem. 2. Materials and methods 2.1 Sampling site Bulk atmospheric deposition (dry and wet) was collected at the Station for Climate Observations (35.52°N, 12.63°E), maintained by ENEA (the Italian National Agency for New Technologies, Energy and Sustainable Economic Development), on the island of Lampedusa, Italy (Fig. 1), (http://www.lampedusa.enea.it/). An interesting aspect of the Med Sea is related to Dissolved Organic Matter (DOM) stoichiometry. Mediterranean DOC and Dissolved Organic Nitrogen (DON) concentrations and their ratios are similar to those reported for the global ocean (Pujo-Pay et al., 2011; Santinelli, 2015). In the surface waters (0-100 m), C:N:P ratios show that Mediterranean DOM is depleted in Dissolved Organic phosphorous (DOP). The study of C:N:P ratio of DOM in atmospheric deposition is important in order to estimate the relative contribution of atmospheric DOM input to the inventory of the surface DOM pool and to understand the fate of the three elements in the water column. This study reports the results of analyses on deposition collected at Lampedusa island (35.52°N, 12.63°E) located in central Med Sea. Lampedusa is located in an ideal position for the study of atmospheric DOC fluxes to the open Med Sea. The site is interesting, in particular, to investigate the mineral dust contribution (mean dust deposition=7.4 g m-2 year-1 , Vincent et., 2016) to DOC deposition. Lampedusa is a flat island far from large islands or continental areas and from relevant pollutant sources. Although influences from ship traffic emissions (
Science of The Total Environment
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Papers by chiara santinelli