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Water
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Characterization of Organic Matter in Marine and Freshwater Environment
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Characterization of Organic Matter in Marine and Freshwater Environment

A special issue of Water (ISSN 2073-4441). This special issue belongs to the section "Biodiversity and Functionality of Aquatic Ecosystems".

Deadline for manuscript submissions: closed (30 November 2022) | Viewed by 13216

Special Issue Editors

Dr. Slađana Strmečki Kos

E-Mail Website
Guest Editor
Division for Marine and Environmental Research, Ruđer Bošković Institute, Zagreb, Croatia
Interests: marine biogeochemistry; atmospheric deposition; air-sea interaction; marine and atmospheric organic matter; trace metal-organic matter interaction; electroanalysis
Special Issues, Collections and Topics in MDPI journals
Dr. Blaženka Gašparović

E-Mail Website
Co-Guest Editor
Division for Marine and Environmental Research, Institute Ruđer Bošković, Zagreb, Croatia
Interests: marine organic matter; lipid biogeochemistry; algae; phytoplankton; fatty acids
Special Issues, Collections and Topics in MDPI journals

Special Issue Information

Dear Colleagues,

Organic matter in marine and freshwater environments has a complex chemical composition and physico-chemical properties that depend on its source, interactions, and possibilities for biogeochemical transformation and preservation. The influence of the living world, from the smallest phytoplankton and microbes to larger zooplankton, as well as the geology of the aquatic system are crucial to understanding the role of organic matter in water and the possible role of oceans, seas, and lakes in carbon sequestration. Organic molecules play a role in the distribution of carbon by influencing the global carbon cycle and the associated climate changes. On the other hand, organic matter changes when exposed to different types of environmental stressors, such as changes in temperature, pH, and salinity, anthropogenic pollution, and atmospheric contributions. Changes in organic matter in waters have an impact on other chemical components of water and thus indirectly affect water quality. Qualitative and quantitative characterization of heterogeneous natural organic matter remains a major challenge for chemists and oceanographers around the world and requires the development of new separation methods and highly sensitive analytical methods.

The aim of this Special Issue is to publish high-quality original research papers and review articles addressing recent advances in the characterization of global or local natural organic matter, the use of new methods, and/or developments in monitoring.

Dr. Slađana Strmečki Kos
Dr. Blaženka Gašparović
Guest Editors

Manuscript Submission Information

Manuscripts should be submitted online at www.mdpi.com by registering and logging in to this website. Once you are registered, click here to go to the submission form. Manuscripts can be submitted until the deadline. All submissions that pass pre-check are peer-reviewed. Accepted papers will be published continuously in the journal (as soon as accepted) and will be listed together on the special issue website. Research articles, review articles as well as short communications are invited. For planned papers, a title and short abstract (about 100 words) can be sent to the Editorial Office for announcement on this website.

Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are thoroughly refereed through a single-blind peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Water is an international peer-reviewed open access semimonthly journal published by MDPI.

Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 2600 CHF (Swiss Francs). Submitted papers should be well formatted and use good English. Authors may use MDPI's English editing service prior to publication or during author revisions.

Keywords

  • organic matter;
  • biogeochemistry;
  • molecular composition;
  • phytoplankton;
  • pollution;
  • climate change;
  • interaction;
  • analytical methods;
  • water quality;
  • monitoring.

Published Papers (6 papers)

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Research

16 pages, 4272 KiB  
Article
TreatEEM—A Software Tool for the Interpretation of Fluorescence Excitation-Emission Matrices (EEMs) of Dissolved Organic Matter in Natural Waters
by Dario Omanović, Saša Marcinek and Chiara Santinelli
Water 2023, 15(12), 2214; https://doi.org/10.3390/w15122214 - 12 Jun 2023
Cited by 1 | Viewed by 2299
Abstract
Fluorescence excitation-emission matrices (EEMs) are a useful tool in aquatic sciences for monitoring and studying the biogeochemistry of organic matter in natural waters and engineered systems. Yet, the interpretation of the wealth of information available in EEMs requires the use of appropriate software. [...] Read more.
Fluorescence excitation-emission matrices (EEMs) are a useful tool in aquatic sciences for monitoring and studying the biogeochemistry of organic matter in natural waters and engineered systems. Yet, the interpretation of the wealth of information available in EEMs requires the use of appropriate software. Existing software tools for the analysis of EEMs, offered by instrument producers, have limited treatment capabilities, while other freely available tools are based on the MATLAB or R programming languages, which require a certain level of programming skills and a pre-installation of MATLAB or R. Here, we present TreatEEM, the first non-commercial, stand-alone Windows-based software tool that provides comprehensive treatment of EEMs. Its greatest advantage is its user-friendly and interactive graphical user interface, providing a convivial and responsive graphical feedback on any action performed on either a single spectrum (recorded at one excitation wavelength) or EEM. The capabilities of TreatEEM, including (a) basic EEM treatment, such as simple inner filter correction, scatter removal, blank subtraction, Raman normalisation, smoothing, drift alignment etc., (b) extraction of useful parameters for DOM characterisation (Coble peaks and fluorescence indices) and (c) preparation of data for PARAFAC analysis plus presentation/manipulation of obtained PARAFAC components, are described in detail, along with a basic theoretical background on these most commonly used treatment steps of EEMs. Full article
(This article belongs to the Special Issue Characterization of Organic Matter in Marine and Freshwater Environment)
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18 pages, 8034 KiB  
Article
Tracking the Spatio-Temporal Distribution of Organic Particles to Predict Macroaggregation in the Northern Adriatic Sea
by Romina Kraus and Nadica Ivošević DeNardis
Water 2023, 15(9), 1665; https://doi.org/10.3390/w15091665 - 24 Apr 2023
Viewed by 1212
Abstract
In the last two decades, the phenomenon of macroaggregation has become more frequent in the Mediterranean Sea and beyond, but it has disappeared in the northern Adriatic. The aim of this study was to present, for the first time, the concentration of surface-active [...] Read more.
In the last two decades, the phenomenon of macroaggregation has become more frequent in the Mediterranean Sea and beyond, but it has disappeared in the northern Adriatic. The aim of this study was to present, for the first time, the concentration of surface-active particles (SAP) at selected sampling stations in the northern Adriatic Sea, as well as phytoplankton and chlorophyll data and physical properties of seawater, in order to investigate the role of SAP in macroaggregation. We used an electrochemical method (polarography and amperometry) to directly and throughput characterize fragile organic material in terms of its dissolved and particulate state in seawater samples. The results show that the concentration of SAP is subject to seasonal variations and was generally higher in the western region. In addition, an increase in surfactant activity and concentration of SAP was detected in the subsurface layer and in the stratified column prior to the mucilage event, which may be related to the very high abundance of Skeletonema marinoi, a diatom characteristic of the winter bloom in the region. We noted an order of magnitude higher concentration of SAP than typically observed in late winter/early spring, which serves as a precursor to the macroaggregation that occurs under certain environmental and oceanographic conditions in marine systems. Full article
(This article belongs to the Special Issue Characterization of Organic Matter in Marine and Freshwater Environment)
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14 pages, 2286 KiB  
Article
Interaction of Silica Nanoparticles with Microalgal Extracellular Polymers
by Petra Vukosav, Lea Pašalić, Danijela Bakarić, Darija Domazet Jurašin and Tea Mišić Radić
Water 2023, 15(3), 519; https://doi.org/10.3390/w15030519 - 28 Jan 2023
Cited by 1 | Viewed by 1605
Abstract
The properties of engineered nanoparticles (NPs) in the marine environment are influenced not only by the high ionic strength of seawater but also by the interaction of NPs with naturally occurring components of seawater, especially natural organic matter. The aim of this study [...] Read more.
The properties of engineered nanoparticles (NPs) in the marine environment are influenced not only by the high ionic strength of seawater but also by the interaction of NPs with naturally occurring components of seawater, especially natural organic matter. The aim of this study was to investigate the interaction of engineered silica nanoparticles (SiO2 NPs, diameter of 12 nm) with microalgal extracellular polymers (EPS) released by the marine diatom Cylindrotheca closterium. Dissolved organic carbon (DOC) content of the prepared EPS suspension (200 μg mL−1) used throughout the study was 3.44 mg C L−1. The incorporation of individual SiO2 NPs (height range 10–15 nm) and their nanoscale aggregates (height up to 25 nm, length up to 600 nm) into the EPS network was visualized by atomic force microscopy (AFM), whereas their molecular-level interaction was unraveled by the change in the signal of the Si-O group in their FTIR spectra. AFM imaging of C. closterium cells taken directly from the culture spiked with SiO2 NPs (10 μg mL−1) revealed that the latter are bound to the EPS released around the cells, predominantly as single NPs (height range 10–15 nm). Since AFM and dynamic and electrophoretic light scattering results demonstrated that SiO2 NPs dispersed in seawater without EPS showed enhanced aggregation (aggregate diameter of 990 ± 170 nm) and a 2.7-fold lower absolute zeta potential value compared to that measured in ultrapure water, our findings suggest that the presence of EPS biopolymers alters the aggregation affinity of SiO2 NPs in the marine environment. This might be of outmost importance during microalgal blooms when increased EPS production is expected because EPS, by scavenging and stabilizing SiO2 NPs, could prolong the presence of NPs in the water column and pose a threat to marine biota. Full article
(This article belongs to the Special Issue Characterization of Organic Matter in Marine and Freshwater Environment)
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10 pages, 1339 KiB  
Communication
Composition of Colloidal Organic Matter in Phytoplankton Exudates
by Katja Klun, Primož Šket, Alfred Beran, Ingrid Falnoga and Jadran Faganeli
Water 2023, 15(1), 111; https://doi.org/10.3390/w15010111 - 29 Dec 2022
Cited by 1 | Viewed by 1327
Abstract
The colloidal organic matter (COM) was isolated from the exudates of three cultured phytoplonkters, namely the chlophyte nanoflagellate Tetraselmis sp., the diatom Chaetoceros socialis and the dinoflagellate Prorocentrum minimum, from the Gulf of Trieste (northern Adriatic Sea). The isolation of COM was [...] Read more.
The colloidal organic matter (COM) was isolated from the exudates of three cultured phytoplonkters, namely the chlophyte nanoflagellate Tetraselmis sp., the diatom Chaetoceros socialis and the dinoflagellate Prorocentrum minimum, from the Gulf of Trieste (northern Adriatic Sea). The isolation of COM was performed by ultrafiltration with molecular weight cut-off membranes of 5 kDa and final desalinisation by dialysis. The composition of the COM was characterised using C elemental analysis and 1H NMR spectroscopy and compared with COM isolated from a marine sample from the same area (Gulf of Trieste). By using 1H NMR spectroscopy, it was possible to semi-quantitatively determine the concentrations of the main biochemical constituents present in the COM samples. The results showed that the phytoplankton COM was predominantly composed of polysaccharides, with minor contributions from proteins and especially lipids. Therefore, the phytoplankton COM mainly contributes to the marine COM pool in the polysaccharide fraction and less in the protein and lipid fractions. Full article
(This article belongs to the Special Issue Characterization of Organic Matter in Marine and Freshwater Environment)
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22 pages, 1913 KiB  
Article
Dissolved Trace Metals and Organic Matter Distribution in the Northern Adriatic, an Increasingly Oligotrophic Shallow Sea
by Abra Penezić, Blaženka Gašparović, Vlado Cuculić, Slađana Strmečki, Tamara Djakovac and Marina Mlakar
Water 2022, 14(3), 349; https://doi.org/10.3390/w14030349 - 25 Jan 2022
Cited by 5 | Viewed by 2751
Abstract
We report a monthly distribution of Zn, Cd, Pb, Cu, Ni and Co, biologically relevant trace metals (TMs), within one year, in the productive surface layer at two stations with different trophic characters in the northern Adriatic (NA). The TM data was accompanied [...] Read more.
We report a monthly distribution of Zn, Cd, Pb, Cu, Ni and Co, biologically relevant trace metals (TMs), within one year, in the productive surface layer at two stations with different trophic characters in the northern Adriatic (NA). The TM data was accompanied by a multivariable dataset, including dissolved organic carbon (DOC), surface-active organic substances (SAS), nitrogen-containing polymeric organic material (N-POM), nutrients, pH, dissolved O2, chlorophyll a (Chl a), seawater temperature, and the Po River discharge rate. At the eu- to mesotrophic station 108, the concentrations of dissolved TMs were 5–116 nM for Zn, 0.04–0.18 nM for Cd, 0.05–0.63 nM for Pb, 3–17 nM for Cu, 4–11 nM for Ni, and 0.2–1.2 nM for Co, while at the oligotrophic station 107, they were 6–224 nM for Zn, 0.03–0.16 nM for Cd, 0.05–1.25 nM for Pb, 3–17 nM for Cu, 4–19 nM for Ni, and 0.1–0.7 nM for Co. The characterization of organic matter (OM) in conjunction with the analysis of correlations with TMs indicated that the OM–TMs interactions differed between the two stations; namely, the freshly produced OM detected at station 108 was probably involved in the complexation of Cu, Co, Cd, and Ni, whereas at station 107, such complexation processes were not present. Accumulation of DOC was observed during the summer months at both stations. Our results present a significant contribution to biogeochemical studies in the NA by focusing on the complexity of TM–OM interactions, which is a prerequisite for interpretation of their responses to local and global changes. Full article
(This article belongs to the Special Issue Characterization of Organic Matter in Marine and Freshwater Environment)
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16 pages, 8308 KiB  
Article
Characterization of Marine-Surface-Dissolved Organic Matter via Amino Acid Enantiomers and Its Implications Based on Diel and Seasonal Observations
by Zhuo-Yi Zhu, Ying-Chun Zhou, Wen-Chao Ma, Ying Wu, Ming Li, Su-Mei Liu, Xue-Wei Xu and Meng Zhou
Water 2021, 13(5), 685; https://doi.org/10.3390/w13050685 - 3 Mar 2021
Viewed by 2352
Abstract
Due to the essential roles of dissolved organic matter (DOM) in both microbiol food loop and marine carbon cycling, changes in marine DOM composition have an important impact on the marine ecosystem and carbon cycling. In October 2014 and June 2015, two field [...] Read more.
Due to the essential roles of dissolved organic matter (DOM) in both microbiol food loop and marine carbon cycling, changes in marine DOM composition have an important impact on the marine ecosystem and carbon cycling. In October 2014 and June 2015, two field investigations for the DOM in the upper 200 m were conducted in the slope region of the northern South China Sea to characterize the DOM composition via amino acid enantiomers. In June, our sampling locations were under upwelling impact induced by an eddy-pair event, whereas in October there were no eddies. High-frequency sampling (a few hours interval) over 24 h reveals that the variability of the amino acid carbon yield (min. 0.2%) and the D/L alanine ratio (min. 0.02) is larger than its corresponding analytical and propagated errors, suggesting solid short-term changes for these two molecular-based indicators. Section samples from June showed a lower D/L alanine ratio (0.43 vs. 0.53) and a GABA mol% (1.0% vs. 1.6%) relative to the section samples from October, suggesting that DOM in June is more fresh (less degraded) compared to that in October. A higher serine mol% (19.5% vs. 13.2%) and lower D/L serine ratio (0.06 vs. 0.24) from the diel observation in June relative to October further indicates that phytoplankton, rather than bacteria, plays an more important role in DOM composition alternation. This is consistent with the higher phytoplankton biomass found in June, promoted by the eddy-pair. Full article
(This article belongs to the Special Issue Characterization of Organic Matter in Marine and Freshwater Environment)
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