scholarly journals Aerosol inputs affect the optical signatures of dissolved organic matter in NW Mediterranean coastal waters

2016 ◽  
Vol 80 (4) ◽  
pp. 437 ◽  
Author(s):  
E. Denisse Sánchez-Pérez ◽  
Isabel Marín ◽  
Sdena Nunes ◽  
Fran L. Aparicio ◽  
Laura Fernández-González ◽  
...  

Aeolian inputs of organic and inorganic nutrients to the ocean are important as they can enhance biological production in surface waters, especially in oligotrophic areas like the Mediterranean. The Mediterranean littoral is particularly exposed to both anthropogenic and Saharan aerosol depositions on a more or less regular basis. During the last few decades experimental studies have been devoted to examining the effect of inorganic nutrient inputs from dust on microbial activity. In this study, we performed experiments at two different locations of the NW Mediterranean, where we evaluated the changes in the quality and quantity of dissolved organic matter due to atmospheric inputs of different origin (Saharan and anthropogenic) and its subsequent transformations mediated by microbial activities. In both experiments the humic-like and protein-like substances, and the fluorescence quantum yield increased after addition. In general, these changes in the quality of dissolved organic matter did not significantly affect the prokaryotes. The recalcitrant character of the fluorescent dissolved organic matter (FDOM) associated with aerosols was confirmed, as we found negligible utilization of chromophoric compounds over the experimental period. We framed these experiments within a two-year time series data set of atmospheric deposition and coastal surface water analyses. These observations showed that both Saharan and anthropogenic inputs induced changes in the quality of organic matter, increasing the proportion of FDOM substances. This increase was larger during Saharan dust events than in the absence of Saharan influence.

2020 ◽  
Vol 8 (11) ◽  
pp. 911
Author(s):  
Francesca Iuculano ◽  
Carlos M. Duarte ◽  
Jaime Otero ◽  
Xosé Antón Álvarez-Salgado ◽  
Susana Agustí

Posidonia oceanica is a well-recognized source of dissolved organic matter (DOM) derived from exudation and leaching of seagrass leaves, but little is known about its impact on the chromophoric fraction of DOM (CDOM). In this study, we monitored for two years the optical properties of CDOM in two contrasting sites in the Mallorca Coast (Balearic Islands). One site was a rocky shore free of seagrass meadows, and the second site was characterized by the accumulation of non-living seagrass material in the form of banquettes. On average, the integrated color over the 250–600 nm range was almost 6-fold higher in the beach compared with the rocky shore. Furthermore, the shapes of the CDOM spectra in the two sites were also different. A short incubation experiment suggested that the spectral differences were due to leaching from P. oceanica leaf decomposition. Furthermore, occasionally the spectra of P. oceanica was distorted by a marked absorption increase at wavelength < 265 nm, presumably related to the release of hydrogen sulfide (HS−) associated with the anaerobic decomposition of seagrass leaves within the banquettes. Our results provide the first evidence that P. oceanica is a source of CDOM to the surrounding waters.


2016 ◽  
Vol 67 (9) ◽  
pp. 1313 ◽  
Author(s):  
Richard L. Miller ◽  
Matthew M. Brown ◽  
Ryan P. Mulligan

Rivers are major conduits for the transport of allochthonous dissolved organic matter (DOM) to the ocean in coupled land–coastal systems. DOM can regulate biogeochemical processes and affect water quality, depending on the concentration and quality of DOM. By using spectral parameters calculated from chromophoric dissolved organic matter (CDOM) ultraviolet-visible absorption spectra, along with dissolved organic carbon (DOC) concentrations, we examined the input and change in the amount and quality of DOM in surface waters of the lower Neuse River and upper–middle regions of the Neuse Estuary following a major rainfall (30cm in 1 day) associated with Hurricane Irene (2011). CDOM and DOC nearly tripled in the 3 days following the storm. Although a strong linear relationship was observed between DOC and CDOM absorption coefficient at 350nm (R2=0.85), a higher fraction of non-chromophoric DOC to CDOM was observed during the rising river discharge. The spectral slope at 275–295nm and the slope ratio (275–295:350–400nm) indicated a shift from higher to lower molecular-weight DOM as it transited through the estuary, probably as a result of photodegradation. The present study demonstrated the utility of using CDOM spectral parameters for examining the flux and transformation of DOM in coastal waters following major rain events.


2009 ◽  
Vol 56 (5) ◽  
pp. 672-685 ◽  
Author(s):  
Stuart J. Goldberg ◽  
Craig A. Carlson ◽  
Dennis A. Hansell ◽  
Norm B. Nelson ◽  
David A. Siegel

2009 ◽  
Vol 83 (4) ◽  
pp. 539-549 ◽  
Author(s):  
Sofia Loureiro ◽  
Esther Garcés ◽  
Margarita Fernández-Tejedor ◽  
Dolors Vaqué ◽  
Jordi Camp

2013 ◽  
Vol 98 (2) ◽  
pp. 931-943 ◽  
Author(s):  
Benjamin Horemans ◽  
Johanna Vandermaesen ◽  
Philip Breugelmans ◽  
Johan Hofkens ◽  
Erik Smolders ◽  
...  

2016 ◽  
Author(s):  
Harshad Kulkarni ◽  
◽  
Natalie Mladenov ◽  
Debashis Chatterjee ◽  
Saugata Datta

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