Photochemical and microbial alterations of DOM spectroscopic properties in the estuarine system Ria de Aveiro

Santos, Luísa; Santos, Eduarda B.H.; Dias, João Miguel; Almeida, Adelaide

doi:10.1039/c4pp00005f

Cited by 28 publications

(20 citation statements)

References 69 publications

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“…Comparable trends have been found by Zhang et al (2007b) in the Yunnan Plateau lakes. E2 : E3 ratio variations found in this study have also been shown in previous studies (Santos et al, 2014;Helms, 1998). In coastal waters E2 : E3 values are typically within the range 8.70±1.4 and 13.5±1.6 (nearshore -offshore in Georgia Bight; Helms et al, 2008).…”

Section: Dynamics Of Dissolved Organic Carbonsupporting

confidence: 92%

Spatio-seasonal variability of chromophoric dissolved organic matter absorption and responses to photobleaching in a large shallow temperate lake

et al. 2017

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Abstract. The development and validation of remotesensing-based approaches for the retrieval of chromophoric dissolved organic matter (CDOM) concentrations requires a comprehensive understanding of the sources and magnitude of variability in the optical properties of dissolved material within lakes. In this study, spatial and seasonal variability in concentration and composition of CDOM and the origin of its variation was studied in Lake Balaton (Hungary), a large temperate shallow lake in central Europe. In addition, we investigated the effect of photobleaching on the optical properties of CDOM through in-lake incubation experiments. There was marked variability throughout the year in CDOM absorption in Lake Balaton (a CDOM (440) = 0.06-9.01 m −1 ). The highest values were consistently observed at the mouth of the main inflow (Zala River), which drains humic-rich material from the adjoining Kis-Balaton wetland, but CDOM absorption decreased rapidly towards the east where it was consistently lower and less variable than in the westernmost lake basins. The spectral slope parameter for the interval of 350-500 nm (S CDOM (350-500)) was more variable with increasing distance from the inflow (observed range 0.0161-0.0181 nm −1 for the mouth of the main inflow and 0.0158-0.0300 nm −1 for waters closer to the outflow). However, spatial variation in S CDOM was more constant exhibiting a negative correlation with a CDOM (440). Dissolved organic carbon (DOC) was strongly positively correlated with a CDOM (440) and followed a similar seasonal trend but it demonstrated more variability than either a CDOM or S CDOM with distance through the system. Photobleaching resulting from a 7-day exposure to natural solar UV radiation resulted in a marked decrease in allochthonous CDOM absorption (7.04 to 3.36 m −1 , 42 % decrease). Photodegradation also resulted in an increase in the spectral slope coefficient of dissolved material.

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Section: Dynamics Of Dissolved Organic Carbonsupporting

confidence: 92%

Spatio-seasonal variability of chromophoric dissolved organic matter absorption and responses to photobleaching in a large shallow temperate lake

et al. 2017

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“…These patterns are consistent with depletion processes taking place in the SML environment through the photochemical processing of organic material. Negative correlations between the SML HIX and exposure to solar radiation have been reported by Santos et al (2014), and associated with a low content of fluorophore groups corresponding to humic-like fractions . Our observations are consistent with the loss of fluorescent intensity from FDOM compounds due to photochemical degradation in the SML.…”

Section: Influence Of Solar Radiation On Hixmentioning

confidence: 79%

“…FDOM decomposition due to interaction with solar radiation is known as photobleaching, a process that provides a source of smaller compounds increasing the availability of carbon substrates in the ocean (Santos et al, 2014). Besides photochemical decomposition, high exposure to solar radiation, specifically to the more energetic wavelengths of ultraviolet (UV) radiation, leads to the growth of unique microbial communities with specific survival strategies for the harsh environment of the SML; e.g., the release of sun blocker-like compounds (Gao and GarciaPichel, 2011).…”

Section: Research Articlementioning

confidence: 99%

“…Although UV radiation is a minor component of solar radiation, it is a main driver in photochemical transformations within the SML. The relationship between UV radiation and FDOM photodegradation is well documented: the shorter and more energetic UV wavelengths can degrade complex molecules of DOM, in the process enhancing microbial reprocessing of DOM in the oceans (Vecchio and Blough, 2002;Vähätalo and Wetzel, 2004;Santos et al, 2014;Helms et al, 2014). GHI refers to the total amount of shortwave radiation received from above by a surface horizontal to the ground.…”

Section: Solar and Photosynthetically Available Radiationmentioning

confidence: 99%

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Influence of solar radiation on biogeochemical parameters and fluorescent dissolved organic matter (FDOM) in the sea surface microlayer of the southern coastal North Sea

Miranda

Mustaffa²,

Robinson³

et al. 2018

Elem Sci Anth

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Miranda, ML, 2018 Influence of solar radiation on biogeochemical parameters and fluorescent dissolved organic matter (FDOM) in the sea surface microlayer of the southern coastal North Sea. Elem Sci Anth, 6: 15. DOI: https://doi.org/10.1525/elementa.278 IntroductionThe sea surface microlayer (SML), defined here as the upper 50-100 µm of the water column, is an important habitat of the ocean where air-sea exchange and transformation processes take place (Wurl et al., 2016). Compounds from natural and anthropogenic sources accumulate within the SML enhancing their concentrations in comparison with the water column. The relative abundance of organic matter within the SML provides a diverse range of substrates for the growth of surface-dwelling heterotrophic microorganisms (Reinthaler et al., 2008).Among the sources of organic substrates in the SML is the dissolved organic matter (DOM; (Cunliffe et al., 2013). DOM is a large mix of organic compounds, mainly the products of biodegradation processes, and is comprised of carbohydrates, proteins, lignin, organic acids, and humic substances (Zhi et al., 2015). Two optically active components of DOM are known: the colored dissolved organic matter (CDOM) and the fluorescent dissolved organic matter (FDOM). CDOM includes materials that are capable of absorbing light, while FDOM refers to the mix of compounds that can absorb light, emitting fluorescence at certain wavelengths according to the presence of diverse chemical functional groups (Coble, 1996;Stedmon and Nelson, 2015). The SML is a highly dynamic and complex habitat in which several processes transform the DOM. These transformations are triggered by the environmental factors of wind, solar radiation, and light availability, as well as by microbial activity (Cunliffe et al., 2013).Light availability in the water column is controlled by two physical processes, absorption and scattering (Kirk, We investigated the influence of solar radiation on biogeochemical parameters of the sea surface microlayer (SML), including the spectroscopic composition of FDOM, and biotic and abiotic parameters. We calculated the humification index, biological index, and recently produced material index from the ultraviolet spectra to characterize the dynamic environment of the SML. The humification index ranged from 4 to 14 in the SML and 14 to 22 in underlying water (ULW). An inverse relation for this index as a function of solar radiation was observed, indicating photochemical decomposition of complex molecules present in fluorescent dissolved organic matter (FDOM). The biological index (along Leg 2) ranged from 1.0 to 2.0 for the SML and 1.0 to 1.5 for ULW. The index for recently produced material ranged from 0.25 to 0.8 for the SML and 0.5 to 1.0 for ULW. The FDOM enrichment process of the SML was influenced by the photochemical decomposition of highly aromatic-like fluorophores, as indicated by the calculated indices. Fluorescence intensity increased for humic C peaks (>0.5 Raman units) in the North Sea samples and for humic M peaks (>1....

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“…However, photochemical transformations likely represent key degradation pathways for terrestrial DOM in alpine and sub-alpine lakes due to the intensive solar irradiation at higher altitudes (Sommaruga, 2001). The photodegradation of DOM results in the alteration of its molecular structure and mineralization of DOC to CO 2 (Kaiser and Sulzberger, 2004;Piccini et al, 2009;Osburn et al, 2011;Santos et al, 2014). The overall effects of photodegradation, depend largely on the irradiation conditions and the origin and composition of the DOM exposed to sunlight (Stedmon and Markager, 2005b;Zhang et al, 2013).…”

Section: Introductionmentioning

confidence: 99%

Photochemical reactivities of dissolved organic matter (DOM) in a sub-alpine lake revealed by EEM-PARAFAC: An insight into the fate of allochthonous DOM in alpine lakes affected by climate change

Zhang

Chen

et al. 2016

Science of The Total Environment

101

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Due to climate change, tree line advance is occurring in many alpine regions. Within the next 50 to 100years, alpine lake catchments are expected to develop increased vegetation cover similar to that of sub-alpine lake catchments which currently exist below the tree line. Such changes in vegetation could trigger increased allochthonous DOM inputs to alpine lakes. To understand the fate of allochthonous DOM in alpine lakes impacted by climate change, the photochemical reactivity of DOM in sub-alpine Lake Tiancai (located 200m below the tree line) was investigated by excitation emission matrix fluorescence combined with parallel factor analysis (EEM-PARAFAC) and UV-Vis spectra analysis. With photo-exposure, a decrease in apparent DOM molecular weight was observed and 32% DOM was photomineralized to CO2. Interestingly, the aromaticity of DOM increased after photodegradation, as evidenced by increases in both the specific UV absorbance at 254nm (SUVA254) and the humification index (HIX). Five EEM-PARAFAC components were identified, including four terrestrially-derived substances (C1, C2, C3 and C4; allochthonous) and one tryptophan-like substance (C5; autochthonous). Generally, allochthonous DOM represented by C2 and C3 exhibited greater photoreactivity than autochthonous DOM represented by C5. C4 was identified as a possible photoproduct with relatively high aromaticity and photorefractive tendencies and contributed to the observed increase in SUVA254 and HIX. UV light facilitated the photodegradation of DOM and had the greatest effect on the removal of C3. This study provides information on the transformation of EEM-PARAFAC components in a sub-alpine lake, which is important in understanding the fate of increased allochthonous DOM inputs to alpine lakes impacted by climate change.

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Photochemical and microbial alterations of DOM spectroscopic properties in the estuarine system Ria de Aveiro

Cited by 28 publications

References 69 publications

Spatio-seasonal variability of chromophoric dissolved organic matter absorption and responses to photobleaching in a large shallow temperate lake

Spatio-seasonal variability of chromophoric dissolved organic matter absorption and responses to photobleaching in a large shallow temperate lake

Influence of solar radiation on biogeochemical parameters and fluorescent dissolved organic matter (FDOM) in the sea surface microlayer of the southern coastal North Sea

Photochemical reactivities of dissolved organic matter (DOM) in a sub-alpine lake revealed by EEM-PARAFAC: An insight into the fate of allochthonous DOM in alpine lakes affected by climate change

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