Seasonal changes in the chemical composition and reactivity of dissolved organic matter at the land-ocean interface of a subtropical river

Yang, Liyang; Cheng, Qiong; Zhuang, Wei; Wang, Hui; Chen, Wei

doi:10.1007/s11356-019-05700-2

Cited by 46 publications

(24 citation statements)

References 58 publications

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“…Although no significant change in the DOC concentration was recorded, a high variability in the S 275-295 was observed. This observation agrees with recent finding where great variability in S 275-295 was shown during the photodegradation of estuarine waters in tropical regions from different seasons [61]. This pattern projected with the appearance of a peak maximum toward the end of the experiment in the irradiated samples, and around the middle of the experiment in the dark control samples (Fig.…”

Section: Profiles Of Doc and Slope Coefficientsupporting

confidence: 93%

Impact of UV radiation on DOM transformation on molecular level using FT-ICR-MS and PARAFAC

Miranda

Osterholz

Giebel

et al. 2020

Spectrochimica Acta Part A: Molecular and Biomolecular Spectros

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Dissolved organic matter (DOM) is an omnipresent constituent of natural water bodies. Reuse and transformation of DOM compounds in the water column is driven by physicochemical and biological processes leading to the production of refractory DOM. Typically, breakdown of DOM chemical compounds into smaller or more condensed fragments is triggered by ultraviolet (UV) radiation. Here, we present a study on the photodegradation of DOM produced during an incubation experiment with a natural microbial community. At the end of the first incubation without UV irradiation, the samples from 3 mesocosms were filtered to remove microbes and particles and continuously exposed to UV radiation (280-365 nm). We investigated DOM in depth via monitoring of dissolved organic carbon (DOC) concentrations, DOM molecular characterization by Fourier-Transform Ion Cyclotron Resonance Mass Spectrometry (FT-ICR-MS) and excitation emission matrix spectroscopy (EEMS). Analysis of variance indicated no significant differences in the DOC concentration between treatments. Main peaks in the fluorescent DOM (FDOM) were photo-bleached by UV radiation, and an increase in the fluorescent intensity of selected peaks was observed on irradiated samples toward the end of the experiment. Parallel factor analysis (PARAFAC) indicated the presence of three main components in all treatments: C1 (Marine humic M), C2 (Bacterial produced humic C), C3 (Tyrosine), and an additional component in the dark incubation of mesocosm 3, C4 (Tryptophan). Despite an intensive filtration protocol through 0.7, 0.2 and 0.1 μm filters, low bacterial abundances were determined (b2.5 × 10 −3 cells mL −1 ). We observed a direct correlation between structural indices and the intensity of PARAFAC components. Average double bond equivalent and aromaticity were strongly positively correlated with PARAFAC components C1 and C2 for one or more mesocosm. Moreover, FT-ICR-MS showed that under the tested conditions, the refractory character of the DOM assessed as the similarity to a deep ocean DOM reference did not increase on molecular level. Thus, mechanisms other than photochemical transformations of relatively recent DOM are likely necessary to facilitate long-term stability of DOM in the oceans.

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Section: Profiles Of Doc and Slope Coefficientsupporting

confidence: 93%

Impact of UV radiation on DOM transformation on molecular level using FT-ICR-MS and PARAFAC

Miranda

Osterholz

Giebel

et al. 2020

Spectrochimica Acta Part A: Molecular and Biomolecular Spectros

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“…In addition, riverine input due to heavy rainfalls during spring lowered the seawater In May, the residuals of the Min-Zhe coastal current drove low temperature seawater flow southwards into the Taiwan Strait, leading to temperature decreases gradually from south to north [39]. In addition, riverine input due to heavy rainfalls during spring lowered the seawater temperature and salinity but increased DIN concentrations (Figure 6) [18]. As a consequence, eurythermal and euryhaline species dominated in spring, such as P. donghaiense, S. trochoidea, Coscinodiscus, and so on.…”

Section: Discussionmentioning

confidence: 99%

“…Based on our data and previous studies, we propose a conceptual model for the effects of environmental drivers on a shift from dinoflagellates in May to diatoms in July in Taiwan Strait (Figure 6). Riverine input decreases seawater salinity to be 29.0-33.0 psu and increases DIN concentration [18,39]. Once seawater temperature increases to 17.0-23.0 • C and DIN concentration is higher than 2.0 µmol L -1 , dinoflagellate cells grow quickly, and then blooms occur in May and reach higher numbers when the more nitrate (but also phosphate) is available [12,22,53]; this increases seawater pH value and DO concentration and reduces nutrient concentrations.…”

Section: Discussionmentioning

confidence: 99%

“…The Taiwan Strait is located in Southeast China and the transition between the South China Sea (SCS) and the East China Sea (ECS). In spring, freshwater in the largest estuary in Fujian province (Minjiang estuary) flows northwestwards and brings nutrients to the Taiwan Strait [18]. In summer, the southwest monsoon brings warm water from SCS to the Taiwan Strait rising seawater temperature and drives deep water upwelling off the Fujian coast increasing nutrient concentrations and phytoplankton biomass in the Taiwan Strait [19].…”

Section: Introductionmentioning

confidence: 99%

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Spatial Distribution of Phytoplankton Community Composition and Their Correlations with Environmental Drivers in Taiwan Strait of Southeast China

Zhang

Jin-zhu

et al. 2020

Diversity

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Large-scale dinoflagellate blooms have appeared in recent decades in the Taiwan Strait, Southeast China. To study spatial variability of phytoplankton community composition, physical and chemical environmental drivers in surface seawater of the Taiwan Strait, we conducted cruises in May and July 2019. Cell numbers of dinoflagellates were significantly higher than that of diatoms in most sampling stations during the cruise in May, whereas diatoms were the major contributor to autotrophic biomass in July. Phytoplankton community shifted from a dinoflagellate- and diatom-dominated system in May to diatom dominance in July. The dominant phytoplankton species (genera) were the harmful algal bloom dinoflagellates Prorocentrum donghaiense and Scrippsiella trochoidea and the diatoms Coscinodiscus in May, and Rhizosolenia, Pseudo-nitzschia, and Guinardia in July. Cell densities of dinoflagellates and P. donghaiense reduced exponentially with increasing seawater temperature and salinity and decreasing dissolved inorganic nitrogen (DIN) concentrations. Based on the results of our work and previous studies, it becomes obvious that harmful dinoflagellate blooms are likely to be a major component of the planktonic food web in the Taiwan Strait at a temperature of 17.0–23.0 °C, a salinity of 29.0–33.0 psu, and a DIN concentration higher than 2.0 μmol L–1.

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“…Long‐term perturbation of El Niño events on watersheds makes it crucial to deploy effective monitoring tools that provide reliable, continuous, and high‐frequency DOM measurements, such as in situ optical fluorescent DOM (FDOM) sensors (Saraceno et al, 2009; Wymore et al, 2018). The excitation‐emission wavelength of current commercial FDOM sensors represents humic‐like FDOM (FDOM H ) components, which are considered a good proxy for the terrestrial DOM fraction (Coble, 1996; Guo et al, 2014; Yang et al, 2019). In many aquatic systems, FDOM is highly correlated with DOC (Guo et al, 2011; Webb et al, 2018), suggesting that FDOM sensors provide an effective tool for monitoring watershed DOM dynamics and export (Shultz et al, 2018; Wymore et al, 2018).…”

Section: Introductionmentioning

confidence: 99%

El Niño‐Driven Dry Season Flushing Enhances Dissolved Organic Matter Export From a Subtropical Watershed

Wu²,

et al. 2020

Geophysical Research Letters

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The 2015/2016 super El Niño event resulted in a positive precipitation anomaly during dry seasons in the Jiulong River watershed, southeast China. Four years (2014-2017) of high frequency, in situ humic-like fluorescent DOM (FDOM H) data in the Jiulong Estuary were coupled with extrapolation to a freshwater end-member FDOM H concentration and river discharge data to estimate riverine FDOM H export. The wetter El Niño dry season was followed by lower FDOM H export during the subsequent wet season. Furthermore, in the dry season after El Niño reached its strongest phase, a 90-187% increase in FDOM H export occurred. If widespread, this pattern suggests El Niño events may enhance export of FDOM H from south China rivers in dry seasons resulting in seasonal and annual shunting of the terrestrial DOM export, modulating coastal carbon cycling. This study highlights the need to incorporate climate-driven regulation patterns on DOM transport across the land-ocean interface.

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Seasonal changes in the chemical composition and reactivity of dissolved organic matter at the land-ocean interface of a subtropical river

Cited by 46 publications

References 58 publications

Impact of UV radiation on DOM transformation on molecular level using FT-ICR-MS and PARAFAC

Impact of UV radiation on DOM transformation on molecular level using FT-ICR-MS and PARAFAC

Spatial Distribution of Phytoplankton Community Composition and Their Correlations with Environmental Drivers in Taiwan Strait of Southeast China

El Niño‐Driven Dry Season Flushing Enhances Dissolved Organic Matter Export From a Subtropical Watershed

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