Colloidal toxic trace metals in urban riverine and estuarine waters of Yantai City, southern coast of North Yellow Sea

The environmental characteristics of colloidal toxic trace metals Cd, Cu and Pb in riverine and estuarine waters collected from two urban rivers of Yantai City in eastern China, the Guangdang and Xin'an Rivers, were investigated using a modified centrifugal ultrafiltration (CUF) method in conjunction with acid extraction and inductively coupled plasma mass spectrometry. The target metals in dissolved pool were divided into four CUF fractions, i.e. <1 kDa, 1-3 kDa, 3-10 kDa and 10 kDa-0.2 mu m, and the results showed that colloidal Cd, Cu and Pb were dominated by 1-10 kDa (1-3 and 3-10 kDa), 1-3 kDa and 10 kDa-0.2 lm fractions, respectively. The coagulation/flocculation of low-molecular-weight (1-10 kDa) colloidal Cd and Cu in the estuaries was obvious and strong, while the enrichment of dissolved Pb in the 10 kDa-0.2 lm fraction may be mainly related to its biogeochemical interactions with Fe-oxides, which is easy to occur in macromolecular colloids. In addition, the actual molecular weight cutoffs (MWCOs) of the three used CUF units with nominal MWCOs of 1, 3 and 10 kDa were determined to be 4.9, 8.5 and 33.9 kDa, respectively, indicating that membrane calibration is essential for explaining the actual fraction of dissolved trace metals and verifying the integrity of ultrafiltration membrane. Overall, the results in this study provide a further understanding of the heterogeneity in biogeochemical features, migration and fate of toxic trace metals in aquatic ecosystems, especially that of the river-sea mixing zone. (C) 2019 Elsevier B.V. All rights reserved

The contrast in suspended particle dynamics at surface and near bottom on the river-dominated northern South China Sea shelf in summer: implication on physics and biogeochemistry coupling

To understand the process-response relations among physical forcing and biogeochemical properties of suspended particles (SPs) in the river-dominated northern South China Sea shelf, a 5-day shipboard observation was conducted at a fixed location on the dispersal pathway of the Zhujiang (Pearl) River plume (ZRP) in the summer of 2016. Instrumented moorings were deployed near the sampling site to record the flow and wave fields every 10 minutes. Hydrographic properties were measured hourly to identify different water masses. Water and SPs samples at the surface (3 m) and near the bottom (3 m above the bed) were taken every 3 h for the analyses of nutrients, chlorophyll-a (Chl-a), and particulate organic matter (POM including POC, PN, and δ13CPOC). Meanwhile, the grain-size composition of SPs and seafloor sediment were also analyzed. Results showed that monsoon winds drove cold upwelling and ZRP waters at the surface. Both the upwelling and ZRP regimes contained newly produced marine phytoplankton based on low POC/Chl-a ratio (PC ratio) and enriched δ13CPOC. However, SPs in the ZRP regime were smaller (&lt;153 µm), having denser particle bulk density, and less enriched δ13CPOC, indicating different bio-communities from the upwelling regime. EOF analysis of the surface data suggested that mixing processes and the dispersal of the ZRP regime were mainly controlled by far-field storm winds, tidal modulation, and strength of mixing. On the other hand, a bottom nepheloid layer (BNL) was observed, mainly consisting of SPs&lt;63 μm with higher bulk density than SPs at the surface. POM in the BNL was degraded and δ13CPOC-depleted according to the PC ratio and δ13CPOC. EOF analysis of the near-bottom data indicated that the dominant physical processes influencing the biogeochemical properties of SPs in the BNL were jointly the upwelling-associated lateral transport (first order) and tide-related resuspension (second order). Our study identified the contrast between the surface and near-bottom regimes with the coupling patterns among physical forcing and physiochemical properties of SPs using good constraints on particle dynamics and particle sources

Absorption and fluorescence of dissolved organic matter in submarine hydrothermal vents off NE Taiwan

National Natural Science Foundation of China [40810069004]; Xiamen University [211-III]; National Science Council of Taiwan [NSC 98-2621-M-110-001-MY3]; "Aim for the Top" University Program of TaiwanThe role of hydrothermal vents as either a source or a sink for chromophoric and fluorescent dissolved organic matter (CDOM and FDOM) in the oceans is unknown, since DOM absorption and fluorescence have not been reported for submarine hydrothermal vents. Water samples were collected from two shallow submarine hydrothermal vents off NE Taiwan, the white vent and the yellow vent, during two cruises in August, 2010. Absorption and excitation-emission-matrix fluorescence spectroscopy were used to characterize the optical properties of DOM from such extremely special environments. The absorption coefficients at wavelength 300 nm (a(300)) were much higher at the white vent mouth and 1 m below it (2.52 +/- 0.88 m(-1)) than in the background (0.34 +/- 0.12 m(-1)). This indicated that the white vent was a source of CDOM for seawater. Three fluorescent components were identified using parallel factor analysis: humic-like C1, tyrosine-like C3, and C2 as a combination of tryptophan-like and marine humic-like components. Both C1 and C3 (but not C2) had their highest fluorescence intensity at the white vent mouth and 1 m below it, suggesting the role of the vent as a source for both humic-like and tyrosine-like DOM. Samples from the yellow vent mouth also had a higher 0300 than the ambient seawater in our first cruise, but had fluorescence intensities of C(1-3) similar to the ambient seawater. Overall, the low humification index (HIX: 1.40 +/- 0.30) and the high autochthonous index (BIX: 1.27 +/- 0.63) indicated that the DOM likely had low humic contents and was mainly autochthonous of biological or bacterial origin in the study area. A biplot of HIX and BIX showed that DOM from the hydrothermal vents had a characteristic similar to terrestrial cave and spring waters, but was distinct from isolated humics. (C) 2011 Elsevier B.V. All rights reserved

The influence of summer hypoxia on sedimentary phosphorus biogeochemistry in a coastal scallop farming area, North Yellow Sea

In situ field investigations coupled with laboratory incubations were employed to explore the surface sedimentary phosphorus (P) cycle in a mariculture area adjacent to the Yangma Island suffering from summer hypoxia in the North Yellow Sea. Five forms of P were fractionated, namely exchangeable P (Ex-P), iron-bound P (Fe-P), authigenic apatite (Ca-P), detrital P (De-P) and organic P (OP). Total P (TP) varied from 13.42 to 23.88 mu mol g(-1) with the main form of inorganic P (IP). The benthic phosphate (DIP) fluxes were calculated based on incubation experiments. The results show that the sediment was an important source of P in summer with similar to 39% of the bioavailable P (Bio-P) recycled back into the water column. However, the sediment acted a sink of P in autumn. The benthic DIP fluxes were mainly controlled by the remobilizing of Fe-P, Ex-P and OP under contrasting redox conditions. In August (hypoxia season), similar to 0.92 mu mol g(-1) of Fe-P and similar to 0.52 mu mol g(-1) of OP could be transformed to DIP and released into water, while similar to 0.36 mu mol g(-1) of DIP was adsorbed to clay minerals. In November (non-hypoxia season), however, similar to 0.54 mu mol g(-1) of OP was converted into DIP, while similar to 0.55 mu mol g(-1) and similar to 0.28 mu mol g(-1) of DIP was adsorbed to clay minerals and bind to iron oxides. Furthermore, scallop farming activities also affected the P mobilization through biological deposition and reduced hydrodynamic conditions. The burial fluxes of P varied from 11.67 to 20.78 mu mol cm(-2) yr(-1) and its burial efficiency was 84.7-100%, which was consistent with that in most of the marginal seas worldwide. This study reveals that hypoxia and scallop farming activities can significantly promote sedimentary P mobility, thereby causing high benthic DIP flux in coastal waters. (C) 2020 Elsevier B.V. All rights reserved

Diurnal variations of surface seawater pCO(2) in contrasting coastal environments

We examined diurnal variations of surface seawater pCO(2) (partial pressure of CO2) in a suite of coastal marine environmental systems in the vicinity of the South China Sea (SCS) from inshore and nearshore settings in Xiamen Bay, Shenhu Bay, and the southwestern Taiwan Strait, to offshore sites in the basin and on the slope of the northern South China Sea as well as in a coral reef system at Xisha Islands in the middle of the SCS. There were significant diurnal changes of surface pCO(2), ranging from 1.0 Pa to 1.6 Pa (10-16 mu atm) in the offshore and oligotrophic sites similar to 4.1 Pa in the Taiwan Strait, 5.1-15.2 Pa in Xiamen Bay and Shenhu Bay, to as high as 60.8 Pa in the coral reef system at Xisha Islands. Processes that modulate these pCO(2) diurnal variations were temperature, tide or current, and biological controls. Temperature was a major driver of the pCO(2) diurnal variability in the oligotrophic regions, while tidal effects were important in the nearshore. In the coral reef system, biological metabolism dominated variability. Diurnal variability could have a potentially important implication on the estimate of air-sea CO2 fluxes, which may result in an uncertainty of +/- 0.48-0.77 mmol C m(-2) d(-1) for the offshore sites in the SCS. Such uncertainties were larger in nearshore settings.National Science Foundation of China [90211002, 40490264, 40521003

The Interplay between NF-kappaB and E2F1 Coordinately Regulates Inflammation and Metabolism in Human Cardiac Cells

Pyruvate dehydrogenase kinase 4 (PDK4) inhibition by nuclear factor-κB (NF-κB) is related to a shift towards increased glycolysis during cardiac pathological processes such as cardiac hypertrophy and heart failure. The transcription factors estrogen-related receptor-α (ERRα) and peroxisome proliferator-activated receptor (PPAR) regulate PDK4 expression through the potent transcriptional coactivator PPARγ coactivator-1α (PGC-1α). NF-κB activation in AC16 cardiac cells inhibit ERRα and PPARβ/δ transcriptional activity, resulting in reduced PGC-1α and PDK4 expression, and an enhanced glucose oxidation rate. However, addition of the NF-κB inhibitor parthenolide to these cells prevents the downregulation of PDK4 expression but not ERRα and PPARβ/δ DNA binding activity, thus suggesting that additional transcription factors are regulating PDK4. Interestingly, a recent study has demonstrated that the transcription factor E2F1, which is crucial for cell cycle control, may regulate PDK4 expression. Given that NF-κB may antagonize the transcriptional activity of E2F1 in cardiac myocytes, we sought to study whether inflammatory processes driven by NF-κB can downregulate PDK4 expression in human cardiac AC16 cells through E2F1 inhibition. Protein coimmunoprecipitation indicated that PDK4 downregulation entailed enhanced physical interaction between the p65 subunit of NF-κB and E2F1. Chromatin immunoprecipitation analyses demonstrated that p65 translocation into the nucleus prevented the recruitment of E2F1 to the PDK4 promoter and its subsequent E2F1-dependent gene transcription. Interestingly, the NF-κB inhibitor parthenolide prevented the inhibition of E2F1, while E2F1 overexpression reduced interleukin expression in stimulated cardiac cells. Based on these findings, we propose that NF-κB acts as a molecular switch that regulates E2F1-dependent PDK4 gene transcription