Carbon dioxide dynamics from sediment, sediment-water interface and overlying water in the aquaculture shrimp ponds in subtropical estuaries, southeast China

Aquaculture ponds can emit a large amount carbon dioxide (CO2), with the consequence of exacerbating global climate change. Many studies about CO2 dynamics across the water-air interface, but CO2 in sediment and overlying water received relative less attention. In this study, CO2 concentration in sediment porewater, the diffusive CO2 fluxes across the sediment-water interface (SWI), and the CO2 production rates in the overlying water (CO2_WP) were determined in the shrimp ponds in the Min River Estuary (MRE) and Jiulong River Estuary (JRE), southeast China, to analyze the dynamics of CO2 among different growth stages of shrimps. Our results showed large variations in porewater CO2 concentrations, CO2 diffusive fluxes and CO2_WP rates among different growth stages, with markedly larger values in the middle stage of shrimp growth. The temporal variation of CO2 in both estuarine ponds followed closely the seasonal change of temperature. The internal CO2 production (CO2_IP) in these ponds was dominated by sediments. A significantly larger mean porewater CO2 concentrations, diffusive fluxes and production rate were observed in the MRE ponds than those in the JRE ponds, which could be attributed to the lower water salinity and a larger source of carbon substrates in the former estuary. Considering a total surface area of 6.63 × 103 km2 across the mariculture ponds in subtropical estuaries, it is estimated conservatively that approximately 100 Gigagram (Gg) of dissolved organic carbon and 190 Gg of dissolved inorganic carbon were transported annually from the mariculture ponds into China's coastal areas. Because of the substantial supply of dissolved carbon, the adjacent coastal waters receiving effluent discharge from the mariculture ponds could become “hotspots” of CO2 emissions. Our results highlight the role of aquaculture pond as a major CO2 source in China's coastal areas, and effective actions are needed to alleviate the greenhouse gas (GHG) emissions from these ponds

Production and uptake of dissolved carbon, nitrogen, and phosphorus in overlying water of aquaculture shrimp ponds in subtropical estuaries, China

Water quality deterioration can adversely affect the long-term sustainability of aquaculture industry. Understanding the processes of nutrient regeneration and uptake is important for improving water quality and the overall ecosystem health of aquaculture system. In spite of the importance of dissolved nutrients (DOC, DIC, N-NO , N-NH , and P-PO ) in governing water quality and ecosystem functioning, the spatiotemporal variations in the production and uptake of dissolved nutrients in aquaculture ponds is still poorly understood. In this study, the nutrient production and uptake rates in the overlying water were quantified among different shrimp growth stages in the aquaculture ponds in the Min River Estuary (MRE) and Jiulong River Estuary (JRE), southeast China. Significant differences in the nutrient production and uptake rates in the overlying water were observed among the three growth stages and two estuaries. The temporal variations of DOC and DIC production rates in both estuarine ponds closely followed the seasonal cycle of temperature, while the difference in DOC and DIC production rates between the two estuaries was likely caused by differences in water salinity. The changes in the production and uptake rates of dissolved inorganic nitrogen (N-NO and N-NH ) and P-PO in the water column over time were partly related to the interactions between thermal conditions and phytoplankton biomass (e.g., chlorophyll a concentrations) in the ponds. Our results demonstrate the complex dynamics and environmental risk of dissolved nutrients in subtropical shrimp ponds, and call for a more effective management of nutrient-laden wastewater in safeguarding the long-term sustainability of aquaculture production

Large fine‐scale spatiotemporal variations of CH4 diffusive fluxes from shrimp aquaculture ponds affected by organic matter supply and aeration in Southeast China

Mariculture shrimp ponds are important CH4 sources to the atmosphere. However, the spatiotemporal variations of CH4 concentration and flux at fine spatial scales in mariculture ponds are poorly known, particularly in China, worlds largest aquaculture producer. In this study, the plot‐scale spatiotemporal variations of water CH4 concentration and flux, both within and among ponds, were researched in shrimp ponds in Shanyutan wetland, Min River Estuary, Southeast China. The average water CH4 concentration and diffusion flux across the water‐air interface in the shrimp ponds over the shrimp aquaculture period varied from 2.29 ± 0.29 to 50.48 ± 20.91 μM and from 0.09 ± 0.01 to 2.32 ± 0.95 mmol·m−2·hr−1, respectively. The CH4 emissions from the estuarine ponds varied greatly between seasons, with peaks in August and September, which was similar to the trend of water temperature and dissolved oxygen concentrations. There was no remarkable difference in CH4 concentration and flux between shrimp ponds but significantly spatiotemporal differences in CH4 concentration and flux within the ponds. Significantly higher emissions occurred in the feeding zone, accounting for approximately 60% of total CH4 emission flux, while much lower CH4 emissions appeared in aeration zone, contributing 14% to total flux. This study suggests the importance of considering spatiotemporal variation in the whole‐pond estimates of CH4 concentration and flux. In light of such high spatial variation within ponds, improving aeration and feed utilization efficiency would help to mitigate CH4 emissions from mariculture ponds

Preparation of Dual Functionalized Surfaces for Covalent Immobilization of BMP-6 and Adhesive Ligands for Biological Applications

The median age of our population causes osteoporosis, bone fractures and disorders, which are also caused by multiple myeloma. In the past 25 years, regenerative medicine had gained in importance, especially for regeneration and renewal of bone tissue, which consists of different cell types composed in a very complex architecture. The growth factor bone morphogenetic protein 6 (BMP-6) belongs to the transforming growth factor β (TGF- β) superfamily and it induces the differentiation of mesenchymal stem cells into mature osteoblasts in bone leading to new bone formation. Besides induction of osteogenic differentiation, BMP-6 is also known to induce cell death in multiple myeloma cells in high concentrations. However, a systemic application is not practicable, since uncontrolled diffusion causes a wide range of side-effects. Immobilization of growth factors allows local treatment of bone fractures and defects, while it prevents uncontrolled release of growth factors. Furthermore, the required amount of growth factors can be reduced tremendously. The objective of this work was the covalent immobilization of BMP-6 co-presented with clicked integrin ligands on a structured gold nanoparticle (AuNP) platform, using blockcopolymer micellar nanolithography (BCMN) developed by Prof. Spatz and co-workers, to study integrin signaling in connection with growth factor responses. BMP-6 was selectively bound to gold nanoparticles organized in a hexagonal structure on the surface allowing to control the amount and density on the surface. I showed that surface co-presentation of BMP-6 and RGD or α5β1 integrin selective ligand promotes SMAD1/5 phosphorylation and osteogenic differentiation of the standard model system C2C12, even at amounts as low as 1 ng, whereas soluble BMP-6 application is significantly less effective. Additionally, BMP-6 was immobilized on gold nanostructured polyethylene glycol diacrylamide (PEG-DA) hydrogels containing different concentrations of cRGD in order to study the influence of the stiffness on the cell signaling. Furthermore, this approach was used to investigate the effect of immobilized BMP-6 in low doses on the multiple myeloma cell line OPM-2 to induce cell death. This approach provides for the first time the successful presentation of BMP-6 in small and defined amounts on surfaces in combination with adhesive ligands. Furthermore, covalent immobilization hinders protein release while maintaining the biological activity of the growth factor

Spatial variations of N2O fluxes across the water‐air interface of mariculture ponds in a subtropical estuary in southeast China

While aquaculture ponds are potentially important sources of atmospheric N2O, the magnitude and variability of N2O concentrations and fluxes both within and across the ponds remain poorly understood. In this study, we examined the small‐scale spatial variations of dissolved N2O concentrations in water and N2O fluxes across the water‐air interface from three mariculture ponds in a subtropical estuary in southeast China. Our results showed that the dissolved concentrations and diffusive fluxes of N2O in the shrimp ponds ranged between 2.3–19.2 nM and 16.4–589.7 nmol m−2 hr−1, respectively, over the culture period. Significant variations of N2O concentrations and fluxes were observed within the ponds, with higher values being observed in the aeration area that could be attributed to the high rates of nitrification in the water column, as well as sediment N2O production and diffusive flux into the overlying water. Also, N2O concentrations and fluxes varied significantly among the three ponds as a result of the difference in N‐NO3− and N‐NH4+ concentrations in the water column. The large fine‐scale spatial variations of N2O concentrations and fluxes observed in our aquaculture ponds suggested that management practices such as aeration and bait feeding could largely affect the extent that aquaculture activities have on N2O emissions and climate change through their influence on the physicochemical environment (e.g., oxygen and N‐NH4+ concentrations) of the ponds

Photoproduction off Nuclei and Point-like Photon Interactions Part I: Cross Sections and Nuclear Shadowing

High energy photoproduction off nuclear targets is studied within the Glauber-Gribov approximation. The photon is assumed to interact as a $q\bar{q}$-system according to the Generalized Vector Dominance Model and as a ``bare photon'' in direct scattering processes with target nucleons. We calculate total cross sections for interactions of photons with nuclei taking into account coherence length effects and point-like interactions of the photon. Results are compared to data on photon-nucleus cross sections, nuclear shadowing, and quasi- elastic $\rho$-production. Extrapolations of cross sections and of the shadowing behaviour to high energies are given.Comment: 15 pages, 12 figure

Large spatial variations in diffusive CH4 fluxes from a subtropical coastal reservoir affected by sewage discharge in southeast China

Coastal reservoirs are potentially CH4 emission hotspots owing to their biogeochemical role as the sinks of anthropogenic carbon and nutrients. Yet, the fine-scale spatial variations in CH4 concentrations and fluxes in coastal reservoirs remain poorly understood, hampering an accurate determination of reservoir CH4 budgets. In this study, we examined the spatial variability of diffusive CH4 fluxes and their drivers at a subtropical coastal reservoir in southeast China using high spatial resolution measurements of dissolved CH4 concentrations and physicochemical properties of the surface water. Overall, this reservoir acted as a consistent source of atmospheric CH4, with a mean diffusive flux of 16.1 μmol m–2 h–1. The diffusive CH4 flux at the reservoir demonstrated considerable spatial variations, with the coefficients of variation ranging between 199 and 426% over the three seasons. The shallow water zone (comprising 23% of the reservoir area) had a disproportionately high contribution (56%) to the whole-reservoir diffusive CH4 emissions. Moreover, the mean CH4 flux in the sewage-affected sectors was significantly higher than that in the nonsewage-affected sectors. The results of bootstrap analysis further showed that increasing the sample size from 10 to 100 significantly reduced the relative standard deviation of mean diffusive CH4 flux from 73.7 to 3.4%. Our findings highlighted the role of sewage in governing the spatial variations in reservoir CH4 emissions and the importance of high spatial resolution data to improve the reliability of flux estimates for assessing the contribution of reservoirs to the regional and global CH4 budgets

Energy and Color Flow in Dijet Rapidity Gaps

When rapidity gaps in high-$p_T$ dijet events are identified by energy flow in the central region, they may be calculated from factorized cross sections in perturbative QCD, up to corrections that behave as inverse powers of the central region energy. Although power-suppressed corrections may be important, a perturbative calculation of dijet rapidity gaps in ${\rm p}\bar{\rm p}$ scattering successfully reproduces the overall features observed at the Tevatron. In this formulation, the average color content of the hard scattering is well-defined. We find that hard dijet rapidity gaps in quark-antiquark scattering are not due to singlet exchange alone.Comment: 9 pages, LaTeX, 2 epsi figure

Dynamical parton distributions of the nucleon and very small-x physics

Utilizing recent DIS measurements (F_{2,L}) and data on dilepton and high-E_{T} jet production we determine the dynamical parton distributions of the nucleon generated radiatively from valence-like positive input distributions at optimally chosen low resolution scales. These are compared with `standard' distributions generated from positive input distributions at some fixed and higher resolution scale. It is shown that up to the next to leading order NLO(\bar{MS}, DIS) of perturbative QCD considered in this paper, the uncertainties of the dynamical distributions are, as expected, smaller than those of their standard counterparts. This holds true in particular in the presently unexplored extremely small-x region relevant for evaluating ultrahigh energy cross sections in astrophysical applications. It is noted that our new dynamical distributions are compatible, within the presently determined uncertainties, with previously determined dynamical parton distributions.Comment: 21 pages, 2 tables, 16 figures, v2: added Ref.[60], replaced Fig.

D* Production in Deep Inelastic Scattering at HERA

This paper presents measurements of D^{*\pm} production in deep inelastic scattering from collisions between 27.5 GeV positrons and 820 GeV protons. The data have been taken with the ZEUS detector at HERA. The decay channel $D^{*+}\to (D^0 \to K^- \pi^+) \pi^+$ (+ c.c.) has been used in the study. The $e^+p$ cross section for inclusive D^{*\pm} production with $5<Q^2<100 GeV^2$ and $y<0.7$ is 5.3 \pms 1.0 \pms 0.8 nb in the kinematic region {$1.3<p_T(D^{*\pm})<9.0$ GeV and $| \eta(D^{*\pm}) |<1.5$}. Differential cross sections as functions of p_T(D^{*\pm}), $\eta(D^{*\pm}), W$ and $Q^2$ are compared with next-to-leading order QCD calculations based on the photon-gluon fusion production mechanism. After an extrapolation of the cross section to the full kinematic region in p_T(D^{*\pm}) and $\eta$(D^{*\pm}), the charm contribution $F_2^{c\bar{c}}(x,Q^2)$ to the proton structure function is determined for Bjorken $x$ between 2 $\cdot$ 10$^{-4}$ and 5 $\cdot$ 10$^{-3}$.Comment: 17 pages including 4 figure