Patchiness of phytoplankton and primary production in Liaodong Bay, China

<div><p>A comprehensive study of water quality, phytoplankton biomass, and photosynthetic rates in Liaodong Bay, China, during June and July of 2013 revealed two large patches of high biomass and production with dimensions on the order of 10 km. Nutrient concentrations were above growth-rate-saturating concentrations throughout the bay, with the possible exception of phosphate at some stations. The presence of the patches therefore appeared to reflect the distribution of water temperature and variation of light penetration restricted by water turbidity. There was no patch of high phytoplankton biomass or production in a third, linear patch of water with characteristics suitable for rapid phytoplankton growth; the absence of a bloom in that patch likely reflected the fact that the width of the patch was less than the critical size required to overcome losses of phytoplankton to turbulent diffusion. The bottom waters of virtually all of the eastern half of the bay were below the depth of the mixed layer, and the lowest bottom water oxygen concentrations, 3–5 mg L^–1, were found in that part of the bay. The water column in much of the remainder of the bay was within the mixed layer, and oxygen concentrations in both surface and bottom waters exceeded 5 mg L^–1.</p></div

Study area, sampling stations (● and △) and ¹⁴C incubation stations (△) in Liaodong Bay, China.

<p>Study area, sampling stations (● and △) and ¹⁴C incubation stations (△) in Liaodong Bay, China.</p

Contour maps of photosynthetic rates (Panel A, in mg C m^–3 h^–1), concentrations of Chl <i>a</i> (Panel B, in mg m^–3) and assimilation numbers (Panel C, in mg C mg^–1 Chl <i>a</i> h^–1), dissolved inorganic nitrogen (DIN, Panel D, in μM), silicate (SiO₃-Si, Panel E, in μM), and phosphate (PO₄-P, Panel F, in μM).

<p>Triangles in F denote stations with phosphate concentrations less than 25 nM.</p

Contour maps and/or corresponding location maps of temperature (Panels A and B, in °C), Secchi-disk depth (Panels C and D, in meters), Secchi-disk depth associated with temperature (Panel E), and dissolved oxygen (DO, Panel F, in mg L^–1).

<p>Contour maps and/or corresponding location maps of temperature (Panels A and B, in °C), Secchi-disk depth (Panels C and D, in meters), Secchi-disk depth associated with temperature (Panel E), and dissolved oxygen (DO, Panel F, in mg L^–1).</p

Relationship between DO concentrations and salinity (Panel A) and location of stations in three groups with different DO concentrations (Panel B).

<p>In Panels A and B, circle dots denote stations with high DO of more than 13 mg L^–1 at a salinity of 1 to low DO concentrations of 3–5 mg L^–1 at salinities of 16–26; Triangles and plus signs denote stations with DO concentrations of roughly 7–9 mg L^–1 and 9–11 mg L^–1, respectively, in both cases at salinities of 20–28.</p

Rational Design of GO-Modified Fe₃O₄/SiO₂ Nanoparticles with Combined Rhenium-188 and Gambogic Acid for Magnetic Target Therapy

Peanutlike magnetic-fluorescent Fe₃O₄/SiO₂ nanoparticles, with an effective dynamic diameter of 180 nm, were synthesized via EuO⁺ doping and coupling of two Fe₃O₄ cores and reassembling through the solvothermal process. Spherical pure Fe₃O₄/SiO₂ nanoparticles with an effective dynamic diameter of 230 nm were also prepared for comparison. We designed graphene oxide (GO)-modified core–shell Fe₃O₄/SiO₂ nanoparticles as a nanocarrier for loading gambogic acid (GA) following labeling with radioisotope rhenium-188. We also performed GA loading and releasing on GA-loaded magnetic nanoparticles, in vivo biodistribution, and magnetic drug targeting therapy experiments. Results indicated that the GA-loaded magnetic nanoparticles demonstrate a clear pH-dependent drug release behavior, having a higher release rate in acidic environments. The in vivo biodistribution of the magnetic nanoparticles has morphologic dependency, and the peanutlike nanoparticles (PN-Fe₃O₄) tend to accumulate more in the spleen, lung, and liver than in the spherical nanoparticles (S-Fe₃O₄). The targeted therapy showed a higher efficacy of PN-Fe₃O₄ in inhibiting tumor cell growth than the nontargeted therapy. The polyethyleneimine (PEI) grafting of PN-Fe₃O₄ with amide bond was also designed to find an effective active targeting antitumor agent considering the fact that the PEI–GO conjugate has a higher GA load efficiency and the convergence effect

Inter-Annual Variability of Area-Scaled Gaseous Carbon Emissions from Wetland Soils in the Liaohe Delta, China

<div><p>Global management of wetlands to suppress greenhouse gas (GHG) emissions, facilitate carbon (C) sequestration, and reduce atmospheric CO₂ concentrations while simultaneously promoting agricultural gains is paramount. However, studies that relate variability in CO₂ and CH₄ emissions at large spatial scales are limited. We investigated three-year emissions of soil CO₂ and CH₄ from the primary wetland types of the Liaohe Delta, China, by focusing on a total wetland area of 3287 km². One percent is <i>Suaeda salsa</i>, 24% is <i>Phragmites australis</i>, and 75% is rice. While <i>S</i>. <i>salsa</i> wetlands are under somewhat natural tidal influence, <i>P</i>. <i>australis</i> and rice are managed hydrologically for paper and food, respectively. Total C emissions from CO₂ and CH₄ from these wetland soils were 2.9 Tg C/year, ranging from 2.5 to 3.3 Tg C/year depending on the year assessed. Primary emissions were from CO₂ (~98%). Photosynthetic uptake of CO₂ would mitigate most of the soil CO₂ emissions, but CH₄ emissions would persist. Overall, CH₄ fluxes were high when soil temperatures were >18°C and pore water salinity <18 PSU. CH₄ emissions from rice habitat alone in the Liaohe Delta represent 0.2% of CH₄ carbon emissions globally from rice. With such a large area and interannual sensitivity in soil GHG fluxes, management practices in the Delta and similar wetlands around the world have the potential not only to influence local C budgeting, but also to influence global biogeochemical cycling.</p></div

Hydrographs for wetland study sites in the Liaohe Delta.

<p>a) Water level patterns for 2012, b) water level patterns for 2013, and c) water level patterns for 2014 from our five wetland sites, including two <i>Phragmites australis</i> sites (Phrag1, Phrag2), two <i>Suaeda salsa</i> sites (Suaeda1, Suaeda2), and one rice paddy site (Rice) in the Liaohe Delta, China. Missing data from Suaeda1 and Suaeda2 at the beginning of 2013, and for Suaeda2 beginning in August of 2014, represent datalogger failure. Consistent water levels <-30 cm for Phrag1 and Rice indicate times when water levels were below pressure transducers embedded in the soils.</p

Location of study sites and aerial distribution of habitat types sampled in the Liaohe Delta, China.

<p>Map highlights 31.6 km² of <i>Suaeda salsa</i> wetlands, 786 km² of <i>Phragmites australis</i> wetlands, and 2464.6 km² of rice paddy wetlands, as well as the location of our five wetland sites, including two in <i>Phragmites australis</i> (Phrag1, Phrag2), two in <i>Suaeda salsa</i> (Suaeda1, Suaeda2), and one in rice paddy (Rice). Aerial distribution data are from [<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0160612#pone.0160612.ref030" target="_blank">30</a>], and the shape file represents 2011 classifications (China Geological Survey).</p

Mean CO₂ fluxes, CH₄ fluxes, and a suite of physico-chemical characteristics of soils (± SE) from five wetland sites in the Liaohe Delta, China collected over three years.

<p>Mean CO₂ fluxes, CH₄ fluxes, and a suite of physico-chemical characteristics of soils (± SE) from five wetland sites in the Liaohe Delta, China collected over three years.</p