Interannual variations in the nutrient cycle in the central Bohai Sea in response to anthropogenic inputs.

In recent decades, there has been growing concern regarding the effects of human activities on the coastal nutrient cycle. However, interannual variations in the coastal nutrient cycle in response to anthropogenic nutrient input have rarely been quantified. In this study, a hydrodynamic-ecological model capable of describing the nitrogen and phosphorus cycles was used to analyze interannual variations in the nutrient cycle in the central Bohai Sea, a typical semi-enclosed sea in the Northwest Pacific. The results showed an increasing trend of dissolved inorganic nitrogen and particulate nitrogen from 1998 to 2017, whereas different forms of phosphorus showed no obvious interannual variations. The annual nutrient budgets were also quantitatively estimated from 1998 to 2017. This indicates that atmospheric nitrogen deposition plays an important role in interannual variations in the nitrogen cycle. A large amount of nitrogen from anthropogenic inputs was mainly removed by sedimentation processes instead of increasing the standing stock of nitrogen in the sea. With the reduction of anthropogenic inputs, the model showed that a variety of forms of nitrogen concentration decreased linearly, whereas phosphorus concentration increased slightly. Therefore, although environmental governance can effectively alleviate water eutrophication, it is necessary to avoid the situation where the dissolved inorganic nitrogen concentration in the sea becomes too low for phytoplankton to grow, which may determine the primary productivity and eventually affect fishery resources.

Anthropogenic impacts on nutrient variability in the lower Yellow River.

Excessive nutrient discharges and changes in nutrient ratios caused by global change and anthropogenic activities have been reported in global rivers; however, the actual alterations occurring in the Yellow River environment is too fast to catch up with. From 2001 to 2018, dissolved inorganic nitrogen (DIN), dissolved inorganic phosphorus (DIP) and dissolved silicon (DSi) concentrations showed decreasing trends in the lower Yellow River throughout the study period. Dissolved organic phosphorus (DOP) concentrations increased since 2009, reaching up to 95% of the total dissolved phosphorus. Annual minimum dissolved organic nitrogen concentrations increased with time. We observed extremely low nutrient concentration events since 2014 in response to the retention effect of large reservoirs; this significantly reduced the downstream water discharge and sediment load and increased phytoplankton uptake. To further analyze the variability of nutrient fluxes, we quantified the fluxes to the Yellow River from natural (runoff, precipitation deposition, and sediment load from the Loess Plateau), anthropogenic (recharged water, fertilizer application, and vegetation coverage), social and industrial (population urbanization, GDP, and sewage effluents) sources. The highest contributions of total nutrient fluxes emptied into the Yellow River was fertilizer losing (44-48%) for DIN, sewage effluents (85-88%) for DIP, and runoff (35-65%) for DSi, respectively. Strictly controlling the amount of fertilizer and improving the application methods, improving sewage treatment technology, and vigorously promoting "green travel" might reduce nutrients emptied into the Yellow River based on the main sources of nutrients. Our study may help policy makers formulate strategies and it is possible to own a better water quality in the Yellow River.

Effect of hyperbaric oxygen on the process of hypertrophic scar formation in rabbit ears.

OBJECTIVE: To explore the influence of hyperbaric oxygen on scar formation in rabbit ears. METHODS: A total of 20 New Zealand rabbits were selected to establish the hypertrophic scar model on the ears. The rabbits were randomly divided into control group and experimental group (7d, 14d, 21d, and 28d group according to different HBO treatment days),each experimental group received hyperbaric oxygen treatment after the operation at the same time everyday for 1 hour. After the day 29, the scars were collected. Histomorphological change in scars was observed by hematoxylin-eosin staining, Masson staining, and transmission electrical microscope. The expression of bax, bcl-2, and the cell apoptosis rate was detected by immunohistochemical method. RESULTS: (i) Both number of fibroblast and amount of collagen fibrils in experimental group were significantly reduced compared with those in control group. In Masson staining, arrangement of collagen fibrils in experimental group was much more irregular and coarse than control groups. (ii) HI value can be found much smaller in the experimental groups than the control (P < .05). Among the four experimental groups, there is significant difference among 7d, 14d, and 21d groups (P < .05), while there is no difference between 21d and 28d groups (P > .05). (iii) Expression of Bax could be detected up-regulated in experimental group (P < .05). While the expression of Bcl-2 is detected significantly down-regulated in experimental group than that in control group (P < .05). Compared with the 7d group, the expression of Bax and Bcl-2 has significant difference in 14d group (P < .05), and the expression of this two factors in 21d group has significant difference comparing with 14d group(P < .05),but there is no significant difference between 28d group and 21d group(P > .05). (iv) Significant difference of cell apoptosis rate can be detected between the experimental groups and the control group (P < .05). Among the four experimental groups, there is significant difference among 7d, 14d, and 21d groups (P < .05), while there is no difference between 21d and 28d groups (P > .05). CONCLUSION: The hyperbaric oxygen can up-regulate bax/bcl-2 value, increase the cell apoptosis rate, and inhibit the early hypertrophic scar in rabbit ears.

Hypoxia off the Changjiang (Yangtze River) estuary and in the adjacent East China Sea: Quantitative approaches to estimating the tidal impact and nutrient regeneration.

Large areas of hypoxia have been reported off The Changjiang Estuary and in the East China Sea. Five cruises, covering winter, spring, and summer, were carried out from 2007 to 2013 in this region, and in August 2013 (summer), an extensive hypoxic event (11,150km2) was observed, which was characterized by an estimated bulk oxygen depletion of 5.1 million tons. A strong tidal impact was observed associated with the bottom oxygen depletion, with the periodicity of diel variations in dissolved oxygen being 12h (i.e., similar to the tidal cycle). A conservative estimate of nutrient regeneration suggested that during the hypoxic event of August 2013, the amount of regenerated nitrogen (as nitrate) and phosphorus (as dissolved inorganic phosphorus) was 27,000-30,000 tons and 1300-41,000tons, respectively. Estimates of the absolute (bulk) regenerated nutrient fluxes were much greater than the conservative estimates.

Characterization of phosphorus sorption on the sediments of Yangtze River Estuary and its adjacent areas.

This paper studied the kinetics, isotherm and thermodynamics of phosphorus sorption onto the sediments of the Yangtze River estuary and its adjacent waters, as well as the sediments' compositions and physicochemical properties. The process could be described well by a two-compartment first order equation. The sorbed phosphorus mainly consisted of Ex-P and Fe-P, with Ex-P being the dominant. The equilibrium isotherms could be fitted well with a modified Langmuir equation. The calculations of the thermodynamic parameters indicated that the process was spontaneous and exothermic. The CEC and the fractions of clay, calcite and organic matter were correlated with the sorption parameters, while the surface proton charge of the sediments was significantly negatively correlated with them. Considering the kinetics and phosphorus forms changes during the process, the sorption in our study could be considered that the physical process plays an important role.

[Surface Property and Sorption Characteristics of Phosphorus onto Surface Sediments in Sanggou Bay].

Kinetic curves and isotherms were investigated to study the sorption mechanism of phosphorus onto the sediments of Sanggou Bay, together with the surface charge properties of sediments and the forms of phosphorus studied. The results showed that the sorption including a fast process and a slow one, and could be described by a two-compartment first order equation. The thermodynamic isotherms were well fitted with a modified Langmuir equation. The maximum adsorption capacity was larger in summer than in spring, and the smaller particle size was favorable to the sorption. The maximum adsorption capacities (Qm) were 0.0471-0.1230 mg x g(-1), and the zero equilibrium phosphorus concentration (EPC0) of the sediments ranged from 0.0596 mg x L(-1) to 0.1927 mg x L(-1), which indicated that the sediments from Sanggou Bay were sources of phosphorus. Inorganic phosphorus (IP) was the main form of total phosphorus (TP). The contents of exchangeable or loosely absorbed P and Fe-bound P increased significantly in the samples after sorption. The sorption process involved physical sorption and chemical sorption, with the former being the predominant.

Biogeochemistry of bulk organic matter and biogenic elements in surface sediments of the Yangtze River Estuary and adjacent sea.

This study investigated the distribution and roles of total organic carbon (TOC), biogenic silicon (BSi), various forms of nitrogen (N) and phosphorus (P), and the stable carbon isotope (δ(13)C) in surface sediments of the Yangtze River Estuary (YRE) and adjacent sea. Terrestrial input accounted for 12-63% of total organic matter in the study area. The distribution of biogenic elements was affected by the Changjiang Diluted Water, the Jiangsu Coastal Current, human activities, marine biological processes, and the sediment grain size. Potentially bioavailable N and P accounted for an average 79.6% of the total N (TN) and 31.8% of the total P (TP), respectively. The burial fluxes for TOC, BSi, TN and TP were 39.74-2194.32, 17.34-517.48, 5.02-188.85 and 3.10-62.72 µmol cm(-2) yr(-1), respectively. The molar ratios of total N/P (1.2-5.0), Si/P (5.0-14.8) and Fe/P (21-61) indicated that much of the P was sequestered in sediments.

[Study on distribution of phosphorus in surface sediments of the Yellow Sea and the East China Sea].

Different phosphorus compositions (TP, IP and OP) were determined in surface sediments of the Yellow Sea (YS) and the East China Sea (ECS),sampled from two cruises between March and June, 2011. The results showed that, contents of TP were from 10.50 micromol x g(-1) to 24.10 micromol x g(-1), IP ranged from 7.14 micromol x g(-1) to 17.10 micromol x g(-1) was the major phosphorus speciation accounting for more than 70% in TP. The percent of IP in TP at most stations was between 50% and 90% , only four stations which lied in the East China Sea with the percent was over 90%. The dominant factors affecting the phosphorus concentration and distribution in surface sediments were anthropogenic activities, sources of input materials, grain size, depositional environments and hydrological conditions. TP burial flux (TPBF) that appeared regional differences was affected by sedimentation rates, porosity and oxygen in bottom water, but TP content and sedimentation rates were crucial factors for TPBF.

[Influence of Ruditapes philippinarum aquaculture on benthic fluxes of biogenic elements in Jiaozhou Bay].

Nutrient excretion rates and the impact of Ruditapes philippinarum on benthic nutrient fluxes were measured by incubation experiments, and these results were used to assess the effect of R. philippinarum aquaculture on nutrient recycling in Jiaozhou bay. Our research indicates that the bioturbation of R. philippinarum would modify biogeochemical progresses in sediment, and restrain nutrients excreted by R. philippinarum releasing to overlying water. Only 37% DIN and 34% PO4(3-) -P excreted by R. philippinarum were released to seawater across the sediment-water interface due to bioturbation of R. philippinarum. According to the reduction of nutrient exchange across the sediment-water interface by bioturbation, only 19% (N) and 17% (P) of biogenic elements fed by R. philippinarum can be recycled and returned to seawater, while the others would be removed from seawater in Jiaozhou Bay. The ratios of Si: N and Si: P of nutrients released from sediment to seawater with bioturbation of R. philippinarum were about 5:18 and 5:1, which were far less than Redfield ratios. Therefore, aquaculture of R. philippinarum should promote BSi biodeposition to sediment and reduce the nutrient ratios of Si: N and Si: P in seawater of Jiaozhou bay.

Platelet-activating factor in the enteric nervous system of the guinea pig small intestine.

Platelet-activating factor (PAF) is a proinflammatory mediator that may influence neuronal activity in the enteric nervous system (ENS). Electrophysiology, immunofluorescence, Western blot analysis, and RT-PCR were used to study the action of PAF and the expression of PAF receptor (PAFR) in the ENS. PAFR immunoreactivity (IR) was expressed by 6.9% of the neurons in the myenteric plexus and 14.5% of the neurons in the submucosal plexus in all segments of the guinea pig intestinal tract as determined by double staining with anti-human neuronal protein antibody. PAFR IR was found in 6.1% of the neurons with IR for calbindin, 35.8% of the neurons with IR for neuropeptide Y (NPY), 30.6% of the neurons with IR for choline acetyltransferase (ChAT), and 1.96% of the neurons with IR for vasoactive intestinal peptide (VIP) in the submucosal plexus. PAFR IR was also found in 1.5% of the neurons with IR for calbindin, 51.1% of the neurons with IR for NPY, and 32.9% of the neurons with IR for ChAT in the myenteric plexus. In the submucosal plexus, exposure to PAF (200-600 nM) evoked depolarizing responses (8.2 +/- 3.8 mV) in 12.4% of the neurons with S-type electrophysiological behavior and uniaxonal morphology and in 12.5% of the neurons with AH-type electrophysiological behavior and Dogiel II morphology, whereas in the myenteric preparations, depolarizing responses were elicited by a similar concentration of PAF in 9.5% of the neurons with S-type electrophysiological behavior and uniaxonal morphology and in 12.0% of the neurons with AH-type electrophysiological behavior and Dogiel II morphology. The results suggest that subgroups of secreto- and musculomotor neurons in the submucosal and myenteric plexuses express PAFR. Coexpression of PAFR IR with ChAT IR in the myenteric plexus and ChAT IR and VIP IR in the submucosal plexus suggests that PAF, after release in the inflamed bowel, might act to elevate the excitability of submucosal secretomotor and myenteric musculomotor neurons. Enhanced excitability of motor neurons might lead to a state of neurogenic secretory diarrhea.