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Perfluorooctanoic acid (PFOA) is a widespread synthetic persistent organic pollutant that may enrich along the food chain and affect the growth, development, reproduction, and lipid metabolism of aquatic organisms, particularly the benthic organisms. However, the toxic effects of PFOA on the half-smooth tongue sole Cynoglossus semilaevis, a commercial benthic fish in China, have rarely been reported. Because juvenile fish are sensitive to environmental pollutants, in the present study, histological assessment and tran-scriptome sequencing were performed to determine the short-term impact of PFOA on juvenile half-smooth tongue soles. Histological analysis showed that PFOA exposure caused hepatocyte rupture, intestinal villi breakage, increased goblet cell count, and brain abnormal. Transcriptome results showed that some interesting signaling pathways, such as glycolysis/gluconeogenesis, PPAR signaling pathway and GABAergic synapse signaling pathway, were enriched after PFOA exposure. In addition, some metabolic, immune and neural genes were differentially expressed, which including ependymin, hbb1-like and gad 1, and they were up-regulated after 14 days of exposure. Transcriptome results also indicated that half-smooth tongue sole might improve energy metabolism in response to PFOA toxicity after 7 days of exposure. These findings provide a basis for studying the ecological effects of PFOA on marine benthic fishes. [ABSTRACT FROM AUTHOR]

Due to poor local accuracy and temporal resolution, the GIM (global ionospheric map) application continues to be of restricted use in obtaining the characteristics of seismic-ionospheric effects. Utilizing spherical harmonic (SH) function and generalized trigonometric series (GTS), the latest 15 min/map GIM with high precision released from the Chinese Academy of Sciences (CAS), is expected to record the short-term response of the fine ionospheric structure. From the interquartile range (IQR) method, we first present the application of CAS GIM in the Mw8.2 Chiapas earthquake in Mexico on September 7, 2017. To verify the reliability, the IGS GIM at low temporal resolution of 2 h/map was simultaneously analyzed and compared. Our results exhibit clear local anomalies that preceded the Chiapas event by 5 days. The detection of IGS GIM merely captured the basic features of pre-earthquake ionospheric anomalies, i.e., abnormal local effect with a duration of 15 h, maximum amplitude of 20 TECU, and westward migration in the seismogenic area with epicentral distance <4092 km. As a comparison, the periodic variations of motion state, energy, and abnormal morphology in the ionospheric anomalies were originally revealed by CAS GIM. The motion tracks exhibited oscillation periodicity characteristics, and the nonstationary and nonlinear intensity fluctuation implied a harmonic energy transmission. These results reflected the imbalance between energy transmission and ion + distribution in dynamic ionospheric processes. Then, the evolution of the ionospheric anomaly could be divided into three stages: formation of 9.2–12.4 LT, climax of 12.6–19.5 LT, and dissipation of 19.7–23.7 LT. During the peak period, the changes in energy transmission resulted in transforming the ionosphere to a "single-double peaks" shape and strong enhancement of the TEC intensity. The variations in horizontal phase velocity of 166–320 km/s in the abnormal region reflected the differences in electromagnetic waves from slow increases to rapid attenuation in the formation and dissipation periods. Based on the electromagnetic field disturbances recorded by the Swarm spacecraft, potential lithosphere–atmosphere–ionosphere Coupling (LAIC) effects could be identified through the electromagnetic coupling path. These features made it easy to remove earthquake precursor signals from other "source-type" TEC turbulences. [ABSTRACT FROM AUTHOR]

To explore the ionospheric coupling mechanism, the total electron contents (TECs) and slant TECs (STECs) were processed from GPS sites in China, Nepal and India, and the singular spectrum analysis (SSA) method was introduced to investigate the seismic-ionospheric signals prior to the Mw7.8 Nepal earthquake on April 25, 2015. The results of pre-earthquake ionospheric anomaly show that there were obviously positive on 2nd day and negative anomalies on 14th day prior to the earthquake, respectively. The radius of anomalous area with a regular elliptical shape reached 2500 km and 2000 km in the above days respectively, which was close to the radius of Nepal earthquake. After excluding the moving effects of ionosphere hump, the investigation by the global ionosphere maps (GIMs) shows that a wide TEC abnormality appeared over the epicenter and conjugated region with the duration of 12 hr. Besides, the magnitude of TEC anomalies impending the shock, with its peaks happening at the midday (local time), was proportional to the number of days prior to the occurrence. By using the STECs within seismogenic zone, we further studied the coseismic ionospheric disturbance (CID) of Nepal earthquake. The results show that two modes of CID propagation velocity have been detected. Due to the TEC respond of Rayleigh wave, one mode had average propagating speed of 1.3 km/s in the near-field within 800 km, and gradually reaching up to 2.7 km/s in the far-field beyond 2000 km. Another mode had average propagating speed of 0.6 km/s only existing in the near-field, which was in accordance with the speed of shock acoustic waves. Besides, CID intensity presented the obvious directional difference. The ambient magnetic field around the epicenter made it easier for CID to spread in the southward direction, the plateau topography also prohibited the propagation of ionospheric disturbance, and most CID points were detected along the southeast direction of the epicenter which is consistent with the rupture propagation. [ABSTRACT FROM AUTHOR]

In this study, the changes of the fatty acid composition of phospholipid in different tissues (muscle, heart, brain and spleen) of steelhead trout (Oncorhynchus mykiss) were analyzed when the water temperature decreased gradually from 16°C to 12°C, 8°C, 6°C, 4°C, 2°C and 1°C. Three fish individuals each tank (average weight 70.32 g ± 9.12 g) were collected and used to analysis at each designed temperatures. At normal temperature (16°C), the fatty acid composition of phospholipid of muscle and heart was similar each other. The highest concentration of saturate fatty acids (SFA) was found in the phospholipid of spleen. The brain phospholipid contained higher oleic acid (18:1n9) than the phospholipid of other tissues at 16°C. When the environmental temperature decreased, the concentration of unsaturated fatty acids of phospholipids in all tissues increased, and accordingly the ratio pf the unsaturated to saturated fatty acids (U/S) and unsaturation index (UI) increased, indicating that steelhead trout can compensate temperature- dependent changes in membrane fluidity by remodeling the fatty acid composition of phospholipids. The changes in the fatty acid composition of phospholipid were tissue-specific. At the early stages of the experiment (16°C to 8°C), the fatty acid composition of phospholipid changed remarkably in muscle, heart, and spleen. When temperature decreased to less than 8°C, an obvious response of phospholipid fatty acid was observed in all tissues. The change of phospholipid composition of steelhead trout tissues may be affected by both cold stress and starvation when the temperature decreased to 2°C, and the change of phospholipid composition of muscle was very obvious. [ABSTRACT FROM AUTHOR]

This study was conducted to evaluate the critical thermal maximum (CTMax), the routine metabolism rate (MO2) and the limiting oxygen saturation (LOS) of three salmonids with four different body weights ranging from 16 g to 131 g. The CTMax was estimated at three different heating rates including 0.5°C min−1, 1°C h−1 and 2°C d−1. Results showed that the CTMax of maple trout (Oncorhynchus mykiss) was the highest, which was followed by steelhead trout (O. mykiss) and Atlantic salmon (Salmon salar). The CTMax of the salmonid fish decreased with the increment of body weight, and was significantly influenced by the heating rate. The MO2 of the salmonid fish increased with the increment of temperature, and decreased with the increment of body weight. Suffocation points of the fish decreased with increasing body weight and temperature. Steelhead trout was more tolerant to hypoxia than maple trout and Atlantic salmon, while the MO2 of Atlantic salmon was the highest among these three salmonids. The LOS of the fish generally had a positive trend with temperature and body weight, and the LOS of steelhead trout was significantly lower than that of maple trout and Atlantic salmon. In conclusion, maple trout was the most tolerant kind to high temperature, while steelhead trout was the most tolerant to hypoxia among three kinds of salmonids. Moreover, the abilities to tolerate higher temperature of three salmonids were affected by their body weight and the heating rate, while the abilities to tolerate hypoxia were influenced by their body weight and the water temperature. [ABSTRACT FROM AUTHOR]

Picoeukaryotes are important members of the surface ocean microbial community with high diversity and significant temporal and spatial variations in community composition. Little is known about the picoeukaryotic biodiversity and community in the Yellow Sea, where hydrologic conditions are very different with the influence of the Yellow Sea Warm Current (YSWC). Using Illumina high throughput sequencing targeting 18S rDNA, we investigated the composition of picoeukaryotes at a permanent monitoring site in the central Yellow Sea from 2011 to 2013. Alveolata, Stramenopiles, and Archaeplastida were the main super groups found. Prasinophytes were dominant in N-YSWC (not influenced by the YSWC) samples whilst YSWC (influenced by the YSWC) samples were dominated by different groups, such as MALV-II (novel marine Alveolata), MAST-3, MAST-4 (novel marine Stramenopiles), and Dictyochophyceae. N-YSWC samples were grouped together in nMDS (non-metric multidimensional scaling) using the Bray-Curtis method. Distances between each two YSWC samples were greater. Based on indicator operational taxonomic unit (OTU) analysis (IOA), indicator species of the YSWC were represented by Pseudochattonella farcimen, Florenciella parvula within the class Dictyochophyceae, and Phaeocystis cordata within the class Prymnesiophyceae. The findings in our study suggest that picoeukaryotic communities in the central Yellow Sea differ temporally in response to changes in the YSWC. [ABSTRACT FROM AUTHOR]

Solar ultraviolet B (UVB) irradiance at the Earth's surface is increasing due to anthropogenic influences. To evaluate the effects of enhanced UVB radiation on photosynthetic characteristics of the marine diatom Phaeodactylum tricornutum, the species was exposed to four levels of UVB radiation, 0, 0.25, 0.75, and 1.50 KJ m day for 7 days. Effects of UVB stress on net photosynthetic rate, net respiration rate, variable chlorophyll (Chl) fluorescence parameters, Chl a and carotenoid contents, and UV-absorbing compounds (UVACs) were investigated. Results showed that there were no significant differences in terms of net respiration rate or maximal photochemical efficiency of photosystem II (F/F) between the treatments in the short or long term. However, enhanced UVB radiation at an intensity of 0.16 W m had a negative effect on the net photosynthetic rate, electron transport rate, and on the pathway of excess energy dissipation over the short term (1 to 5 days). Carotenoid and UVACs content increased under UVB radiation. Photosynthetic parameters were unaffected by UVB radiation on the seventh day indicating that P. tricornutum can adapt to UVB radiation in the long term. Results of the present study indicate that there is a dynamic balance between damage and adaptation in microalgae that enables them to adapt to UVB-induced photosystem alterations during both short-term and long-term exposure. [ABSTRACT FROM AUTHOR]

The mechanism for the hydroxyl-radical-induced depolymerization of cellulose under alkaline conditions in air was investigated using density functional theory at the B3LYP/6-31+G(d,p) level as well as electron transfer theory. The pathway for the depolymerization of cellulose was obtained theoretically and H abstraction from the C(3) atom of the pyran ring during the cleavage of the glucosidic bond was found to be the rate-limiting step due to its high energy barrier (16.81 kcal/mol) and low reaction rate constant (4.623 × 104 mol L−1 s−1). Calculations of the electron transfer between O2 and the saccharide radical performed with the HARLEM software package revealed that following the H abstraction, the oxygen molecule approaches C(2) on the saccharide radical and obtains an electron from the radical, even though no bond forms between the oxygen molecule and the radical. The rate constant for electron transfer could be as high as 1.572 × 1011 s−1. Furthermore, an enol intermediate is obtained during the final stage of the depolymerization. [ABSTRACT FROM AUTHOR]