This study assesses the response of phytoplankton assemblages to recent climate change, especially with regard to the shrinking of sea ice in the northern Chukchi Sea of the western Arctic Ocean. ...Distribution patterns of phytoplankton groups in the late summers of 2008-2010 were analysed based on HPLC pigment signatures and, the following four major algal groups were inferred via multiple regression and cluster analyses: prasinophytes, diatoms, haptophytes and dinoflagellates. A remarkable interannual difference in the distribution pattern of the groups was found in the northern basin area. Haptophytes dominated and dispersed widely in warm surface waters in 2008, whereas prasinophytes dominated in cold water in 2009 and 2010. A difference in the onset date of sea ice retreat was evident among years-the sea ice retreat in 2008 was 1-2 months earlier than in 2009 and 2010. The spatial distribution of early sea ice retreat matched the areas in which a shift in algal community composition was observed. Steel-Dwass's multiple comparison tests were used to assess the physical, chemical and biological parameters of the four clusters. We found a statistically significant difference in temperature between the haptophyte-dominated cluster and the other clusters, suggesting that the change in the phytoplankton communities was related to the earlier sea ice retreat in 2008 and the corollary increase in sea surface temperatures. Longer periods of open water during the summer, which are expected in the future, may affect food webs and biogeochemical cycles in the western Arctic due to shifts in phytoplankton community structure.
The size structure and biomass of a phytoplankton community during the spring bloom period can affect the energy use of higher-trophic-level organisms through the predator–prey body size ...relationships. The timing of the sea ice retreat (TSR) also plays a crucial role in the seasonally ice-covered marine ecosystem, because it is tightly coupled with the timing of the spring bloom. Thus, it is important to monitor the temporal and spatial distributions of a phytoplankton community size structure. Prior to this study, an ocean colour algorithm was developed to derive phytoplankton size index FL, which is defined as the ratio of chlorophyll a (chl a) derived from cells larger than 5 µm to the total chl a, using satellite remote sensing for the Chukchi and Bering shelves. Using this method, we analysed the pixel-by-pixel relationships between FL during the marginal ice zone (MIZ) bloom period and TSR over the period of 1998–2013. The influences of the TSR on the sea surface temperature (SST) and changes in ocean heat content (ΔOHC) during the MIZ bloom period were also investigated. A significant negative relationship between FL and the TSR was widely found in the shelf region during the MIZ bloom season. However, we found a significant positive (negative) relationship between the SST (ΔOHC) and TSR. Specifically, an earlier sea ice retreat was associated with the dominance of larger phytoplankton during a colder and weakly stratified MIZ bloom season, suggesting that the duration of the nitrate supply, which is important for the growth of large-sized phytoplankton in this region (i.e. diatoms), can change according to the TSR. In addition, under-ice phytoplankton blooms are likely to occur in years with late ice retreat, because sufficient light for phytoplankton growth can pass through the ice and penetrate into the water columns as a result of an increase in solar radiation toward the summer solstice. Moreover, we found that both the length of the ice-free season and the annual median of FL positively correlated with the annual net primary production (APP). Thus, both the phytoplankton community composition and growing season are important for the APP in the study area. Our findings showed a quantitative relationship between the interannual variability of FL, the TSR, and the APP, which suggested that satellite remote sensing of the phytoplankton community size structure is suitable to document the impact of a recent rapid sea ice loss on the ecosystem of the study region.
Recent ocean warming and subsequent sea ice decline resulting from climate change could affect the northward shift of the ecosystem structure in the Chukchi Sea and Bering Sea shelf region (Grebmeier ...et al., 2006b). The size structure of phytoplankton communities provides an index of trophic levels that is crucial to understanding the mechanisms underlying such ecosystem changes and their implications for the future. This study proposes a new ocean color algorithm for deriving this characteristic by using the region's optical properties. The size derivation model (SDM) estimates the phytoplankton size index FL on the basis of size-fractionated chlorophyll-a (chl-a) using the light absorption coefficient of phytoplankton, aph(λ), and the backscattering coefficient of suspended particles including algae, bbp(λ). FL was defined as the ratio of algal biomass attributed to cells larger than 5 μm to the total. It was expressed by a multiple regression model using the aph(λ) ratio, aph(488)/aph(555), which varies with phytoplankton pigment composition, and the spectral slope of bbp(λ), γ, which is an index of the mean suspended particle size. A validation study demonstrated that 69% of unknown data are correctly derived within FL range of ±20%. The spatial distributions of FL for the cold August of 2006 and the warm August of 2007 were compared to examine application of the SDM to satellite remote sensing. The results suggested that phytoplankton size was responsive to changes in sea surface temperature. Further analysis of satellite-derived FL values and other environmental factors can advance our understanding of ecosystem structure changes in the shelf region of the Chukchi and Bering Seas.
During the late summer of 1997, most of the continental shelf in the southeastern Bering Sea was covered by aquamarine-colored waters as a result of massive blooms of the coccolithophore,
Emiliania ...huxleyi (
E. huxleyi). Since then,
E. huxleyi blooms in the eastern Bering Sea have become common. This study was conducted to examine spatio-temporal variability in
E. huxleyi blooms in the eastern Bering Sea and to determine what factors are responsible for the blooms. In this study, we used datasets from the satellite ocean color sensor, SeaWiFS (Sea-viewing Wide Field-of-view Sensor) and MODIS (MODerate resolution Imaging Spectroradiometer) to detect the
E. huxleyi blooms. The
E. Huxley bloom was only found in the middle of the continental shelf domain (MSD), where the water depth is 20 to 100
m. We found large-scale interannual and seasonal variability in the area of the
E. huxleyi blooms, with massive blooms observed in the spring of 1998 and 2000, and in the fall of 1997 and 2000. The blooms now typically peak in September, and only small bloom areas have also been observed since 2001.
Here what we proposed is that the key parameter for the
E. huxleyi blooms is the strength of the density stratification resulted from two water masses formed in different season, surface warm layer and cold bottom water (CBW). Warming of the CBW since 2001 in the middle shelf have induced weakening the aforementioned stratification during summer. With less stratification, the water column is much more easily mixed, resulting in an increased nutrient (nitrate and silicate) supply from subsurface layers by storms in the summer. This is likely to be responsible for the recent decrease in
E. huxleyi blooms in the eastern Bering Sea shelf. Conversely, the strong stratification induced by an eruptive warming of surface layer and intensified cold bottom water may result in the development of the massive
E. huxleyi blooms like in 1997.
► We found large-scale interannual and seasonal variability in the area of the
E. huxleyi blooms, with massive blooms observed in the spring of 1998 and 2000, and in the fall of 1997 and 2000 in the eastern Bering Sea. ► The key parameter for the
E. huxleyi blooms is the strength of the density stratification resulted from two water masses formed in different season, surface warm layer and cold bottom water.
Benchmark numerical solutions for a three-dimensional natural convection heat transfer problem in a cubical cavity are presented in this paper. The 3-D cavity has two differentially heated and ...isothermal vertical walls and also four adiabatic walls. The computations are conducted for three Rayleigh numbers of 10
4, 10
5 and 10
6. The filled fluid is with air and the Prandtl number is fixed at 0.71. The computed results are efficiently obtained by using the time–space method, which was proposed by Saitoh (1991) as a highly efficient and fast solver for general heat transfer and fluid flow problems. In our computations, the high-accuracy finite differences of a fourth-order were employed for the spatial discretization of governing equations and boundary conditions. In addition the third-order backward finite difference was used in timewise discretization. The resultant converged flow and temperature characteristics are also presented. The spatial grid dependency of the solutions was examined on a uniform grid. In addition, the grid-independent benchmark solutions were obtained by Richardson extrapolation for three cases. The present benchmark solutions will be useful for checking the performance and accuracy of any numerical methodologies.
The conserved oligomeric Golgi (COG) complex is involved in intra‐Golgi retrograde trafficking, and mutations in six of its eight subunits have been reported in congenital disorders of glycosylation ...(CDG). Here we report a patient showing severe acquired microcephaly, psychomotor retardation, seizures, liver dysfunction, hypocupremia, and hypoceruloplasminemia. Analysis of his serum glycoproteins revealed defects in both sialylation and galactosylation of glycan termini. Trio‐based whole‐exome sequencing identified two heterozygous mutations in COG2: a de novo frameshift mutation c.701dup (p.Tyr234*) and a missense mutation c.1900T > G (p.Trp634Gly). Sequencing of cloned reverse‐transcription polymerase chain reaction (RT‐PCR) products revealed that both mutations were located on separate alleles, as expected, and that the mutant transcript harboring the frameshift mutation underwent degradation. The c.1900T > G (p.Trp634Gly) mutation is located in a domain highly conserved among vertebrates and was absent from both the public database and our control exomes. Protein expression of COG2, along with COG3 and COG4, was decreased in fibroblasts from the patient. Our data strongly suggest that these compound heterozygous mutations in COG2 are causative of CDG.
We have investigated the suitability of high melting point phase change materials for use in new, large scale solar thermal electricity plants. Candidate materials for latent heat thermal energy ...storage are identified and their operating parameters modeled and analysed. The mathematical characteristics of charging and discharging these storage materials are discussed. Several high melting point, high conductivity materials are shown to be suitable and advantageous for use with solar thermal electricity plants, such as Sydney University’s novel, low cost CLFR and MTSA collector systems, as well as existing parabolic trough and tower technologies.
We developed a next‐generation sequencing (NGS) based mutation screening strategy for neurodevelopmental diseases. Using this system, we screened 284 genes in 40 patients. Several novel mutations ...were discovered. Patient 1 had a novel mutation in ACTB. Her dysmorphic feature was mild for Baraitser‐Winter syndrome. Patient 2 had a truncating mutation of DYRK1A. She lacked microcephaly, which was previously assumed to be a constant feature of DYRK1A loss of function. Patient 3 had a novel mutation in GABRD gene. She showed Rett syndrome like features. Patient 4 was diagnosed with Noonan syndrome with PTPN11 mutation. He showed complete agenesis of corpus callosum. We have discussed these novel findings.
•Lower trophic ecosystem model for the global ocean.•4D-VAR reanalysis is used for the environmental fields.•Optimization of bio-ecological parameter values by a Green’s function approach.•Consistent ...biological and environmental fields throughout the global ocean.•Analysis of variability in the ecosystem associated with El Niños.
A lower trophic ecosystem model, which was originally developed for describing the variability in plankton distribution in the western North Pacific, is applied to the global ocean. A realistic time series of dynamically self-consistent circulation fields obtained by a 4-dimensional variational ocean data assimilation experiment is used for the environmental fields in the ecosystem model. An optimization of the bio-ecological parameter values in 40 provinces by a Green’s function approach enables the ecosystem model to represent the observed variabilities of nutrients and surface chlorophyll concentration with a relatively small number (11) of compartments. In addition, artificial trends of the ecosystem variables due to model errors are generally suppressed by the optimization. The obtained parameter values and ecosystem fields are generally consistent with observations in terms of assimilated and non-assimilated metrics. The integrated lower-trophic ecosystem and physical fields in the global ocean offer important information on the mechanisms (such as El Niños) responsible for the seasonal–interannual variability in the lower trophic ecosystem. Our results demonstrate that, with adequate parameter sets capable of modifying indirectly the model and significance of each pathway to reflect the characteristics of local species, a simple ecosystem model can be applied in quantitative analyses to enhance our understanding of the influence of climate variations on the ocean ecosystem.
Toll-like receptors (TLRs) are innate recognition molecules for microbial products, but their direct interactions with corresponding ligands remain unclarified. LPS, a membrane constituent of ...gram-negative bacteria, is the best-studied TLR ligand and is recognized by TLR4 and MD-2, a molecule associated with the extracellular domain of TLR4. Although TLR4-MD-2 recognizes LPS, little is known about the physical interaction between LPS and TLR4-MD-2. Here, we demonstrate cell surface LPS-TLR4-MD-2 complexes. CD14 greatly enhances the formation of LPS-TLR4-MD-2 complexes, but is not coprecipitated with LPS-TLR4-MD-2 complexes, suggesting a role for CD14 in LPS loading onto TLR4-MD-2 but not in the interaction itself between LPS and TLR4-MD-2. A tentative dissociation constant (Kd) for LPS-TLR4-MD-2 complexes was approximately 3 nM, which is approximately 10-20 times lower than the reported Kd for LPS-MD-2 or LPS-CD14. The presence of detergent disrupts LPS interaction with CD14 but not with TLR4-MD-2. E5531, a lipid A antagonist developed for therapeutic intervention of endotoxin shock, blocks LPS interaction with TLR4-MD-2 at a concentration 100 times lower than that required for blocking LPS interaction with CD14. These results reveal direct LPS interaction with cell surface TLR4-MD-2 that is distinct from that with MD-2 or CD14.
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