Rare earth element fingerprints in Korean coastal bay sediments: Association with provenance discrimination

Rare earth elements (REEs: La-Lu) in surface sediments collected from the mouth and middle tidal flats of Gomso Bay, South Korea, in August 2011 and May 2012 were analyzed to investigate the fine-grained sediment provenance. The upper continental crust (UCC)-normalized light REEs (LREEs: La to Nd) were more enriched than the middle REEs (MREEs: Sm to Dy) and heavy REEs (HREEs: Ho to Lu), resulting in large (La/Yb)_UCC (1.9 ± 0.4) to (Gd/Yb)_UCC (1.4 ± 0.2) ratios. The monthly (La/Yb)_UCC values differed between the mouth and middle tidal flats due to deposition of fine-grained sediments that originated from distant rivers (the Geum and Yeongsan) and the Jujin Stream, located on the southern shore of the inner bay. We observed relative reductions in the (La/Yb)_UCC value and REE content in the sediments from the mouth of the bay compared with those from Jujin Stream sediments. Confined to the middle tidal flat around the KH Line of Jujin Stream, the sediments, most enriched in LREEs but depleted in Eu, were distributed in August as strong Jujin Stream runs. Here, we suggest that an increase in LREE/HREE and decrease in MREE/LREE ratios can be used as a proxy to identify the Jujin Stream provenance in mixed riverine sediments and to trace Jujin Stream sediments within the Gomso Bay tidal flat, especially in the summer rainy season.     

Evaluation of Effective Depth of PVD Improvement in Soft Clay Deposit: A Field Case Study

This article presents a case history of determination of effective depth of prefabricated vertical drains (PVDs) under embankment loading on a very soft clay deposit in central China, near Jiujiang, Jiangxi Province. The height of the embankment was 5.3 m and construction time was about one year. The PVDs were installed to a depth of 8.5 m at a spacing of 1.5 m in a triangular pattern. Field observations and the finite element method (FEM) were employed to analyze the performance of the soft deposit during embankment construction. The influential depth of the embankment loading was evaluated based on settlement, excess pore pressure, and stress increase in subsoil, both from the observed data and FEM analysis. The effective PVD depth was determined in the following ways: (1) the depth of 5% subsoil settlement of surface settlement; (2) vertical stress increase in subsoil of 25% in-situ stress; and (3) consolidation time/PVD depth relation by FEM. Based on the analysis, the effective depth of PVDs was determined to be between 10 and 12.8 m for this field case.     

Seasonal variation and principle of cyanobacterial biomass and forms in the water source area of Chaohu City,China

We investigated seasonal variations in cyanobacterial biomass and the forms of its dominant population(M. aeruginosa) and their correlation with environmental factors in the water source area of Chaohu City,China from December 2011 to October 2012. The results show that species belonging to the phylum Cyanophyta occupied the maximum proportion of phytoplankton biomass,and that the dominant population in the water source area of Chaohu City was M. aeruginosa. The variation in cyanobacterial biomass from March to August 2012 was well fitted to the logistic growth model. The growth rate of cyanobacteria was the highest in June,and the biomass of cyanobacteria reached a maximum in August. From February to March 2012,the main form of M.aeruginosa was the single-cell form; M.aeruginosa colonies began to appear from April,and blooms appeared on the water surface in May. The maximum diameter of the colonies was recorded in July,and then gradually decreased from August. The diameter range of M. aeruginosa colonies was 18.37–237.77 μm,and most of the colonies were distributed in the range 20–200 μm,comprising 95.5% of the total number of samples. Temperature and photosynthetically active radiation may be the most important factors that influenced the annual variation in M. aeruginosa biomass and forms. The suitable temperature for cyanobacterial growth was in the range of 15–30°C. In natural water bodies,photosynthetically active radiation had a significant positive influence on the colonial diameter of M.aeruginosa(P0.01).     

Identification and bioinformatics analysis of microRNAs from the sporophyte and gametophyte of <Emphasis Type="Italic">Pyropia haitanensis</Emphasis>

Pyropia haitanensis (T. J. Chang et B. F. Zheng) N. Kikuchi et M. Miyata (Porphyra haitanensis) is an economically important genus that is cultured widely in China. P. haitanensis is cultured on a larger scale than Pyropia yezoensis, making up an important part of the total production of cultivated Pyropia in China. However, the majority of molecular mechanisms underlying the physiological processes of P. haitanensis remain unknown. P. haitanensis could utilize inorganic carbon and the sporophytes of P. haitanensis might possess a PCK-type C₄-like carbon-fixation pathway. To identify microRNAs and their probable roles in sporophyte and gametophyte development, we constructed and sequenced small RNA libraries from sporophytes and gametophytes of P. haitanensis. Five microRNAs were identified that shared no sequence homology with known microRNAs. Our results indicated that P. haitanensis might posses a complex sRNA processing system in which the novel microRNAs act as important regulators of the development of different generations of P. haitanensis.     

Strategy of photo-protection in phytoplankton assemblages in the Kongsfjorden,Svalbard, Arctic

Photo-protective functions were investigated in phytoplankton assemblages at Kongsfjorden, Svalbard in spring, using their UV-absorbing compounds (mycosporine-like amino acids (MAAs)), xanthophyll pigments (diadinoxanthin (DD) and diatoxanthin (DT)) and < beta >- dimethylsulphoniopropionate (< beta >_-DMSP). The dominant phytoplankton species in the inner bay were dominated by Phaeocystis spp. and nanoflagellates, while the offshore waters were dominated by Thalassiosira spp. In the inner bay, UVabsorbing compounds and xanthophyll pigments exhibited higher ratios of MAA to chlorophyll a (MAA:chl a ratio), and both DD and DT to chlorophyll a (DD:chl a ratio and DT:chl a ratio), respectively. Thus, the photoprotective-pigments such as DD and DT appear to complement MAAs in the natural phytoplankton assemblage. However, the ratio of < beta >_-DMSP to chlorophyll a (< beta >_-DMSP:chl a ratio) did not show a distinct spatial distribution according to environmental factors or interspecies differences. In this study, we found that photoprotective compounds occurred in a manner dependent on the phytoplankton species composition in Kongsfjorden Bay, where Phaeocystis is the dominant species.     

Protective effects of C-phycocyanin on alcohol-induced acute liver injury in mice

Excessive alcohol consumption leads to liver disease. Extensive evidence suggests that C-phycocyanin (C-PC), a chromophore phycocyanobilin derived from Spirulina platensis, exerts protective effects against chemical-induced organ damage. In this study, we investigated whether C-PC could protect against ethanol-induced acute liver injury. Serum alanine aminotransferase (ALT), aspartate aminotransferase (AST), triglyceride (TG), total cholesterol (CHOL), low-density lipoprotein (LDL), liver homogenate malondialdehyde (MDA), superoxide dismutase (SOD) content were measured, and pathological examination of liver sections were examined. C-PC showed obvious inhibitory effects on serum ALT, AST, TG, CHOL, LDL and MDA, and SOD content significantly increased in the liver. The structure of hepatic lobules was clear, liver sinus returned to normal, and liver cell cords were arranged in neat rows. Cloudiness, swelling, inflammatory cell infiltration and spotty necrosis of liver cells were significantly reduced. Therefore, C-PC can significantly protect against ethanol-induced acute liver injury.     

Importance of kelp-derived organic carbon to the scallop <Emphasis Type="Italic">Chlamys farreri</Emphasis> in an integrated multi-trophic aquaculture system

Bivalves and seaweeds are important cleaners that are widely used in integrated multi-trophic aquaculture (IMTA) systems. A beneficial relationship between seaweed and bivalve in the seaweed-based IMTA system has been confirmed, but the trophic importance of seaweed-derived particulate organic materials to the co-cultured bivalve is still unclear. We evaluated the trophic importance of the kelp Saccharina japonica to the co-cultured scallop Chlamys farreri in a typical IMTA farm in Sungo Bay (Weihai, North China). The dynamics of detritus carbon in the water were monitored during the culturing period. The proportion of kelp-derived organic matter in the diet of the co-cultured scallop was assessed via the stable carbon isotope method. Results showed that the detritus carbon in the water ranged from 75.52 to 265.19 μg/L, which was 25.6% to 73.8% of total particulate organic carbon (TPOC) during the study period. The amount of detritus carbon and its proportion in the TPOC changed throughout the culture cycle of the kelp. Stable carbon isotope analysis showed that the cultured scallop obtained 14.1% to 42.8% of its tissue carbon from the kelp, and that the percentages were closely correlated with the proportion of detritus carbon in the water (F =0.993, P= 0.003). Evaluation showed that for 17 000 tons (wet weight) of annual scallop production, the kelp contributed about 139.3 tons of carbon (535.8 tons of dry mass). This confirms that cultured kelp plays a similar trophic role in IMTA systems as it does in a natural kelp bed. It is a major contributor to the detritus pool and supplies a vital food source to filter-feeding scallops in the IMTA system, especially during winter and early spring when phytoplankton are scarce.     

Antioxidant system responses in two co-occurring green-tide algae under stress conditions

Green tides have occurred every year from 2007 to 2014 in the Yellow Sea. Ulva prolifera(Müller) J. Agardh has been identified as the bloom-forming alga,co-occurring with U. intestinalis. We observed distinct strategies for both algal species during green tides. U. prolifera exhibited a high abundance initially and then decreased dramatically,while U. intestinalis persisted throughout. The antioxidant system responses of these two macroalgae were compared in the late phase of a green tide(in-situ) and after laboratory acclimation. Lipid peroxidation and antioxidant system responses differed significantly between the two. Malondialdehyde and hydrogen peroxide contents increased significantly in-situ in U. prolifera,but not in U. intestinalis. In U. prolifera,we observed a significant decrease in total antioxidant ability(T-AOC),antioxidant enzymes(SOD and Apx),and non-enzyme antioxidants(GSH and As A) in-situ. U. intestinalis showed the same pattern of T-AOC and SOD,but its Gpx,Apx,and GSH responses did not differ significantly. The results suggest that U. prolifera was more susceptible than U. intestinalis to the harsh environmental changes during the late phase of a Yellow Sea green tide. The boom and bust strategy exhibited by U. prolifera and the persistence of U. intestinalis can be explained by differences in enzyme activity and antioxidant systems.     

From sequential to parallel growth of cities: Theory and evidence from Canada

This paper examines city growth patterns and the corresponding city size distribution evolution over long periods of time using a simple New Economic Geography(NEG) model and urban population data from Canada. The main findings are twofold. First, there is a transition from sequential to parallel growth of cities over long periods of time: city growth shows a sequential mode in the stage of rapid urbanization, i.e., the cities with the best development conditions will take the lead in growth, after which the cities with higher ranks will become the fastest-growing cities; in the late stage of urbanization, city growth converges according to Gibrat′s law, and exhibits a parallel growth pattern. Second, city size distribution is found to have persistent structural characteristics: the city system is self-organized into multiple discrete size groups; city growth shows club convergence characteristics, and the cities with similar development conditions eventually converge to a similar size. The results will not only enhance our understanding of urbanization process, but will also provide a timely and clear policy reference for promoting the healthy urbanization of developing countries.     

A bi-modal model for Chinese cities: City size,car use and land rent

China is experiencing rapid urbanization and motorization. Urban transport congestion poses a challenge to the cities of China. Policies have been made trying to control the car use and the land use in Chinese cities without sound modelling researches. The existing literature on monocentric city modelling has shown that the parameters are critical for the outcome of the modelling. Following the Alonso-type monocentric model, this paper introduces a bi-modal model to simulate the city size, the distribution of land rent and the modal substitution in Chinese cities. We set the key parameters according to the recent available data of China′s cities, and re-explain the hypothesis of the model. Then we make a sensitivity analysis to reveal the impacts of key parameters on the Chinese cities. According to the results, we find that the wage, the price of car use and the agriculture rent have significant impacts on city size. The land supply for the private transport or the public transport has the strongest impacts on car use and the level of transport congestion. The total population of the city and the wage level have strong impacts on land rent. Some results are counter-intuitive, but explainable. We also discuss implication of these results for policy making.