Numerical simulation on the process of saltwater intrusion and its impact on the suspended sediment concentration in the Changjiang (Yangtze) estuary

To study the relationship between sediment transportation and saltwater intrusion in the Changjiang (Yangtze) estuary, a three-dimensional numerical model for temperature, salinity, velocity field, and suspended sediment concentration was established based on the ECOMSED model. Using this model, sediment transportation in the flood season of 2005 was simulated for the Changjiang estuary. A comparison between simulated results and observation data for the tidal level, flow velocity and direction, salinity and suspended sediment concentration indicated that they were consistent in overall. Based on model verification, the simulation of saltwater intrusion and its effect on sediment in the Changjiang estuary was analyzed in detail. The saltwater intrusion in the estuary including the formation, evolution, and disappearance of saltwater wedge and the induced vertical circulation were reproduced, and the crucial impact of the wedge on cohesive and non-cohesive suspended sediment distribution and transportation were successfully simulated. The result shows that near the salinity front, the simulated concentrations of both cohesive and non-cohesive suspended sediment at the surface layer had a strong relationship with the simulated velocity, especially when considering a 1-hour lag. However, in the bottom layer, there was no obvious correlation between them, because the saltwater wedge and its inducing vertical circulation may have resuspended loose sediment on the bed, thus forming a high-concentration area near the bottom even if the velocity near the bottom was very low during the transition phase from flood to ebb.

Effective AC and DC responses of nonlinear composites at higher concentration

For higher concentration of inclusions, an effective medium approximation (EMA) method is used to investigate the bulk effective response of weakly nonlinear composites, which are subject to the constitutive relation of electric displacement and electric field, D-alpha = epsilon E-alpha + chi(alpha)|E|(2) E. As an example of three dimensions, under the external AC and DC electric fields E-app = E-a (1 + sin omega t), we have derived the general effective nonlinear response of composites by the EMA method for higher concentration of spherical inclusions. Furthermore, the effective nonlinear responses at harmonics are predicted.

三种红藻光合作用色素系统的比较研究

本研究分为三个部分：1.以坛紫菜（Porphyra haitanesis Chang et Zheng）的叶状体和丝状体为研究对象，比较坛紫菜叶状体和丝状体的光合色素、色素蛋白的组成，并提取纯化藻红蛋白、藻蓝蛋白、藻胆体及类囊体膜和光系统。研究结果表明坛紫菜叶状体和丝状体色素及色素蛋白的含量不同，藻红蛋白是主要的色素蛋白，坛紫菜叶状体和丝状体的藻红蛋白的含量分别为2.9mg藻红蛋白/g鲜重、4.2mg藻红蛋白/g鲜重，这表明坛紫菜叶状体和丝状体藻红蛋白含量丰富，是提取藻红蛋白很好的材料。藻胆体的性质差异不大，但类囊体膜差异显著，从坛紫菜叶状体中分离到了两种不同的类囊体膜带，光系统Ⅰ(PSⅠ)和PSⅡ分别结合在两条类囊体膜带上，但从坛紫菜丝状体中也分离到两条类囊体膜带，它们的光谱性质和蛋白组成相似，仅放氧速率和DCIP活性有差异，从坛紫菜丝状体中我们仅分离到PSⅡ。坛紫菜叶状体PSⅡ有5种外在蛋白(33、20、Cytc 550、15、12kDa蛋白)，而坛紫菜丝状体外在蛋白仅有4条，缺少12kDa蛋白。2. 以在中国江苏部分地区进行了大规模的商业化栽培的突变体条斑紫菜（Porphyra yezoensis Ueda）和野生型条斑紫菜为研究对象，比较其色素及色素蛋白组成、对不能光质的利用率及藻胆体的组成。条斑紫菜和突变型条斑紫菜对不同的光质利用效果有差异，在白光的照射下，野生型紫菜的放氧速率最大，而突变型紫菜在黄光照射下的放氧速率最大。条斑紫菜野生型与突变型色素含量上有明显的差异,突变型紫菜的藻红蛋白含量明显减少而藻蓝蛋白的含量增加。通过杂交的方法证实诱变所获得条斑紫菜突变体为细胞质突变，但是突变型紫菜却发生了由细胞核编码的γ亚基的缺失，这表明突变型紫菜藻红蛋白含量和性质发生了明显的变化。3. 为了找出淡水红藻-深紫美芒藻(Compsopogon coeruleus (Balbis) Montagne)分布狭窄及生物产量低的原因，本文对深紫美芒藻在不同的盐离子浓度下的放氧速率及藻胆体色素组成和结构上进行研究。结果显示：微量的NaCl（0.1mM）促进深紫美芒藻放氧，而深紫美芒藻在较高的NaCl（1、10mM）, NaH2PO4 （0.1、1、10mM）和 NH4NO3（0.1、1、10mM）溶液中却没有检测到氧气的产生。这与深紫美芒藻生长的环境一致即深紫美芒藻生活在低盐浓度、低营养的泉水中。深紫美芒藻的藻胆体是由藻红蛋白、藻蓝蛋白及别藻蓝蛋白组成，上面结合α、β和γ亚基，含有藻红胆素、藻篮胆素，但缺乏缺少藻尿胆素。

Variation characteristics and ecological risk of heavy metals in the south Yellow Sea surface sediments

Eight cruises were conducted on the south Yellow Sea (SYS) from 1998 to 2005. Variations and the potential ecological risk of heavy metals were studied using the survey data collected during October 2003. The metal content (except for As) was high in the central area where the fine grain size sediments were dominant, and low inshore area where more coarse sediments were present. This suggested that grain size was important in determining distributions of heavy metals. In some local areas, other influencing factors, such as organic content, sedimentation rate, burial efficiency and metal's existing form were discussed. The annual averages of metals showed a stable trend with appreciable fluctuations in 8 years. Using potential ecological risk index (E (RI)) to evaluate the integrated pollution effect of heavy metals, 38.7% of the investigated area was in a moderate degree of contamination, while 77.8% was under moderate ecological risk. However, no distinct correlation was found between E (RI) and plankton biomass. In conclusion, the sediment quality of SYS was good, and the ecological risk was low in general.

Evolution of nutrient structure and phytoplankton composition in the Jiaozhou Bay ecosystem

The inventories of nutrients in the surface water and large phytoplankton( > 69 pm) were analyzed from the data set of JERS ecological database about a typical coastal waters, the Jiaozhou Bay, China, from 1960s for N, P and from 1980s; for Si. By examining long-term changes of nutrient concentration, calculating stoichiometric balance, and comparing diatom composition, Si limitation of diatom production was found to be more possible. The possibility of Si limitation was from 37% in 1980s to 50% in 1990s. Jiaozhou Bay ecosystem is becoming serious eutrophication, with notable increase of NO2-N, NO3-N and NH4-N from 0.1417 mumol/L, 0.5414 mumol/L, 1.7222 mumol/L in 1960s to 0.9551 mumol/L, 3.001 mumol/L, 8.0359 mumol/L in late 1990s respectively and prominent decrease of Si from 4.2614 mumol/L in 1980s to 1.5861 mumol/L in late 1990s; the nutrient structure is controlled by nitrogen; the main limiting nutrient is probably silicon; because of the Si limitation the phytoplankton community structure has changed drastically.

Ocean urea fertilization for carbon credits poses high ecological risks

The proposed plan for enrichment of the Sulu Sea, Philippines, a region of rich marine biodiversity, with thousands of tonnes of urea in order to stimulate algal blooms and sequester carbon is flawed for multiple reasons. Urea is preferentially used as a nitrogen source by some cyanobacteria and dinoflagellates, many of which are neutrally or positively buoyant. Biological pumps to the deep sea are classically leaky, and the inefficient burial of new biomass makes the estimation of a net loss of carbon from the atmosphere questionable at best. The potential for growth of toxic dinoflagellates is also high, as many grow well on urea and some even increase their toxicity when grown on urea. Many toxic dinoflagellates form cysts which can settle to the sediment and germinate in subsequent years, forming new blooms even without further fertilization. If large-scale blooms do occur, it is likely that they will contribute to hypoxia in the bottom waters upon decomposition. Lastly, urea production requires fossil fuel usage, further limiting the potential for net carbon sequestration. The environmental and economic impacts are potentially great and need to be rigorously assessed. (C) 2008 Elsevier Ltd. All rights reserved.

Ecological environment changes in Daya Bay, China, from 1982 to 2004

Data collected from 12 marine monitoring stations in Daya Bay from 1982 to 2004 reveal a substantial change in the ecological environment of this region. The average N/P ratio increased from 1.377 in 1985 to 49.09 in 2004. Algal species changed from 159 species of 46 genera in 1982 to 126 species of 44 genera in 2004. Major zooplankton species went from 46 species in 1983 to 36 species in 2004. The annual mean biomass of benthic animals was recorded at 123.10 gm(2) in 1982 and 126.68 g m(2) in 2004. Mean biomass and species of benthic animals near nuclear power plants ranged froth 317.9 g m(2) in 1991 to 45.24 g m(2) in 2004 and from 250 species in 1991 to 177 species in 2004. A total of 12-19 species of hermatypic corals and 13 species of mangrove plants were observed in Daya Bay from 1984 to 2002. 2008 Elsevier Ltd. All rights reserved.

Nutrient structure of seawater and ecological responses in Jiaozhou Bay, China

Nutrient concentrations in seawater, and C, N, P, Si and chlorophyll a content in different-sized particulates were measured in Jiaozhou Bay, and C, N, P, Si composition in different-sized fractions of phytoplankton and their ecological responses to nutrient structure of the seawater were studied. Microphytoplankton and nanophytoplankton were dominant in Jiaozhou Bay. High C (16.50-20.97 unol L-1), N (2.46-2.99 mu mol L-1) and low P (0.06-0.12 mu mol L-1), Si (0.18-0.57 mu mol L-1) content, and high N/P (24.7-64.6) and low SUP (4.4-10.8), Si/N (0.06-0.20) ratios were found in all sized groups of particulates. These values reflected the elemental compositions of different-sized fractions of phytoplankton as being an ecological response to the nutrients in the seawater. The ratios deviated significantly from the Redfield values. The nutrient composition of seawater and particulates and their relationship to chlorophyll a showed that phytoplankton growth was possibly limited by Si. Si limitation appears favorable for controlling the ecological equilibrium of Jiaozhou Bay. Different-sized fractions of phytoplankton had different suitability to nutrient structures of the seawater. Among phytoplankton size groups, nanophytoplankton and microphytoplankton growths were more adaptable in eutrophic Jiaozhou Bay, and more competitive for assimilation of Si. This is consistent with their diatom-dominated composition, controlling the biomass and productivity of phytoplankton in Jiaozhou Bay. (c) 2006 Elsevier Ltd. All rights reserved.

Density-dependent effects on seston dynamics and rates of filtering and biodeposition of the suspension-cultured scallop Chlamys farreri in a eutrophic bay (northern China): An experimental study in semi-in situ flow-through systems

Effects of stocking density on seston dynamics and filtering and biodeposition by the suspension-cultured Zhikong scallop Chlamys farreri Jones et Preston in a eutrophic bay (Sishili Bay, northern China), were determined in a 3-month semi-field experiment with continuous flow-through seawater from the bay. Results showed that the presence of the scallops could strongly decrease seston and chlorophyll a concentrations in the water column. Moreover, in a limited water column, increasing scallop density could cause seston depletion due to scallop's filtering and biodeposition process, and impair scallop growth. Both filtration rate and biodeposition rate of C. farreri showed significant negative correlation with their density and positive relationship with seston concentration. Calculation predicts that the daily removal of suspended matter from water column by the scallops in Sishili Bay ecosystem can be as high as 45% of the total suspended matter; and the daily production of biodeposits by the scallops in early summer in farming zone may amount to 7.78 g m(-2), with daily C, N and P biodeposition rates of 3.06 x 10(-1), 3.86 x 10(-2) and 9.80 x 10(-3) g m(-2), respectively. The filtering and biodeposition by suspension-cultured scallops could substantially enhance the deposition of total suspended particulate material, suppress accumulation of particulate organic matter in water column, and increase the flux of C, N and P to benthos, strongly enhancing pelagic-benthic coupling. It was suggested that the filtering-biodeposition process by intensively suspension-cultured bivalve filter-feeders could exert strong top-down control on phytoplankton biomass and other suspended particulate material in coastal ecosystems. This study also indicated that commercially suspension-cultured bivalves may simultaneously and potentially aid in mitigating eutrophication pressures on coastal ecosystems subject to anthropogenic N and P loadings, serving as a eutrophic-environment bioremediator. The ecological services (e.g. filtering capacity, top-down control, and benthic-pelagic coupling) functioned by extractive bivalve aquaculture should be emphasized in coastal ecosystems. (c) 2005 Elsevier B.V. All rights reserved.

Effects of nitrogen source and concentration on growth rate and fatty acid composition of Ellipsoidion sp (Eustigmatophyta)

In order to study the effects of different nitrogen source and concentration on the growth rate and fatty acid composition, a marine microalga Ellipsoidion sp. with a high content of eicosapentaenoic acid (EPA) was cultured in media with different nitrogen sources and concentrations. During the pre-logarithmic phase, the alga grew faster with ammonium as N source than with nitrate, but the reverse applied during the post-logarithmic phase. The alga grew poorly in N-free medium or medium with urea as the sole N source. In the same growth phase, ammonium medium resulted in higher yield of total lipid, but the EPA yield did not differ significantly different from that using nitrate medium. The maximum growth rate occurred in medium containing 1.28 mmol L-1 sodium nitrate, while maximum EPA and total lipid contents were reached at 1.92 mmol L-1, when EPA accounted for 27.9% total fatty acids. The growth rate kept stable when NH4Cl ranged from 0.64 to 2.56 mmol L-1, and the maximum content of total lipid and EPA occurred in the medium with 2.56 mmol L-1 NH4Cl. The EPA content was higher in the pre- than post-logarithmic phase, though the total lipid content was lower. The highest EPA content expressed as percent total fatty acid was 27.9% in nitrate medium and and 39.0% in ammonium medium.

GEO-ECOLOGICAL TRANSECT STUDIES IN NORTHEAST TIBET (QINGHAI, CHINA) REVEAL HUMAN-MADE MID-HOLOCENE ENVIRONMENTAL CHANGES IN THE UPPER YELLOW RIVER CATCHMENT CHANGING FOREST TO GRASSLAND

Geo-ecological transect studies in the pastures of the upper catchment of the HuangHe (99 degrees 30'-100 degrees 00'E/35 degrees 30'-35 degrees 40'N'; 3,000-4,000 in a.s.l., Qinghai province, China) revealed evidence that pastures replace forests. Plot-based vegetation records and fenced grazing exclosure experiments enabled the identification of grazing indicator plants for the first time. The mapping of vegetation patterns of pastures with isolated juniper and Spruce forests raise questions as to the origin of the grasslands, which arc widely classified as "natural" at present. Soil investigations and charcoal fragments of Juniperus (8,153 +/- 63 uncal BP) and Picea (6,665 +/- 59 uncal BP) provide evidence of the wider presence of forests. As temperatures and rainfall records undoubtedly represent a forest climate, it is assumed that the present pastures have replaced forests. Circumstantial evidence arising from investigations into the environmental history of the Holocene effectively substantiates this theory.

Pollen morphology and its in systematic and ecological significance in Rheum (Polygonaceae) from China

Pollen morphology of 40 species of Rheum, belonging to eight sections, was investigated under LM and SEM. Four new exine patterns were found in the species: a) microcchinate-foveolate, b) rugulate, c) verrucate-perforate, and d) verrucaterugulate ornamentation. In addition, two patterns, the Rheum-type pollens with microechinate-perforate and fine-reticulate, as previously described, were also confirmed in the present study. Based on above study the evolution trends of pollen morphology in the taxa involved were discussed phylogenetically as below. As microechinate-perforate exine pattern existed commonly, the pattern is, therefore, regarded as the most primitive among all the six types. The fine-reticulate type was thought as a derivative type, deriving from the basic micro echinate-foveolate-perforate pattern, and followed by the rugulate and verrucate-perforate ornamentation. The verrucate-rugulate ornamentation should be the most advanced. More than one pollen type often exist in most of the sections in Rheum. The pollen morphology of Rheum was strongly correlated with its geographical and ecological distribution. Three medicinally important species R. officinale, R. palmation and R. tanguticum can be palynologically distinguished by their ornamentations.

Ecological basis of Alpine meadow ecosystem management in Tibet: Haibei Alpine Meadow Ecosystem Research Station

Alpine meadow and shrub are the main pasture types on the Tibetan Plateau, and they cover about 35% of the total land area. In order to understand the structural and functional aspects of the alpine ecosystem and to promote a sustainable animal production system, the Haibei Alpine Meadow Research Station was established in 1976. A series of intensive studies on ecosystem structure and function, including the energy flow and nutrient cycling of the ecosystem, were the main tasks during the first 10 years. Meanwhile, studies with 5 different grazing intensities on both summer and winter pasture have been conducted. In the early years of the 1990s, the research station started to focus its research work on global warming, biodiversity and sustainable animal production systems in pastoral areas. Various methods for improving degraded pasturelands have been developed in the region.

Social and ecological influences on dispersal and philopatry in the plateau pika (Ochotona curzoniae)

Benefits and costs of dispersal and philopatry of the social plateau pika (Ochotona curzoniae) were studied on the Tibetan plateau for 3 years. Although short-lived, plateau pikas live in cohesive family groups that occupy burrow systems in sedge meadow habitat Most (57.8%) plateau pikas were philopatric, and dispersal movements were extremely restricted. No juvenile females or adult pikas moved more than two family ranges between years; the greatest observed dispersal distances were by two juvenile males that moved five family ranges from the family of their birth. Traversing unfamiliar habitat was not a cost of pika dispersal because most dispersers settled in families that they could easily visit before dispersal. Dispersal movements appeared to result in equalization of density among pika families, an expected result if competition for environmental resources influenced dispersal. Males did not disperse to gain advantages in competition for mates, as evidenced by their moving to families with significantly fewer females. Females, however, moved to families with significantly more males. Males provide abundant paternal care, and significantly more offspring per female survived to become adults from families with more adult males per adult female. Evidence concerning the influence of inbreeding avoidance on natal dispersal was indirect. Some males exhibited natal philopatry; thus some families had opportunity for close inbreeding. Males and females that dispersed had no opposite-sex relatives in their new families. Philopatric pikas may have benefited by remaining in families that exhibited low local densities, and philopatric females might have benefited from social cooperation with relatives.

华南震旦纪-寒武纪两期成磷事件及其地球动力学意义

Phosphorus is an important biological and ecological element that to a certain degree constrains ecological environment and nutrient (including carbon) cycling. Marine sedimentary phosphorites are the principal phosphorus supply of the mankind. In the eastern to southern margins of the Yangtze Craton, South China, there are two phosphogenetic events at the Doushantuo stage of the Late Sinian and the Meishucun stage of the Early Cambrian respectively, corresponding two explosion events of life across the Precambrian\Cambrian boundary. Phosphorus ores from the Sinian and Cambrian phosphate in South China can be classified roughly into two categories, namely, grained and non-grained phosphorites. Grained phosphorites, hosted in dolostone type of phosphogenetic sequences and with larger industrial values, occur mainly in margins of the Upper Yangtze Platform, formed in shallow-water environments with high hydraulic energy and influenced by frequent sea-level change. Non-grained phosphorites, hosted principally in black-shale type of phosphogenetic sequences and with smaller industrial values, are distributed mainly in the Jiangnan region where deeper-water sub-basins with low hydraulic energy were prevailing at the time of phosphogenesis. Secular change ofδ~(13)C, δ~(18) O, ~(86)Sr/~(87)Sr values of carbonates from Sinian and Cambrian sequences were determined. A negative abnormal ofδ~(13)C, δ~(18)O values and positive abnormal of 86Sr/87Sr values from the fossiliferous section of the Lowest Cambrian Meishucun Formation implies life depopulation and following explosion of life across the PrecambriamCambrian boundary. Based on a lot of observations, this paper put forward a six-stage genetic model describing the whole formational process of industrial phosphorites: 1) Phosphorus was transported from continental weathering products and stored in the ocean; 2) dissolved phosphates in the seawater were enriched in specific deep seawater layer; 3) coastal upwelling currents took this phosphorus-rich seawater to a specific coastal area where phosphorus was captured by oceanic microbes; 4) clastic sediments in this upwelling area were enriched in phosphorus because of abundant phosphorus-rich organic matters and because of phosphorus absorption on grain surfaces; 5) during early diagenesis, the phosphorus enriched in the clastic sediments was released into interstitial water by decomposition and desorption, and then transported to the oxidation-reduction interface where authigenic phosphates were deposited and enriched; 6) such authigenic phosphate-rich layers were scoured, broken up, and winnowed in shallow-water environments resulting in phosphate enrichment. The Sinian-Cambrian phosphorites in South China are in many aspects comparable with coastal-upwelling phosphorites of younger geological ages, especially with phosphorites from modern coastal upwelling areas. That implies the similarities between the Sinian-Cambrian ocean and the modern ocean. Although Sinian-Cambrian oceanic life was much simpler than modern one, but similar oceanic planktons prevail, because oceanic planktons (particularly phytoplanktons) are crucial for phosphate enrichment related to coastal upwelling. It implies also a similar seawater-layering pattern between the Sinian-Cambrian ocean and the modern ocean. The two global phosphate-forming events and corresponding life-explosion events at the Sinian and Cambrian time probably resulted from dissolved-phosphate accumulation in seawater over a critical concentration during the Earth's evolution. Such an oceanic system with seawater phosphorus supersaturation is evidently unstable, and trends to return to normal state through phosphate deposition. Accordingly, this paper put forward a new conception of "normal state <=> phosphorus-supersaturation state" cycling of oceanic system. Such "normal state <=> phosphorus-supersaturation state" cycling was not only important for the three well-known global phosphate-forming events, also related to the critical moments of life evolution on the Earth. It might be of special significance. The favorable paleo-oceanic orientation in regard to coastal-upwelling phosphorite formation suggests a different orientation of the Yangtze Craton between the Sinian time and the present time (with a 135° clockwise difference), and a 25° anti-clockwise rotation of the Yangtze Craton from late Sinian to early Cambrian. During the Sinian-Cambrian time, the Yangtze Craton might be separated from the Cathaysia Block, but might be still associated with the North China Craton.