Long-term changes of phytoplankton community in Xiagu waters of Xiamen,China

Long-term changes of phytoplankton community by water sampling method in Xiagu Sea waters of Xiamen,China,were investigated in this study.Species composition of the phytoplankton community in these waters changed greatly since the 1950s.The numbers of Dinophyta species increased significantly,although Bacillariophyta species are generally dominant.The succession of dominant species in phytoplankton community is obvious： large-size dominant species such as Biddulphia sinensis of the 1950s were gradually replaced by small-size ones such as Cyclotella striata and Nitzschia closterium,and species that still maintain dominant such as Skeletonema costatum are also small ones,leading the whole phytoplankton community of smaller size.Cell density of phytoplankton community increased greatly,among which cell density of the most dominant species Skeletonema costatum have been increasing in exponent function.Margalef index of phytoplankton community decreased,indicating decline of biodiversity of the community,and dominant character of Skeletonema costatum increased.Generally,the structure of the entire phytoplankton community is becoming more and more singular and unstable,which makes the occurrence of red tides more frequent.The succession in the phytoplankton community is related to the long-term changes in marine environment,influenced by human activities and global climate changes,especially the increases of nutrient content.

Speciation, distribution, and potential ecological risk assessment of heavy metals in Xiamen Bay surface sediment

Based on the survey of surface sediment in Xiamen Bay in October 2011, the speciation, distribution, and potential ecological risk assessment of heavy metals （Cu, Pb, Zn, Cd, and Cr） in this area were studied us-ing the sequential extraction method and ecological risk assessment method. The results indicated：（1） the total concentrations of these heavy metals were influenced by runoff, industrial wastewater, and sewage, and were all higher in the coastal area than the offshore area while the highest area of Pb was a little far-ther away from the coastal water due to atmosphere deposition;（2） sequential extractions suggested that Cu was mainly composed with residual and Fe/Mn-oxide bound fractions, Pb was bound to Fe/Mn-oxide, Zn and Cr were dominated by residual, and Cd bound to exchangeable and carbonate fractions; （3） the order of migration and transformation sequence was Cd＆gt;Pb＆gt;Cu＆gt;Zn＆gt;Cr and the degree of pollution was Cd＆gt;Pb＆gt;Cu＆gt;Zn＆gt;Cr;and （4） the ratios of the secondary and primary phases showed that Zn and Cr were both clean, Cu may be polluted, Pb was moderately polluted, while Cd was heavily polluted.

Distribution characteristics of total mercury and methylmercury in the topsoil and dust of Xiamen, China

The levels and distribution of mercury （Hg） species, including total mercury （THg） and methylmercury （MeHg） in the topsoil and dust collected from twenty sampling stations located in different land function areas of Xiamen, China, were investigated. The THg concentrations in topsoil ranged from 0.071 to 1.2 mg/kg, and in dust ranged from of 0.034 to 1.4 mg/kg. For stations where the THg of dust was less than 0.31 mg/kg, THg concentrations in the topsoil were significantly correlated to those in the corresponding dust （r = 0.597, n = 16, P = 0.014）. The MeHg concentrations in topsoil were varied between 0.14 and 5.7 μg/kg. The ratios of MeHg/THg in the topsoil ranged from 0.069% to 0.74%. The range of MeHg concentration in the dust were 0.092-2.3 μg/kg. The ratios of MeHg/THg in the dust were at the same level as those in the topsoil. The MeHg concentrations in both topsoil and dust were linked to corresponding THg concentrations and soil organic matter. Neither THg nor MeHg concentration in the topsoil and dust was obviously linked to the land function.

Abundance and distribution of dinoflagellate cysts in Xiamen Western Harbor

In a grid investigation, dinoflagellate cysts were collected from sediments in Xiamen Western Harbor in May of 2000, from which five species of cysts were identified: Alexandrium tamarensis, A. minutum, Lingulodinium polyedra, Gonyaulax scrippsae and Gymnodinium catenatum, account for about 21% in the species composition. The quanti-tative analysis of the sediments shows that the number of dinoflagellate cysts varies from 51 to 256 cysts/g of sediment, the highest value (>200 cysts/g) being recorded at the stations of the central part of the bay, while the lowest (<100 cysts/g) at the bay mouth. A good linear relationship is found between cyst amount and fine-grained sediments. Complex physiognomies on the seabed, topographty in the bay and weak water exchange are the main factors not only in cyst accumulation but also in their distribution pattern, and have resulted in the difference in cyst densities between the inner bay and the outer bay in the harbor.

The study on three-dimensional numerical model and fronts of the Jiulong Estuary and the Xiamen Bay

Applying the methods of on-site observation and dynamic model, the research on the fronts at the Jiulong Estuary has been carried out, during which spatial and temporal distribution, dynamic characteristics and formation mechanism of salinity fronts are analyzed and discussed. The research shows that the estuarine fronts mainly lie in the area from the Jiyu Islet to the Haimen Island, outside of Yuweizai to Hulishan cross-section, the near coast of Yuweizai and the south of the Songyu-Gulangyu Channel. The fronts in the former two regions are formed directly by plume, while the one near the coast of Yuweizai is a tidal intrusion front caused by flood current and the one at the south of the Songyu-Gulangyu Channel is the result of current shear transformation. Under normal circumstances, fresh water of the Jiulong River mainly influences the inside of the Xiamen Bay, and when it is in typhoon seasons, plume front can affect the Taiwan Strait and has an effect on the biogeochemical Drocesses in the strait.

Spatial variability of summer and autumn phytoplankton community structure in Xiamen Western Bay based on pigment analysis

The spatial variations of phytoplankton community structure in the Xiamen Western Bay during the summer and autumn cruises in 2001 were investigated based on HPLC analysis of photosynthetic pigments in algal cells and CHEMTAX processing of pigment data. The Chl a concentration reached 18.9 μg/L in the summer and declined to 0.28–2.17 in the autumn, respectively, consistent with the observation of diatom blooms in June. Among the accessory pigments, fucoxanthin was consistently the most abundant, ranging from 0.172 to 8.46 μg/L, with the maximum concentrations in June. 19’- hexfucoxanthin and alloxanthin were the other two abundant pigments in the summer and autumn. In addition, 19’-butanoyloxyfucoxanthin or peridinin was also important in late autumn. Generally the biomass of all the phytoplankton or each group was higher in the inner part than the mouth of this bay, represented by Chl a. CHEMTAX processing revealed the dominance of diatoms with their contribution of 14.6%–52.5% to the total Chl a, but its importance decreased in the autumn. Cryptophytes and Haptophytes, with an average contribution of 16.9%–31.4% and 12.1%–26.3%, were the other two important groups, especially in the autumn. On the contrary, Dinoflagellates and Chlorophytes were the minor groups, but the former became important sporadically in the autumn. It was suggested that there was distinctive variation in both the phytoplankton community structure and biomass between summer and autumn in the Xiamen Western Bay and the latter was coupled to the changes in temperature and dissolved oxygen. However, the spatial variation of the phytoplankton community structure was not as clear as the trend in the biomass of phytoplankton among all the sites in this bay.

Three-dimensional hydrodynamic model of Xiamen waters

A semi-implicit and Eulerian - Lagrangian finite difference method for three-dimensionalshallow flow has been extended to a more complete system of equations incorporating second-moment turbulence closure model and transport equations of salinity and temperature. The simulation for flooding and drying of mudflats has been improved. The model is applied to Xiamen waters. Based on extensive survey data, water level elevation, temperature and salinity field along the eastern open boundary and at the Jiulong River inlets and runoffs are analyzed, specified and calibrated. The computed results show good agreement with the measured data, reproduce flooding, emergence of large and complex mudflat region.

Grazing impact of microzooplankton on phytoplankton in the Xiamen Bay using pigment-specific dilution technique

Phytoplankton group-specific growth and microzooplankton grazing were determined seasonally using the dilution technique with high-performance liquid chromatography （HPLC） in the Xiamen Bay, a subtropical bay in southeast China, between May 2003 and February 2004. The results showed that growth rates of phytoplankton ranged from 0.71 to 2.2 d^-1 with the highest value occurred in the inner bay in May. Mierozooplankton grazing rates ranged from 0.5 to 3.1 d^-1 with the highest value occurred in the inner bay in August. Microzooplankton grazing impact ranged from 39% to 95% on total phytoplankton Chl a biomass, and 65% to 181% on primary production. The growth and grazing rates of each phytoplankton group varied, the highest growth rate （up to 3.3 d^-1 ） was recorded for diatoms in August, while the maximum grazing rate （ up to 2.1 d ^-1 ） was recorded for chlorophytes in February in the inner bay. Among main phytoplankton groups, grazing pressure of microzooplankton ranged from 10% to 83% on Chl a biomass, and from 14% to 151% on primary production. The highest grazing pressure on biomass was observed for cryptophytes （83%） in August, while the maximum grazing pressure on primary production was observed for eyanobacteria （up to 151% ） in December in the inner bay. Net growth rates of larger phytoplanktons （diatoms and dinoflagellates） were higher than those of smaller groups （ prasinophytes, chlorophytes and cyanobacteria）. Relative preference index showed that microzooplankton grazed preferentially on prasinophytes and avoided to harvest diatoms in cold seasons （December and February）.

REPRODUCTIVE RATE OF A MARINE PLANKTONIC COPEPOD LABIDOCERA EUCHAETA GIESBRECHT IN XIAMEN HARBOR

Reproductive rate of a marine planktonic copepod Labidocera euchaeta Giesbrecht in Xiamen Harbor was studied during the period from April 1986 to August 1987. Results showed that rate of egg production (F, eggs/(,d)) was positively correlated with temperature (T,℃) ) and body weight of spawning female (We,ugC ) as: F=0.0637 (T-7)0.7445Wc. Each month a maximum rate of egg production occurred at one of the five experimental temperatures (10°, 15°, 20°, 25°, and 30℃) near the monthly mean field temperature. The available food density (P, ugC/ml) had significant effect on specific rate of egg production (Fc, %C/d) as :Fc=0.1732(P-0.0179)/P. The gross efficiency of egg production of ca 62% in carbon was independent of food density snd ingestion rate. Observations on in situ egg production and hatching rate demonstrated that this species reproduces continuously all the year round, with summer as its high reproductive season and winter a low one. Ten generations a year is also suggested based on the

Two New Species of Free-Living Marine Nematodes of the Desmodoridae from Mangrove Wetlands of Xiamen Bay, China

Mangroves are unique in their biodiversity,but studies on their meiobenthic biodiversity in China are scarce.Despite the importance of mangroves,little work has been done on the classification of nematodes in mangrove wetlands.Fujian Province is the most northern point of China’s natural mangrove distribution,and it is also one of the provinces with the earliest constructed mangrove forest.In this paper,two new free-living marine nematode species of Desmodoridae from the Xiamen mangrove wetlands in China are described.Metachromadora xiamenensis sp.nov.is characterized by a cylindrical body,and smooth head capsule set off from the rest of the body.The cuticle is finely annulated and thickened at the midbody.Lateral ridges run from the posterior end of the pharynx to the middle of the tail.The amphid foveae is loop shaped and opens at the top with a double contour amphidial,pharynx with bipartite cuticularized internal cavity.There are 18 tubular precloacal supplements and tail with three small protuberances.Molgolaimus euryformis sp.nov.is characterized by a relatively short and plump body with finely annulated cuticle,which is particularly obvious in the tail.The head is small and wide with intensive striates.The inner and outer labial sensilla are indistinct with short spicules and ventral apophysis,a gubernaculum with a block-shaped hook,a swollen conical-cylindrical tail and an absence of precloacal supplements.

Analysis on the situation and countermeasures of water resources supply and demand in the cities of small and medium-sized river basins along southeast coast of China-taking Xiamen City as an example

The small and medium-sized river basins along southeast coast of China hold comparatively abundant water resources.However,the rapid resources urbanization in recent years has produced a series of water problems such as deterioration of river water quality,water shortage and exacerbated floods,which have constrained urban economic development.By applying the principle of triple supply-demand equilibrium,this paper focuses on the estimation of levels of water supply and demand in 2030 at different guarantee probabilities,with a case study of Xiamen city.The results show that water shortage and inefficient utilization are main problems in the city,as the future water supply looks daunting,and a water shortage may hit nearly 2×10^(8)m^(3)in an extraordinarily dry year.Based on current water supply-demand gap and its trend,this paper proposes countermeasures and suggestions for developing and utilizing groundwater resources and improving the utilization rate of water resources,which can supply as a reference for other southeast middle-to-small-sized basin cities in terms of sustainable water resources and water environment protection.

Pollution Characteristics of PM2.5 during a Typical Haze Episode in Xiamen, China

In this study, mass concentrations and chemical compositions of fine particles, mass concentrations of coarse particles, light extinction, and meteorological parameters in the atmosphere ofXiamenwere presented and analyzed to study the chemical and optical characteristics of a typical haze episode from Dec 25, 2010 to Jan 1, 2011. The major chemical compositions of PM2.5, such as water soluble inorganic ions (WSIIs), carbonaceous fractions (mainly composed of organic carbon (OC) and elemental carbon (EC)), and elements were determined. The results showed that with the typical haze episode process, the concentrations of PM2.5 mass, WSIIs, OC, EC, and TE first increased and then decreased. The average concentrations of PM2.5 mass in the stages of Before Haze, During Haze, and After Haze were (88.80 ± 19.97), (135.41 ± 36.20), and (96.35 ± 36.26) μg/m3, respectively. The corresponding average concentrations of secondary organic carbon (SOC) were 6.72, 8.18, and 10.39 μg/m3, accounting for 46.5%, 27.0%, and 61.0% of OC, respectively. S42- , NO3-, and NH4+ were three major WSIIs species, accounting for 31.4%, 26.0%, and 12.1% of total WSIIs. The major elements in PM2.5 were S, K, Fe, Zn, Pb, Ti, and Mn, covering 97.9% of the total elements, while the percentage of the other ten elements was only 2.1%. The average value of light extinction coefficients (bext) was 371.0 ±147.1 Mm-1 during the typical haze episode. The average percentage contributions to bext were 39.3% for organic mass, 19.9% for elemental carbon, 16.0% for ammonium sulfate, 13.0% for coarse mass, and 11.8% for ammonium nitrate.

MECHANISM OF PHOSPHORUS RELEASE FROM THE SEDIMENT-WATER INTERFACE IN XIAMEN BAY

The adsorption/desorption of phosphorus across the sediment -water interface is the main mechanism that controls the buffering capacity of DRP in coastal and estuarine water. Determination by three processes revealed that: 1) DRP flux from early diagenesis in surface sediment is F = 31.9ug/(m2.d ), which is only 1/1600 of the ammonia released; 2) at normal temperature and in the long term, the TDP released by adsorption /desorption across the sediment-water interface is a function of the major environmental factors; and 3) based on the determined SODR and assumed average water depth H(m) and residence time tR(d), the maximum flux of DRP can be estimated.

SPATIOTEMPORAL DISTRIBUTION OF BACTERIAL ABUNDANCE,BIOMASS,PRODUCTIVITY AND TOTAL COLIFORMS IN XIAMEN WESTERN SEA AREA

This paper deals with the application of microbiological parameters obtained by usingAODC and SEM methods, and ~3H-thymidine incorporation into DNA method for quantitative estimation ofbacterial biomass、productivity and growth doubbing time in order to gain better understanding of the role ofmarine bacteria and their activities in Xiamen western sea waters. The results showed that in the seawatersurface, the mean value of total coliforms was 1. 3×104 cells/ml; the mean value of bacterial productionwas 10. 5×10~8 cells/(ml·h), the growth doubling time ranged from 0. 9 to 71. 3 hours. In the bottom sea-

ANALYSIS OF ENVIRONMENTAL FEATURES OF RED TIDE IN THE WESTERN WATERS OF XIAMEN BAY

This article reports main results of investigations on red tide in western waters of Xiamen Bay from Jan. to Dec. 1987, and elaborates on the relationship between the change of phytoplanktonic number and main environmental factors there. The cause and the method for judging and monitoring of red tide are discussed.

KINETICS OF LEAD ADSORPTION BY XIAMEN BAY SEDIMENTS

The kinetics of Pb adsorption in seawater by surface sediments from Xiamen Bay was simulated and the effects of seawater conditions were studied . When water temperature changed from 20 to 30℃, pH from 5 to 8 and salinity from 30 to 4 . the adsorption rate increased by about 50% , one order of magnitude and 5 times, respectively . A negative exponential relation between the adsorption rate and salinity has been found . The adsorption processes can be simulated by the exchange- equilibrium kinetic model . Adsorption rate constant, apparent activation energy and equilibrium adsorptive capacity have been quantitatively determined . The adsorption of Pb by sediments is essentially a chemical action .

A culture-dependent survey of thermophilic bacteria from hot springs in Xiamen area in China

Microbes are believed to play important roles in ecosystem function in many environments.The hot springs of Xiamen Island are close to the Xiamen Sea,and may have some characteristics different from those of inland hot springs.Microbes living in the hot springs of Xiamen may have new characteristics.However,little is known about microbial communities of hot springs close to the Xiamen Sea.A culture-dependent survey of microbial population in the Xiamen hot springs was performed by using an approach combining total cellular protein profile identification and 16S rRNA gene sequencing.A total of 328 isolates of bacteria were obtained from liquid and sediment samples from the Xiamen hot springs,including neutrophilic thermophilic bacteria and moderately thermophilic acidophiles.Neutrophilic thermophilic bacteria,which grow at a temperature range of 55-90℃ including Rhodothermus marinus（Strain 1）,Thermus thermophilus（Strain 2）,Thermus thiopara（Strain 3）,Geobacillus stearothermophilus（Strain 4）,Geobacillus thermoleovorans（Strain 5）,and Pseudomonas pseudoalcaligenes（Strain 6）,were recovered by 2216E plates.Moderately thermophilic acidophiles,which can grow at temperatures above 50℃ and a pH range of 1.8-3.5 such as Alicyclobacillus acidoterrestris（Strain 8）,Sulfobacillus acidophilus（Strain 9）,and Sulfobacillus thermosulfidooxidans（Strain 10）,were isolated on selective solid medium containing sulfur and Fe2＋.Among these strains,Rhodothermus marinus,Thermus thermophilus and Geobacillus stearothermophilus are not only thermophiles,but also halophiles.One bacterium strain（Strain 6） shared 99% nucleotide sequence homology with Pseudomonas pseudoalcaligenes on the 16S rRNA gene sequence,but was quite different from Pseudomonas pseudoalcaligenes in biological characteristics,suggesting that it may represent a novel thermophilic species.Results indicated that various species of neutrophilic thermophiles and moderately thermophilic acidophiles were widely distributed in the Xiamen hot springs and that Rhodothermus marinus and Thermus thermophilus dominated the cultivable microbial community.

Countermeasure Research on the Drainage and Water-logging Prevention of Coastal Cities:A Case Study of Yingping District in Xiamen

According to the drainage problems emerging from the several torrential rainstorm in domestic coastal cities in the last two years, especially the issues that the drainage and waterlogging prevention of coastal cities are susceptible to the tide level of open seas, this paper took the reconstruction of Yingping District in Xiamen, a typical coastal area, as a case study, analyzed the main waterlogging causes of the district under the influences of the average annual tide level and storm tide caused by typhoon with the application of drainage model, and came up with reasonable implementation strategies for reconstruction;besides, this paper also assessed and divided the waterlogging risks of the district under the influences of storm tide and applied engineering measures as well as non-engineering measures to prevent the urban cities from water-logging hazards. It is expected that the study would provide reference for the reconstruction of coastal cities in drainage and water-logging prevention.

DISTRIBUTION AND COMPOSITION OF PAHs IN SURFACE WATERS, POREWATER AND SEDIMENTS FROM XIAMEN WESTERN BAY

Xiamen Western Bay’s water and sediment quality were studied by determining the levels of sixteen polycyclic aromatic hydrocarbons (PAHs) in water, porewater and sediment samples from nine locations in the bay. Total PAH concentrations varied from 106 to 945 ng/l in water, below detection to 3548 ng/l in porewater, and 247 to 480 ng/g dry weight in surface sediments. PAHs levels in porewater were higher than those in surface water, due to the preference of these hydrophobic compounds for sedimentary phase instead of water. Such a concentration gradient implies a potential flux of pollutants from sediments to overlying water. The PAHs levels in sediments were one to several orders of magnitude lower than those in 1993, suggesting their decreased input in recent years and possible degradation with time.