Feeding and egg production of the planktonic copepod Calanus sinicus in spring and autumn in the Yellow Sea, China

Shipboard incubations were conducted in spring (April) and autumn (October/November) 2006 to measure the feeding and egg production rates (EPR) of Calanus sinicus in the Yellow Sea, China. The ingestion rate (2.08-11.46 and 0.26-3.70 mu g C female(-1) day(-1) in spring and autumn, respectively) was positively correlated with microplankton carbon concentrations. In the northern part of the Yellow Sea, feeding on microplankton easily covers the respiratory and production requirements, whereas in the southern part in spring and in the frontal zone in autumn, C. sinicus must ingest alternative food sources. Low ingestion rates, no egg production and the dominance of the fifth copepodite (CV) stage indicated that C. sinicus was in quiescence inside the Yellow Sea Cold Bottom Water (YSCBW) area in autumn. Calanus sinicus ingested ciliates preferentially over other components of the microplankton. The EPR (0.16-12.6 eggs female(-1) day(-1) in spring and 11.4 eggs female(-1) day(-1) at only one station in autumn) increased with ciliate standing stock. Gross growth efficiency (GGE) was 13.4% (3-39%) in spring, which was correlated with the proportion of ciliates in the diet. These results indicate that ciliates have higher nutrient quality than other food items, but the low GGE indicates that the diet of C. sinicus is nutritionally incomplete.

Penning trap mass measurements on nobelium isotopes

The Penning trap mass spectrometer SHIPTRAP at GSI Darmstadt allows accurate mass measurements of radionuclides, produced in fusion-evaporation reactions and separated by the velocity filter SHIP from the primary beam. Recently, the masses of the three nobelium isotopes No252-254 were determined. These are the first direct mass measurements of transuranium elements, which provide new anchor points in this region. The heavy nuclides were produced in cold-fusion reactions by irradiating a PbS target with a Ca-48 beam, resulting in production rates of the nuclei of interest of about one atom per second. In combination with data from decay spectroscopy our results are used to perform a new atomic-mass evaluation in this region.

Determination of photochemically produced hydroxyl radicals in seawater and freshwater

A variety of short-lived, reactive chemical species (i.e. free radicals and excited state species) are known to be photochemically produced in natural waters. Some of these transients may strongly affect chemical and biological processes, and they have been implicated in the degradation of organic pollutants and natural organic compounds in aqueous environments. Previous studies demonstrated that the highly reactive hydroxyl radical (OH) is photochemically formed in seawater. However, the quantitative importance of this key species in the sea has not been previously studied because of past analytical limitations. By using a highly sensitive probe based on α-H atom abstraction from methanol, we were able to measure production rates and steady-state concentrations of photochemically produced OH radicals in coastal and open ocean seawater and freshwaters. The validity of the method was tested by intercalibrating with an independent, OH-specific reaction, hydroxylation of benzoic acid, and also by competition kinetics experiments. Our OH production rates and steady-state concentrations for freshwaters are in excellent agreement with those measured by previous investigators for similar waters. In contrast, for seawater, the values we measured are 1–3 orders of magnitude higher than previously predicted by models, indicating that there is a major unknown photochemical OH source (s) in seawater.

Photo-sensitized oxidation in natural water via .OH radicals

A method is presented for determining production and consumption rates of .OH radicals produced photochemically in natural surface waters. It is based on the determination of the kinetics by which the concentration of a specified trace compound decreases during irradiation. In samples from Lake Greifensee (Switzerland) low production rates for .OH limit its possible effects. In addition, fast consumptions by the natural dissolved organic solutes and by the bicarbonate protect organic micropollutants from oxidation by .OH. Neither direct nor indirect H2O2 photolysis was a significant source of .OH in the lakewater studied lacking iron, whereas nitrate photolysis could have been a source. Comparison with reaction kinetic formulations allows generalizations for other types of waters.

Effects of increased pCO(2) and temperature on the North Atlantic spring bloom. I. The phytoplankton community and biogeochemical response

The North Atlantic spring bloom is one of the largest annual biological events in the ocean, and is characterized by dominance transitions from siliceous (diatoms) to calcareous (coccolithophores) algal groups. To study the effects of future global change on these phytoplankton and the biogeochemical cycles they mediate, a shipboard continuous culture experiment (Ecostat) was conducted in June 2005 during this transition period. Four treatments were examined: (1) 12 degrees C and 390 ppm CO2 (ambient control), (2) 12 degrees C and 690 ppm CO2 (high pCO(2)) (3) 16 degrees C and 390 ppm CO2 (high temperature), and (4) 16 degrees C and 690 ppm CO2 ('greenhouse'). Nutrient availability in all treatments was designed to reproduce the low silicate conditions typical of this late stage of the bloom. Both elevated pCO(2) and temperature resulted in changes in phytoplankton community structure. Increased temperature promoted whole community photosynthesis and particulate organic carbon (POC) production rates per unit chlorophyll a. Despite much higher coccolithophore abundance in the greenhouse treatment, particulate inorganic carbon production (calcification) was significantly decreased by the combination of increased pCO(2) and temperature. Our experiments suggest that future trends during the bloom could include greatly reduced export of calcium carbonate relative to POC, thus providing a potential negative feedback to atmospheric CO2 concentration. Other trends with potential climate feedback effects include decreased community biogenic silica to POC ratios at higher temperature. These shipboard experiments suggest the need to examine whether future pCO2 and temperature increases on longer decadal timescales will similarly alter the biological and biogeochemical dynamics of the North Atlantic spring bloom.

The Experimental and Numerical Studies on Gas Production from Hydrate Reservoir by Depressurization

A set of experimental system to study hydrate dissociation in porous media is built and some experiments on hydrate dissociation by depressurization are carried out. A mathematical model is developed to simulate the hydrate dissociation by depressurization in hydrate-bearing porous media. The model can be used to analyze the effects of the flow of multiphase fluids, the kinetic process and endothermic process of hydrate dissociation, ice-water phase equilibrium, the variation of permeability, convection and conduction on the hydrate dissociation, and gas and water productions. The numerical results agree well with the experimental results, which validate our mathematical model. For a 3-D hydrate reservoir of Class 3, the evolutions of pressure, temperature, and saturations are elucidated and the effects of some main parameters on gas and water rates are analyzed. Numerical results show that gas can be produced effectively from hydrate reservoir in the first stage of depressurization. Then, methods such as thermal stimulation or inhibitor injection should be considered due to the energy deficiency of formation energy. The numerical results for 3-D hydrate reservoir of Class 1 show that the overlying gas hydrate zone can apparently enhance gas rate and prolong life span of gas reservoir.

Effects of iron on growth, pigment content, photosystem II efficiency, and siderophores production of Microcystis aeruginosa and Microcystis wesenbergii

Changes in growth, photosynthetic pigments, and photosystem II (PS II) photochemical efficiency as well as production of siderophores of Microcystis aeruginosa and Microcystis wesenbergii were determined in this experiment. Results showed growths of M. aeruginosa and M. wesenbergii, measured by means of optical density at 665 nm, were severely inhibited under an iron-limited condition, whereas they thrived under an iron-replete condition. The contents of chlorophyll-a, carotenoid, phycocyanin, and allophycocyanin under an iron-limited condition were lower than those under an iron-replete condition, and they all reached maximal contents on day 4 under the iron-limited condition. PS II photochemical efficiencies (maximal PS II quantum yield), saturating light levels (I-k ) and maximal electron transport rates (ETRmax) of M. aeruginosa and M. wesenbergii declined sharply under the iron-limited condition. The PS II photochemical efficiency and ETRmax of M. aeruginosa rose , whereas in the strain of M. wesenbergii, they declined gradually under the iron-replete condition. In addition, I-k of M. aeruginosa and M. wesenbergii under the iron-replete condition did not change obviously. Siderophore production of M. aeruginosa was higher than that of M. wesenbergii under the iron-limited condition. It was concluded that M. aeruginosa requires higher iron concentration for physiological and biochemical processes compared with M. wesenbergii, but its tolerance against too high a concentration of iron is weaker than M. wesenbergii.

Growth and production of free-living heterotrophic nanoflagellates in a eutrophic lake - Lake Donghu, Wuhan, China

In situ growth of heterotrophic nanoflagellates (HNF) in Lake Donghu, a eutrophic shallow lake in mainland China, was studied from January 1999 to March 2000 using a modified Weisse protocol. The study results indicated that the growth rates of HNF showed pronounced seasonal variation (-0.37-1.25 d(-1)), reaching the maximum during spring to early summer. When the water temperature was higher than 25.5 degreesC, HNF growth was inversely proportional to water temperature. There was an effect by bacterial abundance and autotrophic picoplankton on HNF growth that depended on location. HNF biomass was the highest in late spring, and the HNF production ranged from -2.25 to 35.45 mg l(-1) d(-1) with mean of 3.17 mg l(-1) d(-1). When considered in the context of biomass and production data for zooplankton in Lake Donghu, it was evident that HNF contributed significantly to the total zooplankton production in Lake Donghu. These in situ studies indicate that temperature and food supply are the major determinants of HNF abundance and productivity.

Estradiol stimulates growth hormone production in female goldfish

The effects of estradiol (E(2)) on growth hormone (GH) production was investigated in gonad-intact female goldfish. It was first necessary to generate a specific antibody for use in immunocytochemistry, Western, and dot-blot analyses of GH production. To accomplish this, grass carp GH (gcGH) cDNA was cloned by the reverse transcription polymerase chain reaction (RT-PCR) and expressed in Echerichia coli and a specific polyclonal antibody to recombinant gcGH was generated in the rabbit. In Western blot, the anti-gcGH antibody specifically immunoreacted with recombinant gcGH, purified natural common carp GH, and with a single 21.5-kDa GH form from pituitary extracts of grass carp, common carp, goldfish, and zebrafish but not salmon, trout, or tilapia. Intraperitoneal injection of the recombinant gcGH enhanced the growth rates of juvenile common carp demonstrating biological activity of this GH preparation. Electron microscopic studies showed that the anti-gcGH-I antibody specifically reacted with GH localized in the secretory granules of the goldfish somatotroph. Using anti-gcGH-I in a dot-blot assay, it was found that in vivo implantation of solid silastic pellets containing E(2) (100 mu g/g body weight for 5 days) increased pituitary GH content by 150% in female goldfish. In a second, independent study employing a previously characterized anticommon carp GH antibody for radioimmunoassay, it was found that E(2) increased pituitary GH content by 170% and serum GH levels by approximately 350%. The E(2)-induced hypersecretion of GH and increase in pituitary GH levels was not associated with changes in steady-state pituitary GH mRNA levels, suggesting that this sex steroid may enhance GH synthesis at the posttranscriptional or translational level. Previous observations indicate that GH can stimulate ovarian E(2) production. The present results show that E(2) can in turn stimulate GH production, indicating the existence of a novel pituitary GH-ovarian feedback system in goldfish. (C) 1997 Academic Press.

Experimental investigation of production behavior of methane hydrate under ethylene glycol injection in unconsolidated sediment

This article investigates the gas production behavior from methane hydrate (MH) in porous sediment by injecting ethylene glycol (EG) solution with the different concentrations and the different injection rates in an one-dimensional experimental apparatus. The results suggest that the gas production process can be divided into the four stages: (1) the initial injection, (2) the EG diluteness, (3) the hydrate dissociation, and (4) the remained gas output. Nevertheless, the water production rate keeps nearly constant during the whole production process. The production efficiency is affected by both the EG concentration and the EG injection rate, and it reaches a maximum with the EG concentration of 60 wt %.

Neutron production at the heavy ion research facility in Lanzhou

In this work, the neutron radiation field at Heavy Ion Research Facility in Lanzhou (HIRFL) was investigated. Total neutron yields, spectra and angular distributions in the bombardment of various thick targets by C-12 and O-18 ions with energies up to 75 MeV/u were obtained using the activation method. The neutron dose equivalent rates of 60 MeV/u O-18 on various thick targets at different angles were measured with a modified A-B remmeter. Our results are compared with those of other reports.

Production and application of filaments of Grateloupia turuturu (Halymeniaceae, Rhodophyta)

Filaments from Grateloupia turuturu were obtained through germination of spores, regeneration from fragments of discoid crusts and erect thalli. The rates of filament formation through the three ways were 5.3 +/- 1.2%, 100%, and 62.3 +/- 5.6%, respectively. Discoid crusts were the best materials for the production of filaments. The obtained filaments were cloned in stationary and aerated culture. The differentiations of filaments were observed. When attached to the substrata, filaments differentiated into discoid crusts from which erect thalli grew, whereas for filaments in suspension culture, some cells in the filaments differentiated into spherical structures that also formed new erect thalli. Moreover, fragments of filaments (< 100 mu m) were seeded onto nori-nets. The regenerated plantlets grew into adult thalli in field cultivation.

Seasonal variation of reproduction rates and body size of Calanus sinicus in the Southern Yellow Sea, China

Annual variations of egg production rate (EPR) and clutch size of Calanus sinicus, as well as body size of females (prosome length and dry weight), were investigated at a series of stations in the Southern Yellow Sea by onboard incubation. Calanus sinicus was spawning in all the 11 cruises investigated, and the annual variation of EPR was bimodal. Monthly average EPR was highest from May to July, respectively, 5.97, 5.36 and 6.30 eggs female(-1) d(-1), then decreased dramatically to only 1.37 eggs female(-1) d(-1) in August and attained the lowest 1.07 eggs female(-1) d(-1) in October. In November, average EPR increased again to 4.31 eggs female(-1) d(-1). Seasonal variation of clutch size was similar to EPR, except that it decreased gradually after August rather than dramatically as did EPR. Prosome length of females was maximum in May and minimum in October, but dry weight was highest in November. Monthly average EPR correlated better with prosome length than dry weight, while clutch size was rather determined by dry weight of females. It is suggested that egg production of C. sinicus was active during two discontinuous periods when both surface and bottom temperature fell into its favorite range (i.e. 10-23degreesC), and different reproductive strategies were adopted in these two reproductive peaks: other than the highest EPR, longer prosome length was also achieved by C. sinicus from May to July, while females in November developed shorter bodies but accumulated more energy for reproduction.

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.

Morphological and reproductive response of Caragana microphylla to different stocking rates

Understanding the effect on host plants of defending against herbivores is important in grazing ecology and grassland management. In this study, the morphological and reproductive responses of Caragana microphylla Lam. to grazing sheep were investigated using a 15-year grazing experiment with six stocking rates in the Inner Mongolia steppe of China. Plant height, rachis length, leaflet size, and number of pods decreased significantly, whereas spine density and length increased significantly with increased stocking rate. Significant negative correlations were observed between production of vegetative and reproductive organs and defensive organs, indicating that it is costly for C. microphylla to defend against herbivores and that morphological miniaturization and a tradeoff between production and defense were main responses of C. microphylla to herbivores. (c) 2006 Elsevier Ltd. All rights reserved.