Dynamics of picoplankton in the Nansha Islands area of the South China Sea

Dynamics of major picoplankton groups, Synechococcus (Syn), Prochlorococcus (Pro), picoeukaryotes (Euk) and heterotrophic bacteria (Bact) was investigated by flow cytometry for the first time in the Nansha Islands area in the South China Sea. Averaged over the whole investigation area, depth-weighted integrated cell abundance (DWA) of Syn, Pro, Euk and Bact was 1.6 (0.4-5.7)×103, 5.4 (0.1-7.3)×104, 0.7 (0.2-2.2)×103, and 2.3 (1.4-3.2)×105 cells/mL respectively. Picoautotrophic cell abundance was low in the northwest part of the Nansha Islands where surface water temperature was low and the upper mixed layer was shallow. Concurrently, a surface maximum vertical distribution pattern was observed in this area. While in the southeast and east zones where temperatures were relatively higher and nitraclines were deeper, picoplankton is abundant and a subsurface maximum around 50-75 m is observed. Coupling of horizontal and vertical distribution patterns of picoplankton abundance and hydrological status was found, suggesting a strong influence of currents and water column structure on picoplankton distribution in the investigation area. Contrary to that in the shelf water in the East China Sea, the relationship between Pro and Bact in the Nansha Islands area in the South China Sea was not significantly negative but weakly positive. Moreover, a similar distribution pattern of Syn and Pro was observed. Possible reasons for these differences in the two marine regimes were discussed.

Bioconcentration of polycyclic aromatic hydrocarbons in roots of three mangrove species in Jiulong River Estuary

The polycyclic aromatic hydrocarbons(PAHs) concentrations were determined in the root of three mangrove species(Kandelia candel, Avicennia marina and Bruguiera gymnorrhiza) and their growing environment(sediment) in mangrove wetlands of Jiulong River Estuary, Fujian, China. The total PAHs(16 parent PAHs) in mangrove sediments ranged from 193.44 to 270.53 ng/g dw, with a mean value of 231.76±31.78 ng/g dw. Compared with other mangrove and coastal marine sediments, the PAHs concentrations of all the sampling areas in this study were at relatively lower level. The total PAHs(13 parent PAHs) values varied from 30.83 to 62.73 ng/g dw in mangrove roots. Benzo[a]pyrene(five-ring), fluoranthene(four-ring) and pyrene(four-ring) dominated in mangrove sediments. Based on ratios of phenathrene/anthracene, fluoranthene/pyrene and fluoranthene/pyrene + fluoranthene, the main possible sources of surface sediment PAHs were identified as grass, wood or coal combustion for mangrove wetlands of Jiulong River Estuary. Naphthalene(two-ring) and phenathrene(three-ring) were the most abundant compounds in mangrove roots. Sediment-to-vegetation bioconcentration factors(BCF SV s) were calculated and their relationships with PAHs' physico-chemical properties were investigated. The average BCF SV s of PAHs for three mangrove species roots were almost all under the level of 1 except for naphthalene. Good linear relationship between BCF SV values for mangrove roots and PAHs water solubility, octanol-water partitioning coefficients was derived in present study. The solubility and the octanol-water partition coefficient were proved to be good predictors for the accumulation of PAHs in mangrove roots, respectively.

Distribution pattern of marine flagellate and its controlling factors in the central and north part of the Huanghai Sea in early summer

A survey was carried out in the central and north part of the Huanghai Sea (34.5° -37.0°N, 120.5°-124.0°E) during June 12-27, 2000. It was found that the abundance of marine flagellate ranged from 45 to 1 278 cell/ml, 479 cell/ml in average. Flagellate was more abundant in the central part than in the north part of Huanghai Sea, and the abundance decreased with the increasing distance from the coast, showing a similar distribution pattern with isotherm. Vertically, high density of flagellate was always presented in the bottom of thermocline, and formed a dense accumulation in the central area of the Huanghai Sea Cold Water Mass. The effects of physical and biological factors on the distribution of marine flagellate in early summer were discussed. Water temperature (especially the existence of thermocline) rather than salinity showed significant effect on the distribution pattern of marine flagellate in the Huanghai Sea in early summer. When comparing the abundance of marine flagellate with that of other microorganisms, it revealed a comparatively stable relationship among these organ-hisms, with a ratio of heterotrophic bacteria: cyanobacteria: flagellate: dinoflagellate: ciliate being 105 :103:102:101:100.

Phylogenetic diversity of ribulose-1, 5-bisphosphate carboxylase/oxygenase large subunit genes of bacterioplankton in the East China Sea

Phylogenetic diversity of Form I and Form II ribulose1, 5-bisphosphate carboxylase/oxygenase (RubisCO) largesubunit (rbcL) genes in the inshore and offshore areas of the East China Sea were investigated. Two new primer setswere designed for amplifying partial sequences of rbcL genes from Proteobacteria. Four rbcL gene clone libraries wereconstructed by amplification and cloning of approximately 640~800 bp sequences of bacterioplankton populations.The method of screening library by denaturing gradient gel electrophoresis (DGGE) was introduced. The resultsshow that the diversity of Form I is higher in offshore waters with higher salinity and lower productivity, while thatof Form II is higher at the inshore station where salinity is lower and productivity is higher. Several clusters ofsequences obtained are deeply rooted and show low similarity (60%~78%) to the known rbcL in existing databases.The degree of diversity of rbcL genes is directly related to environmental variables, including temperature, salinity,pH, dissolved oxygen, etc. These results indicate that rbcL gene can be used as an effective indicator for geneticdiversity and population variability of bacterioplankton with the ability of carbon dioxide fixation in the sea.

EROD activities of liver in Mugil so-iuy exposed to benzo(a)pyrene,pyrene and their mixture

The effects on hepatic EROD (7-ethoxyresorufin O-deethylase) in Mugil so-iuy exposedto benzo(a)pyrene (BaP), pyrene and their mixtures of equal concentration were investigated, at concentrations of 0.1, 1.0, 5.0, 10.0, 50.0μg/dm3, in experimental condition. Time-effects and dose-response of the biochemical indexs were observed. The results showed that the hepatic EROD activities were induced by the exposure of BaP, pyrene and their mixtures at high concentration. Dose-response connections were that the hepatic EROD activities were elevated with increasing concentration of the pollutants. The combined effect of BaP and pyrene at 1:1 concentration ratio on hepatic EROD activity was antagonism.

Response of antioxidase in viscera of Pagrosuma Major larvae to water soluble fraction of hydrocarbons in No.0 diesel oil

Pagrosomus major larvae were exposed to the water soluble fraction of hydrocarbon in No.0 diesel oil (corresponding to No.2 fuel oil) at concentrations of 0, 0 17, 1.22 and 8 82 mg/L for up to 15 days. Larvae were sampled on days 9 and l5 of the experiment. Supernatants of viscera tissue extractions were assayed for biochemical response in terms of oxidative stress superoxide dismutase(SOD), activity of selenium dependant glutathione peroxidase(Se GPx) and catalase(Ca), and the concentration of reduced glutathione(GSH). On day 9 of exposure, statistically significant dose related increases in Se GPx and SOD activity, and GSH concentration were observed in all cases except for Se GPx activity under the highest dosage of hydrocarbon. However, on day l5 of exposure, a similar dose related response was only observed for Se GPx activity. GSH concentration decreased and SOD activity showed no statistical difference as compared to controls. However, a significant decrease in compared to day 9 Se GPx activity and GSH concentration, in contrast to increase SOD activity at day 15 as indicates an accelerated accumulation of H 2O 2 and potential oxidative damage under long term exposure of larvae to hydrocarbons. No statistical changes were observed in Ca activity throughout the experiment, possibly owing to the high efficiency of Se GPx. A recovery experiment was performed on indicating that the response of antioxidants measured tending to return to their control levels. These results prove the function of the antioxidant defense system of the larvae to the water soluble fraction of hydrocarbons in No.0 diesel oil.

An exploration of the uncertainty relation satisfied by BP network learning ability and generalization ability

This paper analyses the intrinsic relationship between the BP network learning ability and generalization ability and other influencing factors when the overfit occurs, and introduces the multiple correlation coefficient to describe the complexity of samples; it follows the calculation uncertainty principle and the minimum principle of neural network structural design, provides an analogy of the general uncertainty relation in the information transfer process, and ascertains the uncertainty relation between the training relative error of the training sample set, which reflects the network learning ability, and the test relative error of the test sample set, which represents the network generalization ability; through the simulation of BP network overfit numerical modeling test with different types of functions, it is ascertained that the overfit parameter q in the relation generally has a span of 7×10-3 to 7×10-2; the uncertainty relation then helps to obtain the formula for calculating the number of hidden nodes of a network with good generalization ability under the condition that multiple correlation coefficient is used to describe sample complexity and the given approximation error requirement is satisfied; the rationality of this formula is verified; this paper also points out that applying the BP network to the training process of the given sample set is the best method for stopping training that improves the generalization ability.