Wintertime meso-scale horizontal distribution of large tintinnids in the southern Yellow Sea

Spatial distribution of some large tintinnid species (nominally > 76 mu m) is investigated on samples vertically towed in the southern Yellow Sea in winters of 2001 to 2004. Nine tintinnid species are recorded: Codonellopsis morchella, Stenosemella pacifica, S. steini, Tintinnopsis schotti, T. radix, T. karajacensis, Eutintinnus tenuis, Parafavella sp., Leprotintinnus neriticus, of which C. morchella and T. radix dominated in the warm tongue-shaped zone of the Yellow Sea Warm Current (YSWC), and S. pacifica is the next in abundance. Our study shows that these tintinnids occur repeatedly in certain special distribution patterns.

Fluorescence Characterization of Dissolved Organic Matter in the East China Sea after Diatom Red Tide Dispersion

Fluorescence excitation-emission spectroscopy (EEMS) was employed to analyze the 3-dimensional fluorescence of dissolved organic matter in the East China Sea after diatom red tide dispersion. The relationships between fluorescence peak intensity, and salinity and chlorophyll-a were discussed. The centers of protein-like fluorescence peaks dispersed at Ex(max)/Em(max) = 270-280/290-315 nm (Peak B), 220-230/290-305 nm (Peak D), 230-240/335-350 nm(Peak S)and 280/320 nm(Peak T). Two humic-like peaks appeared at 255-270/435-480 nm (Peak A) and 330-350/420-480 nm(Peak C). High tyrosine-like intensity was observed in diatom red tide dispersion area, and tryptophan-like fluorescence was also found which was lower. High FIB/FIS showed that diatom red tide produced much tyrosine-like matter during dispersion. Peaks S, A and C had positive correlation with one another, and their distributions were similar, which decreased with distance increasing away from the shore. Good negative correlations between peaks S, A and C and salinity suggested that Jiangsu-Zhejiang coastal water was the same source of then-L Correlations between fluorescence peak intensity and chlorophyll-a were not remarkable enough to clear the relationship between fluorescence and living algal matter. It was supposed that the living algal matter contributed little to the fluorescence intensity of algal dispersion seawater.

Morphological and genetic study of Prorocentrum donghaiense Lu from the East China Sea, and comparison with some related Prorocentrum species

In this paper, the detailed morphology of Prorocentrum donghaiense Lu from both field samples and cultures was examined, and a taxonomic comparison was made between P donghaiense and some related Prorocentrum spp. using morphological and molecular data and other published information. There were distinct differences among these species in morphological characteristics that historically have been presented as conservative features. The discrepancies extended beyond that of individual variations within the same species due to environmental factors. Therefore, these morphological features may not be conservative but, rather, polymorphic depending on environmental conditions. Based on this analysis, we suggest that the high-biomass bloom-forming species in the East China Sea, previously reported as Prorocentrum dentatum Stein, is P donghaiense Lu. The species reported from the East China Sea and Japanese and Korean waters appear to be the same species. Molecular data also suggest that P. dentatum (CCMP1517) and P. donghaiense are genetically identical. Therefore, the geographic distribution of P. donghaiense may be much wider than expected. (C) 2004 Elsevier B.V. All rights reserved.

Geochemical characteristics of nitrogen in the southern Yellow Sea surface sediments

Roles and distributions of various forms of nitrogen in biogeochemical cycling in the southern Yellow Sea surface sediments were investigated. The southern Yellow Sea could be divided into three regions (I, II and III) according to the proportion of fine-grained sediment in > 65%, 35-65% and < 35%, respectively. The ratios of different forms of nitrogen contents between each two of the three regions indicated that the nitrogen contents increased with the proportion of fine-grained sediment increasing. The quanta of exchangeable forms of nitrogen were similar in the three regions, while their releasing time increased from regions I to III, indicating that the cycle of nitrogen in fine-grained sediments was shorter than that in coarse-grained sediments. Nitrogen burial fluxes were also similar in these regions, while the burial efficiency increased from regions I to III. The highest burial efficiency was 30.21% in region III, indicating that more than 70% of nitrogen in the southern Yellow Sea surface sediments could be released to take part in biogeochemical recycling. When all the four forms of exchangeable nitrogen (nitrogen in ion exchangeable form (IEF-N), nitrogen in weak acid extractable form (WAEF-N), nitrogen in strong alkali extractable form (SAEF-N) and nitrogen in strong oxidant extractable form (SOEF-N)) were released to take part in recycling, their potential contributions were 80% (SOEF-N), 11% (IEF-N), 6% (SAEF-N), 3% (WAEF-N) respectively, which showed that SOEF-N was the predominant one, and its contribution to biogeochemical cycling was the highest. (c) 2004 Elsevier B.V. All rights reserved.

Organochlorine micropollutants in the Jiulong River Estuary and Western Xiamen Sea, China

Organochlorine contaminants including 12 polychlorinated biphenyl (PCB) congeners and 18 insecticides were determined in water, pore water and sediments of the Jiulong River Estuary and Western Xiamen Sea, China. The results showed that the levels of the total PCBs ranged from non-detectable to 1500 ngl(-1) in water, from 209 to 3870 ngl(-1) in pore water, and from 2.78 to 14.8 ng g(-1) dry weight in sediments. Total organochlorine insecticide concentrations were from below the limit of detection to 2480 ngl(-1) in water, from 267 to 33400 ngl(-1) in pore water, and from 4.22 to 46.3 ng g(-1) dry weight in sediments. Concentrations of PCBs and insecticides in pore water were significantly higher than those in surface water, due to the high affinity of these hydrophobic compounds for sediment phase. The PCB congeners with the highest concentrations were CB153, CB180 and CB194, which together accounted for 68-87% of total PCBs in water, pore water and sediment. Among the hexachlorocyclohexane (HCH) compounds, beta-HCH was found to be a major isomer. Analysis of 1,1,1-trichloro-2,2-bis-chlorophenyl-ethane (DDT) and its metabolites showed that 1, 1-dichloro-2[o-chlorophenyl]-2[p-chlorophenyl]-ethylene (DDE) was dominant in the group. In comparison to a 1998 study in the Western Xiamen Sea, levels of organochlorines were enhanced due probably to recent inputs and changes in sediments. (c) 2004 Elsevier Ltd. All rights reserved.

Carbon isotopic studies of individual lipids in organisms from the Nansha sea area, China

Carbon isotopes of individual lipids in typical organisms from the Nansha sea area were measured by the GC-IRMS analytical technique. delta(13)C values of saturated fatty acids in different organisms examined are from -25.6parts per thousand to -29.7parts per thousand with the average values ranging from -26.4parts per thousand to -28.2parts per thousand and the variance range of 11.8parts per thousand, between different organisms is also observed. Unsaturated fatty acids have heavy carbon isotopic compositions and the mean differences of 2.9%.9-6.8parts per thousand compared to the same carbon number saturated fatty acids. delta(13)C values of n-alkanes range from -27.5%o to -29.7parts per thousand and their mean values, ranging from -28.6parts per thousand, to -28.9parts per thousand, are very close in different organisms. The mean difference in delta(13)C between the saturated fatty acids and n-alkanes is only 1.5parts per thousand, indicating that they have similar biosynthetic pathways. The carbon isotopic variations between the different carbon-number lipids are mostly within +/-2.0parts per thousand, reflecting that they experienced a biosynthetic process of the carbon chain elongation. At the same time, the carbon isotopic genetic relationships between the biological and sedimentary lipids are established by comparative studies of carbon isotopic compositions of individual lipids in organisms and sediments from the Nansha sea area, which provides scientific basis for carbon isotopic applied research of individual lipids.

Feeding and respiration rates of a planktonic copepod (Calanus sinicus) oversummering in Yellow Sea Cold Bottom Waters

The distribution, feeding and oxygen consumption of Calanus sinicus were studied in August 2001 on a transect across Yellow Sea Cold Bottom Waters (YSCBW) and two additional transects nearby. The distribution of C. sinicus adults and copepodites stage CV appeared to be well correlated with water temperature. They tended to concentrate in the YSCBW (>10,000 ind. m(-2)) to avoid high surface temperature. Gut pigment contents varied from 0.44 to 2.53 ng chlorophyll a equivalents (chl a equiv.) ind.(-1) for adults, and from 0.24 to 2.24 ng chl a equiv. ind.(-1) for CV copepodites. We found no relationship between gut pigment contents and the ambient chl a concentrations. Although the gut evacuation rate constants are consistent with those measured for other copepods, their low gut pigment contents meant an estimated daily herbivorous ingestion of <3% of body carbon in the YSCBW and <10% outside the YSCBW. However, based on estimates of clearance rates, C. sinicus feeds actively whether in the YSCBW or not, so the low ingestion rates probably reflect shortage of food. Oxygen consumption rates of C. sinicus ranged from 0.21 to 0.84 mul O-2 ind.(-1) h(-1), with high rates often associated with high temperature. From the oxygen consumption rates, daily loss of body carbon was estimated to be 4.0-13.7%, which exceeds our estimates of their carbon ingestion rates. C. sinicus was probably not in diapause, either within or outside the YSCBW, but this cold-water layer provides C. sinicus with a refuge to live through the hot, low-food summer.

Characteristics of nitrogen forms in the southern Huanghai Sea surface sediments

The distributions of different forms of nitrogen in the surface sediments of the southern Huanghai Sea are different and affected by various factors. The contents of IEF-N, SOEF-N and TN gradually decrease eastward, and those of SAEF-N northward, while those of WAEF-N westward. Around the seaport of the old Huanghe (Yellow) River, the contents of both SOEF-N and TN are the highest. Among all the factors, the content of fine sediment is the predominant factor to affect the distributions of different forms of nitrogen. The contents of IEF-N, SOEF-N, and TN have visibly positive correlation with the content of fine sediments, and the correlative coefficient is 0.68, 0.58 and 0.71 respectively, showing that the contents of the three forms of nitrogen increase with those of fine sediments. The content of WAEF-N is related to that of fine sediments to a certain extent, with a correlative coefficient of 0.35; while the content of SAEF-N is not related to that of fine sediments, showing that the content of SAEF-N is not controlled by fine grain-size fractions of sediments. In addition, the distributions of different forms of nitrogen are also interacted one another, and the contents of IEF-N and SOEF-N are obviously affected by TN, while those of inorganic nitrogen (WAEF-N, SAEF-N and IEF-N) are not affected by SOEF-N and TN obviously, although they are interacted each other.

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 (34.5degrees similar to 37.0degreesN, 120.5degrees similar to124.0degreesE) during June 12 similar to 27, 2000. It was found that the abundance of marine flagellate ranged from 45 to 1278 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 organhisms, with a ratio of heterotrophic bacteria: cyanobacteria: flagellate: dinoflagellate: ciliate being 10(5) 10(3):10(2):10(1):10(0).

Grazing impact of copepods on phytoplankton in the Bohai Sea

During spring (April/May 1999) and autumn (September/October 1998) cruises in the Bohai Sea, China, copepods were the dominant components of mesozooplankton, the most abundant species being Calanus sinicus, Centropages mcmurrichi, Paracalanus parvus, Acartia bifilosa and Oithona similis. Pigment ingestion rates by three size classes of copepods (200-500, 500-1000 and > 1000 mum) were measured. In the south of the investigation area, gut pigment content (GPC), individual pigment-specific ingestion rates and grazing impacts on phytoplankton were lower in spring than in autumn. In the central area, GPC and individual pigment-specific ingestion rates were higher in spring than in autumn. The grazing impact on phytoplankton by the copepod assemblages was lower in spring than in autumn, however, because of the relatively smaller biomass in spring. In the western area where the Bohai Sea joins the Yellow Sea, GPC, individual pigment-specific ingestion rates and grazing impacts on phytoplankton were higher in spring than in autumn. Among the three size groups, the small-sized animals (200-500 mum) contributed more than 50% (range 38-98%) of the total copepod grazing during both cruises. The grazing impact on phytoplankton by copepods was equivalent to 11.9% (range 3.0-37.1%) of the chlorophyll-a standing stock and 53.3% (range 21.4-91.4%) of the primary production during the spring cruise. Grazing impact was equivalent to 6.3% (range 2.0-11.6%) of the chlorophyll-a standing stock and >100% (range 25.7-141.6%) of the primary production during the autumn cruise. The copepod community apparently consumed only a modest proportion of the standing stock of phytoplankton during spring and autumn blooms. They did, however, sometimes graze a significant proportion of daily primary production and hence were presumably able to limit the rate of further accumulation of phytoplankton, or even to prevent it. (C) 2003 Elsevier Ltd. All rights reserved.

Abundance of Calanus sinicus across the tidal front in the Yellow Sea, China

The abundance of Calanus sinicus eggs, nauplii, copepodites and adults and chlorophyll a (Chl-a) concentration were studied across tidal fronts in October 2000, and May and June 2001 in the Yellow Sea, China. The aim of the study was to evaluate the role of tidal fronts in the ecology of C. sinicus. The hydrographic tidal fronts were identified by the horizontal temperature gradient in the bottom layer and the temperature profiles across the fronts. The survey results showed that the concentration of Chl-a was high in the vicinity of the fronts, particularly in spring and early summer. The abundance of C. sinicus eggs and nauplii was usually higher in the tidal fronts than in the adjacent areas. In May and June 2001, the abundance of copepodites and adults of C. sinicus peaked in the tidal front. In June 2001 and October 2000, many copepodites and adults were found in stratified region.

Numerical study on the velocity structure around tidal fronts in the Yellow Sea

The velocity components across tidal fronts are examined using the Blumberg and Mellor 3-D nonlinear numerical coastal circulation model incorporated with the Mellor and Yamada level 2.5 turbulent closure model based on the reasonable model output of the M-2 tide and density residual currents. In the numerical experiments, upwelling motion appears around all the fronts with different velocity structures, accounting for surface cold water around the fronts. The experiments also suggest that the location and formation of fronts are closely related to topography and tidal mixing, as is the velocity structure around the front.

The Yellow Sea cold bottom water - an oversummering site for Calanus sinicus (Copepoda, Crustacea)

The vertical distribution and stage-specific abundance of Calanus sinicus were investigated on three key transects in the southern Yellow Sea and the northern East China Sea in August 1999. The results showed that in summer C. sinicus shrank its distribution area to the central cold (less than or equal to10degreesC) bottom water in the Yellow Sea, i.e. the Yellow Sea Cold Bottom Water, remaining in high abundance (345.7 ind m(-3)). In the northern East China Sea on a transect from the mouth of the Yangtze River to the Okinawa trench, only a few individuals appeared in the inner side and none had been found either in the upper layer or in the deep layer of the outer shelf area. The population of C. sinicus in YSCBW consisted of mainly adults (46.83%) and C5 (37.41%). C1-C4 only accounted for 15.76%. The low proportion of the earlier copepodite stages and the high female:male ratio (11.39) indicated that the reproduction of C. sinicus in YSCBW was at a very low level due to the low temperature and low food concentration. It is concluded that the dramatic decrease of C. sinicus population in the shelf area of China seas in summer is caused by the shrinkage of its distribution area and the YSCBW served as an oversummering site.

Triterpane and sterane biomarkers in the YA13-1 condensates from Qiongdongnan Basin, South China Sea

Triterpanes and steranes in condensates from the YA13-1 gas field, Qiongdongnan Basin, were monitored. The YA13-1 condensates have unusual biomarker distributions dominated by terpanes and steranes derived from higher plants. Anomalously abundant 1 got-oleanane and remarkably abundant bicadinanes are present in the YA13-1 condensates, whereas the 17alpha-hopane contents are extremely low. Taraxastane and significantly abundant 17alpha-diahopanes occur in the condensates. In addition, a number of unknown C-29 and C-30 pentacyclic triterpanes including previously unreported compounds were detected in the condensates, some of which are significantly abundant. The unknown compounds may be terrestrial biomarkers. C-29 homologues are relatively predominant among the regular and rearranged steranes. The diasterane concentrations are markedly higher than those of regular steranes. The maturity of the YA13-1 condensates is relatively high, at the peak to late oil generation stage (corresponding to 0.85-1.10% Ro), based on sterane and terpane and including bicadinane maturity parameters (i.e. T/(T-1 + R) and 2T/R bicadinane ratios). The above maturity assessment result is different from that based on diamondoid maturity parameters (%Ro = 1.60-1.70) [Org. Geochem. 25 (1996) 179], which can be explained by a contribution of hydrocarbons from two sources at different depths. The YA13-1 condensates were probably generated from the Yacheng and Lingshui coal-bearing source rocks buried both in the Qiongdongnan Basin (3400-5000 m) and in the Yinggehai Basin (>5000 m). The possible contribution of lower maturity hydrocarbons from the Yacheng and Lingshui Formations (3400-4100 m) in the Qiongdongnan Basin to the YA13-1 gases and condensates should not be neglected. (C) 2003 Elsevier Science B.V. All rights reserved.

Digestive gut structure and activity of protease, amylase, and alkaline phosphatase in Calanus sinicus during summer in the Yellow Sea and the East China Sea

Calanus sinicus aggregate at the depth of 40-60 m (ambient temperature is 16 degreesC) in the waters of the continental shelf of the Yellow Sea during summer. in animals found in near shore regions, there are changes in digestive gut cells structure, digestive enzyme activity (protease, amylase), and tissue enzyme (alkaline phosphatase (ALP)), which may represent adaptations by this cold-water animal to a sharp seasonal increase in temperature of 6-23 degreesC. The activities of the digestive enzymes (protease and amylase) are very low in animals at stations near the estuary of Yangtse River, whereas they are relatively high in animals at stations in the central Yellow Sea, During summer, B-cells of the intestine and the villi intestinalis disappear in animals that do not feed at stations near the estuary of the Yangtse River. Respiration rates were undetectable or quite low during summer in C. sinicus from stations near the estuary of the Yangtse River, whereas they were relatively high at stations in the central Yellow Sea. Based upon the morphological characteristics of the digestive gut structure, enzyme levels, respiration rates, and the distribution of C. sinicus, we concluded that C. sinicus might be dormant during summer in the near shore areas of the East China Sea while remaining active in the central Yellow Sea. (C) 2002 Elsevier Science B.V. All rights reserved.