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21.
We measured the concentrations and distribution of major polyamines(spermine, putrescine and spermidine) in seawater during successive spring algal blooms in an area of frequent harmful blooms in the East China Sea. Spermine, putrescine, and spermidine concentrations were analyzed by high performance liquid chromatography and ranged from 1–64, 7–81, and 0–19 nmol/L. Spermine was present at the highest concentrations, followed by putrescine and spermidine. In late April, when a diatom bloom dominated by Skeletonema costatum dispersed, polyamine concentrations increased, presumably as a result of diatom decomposition. In early May, when a dinoflagellate bloom dominated by Prorocentrum donghaiense occurred, the polyamine concentration decreased from the level seen in late April. The abundant polyamines that decomposed and were released during the diatom bloom in late April may have promoted the growth of P. donghaiense, resulting in its dominance. 相似文献
22.
The primary goal of this study was to assess the effect of varying densities on serum reproductive parameters of immature rainbow trout Oncorhynchus mykiss. Experimental trout were maintained in intensive, pen-reared farms for 300 days in fresh water reservoirs. Initial densities were 4.6, 6.6, and 8.6 kg/m3 (40, 60, 80 ind./m3), indicated as SD1, SD2, SD3, and final densities were 31.1, 40.6, 49.3 kg/m3, respectively. A summary of the ovarian stages were observed by histological examination. Serum E2 (estradiol), T (testosterone) were evaluated by radioimmunoassay and FSH (follicle-stimulating-hormone), LH (luteinizing-hormone), vitellogenin, 17α,20β-P (17α,20βdihydroxy4-pregnen-3-one) were measured by enzyme-linked immunosorbent assay. Our findings demonstrated that ovarian development were retarded (from stage III to stage IV) at highest rearing density (SD3) after 180 days of intensive culture (over 40.6 kg/m3). In addition, we observed an inverse relationship between serum reproductive parameters and rearing density. Furthermore, compared to serum reproductive parameters of SD1, E2, T, FSH, vitellogenin, 17α,20β-P, GSI and LH of two higher density groups decreased firstly and significantly at 60 (over 15.9 kg/m 3 ), 180 (over 31.7 kg/m 3 ), 180 (over 40.6 kg/m3), 240 (over 36 kg/m3), 240 (over 36 kg/m3), 240 (over 45 kg/m3) and 300 (over 49.3 kg/m3) days, respectively. Comparing serum reproductive parameters within the same ovarian development stage of rainbow trout from varying densities revealed that higher population density also led to significantly lower overall serum reproductive parameters. Overall, this study presents the reproductive, endocrinological parameters of juvenile female rainbow trout at high rearing densities and indicates the need for rainbow trout (114.44±5.21 g, 19.69±0.31 cm) that are initially stocked at 6.6 or 8.6 kg/m3 should be classified and subdivided into lower density after 180 days of farming (not over 31.7 kg/m3). 相似文献
23.
HermannKreutzmann 《山地科学学报》2004,1(3):193-210
Starting with a discussion of development concepts which were applied in practice and which followed the developmentalist paradigm the expansion of traffic infrastructure in colonial and post-colonial periods is presented for the High Asian mountain rim. Selective railways and roads are the major feature of this development, which aimed first on serving the convenience of hill station visitors and followed strategic considerations later on. This bias between regional planning and implementation remains a characteristic feature. At the same time traffic infrastructure without asphalt roads is important for the mountain areas, thus breaking up the strong correlation between development and asphalt roads. 相似文献
24.
A severe Cochlodinium geminatum red tide (>300 km2) was observed in the Zhujiang (Pearl) River estuary, South China Sea in autumn 2009. We evaluated the environmental conditions and phytoplankton community structure during the outbreak. The red tide water mass had significantly higher dissolved inorganic phosphate (DIP), ammonia, and temperature, but significantly lower nitrite, nitrate, dissolved inorganic nitrogen (DIN), and DIN/DIP relative to the non-red-tide zones. The phytoplankton assemblage was dominated by dinoflagellates and diatoms during the red tide. C. geminatum was the most abundant species, with a peak density of 4.13×107 cell/L, accounting for >65% of the total phytoplankton density. The DIN/DIP ratio was the most important predictor of species, accounting for 12.45% of the total variation in the phytoplankton community. Heavy phosphorus loading, low precipitation, and severe saline intrusion were likely responsible for the bloom of C. geminatum. 相似文献
25.
Acrochaete leptochaete (Huber) Nielsen (Chaetophoraceae, Chlorophyta) was isolated from the macroalgae Chaetomorpha collected from intertidal pools in Rongcheng, Shandong, China. 18S rDNA combined with ITS regions were used to ascertain the morphological identification of the isolated material. Based on the unialgal culture, asexual reproduction and growth characteristics of A. leptochaete were investigated over wide ranges of temperature and irradiance. Results revealed that asexual reproduction of A. leptochaete could be realized by biflagellate zoospores. The zoospores germinated directly to give self- replicating generations. Zoospore germination was bipolar. A temperature range from 13-21°C and a lower irradiance of 36 μmol/(m2·s) were most favorable for the growth of A. leptochaete. Thallus organization, an important taxonomic criterion for the genus Acrochaete, was affected markedly by temperature and irradiance. Our results extend the knowledge about the species’ general biology and its morphological plasticity. For classification and identification of a simple microphytic algae like A. leptochaete, which are traditionally placed in the class Chaetophoraceae, we propose that molecular tools associated with culture observations are applied. 相似文献
26.
Pigment characterization for the 2011 bloom in Qinhuangdao implicated "brown tide" events in China 总被引:6,自引:0,他引:6
A large-scale bloom occurred from May to June in 2011 in sea area near Qinhuangdao of the Bohai Sea, leading to huge damage of the scallop culture industry. Similar blooms have been observed in this region for three years. The causative species of the bloom, which dominated the phytoplankton community with the maximum cell density around 109 cell/L, could not be identified with morphological features due to the small cell size (~2 mm). A pigment analytical method was then adopted to analyze the pigment profile of the phytoplankton samples collected from the blooming sea area. It was found that pico-sized (<2 mm), nano-sized (2-20 mm), and bulk phytoplankton samples had similar pigment profile, representing the pigment signature of the bloom-causative species. The major pigments detected included 19-butanoyloxyfucoxanthin (But-fuco), fucoxanthin (Fuco), diadinoxanthin (Diad) and chlorophyll a (Chl a), and high content of But-fuco was the most significant characteristics of the phytoplankton samples. Based on the pigment composition and content, the bloom-causative species could be tentatively identified as pelagophyte, "type 8" group of haptophyte, or silicoflagellate. Some unique features of the bloom, such as the extremely high cell density, small-sized and But-fuco containing cells, occurring in early summer, and the feeding-cessation effects on scallops, suggest it be a "brown tide" event similar to those reported in the east coast of the United States of America. The recurrent "brown tide" events and their dramatic impacts on the shellfish mariculture industry in Qinhuangdao need close attention in the coming years. 相似文献
27.
Little is known about the genome of Pacific white shrimp (Litopenaeus vannamei). To address this, we conducted BAC (bacterial artificial chromosome) end sequencing of L. vannamei. We selected and sequenced 7 812 BAC clones from the BAC library LvHE from the two ends of the inserts by Sanger sequencing. After trimming and quality filtering, 11 279 BAC end sequences (BESs) including 4 609 paired- ends BESs were obtained. The total length of the BESs was 4 340 753 bp, representing 0.18% of the L. vannamei haploid genome. The lengths of the BESs ranged from 100 bp to 660 bp with an average length of 385 bp. Analysis of the BESs indicated that the L. vannamei genome is AT-rich and that the primary repeats patterns were simple sequence repeats (SSRs) and low complexity sequences. Dinucleotide and hexanucleotide repeats were the most common SSR types in the BESs. The most abundant transposable element was gypsy, which may contribute to the generation of the large genome size of L. vannamei. We successfully annotated 4 519 BESs by BLAST searching, including genes involved in immunity and sex determination. Our results provide an important resource for functional gene studies, map construction and integration, and complete genome assembly for this species. 相似文献
28.
Pathogenicity of vibrios in fish: An overview 总被引:1,自引:0,他引:1
Norman Y.S.Woo 《中国海洋大学学报(英文版)》2003,2(2):117-128
Bacteria of the genus Vibrio are ubiquitously distributed in the marine environment. Due to the rapid expansion of intensive mariculture and the consequent deterioration of culture conditions, more and more Vibrio spp. have been recognized as pathogenic agents in outbreaks of vibriosis, a serious epizootic disease affecting most wild and farmed fish species worldwide, which has become the most important limiting factor for the development of intensive mariculture industry. Attempts have been made to understand the pathogenicity of vibrios in host fish with the ultimate aim of elucidating the best means for disease control. After an extensive literature survey of the recent advances in the field of fish vibriosis, the pathological changes, virulence factors and associated potential pathogenic mechanisms, transmission routes and related environmental factors involved in outbreak of vibriosis, as well as the controlling strategies are reviewed in the present paper. 相似文献
29.
The advantages of using unmanned underwater vehicles in coastal ocean studies are emphasized. Two types of representative vehicles, remotely operated vehicle (ROV) and autonomous underwater vehicle (AUV) from University of South Florida, are discussed. Two individual modular sensor packages designed and tested for these platforms and field measurement results are also presented. The bottom classification and albedo package, BCAP, provides fast and accurate estimates of bottom albedos, along with other parameters such as in-water remote sensing reflectance. The real-time ocean bottom optical topographer, ROBOT, reveals high-resolution 3-dimentional bottom topography for target identification. Field data and results from recent Coastal Benthic Optical Properties field campaign, 1999 and 2000, are presented. Advantages and limitations of these vehicles and applications of modular sensor packages are compared and discussed. 相似文献
30.
This study aims to assess conservation practices in Izta-Popo National Park(Central Mexico) by evaluating the mechanisms of sediment transfer. We applied a methodology based on fallout ~(137)Cs and optically stimulated luminescence(OSL) analysis. This was tested in the upper catchment of Amalacaxco Gorge, selected for being one of the sectors of the park in which man-made actions have been implemented in last decades to favor forest growth in the alpine grassland and to reduce the effect of water runoff. We quantified the ~(137)Cs activity using gamma and beta spectrometry of fine sediment grains extracted from the surface of parcels of 0.4 m2 in areas of natural forest, natural alpine grassland, alpine grassland with conservation practices, ravines and trails. In general, ~(137)Cs values increases as local slope decreases as it was expected. The natural forest is the most stable area in terms of soil erosion and sediment accumulation and, mean ~(137)Cs activity was taken as reference to assess cumulative zones, with higher ~(137)Cs values and erosive, with lower. We found that trails are accumulative surfaces but in other areas, erosion predominates. Man-made ditches, trenches and afforestation in the alpine grassland have higher ~(137)Cs values than thenatural grassland, which indicates that conservation practices are limiting the sediment transfer from hillslopes to channels, however, soil retention is less than in the natural grassland. Additionally, we evaluated the luminescence(OSL) values obtained from samples extracted from the sediment transported in ravines that are cutting into different sectors of the study area to assess the grade of resetting of fluvial materials. These luminescence results indicated that the sediment transported in ravines that are cutting into the natural forest and alpine grassland is bleached more efficiently than the sediment transported in the alpine grassland with conservation practices. Results of fallout ~(137)Cs and luminescence strongly suggest that man-made actions in this part of the Izta-Popo National Park are dramatically modifying the natural mechanisms of sediment transfer and favoring soil erosion. We conclude that made ditches, trenches and afforestation are not an effective conservation practice in Amalacaxco Gorge because they are promoting soil erosion instead of reducing it. 相似文献