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EN
Marine picoplankton, including prokaryotic and eukaryotic picoplankton, drive many biogeochemical processes, such as carbon, nitrogen and sulfur cycles, making them crucial to the marine ecosystem. Despite the fact that picoplankton is prevalent, its diversity and spatial distribution from the Straits of Malacca (SM) to the South China Sea (SCS) remain poorly investigated. This work explores the phylogenetic diversity and community structure of picoplankton in relation to environmental factors from the SM to the SCS. To this end, the Illumina MiSeq sequencing technique was applied to 16S and 18S rRNA genes. The results showed significant differences in the dynamics of picoplankton between the open sea and the strait region. Proteobacteria and Cyanobacteria constituted a larger part of the prokaryotic group. Within Cyanobacteria, the abundance of Prochlorococcus in the open sea was significantly higher than that of Synechococcus, while the opposite trend was observed in the strait. Dinoflagellata, Cnidaria, Retaria, Tunicata, and Arthropoda dominated among the eukaryotic taxa. High-throughput sequencing data indicated that salinity, temperature and NO2-N were the key factors determining the prokaryotic community structure, while temperature and dissolved oxygen determined the eukaryotic community structure in the studied region. The network analysis demonstrated that the cooperation and competition were also important factors affecting the picoplankton community.
2
Content available remote “Noise” in climatologically driven ocean models with different grid resolution
EN
The internally generated variability in the climate system, which is unrelated to any external factors, can be conceptualized as “noise”. This noise is a constitutive element of high-dimensional nonlinear models of such systems. In a three-layer nested simulation, which is forced by climatological (periodic) atmospheric forcing and includes an (almost) global model, a West-Pacific model, and South China Sea (SCS) model, we demonstrate that such “noise” builds also ocean models. They generate variability by themselves without an external forcing. The “noise” generation intensifies with higher resolution, which favors macroturbulence.
EN
The shipping noise near channels and ports is an important contribution to the ambient noise level, and the depth of these sites is often less than 100 m. However less attention has been paid to the measurement in shallow water environments (Brooker, Humphrey, 2016). This paper presents extensive measurements made on the URN (underwater radiated noise) of a small fishing boat in the South China Sea with 87 m depth. The URN data showed that the noise below 30 Hz was dominated by the background noise. The transmission loss (TL) was modelled with FEM (finite element method) and ray tracing according to the realistic environmental parameters in situ. The discrepancy between the modelled results and the results using simple law demonstrates both sea surface and bottom have significant effect on TL for the shallow water, especially at low frequencies. Inspired by the modelling methodology in AQUO (Achieve QUieter Oceans) project (Audoly et al., 2015), a predicted model applied to a typical fishing boat was built, which showed that the URN at frequencies below and above 100 Hz was dominated by non-cavitation propeller noise and mechanical noise, respectively. The agreement between predicted results and measured results also demonstrates that this modelling methodology is effective to some extent.
EN
Using the yellowfin tuna (Thunnusalbacares,YFT)longline fishing catch data in the open South China Sea (SCS) provided by WCPFC, the optimum interpolation sea surface temperature (OISST) from CPC/NOAA and multi-satellites altimetric monthly averaged product sea surface height (SSH) released by CNES, eight alternative options based on Bayes classifier were made in this paper according to different strategies on the choice of environment factors and the levels of fishing zones to classify the YFT fishing ground in the open SCS. The classification results were compared with the actual ones for validation and analyzed to know how different plans impact on classification results and precision. The results of validation showed that the precision of the eight options were 71.4%, 75%, 70.8%, 74.4%, 66.7%, 68.5%, 57.7% and 63.7% in sequence, the first to sixth among them above 65% would meet the practical application needs basically. The alternatives which use SST and SSH simultaneously as the environmental factors have higher precision than which only use single SST environmental factor, and the consideration of adding SSH can improve the model precision to a certain extent. The options which use CPUE’s mean ± standard deviation as threshold have higher precision than which use CPUE’s 33.3%-quantile and 66.7%-quantile as the threshold
EN
We collected flying fish (Exocoetus volitans) from the South China Sea to determine whether fish scale isotope values correlate with those from muscle, and discuss relevant eco-environmental implications. A significant positive correlation was determined between fish scales and muscle δ13C and δ15N, rendering a fish scale an alternative to muscle tissue for stable isotope analysis. However, muscle and scale isotopic offsets should be fully considered when using δ13C and δ15N to analyze the actual trophic level of fish and their food source. The average offsets of δ13C and δ15N between muscles and scales are -2.1 ± 0.5‰ and 2.3 ± 0.6‰, respectively, though these values vary slightly with fish mass. Weak correlations were found between δ13C and δ15N, both in the flying fish muscle and scales, suggesting that other factors are influencing δ13C and δ15N. Fish δ15N also correlates with the size of individuals, while δ13C reflects the marine habitat. Based on our data, it appears that more eco-environmental processes can be revealed from modern or ancient flying fish scales.
EN
We suggest to transfer the empirical downscaling methodology, which was developed mostly for atmospheric dynamics and impacts, to regional ocean problems. The major problem for doing so is the availability of decades-long and homogeneous and spatially detailed data sets. We have examined the performance of the STORM multidecadal simulation, which was run on a 0.1° grid and forced with 1950–2010 NCEP re-analyses, in the South China Sea and found the data suitable. For demonstration we build with this STORM-data downscaling model for the regional throughflow. The STORM data is compared with AVISO satellite observations and the ocean re-analysis dataset C-GLORS. We find the seasonal patterns and the inter-annual variability of sea surface height anomaly in both the C-GLORS data and the STORM simulation consistent with the AVISO-satellite data. Also the strong westward intensification and the seasonal patterns of South China Sea circulation steered by the monsoon have been presented well. As an important indicator of vertical movement, the sea surface temperature distribution maps are also very close, especially for the narrow upwelling region in summer. We conclude that the output of the STORM simulation is realistically capturing both the large-scale as well as the small-scale dynamical features in the South China Sea.
EN
Based on the survey records on netz-phytoplankton (>76 μm) collected in the South China Sea (SCS) during the cruise from the 21st August to the 18th October, 2012, the species composition, biodiversity and its spatial distribution were studied. The identified 326 phytoplankton species belonged to 75 genera and 4 phyla. Thalassionema nitzschioides was the most dominant species accounting for 33.24% of the total cell abundance, followed by Bacteriastrum furcatum − 8.69%. Whereas the phytoplankton cell abundance (cells l-1) was the highest in the Zhubi Reef (1106.45 ± 2475.38), the southern SCS (396.84 ± 969.87), the western SCS (90.82 ± 144.66) and the northern SCS (66.48 ± 70.89) in order. The distribution of phytoplankton appears to be affected by the Mekong river discharge and particles derived in Sumatra and Kalimantan from biomass burning, nutrient concentrations, the South China Sea Warm Current (SCSWC). The evaluation of biodiversity indices indicated the high level of species richness, evenness and biodiversity in the survey area.
EN
Fatty acid analysis was used to understand feeding ecology and habitat use of coral reef fishes in six families: Lutjanidae (Lutjanus lutjanus), Labridae (Thalassoma lunare), Nemipteridae (Scolopsis affinis, S. monogramma), Pomacentridae (Abudefduf bengalensis, A. sexfasciatus, A. viagiensis), Scaridae (Scarus quoyi, S. quoyi, S. rivulatus, S. ghobban) and Serrandae (Epinephelus fuscoguttatus, Cephalopholis cyanostigma, C. boenak) collected on the Bidong Island of the Malaysian South China Sea. The percentage of saturated fatty acids (ΣSAFA) ranged from 58.0% to 62.5%, with the highest values in fatty acids, the second highest percentage values were those of monounsaturated fatty acids (ΣMUFA) and they ranged from 25.7% to 38.9%, and the percentage of polyunsaturated fatty acids (ΣPUFA) had the lowest values, i.e. from 2.7% to 13.2%. ΣMUFA and ΣPUFA were significantly different between families, while ΣSAFA did not differ. These results indicate diverse feeding ecology and habitat use during the fish life history in relation to physiological condition, sexual development, and recent feeding events in the coral reef habitats in the Malaysian South China Sea.
EN
Amplitude versus offset (AVO) analysis is a conventional seismic exploration technique in geophysical and lithological interpretation and has been widely used in onshore and offshore exploration. Its use in marine gas hydrate research, however, is still in initial stages. In this study, AVO analysis is applied to seismic profiles at drilling sites where hydrate samples have been recovered. The AVO responses of free gas, bottom simulating reflector (BSRs), and gas hydrates are discussed, and the AVO attributes in relation to gas hydrates are summarized. The results show that changes in intercept, gradient, fluid factor and Poisson’s ratio clearly reflect: (i) location of free gas and the BSR, and (ii) spatial relations between blank zone, BSR, gas hydrate, and free gas.
EN
Physicochemical and benthos data were collected from 12 marine monitoring stations in Daya Bay, during 2001-2004. 12 stations in Daya Bay could be grouped into three clusters: cluster I consisted of stations in the southern part of Daya Bay (stations S1, S2 and S6); cluster II consisted of stations in the cage culture areas (stations S3, S4, S5 and S8); cluster III consisted of stations in the southwest, the middle and the northeast of the Bay (stations S7, S9, S10, S11 and S12). Calculation with bivariate correlations between benthos and major physicochemical factors showed that the density of benthos in all stations correlated positively with temperature, DO, pH, NH4-N, SiO3-Si, SiO3-Si /PO4-P and chlorophyll a and was negatively correlated with salinity, Secchi, COD, NO3-N, NO2-N, TIN, PO4-P, TIN/PO4-P and BOD5. Factor analysis showed that there were high positive loading salinity, Secchi and NH4-N of three clusters. Results revealed that temperature, DO, pH, SiO3-Si and SiO3-Si/PO4-P and chlorophyll a could also play an important role in determining the biomass of benthos in Daya Bay, especially near the Nuclear Power Plants, in the southern part and in the cage culture areas.
EN
In order to demonstrate that silicate can be used as an indicator to study upwelling in the northern South China Sea, hierarchical cluster analysis (CA) and principle component analysis (PCA) were applied to analyse the metrics of the data consisting of 14 physical-chemical-biological parameters at 32 stations. CA categorized the 32 stations into two groups (low and high nutrient groups). PCA was applied to identify five Principal Components (PCs) explaining 78.65% of the total variance of the original data. PCA found important factors that can describe nutrient sources in estuarine, upwelling, and non-upwelling areas. PC4, representing the upwelling source, is strongly correlated to silicate (SiO3-Si). The spatial distribution of silicate from the surface to 200 m depth clearly showed the upwelling regions, which is also supported by satellite observations of sea surface temperature.
PL
Artykuł omawia problematykę sporów terytorialnych na akwenie Morza Południowochińskiego, w które uwikłane są państwa regionu, w tym kraje ASEAN (Association of South East Asian Nations — Stowarzyszenie Narodów Azji Południowo-Wschodniej) oraz Chiny. Spory te pośrednio oddziałują na Japonię, Koreę Południową i Stany Zjednoczone. Morze Południowochińskie to ważny akwen, przez który biegną liczne morskie szlaki komunikacyjne służące przepływowi surowców strategicznych i towarów w relacjach Azja Wschodnia — reszta świata. Tym samym akwen ma znaczenie globalne w kontekście bezpieczeństwa i rozwoju gospodarczego. Spory związane z Wyspami Spratly i Paracelskimi to istotny element obecnej sytuacji regionu, który eskalować może w konflikt regionalny, a poprzez zaangażowanie potęg światowych wpłynąć na sytuację na świecie. Artykuł wskazuje źródła sporów, zaangażowanie i stanowiska państw na akwenie Morza Południowochińskiego oraz implikacje regionalne i globalne.
EN
The paper deals with issues related to disputes in the South China Sea region. The countries of the region , including the ASEAN countries (Association of South East Asian Nations) and China, are involved in the disputes. They affect indirectly Japan, South Korea and the USA. The South China Sea is an important water area with numerous sea communication lines used to carry strategic resources and goods in trade relations between East Asia and the rest of the world. Thus the water-area has a global significance in the context of security and economic development. Disputes over Spratly and Paracels Islands constitute an important element of the situation in the region which may escalate into a regional conflict, and through involvement of world powers may affect the situation in the world. The paper shows the sources of the disputes, commitment and approach of the countries in the South China Sea as well as some regional and global implications.
EN
The South China Sea is among Southeast Asia’s potential hot spots, and any turmoil in the area can cause serious security implications for the region. Such a disorder would also have global consequences. Territorial disputes involve many nations: Brunei. China, Malaysia, the Philippines. Taiwan, and Vietnam. Moreover, the situation influences such countries as Japan, South Korea and the United States of America both militarily and economically. The South China Sea is important because of geostrategic location, natural resources and rich fisheries. The article describes main territorial disputes including: Spratly Islands, Paracel Islands and Senkaku Islands, which do not seem to be solved in any near-term period. At present all the claimants are expressing strong preference to solve the disputes peacefully, but in the past navy force was used before to enforce or expand national rights. So, it cannot be excluded that they could be employed again. The potential for conflict is still probable and could escalate very quickly affecting overall global security.
14
Content available remote Using chemometrics to identify water quality in Daya Bay, China
EN
In this paper, chemometric approaches based on cluster analysis, classical and robust principal component analysis were employed to identify water quality in Daya Bay (DYB), China. The results show that these approaches divided water quality in DYB into two groups: stations S3, S8, S10 and S11 belong to cluster A, which lie in Dapeng Cove, Aotou Harbor and the north-eastern part of DYB, where water quality is related mainly to anthropogenic activities. The other stations belong to cluster B, which lie in the southern, central and eastern parts of DYB, where the quality is related mainly to water exchange with the South China Sea. Cluster analysis yields good results as a first exploratory method for evaluating spatial difference, but it fails to demonstrate the relationship between variables and environmental quality on the one hand and the untreated data on the other. However, with the aid of suitable chemometric approaches, the relationship between samples or variables can be investigated. Classical and robust principal component analysis can provide a visual aid for identifying the water environment in DYB, and then extracting specific information about relationships between variables and spatial variation trends in water quality.
EN
Experimental data on the ambient noise generated by large-amplitude internal waves in the ocean are considered. The data are obtained by us during oceanic expeditions in the Indian Ocean and South China Sea. In both cases the generation of noise was caused by solitary internal waves with 50-m amplitudes. The internal waves were accompanied by strong orbital currents (up to 1.5 m/s) which created intense convergence with choppy surface waves at the sea surface. Simultaneous observations of internal waves and parameters of the ambient noise were carried out from a drifting vessel during calm weather. In both cases, the increase in the level of the ambient noise coincided with the passages of internal waves. The analysis of experimental data and the data of numerically modeling are presented.
EN
In the maritime search and rescue responsibility region of Vietnam (on the South China Sea), there are two monsoon seasons in opposite direction and contrary character in two halves of the year: North East monsoon season (cold season) and South West monsoon season (warm season). During monsoon seasons, wind is rather stable and strong, for determining search area, the application of one-dimensional models gives smaller search area as compared with the search area determined in accordance with recommendations in lAMSAR Manual of IMO/ICAO.
PL
W wietnamskim obszarze odpowiedzialności na Morzu Południowo Chińskim są dwie monsunowe pory: północno-wschodnia pora monsunowa (zima) i południowo-zachodnia pora monsunowa (lato). Podczas monsunów w obszarze tym wieją silne wiatry o stałym kierunku. Do wyznaczania obszaru poszukiwania zastosowano modele jednowymiarowe, które umożliwiają zmniejszenie obszaru poszukiwania w stosunku do obszarów wyznaczonych zgodnie z zaleceniami w podręczniku lAMSAR IMO/ICAO.
EN
This study analyzed seasonal physicochemical and phytoplankton data collected at 12 marine monitoring stations in Daya Bay from 1999 to 2002. Cluster analysis based on water quality and phytoplankton parameters measured at the 12 stations could be grouped into three clusters: cluster I - stations S1, S2, S7 and S11 in the southern part and the north-eastern part of Daya Bay; cluster II - stations S5, S6, S9, S10 and S12 in the central and north-eastern parts of Daya Bay; cluster III - stations S3, S4 and S8 in the cage culture areas in the south-western part of Daya Bay and in the north-western part of the Bay near Aotou harbor. Bivariate correlations between phytoplankton density and the major physical and nutrient factors were calculated for all stations. Factor analysis shows that there were high positive loadings of pH, TIN and the ratio of TIN to PO4-P in the three clusters, which indicates that all the stations in the three clusters were primarily grouped according to their respective nutrient conditions.
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