This study was to investigate bacterial and archaeal community structure of pan-Arctic Ocean sediments by pyrosequencing. In total, investigation of three marine sediments revealed 15 002 bacterial and 4 362 archaeal operational taxonomic units (OTUs) at the 97% similarity level. Analysis of community structure indicated that these three samples had high bacterial and archaeal diversity. The most relatively abundant bacterial group in Samples CC1 and R05 was Proteobacteria, while Firmicutes was dominant in Sample BL03. Thaumarchaeota was the most relatively abundant archaeal phylum in Samples CC1 and R05, and the relative abundance of Thaumarchaeota was almost as high as that of Euryarchaeota in Sample BL03. These two phyla accounted for nearly 100% of the archaeal OTUs. δ-Proteobacteria and γ-Proteobacteria were the two most relatively abundant classes at Proteobacterial class level, and their relative abundance was more than 60% in Samples CC1 and R05. There were also differences in the top 10 relatively abundant bacterial and archaeal OTUs among the three samples at the 97% similarity, and only 12 core bacterial OTUs were detected. Overall, this study indicated that there were distinct microbial communities and many unique OTUs in these three samples.
Coral reefs are an sensitive-to-environment complex marine ecosystem.The ecosystem of corals is rich in biodiversity.Remote sensing offers a powerful tool for categorizing coral reefs and is the most cost-effective approach for the large-scale reef survey.The Dongsha Atoll, more than 300 km2 with an average depth of 10 m, is located at the northern continental margin of the South China Sea.It has been abused by destructive fishing during recent decades.Three satellite imageries (Quickbird2, ETM+ and SPOT5) are used to evaluate the capabilities of SPOT5 imagery to provide data that are useful for categorizing the current distribution of coral reefs therein.During the data processing, unsupervised classification functions are adopted for ETM+ and SPOT5 data, while the supervised classification method is used for Quickbird2.The classes are (or not) merged into coral reef, and then will be operated by vectorization, simplification, and topological analysis.There are 1 331 coral reefs larger than 100 m2 with a detection limit of 3×3 pixels at the multi-band data of Quickbird2, which is taken as the comparison baseline.The results extracted from SPOT5 and ETM images are less in number and area than those from the Quickbird2 image, whereas the results from SPOT5 data are better than those of ETM data at the silty lagoon due to its higher resolution.SPOT5 XS band 2 fails to distinguish the deep substrate inside the atoll compared with ETM data because of its poor penetration capability.Only SPOT XS band 1 cannot be used to differentiate coral reef from sand bottom.Merging the SPOT5 multi-bands data with the spatial resolution of SPOT5 pan-data and referring to ETM imagery are expected to provide an optimal satellite-based approach for mapping of coral reefs.
The result of an analysis of mollusca remains collected from the Chukchi Sea,Beaufort Sea and Bering Sea in the First Chinese National Arctic Research Expedition,from July to September,1999 is presented.Seventeen species of mollusca have been identified,which belong to two classes:Bivalvia and Gastropoda.The compositions of the mollusca are very simple.According to the distribution pattern two groups may be distinguished among molluscan species.The Pan-Arctic and circumboreal group comprises Nuculana pernula,N.radiata,Nucula bellotii,Astarte montagui,Seripes groenlandicus,Macoma calcarea,M.moesta alaskana,Liocyma fluctuosa,Mya pseudoarenaria and Turritella polaris. Three species,Cyclocardia crebricos tata,Trichotrois coronata and Argobuccinum oregonense are components of the Pan-Arctic and Pacific boreal group.With regard to feeding habits,detritus feeders dominate.There are 7 species of detritus feeders,i.e.,Nuculana pernula,N.radiata,Nucula bellotii,Macoma calcarea,M.moesta alaskana,Macoma sp.and Trichotropis coronata.Detritus feeders are dominant with regard to the numbers of species as well as to the frequency of occurrence.Macoma calcarea is the most abundant species.
Satellite remote sensing of inland water body requires a high spatial resolution and a multiband narrow spectral resolution, which makes the fusion between panchromatic (PAN) and multi-spectral (MS) images particularly important. Taking the Daquekou section of the Qiantang River as an observation target, four conventional fusion methods widely accepted in satellite image processing, including pan sharpening (PS), principal component analysis (PCA), Gram-Schmidt (GS), and wavelet fusion (WF), are utilized to fuse MS and PAN images of GF-1. The results of subjective and objective evaluation methods application indicate that GS performs the best, followed by the PCA, the WF and the PS in the order of descending. The existence of a large area of the water body is a dominant factor impacting the fusion performance. Meanwhile, the ability of retaining spatial and spectral informations is an important factor affecting the fusion performance of different fusion methods. The fundamental difference of reflectivity information acquisition between water and land is the reason for the failure of conventional fusion methods for land observation such as the PS to be used in the presence of the large water body. It is suggested that the adoption of the conventional fusion methods in the observing water body as the main target should be taken with caution. The performances of the fusion methods need re-assessment when the large-scale water body is present in the remote sensing image or when the research aims for the water body observation.
In this study, changes in Arctic sea ice thickness for each ice age category were examined based on satellite observations and modelled results. Interannual changes obtained from Ice, Cloud, and Land Elevation Satellite (ICESat)-based results show a thickness reduction over perennial sea ice (ice that survives at least one melt season with an age of no less than 2 year) up to approximately 0.5-1.0 m and 0.6-0.8 m (depending on ice age) during the investigated winter and autumn ICESat periods, respectively. Pan-Arctic Ice Ocean Modeling and Assimilation System (PIOMAS)-based results provide a view of a continued thickness reduction over the past four decades. Compared to 1980s, there is a clear thickness drop of roughly 0.50 m in 2010s for perennial ice. This overall decrease in sea ice thickness can be in part attributed to the amplified warming climate in north latitudes. Besides, we figure out that strongly anomalous southerly summer surface winds may play an important role in prompting the thickness decline in perennial ice zone through transporting heat deposited in open water (primarily via albedo feedback) in Eurasian sector deep into a broader sea ice regime in central Arctic Ocean. This heat source is responsible for enhanced ice bottom melting, leading to further reduction in ice thickness.
The ocean color satellite is mainly applied to measure the water constituents such as chlorophyll, suspended material and yellow substance. The leaving water radiance is very small part of the total radiance arrival at the sensor about 3%-15%,and depends on the properties of the orbit and sensor. Before the satellite is launched on the orbit, it needs to simulate the radiation imagery in order to evaluate the quality and availability of the satellite data. If the parameters of satellite orbit, the properties of sensor as well as the characteristics of the atmosphere and water have been known, the radiation scattered by air molecule and aerosol, reflected solar radiation, water leaving and total radiation arriving at the sensor can be simulated by the models of radiation transfer in the atmosphere, air/water and subsurface water. In this paper, the mechanism, models and procedures of the radiation simulation are first discussed and employed to simulate a series of imageries for the Chinese satellites FY-lA, FY-1B, and ROCSAT-1 (Taiwan, China), and American satellite Ses STAR. Their results show that the solar irradiance arrived at water surface and the sun glitter mainly affect the quality and availability of satellite data, which depend on the orbit properties. Finally, some suggestions are proposed to improve the quality and availability of a:ean color satellite data.
A series of NOAH AVHRR data over the East China Sea were collected from the ground station of the Institute of Oceanography,Hangzhou,China.Three methods,including a functional analytic method FAM),a maximum cross correlation(MCC)' method and a correlation relaxation(C-R) method,are applied to derive the sea surface current field from sequential satellite images in the area of the East China Sea.Several preprocessing steps,such as geometric correction,SST determination,image projection,image navigation and grey value normalization as well as land and cloud mask are performed.The results from the three methods reflect the general current system in this area reasonably.
Ocean environmental information is very important to supporting the fishermen in fishing and satellite remote sensing technology can provide it in large scale and in near real-time.Ocean fishery locations are always far away beyond the coverage of the satellite data received by a land-based satellite receiving station.A nice idea is to install the satellite ground station on a fishing boat.When the boat moves to a fishery location,the station can receive the satellite data to cover the fishery areas.One satellite remote sensing system was once installed in a fishing boat and served fishing in the North Pacific fishery areas when the boat stayed there.The system can provide some oceanic environmental charts such as sea surface temperature(SST) and relevant derived products which are in most popular use in fishery industry.The accuracy of SST is the most important and affects the performance of the operational system,which is found to be dissatisfactory.Many factors affect the accuracy of SST an it is difficult to increase the accuracy by SST retrieval algorithms and clouds detection technology.A new technology of temperature error control is developed to detect the abnotmity of satellite-measured SST.The performance of the technology is evaluated to change the temperature bias from -3.04 to 0.05℃ and the root mean square(RMS) from 5.71 to 1.75℃.It is suitable for employing in an operational satellite-measured SST system and improves the performance of the system in fishery applications.The system has been running for 3 a and proved to be very useful in fishing.It can help to locate the candidates of the fishery areas and monitor the typhoon which is very dangerous to the safety of fishing boats.
The space satellite programs,such as CZCS/Nimbus-7,VHRSR/FY-1,OCTS/ADEOS and SeaWiFS/SeaStar,have demonstrated and proven that remote sensing is a powerful tool for understanding the spatial and temporal ocean color distribution.In general,there are two main technical keys in the processing ocean color satellite data.They are the atmospheric correction and the inversion of water-leaving radiance into water constituents (such as chlorophyll,suspended material and yellow substance) quantitatively.The SeaWiFS (sea-viewing wide field-of-view sensor) atmospheric correction algorithm for China's coastal waters is discussed. First,the major advantages of SeaWiFS are introduced.Second,in view of the problems of the SeaDAS algorithm applying in China's coastal waters,the local atmospheric correction algorithms are discussed and developed.Finally,the advantages of the loc al algorithms are presented by the comparison of the results from two different algorithms.
China has launched her first ocean color satellite HY-1A on May 15,2002 since American ocean color satellite SeaSTAR was on the orbit in 1997.First,the properties and characteristics of HY-1A are briefly introduced; second,the quality and availability are evaluated by means of the complex signal noise ratio(CSNR) which is simulated theoretically; third,the received HY-1A data are compared with SeaSTAR data to understand the accuracy of radiance measurement by the HY-1A; finally,the remote sensing products of ocean color and temperature are mapped to study the application potentiality of HY-1A.The results show that the HY-1A has its latent capability for the application of marine environment detection,the management and protection of marine resources,and the national rights and interests.Meanwhile some suggestions are proposed to modify the next ocean satellite.