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The effect of substrate grain size on burrowing ability and distribution characteristics of Perinereis aibuhitensis
Tao Sun, Chun’e Liu, Xingzuo Li, Dongzhengyang An, Hairui Yu, Zheng Ma, Feng Liu
doi: 10.1007/s13131-019-1348-z
Perinereis aibuhitensis (Grube, 1878) lives in marine sediments of estuary or shoal areas, where substrate has some crucial environmental factors affecting its burrowing and distribution. In order to provide basic data for the habitat selection and suitability evaluations of the artificial aquaculture of P. aibuhitensis, this paper conducted a quantified analysis of its burrowing ability and explored its behavioral preferences in different substrates, including mud (<75 μm), fine sand (125–250 μm), medium sand (250–500 μm), coarse sand (500–2 000 μm), gravel (2 000–4 000 μm) and ceramsite (4 000–8 000 μm). The research results revealed that substrate grain size significantly affected the burrowing time, burrowing rate, burrowing depth and distribution rate (P<0.01). Moreover, P. aibuhitensis demonstrated preferential selections relating to substrate grain sizes, had higher burrowing ability in ceramsite, mud and fine sand compared with other substrates. The strongest burrowing ability and the highest distribution rate were observed in ceramsite. The study indicated that P. aibuhitensis was sensitive to substrate grain size, which also had an impact on its burrowing process and population distribution. In the natural sea, substrates mainly composed of mud and fine sand are fit for aquaculture and stock enhancement. Based on behavioral preferences and ecological rehabilitation function of P. aibuhitensis, this paper proposes a symbiotic system of marine animals and halophytes, and constructs an ecosystem model of " Marine fish-Halophytes-Perinereis aibuhitensis” with P. aibuhitensis as the link.
key words: Perinereis aibuhitensis, substrate, grain size, burrowing ability, distribution characteristics
Comparison of TMI and AMSR-E sea surface temperatures with Argo near-surface temperatures over the global oceans
Xingrong CHEN, Zenghong LIU, Chaohui SUN, Haiyan WANG
doi: 10.1007/s13131-017-1040-0
Satellite-derived sea surface temperatures (SSTs) from the tropical rainfall measuring mission (TRMM) microwave imager (TMI) and the advanced microwave scanning radiometer for the earth observing system (AMSR-E) were compared with non-pumped near-surface temperatures (NSTs) obtained from Argo profiling floats over the global oceans. Factors that might cause temperature differences were examined, including wind speed, columnar water vapor, liquid cloud water, and geographic location. The results show that both TMI and AMSR-E SSTs are highly correlated with the Argo NSTs; however, at low wind speeds, they are on average warmer than the Argo NSTs. The TMI performs slightly better than the AMSR-E at low wind speeds, whereas the TMI SST retrievals might be poorly calibrated at high wind speeds. The temperature differences indicate a warm bias of the TMI/AMSR-E when columnar water vapor is low, which can indicate that neither TMI nor AMSR-E SSTs are well calibrated at high latitudes. The SST in the Kuroshio Extension region has higher variability than in the Kuroshio region. The variability of the temperature difference between the satellite-retrieved SSTs and the Argo NSTs is lower in the Kuroshio Extension during spring. At low wind speeds, neither TMI nor AMSR-E SSTs are well calibrated, although the TMI performs better than the AMSR-E.
key words: Argo, near-surface temperature, tropical rainfall measuring mission (TRMM) microwave imager, advanced microwave scanning radiometer for the earth observing system, sea surface temperature
Newly discovered hydrothermal fields along the ultraslow-spreading Southwest Indian Ridge around 63°E
Jie CHEN, Chunhui TAO, Jin LIANG, Shili LIAO, Chuanwan DONG, Huaiming LI, Wei LI, Yuan WANG, Xihe YUE, Yonghua HE
doi: 10.1007/s13131-018-1333-y
The ultraslow-spreading Southwest Indian Ridge (SWIR) to the east of the Melville fracture zone is characterized by very low melt supply and intensive tectonic activity. Due to its weak thermal budget and extremely slow spreading rate, the easternmost SWIR was considered to be devoid of hydrothermal activity until the discovery of the inactive Mt. Jourdanne hydrothermal field (27°51′S, 63°56′E) in 1998. During the COMRA DY115-20 cruise in 2009, two additional hydrothermal fields (i.e., the Tiancheng (27°51′S, 63°55′E) and Tianzuo (27°57′S, 63°32′E) fields) were discovered. Further detailed investigations of these two hydrothermal sites were conducted by Chinese manned submersible Jiaolong in 2014–2015. The Tiancheng filed can be characterized as a low-temperature (up to 13.2°C) diffuse flow hydrothermal field, and is hosted by fractured basalts with hydrothermal fauna widespread on the seafloor. The Tianzuo hydrothermal field is an inactive sulfide field, which is hosted by ultramafic rocks and controlled by detachment fault. The discovery of the three hydrothermal fields around Segment #11 which receives more melt than the regional average, provided evidence for local enhanced magmatism providing heat source to drive hydrothermal circulation. We further imply that hydrothermal activity and sulfide deposits may be rather promising along the easternmost SWIR.
key words: Southwest Indian Ridge, ultraslow-spreading, hydrothermal field, local enhanced magmatism, heat source
Feeding strategies of Euphausia superba in the eastern South Shetland Islands in austral summer
Mengtan Liu, Zhencheng Tao, Ye Zhang, Guang Yang, Song Sun, Chaolun Li, Fengfeng Le
doi: 10.1007/s13131-019-1392-8
Euphausia superba is a key species in the Southern Ocean that serves as a link between primary production and higher trophic levels. To investigate the feeding strategies of E. superba from the eastern South Shetland Islands, fatty acid biomarkers, stable isotope signatures, and an incubation experiment were conducted. The results of the incubation experiment proved that adult E. superba mainly fed on 2 to 20 μm particles, demonstrating the importance of nanoplankton in their diet. Moreover, significant positive relationships between δ15N and body size demonstrated that size-related dietary shifts were present in E. superba. Evidence from principal component analysis and the C16:1ω7/C18:4ω3 ratio showed that juveniles preferentially fed on dinoflagellates and that adults were more likely to feed on diatoms. Fatty acid profiles in adult E. superba roughly mirrored the different trophic conditions and feeding strategies between stations. Adult E. superba at Stas D2-07, D5-07, DA-01 and DA-02 exhibited elevated levels of C16:1ω7, C18:4ω3, C18:1ω9 and C18:1ω9/C18:1ω7, indicating higher levels of feeding on both phytoplankton and higher trophic diets. In contrast, adult E. superba at Stas D1-03 and D1-04 were characterized by high levels of polyunsaturated fatty acids/saturated fatty acids ratios and low levels of C16:1ω7, C18:1ω7, C18:4ω3, C18:1ω9 and total fatty acids. We inferred that adult krill at Stas D1-03 and D1-04 still suffered from difficult dietary conditions after overwintering. The different dietary conditions between stations suggest a highly plastic feeding strategy of E. superba in the eastern South Shetland Islands.
key words: Euphausia superba, South Shetland Islands, fatty acids, stable isotopes
Relationships between intensity of the Kuroshio current in the East China Sea and the East Asian winter monsoon
Ming YIN, Xin LI, Ziniu XIAO, Chongyin LI
doi: 10.1007/s13131-018-1240-2
Based on satellite altimeter and reanalysis data, this paper studies the relationships between the intensity of the Kuroshio current in the East China Sea (ECS) and the East Asian winter monsoon (EAWM). The mechanisms of their possible interaction are also discussed. Results indicate that adjacent transects show consistent variations, and on an interannual timescale, when the EAWM is anomalously strong (weak), the downstream Kuroshio in the ECS is suppressed (enhanced) in the following year from February to April. This phenomenon can be attributed to both the dynamic effect (i.e., Ekman transport) and the thermal effect of the EAWM. When the EAWM strengthens (weakens), the midstream and downstream Kuroshio in the ECS are also suppressed (intensified) during the following year from October to December. The mechanisms vary for these effects. The EAWM exerts its influence on the Kuroshio's intensity in the following year through the tropospheric biennial oscillation (TBO), and oceanic forcing is dominant during this time. The air-sea interaction is modulated by the relative strength of the EAWM and the Kuroshio in the ECS. The non-equivalence of spatial scales between the monsoon and the Kuroshio determines that their interactions are aided by processes with a smaller spatial scale-i.e., local wind stress and heating at the sea surface.
key words: East Asian winter monsoon, Kuroshio intensity, East China Sea, interaction, correlation analysis, composite analysis
Paleoenvironmental implications of the calcium isotope characteristics in the MD81349 from the Nintyeast Ridge in the Indian Ocean
Feng WANG, Nianqiao FANG, Chaoyong HU, Sarah GOLDSMITH, Yonghang XU, Xuan DING, Aijun WANG, Ping CHEN, Rui BAO
doi: 10.1007/s13131-018-1264-7
A δ44Ca curve from shells of the planktonic foraminifera Globigerinoides sacculifer in calcareous biogenic oozes has been extracted from the Nintyeast Ridge in the Indian Ocean since 300 ka. By combining terrigenous inputs (e.g., grain size, magnetic susceptibility, and turbidite frequency) with the oceanic productivity (e.g., biogenic content and Neogloboquadrina dutertrei content), it is found that the curve’s variations are closely related to the historical evolution of the oceanic calcium cycle. The δ44Ca value is in lower tendency and has small oscillation during Marine Isotope Stage (MIS) 6, when the supply of terrigenous detrital is highest. In contrast, during MIS 3, 5 and 7, the δ44Ca values are in higher tendency, and their fluctuations are consistent with the variations of the productivity proxies. These results suggest that the calcium isotopes are mainly influenced by the input of the Himalayan erosion products to the northern Indian Ocean. In addition, the developmental stages of calcareous planktons may have a secondary impact on the fluctuations of the calcium isotope ratio of sea water.
key words: Nintyeast Ridge, calcium isotope, paleoceanography, Indian Ocean
Aerial observations of sea ice and melt ponds near the North Pole during CHINARE2010
Lanyu LI, Changqing KE, Hongjie XIE, Ruibo LEI, Anqi TAO
doi: 10.1007/s13131-017-0994-2
An aerial photography has been used to provide validation data on sea ice near the North Pole where most polar orbiting satellites cannot cover. This kind of data can also be used as a supplement for missing data and for reducing the uncertainty of data interpolation. The aerial photos are analyzed near the North Pole collected during the Chinese national arctic research expedition in the summer of 2010 (CHINARE2010). The result shows that the average fraction of open water increases from the ice camp at approximately 87°N to the North Pole, resulting in the decrease in the sea ice. The average sea ice concentration is only 62.0% for the two flights (16 and 19 August 2010). The average albedo (0.42) estimated from the area ratios among snow-covered ice, melt pond and water is slightly lower than the 0.49 of HOTRAX 2005. The data on 19 August 2010 shows that the albedo decreases from the ice camp at approximately 87°N to the North Pole, primarily due to the decrease in the fraction of snow-covered ice and the increase in fractions of melt-pond and open-water. The ice concentration from the aerial photos and AMSR-E (The Advanced Microwave Scanning Radiometer-Earth Observing System) images at 87.0°–87.5°N exhibits similar spatial patterns, although the AMSR-E concentration is approximately 18.0% (on average) higher than aerial photos. This can be attributed to the 6.25 km resolution of AMSR-E, which cannot separate melt ponds/submerged ice from ice and cannot detect the small leads between floes. Thus, the aerial photos would play an important role in providing high-resolution independent estimates of the ice concentration and the fraction of melt pond cover to validate and/or supplement space-borne remote sensing products near the North Pole.
key words: sea ice, melt pond, albedo, concentration, aerial observation, North Pole
Smectite formation in metalliferous sediments near the East Pacific Rise at 13°N
Kunbo RONG, Zhigang ZENG, Xuebo YIN, Shuai CHEN, Xiaoyuan WANG, Haiyan QI, Yao MA
doi: 10.1007/s13131-018-1265-6
A 43 cm long E271 sediment core collected near the East Pacific Rise (EPR) at 13°N were studied to investigate the origin of smectite for understanding better the geochemical behavior of hydrothermal material after deposition. E271 sediments are typical metalliferous sediments. After removal of organic matter, carbonate, biogenic opal, and Fe-Mn oxide by a series of chemical procedures, clay minerals (<2 μm) were investigated by X-ray diffraction, chemical analysis and Si isotope analysis. Due to the influence of seafloor hydrothermal activity and close to continent, the sources of clay minerals are complex. Illite, chlorite and kaolinite are suggested to be transported from either North or Central America by rivers or winds, but smectite is authigenic. It is enriched in iron, and its contents are highest in clay minerals. Data show that smectite is most likely formed by the reaction of hydrothermal Fe-oxyhydroxide with silica and seawater in metalliferous sediments. The Si that participates in this reaction may be derived from siliceous microfossils (diatoms or radiolarians), hydrothermal fluids, or detrital mineral phases. And theirδ30Si values are higher than those of authigenic smectites, which implies that a Si isotope fractionation occurs during the formation because of the selective absorption of light Si isotopes onto Fe-oxyhydroxides. Sm/Fe mass ratios (a proxy for overall REE/Fe ratio) in E271 clay minerals are lower than those in metalliferous sediments, as well as distal hydrothermal plume particles and terrigenous clay minerals. This result suggests that some REE are lost during the smectite formation, perhaps because their large ionic radii of REE scavenged by Fe-oxyhydroxides preclude substitution in either tetrahedral or octahedral lattice sites of this mineral structure, which decreases the value of metalliferous sediments as a potential resource for REE.
key words: metalliferous sediments, smectite formation, REE, silicon isotope
The origin of the suspended particulate matter in the seagrass meadow of tropical waters, an evidence of the stable isotope signatures
doi: 10.1007/s13131-019-1380-z
Suspended particulate matter (SPM) has been known as an important variable in the organic matter flow of coastal ecosystem. Half of burial carbon in seagrass meadows is contributed by allochthonous sources that compose the SPM such as phytoplankton, seagrass detritus, marine snow aggregates and terrestrially derived particles. Each composition of the SPM contributes different roles and is important to be identified, for instance, the exact contribution of seagrass detritus will be useful for determination of carbon export through the detritus form in seagrass meadows. Here, the SPM of seagrass meadows is studied in Bintan Island and the Selayar Archipelago. The aim of this research is to determine the source origin of the SPM using a stable isotope signature. In order to fulfill this aim, the objectives are defined as: (1) to specify the stable isotope signature (δ13C and δ15N) of the SPM, and (2) to determine the proportional distribution of the SPM’s prospectus sources. The result shows that the possibility of the source origin of the SPM includes a seagrass fraction (Enhalus acoroidesand Thalassia hemprichii), terrestrial C4 plant, macroalgae, and terrestrial C3 plant. The SPM lies between the marine- and terrigenous-end members. However, it seems that the SPM is more to be terrigenous-end and allochthonous. According to a Bayesian mixing model, the terrestrial C4 has the highest contribution of the SPM at all sites except Barugaia and Pasi Island in Selayar (i.e., the highest contribution of the SPM is from the detritus of E. acoroides). The second contribution has been contributed by either seagrass detritus (E. acoroides or Th. hemprichii) or terrestrial C3 plant. The finding of this study indicates that there is a strong influence of the terrigenous sources in the SPM of the seagrass meadows.
key words: suspended particulate matter, stable isotope, source origin, seagrass ecosystems
N2 fixation rate and diazotroph community structure in the western tropical North Pacific Ocean (WTNP)
Run Zhang, Dongsheng Zhang, Min Chen, Zhibing Jiang, Chunsheng Wang, Minfang Zheng, Yusheng Qiu, Jie Huang
In the present study, we report N2 fixation rate (15N isotope tracer assay) and the diazotroph community structure (using the molecular method) in the western tropical North Pacific Ocean (WTNP) (13–20°N, 120–160°E). Our independent evidence on the basis of both in situ N2 fixation activity and diazotroph community structure showed the dominance of unicellular N2 fixation over majority of the WTNP surface waters during the sampling periods. Moreover, a shift in the diazotrophic composition from unicellular cyanobacteria group B-dominated to Trichodesmium spp.-dominated toward the western boundary current (Kuroshio) was also observed in 2013. We hypothesize that nutrient availability may have played a major role in regulating the biogeography of N2 fixation. In surface waters, volumetric N2 fixation rate (calculated by nitrogen) ranged between 0.6 and 2.6 nmol/(L·d) and averaged (1.2±0.5) nmol/(L·d), with <0 μm size fraction contributed predominantly (88%±6%) to the total rate between 135°E and 160°E. Depth-integrated N2 fixation rate over the upper 200 m ranged between 150 μmol/(m2·d) and 480 μmol/(m2·d) (average (225±105) μmol/(m2·d). N2 fixation can account for 6.2%±3.7% of the depth-integrated primary production, suggesting that N2 fixation is a significant N source sustaining new and export production in the WTNP. The role of N2 fixation in biogeochemical cycling in this climate change-vulnerable region calls for further investigations.
key words: western tropical North Pacific Ocean (WTNP), N2 fixation, 15N isotope tracer assay, unicellular diazotroph

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