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Pei S.,Key Laboratory of Coastal Wetland Biogeosciences | Pei S.,Function Laboratory for Marine Geology | Laws E.A.,Louisiana State University | Zhang H.,Ocean University of China | And 2 more authors.
PLoS ONE | Year: 2017

A comprehensive study of water quality, phytoplankton biomass, and photosynthetic rates in Liaodong Bay, China, during June and July of 2013 revealed two large patches of high biomass and production with dimensions on the order of 10 km. Nutrient concentrations were above growth-rate-saturating concentrations throughout the bay, with the possible exception of phosphate at some stations. The presence of the patches therefore appeared to reflect the distribution of water temperature and variation of light penetration restricted by water turbidity. There was no patch of high phytoplankton biomass or production in a third, linear patch of water with characteristics suitable for rapid phytoplankton growth; the absence of a bloom in that patch likely reflected the fact that the width of the patch was less than the critical size required to overcome losses of phytoplankton to turbulent diffusion. The bottom waters of virtually all of the eastern half of the bay were below the depth of the mixed layer, and the lowest bottom water oxygen concentrations, 3-5 mg L-1 , were found in that part of the bay. The water column in much of the remainder of the bay was within the mixed layer, and oxygen concentrations in both surface and bottom waters exceeded 5 mg L-1 . © 2017 Pei et al. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.

Yang S.,Key Laboratory of Coastal Wetland Biogeosciences | Yang S.,Function Laboratory for Marine Geology | Yang S.,CAS Qingdao Institute of Oceanology | Li J.,CAS Qingdao Institute of Oceanology | And 9 more authors.
Quaternary International | Year: 2015

Eighty-six seafloor surface sediment samples from the western Bohai Sea were analyzed palynologically to understand the distribution pattern and transport paths of pollen and spores. The results reveal that the pollen assemblages are dominated by arboreal pollen, which accounts for an average of 52% and mainly includes Pinus, deciduous Quercus, Carpinus, Betula, Nitraria, Castanea, and Ulmus. The pollen percentages of herbaceous taxa reach an average of 25%, mostly represented by Chenopodiaceae, Artemisia, Gramineae, Liliaceae, Polygonum, Typha, and Cyperaceae. The fern spores are mostly Selaginella, Osmunda, Triletes, and Monoletes. The distribution characteristic of pollen and spores implies that the pollen assemblages correspond well with the watershed vegetation. Variation in the pollen assemblages in different parts of the marine area could reflect differences in local vegetation, especially the vegetation along the inflowing rivers. The spatial distribution of pollen assemblages further suggests that the discharge from the Yellow River and Luanhe River has a great contribution to the pollen inputs into the western Bohai Sea. Pollen concentrations are lower in the nearshore sea area (water depth<20. m) due to the combined effects of dynamic sedimentary environment and inflowing rivers. By contrast, pollen concentrations show higher values in the deeper waters of fine sediments near estuaries of Yellow River and Luanhe River and the sea area north of 39.5°N, reaching a maximum concentration of 7000grains/g. Based on the distribution characteristics of pollen and spores, the PCA analysis results of the distribution of the dominant pollen taxa confirm that pollen grains and spores deposition into the western Bohai Sea was primarily affected by the hydrodynamic condition or water sorted effect (including river flows and ocean currents), and secondarily through aeolian transportation. Non-arboreal pollen were mainly carried by fluvial input and deposited in the nearshore shallow water area. Arboreal pollen dominated by Pinus were mainly transported by winds and ocean currents, and fern spores mainly by river flows and ocean currents. The latter two types were mostly concentrated in relatively deeper water area. © 2015 Elsevier Ltd and INQUA.

Yang S.,Key Laboratory of Coastal Wetland Biogeosciences | Yang S.,Function Laboratory for Marine Geology | Yang S.,CAS Qingdao Institute of Oceanology | Li J.,Function Laboratory for Marine Geology | And 14 more authors.
Palaeogeography, Palaeoclimatology, Palaeoecology | Year: 2016

Assessing pollen distribution patterns in the sea is essential to understanding pollen provenance, upon which subsequent interpretation of Quaternary pollen data from marine sediments in the same study area should be soundly based. Here we present palynological data from seafloor sediments in Laizhou Bay and analogous samples from its inflowing rivers to elucidate the distribution patterns and provenance of modern palynomorphs. Our results demonstrate that the pollen assemblages of marine areas are dominated by arboreal pollen types, especially Pinus, and herbaceous pollen types are dominated by Chenopodiaceae and Artemisia. The higher pollen concentrations occur in the southwest area of Laizhou Bay, and the lower pollen concentrations are mainly distributed in the nearshore area of the Yellow River estuary. Such pollen distribution patterns are tightly correlated with the distribution features of grain size of the surface sediments. Specifically, the sediments with higher pollen concentrations are of very fine and fine silts, whereas those with lower pollen concentrations are of fine sands. The results of PCA analysis suggest that pollen grains in the nearshore areas are mainly transported by water flows, of which herbaceous pollen show relatively higher concentrations; while pollen grains in the offshore areas are largely carried by winds, especially those pollen types with sacs, such as Pinus. Dissimilarity analysis between marine and alluvial samples indicates that the pollen spectrum show close linkage with the regional vegetation in the surrounding watersheds. Pollen quantitative characteristics and pollen assemblage changes in different parts of the marine areas indicate various pollen provenance and changing landscape of terrestrial vegetation, particularly along the inflowing rivers. Our Assessments on pollen distribution patterns and provenance based on palynological investigation would strongly aid Quaternary palaeoecological and palaeoclimatological interpretation for our study area. © 2016 Elsevier B.V.

Oliva-Urcia B.,CSIC - Pyrenean Institute of Ecology | Oliva-Urcia B.,Autonomous University of Madrid | Munoz A.,University of Zaragoza | Larasoana J.C.,Instituto Geologico Y Minero Of Espana Igme | And 8 more authors.
Geologica Acta | Year: 2016

Environmental magnetic proxies were analyzed in a relatively monotonous, ~25.3m thick alluvial sedimentary sequence drilled in the Añavieja Basin (NE Spain). Results from the core AÑ2 suggest that the concentration dependent magnetic parameters mainly reflect variations in the content of detrital magnetite, sourced in the catchment rocks and soils of the basin, via changes in the dynamics of alluvial fans due to temperature changes in the northern hemisphere during the Late Pleistocene. The correspondence between the magnetic proxies and the temperature variations in the North Atlantic region (NGRIP curve) indicates that higher (lower) concentrations and finer (coarser) magnetite grains coincide with warm (cold) periods. We propose that during cold periods, a sparser vegetation cover favored the incoming of higher energy runoff bearing coarser sediments to the basin that are relatively impoverished in magnetite. In contrast, during warm periods, the wider distribution of the vegetation cover associated with the lower runoff energy lead to finer, magnetite-richer sediment input to the basin. Maghemite, presumably of pedogenic origin, appears to be present also in the studied alluvial sediments. Further studies are necessary to unravel its palaeoclimatic significance. © 2016, Universitat de Barcelona. All rights reserved.

Wang X.,Huazhong Agricultural University | Wang X.,University of Wyoming | Zhu M.,University of Wyoming | Koopal L.K.,Wageningen University | And 8 more authors.
Environmental Science: Nano | Year: 2016

The structure and magnetic properties of nano-sized (1.6 to 4.4 nm) ferrihydrite samples are systematically investigated through a combination of X-ray diffraction (XRD), X-ray pair distribution function (PDF), X-ray absorption spectroscopy (XAS) and magnetic analyses. The XRD, PDF and Fe K-edge XAS data of the ferrihydrite samples are all fitted well with the Michel ferrihydrite model, indicating similar local-, medium- and long-range ordered structures. PDF and XAS fitting results indicate that, with increasing crystallite size, the average coordination numbers of Fe-Fe and the unit cell parameter c increase, while Fe2 and Fe3 vacancies and the unit cell parameter a decrease. Mössbauer results indicate that the surface layer is relatively disordered, which might have been caused by the random distribution of Fe vacancies. These results support Hiemstra's surface-depletion model in terms of the location of disorder and the variations of Fe2 and Fe3 occupancies with size. Magnetic data indicate that the ferrihydrite samples show antiferromagnetism superimposed with a ferromagnetic-like moment at lower temperatures (100 K and 10 K), but ferrihydrite is paramagnetic at room temperature. In addition, both the magnetization and coercivity decrease with increasing ferrihydrite crystallite size due to strong surface effects in fine-grained ferrihydrites. Smaller ferrihydrite samples show less magnetic hyperfine splitting and a lower unblocking temperature (TB) than larger samples. The dependence of magnetic properties on grain size for nano-sized ferrihydrite provides a practical way to determine the crystallite size of ferrihydrite quantitatively in natural environments or artificial systems. © The Royal Society of Chemistry 2016.

Yang X.,Sun Yat Sen University | Liu Q.,CAS Institute of Geology and Geophysics | Liu Q.,Function Laboratory for Marine Geology | Yu K.,CAS South China Sea Institute of Oceanology | And 5 more authors.
Physics of the Earth and Planetary Interiors | Year: 2016

High-resolution paleomagnetic secular variation (PSV) records bear great information of dynamics processes of the Earth's geomagnetic field, and can be further used for inter-profile correlation and for dating sediments. However, effects of changes in the depositional environment on PSV records have not been fully determined. This study constructed Holocene PSV records for the gravity piston core (ZSQD34) obtained from the northern South China Sea. Rock magnetic and Transmission Electron Microscope (TEM) results indicate that single (SD) and PSD domain magnetites are the main carrier of the natural remanent magnetization. Comparable to the records derived from the freshwater lakes and the modeling results, we observed that direction curves from these two environments of contrasting salinity content are rather consistent. The direction curves are independent of the constructed salinity. However, the gradual increasing trend of relative intensity since about 5 kyr might be related to the decreasing sea surface salinity. Furthermore, on the centennial and millennial time scale, the relative intensity and salinity show some positive relation, suggesting a potential contribution of salinity to the paleomagnetic relative intensity recording processes. © 2016 Elsevier B.V.

Xu G.,CAS Qingdao Institute of Oceanology | Xu G.,Function Laboratory for Marine Geology | Xu G.,Key Laboratory of Coastal Wetland Biogeosciences | Liu J.,CAS Qingdao Institute of Oceanology | And 14 more authors.
Environmental Science and Pollution Research | Year: 2015

Spatial distribution, ecological risk, pollutant source, and transportation of trace metals in surface sediments, as well as the sediment properties, were analyzed in this study to assess the pollution status of trace metal in the Laizhou Bay, China. Results of provenance analyses indicate that surface sediments were primarily from weathering products carried by the surrounding short rivers and partially from loess matters carried by the Yellow River. Variations of trace metal concentrations were mostly controlled by the accumulation of weathering products, organic matters, and the hydrodynamics. Geoaccumulation index suggests that no Cr pollution occurred in the study area, and Cu, Pb, and Zn pollutions appeared only at a few stations. Comparatively, Cd and As pollutions were at noticeably weak to moderate level at many stations. The combination of six trace metals in this study had a 21 % probability of being toxic in our study area based on sediment quality guidelines. Enrichment factors (EFs) and statistical analyses indicate that Cu, Pb, and Zn were primarily derived from the natural process of weathering. By contrast, Cd, As, and Cr (especially Cd and As) were provided by the anthropogenic activities to a large extent. Due to the dilution of coarse-grained sediments, there was even no contamination at some of stations that were obviously influenced by humans. Based on the current study of transportation process of fine-grained sediments in combination with the spatial distribution of EFs, it is found that the migration of anthropogenic trace metals was mainly controlled by the tide in the Laizhou Bay. The study suggests that an effective strategies and remedial measures should be designed and undertaken to prevent further anthropogenic Cd and As pollutions in this area in the future. © 2015, Springer-Verlag Berlin Heidelberg.

Xia P.,State Oceanic Administration | Meng X.,State Oceanic Administration | Meng X.,Function Laboratory for Marine Geology | Li Z.,East China Normal University | And 3 more authors.
Organic Geochemistry | Year: 2015

Located at the interface of terrestrial and marine ecosystems, mangroves are particularly sensitive to environmental change. They provide a sedimentary sink for organic carbon, whereby cores can provide detailed records of mangrove species. We aimed to trace the history of mangrove development over the past 150years in Yingluo Bay, SW China. Sedimentation rates (avg. 0.32 and 0.37cm/year) were calculated on the basis of ln(210Pbex) vs. mass depth, and offset the rate of relative sea level rise (0.22-0.24cm/year), leading to a seaward expansion of new mangrove habitats. Chemical tracers (δ13Corg and C:N) and an isotope mixing model were utilized to trace the contribution of mangrove-derived organic matter (MOM). Changes in the relative abundance of pollen from mangrove plants was used to compensate for diagenetic alteration of the stable isotope values and potential overlaps in isotope values for different sources of organic matter. The result of Pearson correlation analysis showed that the MOM was moderately positive correlated with total mangrove pollen, indicating that stable carbon isotopes and mangrove pollen provide similar information for tracing mangrove ecosystems. Based on results from this study, compositional changes in mangrove communities could be divided into two main stages: a degradation period (1870-1930 AD) and a flourishing period (1930-2011 AD), corresponding to colder temperature and warmer temperature, respectively. Owing to the location being far away from any industrial area and human activity, temperature may be a key factor for mangrove development. © 2015 Elsevier Ltd.

Wang K.,State Oceanic Administration | Wang K.,Function Laboratory for Marine Geology | Shi X.,State Oceanic Administration | Shi X.,Function Laboratory for Marine Geology | And 4 more authors.
Acta Oceanologica Sinica | Year: 2015

Generation, morphology, and distribution of authigenic minerals directly reflect sedimentary environment and material sources. Surface sediments were collected from the western Gulf of Thailand during 2011–2012, and 159 samples were analyzed to determine detrital minerals. Authigenic minerals, including siderite, pyrite, and glauconite, are abundant whereas secondary minerals, such as chlorite and limonite, are distributed widely in the study area. Siderite has a maximum content of 19.98 g/kg and appears in three types from nearshore to continental shelf, showing the process of forming-maturity-oxidation. In this process, the MnO content in siderite decreases, but Fe2O3 and MgO content increase. Colorless or transparent siderite pellets are fresh grains generated within a short time and widely distributed throughout the region; high content appears in coastal area where river inputs are discharged. Translucent cemented double pellets appearing light yellow to red are mature grains; high content is observed in the central shelf. Red-brown opaque granular pellets are oxidized grains, which are concentrated in the eastern gulf. Pyrite is mostly distributed in the central continental shelf with an approximately north–south strip. Pyrite are mainly observed in foraminifera shell and distributed in clayey silt sediments, which is similar to that in the Yangtze River mouth and the Yellow Sea. The pyrite in the gulf is deduced from genetic types associated with sulfate reduction and organic matter decomposition. Majority of glauconite are granular with few laminar. Glauconite is concentrated in the northern and southern parts within the boundary of 9.5° to 10.5°N and is affected by river input diffusion. The distribution of glauconite is closely correlated with that of chlorite and plagioclase, indicating that glauconite is possibly derived from altered products of chlorite and plagioclase. The K2O content of glauconite is low or absent, indicating its short formation time. © 2015 The Chinese Society of Oceanography and Springer-Verlag Berlin Heidelberg

Zhang H.T.,State Oceanic Administration | Yang Y.M.,State Oceanic Administration | Yang Y.M.,Function Laboratory for Marine Geology | Yan Q.-S.,State Oceanic Administration | And 8 more authors.
Geologica Acta | Year: 2016

The composition of melt inclusions in basalts erupted at mid-ocean ridges may be modified by post-entrapment processes, so the present composition of melt inclusions may not represent their original composition at the time of entrapment. By combining the melt inclusion composition in samples from the South Mid-Atlantic Ridge at 19°S analyzed in this study, and from the Petrological Database, we found that post-entrapment crystallization processes resulted in higher Ca/Al, Mg#[100 χ atomic Mg2+/(Mg2++Fe2+)], MgO and FeO contents, and lower CaO and Al2O3 contents of plagioclase-hosted melt inclusions relative to those hosted in olivine. In addition, melt inclusions hosted in plagioclase with anorthite content larger than 80mol.% had been modified more readily than others. By discussing the relationships between Ca/Al and fractional crystallization, post-entrapment crystallization, and the original melt composition, we propose that Ca/Al can be regarded as an indicator of the effect of post-entrapment processes on melt inclusion composition. Specifically, i) when Ca/Al<0.78, melt inclusion compositions corrected for fractional crystallization to Mg#=72 can represent the primary magma at mid-ocean ridges; ii) when 0.781.0, the compositions of melt inclusions do not reflect the original melt composition nor preserve information about the mantle source. According to these criteria, plagioclase-hosted melt inclusions with Ca/Al>1.0 in basalts from the South Mid-Atlantic Ridge at19°S cannot represent the composition of the melt at the moment of their entrapment. © 2016, Universitat de Barcelona. All rights reserved.

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