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1.
Matheus Carvalho de Carvalho Ken-ichi Hayashizaki Hisao Ogawa 《Journal of Oceanography》2008,64(5):705-712
Through 2004 and 2005, δ
34S of sinking material from Otsuchi Bay was measured at the center and rocky shore of the bay. At the center of the bay δ
34S was high (18∼21‰) in the material collected from April to November. However, δ
34S was low (9∼14‰) in the material collected from December to March. The increase in δ
34S in April was attributed to an increase in phytoplankton biomass because marine phytoplanktonic δ
34S is high. When δ
34S of sinking material was low, input of riverine material or bottom sediment resuspension were considered as the probable
causes, because their δ
34S is low. Marine sulfur was always high (more than 70%) at both stations. The difference between the δ
34S of sinking material collected from the different sampling stations indicates that marine macroalgae contribute to sinking
material near the shore when phytoplankton is scarce. In conclusion, the relative influence of different material sources
to sinking materials could be successfully estimated using δ
34S. 相似文献
2.
Geochemistry of pore waters from the Xisha Trough, northern South China Sea and their implications for gas hydrates 总被引:2,自引:0,他引:2
Shao-Yong Jiang Tao Yang Lu Ge Jing-Hong Yang Hong-Fei Ling Neng-You Wu Jian Liu Dao-Hua Chen 《Journal of Oceanography》2008,64(3):459-470
This paper reports all available geochemical data on sediments and pore waters from the Xisha Trough on the northern continental
margin of the South China Sea. The methane concentrations in marine sediments display a downhole increasing trend and their
carbon isotopic compositions (δ
13C = −25 to −51‰) indicate a thermogenic origin. Pore water Cl− concentrations show a range from 537 to 730 mM, and the high Cl− samples also have higher concentrations of Br−, Na+, K+, and Mg2+, implying mixing between normal seawater and brine in the basin. The SO4
2− concentrations of pore waters vary from 19.9 to 36.8 mM, and show a downhole decreasing trend. Calculated SMI (sulfate-methane
interfaces) depths and sulfate gradients are between 21 and 47 mbsf, and between −0.7 and −1.7 mM/m, respectively, which are
similar to values in gas hydrate locations worldwide and suggest a high methane flux in the basin. Overall, the geochemical
data, together with geological and geophysical evidence, such as the high sedimentation rates, high organic carbon contents,
thick sediment piles, salt and mud diapirs, active faulting, abundant thermogenic gases, and occurrence of huge bottom simulating
reflector (BSR), are suggestive of a favorable condition for occurrence of gas hydrates in this region. 相似文献
3.
Natural marine gas hydrate was discovered in Korean territorial waters during a 2007 KIGAM cruise to the central/southwestern
Ulleung Basin, East Sea. The first data on the geochemical characterization of hydrate-bound water and gas are presented here
for cold seep site 07GHP-10 in the central basin sector, together with analogous data for four sites (07GHP-01, 07GHP-02,
07GHP-03, and 07GHP-14) where no hydrates were detected in other cores from the central/southwestern sectors. Hydrate-bound
water displayed very low concentrations of major ions (Cl−, SO42−, Na+, Mg2+, K+, and Ca2+), and more positive δD (15.5‰) and δ18O (2.3‰) signatures compared to seawater. Cl– freshening and more positive isotopic values were also observed in the pore water at gas hydrate site 07GHP-10. The inferred
sulfate–methane interface (SMI) was very shallow (<5 mbsf) at least at four sites, suggesting the widespread occurrence of
anaerobic oxidation of methane (AOM) at shallow sediment depths, and possibly high methane flux. Around the SMI, pore water
alkalinity was very high (>40 mM), but the carbon isotopic ratios of dissolved inorganic carbon (δ13CDIC) did not show minimum values typical of AOM. Moreover, macroscopic authigenic carbonates were not observed at any of the
core sites. This can plausibly be explained by carbon with high δ13C values diffusing upward from below the SMI, increasing alkalinity via deep methanogenesis and eventually escaping as alkalinity
into the water column, with minor precipitation as solid phase. This contrasts, but is not inconsistent with recent reports
of methane-fuelled carbonate formation at other sites in the southwestern basin sector. Methane was the main hydrocarbon component
(>99.85%) of headspace, void, and hydrate-bound gases, C1/C2+ ratios were at least 1,000, and δ13CCH4 and δDCH4 values were in the typical range of methane generated by microbial reduction of CO2. This is supported by the δ13CC2H6 signatures of void and hydrate-bound gases, and helps clarify some contradictory interpretations existing for the Ulleung
Basin as a whole. In combination, these findings suggest that deep biogenic gas and pore waters migrate upward through pathways
such as hydrofractures, and measurably influence the shallow carbon cycle. As a result, cation-adjusted alkalinity/removed
sulfate diagrams cannot always serve to estimate the degree of alkalinity produced by sulfate reduction and AOM in high methane
flux areas. 相似文献
4.
厦门湾水体中颗粒有机碳的垂向输出通量:234Th/238U不平衡的应用 总被引:2,自引:1,他引:2
对厦门湾塔角附近海域某站位叶绿素 a、POC、初级生产力、234Th/238U不平衡进行的周日变化研究表明,POC含量介于14.4~34.6 mmol/m3之间,其中碎屑有机碳与活体有机碳所占份额分别为74%~92%和8%~26%.POC垂直分布呈现由表及底降低的趋势,且白昼期间POC含量高于晚间,说明研究海域POC含量与生物过程具有密切联系.初级生产力水平在1d之中变化达5倍,垂直分布亦随深度增加而降低,与叶绿素a的变化相对应.短时间(2h)培养获得的初级生产力水平明显高于长时间培养(24 h)的结果,证实部分新固定的碳被优先呼吸排出.结合234Th/238U不平衡法获得的颗粒态234Th输出通量及输出界面颗粒物中的POC/PTh比值,可计算出真光层 POC的垂向输出通量为16.0mmol/(m2·d),其中碎屑有机碳与活体有机碳贡献的数量分别为13.3和2.7mmol/(m2·d).POC输出通量与初级生产力的比值(ThE比值)平均为0.31,真光层POC停留时间平均为11d.上述结果与Aksnes和Wassmann[1]的模型计算结果相吻合,但与其他大多数模型的结果仍存在一定的差异. 相似文献
5.
Stable Carbon and Nitrogen Isotopic Characterization of Organic Matter in a Mangrove Ecosystem on the Southwestern Coast of Thailand 总被引:1,自引:0,他引:1
Organic matter in a tropical mangrove ecosystem was characterized by stable carbon and nitrogen isotopic analyze, conducted
on various organic samples, including land and mangrove plants, soils, particulate organic matter (POM), and sea and river
sediments along the southwestern coast of Thailand. The δ13C values of land plants and POM in river water can be explained in terms of a greater influence of C3 plants than C4 plants in this area. The POM and sediments from the Trang River and Ko Talibong area showed systematically higher δ15N values than those from Ko Muk and other coastal areas. Organic matter in the Trang River might be influenced by nitrogen
released from agricultural or human waste, which could affect the isotopic composition of POM and sediments in the Trang River
estuary and along the coast near the river mouth. We used a stochastic method to estimate the contributions of four organic
end-members, identifiable by their δ13C and δ15N values. The results implied that seagrasses were a major source of sedimentary organic matter, contributing 42 ± 5% in the
Ko Muk area and 36 ± 5% in the Ko Talibong area. The contribution of coastal POM to sediments was estimated to be only 13%
in Ko Muk and 19% in Ko Talibong. Mangrove plants contributed approximately 23% in both areas. It was concluded that seagrasses
are an important source of sedimentary organic matter in this coastal region of southwestern Thailand.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
6.
We utilized 234Th, a naturally occurring radionuclide, to quantify the particulate organic carbon (POC) export rates in the northern South
China Sea (SCS) based on data collected in July 2000 (summer), May 2001 (spring) and November 2002 (autumn). Th-234 deficit
was enhanced with depth in the euphotic zone, reaching a subsurface maximum at the Chl-a maximum in most cases, as commonly
observed in many oceanic regimes. Th-234 was in general in equilibrium with 238U at a depth of ∼100 m, the bottom of the euphotic zone. In this study the 234Th deficit appeared to be less significant in November than in July and May. A surface excess of 234Th relative to 238U was found in the summer over the shelf of the northern SCS, most likely due to the accumulation of suspended particles entrapped
by a salinity front. Comparison of the 234Th fluxes from the upper 10 m water column between 2-D and traditional 1-D models revealed agreement within the errors of
estimation, suggesting the applicability of the 1-D model to this particular shelf region. 1-D model-based 234Th fluxes were converted to POC export rates using the ratios of bottle POC to 234Th. The values ranged from 5.3 to 26.6 mmol C m−2d−1 and were slightly higher than those in the southern SCS and other oligotrophic areas. POC export overall showed larger values
in spring and summer than in autumn, the seasonality of which was, however, not significant. The highest POC export rate (26.6
mmol C m−2d−1) appeared at the shelf break in spring (May), when Chl-a increased and the community structure changed from pico-phytoplankton
(<2 μm) dominated to nano-phytoplankton (2–20 μm) and micro-phytoplankton (20–200 μm) dominated. 相似文献
7.
Concentration and stable isotopic compositions (δ
18O) of dissolved O2 were measured in seawater samples collected from the Philippine Sea in June 2006. The in-situ O2 consumption rate and the isotopic fractionation factor (α
r
) during dissolved O2 consumption were obtained from field observations by applying a vertical one-dimensional advection diffusion model to the
deep water mass of about 1000–4000 m. The average O2 consumption rate and α
r
were, respectively, 0.11 ± 0.07 μmol kg−1yr−1 and 0.990 ± 0.001. These estimated values agree well with values from earlier estimations of Pacific deep water. The in-situ O2 consumption rates are two or more times higher north of 20°N, although the value of α
r
was not significantly different between the north and south. Its levels varied rapidly in the water mass of less about 2000
m depth. These results suggest that organic matter from the continent imparts a meaningful contribution to the upper water
in the northern part of the area; it might produce the strong O2 minimum that is evident in the water mass from about 1000–2000 m in the northern part of the Philippine Sea. 相似文献
8.
海底地下水排放对典型红树林蓝碳收支的影响 总被引:1,自引:0,他引:1
海底地下水排放(Submarine Groundwater Discharge,SGD)是陆海相互作用的重要表现形式之一,其携带的物质对近岸海域生源要素的收支有重要影响。本文利用222Rn示踪技术估算了我国典型红树林海湾—广西珍珠湾在2019年枯季(1月)SGD携带的碳通量。调查发现,地下水中222Rn活度、溶解无机碳(DIC)和溶解有机碳(DOC)的平均浓度均高于河水和湾内表层海水。利用222Rn质量平衡模型估算得到珍珠湾SGD速率为(0.36±0.36) m/d,SGD输入到珍珠湾的DIC和DOC通量分别为(2.41±2.63)×107 mol/d和(1.96±2.20)×106 mol/d。珍珠湾溶解碳的源汇收支表明,SGD携带的DIC和DOC分别占珍珠湾总DIC和总DOC来源的91%和89%。因此,SGD携带的DIC和DOC是珍珠湾DIC和DOC的主要来源,是海岸带蓝碳收支和生物地球化学循环过程中的重要组成。 相似文献
9.
根据2018年7月、11月和2019年1月、4月对广东考洲洋牡蛎养殖海域进行4个季节调查获得的p H、溶解无机碳(DIC)、水温、盐度、溶解氧(DO)及叶绿素a(Chla)等数据,估算该区域表层海水溶解无机碳体系各分量的浓度、初级生产力(PP)、表层海水CO2分压[p(CO2)]和海-气界面CO2交换通量(FCO2),分析牡蛎养殖活动对养殖区碳循环的影响。结果表明:牡蛎养殖区表层海水中Chl a、DIC、HCO3–和PP显著低于非养殖区;养殖淡季表层海水中pH、DO、DIC、HCO3–、和CO32–显著大于养殖旺季,养殖旺季的p(CO2)和FCO2显著大于养殖淡季。牡蛎养殖区表层海水夏季、秋季、冬季和春季的海-气界面CO2交换通量FCO2平均值分别是(42.04±9.56)、(276... 相似文献
10.
Graham P. Wilson Angela L. Lamb Melanie J. Leng Silvia Gonzalez David Huddart 《Estuarine, Coastal and Shelf Science》2005,64(4):685-698
Microfossil analysis (e.g. diatoms, foraminifera and pollen) represents the cornerstone of Holocene relative sea-level (RSL) reconstruction because their distribution in the contemporary inter-tidal zone is principally controlled by ground elevation within the tidal frame. A combination of poor microfossil preservation and a limited range in the sediment record may severely restrict the accuracy of resulting RSL reconstructions. Organic δ13C and C/N analysis of inter-tidal sediments have shown some potential as coastal palaeoenvironmental proxies. Here we assess their viability for reconstructing RSL change by examining patterns of organic δ13C and C/N values in a modern estuarine environment. δ13C and C/N analysis of bulk organic inter-tidal sediments and vegetation, as well as suspended and bedload organic sediments of the Mersey Estuary, U.K., demonstrate that the two main sources of organic carbon to surface saltmarsh sediments (terrestrial vegetation and tidal-derived particulate organic matter) have distinctive δ13C and C/N signatures. The resulting relationship between ground elevation within the tidal frame and surface sediment δ13C and C/N is unaffected by decompositional changes. The potential of this technique for RSL reconstruction is demonstrated by the analysis of part of an early Holocene sediment core from the Mersey Estuary. Organic δ13C and C/N analysis is less time consuming than microfossil analysis and is likely to provide continuous records of RSL change. 相似文献
11.
A carbon,nitrogen, and sulfur elemental and isotopic study in dated sediment cores from the Louisiana Shelf 总被引:2,自引:0,他引:2
Robert J. Rosenbauer Peter W. Swarzenski Carol Kendall William H. Orem Frances D. Hostettler Mark E. Rollog 《Geo-Marine Letters》2009,29(6):415-429
Three sediment cores were collected off the Mississippi River delta on the Louisiana Shelf at sites that are variably influenced
by recurring, summer-time water-column hypoxia and fluvial loadings. The cores, with established chronology, were analyzed
for their respective carbon, nitrogen, and sulfur elemental and isotopic composition to examine variable organic matter inputs,
and to assess the sediment record for possible evidence of hypoxic events. Sediment from site MRJ03-3, which is located close
to the Mississippi Canyon and generally not influenced by summer-time hypoxia, is typical of marine sediment in that it contains
mostly marine algae and fine-grained material from the erosion of terrestrial C4 plants. Sediment from site MRJ03-2, located
closer to the mouth of the Mississippi River and at the periphery of the hypoxic zone (annual recurrence of summer-time hypoxia
>50%), is similar in composition to core MRJ03-3, but exhibits more isotopic and elemental variability down-core, suggesting
that this site is more directly influenced by river discharge. Site MRJ03-5 is located in an area of recurring hypoxia (annual
recurrence >75%), and is isotopically and elementally distinct from the other two cores. The carbon and nitrogen isotopic
composition of this core prior to 1960 is similar to average particulate organic matter from the lower Mississippi River,
and approaches the composition of C3 plants. This site likely receives a greater input of local terrestrial organic matter
to the sediment. After 1960 and to the present, a gradual shift to higher values of δ13C and δ15N and lower C:N ratios suggests that algal input to these shelf sediments increased as a result of increased productivity
and hypoxia. The values of C:S and δ34S reflect site-specific processes that may be influenced by the higher likelihood of recurring seasonal hypoxia. In particular,
the temporal variations in the C:S and δ34S down-core are likely caused by changes in the rate of sulfate reduction, and hence the degree of hypoxia in the overlying
water column. Based principally on the down-core C:N and C:S ratios and δ13C and δ34S profiles, sites MRJ03-3 and MRJ03-2 generally reflect more marine organic matter inputs, while site MRJ03-5 appears to be
more influenced by terrestrial deposition. 相似文献
12.
Spatial variability in the primary productivity in the East China Sea and its adjacent waters 总被引:7,自引:0,他引:7
Primary productivity in the East China Sea and its adjacent area was measured by the13C tracer method during winter, summer and fall in 1993 and 1994. The depth-integrated primary productivity in the Kuroshio
Current ranged from 220 to 350 mgC m−2d−1, and showed little seasonal variability. High primary productivity (above 570 mgC m−2d−1) was measured at the center of the continental shelf throughout the observation period. The productivity at the station nearest
to the Changjiang estuary exhibited a distinctive seasonal change from 68 to 1,500 mgC m−2d−1. Depth-integrated primary productivity was 2.7 times higher in the shelf area than the rates at the Kuroshio Current. High
chlorophyll-a specific productivity (mgC mgChl.-a−2d−1) throughout the euphotic zone was mainly found in the shelf area rather than off-shelf area, probably due to higher nutrient
availability and higher activity of phytoplankton at the subsurface layer in the shelf area. 相似文献
13.
Data from piston cores collected from Carolina Rise and Blake Ridge, and from many DSDP/ODP sites indicate that extreme 13C-depletion of methane and ΣCO2 occurs within the uppermost methanogenic zone of continental rise sediments. We infer that 13C-depleted methane is generated near the top of the methanogenic zone when carbon of 13C-depleted ΣCO2, produced by microbially-mediated anaerobic methane oxidation, is recycled back to methane through CO2 reduction. Interstitial water and gas samples were collected in 27 piston cores, 16 of which penetrated through the sulfate reduction zone into methane-bearing sediments of the Carolina Rise and Blake Ridge. Isotopic measurements (δ13CCH4, δ13CCO2, δDCH4, and δDH2O) indicate that this methane is microbial in origin, produced by microbially-mediated CO2 reduction. Methane samples form two distinct isotopic pools. (1) Methane from a seafloor seep site shows a mean δ13CCH4 value of − 69 ± 2%., mirroring values found at ≥ 160 mbsf from a nearby DSDP site. (2) Twenty, areally-separated sites (sample depth, 10 to 25 mbsf) have δ13CCH4 values ranging from −85 to −103%., and δ13CCO2 as negative as −48%.. The very low δ13C values from the methane and CO2 pools highlight the importance of carbon cycling within continental rise sediments at and near the sulfate-methane boundary. 相似文献
14.
P. Jean-Baptiste A. Dapoigny M. Stievenard J. L. Charlou Y. Fouquet J. P. Donval J. M. Auzende 《Geo-Marine Letters》1997,17(3):213-219
Hydrothermal vent fields south of the Garret Fracture zone were sampled for the isotope composition of helium and oxygen
([18O]H2O/[16OH2O). The helium isotopes end-member (3He / 4He=8.3×R
a
and [4He]≈1.2–2.4×10-5 cm3 STP g-1) is quite similar to other known hydrothermal sites pointing to the homogeneous helium composition of the upper mantle. The
δ18O end-member value (δ18O≈0.5–0.6‰) confirms previous suggestions from other sites and from isotope modeling, that hydrothermal fluids are slightly
enriched in 18O relative to the ocean as a result of water–rock interactions at high temperature.
Received: 11 December 1995/Revision received: 20 December 1996 相似文献
15.
Christopher T. Mills Robert F. Dias Dennis Graham Kevin W. Mandernack 《Marine Chemistry》2006,98(2-4):197-209
Sediment samples ranging from 0.05 to 278 m below sea floor (mbsf) at a Northwest Pacific deep-water (5564 mbsl) site (ODP Leg 191, Site 1179) were analyzed for phospholipid fatty acids (PLFAs). Total PLFA concentrations decreased by a factor of three over the first meter of sediment and then decreased at a slower rate to approximately 30 mbsf. The sharp decrease over the first meter corresponds to the depth of nitrate and Mn(IV) reduction as indicated by pore water chemistry. PLFA-based cell numbers at site 1179 had a similar depth profile as that for Acridine orange direct cell counts previously made on ODP site 1149 sediments which have a similar water depth and lithology. The mole percentage of straight chain saturated PLFAs increases with depth, with a large shift between the 0.95 and 3.95 mbsf samples. PLFA stable carbon isotope ratios were determined for sediments from 0.05 to 4.53 mbsf and showed a general trend toward more depleted δ13C values with depth. Both of these observations may indicate a shift in the bacterial community with depth across the different redox zones inferred from pore water chemistry data. The PLFA 10me16:0, which has been attributed to the bacterial genera Desulfobacter in many marine sediments, showed the greatest isotopic depletion, decreasing from − 20 to − 35‰ over the first meter of sediment. Pore water chemistry suggested that sulfate reduction was absent or minimal over this same sediment interval. However, 10me16:0 has been shown to be produced by recently discovered anaerobic ammonium oxidizing (anammox) bacteria which are known chemoautotrophs. The increasing depletion in δ13C of 10me16:0 with the unusually lower concentration of ammonium and linear decrease of nitrate concentration is consistent with a scenario of anammox bacteria mediating the oxidation of ammonium via nitrite, an intermediate of nitrate reduction. 相似文献
16.
We have measured helium isotopic ratios of thirty-seven Pacific water samples from various depths collected in adjacent regions
of Honshu, Japan. The 3He/4He ratios vary significantly from 0.989 R
atm to 1.208 R
atm where R
atm is the atmospheric ratio of 1.39 × 10−6. The mid-depth (750–1500 m) profile of 3He/4He ratios at ST-1 located Northwestern Pacific Ocean east of Japan (Off Joban; 37°00′ N, 142°40′ E) is significantly different
from that at ST-2 of the Northern Philippine Sea south of Japan (Nankai Trough; 33°07′ N, 139°59′ E), suggesting that these
waters were separated by a topographic barrier, the Izu-Ogasawara Ridge. Taking 3He/4He data of the Geosecs expeditions in the western North Pacific, an extensive plume of 15% excess 3He relative to the air may be traced at ST-1 over 12,000 kilometers to the northwest of the East Pacific Rise where the mantle
helium may originate. The 20% excess found at ST-2 may be attributable to the additional source of the subduction-type mantle
helium in the Okinawa Trough. A 15% excess of 3He has also been discovered at a depth of about 1000∼1500 m at ST-3 adjacent to Miyakejima Island (33°57′ N, 139°22′ E) and
ST-4 of Sagami Bay (35°00′ N, 139°22′ E). It is confirmed that mid-depth all over the western North Pacific water is affected
by the mantle helium with a high 3He/4He ratio.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
17.
Assessment of nitrogen loading from the Kiso-Sansen Rivers into Ise Bay using stable isotopes 总被引:1,自引:0,他引:1
Ryo Sugimoto Akihide Kasai Kouichi Fujita Kenichi Sakaguchi Tomomi Mizuno 《Journal of Oceanography》2011,67(2):231-240
Concentrations of particulate organic nitrogen (PN), dissolved inorganic nitrogen (DIN), and their nitrogen isotope ratios
(δ
15N) in the Kiso-Sansen Rivers were determined from monthly observations over the course of a year to assess variations in the
form and sources of riverine nitrogen discharged into Ise Bay. The δ
15N values of NO3
− observed in the Kiso-Sansen Rivers showed a logarithmic decreasing trend from 8 to 0‰, which varied with the river discharge,
indicating mixing between point sources with high δ
15N and non-point sources with low δ
15N. The influence of isotope fractionation of in situ biogeochemical processes (mainly DIN assimilation by phytoplankton) on
δ
15N of NO3
− was negligible, because sufficient concentrations of NH4
+ for phytoplankton demand would inhibit the assimilation of NO3
−. A simple relationship between river discharge and δ
15N of NO3
− showed that the fraction of total NO3
− flux arising from point sources increased from 4.0–6.3% (1.1–1.8 tN day−1) during higher discharge (>600 m3 s−1) to 30.2–48.3% (2.6–4.1 tN day−1) during lower discharge (<300 m3 s−1). Riverine NO3
− discharge from the Kiso-Sansen Rivers can explain 75% of the variations in surface NO3
− at the head of Ise Bay over the year. 相似文献
18.
Hajime Kawakami Makio C. Honda Masahide Wakita Shuichi Watanabe 《Journal of Oceanography》2007,63(6):967-982
Time-series measurements of dissolved inorganic carbon (DIC) and nutrient concentrations were conducted in the northwestern
North Pacific from October 2002 to August 2004. Assuming that data obtained in different years represented time-series seasonal
data for a single year, vertical distributions of DIC and nutrients showed large seasonal variabilities in the surface layer
(∼100 m). Seasonal variabilities in normalized DIC (nDIC) and nitrate concentrations at the sea surface were estimated to
be 81–113 μmol kg−1 and 12.7–15.7 μmol kg−1, respectively, in the Western Subarctic Gyre. The variability in nutrients between May and July was generally at least double
that in other seasons. In the Western Subarctic Gyre, estimations based on statistical analyses revealed that seasonal new
production was 39–61 gC m−2 and tended to be higher in the southwestern regions or coastal regions. The seasonal new productions in the northwestern
North Pacific were two or more times higher than in the North Pacific subtropical gyre and the northeastern North Pacific.
It is likely that this difference is due to spatial variations in the concentrations of trace metals and the species of phytoplankton
present. In addition, from estimations of surface pCO2 it was verified that the Western Subarctic Gyre is a source of atmospheric CO2 between February and May and a sink for CO2 between July and October. 相似文献
19.
Hodaka Kawahata Mayuri Inoue Masato Nohara Atsushi Suzuki 《Journal of Oceanography》2006,62(4):405-412
The δ18O, δ13C and trace element composition of pearls collected from Ago Bay, Japan, were investigated in order to evaluate biomineralization
in the cultured pearl oyster (Pinctada fucata martensii). The oxygen isotopic data suggest that the pearls were produced around 23–24°C, mainly in June to early July, which is consistent
with their occurrence in the field. Therefore the pearls were produced under or close to isotopic equilibrium conditions,
although they showed high calcification rates (higher than 0.2–1.0 g cm− 2yr−1) under which, for example, coral skeletons (calcification rate ∼0.28 g cm− 2yr−1) often show non-equilibrium isotope partitioning. The δ13C values were ∼− 2.9‰ lower than those calculated for offshore waters under equilibrium conditions. This may be due to low-δ13C bottom waters resulting from the degradation of organic matter (OM) or to a contribution of low-δ 13C food. In the latter case, a simple mass balance calculation gives a respiration component of 14%. Twelve trace elements
of bulk pearl samples were classified into four groups on the basis of their enrichment/depletion patterns relative to seawater
and inter-element relationships: group 1, Co, Cr, Pb; group 2, Ba, Cs, U; group 3, Cu, Sn, V, and group 4, Mn, Rb, Mo. Comparison
with coral skeletons suggests that Ba and Mn (groups 2 and 4) were definitely much enriched in proteinaceous OM relative to
aragonite crystals in pearls and that V (group 3) in pearls showed only slight enrichment in the organicrich layer. By contrast,
the other elements showed small differences between both layers (enrichment factor of <3), suggesting that these elements
occur largely in aragonite crystals. 相似文献
20.
Stable isotope analysis of some representative fish and invertebrates of the Newfoundland and Labrador continental shelf food web 总被引:3,自引:1,他引:3
We examined stable carbon and nitrogen isotopic signatures of 17 fish and 16 invertebrate taxa common to the Newfoundland and Labrador (NL) continental shelf food web. Particular sampling emphasis was placed on Atlantic cod (Gadus morhua) and related prey species (e.g. shrimp, Pandalus borealis, and capelin, Mallotus villosus). We found highly significant (p < 0.0001) differences between near-shore (bays) and offshore (shelf edge) δ15N signatures for cod, ‘other fish’ (pooled) and invertebrates (pooled). In contrast, there were only minor differences in δ13C signatures of ‘other fish’ (p < 0.05) and no difference for cod and invertebrates among the two habitats. We sampled at two times of the year (January and June) and found no systematic effect of season on both δ13C and δ15N in cod, ‘other fish’ and invertebrates. We calculated isotopic fractionation factors for cod from the entire shelf (mixed diet) and for cod with diets composed mainly of capelin or shrimp. These values ranged between 2.2‰ and 3.9‰ for δ15N and −0.4‰ and 0.8‰ for δ13C and, for δ15N, may reflect diet-related differences in bioenergetic status. We discuss potential mechanisms for near-shore versus offshore enrichment of δ15N signatures, and demonstrate the implications of this spatial variation on δ15N-derived trophic position estimates. 相似文献