硇洲岛大型海藻群落的季节演替*

2011年4月至2012年1月对硇洲岛潮间带大型海藻进行了周年的季节调查, 结果表明, 调查海域大型海藻共有64种。其中褐藻门15种, 占总种类数的23.44%; 红藻门28种, 占总种类数的43.75%; 绿藻门20种, 占总种类数的31.25%; 蓝藻门1种, 占总种类数的1.56%。其种类数春季最多, 共43种; 夏季24种; 秋季29种; 冬季31种。有9个物种为4个季节共有种, 有14个物种为3个季节共有种。各季节间共有种类数为12~26种, 季节间种类更替率为0.42~0.78, 春夏季种类更替率最高, 秋冬季种类更替率最低。优势种共有13种, 仅拟鸡毛菜Pterocladiella capillacea为全年优势种, 而半叶马尾藻Sargassum hemiphyllum和小珊瑚藻Corallina pilulifera为3个季节共有优势种。调查海域大型海藻生物量季节变化明显, 平均生物量春季最高, 冬季次之, 夏季最低。不同物种其垂直分带明显, 从高潮区往低潮区种类数不断增多; 生物量也是从高潮区往低潮区逐渐增大。物种多样性指数变化范围为0.03~2.33, 年均值为1.10; 均匀度变化范围为0.01~0.70, 年均值为0.36; 种类丰富度指数变化范围为0.15~1.65, 年均值为0.72; 辛普森优势度指数变化范围为0.01~0.78, 年均值为0.39。各大型海藻含水率变化范围在51.92%~97.52%, 平均值为85.21%; 总有机碳含量变化范围在4.34%~42.06%, 平均为27.99%。相关性分析发现, 调查海域大型海藻生物量与无机氮(DIN)呈显著负相关, 相关系数为0.49(P＜0.05), 与其他环境因子的相关性不明显。在大型海藻生长旺盛的冬春季, 海水中的无机氮(DIN)含量最低, 与其他自然海域冬季营养盐积累规律显著不同。     

Seasonal and Interannual Variability in the Distribution of Surface Nutrients and Dissolved Inorganic Carbon in the Northern North Pacific: Influence of El Niño

The seasonal and interannual changes in surface nutrients, dissolved inorganic carbon (DIC) and total alkalinity (TA) were recorded in the North Pacific (30–54°N) from 1995 to 2001. This study focuses on the region north of the subarctic boundary (∼40°N) where there was extensive monthly coverage of surface properties. The nutrient cycles showed large interannual variations in the eastern and western subarctic gyres. In the Alaska Gyre the seasonal depletion of nitrate (ΔNO₃) increased from 8–14 μmol kg⁻¹ in 1995–1999 to 21.5 μmol kg⁻¹ in 2000. In the western subarctic the shifts were similar in amplitude but more frequent. The large ΔNO₃ levels were associated with high silicate depletions, indicating enhanced diatom production. The seasonal DIC:NO₃ drawdown ratios were elevated in the eastern and central subarctic due to calcification. In the western subarctic and the central Bering Sea calcification was significant only during 1997 and/or 1998, two El Ni?o years. Regional C/N stoichiometric molar ratios of 5.7 to 7.0 (>40°N) were determined based on the years with negligible or no calcification. The annual new production (NP_a) based on ΔNO₃ and these C/N ratios showed large interannual variations. NP_a was usually higher in the western than in the eastern subarctic. However, values of 84 gC m⁻²yr⁻¹ were found in the Alaska Gyre in 2000 which is similar to that in the most productive provinces of the northern North Pacific. There were also large increases in NP_a around the Alaska Peninsula in 1997 and 1998. Finally, the net removal of carbon by the biological pump was estimated as 0.72 Gt C yr⁻¹ in the North Pacific (>30°N). This revised version was published online in August 2006 with corrections to the Cover Date.     

The Functions of China Marginal Sea Sediments in the Cycle of Biogenic Elements

The contents of biogenic elements in China marginal sea sediments are related to their grain sizes, river transport, et al. In general, the finer the grain size is, the higher the contents of organic matter and OC, N, P are, the lower the contents of S and Si are. The biogeochemical environments of sediments are related to Eh, pH, temperature content of OC,Fe3 /Fe2 radio, water dynamics condition, grain size of sediment, S system in sediment interstitial waters, et al., and they influence the early diageneses and cycle of biogenic elements in sediments. In most regions of China marginal sea, the flux directions of S2-, HS-,3- NH4 H4SiO4, PO4 , across the sediment-water interface are from sediment to the overlying seawater, the flux directions of SO42-, HCO3-, NO3-, NO2- across the sediment-water interface are from the overlying seawater to sediment. The irrigation of living things is important in the cycle of the biogenic elements across sediment-water interfaces.     

Parameterization of iron and manganese cycling in the Black Sea suboxic and anoxic environment

New and published data on the distribution and speciation of manganese and iron in seawater are analyzed to identify and parameterize major biogeochemical processes of their cycling within the suboxic (15.6σ_t16.2) and anoxic layers (σ_t16.2) of the Black Sea. A steady-state transport-reaction model is applied to reveal layering and parameterize kinetics of redox and dissolution/precipitation processes. Previously published data on speciation of these elements in seawater are used to specify the nature of the transformations. Two particulate species of iron (Fe(III) hydroxide and Fe(II) sulfide) are necessary to adequately parameterize the vertical profile of suspended iron, while three particulate species (hydrous Mn(IV) oxide, Mn(II) sulfide, and Mn(II) carbonate) are necessary to describe the profile of suspended manganese. In addition to such processes as mixing and advection, precipitation, sinking, and dissolution of manganese carbonate are found to be essential in maintaining the observed vertical distribution of dissolved Mn(II). These results are used to interpret the observed difference in the form of vertical distribution for dissolved Mn(II) and Fe(II). Redox transformations of iron and manganese are coupled via oxidation of dissolved iron by sinking suspended manganese at σ_t16.2±0.2 kg m⁻³. The particulate manganese, necessary for this reaction, is supplied through oxidation of dissolved Mn(II). The best agreement with observations is achieved when nitrate, rather than oxygen, is set to oxidize dissolved Mn(II) in the lower part of the suboxic layer (15.90σ_t16.2). The results support the idea that, after sulfides of these metals are formed, they sink with particulate organic matter. The sinking rates of the particles and specific rates of individual redox and dissolved-particulate transformations have been estimated by fitting the vertical profile of the net rate.     

Simulation of upper-ocean biogeochemistry with a flexible-composition phytoplankton model: C, N and Si cycling in the western Sargasso Sea

We report the first application of a biogeochemical model in which the major elemental composition of the phytoplankton is flexible, and responds to changing light and nutrient conditions. The model includes two phytoplankton groups: diatoms and non-siliceous picoplankton. Both fix C in accordance with photosynthesis-irradiance relationships used in other models and take up NO₃⁻ and NH₄⁺ (and Si(OH)₄ for diatoms) following Michaelis-Menten kinetics. The model allows for light dependence of photosynthesis and NO₃⁻ uptake, and for the observed near-total light independence of NH₄⁺ uptake and Si(OH)₄ uptake. It tracks the resulting C/N ratios of both phytoplankton groups and Si/N ratio of diatoms, and permits uptake of C, N and Si to proceed independently of one another when those ratios are close to those of nutrient-replete phytoplankton. When the C/N or Si/N ratio of either phytoplankton group indicates that its growth is limited by N, Si or light, uptake of non-limiting elements is controlled by the content of the limiting element in accordance with the cell-quota formulation of Droop (J. Mar. Biol. Ass. U.K 54 (1974) 825).We applied this model to the Bermuda Atlantic Time-series Study (BATS) site in the western Sargasso Sea. The model was tuned to produce vertical profiles and time courses of [NO₃⁻], [NH₄⁺] and [Si(OH)₄] that are consistent with the data, by adjusting the kinetic parameters for N and Si uptake and the rate of nitrification. The model then reproduces the observed time courses of chlorophyll-a, particulate organic carbon and nitrogen, biogenic silica, primary productivity, biogenic silica production and POC export with no further tuning. Simulated C/N and Si/N ratios of the phytoplankton indicate that N is the main growth-limiting nutrient throughout the thermally stratified period and that [Si(OH)₄], although always limiting to the rate of Si uptake by diatoms, seldom limits their growth rate. The model requires significant nitrification in the upper 200 m to yield realistic time courses and vertical profiles of [NH₄⁺] and [NO₃⁻], suggesting that NO₃⁻ is not supplied to the upper water column entirely by physical processes. A nitrification-corrected f-ratio (f_NC), calculated for the upper 200 m as: (NO₃⁻ uptake—nitrification)/(NO₃⁻ uptake+NH₄⁺ uptake) has annual values ranging from only 0.05–0.09, implying that 90–95% of the N taken up annually by phytoplankton is supplied by biological regeneration (including nitrification) in the upper 200 m. Reported discrepancies between estimates of organic C export based on seasonal chemical changes and POC export measured at the BATS site can be almost completely resolved if there is significant regeneration of NO₃⁻ via organic-matter decomposition in the upper 200 m.     

Incorporation of aged dissolved organic carbon (DOC) by oceanic particulate organic carbon (POC): An experimental approach using natural carbon isotopes

Incorporation of ¹⁴C-depleted (old) dissolved organic carbon (DOC) on/into particulate organic carbon (POC) has been suggested as a possible mechanism to explain the low Δ¹⁴C-POC values observed in the deep ocean [Druffel, E.R.M., Williams, P.M., 1990. Identification of a deep marine source of particulate organic carbon using bomb ¹⁴C. Nature, 347, 172–174.]. A shipboard incubation experiment was performed in the Sargasso Sea to test this hypothesis. Finely ground dried plankton was incubated in seawater samples from the deep Sargasso Sea, both with and without a biological poison (HgCl₂). Changes in parameters such as biochemical composition and carbon isotopic signatures of bulk POC and its organic compound classes were examined to study the roles of sorptive processes and biotic activity on POC character. Following a 13-day incubation, the relative abundance of the acid-insoluble organic fraction increased. Abundances of extractable lipids and total hydrolyzable amino acids decreased for both treatments, but by a greater extent in the non-poisoned treatment. The Δ¹⁴C values of POC recovered from the non-poisoned treatment were significantly lower than the value of the unaltered plankton material used for the incubation, indicating incorporation of ¹⁴C-depleted carbon, most likely DOC. The old carbon was present only in the lipid and acid-insoluble fractions. These results are consistent with previous findings of old carbon dominating the same organic fractions of sinking POC from the deep Northeast Pacific [Hwang, J., Druffel, E.R.M., 2003. Lipid-like material as the source of the uncharacterized organic carbon in the ocean? Science, 299, 881–884.]. However, the Δ¹⁴C values of POC recovered from the poisoned treatment did not change as much as those from the non-poisoned treatment suggesting that biological processes were involved in the incorporation of DOC on/into POC.     

Model Simulations of Carbon Sequestration in the Northwest Pacific by Direct Injection

The direct disposal of CO₂ into the ocean interior represents a possible means to help mitigate rising levels of atmospheric CO₂. Here, we use three different versions of an ocean general circulation model (OGCM) to simulate the direct injection of liquid CO₂ near Tokyo. Our results confirm that direct injection can sequester large amounts of CO₂ from the atmosphere when disposal is made at sufficient depth (80–100% of the carbon injected at 3000 m remains in the ocean after 500 years) but show that the calculated efficiency is rather sensitive to the choice of physical model. Moreover, we show, for the first time in an OGCM and under a reasonable set of economic assumptions, that sequestration effectiveness is quite high for even shallow injections. However, the severe acidification that accompanies injection and the impossibility of effectively monitoring injected plumes argue against the large-scale viability of this technology. Our coarse-grid models show that injection at the rate of 0.1 Pg-C/yr lowers pH near the site of injection by as much as 0.7–1.0 pH-unit. Such pH anomalies would be much larger in more finely gridded models (and in reality) and have potential to severely harm deep-sea organisms. We also show that, after several hundred years, one would effectively need to survey the entire ocean in order to accurately verify the inventory of injected carbon. These results suggest that while retention may be sufficient to justify disposal costs, other practical problems will limit or at best delay widespread deployment of this technology.     

海洋微藻的体外抗肿瘤活性初筛

采用小鼠乳腺癌细胞株tsFT210的细胞周期抑制、细胞凋亡诱导、细胞坏死以及对卤虫的毒性为活性指标,对48种海洋微藻的甲醇提取物的抗肿瘤活性进行了筛选。结果表明,以卤虫毒性为活性指标时,9种海洋微藻显示了不同程度的抗肿瘤活性,以tsFT210为筛选模型时,也有9种具有抗肿瘤活性,其中3种为明显的细胞凋亡诱导活性、2种为细胞坏死性活性、1种为G2/M期抑制活性,因此有必要进行开拓海洋微藻药用新资源的研究。     

黄、东海温盐跃层的分布特征及其季节变化

利用“中韩水循环动力学合作研究”和“中国近海海洋环境综合调查”( 1 996年 4月 -1 999年 1月 )期间各季节 1 2 8°E以西的校正后的 CTD现场水文调查资料 ,对黄、东海温、盐跃层在 4个不同时期 (成长、强盛、消衰和无跃期 )的各特征值的分布特性及其季节变化作了探讨和分析。结果表明 :( 1 )黄海底层显著冷水团的存在 ,使黄海以温跃层占绝对主导地位 ;东海的沿岸海区因受长江径流的影响则以盐跃层为主导。 ( 2 )温跃层的强度主要取决于与其相联的上、下层水团的强弱。冷水团的存在是产生强跃层的根本原因。( 3)夏季东海区双温跃层从浙江近海到济州岛以南水域连成片 ,其分布范围恰好与冬季入侵陆架的黑潮水相一致。 ( 4 )长江冲淡水舌状盐跃层强度等值线在各季节的伸展情况反映了长江冲淡水在各季节的扩散情况 ,一年当中 ,其轴向先从南往北转 ,再从北往南转。 ( 5 )苏北浅滩以及台湾海峡北部终年为无跃区     

Time-series observation of dissolved inorganic carbon and nutrients in the northwestern North Pacific

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.