刘公岛海洋牧场底层海水溶解氧浓度的变化特征

由于缺乏长期观测资料,前人对山东半岛邻近海域海水溶解氧的时间变化和空间分布特征的研究较少。本文基于威海刘公岛海洋牧场于2016年7月20日至2017年3月14日期间,利用生态环境实时在线观测系统获得的底层海水的温度、盐度、水深、溶解氧数据,分析了该牧场海水溶解氧浓度的时间变化特征及其影响因素,并探讨了低氧灾害发生的可能性。结果表明在观测期间,该牧场海水溶解氧浓度以季节变化为主,冬季最大、夏季最小,其中2月份平均值最高,约为10.86mg/L,8月份平均值最低,约为5.91mg/L。同时海水溶解氧浓度也存在显著的小时变化和日变化,且变化幅度于8月份最大、3月份最小。影响海水溶解氧浓度变化的主要因素是海水温度,溶解氧浓度随着温度的季节性变化而变化。夏季,水体分层会使溶解氧浓度发生大幅度的降低,大风过程对于溶解氧浓度也有一定的影响,通过打破夏季的季节性温跃层使水体发生垂向混合从而为海底提供氧气,但大风过程之后的几天会出现溶解氧浓度降低的现象。本次研究发现刘公岛海洋牧场在观测期间不存在低氧现象。     

南美洲鳗鲡(Anguilla rostrata)的耗氧率(ROC)、窒息点(AP)和适温范围(RT)及对非离子氨(NIA)、NO2-的LC50和SC的研究

为研究南美洲鳗鲡(Anguillarostrata)的耗氧率及其对水温、低溶氧、非离子氨和亚硝酸盐耐受性,本研究采用自制的鱼类呼吸装置测定其耗氧率和窒息点,以黑仔鳗为试验材料,探索其对水温、非离子氨、亚硝酸盐耐受性。结果表明,南美洲鳗鲡耗氧率存在昼夜变化,其昼间耗氧率为(86.46±37.77)mg/(kgh),夜间耗氧率为(123.58±22.56)mg/(kgh),二者存在显著性差异(P0.05);在15—30°C范围内,耗氧率随温度升高逐渐增大,耗氧率和水温的回归方程y=–0.1316x2+9.4507x–13.712(R2=0.9993);南美洲鳗鲡的耗氧率随体质量增大而降低,耗氧量随体质量增加而增大,耗氧量和体重的回归方程为y=0.2321x0.8334(R2=0.9979);在水温25°C时其窒息点随鱼体质量的增大而降低,均重10g、40g和160g的鳗鲡窒息点溶解氧浓度分别为(0.98±0.25)、(0.46±0.06)和(0.32±0.02)mg/L;13—29°C为南美洲鳗鲡的适温范围,25—29°C为其生长适宜水温,在一定范围内的短时低水温或高水温环境对其损伤是可逆的;水中非离子氨对南美洲鳗鲡的LC50和SC分别为12.22mg/L和1.22mg/L,亚硝酸盐氮对南美洲鳗鲡的LC50和SC分别为61.68mg/L和6.17mg/L。     

The bivalve Lembulus bicuspidatus may enhance denitrification in shelf sediment at the Angola–Benguela Frontal Zone

We collected living individuals of the bivalve Lembulus bicuspidatus, which shows an unusual preference for the oxygen-deficient habitat found at the Angola–Benguela Frontal Zone of the southeastern Atlantic. With a series of incubation experiments with ¹⁵N-labelled nitrate as a tracer in combination with membrane-inlet mass spectrometry, we studied the potential contribution of L. bicuspidatus to nitrate reduction in the upper sediment layer. Our preliminary results suggest that L. bicuspidatus enhances nitrate reduction if the oxygen concentration is sufficiently low. The Lembulus-mediated nitrate reduction rate is then similar to the rate of microbial nitrate reduction in the surrounding sediment.     

不同盐度对文蛤(Meretrix meretrix)呼吸代谢及体内酶活性的影响

为研究不同盐度对文蛤呼吸代谢的影响,本实验设置5个盐度(‰)梯度(11、18、25、32、39),检测不同盐度对文蛤(Meretrixmeretrix)耗氧和排氨的影响,以及文蛤的外套膜、鳃、肝胰腺三种组织中乳酸脱氢酶和Na+/K+-ATP酶活性的变化。结果表明:随着盐度的不断升高,文蛤耗氧率先升后降再升,在盐度18时达到最大值;排氨率先升后降,在盐度32时达到最大值。随着盐度不断升高和胁迫时间延长,文蛤的肝胰腺中乳酸脱氢酶活力总体呈先升高后下降再升高的趋势(P0.05),酶活力在盐度39时为最高;随着盐度不断升高和胁迫时间延长,文蛤的外套膜中Na+/K+-ATP酶活力总体呈先下降再升高后下降的趋势(P0.05),在盐度32时为最高;文蛤的外套膜和鳃中乳酸脱氢酶活力以及鳃和肝胰腺中Na+/K+-ATP酶活力受盐度影响不显著(P0.05),酶活力变化也多呈现"W"形的变化趋势。研究结果为文蛤的人工养殖提供参考。     

威海市褚岛北部海域CDOM和COD分布特征遥感分析

根据2017年7月和9月在山东威海褚岛北部海域现场测量的COD_(Mn)(Chemical oxygen demand)值和水体表观光学量,结合COMS(Communication,OceanMeteorological Satellite)上搭载的传感器GOCI(Geostationary Ocean Color Imager)所提供的有色可溶性有机物(Chromophoric dissolved organic matter,CDOM)产品,利用星地同步观测数据对现有的基于遥感反射比反演CDOM的模式进行验证,确定适合该海域的CDOM浓度遥感反演模式;通过对测试海域化学需氧量与遥感反演的水体CDOM浓度相关性分析,建立利用CDOM反演COD_(Mn)的遥感模式,并将该模式应用于测试海域LANDSAT 8/OLI(Operational Land Imager)遥感图像上,获取该海域COD_(Mn)浓度专题图,基于这些专题图分析了测试海域COD_(Mn)时空分布特征。结果表明:(1)基于GOCI产品的CDOM浓度值随时间和站点动态变化大,离岸越近数值越高,同一地点水体前后相差近1 h的数值变化也较大;(2)基于LANDSAT 8/OLI遥感数据反演的COD_(Mn)浓度时间动态变化大,总体来看褚岛附近水体的COD_(Mn)含量相对较低,褚岛以北海域水体COD_(Mn)含量有所增加,褚岛西侧水体的COD_(Mn)含量较东侧水体COD_(Mn)含量来说整体偏高。     

Authigenic carbonates from the eastern Black Sea as an archive for shallow gas hydrate dynamics – Results from the combination of CT imaging with mineralogical and stable isotope analyses

Authigenic carbonates associated with cold seeps provide valuable archives of changes in the long-term seepage activity. To investigate the role of shallow-buried hydrates on the seepage strength and fluid composition we analysed methane-derived carbonate precipitates from a high-flux hydrocarbon seepage area (“Batumi seep area”) located on the south-eastern Black Sea slope in ca. 850 m. In a novel approach, we combined computerized X-ray tomography (CT) with mineralogical and isotope geochemical methods to get additional insights into the three-dimensional internal structure of the carbonate build-ups.     

Pacific coral oxygen isotope and the tropospheric temperature gradient over the Asian monsoon region: a tool to reconstruct past Indian summer monsoon rainfall

Having recognized that it is the tropospheric temperature (TT) gradient rather than the land–ocean surface temperature gradient that drives the Indian monsoon, a new mechanism of El Niño/Southern Oscillation (ENSO) monsoon teleconnection has been unveiled in which the ENSO influences the Indian monsoon by modifying the TT gradient over the region. Here we show that equatorial Pacific coralline oxygen isotopes reflect TT gradient variability over the Indian monsoon region and are strongly correlated to monsoon precipitation as well as to the length of the rainy season. Using these relationships we have been able to reconstruct past Indian monsoon rainfall variability of the first half of the 20th century in agreement with the instrumental record. Additionally, an older coral oxygen isotope record has been used to reconstruct seasonally resolved summer monsoon rainfall variability of the latter half of the 17th century, indicating that the average annual rainfall during this period was similar to that during the 20th century. Copyright © 2011 John Wiley & Sons, Ltd.     

Hydrodynamic and isotopic investigations for evaluating the mechanisms and amount of groundwater seepage through a rockslide dam

This study addresses the influence of landslide dams on surface water drainage and groundwater flow. In the study area of Scanno Lake and Sagittario River (Central Italy), a limestone rockslide‐avalanche formed a lake, which has an outlet that is occasionally active, showing infiltration into the rockslide dam. Several springs are present at the lake's base and are partly fed by seepage through the rockslide debris. Piezometric surveys, discharge measurements, pumping tests and chemical analyses are tools used to build a conceptual model of the groundwater flow and to evaluate the flow through the rockslide debris. Seasonal water isotopic signatures validate the assumed model, showing a mixing of infiltration recharge and groundwater seepage throughout the rockslide debris. Various recharge areas have been found for springs, pointing out those directly fed by the rockslide debris aquifer. Hypotheses about seasonal groundwater mixing between the regional carbonate aquifer and the rockslide debris aquifer are supported by isotope results. Seasonal changes in groundwater table level due to recharge and surface losses from seasonal outlet have been correlated with isotopic groundwater composition from the rockslide debris aquifer and the downstream springs; this relationship highlights the role of the rockslide dam body on the hydrodynamics of the studied area. Relationships between surface waters and groundwater in the area have been completely understood on the basis of water isotopic fingerprinting, finally obtaining a complete evaluation of groundwater renewable resources and its regimen. Copyright © 2010 John Wiley & Sons, Ltd.     

Estimation of source water to cedar elm in a central Texas riparian ecosystem

A riparian ecosystem downstream of a small dam in central Texas was instrumented for sap flow, soil moisture content, and stream level from 2001. Stable isotopes in water (D and ¹⁸O) were analysed from rainfall, stream, lake, and cored sapwood cellulose from cedar elm (Ulmus crassifolia). The isotope signature of water source to cedar elm was identified by back calculation starting with the water isotopes in cellulose, and accounting for leaf‐water evaporation and biological fractionation during cellulose synthesis. The estimated mean isotope of the source water to cedar elm was enriched above rainfall in similarity to stream water during 2002. Flow paths that may have contributed to estimated variability from regional base flow and recharge water were identified using the variably saturated HYDRUS‐2D model. Copyright © 2004 John Wiley & Sons, Ltd.     

Fractal analysis of long-range paleoclimatic data: Oxygen isotope record of pacific core V28-239

R/S analysis of the oxygen isotope curve of Pacific core V28-239 yields a fractal dimension of 1.22. This value is considered to characterize global climatic change over the last 2 million years as expressed by changing O¹⁸ ratios and confirms that climatic variations are characterized by long-term persistence. The fractal dimension of 1.22 compares favorably with the approximate fractal dimension of 1.26 for annual precipitation records for nine major cities in the United States. Although the precipitation and oxygen isotope data are measured in different physical units and recorded at different time scales, fractal analysis allows for a mathematical comparison of the two phenomena. Additionally, since the fractal dimensions of the oxygen isotope and precipitation records are similar, it is implied that such fractal dimensions are characteristic of climate change over the spectral range of 10 to 10⁶ years. Given this temperature curves based on fractal parameters of long-term O¹⁸ data could be constructed which would allow examination of characteristics of temperature variation over tens and hundreds of years. Such studies may allow the establishment of limits on natural temperature variation and document the persistence of temperature trends through time. If these trends and limits can be resolved, long-range climatic prediction is feasible.