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1.
Spatial variations in the distribution and fluxes of dissolved oxygen and sulfide in bottom sediments of Omega and Sevastopol bays have been studied. The results of analysis reveal that the distribution of dissolved oxygen and sulfide in pore water depends mostly on seasonal variations in the oxygen concentration in bottom water, grain size, the organic carbon content in bottom sediments, and, additionally for Sevastopol Bay, the iron content. The oxygen flux at the bottom of Sevastopol Bay is 20 times larger in winter–spring compared to that of Omega Bay. Anaerobic conditions in Sevastopol Bay sediments are observed much closer to the surface, with their subsequent development in bottom water.  相似文献   

2.
Two different cold waters were found under the surface mixed layer in Tsushima Straits and the southwestern Japan Sea in autumn 2004. One is cold saline water with a low concentration of dissolved oxygen, and the other is cold less saline water with a high concentration of dissolved oxygen. The older saline water originates from the bottom of the East China Sea, strongly influenced by the Kuroshio water with high salinity. The bottom density in the eastern channel of the Tsushima Straits is coincident with that of the East China Sea in autumn, corresponding to the season when the cold saline water was frequently found in the Tsushima Straits. The newer less saline water originates from the front of Tsushima Warm Current between the Tsushima Warm Current water and the surface cold water in the Japan Sea. This water is formed by subduction above the isopycnal surface from the front of the Tsushima Warm Current.  相似文献   

3.
基于2020年夏季的大面航次观测数据,分析了烟台—威海北部海洋牧场及邻近海域海水溶解氧浓度垂向分布最小值（氧最小值层）的空间分布特征,并探讨了影响因素。从6月至8月,海水溶解氧浓度不断减小,垂向结构亦存在显著变化。海水溶解氧浓度垂向分布的最小值主要集中于7月的近岸海域,最小值大致从外海向近岸方向减小,其距离海底高度及与底层溶解氧浓度之差的绝对值均于双岛湾邻近海域为最大。海水溶解氧浓度垂向分布的最小值位于最强密度层结以下。但是海水溶解氧浓度垂向分布最小值的强度向北减小,而密度层结向北增大,两者的空间分布基本相反,说明密度层结抑制垂向湍流扩散可极大减少深层海水溶解氧的来源,是海水溶解氧浓度垂向分布最小值形成的必要条件,但不是主导因素。在海水溶解氧浓度垂向分布的最小值层,表观耗氧量存在垂向分布的最大值,大部分站点的pH存在垂向分布的最小值,说明局地增强、持续的生物地球化学耗氧是控制海水溶解氧浓度垂向分布最小值形成和空间分布的一个重要过程。研究结果表明氧最小值层是夏季烟台—威海北部近岸海水溶解氧垂向结构的典型特征之一。  相似文献   

4.
利用海底有缆在线观测系统获得的连续实时观测数据，研究了2016年6月2日至10月22日期间威海市西港海洋牧场底层海水溶解氧浓度的时间变化特征，并探讨了其影响机制。结果表明，观测期间底层海水溶解氧浓度整体呈先减小后增大的变化趋势，其变化范围为2.99 mg/L至11.43 mg/L，均值约为6.65 mg/L。进一步分析表明：（1）底层海水饱和溶解氧浓度的变化并不显著，于6月出现过饱和现象；（2）海水温度是底层海水溶解氧浓度日际变化和月变化的主要影响因素；（3）7月至8月中旬，在季节性温跃层抑制垂向混合和水温升高的共同影响下，底层溶解氧浓度总体呈下降趋势；（4）日平均风速与日平均海水溶解氧浓度的相关性并不显著，但大风期间底层海水溶解氧浓度存在先升高后降低的变化特征；（5）底层海水溶解氧浓度的日变化以全日周期为主，可能主要受生物过程、垂向混合扩散和潮流输运等日变化的影响。本研究对于进一步探讨山东半岛海洋牧场区域海水溶解氧的时空分布特征及其影响机制具有重要意义。  相似文献   

5.
山东半岛沿岸海域陆海相互作用强烈,有着复杂水动力环境的同时也是我国重要的渔业资源区和水产养殖区,针对其DO时空变化特征及影响机制的研究具有重要意义。本文基于2015—2017年期间的监测数据,研究了山东半岛东部近海海水溶解氧的时空变化特征,并结合实测的温度、盐度、pH数据探究其影响机制。结果表明：表、底层溶解氧的空间分布形态基本一致,水平上呈现出北高南低、外海高近岸低、湾内低于湾外的块状分布特点,垂向上表层高于底层。在监测期间内,溶解氧的季节变化规律为春季最高,夏季最低,具体表现为3月>5月>10月>8月,乳山湾等海湾处的季节波动较大;表底层溶解氧的年际变化略有不同,但均趋于稳定,靖海湾和五垒岛湾近海溶解氧的年际变化显著。表观耗氧量在整个研究阶段的均值为–0.33 mg/L,呈现出基本平衡状态,但乳山湾沿岸海域受到陆源输入有机物的显著影响,贫氧状况频发。监测期间,溶解氧与海水温度呈显著负相关,两者相关系数高达–0.95,其中成山头至石岛海域的溶解氧浓度高值区与当地的低温海水相对应;盐度对溶解氧的影响则相对较弱;有机污染物的聚集常造成乳山湾近岸海域的pH异常,其大量耗氧是导致当地为溶解氧浓度低值区的重要原因。  相似文献   

6.
Seasonal changes in the dissolved oxygen (DO) content in water were analyzed based on long-term observations (2006–2013) in the Eastern Bosporus Strait (Peter the Great Bay, Sea of Japan). It was found that the monthly average DO concentrations at the bottom of the strait were significantly lower in summer than the average annual long-term data. The minimum DO contents were recorded during four months, from July to October. It was shown that the DO content in water depended on changes in current directions in the strait: lower DO contents resulted from hypoxic water inflow, mostly from Amur Bay.  相似文献   

7.
High precision total CO2 (TCO2) data are presented from the NW Weddell Sea obtained during two cruises which were 3 years apart. A TCO2 increase from 1993 to 1996 was observed in the newly formed bottom water, whereas no TCO2 increase was found in the surrounding water masses. Accompanying this TCO2 increase in the bottom water was an oxygen decrease. Obviously, bottom water with variable characteristics is produced along the margins of the Weddell Sea. Examination of possible causes leads to the conclusion that the bottom water variability is largely due to varying amounts of Warm Deep Water intruding onto the shelves of the Weddell Sea, thus changing the shelf water end-member of bottom water formation. Analysis of the data, using the observed differences of oxygen to perform a correction, suggested that some part of the TCO2 increase of the bottom water is due to the increased level of anthropogenic CO2. The TCO2 increase of the bottom water is commensurate to a tentative annual increase of about 1 μmol kg−1 in the surface water source of this bottom water. This would agree fairly well with the increase of the partial pressure of CO2 in the atmosphere.  相似文献   

8.
乳山湾邻近海域低氧现象及成因浅析   总被引：1，自引：0，他引：1  
根据2009-06-2009-09及2010-05-2010-06在乳山湾及其毗邻海域的综合调查,分析了该海域溶解氧的变化,初步探讨了影响溶解氧变化及底层低氧形成的原因。结果表明,夏季乳山湾邻近海域存在季节性低溶解氧区,溶解氧在6,7月份相对较高,而在8,9月份相对较低,最低值出现在8月份,为3.21mg/L(饱和度为35.5%),表观耗氧量为5.82mg/L。乳山湾外邻近水域溶解氧略高于湾口和湾内。底层溶解氧水平受到潮汐的影响,具有较大的周日波动性,变化范围介于3.74～8.26mg/L;在落潮时质量浓度降低而在涨潮时质量浓度升高。在这一区域存在较为强烈的温、盐跃层,从而限制了表、底层溶解氧的交换,而COD质量浓度的升高为这一区域的耗氧过程提供了一定的物质基础。潮汐、黄海冷水团的顶托作用、有机物质在底层水域的氧化作用以及底泥耗氧过程导致底层溶解氧的亏损。  相似文献   

9.
Data are presented on the content and composition of hydrocarbons (HC) (aliphatic, AHC and polyaromatic, PAH) in the filtered particulate matter and in the surface layer of the bottom sediments on the northern shelf of the Caspian Sea and related to the data on their content in the Volga River estuary. Because of the transformation and precipitation of anthropogenic and natural compounds, the HC composition in the particulate matter and bottom sediments undergoes transformations caused by the mixing of fresh and saline waters (in the bottom sediments, within the concentration ranges 70.4–4557.9 μ g/g for AHC and 3.8–4800 ng/g for PAH). It was found that the greatest concentrating of HC proceeds in the region of the avalanche sedimentation, and their content is independent of the grain-size type of the sediments. The anthropogenic HC (oil and pyrogenous) do not get over the marginal filter of the Volga River and do not pass to the open part of the sea.  相似文献   

10.
Vertical variability in the bio-optical properties of seawater in the northern South China Sea(NSCS) including inherent optical properties(IOPs) and chlorophyll a concentration(Chl) were studied on the basis of in situ data collected in summer 2008 using an absorption/attenuation spectrophotometer. An empirical model was developed to estimate Chl profiles based on the absorption line height at long wavelengths, with a relative root mean square error of 37.03%. Bio-optical properties exhibited large horizontal and vertical spatial variability. As influenced by coastal upwelling and the Zhujiang River(Pearl River) discharge, both IOPs and Chl exhibited high values in the surface waters of the inner shelf, which tended to decrease with distance offshore. Subsurface maximum layers of IOPs and Chl were observed in the middle and outer shelf regions, along with significantly higher values of attenuation coefficients beneath this layer that rapidly increased towards the bottom. In the open ocean, both IOPs and Chl exhibited consistent variability, with the subsurface maximum layer typically located at34–84 m. Phytoplankton were found to be one of the major components in determining the vertical variability of bio-optical properties, with their vertical dynamics influenced by both physical forcing and light attenuation effects. The depth of the subsurface maximum layer was found to be closely related to the fluctuation of the oceanic thermocline and the depth of the euphotic zone, which also affected the total integrated biomass of the upper ocean. Typically high values of attenuation coefficients observed in the bottom waters of the continental shelf reflected the transport of particulate matter over the bottom boundary layer. Our results reveal large spatial differences in bio-optical profiles in response to complex marine ecodynamics in the NSCS. From the perspective of marine research, high-resolution optical measurements are clearly advantageous over conventional bottle sampling.  相似文献   

11.
The concentration distribution was studied for dissolved oxygen, phosphorus forms, and particulate matter in Curonian Bay of the Baltic Sea in poorly known consolidated ice cover conditions during the winter seasons of 2010, 2011, and 2013. The surface and near-bottom waters were sampled at 51 stations. The ice cover exerts no significant effect on the typical seasonal variation of all considered parameters in the basin. The concentrations of mineral and organic phosphorus in the bay appeared to be lower by factors of 2–4 compared to summer values. A two- to threefold decrease in the concentrations of organic phosphorus since 2010 to 2011 and then to 2013 was recorded in the bay, which resulted from a decrease in phosphorus production by phytoplankton. Despite water being isolated from air by ice, the absence of wave mixing, and the decrease in oxygen production owing to the seasonal winter decrease in the intensity photosynthetic processes, no oxygen deficiency was found in the basin. This is because oxygen supplied to the bay by river runoff and production by photosynthesis in the bay exceed the utilization for oxidation of organic matter resulting from low bioproductivity of the waters during winter. The winter decrease in the fraction of biogenic particulate matter is seen as a four- to sevenfold drop in its total concentration in the waters compared to summer seasons. The absence of wave roiling of bottom sediments also caused a decrease in the secondary supply of biogenic particulate matter from sediments into near-bottom waters. No negative trends of geoecological conditions in the bay were revealed by the studied parameters under consolidated ice cover conditions.  相似文献   

12.
A. S. Kukushkin 《Oceanology》2013,53(5):554-569
The peculiarities in the distribution pattern of the concentration of suspended organic matter (SOM) components were studied for the long-term period of 1979–1995. We have analyzed their seasonal, annual, and interannual variability in the surface water layer and in the photosynthetic water layer in the northwestern Black Sea. Four areas pertaining to different concentrations of SOM components were defined according to the effect of riverine discharge and of open sea water masses, i.e. western, northern, central, and eastern areas. We have found an increase in the concentrations of SOM components in the summer-autumn period in the late 1980s and early 1990s, with the highest values observed in 1992. The concentration of suspended organic carbon was estimated for the concentration of Chlorophyll a in the surface water layer. These calculations are based on the regression relationship between simultaneous measurements of these two parameters in situ. It was found that the seasonal interannual variability in the concentrations of SOM components was affected by the volume of riverine discharge, its run to the sea, and climatic shifts.  相似文献   

13.
A. S. Kukushkin 《Oceanology》2014,54(5):606-617
The peculiarities of the distribution of the components of the suspended organic matter (SOM) and their interannual and seasonal variability have been analysed in the surface water layer and photic water layer of the Black Sea (the deep-sea areas) for the period of 1978–1995. The statistical assessment of the seasonal and monthly dynamics of the SOM components and their ratios was performed. The seasonal dynamics of the concentration of particulate organic carbon have been calculated based on the data on the Chlorophyll “a” (Chl “a”) concentration in the surface water layer based on the regression relationship between these two parameters measured in situ simultaneously. Taking these relationships into account, the interannual dynamics of the Chl “a” concentration have been analysed for the period of 1978–2010. It was found that the concentrations of the SOM components increased significantly in the 1980’s and early 1990’s with the maximum reached in the summer of 1992. It was also found that the seasonal interannual dynamics of the components of the SOM were mainly preconditioned by the interannual dynamics of the phytoplankton biomass, which, in turn, depended on the climatic conditions.  相似文献   

14.
Nearshore suspended sediment concentration along the muddy Surinam coast is highly variable; maximum values are many times greater than on other muddy coasts. Water samples taken at four field stations during various stages of the tide range in concentration from 15 to 3,700 mg/l near the surface and from 100 to 30,000 mg/l near the bottom. Highest overall concentrations and greatest variability in concentration occur in water over large banks of fluid mud (thixotropic gel) that extend 2–3 km offshore and 5–10 km along-shore. On both the intertidal and subaqueous portions of these mudbanks highest concentrations are found at low tide. Results provide evidence that an exchange between fluid mud and suspended sediment takes place during each tidal cycle.  相似文献   

15.
An 18-year monitoring record (1978-1995) of dissolved oxygen within a region having hypoxia (dissolved oxygen less than 2 mgl(-1)) in the bottom layer was examined to describe seasonal and annual trends. The monitoring location was near or within a well-described summer hypoxic zone whose size has been up to 20,000 km(2). The monitoring data were used to hindcast the size of the hypoxic zone for before consistent shelfwide surveys started, and to predict it for 1989, when a complete shelfwide survey was not made. The concentration of total Kjeldahl nitrogen (TKN) in surface waters and concentration of bottom water oxygen were directly related, as anticipated if organic loading from surface to bottom was from in situ processes. The TKN data were used to develop a predictive relationship that suggested there was no substantial hypoxia before the 1970s, which was before nitrate flux from the Mississippi River to the Gulf of Mexico began to rise. The peak frequency in monthly hypoxic events is two to three months after both the spring maximum in discharge and nitrate loading of the Mississippi River. These results support the conclusion that persistent, large-sized summer hypoxia is a recently-developed phenomenon that began in the 1970s or early 1980s.  相似文献   

16.
This publication considers the probing data on aquatic anomalies (hydrothermal plumes) in the areas of 26° and 29° N of the Mid-Atlantic Ridge (MAR). The mass of the hydrothermal iron supply and the intensity of the iron sedimentation onto the bottom were estimated by means of sediment traps. It was found that the plume of the TAG hydrothermal vent 6 km3 in volume contained about 67 t of suspended Fe; the plume of the Broken Spur field (up to 8.24 km3 in volume) contained 23.5 t or less because of the lower concentration. The data on the sedimentary matter fluxes showed that 0.3–0.5% of the hydrothermal iron was precipitated immediately from a plume of neutral buoyancy onto the bottom; the bulk of the iron was dissipated into the environment. From the dimensions of the plumes, the flow dynamics, the iron concentrations in the plumes, and the amounts of iron supplied by hydrothermal vents, it was found that the resident time of the plumes considered was from 5 to 10 days.  相似文献   

17.
通过对2011年北部湾北部海域春季和夏季溶解氧（DO）及其他环境要素进行分析讨论，发现DO的季节性差异较大，春季DO含量（平均8.11 mg/L）明显高于夏季（平均6.05 mg/L）。夏季北部湾底层部分区域存在DO低值，该低值区常年存在，并且DO最低值逐渐降低、低值区范围逐渐扩大。利用相关性分析和灰色关联度分析的方法，对夏季底层DO低值的成因进行分析发现：夏季底层水体浮游植物产氧作用较弱，海水层化作用强，阻碍了表底层DO的交换；另外底层有机质分解的耗氧作用明显，出现了氧气的净消耗，由此导致夏季底层水体出现DO的低值。同时，由于2011年之后北部湾北部海域陆源污染排放和赤潮的频发使得该海域低氧状况加剧，潜在低氧区逐渐发展为低氧区。  相似文献   

18.
Potential spawning habitat is defined as the area where environmental conditions are suitable for spawning to occur. Spawning adult data from the first quarter (January–March) of the International Bottom Trawl Survey have been used to study the inter-annual variability of the potential spawning habitat of North Sea plaice from 1980 to 2007. Generalised additive models (GAM) were used to create a model that related five environmental variables (depth, bottom temperature and salinity, seabed stress and sediment type) to presence–absence and abundance of spawning adults. Then, the habitat model was applied each year from 1970 to 2007 to predict inter-annual variability of the potential spawning habitat. Predicted responses obtained by GAM for each year were mapped using kriging. A hierarchical classification associated with a correspondence analysis was performed to cluster spawning suitable areas and to determine how they evolved across years. The potential spawning habitat was consistent with historical spawning ground locations described in the literature from eggs surveys. It was also found that the potential spawning habitat varied across years. Suitable areas were located in the southern part of the North Sea and along the eastern coast of England and Scotland in the eighties; they expanded further north from the nineties. Annual survey distributions did not show such northward expansion and remained located in the southern North Sea. This suggests that this species' actual spatial distribution remains stable against changing environmental conditions, and that the potential spawning habitat is not fully occupied. Changes in environmental conditions appear to remain within plaice environmental ranges, meaning that other factors may control the spatial distribution of plaice spawning habitat.  相似文献   

19.
The spatial and temporal variability of the chlorophyll (Chl) concentration in the surface water layer of the Black Sea in 1998–2008 has been analyzed using the data obtained by the SeaWiFS satellite sensor. In the deep-sea areas, the seasonal pattern of the Chl concentration is represented by a U-shape curve. The maximal concentrations are observed in the winter-spring and autumn periods, while the minimal, in the summertime. In the northwestern Black Sea, the maximal concentrations are registered in mostly the summer and autumn periods. Pronounced interannual variability is found for the summer concentrations of Chl observed for an 11-year period. After a cold winter, the concentration of Chl in the spring period is 3–5 times higher compared to the mild-winter years. In December–March, a negative correlation between the water temperature and the average Chl concentration is registered.  相似文献   

20.
The transport of Japan Basin Bottom Water (JBBW) into the Yamato Basin in the Japan Sea is an important boundary condition for the modification of the abyssal water mass in the Yamato Basin. To estimate the volume transport of JBBW, two year-long observations (October 2011–October 2012 and May 2014–May 2015) were carried out using current meters moored in the deep channel connecting the Japan Basin with the Yamato Basin. The mean transport toward the Yamato Basin from the Japan Basin was estimated to be 7.37 × 104 and 5.15 × 104 m3 s?1, consistent with previous estimates from box model analysis and lowered acoustic Doppler current profiler observations. The time series of JBBW transport showed significant variability. A cause of the variability was bottom-intensified flow fluctuations in the 3- to 15-day period band, which suggests bottom-trapped topographic Rossby waves in the deep channel. In addition, during August–October 2014, notable variation of JBBW transport accompanied significant decreases of potential temperature and dissolved oxygen concentration. Detailed examination of the episodic variations of flows, potential temperature, and dissolved oxygen concentration, together with consideration of sea surface height variations, suggested that rapid northward meandering of the surface subarctic front was another cause of the significant variation in JBBW transport.  相似文献   

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