Hydrographical characteristics and oxygen isotopic signatures of water in a coastal environment (Mangalore) along the southeastern Arabian Sea

Coastal marine environments are important links between the continents and the open ocean. The coast off Mangalore forms part of the upwelling zone along the southeastern Arabian Sea. The temperature, salinity, density, dissolved oxygen and stable oxygen isotope ratio (δ¹⁸O) of surface waters as well as those of bottom waters off coastal Mangalore were studied every month from October 2010 to May 2011. The coastal waters were stratified in October and November due to precipitation and runoff. The region was characterised by upwelled bottom waters in October, whereas the region exhibited a temperature inversion in November. The surface and bottom waters presented almost uniform properties from December until April. The coastal waters were observed to be most dense in January and May. Comparatively cold and poorly oxygenated bottom waters during the May sampling indicated the onset of upwelling along the region. δ¹⁸O of the coastal waters successfully documented the observed variations in the hydrographical characteristics of the Mangalore coast during the monthly sampling period. We also noted that the monthly variability in the properties of the coastal waters of Mangalore was related to the hydrographical characteristics of the adjacent open ocean inferred from satellite-derived surface winds, sea surface height anomaly data and sea surface temperatures.     

Sources and distribution of fresh water in the East Greenland Current

Fresh water flowing from the Arctic Ocean via the East Greenland Current influences deep water formation in the Nordic Seas as well as the salinity of the surface and deep waters flowing from there. This fresh water has three sources: Pacific water (relatively fresh cf. Atlantic water), river runoff, and sea ice meltwater. To determine the relative amounts of the three sources of fresh water, in May 2002 we collected water samples across the East Greenland Current in sections from 81.5°N to the Irminger Sea south of Denmark Strait. We used nitrate-phosphate relationships to distinguish Pacific waters from Atlantic waters, salinity to obtain the sum of sea ice melt water and river runoff water, and total alkalinity to distinguish the latter. River runoff contributed the largest part of the total fresh water component, in some regions with some inventories exceeding 12 m. Pacific fresh water (Pacific source water S ∼ 32 cf. Atlantic source water S ∼ 34.9) typically provided about 1/3 of the river runoff contribution. Sea ice meltwater was very nearly non-existent in the surface waters of all sections, likely at least in part as a result of the samples being collected before the onset of the melt season. The fresh water from the Arctic Ocean was strongly confined to near the Greenland coast. We thus conjecture that the main source of fresh water from the Arctic Ocean most strongly impacting deep convection in the Nordic Seas would be sea ice as opposed to fresh water in the liquid phase, i.e., river runoff, Pacific fresh water, and sea ice meltwater.     

Simulation of the Circulation and Space Structure of Thermohaline Fields in the Sevastopol Bay with Regard for the Actual External Data (Winter, 1997)

We discuss the results of the numerical experiment aimed at the simulation of the behavior of currents and transformations of the temperature and salt modes in the Sevastopol Bay in January–February 1997. In the numerical analysis, we use actual data on the velocity and direction of the wind, sea surface temperature, and the discharge of River Chernaya. It is shown that the circulation and structure of hydrological fields are mainly connected with the direction of the wind, its intensity, and variability in the course of time. Since the analyzed water area is shallow, the currents inside the bay undergo rapid transformations (less than for an hour after changes in the wind). At the same time, the transformations of the thermohaline fields are slower. Due to the inflow of fresh waters of River Chernaya and salt waters from the open sea through the strait, the structure of thermohaline fields formed in the bay is nonuniform (both in the vertical and horizontal directions). The distribution of salinity plays the main role in the formation of the vertical stratification, which is natural for the winter season. Due to the process of freshening of water, a quite high vertical salinity gradient is formed in the upper layer of the sea. As a result, the process of cooling does not lead to the appearance of convection and inversions of temperature are formed in the case where warmer waters are located in the bottom layers. __________ Translated from Morskoi Gidrofizicheskii Zhurnal, No. 2, pp. 60–76, March–April, 2005.     

中沙群岛海域春夏交季温盐分布特征

中沙群岛主要由中沙大环礁和黄岩岛组成,其温盐分布对于本区渔业生产、航海保障和水下通讯等具有重要意义。尤其是春夏之交的季节转换时期,该海域水温和盐度及其相应的跃层特性存在显著的季节变化,掌握其季节变化特征具有重要现实意义。本文基于2019年5月（南海春夏季风转换期）中沙大环礁、黄岩岛和2020年6月（夏季风爆发期）中沙大环礁海域大面站调查数据分析,发现中沙大环礁海域水温和盐度分布特征在夏季风爆发前后具有显著的差异性,2个航次的温跃层分布也呈现出较大不同,2019年5月黄岩岛海域温盐中上层分布与中沙大环礁相似,但底层有所差异,跃层深度也较大。2020年6月中沙大环礁内水体升温较快,各层水温均高于2019年5月,其中以底层水体升温最为显著;2019年5月中沙大环礁内水温水平梯度较大,且随着水深加大水平梯度也越大,2020年6日水平温度梯度逐渐减小。2个航次的盐度分布与水温分布较为相似。结合调查时段的海表热通量变化和卫星高度计资料分析认为,2019年5月中沙大环礁西南部海洋吸热高于东北部,故表层水温西南高东北低;2020年6月至7月环礁西南部海洋吸热低于东北部,故表层水温西南低东北高。由于中尺度涡的作用,中沙大环礁区域局部产生低温高盐或高温低盐水,并导致2020年6月中沙大环礁大部分海域的温跃层加深。     

Submarine springs of fresh water in the region from Cape Feolent to Cape Sarych

We performed a search for local coastal submarine springs of fresh water in the region from Cape Feolent to Cape Sarych (down to an isobath of 40m). Stable submarine springs of brackish water with the minimum salinity of 5.5‰ and the minimum total output of 30,000 m³/day were discovered only near the west wall of Cape Aiya. It is shown that brackish waters discharging from these springs spread over the sea surface in the form of a thin layer (up to 1 m in thickness) characterized by lower salinity, higher transparency, and an elevated content of silicic acid. We make a conjecture that the appearance of 2–3-m-thick layers of water with higher transparency and lower salinity at depths of 5–8 m is explained by the discharge of unknown bottom springs of underground fresh water. Translated by Peter V. Malyshev and Dmitry V. Malyshev     

山东半岛东部近海海水溶解氧时空变化

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。     

长江口及其邻近海区环流和温、盐结构动力学研究IV 盐度结构

盐度的数值模拟结果表明: 一年四季长江口及其邻近海区的盐度分布均为近岸低, 外海高,近岸与外海盐差大。冬季近岸和外海的上层盐度呈垂直均匀分布, 陡坡及外海的底层出现层化; 近岸特别是长江口及其以南近岸盐度的水平变化显著, 外海变化缓慢。春季在长江口以北, 近岸至外海的表层至近底层盐度呈垂直均匀分布, 近岸至外海的底层存在一个向北延伸的盐舌; 长江口及其以南近岸和外海的表层至次表层盐度呈垂直均匀分布, 在近岸稍远的表层至次表层形成盐跃层, 其强度自近岸至外海和自表层至底层逐渐减弱; 在陡坡区的底层盐度几乎呈均匀分布, 并保持高盐特征。夏季除长江口及其以南近岸浅水区盐度呈垂直均匀分布外, 其它区域盐度均出现剧烈分层, 在长江冲淡水区形成强盐跃层, 其强度自表层至底层迅速减弱, 陡坡至外海的底层盐度大致呈均匀分布且保持高盐特征。秋季长江口以北近岸浅水区表层盐度低且出现层化, 表层以下盐度高且呈垂直均匀分布; 近岸以远自表层至底层呈垂直均匀分布, 在外海上层盐度低且呈垂直均匀分布, 而底层盐度高并出现分层;长江口及其以南近岸浅水区盐度呈垂直均匀分布, 陡坡区出现层化, 其盐度为表层低, 底层高; 层化自表层至底层逐渐增强, 并随陡坡至外海的减弱, 上层又逐渐变为垂直均匀分布。     

2012年春季渤海中部及邻近海域叶绿素a与环境因子的分布特征

分析了2012年春季渤海中部及其邻近海域32个站点叶绿素a和环境因子的空间分布特征及其相互关系。结果发现:渤海中部靠近黄河口邻近水域相对于其他水域,呈现出相对较高的水温和较低的盐度,这与黄河淡水输入以及近岸水深相对较浅有密切关系。营养盐浓度在空间分布上表现为黄河口附近海域较高,在垂直分布上表现为中、底层高于表层,显示出黄河水输入与沉积物营养盐再释放的影响;此外,营养盐浓度与结构显示,渤海海域存在明显的磷和硅限制,磷限制尤其严重。叶绿素a浓度的空间分布显示,表层叶绿素a浓度的高值区出现在渤海湾湾口处,而中层与底层的叶绿素a浓度高值区出现在渤海中部。主成分分析结果表明,磷酸盐和温度是影响表层叶绿素a浓度的重要因素,而中、底层叶绿素a浓度主要受磷酸盐的影响。     

Sensitivity of a global ocean model to increased run-off from Greenland

We study the reaction of a global ocean–sea ice model to an increase of fresh water input into the northern North Atlantic under different surface boundary conditions, ranging from simple restoring of surface salinity to the use of an energy balance model (EBM) for the atmosphere. The anomalous fresh water flux is distributed around Greenland, reflecting increased melting of the Greenland ice sheet and increasing fresh water export from the Arctic Ocean. Depending on the type of surface boundary condition, the large circulation reacts with a slow-down of overturning and gyre circulations. Restoring of the total or mean surface salinity prevents a large scale redistribution of the salinity field that is apparent under mixed boundary conditions and with the EBM. The control run under mixed boundary conditions exhibits large and unrealistic oscillations of the meridional overturning. Although the reaction to the fresh water flux anomaly is similar to the response with the EBM, mixed boundary conditions must thus be considered unreliable. With the EBM, the waters in the deep western boundary current initially become saltier and a new fresh water mass forms in the north-eastern North Atlantic in response to the fresh water flux anomaly around Greenland. After an accumulation period of several decades duration, this new North East Atlantic Intermediate Water spreads towards the western boundary and opens a new southward pathway at intermediate depths along the western boundary for the fresh waters of high northern latitudes.     

南中国海海水中多环芳烃的分布特征及源分析

利用气相色谱-质谱联用(GC-MS)技术,对2012年10月采自南中国34个站位的表层、500 m层、底层海水中的16种多环芳烃(16PAHs)进行了检测分析。结果显示:南中国海海水中16PAHs的含量相对于其他类似广阔水域较低,分布特征大致呈现500 m层表层底层。经特征PAHs组分分析判定南中国海海水中PAHs主要来源于石油及其产品。     

沿岸海区冬季垂直环流及其温盐结构的数值研究──Ⅱ.温盐结构

冬季沿岸海区温度和盐度的数值计算结果表明：温度在近岸近表层大致呈垂直均匀分布,外海近表层形成较强的温跃层,近岸至外海的下层保持冷水特征。表层和底层盐度高,中层盐度低,在中层形成自近岸伸向外海且盐度逐渐由低变高的低盐水舌,河口冲淡水区形成较强的盐跃层。随着自南往北海区水深的逐渐变浅、岸界坡度的由大变小和沿岸下降流的由强变弱,近岸温度和盐度的垂直分布越来越均匀,外海近表层的温跃层强度越来越弱。盐度自南至河口区逐渐由高变低,而自河口区至北逐渐由低变高。沿岸下降流使河流冲淡水区的益跃层变厚。     

Empirical tools for simulating salinity in the estuaries in Everglades National Park,Florida

Salinity in a shallow estuary is affected by upland freshwater inputs (surface runoff, stream/canal flows, groundwater), atmospheric processes (precipitation, evaporation), marine connectivity, and wind patterns. In Everglades National Park (ENP) in South Florida, the unique Everglades ecosystem exists as an interconnected system of fresh, brackish, and salt water marshes, mangroves, and open water. For this effort a coastal aquifer conceptual model of the Everglades hydrologic system was used with traditional correlation and regression hydrologic techniques to create a series of multiple linear regression (MLR) salinity models from observed hydrologic, marine, and weather data. The 37 ENP MLR salinity models cover most of the estuarine areas of ENP and produce daily salinity simulations that are capable of estimating 65–80% of the daily variability in salinity depending upon the model. The Root Mean Squared Error is typically about 2–4 salinity units, and there is little bias in the predictions. However, the absolute error of a model prediction in the nearshore embayments and the mangrove zone of Florida Bay may be relatively large for a particular daily simulation during the seasonal transitions. Comparisons show that the models group regionally by similar independent variables and salinity regimes. The MLR salinity models have approximately the same expected range of simulation accuracy and error as higher spatial resolution salinity models.     

黄河口及邻近水域小型鳀鲱鱼类数量分布及其与环境因子的关系

小型鳀鲱鱼类多为浮游生物食性种类;又是多种高营养层次鱼类的饵料生物;作为生态系统中的重要类群;其数量分布对多种生物均具有重要影响。本文根据2013年6月、8月、10月和2014年2月、4月、5月在黄河口及邻近水域进行的渔业资源和环境调查数据;分析了该海域小型鳀鲱鱼类资源数量分布特征;并用广义可加模型研究了其数量分布与时空和环境因子等之间的关系。黄河口及邻近水域小型鳀鲱鱼类相对资源量呈现明显的季节变化;夏、秋季相对资源量明显高于冬、春季。小型鳀鲱鱼类相对资源量具有明显的空间变化;且在不同月份呈现不同的空间分布格局;在4月、5月、6月小型鳀鲱鱼类主要分布于近岸水域;在8月、10月小型鳀鲱鱼类分布外移且范围扩大。GAM分析表明;影响黄河口及邻近水域小型鳀鲱鱼类相对资源量时空分布的主要环境因子包括表层盐度、表层水温、水深和浮游植物丰度等。小型鳀鲱鱼类相对资源量随表层盐度的升高呈现升高的趋势;在盐度达到30时;小型鳀鲱鱼类相对资源量处于最高水平。随表层水温的升高相对资源量有升高趋势;当表层水温达到15℃后;小型鳀鲱鱼类相对资源量增加趋势减缓且丰度较大。小型鳀鲱鱼类相对资源量随浮游植物丰度的增大总体呈现上升趋势;而随水深的变化呈现先降低后升高的趋势。黄河口及邻近水域小型鳀鲱鱼类相对资源量的时空变化与鳀鲱鱼类产卵、索饵和越冬洄游有关;受到季节变化、黄河径流变化以及黄河调水调沙等引起的海洋环境因子变动的影响。     

Analysis of thermohaline and current distribution characteristics of Zhejiang and Fujian waters in summer

This paper analyzed the distribution of thermohaline and circulation characteristics of Zhejiang and Fujian waters, based on the cross-sectional thermohaline data and on current data (up to 30 d duration) at fixed-point moorings, collected in the summer of 2006. We also performed low-pass filtering and spectrum analysis on the mooring submersible buoy data. Based on that analysis, we discussed the characteristics of low frequency currents and time-variations in these waters. The main conclusions are as follows. (1) There is a low salinity pinnate area near the Hangzhou Bay in summer, and outside the low salinity area, an obvious salinity front is present from surface to bottom near 123°E. There is also a temperature front below the surface at a corresponding position. (2) Bottom water of the Taiwan Warm Current comes from the subsurface of Kuroshio. (3) The direction of low frequency current at fixed anchor stations is N-NE or S, which mainly depends on the interaction of control currents in this waters. (4) Significant spectral peaks at all mooring stations are typically semidiurnal and diurnal tides. Semidiurnal tidal waves are the main ones in these waters, and have more energy closer to the shore. (5) Significant energy spectral peaks of middle period (3 to 8 d) of currents are responses to weather frequency. (6) Significant energy spectral peaks of long periods at the surface or bottom are probably responses to seasonal wind or bottom friction, while, the long period peaks of other depths can reflect cyclical changes of interactions between currents. We conclude that the pulsation period of the Taiwan Warm Current in these waters is 10-17 d.     

2008年夏季楚科奇陆架海域近底层水温大幅快速变化事件研究

2008年夏季中国第3次北极科学考察期间,利用锚碇潜标对北冰洋楚科奇陆架海域进行了为期33 d的海流剖面、近底层温度与盐度连续观测。观测数据显示楚科奇陆架海域近底层海水温度出现了两次较大幅度的快速升降现象。结合此次科学考察R断面温盐深仪(CTD)观测资料、以及卫星遥感海表温度(SST)和海表风场等资料,综合分析表明:观测到的这种快速升、降温现象不仅发生在近底层;这种快速升、降温现象应该是由海水温度锋面在夏季整体缓慢北移的同时存在短暂南北摆动所导致;温度锋面的季节性北移属于北极气候特征,而温度锋面短暂的南北摆动则与短期天气过程有关。     

东海沿岸海区垂直环流及其温盐结构动力过程研究Ⅱ．温盐结构

对于本研究采用的动力学模型及其垂直环流的模拟结果已在第Ⅰ部分论述。作者将对与垂直环流对应的温、盐结构进行分析。温度和盐度模拟结果表明：冬季东海沿岸海区的温、盐分布均为近岸低、外海高;近岸温、盐呈垂直均匀分布,在外海出现分层,其温度为表层高、底层低,而盐度却为表层和底层高,中层偏低,长江口以南的近表层以下形成自近岸伸向外海的弱低盐水舌;长江冲淡水区及长江口以北和其以南外海的近表层有温、盐跃层生成,深底层温、盐呈均匀分布,且保持低温高盐特征;随着海区自北往南纬度的降低,岸坡和水深的增大及沿岸下降流的增强,温度和盐度自近岸至外海的垂直均匀分布跨度逐渐变窄;外海近表层的温、盐跃层强度自北至长江口逐渐增强,而自长江口至南逐渐减弱,其位置自北往南逐渐上移;冬季沿岸下降流使长江冲淡水区的盐跃层变厚。夏季海区的温度分布为近岸和外海高,近岸稍远出现冷水涌升,垂向上呈现显著分层,盐度分布为近岸低、外海高;长江冲淡水区及杭州湾以南外海的次表层存在温、盐跃层,其跃层以上出现混合层,且保持高温低盐特征,跃层以下温、盐大致呈均匀分布,并保持低温高盐特征;随着海区自南往北纬度的增高、岸坡和水深的减小及沿岸上升流自南至长江口和自长江口至北的增强和继而减弱,长江冲淡水区的温、盐跃层强度自南至长江口逐渐增强,而自长江口至北逐渐减弱,外海次表层的温、盐跃层强度却自南至长江口逐渐减弱,自长江口至北又逐渐增强,其温、盐跃层的位置自南往北逐渐上移;夏季沿岸上升流使长江冲淡水区的盐跃层变薄。     

Elucidating the dynamics and mixing agents of a shallow fjord through age tracer modelling

The mixing agents and their role in the dynamics of a shallow fjord are elucidated through an Eulerian implementation of artificial tracers in a three-dimensional hydrodynamic model. The time scales of vertical mixing in this shallow estuary are short, and the artificial tracers are utilized in order to reveal information not detectable in the temperature or salinity fields. The fjord's response to external forcing is investigated through a series of model experiments in which we quantify vertical mixing, transport time scales of fresh water runoff and estuarine circulation in relation to external forcing.Using age tracers released at surface and bottom, we quantify the time scales of downward mixing of surface water and upward mixing of bottom water. Wind is shown to be the major agent for vertical mixing at nearly all depth levels in the fjord, whereas the tide or external sea level forcing is a minor agent and only occasionally more important just close to the bottom. The time scale of vertical mixing of surface water to the bottom or ventilation time scale of bottom water is estimated to be in the range 0.7 h to 9.0 days, with an average age of 2.7 days for the year 2004.The fjord receives fresh water from two streams entering the innermost part of the fjord, and the distribution and age of this water are studied using both ageing and conservative tracers. The salinity variations outside this fjord are large, and in contrast to the salinity, the artificial tracers provide a straight forward analysis of river water content. The ageing tracer is used to estimate transport time scales of river water (i.e. the time elapsed since the water left the river mouth). In May 2004, the typical age of river water leaving the fjord mouth is 5 days. As the major vertical mixing agent is wind, it controls the estuarine circulation and export of river water. When the wind stress is set to zero, the vertical mixing is reduced and the vertical salinity stratification is increased, and the river water can be effectively exported out of the fjord.We also analyse the river tracer fields and salinity field in relation to along estuary winds in order to detect signs of wind-induced straining of the along estuary density gradient. We find that events of down estuary winds are primarily associated with a reduced along estuary salinity gradient due to increased surface salinity in the innermost part of the fjord, and with an overall decrease in vertical stratification and river water content at the surface. Thus, our results show no apparent signs of wind-induced straining in this shallow fjord but instead they indicate increased levels of vertical mixing or upwelling during down estuary wind events.     

The Adriatic sea hydrography and circulation in spring and autumn (1985–1987)

The Adriatic basin-wide circulation and its temporal variability are reviewed on the basis of results from the analysis of hydrographic data collected during four POEM cruises. Major well known features in the circulation are revealed in the data set which covers the period from October 1985 to April 1987. A prominent signal associated with the seasonal variability is identified in the water outflowing along the Italian coast. Differences between autumn and spring in the vein of cold and fresh water flowing along the Italian shelf manifest mainly in the temperature field. During the stratified season the fresh water spreads over the entire surface layer of the southern Adriatic. On the other hand, during spring, when the sea is vertically homogeneous, the fresh water remains confined to the surface longshore boundary layer over the entire length of the Italian coast. Layers below the seasonal thermocline at the eastern portion of the sea display very weak seasonal signals. A strong signal associated with the inter-annual variations also has been documented from the analysed data set; it mainly appears in the salinity field. It is shown that in spring 1986, the salinity averaged over the entire water column north of the Palagruza Sill is lower by 0.3 psu than in spring 1987. A similar, but less prominent difference is noted in the southern Adriatic. An attempt is made to associate these differences with variations in climatic conditions over the area, the river runoff and the Mediterranean water inflow.     

基于Tweedie-GAM模型研究海州湾小黄鱼资源丰度与栖息环境的关系

本研究根据2011年及2013—2016年春季和秋季在海州湾及其邻近海域进行的底拖网调查数据，结合同步采集的底层海水温度、底层海水盐度、水深、底质类型，以及脊腹褐虾(Crangon affinis)、细螯虾(Leptochela gracilis)、鳀(Engraulis japonicus)、赤鼻棱鳀(Thrissa kammalensis)等小黄鱼(Larimichthys polyactis)主要饵料生物的资源丰度数据，采用条件数κ和方差膨胀因子(VIF)度量多重共线性的程度，选取关键环境因子，再应用基于Tweedie分布的广义可加模型(GAM)研究不同季节和不同生长阶段的小黄鱼资源丰度与环境因子的关系。多重共线性的检验表明，所有初始变量之间没有显著的多重共线性，均可作为解释变量代入模型。结果表明:不同季节和生长阶段，影响小黄鱼资源分布的主要因子及其偏差解释率各不相同，各变量所对应的适宜范围也不同。例如:影响春季小黄鱼幼体资源分布的主要因子有底层海水温度、底层海水盐度、水深和脊腹褐虾的分布，其中偏差解释率最大的因子为水深(16.09%)；而影响春季成体资源分布的因子为底层海水温度、底层海水盐度、水深及脊腹褐虾和鳀的分布，其中偏差解释率最大的因子为底层海水盐度(13.56%)。本研究表明，海州湾及其邻近海域不同季节和不同生长阶段小黄鱼的资源分布与其自身的生态习性、海洋环境以及饵料生物的分布密切相关。     

山东南部近海秋季长蛇鲻相对资源量的分布及其影响因素

为探究长蛇鲻(Saurida elongate)的生态习性和分布规律,并为长蛇鲻资源的合理利用与养护提供科学依据,本文根据2016年秋季在山东南部近海进行的渔业资源与环境调查数据,分析了该海域长蛇鲻的分布特征,研究长蛇鲻成体、幼体的分布差异,并利用广义可加模型(GAM)研究其分布与生物因子和环境因子的关系。结果表明,长蛇鲻成体与幼体的分布存在差异,成体分布范围广,幼体主要分布在30 m等深线及以浅水域。GAM模型的结果表明,饵料生物、底层水温、水深和底层盐度是影响长蛇鲻相对资源量分布的主要因子。成体、幼体的分布与影响因子的关系差异极显著(P<0.01)。长蛇鲻成体的相对资源量随饵料生物和底层水温的增加表现为先上升后下降的趋势,而幼体呈现一致上升趋势;成体和幼体的相对资源量随水深增加均呈下降趋势;幼体相对资源量随底层盐度增加有明显上升趋势,而盐度对成体的影响不显著。本研究认为山东南部近海是长蛇鲻的重要栖息地,水温和盐度是成体和幼体分布差异的可能原因。