High-resolution phytoplankton diel variations in the summer stratified central Yellow Sea

Vertical distributions of phytoplankton biomass and community structure were studied in the summer stratified central Yellow Sea (YS) using a submersible spectrofluorometer (Fluoroprobe, bbe Moldaenke, Germany), along with photosynthetic pigments analysis (HPLC-CHEMTAX), and microscope observation. Above all, the results of the dominating group obtained from these methods generally coincided with each other on the transect 35°N. The concentrations of brown algae, green algae and total chlorophyll a (Chl a) biomass were highly correlated between the results of Fluoroprobe observations and pigments analysis (r?=?0.79, 0.91 and 0.82, respectively, n?=?54, p?<?0.01). In the summer stratified central YS, significant differences in phytoplankton compositions on the vertical distribution was observed. On the basis of HPLC-CHEMTAX results, the dominating group of phytoplankton composition generally changed from cyanobacteria to chrysophytes and then to diatoms, from surface to bottom. Interestingly, on the basis of high-resolution observations using Fluoroprobe, a periodic fluctuation of the pycnocline presumably due to the semidiurnal internal tides was observed at an anchor station (35°N, 123°E). In addition, both nutrients and Chl a concentrations at the depth of the subsurface chlorophyll maximum (SCM) seemed to coincide with the rhythm of the pycnocline fluctuation, indicating the latter might have a potential impact on the dynamics of SCM phenomena in the summer stratified central YS.     

秋季季风转换期间台湾海峡遥测叶绿素a的年际变动

The time series of multiple sources of satellite data are used to examine the interannual variability of chlorophyll a concentration （Chl a） and its relation to the physical environment during the autumn monsoon transitional period in the Taiwan Strait （TWS）. The satellite data included the Chl a concentration and sea surface temperature （SST） derived from the Moderate Resolution Imaging Spectroradiometer （MODIS）/ Aqua as well as the multi-sensors merged wind products from 2002 to 2012. The results show that the average Chl a concentration of the whole TWS is mainly contributed by the northern TWS. The average Chl a in the northern TWS is 3.6 times that in the southern TWS. The maximum variability of Chl a is located in the frontal regions between the cold Zhe-Min Coastal Water and the strait warm water. The temporal change of Chl a concentration is different in the northern and southern TWS. The changes in the relative strength of the cold and warm water masses is suggested to be the dominant processes in controlling the phytoplankton growth in the northern TWS, while there is wind-induced mixing in the southern TWS. Additionally, La Nina events exhibited complex effects on the interannual variability of Chl a concentration in autumn. The longterm time series of physical and biological observations are especially needed to better understand how the TWS complex ecosystem responds to climate variations.     

南黄海冷水团海域溶解氧和叶绿素最大现象值及营养盐累积的季节演变

基于2006-2007年在南黄海冷水团海域开展的4个季度月的调查资料, 重点研究了该海域溶解氧(DO)、叶绿素a(Chl a)最大值现象和营养盐累积的季节演变规律。结果表明:春至秋季黄海冷水团海域DO和Chl a最大值层深度具有先加深后变浅的趋势, 出现最大值层的海域面积呈现出先增大后缩小的变化过程, DO和Chl a最大值层的深度及面积在夏季均达到最大, 至冬季DO和Chl a最大值现象消失;夏季冷水团海域深水区DO最大值处的氧含量整体高于春季, 而冷水团边界附近氧最大值处的氧含量整体低于春季;春至秋季冷水域深水区次表层Chl a最大值处的Chl a含量先降低后升高, 于夏季时最低, 入秋后开始升高, 而一年四季中冷水域边界附近Chl a最大值处的Chl a含量却在夏季时最高, 而且显著高于深水区。黄海冷水团海域的底层营养盐储库具有一定的空间异质性, 冷水域底层通常分别在深水区和西部边界处存在营养盐高值核心, 其中位于深水区的高值核心位置季节变化不明显, 而位于冷水域西部边界附近的高值核心位置则呈现出自春季至夏季向西移动、入秋后又向东部移动的季节变化特征。水文物理因素和生物化学过程对DO、Chl a最大值及营养盐储库的季节演变具有重要的调控作用。     

东海区叶绿素a和初级生产力季节变化特征

依据2008年春季(5月)、夏季(8月)、秋季(11月)和2009年冬季(2月)的现场调查结果,分析了东海区叶绿素a、初级生产力的平面分布、垂直分布和季节变化的特征,并探讨了其影响因素。结果表明,四个航次叶绿素a浓度分别为1.33、0.93、1.61和0.65 mg/m3,秋季春季夏季冬季。春季、夏季和秋季最大值均出现在0—10m水层,冬季最大值出现在底层。叶绿素a浓度远海年季变化较小,近岸区和垂直分布年季变化较大。四个航次初级生产力平均为375.03、414.37、245.45和102.60 mg/(m3 h),夏季秋季春季冬季。叶绿素a浓度和初级生产力水平均高于历史同期值。鱼外渔场的年平均初级生产力最大,海州湾渔场最小。通过分析叶绿素a和环境因子的相关性表明,叶绿素a与浮游植物显著正相关;春季和秋季的低温以及春季和夏季的低盐比较适合浮游植物的生长;活性磷酸盐可能是限制春季和秋季叶绿素a的重要因素。     

Mesoscale features and phytoplankton biomass at the GoodHope line in the Southern Ocean during austral summer

Two sets of high-resolution subsurface hydrographic and underway surface chlorophyll a (Chl a) measurements are used, in conjunction with satellite remotely sensed data, to investigate the upper layer oceanography (mesoscale features and mixed layer depth variability) and phytoplankton biomass at the GoodHope line south of Africa, during the 2010–2011 austral summer. The link between physical parameters of the upper ocean, specifically frontal activity, to the spatially varying in situ and satellite measurements of Chl a concentrations is investigated. The observations provide evidence to show that the fronts act to both enhance phytoplankton biomass as well as to delimit regions of similar chlorophyll concentrations, although the front–chlorophyll relationships become obscure towards the end of the growing season due to bloom advection and ‘patchy’ Chl a behaviour. Satellite ocean colour measurements are compared to in situ chlorophyll measurements to assess the disparity between the two sampling techniques. The scientific value of the time-series of oceanographic observations collected at the GoodHope line between 2004 to present is being realised. Continued efforts in this programme are essential to better understand both the physical and biogeochemical dynamics of the upper ocean in the Atlantic sector of the Southern Ocean.     

Seasonal change of oceanographic conditions and chlorophyll <Emphasis Type="Italic">a</Emphasis> vertical distribution in the southwestern Okhotsk Sea during the non-iced season

Seasonal changes in oceanographic conditions related to primary productivity was investigated in the southwestern Okhotsk Sea during non-iced seasons, using the observation data conducted in 2000∼2006. Based on hydrographic characteristics, the studied area could be classified into two regions, the Coastal Region which is influenced under the Soya Warm Current and the Forerunner Water of the Soya Warm Current, and the Offshore Region where the Intermediate Cold Water was located in the subsurface layer. This study is the first report on seasonal change of nutrient and chlorophyll a concentrations in the offshore region of the southwestern Okhotsk Sea. Variability of concentrations of chlorophyll a and nutrients is temporally and regionally high in the Coastal Region. The maximum chlorophyll a concentration in April was observed at the surface layer of both regions. The most remarkable feature on the vertical structure in the Offshore Region was the consistent existence of the Intermediate Cold Water and the development of seasonal thermocline in the subsurface layer during summer and autumn. The stratification formed within the euphotic zone in the Offshore Region resulted in the formation of the subsurface chlorophyll a maximum (SCM) from May to October. Throughout the research period, although less amplitude of nutrients at the surface was observed in the Coastal Region than that in the Offshore Region, comparable amplitude of chlorophyll a concentration was observed between regions. These results suggested differences of environmental conditions for primary production between the two regions. Depending on the presence of SCM, relationships between chlorophyll a concentration at the sea surface and chlorophyll a standing stock within the euphotic layer were different. At most stations with SCM, the surface chlorophyll a concentration was lower than 0.6 mg m-3. This suggests that the presence of SCM and the chlorophyll a standing stock within the euphotic layer may be estimated using the surface chlorophyll a concentration from spring to autumn in the studied area.     

南海北部表层颗粒有机碳的季节和年际变化遥感分析

海洋颗粒有机碳（POC）是海洋固碳的一个关键参数。为了研究南海北部陆架及海盆表层POC浓度的时空分布特征以及变化趋势,本文利用2009-2011年4个季节的实测数据,对NASA发布的MODIS/AQUA卫星月平均POC遥感产品,进行了验证和校正;并利用校正后的遥感数据分析了2003-2014年POC的时空分布特征和变化趋势。发现POC遥感产品与南海北部实测数据具有较好的线性关系（R2=0.72）,但存在系统性偏高,需利用实测数据对遥感数据进行区域性校正。分析校正后的遥感数据发现,南海北部陆架POC浓度较高,平均为（33.34±8.02）mg/m3;吕宋海峡西南海域浓度较低,平均为（29.25±6.20）mg/m3;中央海盆区浓度最低,平均为（27.02±4.84）mg/m3。春夏季POC浓度较低,最低值一般出现在5月,冬季（12月至翌年1月）POC浓度达到最高。利用2003-2014年的长时间序列遥感叶绿素（Chl a）和海表温度（SST）、混合层深度（MLD）模式数据,以及实测数据对南海北部POC浓度的影响机制进行了分析。发现POC与Chl a在秋冬呈现较好的相关关系（R2=0.51）,但在春夏季较离散,表明秋冬季生物作用对POC影响较大。2003-2014年期间,POC与Chl a、MLD及SST存在明显的年际变化,但并没有显著的上升或下降趋势。     

南极威德尔海春季海冰物理结构对叶绿素上限含量的影响

2006年冬末春初,在德国POLARSTERN科学考察船执行南极威德尔海西北海域考察期间,调查了考察区海冰物理和海洋生物。本文观测了航线上钻取的27支海冰冰芯的组构和71个冰晶体薄片;分析得到393组冰温数据;348组盐度、密度数据和311组叶绿素a和脱镁叶绿素含量数据;通过302组冰内相同深度孔隙率和叶绿素a含量数据分析,发现海冰物理参数影响冰内叶绿素a含量的新证据;利用收集的雪、冰厚度数据以及环境容量制约生态平衡的规律,建立了雪、冰厚度对冰底叶绿素繁荣的影响以及;确立了南极粒状冰和柱状冰内叶绿素a上限含量同卤水体积的关系。从而表达了冰晶体对卤水排泄的效应和冰物理性质对南极春季冰底和冰-水界面叶绿素a增长的贡献。此外,还得出海冰物理性质影响冰藻,并且是南极冰区水体浮游植物繁荣的关键控制因素。     

基于复合模型的西南大西洋阿根廷滑柔鱼（Illex argentinus）时空分布研究

本文利用2003-2011年西南大西洋阿根廷滑柔鱼渔业数据和海洋环境数据，包括海表温度（sea surface temperature， SST），海面高度（sea surface height， SSH）和叶绿素浓度（chlorophyll a， Chl a），开发基于广义加性模型（GAM）和神经网络模型（NNM）的复合模型研究滑柔鱼资源时空分布。GAM用于选择关键影响因子，并分析与单位捕捞努力量渔获量（catch per unit effort， CPUE）的关系，NNM用于建立关键影响因子与CPUE之间的预报模型。结果表明：GAM选择的影响因子的偏差解释率为53.8%，空间变量（经度和纬度），环境变量（SST、SSH、Chl a）均匀CPUE之间存在显著相关性。CPUE与SST和SSH之间为非线性关系，与Chl a之间为线性关系。NNM模型的MSE和ARV较低，其精度高且稳定。此复合模型也能够解释解释西南大西洋阿根廷滑柔鱼时空变化趋势和迁徙模式。     

夏季南海西部叶绿素浓度高值带的年际变化

基于1998-2013年SeaWiFS和MODIS传感器的叶绿素浓度资料,本文分析了夏季南海西部叶绿素浓度高值带的年际变化规律。夏季,叶绿素及营养盐在海流的作用下离岸输送,从而在南海西部形成叶绿素浓度高值带,其分布与东向急流的流向一致。分析结果显示,高值带分布主要受13°N以南海域风场的调控,且滞后风场1周。当13°N以南海域受异常东北风（西南风）控制时,高值带位于其多年平均位置以北（南）。     

Variabilité spatio-temporelle de la biomasse microphytobenthique en rade de Brest et en Manche occidentale

Microphytobenthic biomass was estimated in the Bay of Brest (1994) and the western English Channel (Trezen Vraz, 1993) using spectrophotometry. Best results (42 % difference) were obtained with an instantaneous extraction procedure at room temperature, compared with the cold extraction procedure. Chlorophyll biomass in sediment was higher in the western English Channel (65–215 mg Chl a m⁻²) than in the Bay of Brest (10–113 mg Chl a m⁻²), in contrast to total pigment biomass (Chl a + pheo a : 88–254 mg m⁻² at Trezen Vraz vs. 131–934 mg m⁻² in the Bay of Brest). This study emphasized decreasing pigment biomass from the estuary to the open sea. Low benthic pigment biomass in the Bay, compared to eutrophic ecosystems, agrees with previous studies on the pelagic system, suggesting that there is no eutrophication in the Bay of Brest. Microphytobenthic blooms were strongly correlated with environmental factors, such as river floods, light intensity, water temperature and the spring/neap tidal cycle. Turbidity and light could be limiting factors at Roscanvel, i.e. the deepest site facing gyre circulation. The latter would favour sedimentation of silt particles at the sediment-water interface. Microphytobenthos population dynamics would be also dependent on the spring/neap tidal cycle, since maximum chlorophyll biomass occurred at neap tides at all three sites in the Bay of Brest, in contrast to the western English Channel. Lower temporal variations of pigment biomass in sediment were observed in the Channel, compared with the Bay of Brest; maximum chlorophyll biomass in sediment was found to occur three to four weeks after the phytoplankton blooms.     

中国南海表层叶绿素a季节内变化特征及成因

对中国南海表层叶绿素a季节内变化的研究有助于深入认识其海洋特征,满足渔情预报等实际应用需求。利用卫星观测资料分析南海表层叶绿素a不同季节的季节内变化特征,结果表明南海表层叶绿素a季节内振荡强度冬季最高。冬季和春季的季节内振荡最强区域都位于吕宋岛西北侧海区,夏季和秋季振荡较强的区域偏向菲律宾群岛一侧。分析表明研究海区表层温度和表层叶绿素a 存在负相关,冬强夏弱,北强南弱。大部分海区海面高度和叶绿素a 相关性不显著,但南海东南边缘海区海面高度和叶绿素a在季节内存在正相关。冬季海盆尺度逆时针旋转的环流结构应是这些现象产生的原因。除南海东南边缘海区、海南岛东南海区和吕宋岛西侧海区之外,风应力大小和热通量均与叶绿素a 在季节内呈正相关。这显示非局地风场和海流等因素、海洋动力调整过程可能在吕宋海峡以西和南海东南边缘的表层叶绿素a 季节内变化中起到重要作用。     

Succession of phytoplankton functional groups from spring to early summer in the central Bohai Sea using HPLC–CHEMTAX approaches

Phytoplankton is a key component in the functioning of marine ecosystems, phytoplankton community structures are very sensitive to their environment. This study was conducted in the central Bohai Sea in the spring and early summer of 2015. Spatial variations in phytoplankton functional groups were examined through high-performance liquid chromatography pigment–CHEMTAX analysis. Results suggested that the phytoplankton biomass (chlorophyll a [Chl a]) in spring was mainly derived from the diatom community and was 3.5-fold higher than that in the summer. Meanwhile, the phytoplankton in the early summer sustained more diverse marker pigments than that in the spring. Despite the overwhelming predominance of microsized phytoplankton in the spring, some smaller phytoplankton (pico- or nanosized), including flagellates, such as prasinophytes, chlorophytes, and cryptophytes, highly contributed to the total Chl a in the summer. Various physico-chemical variables were recorded, and their correlations with phytoplankton density were established by redundancy analysis. Temperature, water stratification, nutrient availability, and even nutritive proportion influenced the succession of phytoplankton functional groups from diatom dominance in the spring to flagellate (mainly haptophytes and prasinophytes) dominance in the early summer. In conclusion, our work comprehensively evaluated the phytoplankton diversity and dynamics in the central Bohai Sea and suggests the need for long-term monitoring for further investigation.     

Vertical distribution of suspended particulate matter in the Caspian Sea in early summer

The features of the vertical distribution of chlorophyll a, particulate organic carbon and its isotopic composition, total suspended particulate matter (SPM), and the structure of the phytoplankton community in the Middle and South Caspian Sea in May–June 2012 are discussed. The subsurface chlorophyll a maximum (SCM) was found everywhere at depths of ~20 to 40–60 m. The position of this layer is confined to the depth of the seasonal thermocline, which is determined by the development of a cold-water (dark) phytocenosis. The genesis of this layer was studied. The increase in chlorophyll a concentration in this layer is caused by an abundance of phytoplankton or an increased concentration of this phytopigments per algal cell. The highest values of the studied organic compounds and phytoplankton biomass are revealed as close to the seasonal thermocline extending from the southern periphery of the Derbent Depression to the Apsheron Sill, which is determined by the bottom topography. The presence of chlorophyll a at depths exceeding 300 m (up to ≥1 mg/m³) was revealed. This was supported by findings of individual algal cells containing chlorophyll a and even their accumulations in the deep water layer. The most probable mechanisms responsible for the presence of these cells at the deep water level are discussed in the paper. The vertical distribution of the values of the organic carbon isotopic composition is primarily controlled by the vertical structure of phytoplankton and chlorophyll a in the water column up to ~500 m and by biogeochemical processes at the redox barrier (~600 m layer). The relative stability of chlorophyll a and the stability of pheophytin a in anaerobic environments were verified. A significant amount of weakly transformed chlorophyll a was found close the sea bottom.     

长江口南部赤潮区春季表层沉积物中色素组成、含量与分布状况

为剖析长江口邻近海域春季硅藻藻华后期藻类沉降与底层水体缺氧现象之间的关系,作者于2011年春季,在长江口南部赤潮区采集了表层沉积物样品,并通过高效液相色谱法(HPLC),对浮游植物色素进行了分析。结果表明,硅藻藻华发生后,表层沉积物中叶绿素a(Chl a)、岩藻黄素(Fuco)和19’-丁酰氧基岩藻黄素(But-Fuco)含量有显著增加,高值区主要分布在调查海域东南侧50 m等深线外侧,与底层低氧水体分布区基本吻合。因此,硅藻藻华后沉降的藻类对于该海域夏季缺氧区的形成应具有一定作用,其具体过程和机制仍有待于研究。     

基于遥感数据对比南海和阿拉伯海夏季叶绿素a浓度

The South China Sea(SCS) and the Arabian Sea(AS) are both located roughly in the north tropical zone with a range of similar latitude(0°–24°N). Monsoon winds play similar roles in the upper oceanic circulations of the both seas. But the distinct patterns of chlorophyll a(Chl a) concentration are observed between the SCS and the AS.The Chl a concentration in the SCS is generally lower than that in the AS in summer(June–August); the summer Chl a concentration in the AS shows stronger interannual variation, compared with that in the SCS; Moderate resolution imaging spectroradiometer(MODIS)-derived data present higher atmospheric aerosol deposition and stronger wind speed in the AS. And it has also been found that good correlations exist between the index of the dust precipitation indicated by aerosol optical thickness(AOT) and the Chl a concentration, or between wind and Chl a concentration. These imply that the wind and the dust precipitation bring more nutrients into the AS from the sky, the sub-layer or coast regions, inducing higher Chl a concentration. The results indicate that the wind velocity and the dust precipitation can play important roles in the Chl a concentration for the AS and the SCS in summer. However aerosol impact is weak on the biological productivity in the west SCS and wind-induced upwelling is the main source.     

Phytoplankton dynamics associated with the monsoon in the Sulu Sea as revealed by pigment signature

Phytoplankton dynamics during the northeast monsoon was investigated in the Sulu Sea from algal pigment analysis. We visited the Sulu Sea in February 2000, a mid period of the northeast monsoon, and in November and December 2002, the beginning of the northeast monsoon. SeaWiFS images showed generally low concentrations of surface chlorophyll a (Chl a) during the southwest monsoon and higher concentrations with several peaks during the northeast monsoon. In the beginning of the northeast monsoon, subsurface chlorophyll maxima (SCM) occurred, where vertical variation in class-specific composition as estimated from pigment signatures was prominent. Prochlorococcus, cyanobacteria, prymnesiophytes and crysophytes were important groups above the SCM, and the contribution of cyanobacteria to Chl a became much lower at and below the SCM. Contributions of chlorophytes and prasinophytes to Chl a generally showed maxima near the SCM. This distribution was accompanied by vertical changes in the concentration of photoprotective pigments relative to photosynthetic accessory pigments. During the mid northeast monsoon, the upward supply of nutrients was probably enhanced at some stations due to vertical mixing, and as a consequence diatoms dominated in the upper 100 m water column of these stations, and other eukaryotic flagellates including prymnesiophytes, chrysophytes and cryptophytes were secondary major components of the community. The elevation of Chl a concentration and changes in phytoplankton community during the northeast monsoon likely influence the variation in biological production at higher trophic levels in the Sulu Sea.     

Carbon production and export from Biscayne Bay,Florida. I. Temporal patterns in primary production,seston and zooplankton

Five stations along a transect from the western shore of Biscayne Bay, Florida to the Florida Current were sampled monthly for one year. The variability and amount of seston particulate organic carbon, adenosine triphosphate, chlorophyll a, primary production and zooplankton decreased along the seaward transect. The greater inshore biomass and variability of seston were the result of the allochthonous input of detritus and inorganic nutrients via terrestrial runoff. Annual primary production in this subtropical coastal lagoon ranged from 13 to 46 g C m^?2 yr^?1. Chlorophyll a in the bay ranged from 1 to 3 mg chlorophyll a m^?2. In contrast, chlorophyll a in the surface centimetre of the sediment ranged from 50 to 300 mg chlorophyll a m^?2. In this clear, shallow (2 to 3 m), oligotrophic lagoon, over 90% of total primary production is by submerged macrophytes and benthic algae. The high zooplankton biomass in the bay is most likely sustained by macrophyte detritus and the resuspension of benthic diatoms by the high winds associated with summer squalls and winter cold fronts.     

Spatial variability and temporal dynamics of surface water pCO2, ��O2/Ar and dimethylsulfide in the Ross Sea, Antarctica

We report results from two surveys of pCO₂, biological O₂ saturation (??O₂/Ar) and dimethylsulfide (DMS) in surface waters of the Ross Sea polynya. Measurements were made during early spring (November 2006-December 2006) and mid-summer (December 2005-January 2006) using ship-board membrane inlet mass spectrometry (MIMS) for high spatial resolution (i.e. sub-km) analysis. During the early spring survey, the polynya was in the initial stages of development and exhibited a rapid increase in open water area and phytoplankton biomass over the course of our ∼3 week occupation. We observed a rapid transition from a net heterotrophic ice-covered system (supersaturated pCO₂ and undersaturated O₂) to a high productivity regime associated with a Phaeocystis-dominated phytoplankton bloom. The timing of the early spring phytoplankton bloom was closely tied to increasing sea surface temperature across the polynya, as well as reduced wind speeds and ice cover, leading to enhanced vertical stratification. There was a strong correlation between pCO₂, ??O₂/Ar, DMS and chlorophyll a (Chl a) during the spring phytoplankton bloom, indicating a strong biological imprint on gas distributions. Box model calculations suggest that pCO₂ drawdown was largely attributable to net community production, while gas exchange and shoaling mixed layers also exerted a strong control on the re-equilibration of mixed layer ??₂ with the overlying atmosphere. DMS concentrations were closely coupled to Phaeocystis biomass across the early spring polynya, with maximum concentrations exceeding 100 nM.During the summer cruise, we sampled a large net autotrophic polynya, shortly after the seasonal peak in phytoplankton productivity. Both diatoms and Phaeocystis were abundant in the phytoplankton assemblages during this time. Minimum pCO₂ was less than 100 ppm, while ??O₂/Ar exceeded 30% in some regions. Mean DMS concentrations were ∼2-fold lower than during the spring, although the range of concentrations was similar between the two surveys. There was a significant correlation between pCO₂, ??O₂/Ar and Chl a across the summer polynya, but the strength of these correlations and the slope of O₂ vs. CO₂ relationship were significantly lower than during the early spring. Summertime DMS concentrations were not significantly correlated to phytoplankton biomass (Chl a), pCO₂ or ??O₂/Ar. In contrast to the early spring time, there were no clear temporal trends in summertime gas concentrations. Rather, small-scale spatial variability, likely resulting from mixing and localized sea-ice melt, was clearly evident in surface gas distributions across the polynya. Analysis of length-scale dependent variability demonstrated that much of the spatial variance in surface water gases occurred at scales of <20 km, suggesting that high resolution analysis is needed to fully capture biogeochemical heterogeneity in this system.     

Diel vertical migration of the copepod Calanus sinicus before and during formation of the Yellow Sea Cold Bottom Water in the Yellow Sea

To understand the effects of the Yellow Sea Cold Bottom Water(YSCBW)on the diel vertical migration(DVM)of the copepod Calanus sinicus,we surveyed vertical distribution of C.sinicus at a fixed station in the Yellow Sea before(spring)and during(summer)formation of the YSCBW.Cold water(<10 C)was observed in the bottom layer when the water column was thermally stratified in summer,but the water column was thermally well-mixed in spring 2010.Samples were collected from five different layers at 3-h intervals using an opening-closing net.Adult females(1–155 ind./m3)showed a clear normal DVM pattern throughout the entire water column in spring,whereas adult males did not migrate.DVM of copepodite V(CV)individuals was not clear,but the maximum abundance of CI–CIV occurred consistently in the upper 10–20 m layer,where there was a high concentration of chlorophyll-a(Chl-a)(0.49–1.19μg/L).In summer,weak DVM was limited to cold waters beneath the thermocline for adult females(<30 ind./m3),but not for adult males.The maximum abundance of CI–CIV also occurred consistently in the subsurface layer(20–40 m)together with high concentrations of Chl-a(0.81–2.36μg/L).CV individuals(1–272 ind./m3)moved slightly upward nocturnally to the near-surface layer(10–20 m),where the average temperature was 25.74 C,but they were not found in the surface layer(0–10 m;28.31 C).These results indicate that the existence of the YSBCW affected food availability at depth and the vertical temperature distribution,leading to variation in the amplitude and shape of stage-specific vertical distributions(CI to adults)in C.sinicus before and during the formation of cold waters in the Yellow Sea during the study period.