Nutrient and Plankton Dynamics in the NE and NW Gyres of the Subarctic Pacific Ocean

The western subarctic gyre (WSG) and the eastern Alaska Grye (AG) on each side of the subarctic North Pacific, have many similarities. In both gyres, macronutrients are generally high and chl is low, and hence both gyres are High Nitrate, Low Chlorophyll (HNLC) regions. Despite the general similarities between these two gyres, there are many important differences. The time series station established at Stn KNOT on the southwest edge of the WSG and two in situ mesoscale iron enrichment experiments at each of the gyres has provided more information on iron concentrations, the dual role of iron and silicate limitation and seasonal cycles in the gyres. There is more seasonality in many parameters at Stn KNOT than at Stn P. There is an increase in Chl and primary productivity at Stn KNOT in May followed by increased iron limitation in summer. Low DIC:NO₃ ratios and high Si:NO₃ ratios in the WSG, indicate lower calcification and higher diatom production than at Stn P. The sources of iron for these areas are still not clear, but horizontal transport of iron rich coastal water and vertical transport could be important sources at certain times of the year in addition to dust input. Satellite images show that chl-rich coastal waters occasionally extend to the vicinity of Stn KNOT and therefore Stn KNOT may not always represent conditions in the main part of the WSG. This review focuses mainly on a comparison of Stn KNOT and Stn P, two time series stations on the edge of two very large gyres. At present, we have a limited understanding of the temporal and spatial variability within each of these large gyres. This revised version was published online in July 2006 with corrections to the Cover Date.     

Eddies and Tropical Instability Waves in the eastern tropical Pacific: A review

Mesoscale eddies and tropical instability waves in the eastern tropical Pacific, first revealed by satellite infrared imagery, play an important role in the dynamics and biology of the region, and in the transfer of mass, energy, heat, and biological constituents from the shelf to the deep ocean and across the equatorial currents.From boreal late autumn to early spring, four to 18 cyclonic or anticyclonic eddies are formed off the coastal region between southern Mexico and Panama. The anticyclonic gyres, which tend to be larger and last longer than the cyclonic ones, are the best studied: they typically are 180–500 km in diameter, depress the pycnocline from 60 to 145 m at the eddy center, have swirl speeds in excess of 1 m s⁻¹, migrate west at velocities ranging from 11 to 19 cm s⁻¹ (with a slight southward component), and maintain a height signature of up to 30 cm. The primary generating agents for these eddies are the strong, intermittent wind jets that blow across the isthmus of Tehuantepec in Mexico, the lake district in Nicaragua and Costa Rica, and the Panama canal. Other proposed eddy-generating mechanisms are the conservation of vorticity as the North Equatorial Counter Current (NECC) turns north on reaching America, and the instability of coastally trapped waves/currents.Tropical Instability Waves (TIWs) are perturbations in the SST fronts on either side of the equatorial cold tongue. They produce SST variations on the order of 1–2 °C, have periods of 20–40 days, wavelengths of 1000–2000 km, phase speeds of around 0.5 m s⁻¹ and propagate westward both north and south of the Equator. The Tropical Instability Vortices (TIVs) are a train of westward-propagating anticyclonic eddies associated with the TIWs. They exhibit eddy currents exceeding 1.3 m s⁻¹, a westward phase propagation speed between 30 and 40 km d⁻¹, a signature above the pycnocline, and eastward energy propagation. Like the TIWs, they result from the latitudinal barotropically unstable shear between the South Equatorial Current (SEC) and the NECC with a potential secondary source of energy from baroclinic instability of the vertical shear with the Equatorial Undercurrent (EUC).This review of mesoscale processes is part of a comprehensive review of the oceanography of the eastern tropical Pacific Ocean.     

Silicate to Nitrate Ratio of the Upper Sub-Arctic Pacific and the Bering Sea Basin in Summer: Its Implication for Phytoplankton Dynamics

Consumption of silicate and nitrate (Si:N molar ratio) in the upper layer of the pelagic subarctic Pacific in summer was evaluated by a regression analysis of silicate vs. nitrate concentrations at the upper 100 m depth. Based on data of three cruises, the pelagic subarctic Pacific can be classified into two groups. First group is characterized by roughly 1:1 consumption of silicate and nitrate, and occupies rather larger area of subarcfic Pacific, i.e., the Gulf of Alaska and the Western Subarctic gyre (averaged slope of Si:N linear regression: 1.21, n = 10 and 1.45, n = 9, respectively). Second group is the regions of the Bering Sea basin and the Oyashio region, and showed higher silicate consumption compared to that of nitrate (averaged slope of Si:N linear regression: 2.14, n = 9 and 2.36, n = 3, respectively). The Si:N difference observed is possibly attributed to relative contribution of diatoms production among the phytoplankton assemblages in the regions, i.e., dominance of diatoms production in the regions of the second group. Higher accumulation of ammonium at the bottom of euphotic layer in the summer Bering Sea basin would also contribute to increase consumption ratio of Si:N amounts.     

The particle fluxes in sediment traps from Niulang Guyot area in the Northwest Pacific Ocean

The flux of settling particles in the ocean has been widely explored since 1980s due to its important role in biogenic elements cycling, especially in the transport of particulate organic carbon (POC) in the deep sea. However, research in the seamount area of the oligotrophic subtropical Northwest Pacific Ocean is lacking. In this work, two sediment traps were deployed at the foot and another two at the hillside of Niulang Guyot from August 2017 to July 2018. The magnitude and composition of particle fluxes were measured. The main factors influencing the spatial variations of the fluxes were evaluated. Our results indicated a low particulate flux from Niulang Guyot area in the Northwest Pacific Ocean, reflecting low primary productivity of the oligotrophic ocean. The total mass flux (TMF) decreased from 2.57 g/(m2·a) to 0.56 g/(m2·a) with increasing depth from 600 m to 4 850 m. A clear seasonal pattern of TMF was observed, with higher flux in summer than that in winter. The peak flux of 26.52 mg/(m2·d) occurred in August at 600 m, while the lowest value of 0.07 mg/(m2·d) was shown in February at 4 850 m. The settling particles at the deep layers had similar biochemical composition, with calcium carbonate (CaCO₃) accounting for up to 90%, followed by organic matter and opal, characteristics of Carbonate Ocean. The POC flux decreased more rapidly in the twilight layer because of faster decomposition, remineralization, and higher temperature. A small fraction of POC was transported into the deep ocean by biological pump. Particle fluxes were mainly controlled by the calcareous ballasts besides the primary productivity of the surface water. The advection may be another important factor affecting the flux in the seamount area. The combination of settled matters rich in foraminiferal tests with topography and currents may be the reason for regulating the local abundance of benthos on seamounts. Our results will fill in the knowledge gap of sedimentation flux, improve the understanding of ecosystem in Niulang Guyot area, and eventually provide data support for the optimization of regional ecological modeling.     

西北太平洋不同寿命中尺度涡统计特征

本研究通过OW(Okubo-Weiss)参数和闭合等值线相结合的方法自动识别西北太平洋(0°—45°N,120°—180°E)中尺度涡并跟踪后续中尺度涡,分析了不同寿命中尺度涡的季节变化、年际变化、数量特征以及动力学参数等。研究发现,不同寿命中尺度涡的数量高峰时间在不同程度上晚于气象上最冷月份约1～3个月。与其他寿命中尺度涡不同,中等寿命中尺度涡的气旋涡(33.9 cm/s)比中等寿命中尺度涡的反气旋涡(16.9 cm/s)旋转得更快,季节变化最为显著。冬季更适于西北太平洋中尺度涡的发生与发展,并且在寿命上,更易发展为中等寿命涡旋。不同寿命中尺度涡的月数量变化都存在3个明显的周期性变化(第一主周期、第二主周期、第三主周期),根据不同主周期的时间尺度长短,它们的影响因子分别可能是太阳辐射、ENSO现象、季节变化。从地理分布看,不同寿命中尺度涡高频区分布并不完全一致。从涡旋平均振幅地理分布看,中等寿命中尺度涡在高频区拥有最大的涡旋平均振幅(15～25 cm),短寿命中尺度涡次之(15～20 cm),长寿命中尺度涡的平均振幅最小(10～16 cm)。从涡旋半径地理分布看,长寿命中尺度涡仅在副...     

西北冰洋中太平洋入流水营养盐的变化特征

利用1999,2003和2008年夏季(7-9月)三次中国北极科学考察数据资料,分析和讨论太平洋入流水营养盐的分布和楚科奇海关键生物地球化学过程对太平洋水化学性质的改造.结果表明,2003和2008年在白令海峡南部64.3°N纬向断面(BS断面)由于水团性质差异显著,营养盐呈西高、东低的分布趋势.2003年BS断面水柱...     

POC fluxes from euphotic zone estimated from 234Th deficiency in winter in the northwestern North Pacific Ocean

1IntroductionThefluxesofcarbon,nutrients,andassoci-atedelementsinvolvedinthebiogeochemicalcyclesoutoftheeuphoticzoneareimportantinthestudyofglobalCO2 change.Someworkershaveproposedthatatthesteadystatethefluxofparticulateorganiccarbonoutoftheeuphoticzoneequalsthenewproduction(EppleyandPe-terson,1979;Eppley,1989).Generallytwometh-odscanbeemployedtoobtainthefluxdata.Oneistousesedimenttrapsintheupperocean(<200m)orfloatingsedimenttraps.Thoughthesedimenttraptechnologyhasshowntobeuse-fulfortimeser…     

An East-West Comparison of the Transition Zone Coastal Pelagic Nekton of the North Pacific Ocean

During the 1980s and 1990s, scientific research cruises were conducted in both the eastern and western boundary regions of the North Pacific Ocean. The main purpose of these cruises was to examine the abundance and distribution patterns of juvenile salmon in coastal waters. These studies created one of the most extensive databases ever collected on the species composition of coastal Transition Zone epipelagic nekton in the North Pacific Ocean. Catch data from two purse seine and two surface trawl surveys (one each from off northern Japan and eastern Russia and off the West Coast of the U.S.) were examined using multivariate techniques to analyze the community structure of nektonic cephalopods, elasmobranchs, and teleosts in the coastal zone during the summer and autumn months. Juvenile salmonids are generally among the most common species caught, but in terms of overall abundance, other potential competitors with juvenile salmon, such as small squids and clupeoid fishes predominated the catches. Species diversity and dominance varied among areas and gear types. Distinct assemblages were found in each area, but the two regions had closely related species occupying similar ecological positions in each habitat. This revised version was published online in August 2006 with corrections to the Cover Date.     

南海及西北太平洋卫星高度计资料分析:海洋中尺度涡统计特征

采用AVISO提供的卫星高度计融合数据,对南海及西北太平洋(5°～35°N,105°～150°E)1993～2009年17a间的中尺度涡活动进行统计分析.结果表明南海中尺度涡活动具有明显的年际变化,每年观测到产生的中尺度涡个数平均为21～22个,标准差约为4个,占年平均值的20%;而西北太平洋中尺度涡个数的年际差异不大,平均每年观测到150～151个中尺度涡产生,标准差约为14个,仅占年平均值的9%.中尺度涡的逐月统计结果表明南海和西北太平洋的中尺度涡活动均有明显季节变化,1993～2009年间的各月南海和西北太平洋分别观测到30～31个和213～214个中尺度涡产生,标准差分别约为6个和41个,均占各自月平均值的19%.中尺度涡主要集中分布在南海东北部、越南东部和黑潮流轴附近海域.涡动能、海面高度距平均方根以及涡度均方根的空间分布大致与涡旋个数分布一致,但在西北太平洋的低纬海区和黑潮延伸体区域则不甚吻合.在相同的涡旋判别标准下,西北太平洋低纬海区(5°～15°N)观测到的中尺度涡个数比中高纬海区要少得多.     

Hawaii Cyclonic Eddies and Blue Marlin Catches: The Case Study of the 1995 Hawaiian International Billfish Tournament

The combination of prevailing northeasterly tradewinds and island topography results in the formation of vigorous, westward propagating cyclonic eddies in the lee of the Hawaiian Islands on time scales of 50–70 days. These mesoscale (∼10² km) features are nowhere more conspicuous or spin up more frequently than in the Alenuihaha Channel between the Island of Maui and the Big Island of Hawaii. Cyclonic eddies in subtropical waters such as those around Hawaii vertically displace the underlying nutricline into the overlying, nutrient-depleted euphotic zone creating localized biologically enhanced patches. Insight into how these eddies may directly influence pelagic fish distribution is provided by examination of recreational fish catch data coinciding with the presence of eddies on the fishing grounds. We highlight the 1995 Hawaii International Billfish Tournament in which a cyclonic eddy dominated the ocean conditions during the weeklong event and the fish catch distribution differed significantly from the average historical tournament catch patterns. On the tournament fishing grounds, well-mixed surface layers and strong current flows induced by the eddy's presence characterized the inshore waters where the highest catches of the prized Pacific blue marlin (Makaira mazara) occurred, suggesting possible direct (e.g., physiological limitations) or indirect (e.g., prey availability) biological responses of blue marlin to the prevailing environment. This revised version was published online in August 2006 with corrections to the Cover Date.     

太平洋副热带东部模态水的年际变化及机制研究

根据2004—2014年的全球海洋Argo网格数据集(BOA_Argo)和ECMWF ERA-Interim再分析资料,计算了冬季太平洋副热带东部海区的水团变性率及水团形成率,对南北太平洋副热带东部新生成模态水的年际变化及其形成机制进行了研究。结果表明:北太平洋副热带东部模态水(NPESTMW)和南太平洋副热带东部模态水(SPESTMW)的新生成体积及核心密度在2004—2014年具有明显的年际变化:NPESTMW主要经历了2005—2009年和2010—2013年2次持续4～5a的体积和密度增加过程,其中体积最大值出现在2009年,最小值则出现在2005和2014年。南半球SPESTMW则经历了2007—2009年和2010—2013年共两次持续3～4a的体积和密度减小过程,其中体积的最小值出现在2009、2013年,最大值出现在2010年。合成分析发现,由冬季海面热通量异常引起的深混合层内与模态水密度相当的水团表层形成率异常,可能是导致NPESTMW和SPESTMW新生成水体积年际变化的重要因素;同时,SPESTMW新生成水的年际变化受局地风应力旋度的年际变化影响明显。     

热带太平洋活性微生物菌株的筛选和鉴定

从热带太平洋的生物、海水、沉积物样品中分离到细菌、酵母和霉菌共475株．选择8个指示菌并采用圆形纸片法对分离菌株的发酵液进行抗菌和抗肿瘤活性筛选，获得20个具有抗菌和／或抗肿瘤活性的微生物菌株．细菌、酵母和霉菌活性菌株的筛选得率都比较低，分别为5．4％、2．2％和3．4％，其原因可能与纸片的发酵液的添加量较少和菌株发酵条件的控制有关．同时采用分子生物学方法鉴定了活性菌株，除4株未有结果外，其余菌株分归为9个属，其中芽孢杆菌属7株、占活性菌株的35％，盐单胞菌属2株、占10％，其它菌属各1株、占5％．抑菌谱分析表明，大多数活性菌株对革兰氏阳性细菌具有抑制作用，而来源于鱼体的菌株抑菌谱较广，对细菌、真菌均有拮抗作用，另外还发现一株酵母（Rhodosporidium toruloides）可抑制金黄色葡萄球菌．作者提出“活性指示（activity index）”参数，对活性菌株的抗菌谱和活性强度进行综合评估，也表明源于鱼体的菌株的活性指示值较高．这4株芽孢杆菌尤其是DY-Y-11A1A菌株，具有潜在的后续开发价值．     

东太平洋柱状沉积物的古气候和古环境记录

太平洋深海盆地的远洋沉积物在物质组成和来源上远较大陆边缘简单.由于远离大陆,又有海沟与周边大陆分隔,太平洋深海沉积物中通常不包含由河流水系搬运而来的悬浮物,因此从深海沉积物中提取古气候、古环境信息可以避免诸多地质因素相互叠加和干扰[1].深海远洋沉积物中的主要组分是风成陆源碎屑(包括火山碎屑)和来自上层海水的生源组分(降落到洋底的生物壳体)以及由海解作用形成的自生矿物[2],其中陆源碎屑的相对含量、粒度及矿物成分可以反映大气环流的强度及物源区的气候环境[1],生源组分的组成、相对含量和丰度以及种属含量变化则与表层海水的生产力和溶解作用有关.     

Vertical Nutrient Distributions in the Western North Pacific Ocean: Simple Model for Estimating Nutrient Upwelling, Export Flux and Consumption Rates

A one-dimensional, steady-state model has been developed to understand the factors controlling vertical distributions of nutrients such as nitrate and phosphate in the western North Pacific water columns. The model includes simple physics and some biogeochemical processes. Nutrients are supplied by upwelling of nutrient-rich deep waters with a constant upwelling velocity and nutrient regeneration due to decomposition of sinking particulate matter; the latter is expressed by an exponential-type export flux. Nutrients are consumed in the water column due to uptake by marine organisms, represented by a first-order substrate kinetics. The consumption rate constant is given as an exponential function of depth. The model has been applied to a data set of WOCE (World Ocean Circulation Experiment) P9 one-time measurements observed in the western North Pacific. The calculated curves fit well to observed vertical nutrient profiles from 100 m depth to over 2,500 m depth at 35 stations from 19°N to 33°30′ N along 137°E with correlation factors of greater than 0.998. A modified model, including a correction term representing a depth-dependent upwelling velocity, can reproduce observed vertical nutrient profiles at 32 stations from 5°N to 18°30′ N along 137°E with correlation factors greater than 0.993. The results support the hypothesis that most of the vertical nutrient profiles in the western North Pacific are controlled by particle export flux, consumption rate, remineralization rate and upwelling velocity. This revised version was published online in July 2006 with corrections to the Cover Date.     

中国多金属结核开辟区沉积物地球化学特征

对中国多金属结核开辟区沉积物的详细研究表明,研究区内沉积物处于氧化至弱氧化环境,两种色调的沉积物在粒度分布特征以及化学组成上都存在着显著的差异,它们是不同沉积环境的反应.不同色调之间的界面为一沉积间断面.沉积物中的铁和锰具有不同的来源,铁可能以岩源碎屑为主,而锰则更可能是自生成因.钙和镁以生物成因为主.     

分形理论在太平洋多金属结核分布研究中的应用

分形理论与耗散结构、混沌理论一样,是最近一个时期非线性科学研究中所取得的重要成果[1],并在近年来得到了迅速的发展.其主体内容是研究系统的自相似性和不规则性,能为复杂问题的定量化提供新的途径[2].用分形理论研究地质现象是非线性科学的一个重要方向,前人已在地质数据的分形结构、地质时空结构的自相似性及其动力学机制、地质现象的分形重建与矿床分形统计预测方法等方面进行探索,取得了一些重要成果[3～6],但值得指出的是地质分形是统计意义上的无规分形,与数学意义上的严格自相似有区别.     

东太平洋海盆430柱沉积物特征与地层

对东太平洋海盆 ４３０ 柱沉积物的组分、古生物、结构构造以及古地磁、铀系等进行研究后, 将沉积物进行分类、命名与分层, 并确定其年代。研究表明, 本柱由下至上的沉积物分别为含沸石粘土、深海粘土、硅质粘土和钙质粘土。该柱中存在 ４ 个沉积间断, 其中在 ３２５ ｃｍ附近层位有一厚约 １０ ｃｍ 的多金属结核层,此界面为中中新世至晚上新世的沉积间断,它在 Ｃ Ｃ区内普遍存在, 持续时间长, 分布范围广。反映此时南极底层流十分强盛, 对东太平洋 Ｃ Ｃ 区的沉积作用和多金属结核形成与发育产生重要的影响。     

Community Structure and Dynamics of Phytoplankton in the Western Subarctic Pacific Ocean: A Synthesis

The phytoplankton community in the western subarctic Pacific (WSP) is composed mostly of pico- and nanophytoplankton. Chlorophyll a (Chl a) in the <2 μm size fraction accounted for more than half of the total Chl a in all seasons, with higher contributions of up to 75% of the total Chl a in summer and fall. The exception is the western boundary along the Kamchatka Peninsula and Kuril Islands and the Oyashio region where diatoms make up the majority of total Chl a during the spring bloom. Among the picophytoplankton, picoeukaryotes and Synechococcus are approximately equally abundant, but the former is more important in term of carbon biomass. Despite the lack of a clear seasonal variation in Chl a concentration, primary productivity showed a large seasonal variation, and was lowest in winter and highest in spring. Seasonal succession in the phytoplankton community is also evident with the abundance of diatoms peaking in May, followed by picoeukaryotes and Synechococcus in summer. The growth of phytoplankton (especially >10 μm cell size) in the western subarctic Pacific is often limited by iron bioavailability, and microzooplankton grazing keeps the standing stock of pico- and nano-phytoplankton low. Compared to the other HNLC regions (the eastern equatorial Pacific, the Southern Ocean, and the eastern subarctic Pacific), iron limitation in the Western Subarctic Gyre (WSG) may be less severe probably due to higher iron concentrations. The Oyashio region has similar physical condition, macronutrient supply and phytoplankton species compositions to the WSG, but much higher phytoplankton biomass and primary productivity. The difference between the Oyashio region and the WSG is also believed to be the results of difference in iron bioavailability in both regions. This revised version was published online in July 2006 with corrections to the Cover Date.