Exploring seamount ecosystems and biodiversity in the tropical Western Pacific Ocean

正Seamounts are underwater mountains that rise at least 1 000 m from the seafloor.They are generally extinct underwater volcanoes,of which a few remain active and support both vent and seamount communities.Seamounts constitute distinct submarine landscape of the world's ocean floor and over half the number of seamounts occur in the Pacific Ocean,     

Analysis of differences in nutrients chemistry in seamount seawaters in the Kocebu and M4 seamounts in Western Pacific Ocean

Comprehensive surveys were conducted in the Kocebu deep seamount and the M4 shallow seamount in the Western Pacific Ocean in March 2018 and May 2019,respectively.The distributions of nutrients in euphotic zone of the two seamount-areas were revealed,and the causative controlling factors were analyzed.Results show that the vertical distribution of nutrients in the two seamount-areas accorded with the general law of the oligotrophic ocean.The concentrations of NO_3-N,PO_4-P,and SiO_3-Si generally increased gradually with the increase of water depth,and they were extremely low in water layers within100 m.The area of high N02-N concentration well agreed with the Deep Chlorophyll Maximum Layer.On the other hand,the distribution of water masses and phytoplankton and hydrological conditions in the two seamount-areas were different,resulting in lower concentrations of NO_3-N,PO_4-P,and SiO_3-Si in the water layers below 100 m in the Kocebu seamount area than those in the M4 seamount area.In addition,N02-N was affected by the distribution of phytoplankton,and distributed mainly in the water layers of 150 and100 m.There was upwelling in the euphotic zone of M4 seamount area,causing accumulations of nutrients and phytoplankton around the seamount,forming a "seamount effect";however,no such an effect was found in Kocebu seamount area.Affected by the composition of biological community and the "seamount effect",the nitrogen limitation in the M4 seamount area was not significant,and the dissolved inorganic nitrogen(DIN):PO_4-P and SiO_3-Si:DIN were closer to the Redfield ratios.     

Planktonic ciliate trait structure variation over Yap,Mariana,and Caroline seamounts in the tropical Western Pacific Ocean

Trait structure is increasingly used in plankton ecology to understand diversity and biogeography.However,our knowledge of micro zooplankton(e.g.planktonic ciliates) trait structure and its variation with hydrography is limited.In this study,we analyzed planktonic ciliate trait structure in waters with different hydrography and deep Chlorophyll a maximum(DCM) layers over three seamounts:Yap,Mariana,and Caroline seamounts.Mariana seamount had a lower surface temperature than the Yap and Caroline seamounts.DCM layers over Mariana and Caroline seamounts were deeper than Yap seamount.There was a weak upwelling in upper 50 m around top of Mariana seamount.The ciliate distribution showed bimodal pattern(high abundance appeared in the surface and DCM layers) over three seamounts.At surface layer,the large size-fraction(30 μm) abundance proportion to aloricate ciliate over Yap seamount(44.4%)was higher than Mariana(32.8%) and Caroline(36.1%) seamounts.For tintinnid abundance proportion to total ciliate,Mariana(12.0%) and Caroline(11.5%) seamounts at about 100-m depth were higher than that of Yap seamount(6.4%).Vertically,tintinnid could be divided into 4 groups over the three seamounts.At30-m depth,group I(species occurring from surface to 100 m only) was dominant component over Yap and Caroline seamounts,while group IV(species occurring at every depth) changed into dominant component over Mariana seamount,the weak upwelling might be the reason.Salpingella faurei was the top dominant species,which corresponded to deeper DCM layers over Mariana and Caroline seamounts.Our results showed that the upwelling and the deeper DCM could influence the planktonic ciliate trait structure.     

Control factors of DIC in the Y3 seamount waters of the Western Pacific Ocean

An investigation was carried out in the Y3 seamount area of the Western Pacific Ocean in December 2014,and the distribution of dissolved inorganic carbon(DIC) and its relationship with environmental factors in this area were explored.The results show that DIC concentration was higher in the adjacent waters of the Y3 seamount area,and the uplift of DIC isolines at the stations was close to the seamount.Meanwhile,interaction between the North Equatorial Current(NEC) and the Y3 seamount affected the DIC distribution i.e.,the upwelling in the same direction of the NEC was obvious,resulting in a decreasing trend of average concentration of DIC in the 200 m water column from the top to the two side s in this direction but in the cross direction.The DIC concentration increased with the water depth increase,and its distribution was affected by various environmental factors.In the surface water,high temperature was a decisive factor for the decrease of the DIC concentration,but the photosynthesis of phytoplankton showing only a weak influence.In the North Pacific Tropic Water(NPTW),DIC production rate from organic matter decomposition was higher than that of DIC consumption by phytoplankton photosynthesis,leading to a continual increase of DIC.In the North Pacific Intermediate Water(NPIW),organic matter decomposition played a leading role in the increase of DIC.In the deep water,decomposition of organic matter weakened,and the dissolution of CaCO_3 controlled the carbonate system,and DIC had the smallest variation range.     

Characterization and diversity of magnetotactic bacteria from sediments of Caroline Seamount in the Western Pacific Ocean

Journal of Oceanology and Limnology - Magnetotactic bacteria(MTB) are a group of microorganisms capable of orientating and swimming along magnetic fields because they contain intracellular...     

Erratum to: Analysis of differences in nutrients chemistry in seamount seawaters in the Kocebu and M5 seamounts in Western Pacific Ocean

Journal of Oceanology and Limnology - Comprehensive surveys were conducted in the Kocebu deep seamount and the M4 shallow seamount in the Western Pacific Ocean in March 2018 and May 2019,...     

A new species of Macandrewia(Demospongiae,Tetractinellida,Macandrewiidae) from a seamount in the Western Pacific Ocean

A new species of Macandrewia Gray from a seamount near Yap Trench in the Western Pacific Ocean was described.Macandrewia yapensis sp.nov.is distinct from its congeners by possessing a foliate shape with contorted lamellae,tuberculiform terminations of desmas,and unique size of spicules.This is the third species of Macandrewia described from the Pacific Ocean.In addition a partial sequence of COI gene was obtained from the new specimen and then it submitted to GenBank.Phylogenetic tree constructed with the partial COI sequences appears to exhibit a more congruent relationship with morphological data of macandrewiid species compared to 28 S gene tree.     

Variabilities of surface current in the tropical Pacific Ocean

The Simple Ocean Data Assimilation (SODA) package is used to better understand the variabilities of surface current transport in the Tropical Pacific Ocean from 1950 to 1999. Seasonal variation, internnual and decadal variability analyses are conducted on the three major surface currents of the Tropical Pacific Ocean: the North Equatorial Current (NEC), the North Equatorial Countecurrent (NECC), and the South Equatorial Current (SEC). The transport of SEC is quite larger than those of NEC and NECC. The SEC has two maximums in February and August. The NEC has a small annual variation. The NECC has a maximum in October and is very weak in March and April. All currents have remarkable interannual and decadal variabilities. The variabilities of the NEC and the SEC related to the winds over them well, but the relationship between the NECC and the wind over it is not close. Analysis related to El Niño-Southern Oscillation (ENSO) suggests that before El Niño (La Niña) the SEC is weaker (stronger) and the NECC is stronger (weaker), after El Niño (La Niña) the SEC is stronger (weaker) and the SEC is weaker (stronger). There is no notable relationship between the NEC and ENSO.     

Morphology and phylogeny of Chrysogorgia pinniformis sp.nov.and C.varians sp.nov.,two golden corals from the Caroline seamounts in the tropical Western Pacific Ocean

Two new species of Chrysogorgia Duchassaing Michelotti,1864 collected from the Caroline seamounts in the tropical Western Pacific Ocean are described.Chrysogorgia pinniformis sp.nov.belongs to Versluys' group C(Squamosae typicae) with only scales in polyp body wall and tentacles.C.pinniformis sp.nov.is characterized by large branches pinnately branched and forming multiple fans with its small branches regularly and quasi-dichotomous branched,and scales and rods present in the polyp mouth area.It is most similar to C.pinnata Cairns,2007 by the pinnate trait,but differs from the latter by its group C pattern(vs.group A,Spiculosae) and having sclerites present in the polyp mouth area(vs.absent).Chrysogorgia varians sp.nov.belongs to the Chrysogorgia group A(Spiculosae) with rods distributed in the polyp body wall and tentacles.It is characterized by warty rods and elongated scales in the tentacles,many warts and ridges on the scales,conspicuously toothed margins at the rounded ends in the pinnules,and small rods with ridge-like warts in the polyp mouth area.This species was frequent and abundant in the Caroline seamounts during our cruises and its morphological variability in growth period was obvious.The phylogenetic analyses based on mtMutS and 28 S rDNA regions supported the assignment of the new species to the genus Chrysogorgia.However,the mtMutS marker showed very limited usefulness for species delimitation and inner relationship inference of Chrysogorgia.In contrast,the 28 S rDNA showed much higher level of genetic variation,and it may be a potential barcode for this genus.In the 28 S rDNA trees,the two new species clustered together.Additionally,compilation of our data showed that 42 of 78(ca.54%) Chrysogorgia species were found in the Indo-West Pacific convergent region,indicating that this area may be a hotspot of deep-water Chrysogorgia species.     

SEASONAL HEAT BUDGET IN THE TROPICAL WESTERN PACIFIC OCEAN IN A GLOBAL GCMⅠ.GENERAL DESCRIPTION

This paper describes the large scale aspects of the seasonal surface heat budget and discusses itsmain forcing mechanisms in the tropical Western Pacific Ocean.The high-resolution generalcirculation model (Semtner & Chervin,1992)used in this study reproduced well the observed upper-layer thermal structure and circulation.It is shown that at least on the average of the study region(20°S-20°N,west boundary-160°E)the semiannual variation is a dominant signal for all heat budgetcomponents and is presumably due to the sun’s passing across the equator twice a year,but that thecomponents have substantial differences in amplitude.The local Ekman divergence in the region doesnot change significantly through the year.As a result,the change in surface heat content is roughlyhalf due to ocean-atmosphere heat exchange and half due to heat advection by remotely forced verti-cal motion.Horizontal currents do not play a significant role directly by advection,because the wat-er which enters the region is not very muc     

Seasonal heat budget in the tropical Western Pacific Ocean in a global GCM II. In five subregions

The general features of the seasonal surface heat budget in the tropical western Pacific Ocean, 20° S–20°N, western boundary −160°E, were documented by Qu (1995) using a high-resolution general circulation model (GCM, Semtner & Chervin, 1992) and existing observations. Close inspection of the smaller areas, with the whole region further partitioned into six parts, showed different mechanisms balance the seasonal surface heat budget in different parts of the region. The results of study on five subregions are detailed in this article. In the equatorial (3°S–3°N) and North Equatorial Countercurrent (3°N–9°N) region, the surface heat flux does not change significantly throughout the year, so the surface heat content is determined largely by vertical motion near the equator and roughly half due to horizontal and half due to vertical circulation in the region of the North Equatorial Countercurrent (NECC). In the other subrigions (9°N–20°N, 20°S–11°S and 11°S–3°S), however, in addition to ocean dynamics, surface heat flux can also play a major role in the seasonal variation of sea surface temperature (SST). The remotely forced baroclinic waves and their effect on the surface heat storage in the model are also investigated. Comparison with observations indicates that the model wave activities are reasonably realistic. Contribution No. 2396 from the Institute of Oceanology, Chinese Academy of Sciences. This study was supported by the Australian CSIRO Division of Oceanography and the National Natural Science Foundation of China (No. 49176255)     

Paragorgia papillata sp.nov.,a new bubblegum coral(Octocorallia:Paragorgiidae) from a seamount in the tropical Western Pacific

A new species of bubblegum coral,Paragorgia papillata sp.nov.,discovered from a seamount located on the Caroline Ridge at the water depth of 858 m,is studied using morphological and molecular approaches.The new gorgonian is white-colored,uniplanar with prominent autozooids,and measures about670-mm high and 690-mm wide.The genetic distance and phylogenetic analysis showed that P.papillata sp.nov.was closely related to P.coralloides Bayer,1993,but the former differs morphologically from the latter by its prominent calyces(diameter 2.0-4.0 mm and height 1.5-3.0 mm vs.both diameter and height about 1 mm),white cortex(vs.pink),regular 8-radiates in surface cortex(vs.mostly 8-radiate derived globular radiates) and highly ornate medullar spindles(length 185-400 μm vs.no more than 150 μm).P.papillata sp.nov.is the third known white-colored species of the genus,and the fifth species found in the tropical Western Pacific.     

Tritonia iocasica sp.nov.,a new tritoniid species from a seamount in the tropical Western Pacific(Heterobranchia:Nudibranchia)

During an expedition to a seamount at Caroline Plate in the tropical Western Pacific,a new species of Tritonia was sampled from the upper bathyal zone at depth of 970-1 262 m.This new species,Tritonia iocasica sp.nov.,represents the first tritoniid nudibranch known to feed on octocoral of the family Melithaeidae.The species is up to 120 mm in length,pinkish in color;with the rhinophoral sheath divided into several petaliform extensions;veil with,about 18 elongate digitiform processes;notal margin with17-19 pairs of secondary gills;anus located below the 5~(th) and 6~(th) secondary gills,and the genitalia below the 3~(rd) secondary gill on the right side of the body.Based on these external features,T.iocasica sp.nov.can be dearly distinguished from all previously described members of the genus.Phylogenetic analyses of two mitochondrial(COI,16 S rRNA) and a nuclear(H3) genes using Bayesian inference,maximum likelihood,and species delimitation analysis also support the separation of T.iocasica sp.nov.from its congeners.     

大尺度环流系统对西北太平洋变性TC频数影响的气候诊断分析

基于中国热带气旋年鉴资料,从气候学角度出发,对西北太平洋TC(热带气旋)发生温带变性的频数与大尺度环流系统间的关系进行了诊断和分析.研究发现变性TC多发生于夏、秋两季,通过对NCEP月平均再分析资料的500hPa高度场进行EOF分解,发现西北太平洋TC变性的频数与65°N附近强冷高压系统在夏、秋两季都存在着正相关关系,且相关性在秋季高于夏季;与30°N附近强副热带高压系统存在负相关关系,夏季副热带高压系统的作用更大;与30°N以南西北太平洋多台风活动区域的弱低压存在显著的负相关,低压越弱,对流越弱,则TC的生成数越少,其中发生变性的TC数也会减少.500hPa高度场EOF分解的第一特征向量所对应的时间函数分布在20世纪70年代中期前后出现了反号,较好地对应了变性TC年频数的年际变化趋势,70年代中期之前变性TC呈总体偏多,之后变性TC的频数总体偏少,呈明显下降趋势.     

Characteristics and biogeochemical effects of oxygen minimum zones in typical seamount areas,Tropical Western Pacific

As a serious consequence of ocean warming and increased stratification,a rapid decrease in dissolved oxygen(DO) content of the world's oceans has attracted more and more attention recently.In open oceans,the decline of DO is characterized by the expansion of oxygen minimum zones(OMZs) in the ocean interior.Vast OMZs exist within the mesopelagic zones of the Tropical Western Pacific(TWP),but have gained very little attention.In this study,we focus on characteristics of OMZs in three typical seamounts areas(named Y3,M2,and Kocebu,respectively) of the TWP.Based on distributions of DO,the OMZs of the three seamounts areas are very different in scope,thickness,and the minimum oxygen content.The significantly different characteristics of OMZs at the seamounts are mainly because they are located in regions affected by different ventilation and consumption characteristic.To quantitatively describe the intensity of OMZs,a parameter,I_(OMZ),is firstly proposed.According to this quantitative parameter,the intensity order of OMZs for the three seamounts areas is KocebuM2Y3.Potential biogeochemical effects of OMZs in the three seamounts areas are discussed using I_(OMZ).With higher I_(OMZ),the degradation of particulate organic carbon(POC) tends to be lower.Yet because of the limited data,their relationship still need more research to prove.However,if this relationship holds in global oceans,the presence of seamounts would—under climate warming with expanding OMZs—promote vertical transport of POC resulting in an enhanced biological pump.Our study provides a new way to quantitatively study the impact of OMZs on the efficiency of biological pump.     

Review on observational studies of western tropical Pacific Ocean circulation and climate

The Western Tropical Pacific(WTP) Ocean holds the largest area of warm water(28℃) in the world ocean referred to as the Western Pacific Warm Pool(WPWP),which modulates the regional and global climate through strong atmospheric convection and its variability.The WTP is unique in terms of its complex 3-D ocean circulation system and intensive multiscale variability,making it crucial in the water and energy cycle of the global ocean.Great advances have been made in understanding the complexity of the WTP ocean circulation and associated climate impact by the international scientific community since the 1960 s through field experiments.In this study,we review the evolving insight to the 3-D structure and multi-scale variability of the ocean circulation in the WTP and their climatic impacts based on in-situ ocean observations in the past decades,with emphasis on the achievements since 2000.The challenges and open que stions remaining are reviewed as well as future plan for international study of the WTP ocean circulation and climate.     

Morphology and molecular phylogeny of Paragorgia rubra sp.nov.(Cnidaria:Octocorallia),a new bubblegum coral species from a seamount in the tropical Western Pacific

A new species of bubblegum coral,Paragorgia rubra sp.nov.,discovered from a seamount at a water depth of 373 m near the Yap Trench is studied using morphological and molecular approaches.Paragorgia rubra sp.nov.is the fourth species of the genus found in the tropical Western Pacific.The new gorgonian is red-colored,uniplanar,and measures approximately 530 mm high and 440 mm wide,with autozooids distributed only on one side of the colony.Paragorgia rubra sp.nov.is most similar to P.kaupeka Sánchez,2005,but differs distinctly in the polyp ovals with large and compound protuberances(vs.small and simple conical protuberances) and the medullar spindles possessing simple conical protuberances(vs.compound protuberances).Moreover,P.rubra sp.nov.differs from P.kaupeka in the smaller length/width ratio of surface radiates(1.53 vs.1.75).The genetic distance of the mtMutS gene between P.rubra sp.nov.and P.kaupeka is 0.66%,while the intraspecific distances within Paragorgia Milne-Edwards Haime,1857 except the species P.regalis complex are no more than 0.5%,further supporting the establishment of the new species.Furthermore,the ITS2 secondary structure of P.rubra sp.nov.is also different from those of congeners.Phylogenetic analyses indicate Paragorgia rubra sp.nov.and P.kaupeka form a clade,which branched early within Paragorgia and diversified approximately 15 Mya.     

Geochemical characteristics and geological implication of ferromanganese crust from CM6 Seamount of the Caroline Ridge in the Western Pacific

Ferromanganese crusts(Fe-Mn crusts) grow very slow and can be treated as condensed stratigraphic sections recording paleo-oceanographic environmental information and local key geological events during the mineralization process.Geochronology,textures,mineralogy,and geochemistry of a Fe-Mn crust sample from the CM6 Seamount of the Caroline Ridge in the Western Pacific Ocean were analyzed by means of electron probe microanalysis and X-ray diffraction.The Fe-Mn crust shows three layers in textural characteristics from bottom to top.The lower,middle,and upper layers presence mottled,botryoidal,and columnar textures,respectively.Ferruginous vernadite,Fe hydroxide,amorphous silicate minerals,calcite,quartz,and feldspar are the main minerals of the Fe-Mn crust.Using cobalt chronometry method,the cumulative growth time of the Fe-Mn crust was determined to be 11 Ma or 25 Ma,of which25 Ma is inconsistent with other lines of age constraint brought by dating of the substrate.The co-existence of abundant silicate minerals and bioclasts in the middle and lower layers of the Fe-Mn crust diluted the ferromanganese oxide deposits,thus affected the texture,minerals,and geochemical characteristics of the Fe-Mn crust.Variations in Mn Co,Ni,and other elements content and the burial of opal-A recorded the expansion of oxygen minimum zone(OMZ) in the upper layer of the Fe-Mn crust.In addition,the highreflectivity Fe-rich laminae might indicate the surrounding volcanic activity.The Fe-Mn crust sample was determined to be hydrogenic by electron probe micro-analyzer(EPM A).The findings help us understand the geochemical characteristics of the Fe-Mn crust in the Caroline Ridge Seamount in the Western Pacific and the variations of paleo-oceanographic environment clues borne by the Fe-Mn crusts.     

Ventilation of the North Pacific Ocean: Water exchange between subtropical and tropical gyres

INTRODUCTIONIntheearly 1 980 s,ventilationtheoryemergedtopredictthehorizontalandverticalstructureofthethermocline.Thereweretwodifferentviewsonthestratifiedoceans.Thefirsttheory (RhinesandYoung,1 982 ,hereafterRY ;YoungandRhines,1 982 )proposedanunventilatedmodelinwhichonlytheuppermostlayerisexposedtothesurfaceandisforcedbythewindstress.Thesecondtheory (Luytenetal.,1 983 ,hereafterLPS)offeredaventilatedmodelwhichisclosertotheclassicalthermoclinetheoriesthanthatofthefirstone (e.g .,Nee…