东太平洋海盆一短柱状沉积物的分析与研究

本文利用＂海洋四号＂调查船,ＨＹ４－８７１航次在东太平洋海盆ＣＣ２９站取得的短柱状样,研究了沉积物岸性变化特征,分析讨论了元素在沉积物固液两相间的迁移变化及其影响因素．结果表明,在短暂的地史时期内,ＣＣ２９站沉积环境和物质来源都有变化．沉积物由过去的以陆源和火山源为主演变到现在的以陆源和生物源为主．沉积物物质来源的变化是引起ＣＣ２９站沉积物主要化学组分变化的重要原因;间隙水元素浓度的变化除与沉积环境有关外,还主要受沉积物早期成岩作用的影响．     

东太平洋多金属结核的一般特征与影响因素

本文主要阐述了东太平洋海盆国家海洋局调查区内多金属结核的物性特点、形态分区、粒级分布、矿物成分以及结核丰度、品位与生成环境因素的关系，并指出了勘探与选冶的较佳区块。     

Isotopic analyses of nitrate and nitrite from reference mixtures and application to Eastern Tropical North Pacific waters

Isotopic analyses of nitrate by the denitrifier method, and indeed by many other analytical methods, do not discriminate between nitrate and nitrite. For samples containing both chemical species, accurate isotopic analysis of nitrate requires either removal of nitrite or independent isotopic analysis of nitrite and subtraction of its contribution to the mixed isotopic signal. This study evaluates the application of a variety of available analytical approaches to the isotopic analysis of mixed nitrate and nitrite solutions, with the goal of producing accurate coupled isotopic analyses of both nitrate and nitrite. These methods are tested on mixtures of standard solutions of nitrate and nitrite, and then applied to the coupled δ¹⁵N and δ¹⁸O analyses of nitrate and nitrite in waters of the Eastern Tropical North Pacific (ETNP). Results from standard mixtures show that even for extreme values of nitrate and nitrite δ¹⁵N and δ¹⁸O, both nitrite removal by ascorbate and nitrite isotopic analysis and subtraction from the mixed isotopic signal yield nitrate δ¹⁵N and δ¹⁸O values that are close to the expected values. Application of these analyses to samples from the ETNP yielded δ¹⁵N_NO3 and δ¹⁸O_NO3 values as high as 21‰ vs. AIR and 19‰ vs. VSMOW, respectively. Conversely, very low δ¹⁵N values were observed in nitrite, with values ranging from − 7.2 to − 18.5‰ vs. AIR. Removal of nitrite from ETNP samples thus revealed differences of up to 5‰ between NO₃^- and NO₂^- + NO₃^- for both δ¹⁵N and δ¹⁸O. Moreover, the δ¹⁵N offset between co-occurring nitrate and nitrite is greater than expected from the action of denitrification alone and may provide a unique constraint on the processes involved in the cycling of nitrite in and around oxygen deficient zones. Finally, subtraction of the nitrite δ¹⁵N and δ¹⁸O from ETNP samples allows the extension of the Δ(15,18) tracer into suboxic regions containing nitrite. The magnitude and distribution of Δ(15,18) in these samples suggests an important role for nitrite reoxidation in nitrate isotope variations.     

赤道东太平洋海隆水体悬浮颗粒硫化物及其对海底热液活动的指示

基于2011年大洋一号第22次环球考察在东太平洋热液活动区采集的5个站位的77个悬浮体样品,利用扫描电镜与能谱分析相结合的方法,对悬浮颗粒硫化物颗粒的矿物形貌和物相、矿物组合特征以及空间分布进行了系统的研究,探讨了悬浮颗粒矿物组成对海底热液活动的指示作用。研究区出现了闪锌矿、纤锌矿、黄铁矿、白铁矿、磁黄铁矿、黄铜矿、方黄铜矿、铜蓝以及单质硫等多种硫化物颗粒,主要的硫化物矿物包括黄铁矿—闪锌矿—黄铜矿—磁黄铁矿,据此推断该区海底热液属于典型的高温热液流体,其温度在350℃以上。研究区不同站位间悬浮体丰度和保存程度差异明显,这与距离热液活动点远近有着较好的关系。     

Epibiotic traits of the invasive red seaweed Acanthophora spicifera in La Paz Bay,South Baja California (Eastern Pacific)

The aim of this study was to analyze the interaction of a non‐native macroalga (Acanthophora spicifera) with native macroalgae (Sargassum spp.) and sponge assemblages in a subtropical embayment of the Mexican Pacific. The intensity of A. spicifera epiphytism on the native seaweed Sargassum varied significantly over time and was inversely related to the Sargassum density and size. The higher intensity (up to 28 individuals per host plant) occurred when Sargassum was smaller and was lower in density (senescence period). The lower intensity was recorded during the growth period of Sargassum and the subsequent increase in intensity was attributed to a high fragmentation period of A. spicifera, which was evidenced by a decrease in its average size and biomass and by the presence of larger free‐floating accumulations on the subtidal zone. The facultative interaction between A. spicifera and Sargassum appears to be neutral, as no negative or positive effects were found for epiphytic or basibiont seaweeds. However, this invasive seaweed characteristically monopolizes almost all types of hard substrate, and its effects on other algae and benthic organisms should be investigated. Moreover, A. spicifera was often epizoic on epilithic sponges. This invasive seaweed was found anchored on the sponge tissue by rhizome‐like structures. In addition, free‐floating fronds of A. spicifera were frequently found carrying small pieces of the basibiont sponge in its basis (60% of them with eggs and embryos), which suggests a novel facilitation mechanism for some sponge species, as the A. spicifera epizoism could favor fragmentation, dispersal and recruitment of these invertebrates. This study shows that A. spicifera is not only a species that adapts rapidly to the new conditions of the receiving environment but, due to its epibiotic traits, it can directly interact with and influence the life histories of some native species.     

Cold seeps of the deep Gulf of Mexico: Community structure and biogeographic comparisons to Atlantic equatorial belt seep communities

Quantitative collections of tubeworm- and mussel-associated communities were obtained from 3 cold seep sites in the deep Gulf of Mexico: in Atwater Valley at 1890 m depth, in Alaminos Canyon at 2200 m depth, and from the Florida Escarpment at 3300 m depth. A total of 50 taxa of macro- and megafauna were collected including 2 species of siboglinid tubeworms and 3 species of bathymodiolin mussels. In general, the highest degree of similarity was between communities collected from the same site. Most of the dominant families at the well-characterized upper Louisiana slope seep sites of the Gulf of Mexico were present at the deep sites as well; however, there was little overlap at the species level between the upper and lower slope communities. One major difference in community structure between the upper and lower slope seeps was the dominance of the ophiuroid Ophioctenella acies in the deeper communities. The transition between upper and lower slope communities appears to occur between 1300 and 1700 m based on the number of shared species with the Barbados seeps at either end of this depth range. Seep communities of the deep Gulf of Mexico were more similar to the Barbados Accretionary Prism seep communities than they were to either the upper slope Gulf of Mexico or Blake Ridge communities based on numbers of shared species and Bray–Curtis similarity values among sites. The presence of shared species among these sites suggests that there is ongoing or recent exchange among these areas. An analysis of bathymodioline mussel phylogeography that includes new collections from the west coast of Africa is presented. This analysis also suggests recent exchange across the Atlantic equatorial belt from the Gulf of Mexico to the seeps of the West Nigerian margin.     

The structure of tuna access agreements in the Western and Central Pacific Ocean: Lessons for Vessel Day Scheme planning

The tuna industry in the Western and Central Pacific Ocean (WCPO) is one of the largest and most valuable fisheries in the world. Since the 1980s, Pacific island countries have used licensing agreements with foreign fishing interests—known as access agreements—to earn tuna-related revenue and control the environmental impacts of fishing, with only minimal success. To date, there has been little work detailing the structure of access agreements and assessing how this structure relates to economic and environmental outcomes in the sector. This article helps to fill this gap by providing an overview of various access structures and a detailed empirical assessment of how these structures are applied in access agreements between Pacific island countries and the major foreign fishing interests active in the WCPO. This analysis is placed in the context of evolving regional fisheries management structures. The study reveals that while there is no uniform formula for access agreements, each structure is subject to distinct political, economic and environmental considerations that influence outcomes for Pacific island countries. As Pacific island countries develop the mechanism to allocate fishing rights under the new Vessel Day Scheme, drawing on their long history with access agreements will assist efforts to use access to achieve policy objectives. Improved transparency will enable Pacific island countries to identify successes and problems and adapt the Vessel Day Scheme allocation mechanisms accordingly.     

Spatio‐temporal variation in density and size structure of the endangered sea cucumber Isostichopus fuscus in Huatulco National Park,Mexico

The brown sea cucumber Isostichopus fuscus (Ludwig, 1875) has been subjected to strong fishing pressure and is currently considered an endangered species by the IUCN Red List of Threatened Species. Spatial and temporal variations in density were analysed and population parameters of I. fuscus were estimated in three localities of the Southern Mexican Pacific. Density was estimated using circular transects covering a 300 m² area in each locality. Body length and weight were also measured. The mean density was 0.018 ± 0.013 individuals·m^?2, and was statistically significantly lower during summer. The mean length and weight were 22.4 ± 3.8 cm and 396 ± 130 g, respectively, and statistically significant differences were found among localities. The weight–length relationship was W = 0.28·L^1.32 and the mean relative condition index (Kn) = 1.04 ± 0.31. The von Bertalanffy growth equation was L_t = 38.7·(1–exp^(?0.4·t)). The lowest values of length, weight and age were found at Dos Hermanas, suggesting that this locality could be favorable for the settlement of larvae and recruitment and growth of juveniles. The present study is the second to estimate densities of I. fuscus and the first one to publish data on size structure and growth for the population at Bahias de Huatulco. The densities were so low in the three sampled localities that none of them would be able to support a fishery, even under a sustainable management scheme. The information collected in the present study could be helpful for management programs of the Huatulco National Park, as all the data used for these currently come mainly from the populations of I. fuscus in the Gulf of California.     

东太平洋多金属结核富钡镁锰矿细脉蛋白石层的成因机制

为探讨东太平洋CC区多金属结核中富钡镁锰矿细脉蛋白石层的成因机制,利用矿相显微镜、电子探针和ICP-OES,对蛋白石层及其周围铁锰氧化物进行了显微结构特征和化学成分特征的研究。结果表明:高反射率矿物结晶程度较好,主要由MnO组成,具有高Mn低Fe的特征,为成岩成因的钡镁锰矿。中反射率矿物结晶程度较差,主要由MnO和FeO组成,为水成成因的水羟锰矿。低反射率矿物为一种半透明矿物,主要由SiO₂组成,为生物成因的蛋白石。根据钡镁锰矿、水羟锰矿和蛋白石的成因机制,为蛋白石层及其内部钡镁锰矿细脉的形成过程建立了一个模型,共分为5个生长阶段:第1阶段,结核呈半埋藏状态在氧化环境中形成水羟锰矿;第2阶段,结核呈半埋藏状态接受SiO₂胶体的沉淀作用形成蛋白石层;第3阶段,结核呈半埋藏状态在氧化环境中形成水羟锰矿的同时,其成岩作用和蛋白石的脱水作用使蛋白石层中产生大量的裂缝;第4阶段,结核呈埋藏状态在弱氧化-还原环境中发生交代作用和重结晶作用形成钡镁锰矿;第5阶段,结核呈半埋藏状态形成水羟锰矿。     

东太平洋中国多金属结核区锰结核样品中微生物群落结构的研究

通过非培养手段研究了东太平洋中国多金属结核区ES0303站点锰结核样品中的微生物群落结构.细菌16S rRNA基因克隆文库的研究结果表明：结核内细菌种群结构复杂,微生物种类丰富且各种群丰度不一（61个OTUs）,其中变形杆菌类群为优势种群,占所有细菌克隆子比例的64%,且主要分布于β/γ-、α-和δ-等3类变形杆菌（Proteobacteria）亚群之中,占比分别为34%、18%和12%.此外还存在包括酸杆菌（Acidobacteria）,放线菌纲（Actinobacteria）,绿弯菌门（Chloroflexi）,厚壁菌门（Firmicutes）,浮霉菌门（Planctomycetes）等在内的细菌类群的分布,克隆子比例依次为9%、7%、8%、2%和5%.古菌16S rRNA基因克隆文库的研究结果表明：古菌的群落结构单一（仅12个OTUs）,全部是由泉古菌海洋类群I（crenarchaeote marine group I,MGI）组成;其中MGI-η类群最为丰富,达到44%,而MGI-α、MGI-ζ和MGI-ε类群的克隆子比例分别为25%、18%和9%,另外还发现2个新的MGI分类类群.相关克隆子的数据库比对和系统发育树分析表明,并未发现已报道的直接参与铁锰氧化还原相关类群的存在,但它们大多数与来自多金属结核来源或深海来源的不可培养微生物具有较高的同源性.进一步的分析表明,锰结核内存在相当数量的氨氧化菌、硫酸盐还原菌、酸杆菌等能够改变pH值的细菌和古菌类群的存在,意味着它们可能在锰结核的形成过程中起到重要的作用.     

西太平洋多金属结核区表层沉积物细菌群落结构及其对沉积扰动的响应

本文基于大洋第48航次在西太平洋马尔库斯 威克海山多金属结核区采集的6个表层沉积物样品的高通量测序结果,开展底栖细菌群落结构调查,共获得253012条序列,分属于41个门、85个纲、189个目、261个科和322个属。其中,变形菌纲(Proteobacteria)为优势类群,分为γ 、α 和δ 三个亚群,分别占总序列条数的24.76%、20.21%和6.48%。绿弯菌门(Chloroflexi)、酸杆菌门(Acidobacteria)、芽单胞菌门(Gemmatimonadetes)、浮霉菌门(Planctomycetes)、放线菌门(Actinobacteria)、拟杆菌门(Bacteroidetes)及硝化螺旋菌门(Nitrospirae)等类群的序列数和属种较丰富。对序列条数大于1%的OTU(operational taxonomic units)分析,共获得优势菌群23个目,包含6个优势科,10个优势属,其中,铁锰功能细菌占10.20%,主要来自交替单胞菌属(Alteromonas)(6.90%)、假交替单胞菌属(Pseudoalteromonas)(1.80%)和希瓦氏菌属(Shewanella)(1.00%)等,另外还存在参与氮和硫元素循环的种属。PICRUSt功能预测分析显示结核区细菌主要涉及信号转导、蛋白转运、原核生物固碳、群体感应、能量转换、氨基酸和嘧啶代谢等功能。BC1826站位与其他站位相比,细菌多样性较低。结合沉积柱粒度分析结果,推测BC1826站位微生物群落结构的差异与沉积扰动有关,两者具有一定的响应关系。与已有研究成果汇总对比发现,西太平洋结核区与东太平洋结核区的细菌群落组成结构有较大差异。     

Morphological description and population structure of an ophiuroid species from cobalt-rich crust seamounts in the Northwest Pacific: Implications for marine protection under deep-sea mining

Many seamounts are covered with cobalt-rich ferromanganese crusts, and are increasingly attracting interest for the potential extraction of valuable mineral resources from deep seabed environments. However, the impacts of potential mining activities on the vulnerable seamount ecosystem remain unclear. To enhance the understanding of connectivity in benthic invertebrate populations in the Northwest Pacific, several seamounts were surveyed and biological samples collected. In the present study, the ophiuroid species Ophioplinthaca defensor is reported for the first time from four deep seamounts in the Northwest Pacific, and described, providing more detailed morphological diagnosis characters. To assess the population structure of the species between and within seamounts, two mitochondrial markers (COI and 16S) were sequenced. In total, 20 haplotypes from 32 COI sequences and 8 haplotypes from 3716S sequences were recovered. The star-shaped TCS networks and non-significant pairwise population differences reveal the absence of distinct population structures between and within seamounts. In addition, the O. defensor population seemed to have undergone a demographic expansion in history. This is the first study on the genetic population structure of a benthic invertebrate from seamounts in the Northwest Pacific, and this results suggest a potentially high, long distance dispersal capacity in O. defensor between seamounts, which could inform the development of the Regional Environmental Management Plans for the cobalt-rich crust seamounts in the area.     

Management of the precious coral fishery in Taiwan: Progress and perspectives

Precious corals have been commercially exploited because of their legendary and cultural importance for many centuries in the Mediterranean and for almost one century in the Northwest Pacific. Although the precious coral fishery in Taiwan dates back to the 1920s, relevant studies on biology and ecology of resources are relatively scarce. The management of the precious coral fishery in Taiwan was officially instituted in January 2009, when data on the catch and effort of the fishery were recorded. In this study, the catch-effort data of the fishery were examined to explore the temporal and spatial patterns in composition and abundance of Corallium and Paracorallium spp. around Taiwan. A total landing of 3233.0 and 2906.8 kg precious corals were recorded for 2009 and 2010, respectively. Less than 5% of those amounts were from live colonies. A high proportion of fossilized colonies in the catch reflect the non-selective nature of the fishing gear; however, the factors that cause colonies to collapse are not exclusive to the impact of the fishery. Momo coral was dominant in the production for both years, followed by Miss coral. The total production of precious corals correlated positively with fishing efforts, while a weak relationship was found between the production of live colonies and fishing efforts. The fishing efforts mainly aggregated in designated fishing ground A (DFG-A) for both years, while the production of live colonies mainly occurred in DFG-E. The monthly occurrence rate of live colonies decreased over the past 2 years. Although fluctuating significantly, the CPUE of dominant species exhibited an apparent decreasing pattern. High aggregation of the fishing efforts in specific regions and low numbers of live colonies in the production should be carefully taken into account when amending management regulations in the future. The establishment of marine protected areas, in addition to the strict controls that already apply, should be considered to not only sustain the population structure of the sessile animals but also their function in the marine ecosystem.     

Lipid and 13C signatures of submicron and suspended particulate organic matter in the Eastern Tropical North Pacific: Implications for the contribution of Bacteria

The contribution of bacterial biomass to total particulate organic matter (POM) in the ocean, including exported material, is poorly constrained. To examine potential signatures for the presence and export of bacterioplankton and their detrital remains, here we provide a detailed compound-specific ¹³C characterization of fatty acids from membrane polar lipids obtained from a water column profile in the Eastern Tropical North Pacific. POM of submicron size (0.2–0.7 μm; “X-POM”) was sampled and analyzed separately from the size class typically collected as “suspended” POM (0.7–53 μm; “L-POM”). The distributions of polar head group classes, specific fatty acid side chains, and natural ¹³C contents all vary, both between particle size classes and with depth in the water column. In general, the polar lipids in submicron material – and by inference, lipids of bacterial origin – have higher ¹³C content than polar lipids from larger POM and are equally abundant. Lipid signatures from the photic zone appear to be partially conserved in the suspended pool during transit down the water column. However, bacterial heterotrophy and possibly chemoautotrophy partially overprint these surface signatures. In addition, active metabolisms in the oxygen minimum zone (OMZ) appear to mediate the disaggregation of POM transported from the surface, thus adding complexity to the pathways of mid-water carbon flux and providing additional organic substrates to the OMZ and below. This “substrate injection” may provide important fuel for the denitrification and anammox reactions. Finally, examination of ¹³C content in polar lipids provides a basis for new interpretation of depth-related variations in δ¹³C values of bulk suspended POM.     

东太平洋赤道海域茎柔鱼小型群体资源分布及其渔场环境特征

茎柔鱼(Dosidicus gigas)是我国远洋渔业的重要捕捞对象。当前针对茎柔鱼渔场分布及其与环境关系的研究多集中于秘鲁海域,针对赤道海域茎柔鱼特定种群小型群体资源分布及其渔场环境特征研究较少。根据2019年12月至2020年2月茎柔鱼生物学数据,2019年12月至2020年4月生产和环境数据,运用胴长-体重关系拟合、地统计插值、广义可加模型(GAM)探究其资源分布及渔场环境状况。结果表明：东太平洋赤道海域茎柔鱼胴长范围为136~407 mm,体重范围为117~1557 g；2019年12月至2020年4月各月渔获量呈先增加后减小趋势,2月渔获量最高；CPUE曲线除2月增加外,总体呈下降趋势；渔场集中分布于0°~3°S、105°W~114°W海域,不同月份渔场重心经向变化明显；渔场最适SST范围是24.5~25.5 °C,最适Chl-a范围是0.16~0.20 mg/m3,月份是影响茎柔鱼CPUE的主要因子。研究表明：该海域茎柔鱼渔获主要为小型群体；小型群体生长发育期(2–3月)对渔场分布有重要影响,生长发育期前茎柔鱼集群度高,生长发育期后逐渐分散活动；单一影响因子与茎柔鱼CPUE相关性不显著,综合考虑其他环境因素及其交互影响是今后的研究方向。     

基于海表温度和海面高度的东太平洋大眼金枪鱼渔场预测

开展东太平洋大眼金枪鱼(Thunnus obesus)渔场预报技术研究,建立基于多环境因子渔场预报模型,将对该资源的高效开发和利用具有重要的意义。作者根据2009~2011年东太平洋海域(20°N~35°S、85°W~155°W)延绳钓生产统计数据,结合海洋遥感获得的表温(SST)和海面高度(SSH)的数据,运用一元非线性回归方法,以渔获量为适应性指数,按季度分别建立了基于SST和SSH的大眼金枪鱼栖息地适应性指数,采用算术平均法获得基于SST和SSH环境因子的栖息地指数综合模型,并用2012年各月实际作业渔场进行验证。研究结果显示,大眼金枪鱼渔场多分布在SST为24~29℃、SSH为0.4~0.8 m的海域。指数模型较好地拟合了因子适应性曲线(P0.05)。基于栖息地指数的2012年大眼金枪鱼中心渔场预报准确性平均达63%,可为金枪鱼延绳钓渔船寻找中心渔场提供指导。     

Changing structure of benthic foraminiferal communities: implications from experimentally grown assemblages from coastal Georgia and Florida,USA

Environmental changes such as ocean warming or sea‐level rise have a profound impact on shallow‐water coastal environments. Benthic foraminifera have long been successfully used as indicators for ecologic responses. The propagule method is a useful tool to evaluate the reactions of entire assemblages of foraminifera when exposed to different environmental conditions. Here we present results from growth experiments of foraminiferal assemblages from three sites in coastal Georgia and Florida (USA) under different temperatures (18, 24 and 30 °C) and salinities (15 and 35). Results show that assemblages grown at the higher temperatures had greater abundances of foraminifera, whereas salinity was the primary factor in shaping the composition of the experimentally grown assemblages from the three sites. We also show that experimentally grown assemblages contain high numbers of ‘exotic’ species that result from successful propagule recruitment from outside of the original environments (e.g. the open shelf). Overall, opportunistic and previously termed ‘pioneer species’ proved to be the most successful constituents of the experimental assemblages, showing that reactions of foraminiferal assemblages to environmental changes can appear remarkably quickly (e.g. in the course of several weeks). Our observations on the faunal reactions to different temperatures and salinities indicate that ongoing environmental alterations of coastal areas will likely result in significant changes in the shallow‐water foraminiferal assemblages of the coasts of Georgia and Florida. As such, our study provides general insights into the ecologic effects of current climate change.     

Structural patterns and tectonic history of the Bauer microplate, Eastern Tropical Pacific

The Bauer microplate was an independent slab of oceanic lithosphere that from 17 Ma to 6 Ma grew from 1.4 × 10⁵ km² to 1.2 × 10⁶ km² between the rapidly diverging Pacific and Nazca plates. Growth was by accretion at the lengthening and overlapping axes of the (Bauer-Nazca) Galapagos Rise (GR) and the (Pacific-Bauer) East Pacific Rise (EPR). EPR and GR axial propagation to create and rapidly grow the counter-clockwise spinning microplate occurred in two phases: (1) 17–15Ma, when the EPR axis propagated north and the GR axis propagated south around a narrow (100- to 200-km-wide) core of older lithosphere; and (2) 8–6 Ma, when rapid northward propagation of the EPR axis resumed, overlapping ∼400 km of the fast-spreading Pacific-Nazca rise-crest and appending a large (200- to 400-km-wide) area of the west flank of that rise as a ‘northern annex’ to the microplate. Between 15 and 8 Ma the microplate grew principally by crustal accretion at the crest of its rises. The microplate was captured by the Nazca plate and the Galapagos Rise axis became extinct soon after 6 Ma, when the south end of the Pacific-Bauer EPR axis became aligned with the southern Pacific-Nazca EPR axis and its north end was linked by the Quebrada Transform to the northern Pacific-Nazca EPR axis. Incomplete multibeam bathymetry of the microplate margins, and of both flanks of the Pacific-Bauer and Bauer-Nazca Rises, together with archival magnetic and satellite altimetry data, clarifies the growth and (counter-clockwise) rotation of the microplate, and tests tectonic models derived from studies of the still active, much smaller, Easter and Juan Fernandez microplates. Our interpretations differ from model predictions in that Euler poles were not located on the microplate boundary, propagation in the 15–8 Ma phase of growth was not toward these poles, and microplate rotation rates were small (5°/m.y.) for much of its history, when long, bounding transform faults reduced coupling to Nazca plate motion. Some structures of the Bauer microplate boundary, such as deep rift valleys and a broad zone of thrust-faulted lithosphere, are, however, similar to those observed around the smaller, active microplates. Analysis of how the Bauer microplate was captured when coupling to the Pacific plate was reduced invites speculation on why risecrest microplates eventually lose their independence.     

Power Europe: EU and the illegal,unreported and unregulated tuna fisheries regulation in the West and Central Pacific Ocean

Illegal, unreported and unregulated (IUU) fishing activities are widely considered a main cause of unsustainable fisheries across the globe. The EU has taken a leading role in the fight against IUU fishing, using both its market and normative power to advance its EU IUU Regulation (no. 1005/2008) and wider fisheries sustainability agenda outside its territory. This paper examines how successful the EU has been in using its market and normative power to influence regulatory strategies and frameworks governing tuna fisheries in the Pacific Islands region of the Western Pacific Ocean. The results indicate that while the market power of the EU remains an influential factor, the diminishing normative power of the EU in WCPO is weakening any attempts to implement its IUU fishing regulation and Pacific Island nations have promoted their own regulatory agenda. We conclude that the changing asymmetries between market and normative power has led to a differentiated geography of regulatory uptake, and while market power will remain a dominant strategy for the EU, normative power, when exercised should focus on cooperation rather than ‘teaching’ the benefits of an EU regulatory approach.     

The three-dimensional structure and seasonal variation of the North Pacific meridional overturning circulation

The three-dimensional structure and the seasonal variation of the North Pacific meridional overturning circulation (NPMOC) are analyzed based on the Simple Ocean Data Assimilation data and Argo profiling float data.The NPMOC displays a multi-cell structure with four cells in the North Pacific altogether.The TC and the STC are a strong clockwise meridional cell in the low latitude ocean and a weaker clockwise meridional cell between 7°N and 18°N,respectively, while the DTC and the subpolar cell are a weaker ...