Generation mechanism of an alongshore bar on a sandy beach slope

A model explaining the mechanism of alongshore bar formation from the point of view of the sediment balance in the surf zone is considered. A cloud of suspended matter that appears during wave breaking is transported shoreward and simultaneously sediments forming a vertical material flux directed to the bottom (S). Simultaneously, an undertow generates a horizontal offshore flux of suspended matter q _x . Under these conditions, the sediment balance is determined by the equality of the flux -S and the gradient dq _x /dx. The bottom profile satisfying the balance equation is a bar profile with the crest at the point of the flux maximum -S. The model predicts a concave profile of the seaside slope and a concave-convex profile of the slope in the trough. A conclusion is reached on the basis of the calibration and verification of the model based on the field data that the suggested mechanism manifests itself differently in the outer and inner zones of the coastal zone. In the inner zone, the horizontal size of the bar is determined by the length of short wind waves, while, in the outer one, it is determined by the length of the infragravity waves related to the groups of short waves. It is shown that the model can be applied to estimate the parameters of the largest bar in the inner part of the coastal zone.     

Evaluation of spatial distribution of turbulent mixing in the central Pacific

A long-term mean turbulent mixing in the depth range of 200–1000 m produced by breaking of internal waves across the middle and low latitudes (40°S–40°N) of the Pacific between 160°W and 140°W is examined by applying fine-scale parameterization depending on strain variance to 8-year (2005–2012) Argo float data. Results show that elevated turbulent dissipation rate (ε) is related to significant topographic regions, along the equator, and on the northern side of 20°N spanning to 24°N throughout the depth range. Two patterns of latitudinal variations of ε and the corresponding diffusivity (K_ρ) for different depth ranges are confirmed: One is for 200–450 m with significant larger ε and K_ρ, and the maximum values are obtained between 4°N and 6°N, where eddy kinetic energy also reaches its maximum; The other is for 350–1000 m with smaller ε and K_ρ, and the maximum values are obtained near the equator, and between 18°S and 12°S in the southern hemisphere, 20°N and 22°N in the northern hemisphere. Most elevated turbulent dissipation in the depth range of 350–1000 m relates to rough bottom roughness (correlation coefficient?=?0.63), excluding the equatorial area. In the temporal mean field, energy flux from surface wind stress to inertial motions is not significant enough to account for the relatively intensified turbulent mixing in the upper layer.     

Seasonal variations in the nitrogen isotopic composition of settling particles at station K2 in the western subarctic North Pacific

Intensive observations using hydrographical cruises and moored sediment trap deployments during 2010 and 2012 at station K2 in the North Pacific Western Subarctic Gyre (WSG) revealed seasonal changes in δ ¹⁵N of both suspended and settling particles. Suspended particles (SUS) were collected from depths between the surface and 200 m; settling particles by drifting sediment traps (DST; 100–200 m) and moored sediment traps (MST; 200 and 500 m). All particles showed higher δ ¹⁵N values in winter and lower in summer, contrary to the expected by isotopic fractionation during phytoplankton nitrate consumption. We suggest that these observed isotopic patterns are due to ammonium consumption via light-controlled nitrification, which could induce variations in δ ¹⁵N(SUS) of 0.4–3.1 ‰ in the euphotic zone (EZ). The δ ¹⁵N(SUS) signature was reflected by δ ¹⁵N(DST) despite modifications during biogenic transformation from suspended particles in the EZ. δ ¹⁵N enrichment (average: 3.6 ‰) and the increase in C:N ratio (by 1.6) in settling particles suggests year-round contributions of metabolites from herbivorous zooplankton as well as TEPs produced by diatoms. Accordingly, seasonal δ ¹⁵N(DST) variations of 2.4–7.0 ‰ showed a significant correlation with primary productivity (PP) at K2. By applying the observed δ ¹⁵N(DST) vs. PP regression to δ ¹⁵N(MST) of 1.9–8.0 ‰, we constructed the first annual time-series of PP changes in the WSG. This new approach to estimate productivity can be a powerful tool for further understanding of the biological pump in the WSG, even though its validity needs to be examined carefully.     

南极西北威德尔海上层海洋湍流混合研究

Turbulent mixing in the upper ocean(30-200 m) of the northwestern Weddell Sea is investigated based on profiles of temperature,salinity and microstructure data obtained during February 2014.Vertical thermohaline structures are distinct due to geographic features and sea ice distribution,resulting in that turbulent dissipation rates(ε) and turbulent diffusivity(K) are vertically and spatially non-uniform.On the shelf north of Antarctic Peninsula and Philip Ridge,with a relatively homogeneous vertical structure of temperature and salinity through the entire water column in the upper 200 m,both ε and K show significantly enhanced values in the order of O(10~(-7))-O(10~(-6)) W/kg and O(10~(-3))-O(10~(-2)) m~2/s respectively,about two or three orders of magnitude higher than those in the open ocean.Mixing intensities tend to be mild due to strong stratification in the Powell Basin and South Orkney Plateau,where s decreases with depth from O(10~(-8)) to O(10~(-9)) W/kg,while K changes vertically in an inverse direction relative to s from O(10~(-6)) to O(10~(-5)) m~2/s.In the marginal ice zone,K is vertically stable with the order of10~(-4) m~2/s although both intense dissipation and strong stratification occur at depth of 50-100 m below a cold freshened mixed layer.Though previous studies indentify wind work and tides as the primary energy sources for turbulent mixing in coastal regions,our results indicate weak relationship between K and wind stress or tidal kinetic energy.Instead,intensified mixing occurs with large bottom roughness,demonstrating that only when internal waves generated by wind and tide impinge on steep topography can the energy dissipate to support mixing.In addition,geostrophic current flowing out of the Weddell Sea through the gap west of Philip Passage is another energy source contributing to the local intense mixing.     

Phylogenetic relationship between symbionts of tubeworm <Emphasis Type="Italic">Lamellibrachia satsuma</Emphasis> and the sediment microbial community in Kagoshima Bay

Vestimentiferan tubeworms acquire their symbionts through horizontal transmission from the surrounding environment. In the present study, we constructed a 16S rRNA gene clone library to investigate the phylogenetic relationship between diverse microbes in the sediment and symbiotic bacteria in the trophosome of the tubeworm, Lamellibrachia satsuma, from Kagoshima Bay, Japan. Two symbiotic bacterial phylotypes belonging to the classes γ- and ε-Proteobacteria were found from this tubeworm trophosome. They were very closely related to the symbionts of several other marine invertebrates. The most predominant bacteria in the sediment were ε-Proteobacteria. A broad diversity of bacteria belonged to non-proteobacterial phyla such as Planctomycetes, Acidobacteria, and Chloroflexi was observed. The presence of sulfur oxidizers (i.e., ε-Proteobacteria and γ-Proteobacteria) and sulfur reducers (i.e., δ-Proteobacteria) may play a significant role in the sulfur cycle in these habitats and provide multiple sources of nutrition to the cold-seep communities. Closely related clones of ε-Proteobacteria symbiont in the species level and of γ-Proteobacteria symbiont in the genus level were found in the surrounding sediment. The similarity of symbiont clones of L. satsuma with other symbionts and free-living bacteria suggests the possibility of opportunistic symbiosis in ε-Proteobacteria and the co-evolution of γ-Proteobacteria having occurred after symbiosis with the tubeworms.     

In situ pore-pressure evolution during dynamic CPT measurements in soft sediments of the western Baltic Sea

We present in situ strength and pore-pressure measurements from 57 dynamic cone penetration tests in sediments of Mecklenburg (n?=?51), Eckernförde (n?=?2) and Gelting (n?=?4) bays, western Baltic Sea, characterised by thick mud layers and partially free microbial gas resulting from the degradation of organic material. In Mecklenburg and Eckernförde bays, sediment sampling by nine gravity cores served sedimentological characterisation, analyses of geotechnical properties, and laboratory shear tests. At selected localities, high-resolution echo-sounder profiles were acquired. Our aim was to deploy a dynamic cone penetrometer (CPT) to infer sediment shear strength and cohesion of the sea bottom as a function of fluid saturation. The results show very variable changes in pore pressure and sediment strength during the CPT deployments. The majority of the CPT measurements (n?=?54) show initially negative pore-pressure values during penetration, and a delayed response towards positive pressures thereafter. This so-called type B pore-pressure signal was recorded in all three bays, and is typically found in soft muds with high water contents and undrained shear strengths of 1.6–6.4 kPa. The type B signal is further affected by displacement of sediment and fluid upon penetration of the lance, skin effects during dynamic profiling, enhanced consolidation and strength of individual horizons, the presence of free gas, and a dilatory response of the sediment. In Mecklenburg Bay, the remaining small number of CPT measurements (n?=?3) show a well-defined peak in both pore pressure and cone resistance during penetration, i.e. an initial marked increase which is followed by exponential pore-pressure decay during dissipation. This so-called type A pore-pressure signal is associated with normally consolidated mud, with indurated clay layers showing significantly higher undrained shear strength (up to 19 kPa). In Eckernförde and Gelting bays pore-pressure response type B is exclusively found, while in Mecklenburg Bay types A and B were detected. Despite the striking similarities in incremental density increase and shear strength behaviour with depth, gas occurrence and subtle variations in the coarse-grained fraction cause distinct pore-pressure curves. Gaseous muds interbedded with silty and sandy layers are most common in the three bays, and the potential effect of free gas (i.e. undersaturated pore space) on in situ strength has to be explored further.     

Effect of Mercury Chloride on the Chlorophyl <Emphasis Type="Italic">a</Emphasis> and Pheophytin Content in Marine Microalgae: Measuring the Flow of Autotrophic Phytoplankton Using Sediment Traps Data

The present work aimed to study the influence of mercuric chloride (HgCl₂) on pigment content (chlorophyll a and pheophytin) in sediment traps on the basis of experimental data. The marine microalgal cultures of Conticribra weissflogii (Mediophyceae), Tetraselmis viridis (Chlorodendrophyceae), Amphidinium carterae (Dinophyceae), Nannochloropsis sp. (Eustigmatophyceae) were used. The obtained results revealed that the influence of mercury on pigment content as well as on photosynthetic activity was different in different species. The considerable decrease in phytopigments content was observed in Amphidinium carterae and Conticribra weissflogii, while the proportion of pheophytin increased. The pigment content of Tetraselmis viridis was not different from the control line, while for Nannochloropsis sp. the increase in pigment concentration was noticed. The complete immediate inhibition of photosynthetic activity was observed in Conticribra weissflogii, Tetraselmis viridis, Amphidinium carterae, while Nannochloropsis sp. responded only after 24 h of exposition. The pigment degradation rate was almost the same for diatoms and dinoflagellates. The equation for estimating the phytopigments content in sediment traps, that takes into consideration the exposition time, is proposed.     

A Baseline Assessment of Coral Reef in Malacca Straits,Malaysia

Coral reefs along the Malacca Straits (MS) are poorly developed mainly due to turbidity and sedimentation. This study describes the health status and community structure of the corals in Cape Rachado, West Coast of Peninsular Malaysia (WCPM), utilizing the Coral Video Transect (CVT) technique. All the survey transects were categorized as ‘fair’ coral conditions (27.39 ± 5.41%–48.56 ± 18.96%) with the reef floor mainly covered by corals and sediment. Twelve families of coral comprised of 25 distinct genera were identified. Coral communities were differentiated into four clusters with each being predominated by Galaxea, Diploastrea, Fungia and Pectinia respectively. Among all, Pectinia is the most spectacular genera and dominated the survey area. Along the MS, Favia, Favites and Porites are commonly found while Porites and Pectinia dominated the reefs. Low coral cover and diversity was recorded in MS as compared to the reefs in the South China Sea (SCS). The most prominent results include changes in the dominant coral from Porites to Pectinia while some species such as Acropora were absent from the study area. Based on the presented data, the reef in the study area was predominantly occupied by sediment and the coral communities were formed by a species with a high tolerance to turbidity and sedimentation.     

Features of the atmospheric boundary layer block for three versions of the WAM wind wave model

The estimated characteristics of the atmospheric boundary layer, obtained by the simulation of wind wave fields using three versions of the WAM numerical model are compared with the well-known empirical dependences of drag coefficient C _d on wind speed U ₁₀ and wave age A, as well as with the dependence of dimensionless roughness height z _n on inverse wave age u*/с р. Calculations carried out for several years in the areas of the Pacific and Indian oceans, based on the ERA-interim and CFSR wind reanalyses have shown good agreement between the model and empirical dependences C _d (U ₁₀) and C _d (A). The range of estimated variability for z _n (u*/с _р ) has been found to be significantly less than empirical. It has been also found that estimated values of wind speed U _10W (t) are overestimated from 5 to 10% in all versions of WAM models compared with the input wind reanalysis U _10R (t) at the moments of appearance maximum values of wind U _10R (t). The reasons for the established features of the WAM model and their dependence on the model version are discussed.     

Potential for heavy metal (copper and zinc) removal from contaminated marine sediments using microalgae and light emitting diodes

The effects of monochromatic (blue, yellow and red LED) and mixed wavelengths (fluorescent lamp) on the adsorption and absorption of Cu and Zn by Phaeodactylum tricornutum, Nitzschia sp., Skeletonema sp., and Chlorella vulgaris were investigated. In addition, we confirmed the potential of microalgae for phytoremediation of these heavy metals from contaminated marine sediment by using microcosm experiments that incorporated LEDs and semipermeable membrane (SPM) tube containing microalgae. Among the four microalgae, C. vulgaris grown under red LED exhibited the highest Cu and Zn removal with values of 17.5 × 10^-15 g Cu/cell and 38.3 × 10^-15 g Zn/cell, respectively. Thus, C. vulgaris could be a useful species for phytoremediation. In the microcosm experiments with SPM containing C. vulgaris, the highest Cu and Zn removal from sediment and interstitial water showed under red LED. Therefore, phytoremediation using LED and SPM tube containing microalgae could be utilized as an eco-friendly technique for remediating contaminated marine sediment.     

Predicting bed form roughness: the influence of lee side angle

Flow transverse bedforms (ripples and dunes) are ubiquitous in rivers and coastal seas. Local hydrodynamics and transport conditions depend on the size and geometry of these bedforms, as they constitute roughness elements at the bed. Bedform influence on flow energy must be considered for the understanding of flow dynamics, and in the development and application of numerical models. Common estimations or predictors of form roughness (friction factors) are based mostly on data of steep bedforms (with angle-of-repose lee slopes), and described by highly simplified bedform dimensions (heights and lengths). However, natural bedforms often are not steep, and differ in form and hydraulic effect relative to idealised bedforms. Based on systematic numerical model experiments, this study shows how the hydraulic effect of bedforms depends on the flow structure behind bedforms, which is determined by the bedform lee side angle, aspect ratio and relative height. Simulations reveal that flow separation behind bedform crests and, thus, a hydraulic effect is induced at lee side angles steeper than 11 to 18° depending on relative height, and that a fully developed flow separation zone exists only over bedforms with a lee side angle steeper than 24°. Furthermore, the hydraulic effect of bedforms with varying lee side angle is evaluated and a reduction function to common friction factors is proposed. A function is also developed for the Nikuradse roughness (k _s), and a new equation is proposed which directly relates k _s to bedform relative height, aspect ratio and lee side angle.     

Morphological identification of <Emphasis Type="Italic">Alexandrium</Emphasis> species (Dinophyceae) from Jinhae-Masan Bay,Korea

Outbreaks of paralytic shellfish poisoning (PSP) and dense blooms caused by Alexandrium species in Jinhae-Masan Bay, Korea have been nearly annual events for many years. However, excluding some Alexandrium species responsible for PSP, there are no critical reports on the morphology of Alexandrium species in this bay. To identify the Alexandrium species based on detailed morphological features, vegetative cells collected water samples and established by the incubation of resting cysts isolated from sediment trap samples were analyzed. Four species of Alexandrium were identified: Alexandrium affine, A. fundyense, A. catenella, and A. insuetum. Morphological features of these species were basically consistent with those outlined in previous studies. However, the ventral pore and the connecting pore on the sulcal plate, which have been accepted as diagnostic characteristics for the identification of A. fundyense and A. catenella, need to be reevaluated, indicating that useful morphological features for identifying these two species should be recommended to avoid confusion in the classification of species in genus Alexandrium.     

Fine-scale Microbial Communities Associated with Manganese Nodules in Deep-sea Sediment of the Korea Deep Ocean Study Area in the Northeast Equatorial Pacific

Despite its potential significance for industrial utilization, any activities associated with the mining of manganese (Mn) nodules might have substantial impacts on benthic ecosystems. Because microorganisms respond quickly to changing environmental conditions, a study of microbial communities provides a relevant proxy to assess possible changes in benthic ecosystems associated with mining activities. We investigated fine-scale microbial community composition and diversity inside and on the surface of Mn nodules and in nearby deep-sea sediments in the Korea Deep Ocean Study (KODOS) area located in the Clarion-Clipperton Fracture Zone (CCFZ) of the northeast equatorial Pacific. Although microbial cell density was lower within nodules (3.21 × 10⁶ cells g^-1) than in sediment (2.14 × 10⁸ cells g^-1), nodules provided a unique habitat for microorganisms. Manganese-oxidizing bacteria including Hyphomicrobium and Aurantimonas in Alphaproteobacteria and Marinobacter in Gammaproteobacteria were abundant in nodules, which implied that these bacteria play a significant role in nodule formation. In contrast, Idiomarina in Gammaproteobacteria and Erythrobacter and Sulfitobacter in Alphaproteobacteria were abundant in sediments. Meanwhile, Thaumarchaeota, a phylum that consists of ammonia-oxidizing chemolithoautotrophs, were the predominant archaeal group both in nodules and sediment. Overall, microbial communities in Mn nodules were unique compared to those observed in sediments. Furthermore, the phylogenetic composition of microorganisms in the KODOS area was distinguishable from that in the nodule provinces claimed by China and Germany in the CCFZ and nodule fields in the central South Pacific Gyre, respectively.     

Features of the spatial distribution of phytoplankton in Nhatrang Bay of the South China Sea during the rainy season

The species composition, phytoplankton abundance, and relative yield of the variable fluorescence (F _v /F _m ) were determined in the mesotrophic Nhatrang Bay in October–November of 2004. The species diversity (250 taxonomic units) and heterogeneity of the phytoplankton structure were high. With respect to the number of species and their abundance, diatoms prevailed. In selected parts of the bay, dinoflagellates dominated. The mean biomass in the water column under 1 m² (B _t ) varied from 2.3 to 64.4 mg C/m³ being 31.0 mg C/m³ on average. The values of B _t were the lowest at the stations nearest to the river mouth. Seaward, B _t increased. The values of B _t increased with depth at some stations and decreased at others. In the surface sea layers, the biomass was lower than that in the underlying waters. The values of F _v /F _m ranged from 0.10 to 0.64 (at a mean value of 0.49). The lowest values of F _v /F _m were observed in the area close to the seaport. Over the greater part of the bay, the values of F _v /F _m were higher than 0.47. Such values are indicative of the relatively high potential photosynthetic activity of the phytoplankton. The abundance and species diversity were higher than those in the dry season (March–April).     

“海参-对虾”混养海水池塘的食物网结构及营养层级研究

The food sources of aquacultured Apostichopus japonicus and the trophic levels of organisms in a sea cucumber(A. japonicus) and prawn(Penaeus japonica) polyculture system in a saltwater pond in Zhuanghe, Liaoning Province were examined using carbon and nitrogen stable isotopes. Across organisms, δ13C ranged from(–25.47±0.20)‰ to(–16.48±0.17)‰(mean±SD), and δ15N ranged from(4.23±0.49)‰ to(12.44±0.09)‰. The δ13C and δ15N contents of A. japonicus, P. japonica and Fenneropenaeus chinensis were comparatively higher than those of other organisms. Values of δ13C and δ15N revealed that P. japonica, Hemigrapsus sanguineus and Neomysis japonica comprised the largest component of the diet of A. japonicus. The mean trophic level of the organisms in this saltwater pond polyculture system was(2.75±0.08). P. japonica, A. japonicus, F. chinensis,Synechogobius hasta and Neomysis japonica were in the 3rd trophic level(2–3); jellyfish, H. sanguineus and zooplankton were in the 2nd trophic level(1–2); and Enteromorpha prolifera, benthic microalgae, periphyton and suspended matter primarily consisting of phytoplankton, bacteria and humus were in the primary trophic level(0–1).     

风暴过程中潮滩悬沙浓度和悬沙输运的变化及其动力机制——以长江三角洲南汇潮滩为例

悬沙浓度是淤泥质海岸重要的环境指标。为探讨潮滩悬沙浓度和悬沙输运对风暴事件的响应过程及其动力机制,于2014年9月"凤凰"台风过境前、中、后在长江三角洲南汇潮滩进行了现场观测,获得同步高分辨率的水深、波高、近底流速和浊度剖面时间序列(9个潮周期)。结果表明,风暴中平均和最大波高、波-流联合底床剪切应力、悬沙浓度和悬沙输运率可比平静天气高数倍;风暴期间高潮位低流速阶段悬沙沉降导致近底发育数十厘米厚的浮泥层(悬沙浓度大于10 g/L)。研究认为风暴事件中淤泥质海岸悬沙浓度和悬沙输运的剧烈变化其根本动力机制是风暴把巨大能量传递给近岸水体,进而显著增大波-流联合底床剪切应力,导致细颗粒泥沙再悬浮。     

东印度洋5种缘毛类纤毛虫(钟虫属和聚缩虫)水平分布初次报道

腹壁纤毛虫是一种附着在浮游动物上的原生生物,尤其是附着在桡足类和甲壳类上的。而缘毛虫是可以以自由或寄生的形式在世界各沿海地区和港湾处被发现。本研究首次对东印度洋表层至200 m深海域的缘毛类纤毛虫以及其水平分布展开了研究。根据纤毛虫的形态、纤毛结构和茎的形态等的特征,在2014年4月10日至5月13日东印度洋航次的浮游生物拖网样品中鉴定出了五种富腹纤毛虫,海洋钟形虫Vorticella oceanica、交替聚缩虫Zoothamnium alternans、阿拉聚缩虫Zoothamnium alrasheidi、远洋聚缩虫Zoothamnium pelagicum和海洋聚缩虫Zoothamnium marinum。并通过光显微镜和扫描显微镜拍摄的照片,说明了其形态、尺寸和特征。研究结果表明,海洋钟形虫和远洋聚缩虫的分布与硅藻（如,密聚角毛藻Chaetoceros coarctatus）和桡足类（如,短角长腹剑水蚤Oithona brevicornis）等寄主有关,也包括甲藻（如,三角角藻Ceraitum tripose）周围的一些个体。这些附着纤毛虫的分布在东印度洋海域东南区以海洋钟形虫、远洋聚缩虫和海洋聚缩虫为主,而在孟加拉湾北部则有大量的阿拉聚缩虫。这种分布的变化可能是与寄主的分布有关,如桡足类（短角长腹剑水蚤）和硅藻（密聚角毛藻）的分布影响。     

东印度洋现生浮游有孔虫

A brief morphometric study of the recent planktonic foraminifera in the eastern Indian Ocean was provided with the taxonomic key to species,synonyms,SEM microphotographs of shells and chamber arrays.By recent classification,currently 20 species representing 13 genera and 6 families(Canderinidae,Heterohelicoidae,Hedbergellidae,Higerigerinoidae,Globigerinoidae,and Globorotaloidae)identified from the planktonic material of the eastern Indian Ocean up to a depth of 200 m.Their distribution in water(0–200 m)also reports on the new range of expansion in the eastern Indian Ocean,with Dentigloborotalia anfracta,Hastigerina pelagica,Streptochilus globigerus,Globigerinella calida,Globigerinella adamsi,Orcadia reidelii,Tenuitella parkerae,Tenuitella compressa,reported for the first time in this study area.In general,only around 50 planktonic species are valid worldwide,more specifically the species,e.g.,H.pelagica,G.calida,G.adamsi,S.globigerus,O.riedeli,T.parkerae,T.compressa,which occur in the eastern Indian Ocean to fill the the paucity of the recent regional taxonomic literature and the problematic identification from the eastern Indian Ocean.This work aims to bridge this gap and help scientists,managers,educators and students to identify plankton foraminifers by using species notes and images.     

Oceanic processes of upper ocean heat content associated with two types of ENSO

The spatiotemporal variability of equatorial Pacific upper ocean heat content (HC) and subsurface heat during two types of El Niño-Southern Oscillation (ENSO), namely eastern and central Pacific (EP and CP) types, is investigated using subsurface ocean heat budget analysis. Results show that HC tendencies during both types of ENSO are mainly controlled by oceanic heat advection beneath the mixed layer to the thermocline, and the role of net surface heat flux can be neglected. The most important three terms are the zonal and vertical advections of anomalous heat by climatological currents (QU ₀ T′, QW ₀ T′) and zonal advection of climatological heat by anomalous current (QU′T ₀). The large contribution of QU ₀ T′ extends from west to east along the equatorial Pacific. The considerable contribution of QU′T ₀ is confined to the east of 160°W, and that of the QW ₀ T′ is observed in the central Pacific between 180°E and 120°W. In particular, a major contribution of QW ₀ T′ is also observed in the far eastern Pacific east of 100°W during EP ENSO. There is also a small contribution from meridional advection of climatological heat by anomalous current (QV′T ₀). In contrast, the meridional advection of anomalous heat by climatological currents (QV ₀ T′) and vertical advection of climatological heat by anomalous current (QW′T ₀) are two damping factors in the HC tendency, with the former dominating. Differences in spatial distribution of the heat advection associated with the two types of ENSO are also presented. We define a warm water heat index (WWH) as integrated heat content above 26 kg m^?3 potential density (26σ _? ) isopycnal depth within 130°E–80°W and 5°S–5°N. Further examination suggests that the recharge–discharge of WWH is involved in both types of El Niño, though with some differences. First, it takes about 42 (55) months for the evolution of a recharge–discharge cycle during an EP (CP) ENSO. Second, the EP El Niño event peaks during the discharge phase, 7–8 months after the recharge time. The CP El Niño peaks during the recharge phase, 4–5 months before the recharge time. The locations of HC anomalies in the El Niño mature phase relative to those at recharged time explain why the EP and CP El Niño peak in different stages of the recharge–discharge process.     

Diatoms in surface sediments of the Sea of Okhotsk and the northwest Pacific Ocean

The present investigation was targeted at diatom composition studies in the surface sediments (0–1 cm) sampled in the Sea of Okhotsk and the northwest Pacific in the depth range from 130 to 6110 m. The taxonomic analysis, as well as the quantitative (the diatom cell abundance per sediment dry weight unit) content and ecological group definition, was applied. Ten diatom taxa are the main body (80–100%) of the diatom assemblages: Bacterosira bathyomphala, Chaetoceros spp. (spores), Actinocyclus curvatulus, Thalassiosira latimarginata (group), T. antarctica (spores), Neodenticula seminae, Rhizosolenia hebetata f. hiemalis, Thalassiothrix longissima, Coscinodiscus marginatus, Coscinodiscus oculus iridis. The relative content of these species reflects the sedimentation conditions for different parts of the sea: the shelf, the continental slope, the open sea, and the ocean. The highest diatom content (45.6.3–60.0 10⁶ per g of dry weight) was found for the surface sediments in the central part of the Sea of Okhotsk and the continental slope of western Kamchatka.