Steric height trends at Ocean Station Papa in the Northeast Pacific Ocean

Abstract

We estimate secular changes in steric sea level in the northeast Pacific Ocean using the 27‐year time series of monthly hydrographic observations for Station PAPA (50°N, 145°W). Linear trends based on the entire data record suggest that steric heights relative to 1000 db are increasing at a rate of 0.93 mm/yr and that 67% of this increase is due to thermosteric changes at depths below 100 m; the smaller halosteric contribution to the steric trend appears to be confined to the upper 100 m. A trend of 0(1 mm/yr) is consistent with estimates of sea level rise based on coastal tide gauge records. However, a critical examination of the results indicates that sea level changes of such small magnitude would be masked by the large (1–10 cm) interannual variability of open ocean steric height. This is verified by recalculation of trends using abridged versions of the data set. We conclude that our trend estimates are still open to question and that the present 27‐year time series is too short to permit accurate resolution of possible climate‐induced changes in global sea level.     

Plankton copper requirements and uptake in the subarctic Northeast Pacific Ocean

We undertook the first measurements of metabolic Cu requirements (net Cu:C assimilation ratios) and steady-state Cu uptake rates (ρCu_ss) of natural plankton assemblages in the northeast subarctic Pacific using the short-lived radioisotope ⁶⁷Cu. Size-fractionated net Cu:C assimilation ratios varied ～3 fold (1.35–4.21 μmol Cu mol C^?1) among the stations along Line P, from high Fe coastal waters to the Fe-limited open ocean. The variability in Cu:C was comparable to biogenic Fe:C ratios in this region. As previously observed for Fe uptake, the bacterial size class accounted for half of the total particulate ρCu_ss. Interestingly, carbon biomass-normalized rates of Fe uptake from the siderophore desferrioxamine B (DFB) (ρFe_DFB; a physiological proxy for Fe-limitation) by the >20 μm size class were positively correlated with the intracellular net Cu:C assimilation ratios in this size class, suggesting that intracellular Cu requirements for large phytoplankton respond to increased Fe-limitation. At Fe-limited Ocean Station Papa (OSP), we performed short-term Cu uptake (ρCu_L) assays to determine the relative bioavailability of Cu bound to natural and synthetic ligands. Like the volumetric ρCu_ss measured along Line P, the bacterial size class was responsible for at least 50% of the total ρCu_L. Uptake rates of Cu from the various organic complexes suggest that Cu uptake was controlled by the oxidation state of the metal and by the metal:ligand concentration ratio, rather than the concentration of inorganic species of Cu in solution. Collectively, these data suggest that Cu likely plays an important role in the physiology of natural plankton communities beyond the toxicological effects studied previously.     

A comparison of two methods for determining copper partitioning in oxidized sediments

Model estimations of the proportion of Cu in oxidized sediments associated with extractable organic materials show some agreement with the proportion of Cu extracted from those sediments with ammonium hydroxide. Data were from 17 estuaries of widely differing sediment chemistry. The modelling and extraction methods agreed best where concentrations of organic materials were either in very high concentrations, relative to other sediment components, or in very low concentrations. In the range of component concentrations where the model predicted Cu should be distributed among a variety of components, agreement between the methods was poor. Both approaches indicated that Cu was predominantly partitioned to organic materials in some sediments, and predominantly partitioned to other components (most probably iron oxides and manganese oxides) in other sediments, and that these differences were related to the relative abundances of the specific components in the sediment. Although the results of the two methods of estimating Cu partitioning to organics correlated significantly among 24 stations from the 17 estuaries, the variability in the relationship suggested refinement of parameter values and verification of some important assumptions were essential to the further development of a reasonable model.     

Matched-field processing in a range-dependent shallow waterenvironment in the Northeast Pacific Ocean

This paper describes matched-field processing (MFP) of data collected in shallow water off the western coast of Vancouver Island in the Northeast Pacific Ocean. The data were collected from a vertical line array (VLA) as part of the PACIFIC SHELF trial carried out on the continental shelf and slope during September 1993, sensors in the 16-element VLA were evenly spaced at depths between 90 and 315 m, while the sound source was towed along radial paths or arcs. In this paper, we present results of the analysis of data from a continuous wave (CW) source which was towed downslope at a depth of 30 m in water from 150 to 375 m deep, in order to model the range-dependence of the acoustic propagation efficiently, the replica fields were calculated using the adiabatic normal mode approximation. This approximation was considered appropriate for the bottom slopes of the environment. Using sparse bathymetric data, a water sound speed profile and estimates of bottom properties, MFP correlations on individual ambiguity surfaces were found to be greater than 0.9 for the strongest signals. On account of environmental mismatch, the source position could not be determined unambiguously from most of the ambiguity surfaces even at high signal-to-noise ratios. Nevertheless, when an efficient linear tracker was applied to the ambiguity surfaces to find tracks, the source track was recovered at both low and high signal-to-noise ratios, this tracker performs the analysis at a constant depth and reports the track with the highest estimated track signal-to-noise ratio     

Evidence of change in the winter mixed layer in the Northeast Pacific Ocean

Sea-surface temperatures in the Northeast Pacific Ocean show a warming trend, and salinities show a declining trend, in data collected over the last 60 years. These changes combine to reduce the density of the surface layer over a large area of the Northeast Pacific. The declining surface density changes the energetic requirements for the formation of a surface mixed layer, and observations at Ocean Station Papa indicate that mid-winter mixed layer depths are showing a marked decline. The reduction in the depth of penetration of the winter-time mixed layer should reduce the nutrients entrained into the upper ocean each winter. Observations suggest that near surface nutrient levels are declining at Papa but remain well above levels that might inhibit productivity. However, at present the productivity of large phytoplankton appears to be limited by iron supply which is thought to be mainly from the atmosphere. A shallower mixed layer depth could increase the concentration of iron in this layer. The increase in iron would increase the utilization of nitrate, mainly by diatoms, and new production and the f ratio would increase.     

Chemical speciation of copper and zinc in surface waters of the western Black Sea

The chemical speciation of Cu and Zn was investigated by voltammetric titration methods in the surface waters (10 m) of the western Black Sea during an Istanbul–Sevastopol cruise conducted in November 1998. Supporting parameters (temperature (T), salinity (S), pH, alkalinity (Alk), suspended particulate matter (SPM) and dissolved and particulate ²³⁴Th) were obtained in order to distinguish hydrographic features against involvement of the metals in biogeochemical processes. In the Turkish continental slope region, the cruise track intersected a narrow vein of colder water originating on the western shelf. The core of this cold water vein was characterised by a relatively low salinity, higher specific alkalinity and higher metal (especially Cu) and metal-binding ligand concentrations.A very large portion of Cu (93–99.8%) and Zn (82–97%) was organically complexed. The degree of complexation was highest in shelf waters and lowest in the central gyre. Titration data for Cu were modelled by two classes of organic binding ligands characterised by (C_L1=3–12 nM, log K₁′=13.1–13.9) and (C_L2=20–70 nM, log K₂′=9.4–11.2). These ligands occurred mainly in the ‘dissolved’ phase, as defined by 0.4-μm filtration. The stronger Cu-binding ligand seemed to be produced in situ in response to Cu concentration, whereas the weaker Cu-binding ligand appeared to be derived from terrestrial sources and/or reducing shelf sediments. Titration results for Zn were generally represented by one class of ligands (C_L1=8–23 nM, log K₁′=9.4–10.2), which were almost uniformly distributed between the ‘dissolved’ (78±8%) and the particulate phase (22±8%). The concentration of these strong Zn-binding ligands showed a very good correlation with SPM (r²=0.64), which improved when the dissolved ligands alone were considered (r²=0.78). It is hypothesised that these ligands were produced in situ by the bacterial breakdown of particulate organic matter.     

Hydrothermal manganese oxide deposits from Baby Bare seamount in the Northeast Pacific Ocean

Manganese oxide crusts were recovered from Baby Bare seamount in order to investigate the history of off-axis hydrothermal venting. Baby Bare is a small basement high protruding from a regional sediment cover on the eastern flank of the Juan de Fuca Ridge that acts as a focus for discharging crustal fluids. Stratabound Mn-oxide crusts were collected where warm venting has been observed near the seamount summit. Mn-oxide crusts are composed primarily of 10 Å manganate ± pyrolusite, with minor nontronite, saponite, and/or barite. These assemblage and chemical characteristics such as high Mn/Fe ratios and low trace metal and REE concentrations are indicative of a hydrothermal origin. Minimum ages for these deposits, calculated using growth rates (324 to ∼ 1800 mm/Ma) and estimated thicknesses of manganese outcrops, show that Baby Bare has been hydrothermally active for at least 0.5 Myr, and possibly since its formation (1.7–2.7 Ma). Hydrothermal manganese oxide crusts such as these from Baby Bare record interactions between the hydrothermal fluids and seawater and are important tools for estimating the longevity of off-axis hydrothermal activity.     

Nitrogen isotope patterns in the oxygen-deficient waters of the Eastern Tropical North Pacific Ocean

We analyzed the stable nitrogen isotope composition of an extensive set of samples of particulate matter (PM) and seawater nitrate collected during October/November 1997 along the Mexican coastline from 24° to 11.5°N. At the northern and southern end of our study area, the δ¹⁵N of PM ranged between 5 and 7‰ in the upper 200 m of the water column with higher values at intermediate depths. These data are very similar to those reported from other parts of the open ocean. In the oxygen minimum zone (OMZ), we found significantly higher δ¹⁵N values for suspended particles. Furthermore, the δ¹⁵N of nitrate (NO₃) was elevated within the OMZ and we found a strong relationship between the oxygen concentration, nitrate deficit and the ¹⁵N content of the nitrate. The core of the OMZ between 22°N, 105°W and 15°N, 110°W coincided with higher nitrate deficits and δ¹⁵N values relative to the stations near the boundaries. The δ¹⁵N of nitrate was highest, with values up to 18.7‰, where oxygen concentrations were below 1–2 μmol/l. This pattern is consistent with an overall nitrogen isotopic enrichment factor of 22.5‰ for denitrification in the core of the OMZ using the Rayleigh equation (closed-system approach). Results from a diffusion model (open-system approach), however, gave a fractionation factor of 30±7.5‰, implying that the Rayleigh formula only gives a lower estimate of the fractionation factor ε. The vertical flux of particles collected in short-term deployments (ca. 35 h) of a drifting sediment trap was not significantly correlated with the water column nitrate deficit. The isotopic signature of the nitrate within the gradient is very similar to the δ¹⁵N value of sedimenting particles, suggesting that there might be a strong link between the production and sedimentation of particles. Upward flux of nitrate across the thermocline can account for less than half of the particle flux leaving the mixed layer. Mixing and transport of nitrate across the lower boundary of the OMZ can lead to significant enrichment in the ¹⁵N content of deep waters, and our isotopic data imply that at least 14% of the nitrate in the waters below the OMZ originates from this source.     

Distribution of bacterial abundance and cell-specific nucleic acid content in the Northeast Pacific Ocean

We tested the idea that bacterial cells with high nucleic acid content (HNA cells) are the active component of marine bacterioplankton assemblages, while bacteria with low nucleic acid content (LNA cells) are inactive, with a large data set (>1700 discrete samples) based on flow cytometric analysis of bacterioplankton in the Northeast Pacific Ocean off the coast of Oregon and northern California, USA. Samples were collected in the upper 150 m of the water column from the coast to 250 km offshore during 14 cruises from March 2001 to September 2003. During this period, a wide range of trophic states was encountered, from dense diatom blooms (chlorophyll-a concentrations up to 43 μg l⁻¹) at shelf stations during upwelling season (March–September) to lower chlorophyll-a concentrations (0.1–5 μg l⁻¹) during winter (November–February) and at basin stations (>1700 m depth). We found only weakly positive relations of log total bacterial abundance to log chlorophyll-a concentration (as a proxy for availability of organic substrate), and of HNA bacteria as a fraction of total bacteria to log chlorophyll-a. Abundance of HNA and LNA bacteria co-varied positively in all regions, although HNA bacteria were more responsive to high phytoplankton biomass in shelf waters than in slope and basin waters. Since LNA cell abundance in general showed responses similar to those of HNA cell abundance to changes in phytoplankton biomass, our data do not support the hypothesis that HNA cells are the sole active component of marine bacterioplankton.     

Production and speciation of hydrogen sulfide in surface waters of the high latitude North Atlantic Ocean

During the August 1993 Intergovernmental Oceanographic Commission's Contaminant Baseline Survey cruise to the high latitude North Atlantic, determinations of total dissolved sulfide (TDS=free sulfide, H₂S_(g)+HS⁻+S²⁻, plus dissolved metal–sulfide complexes), free sulfide, and carbonyl sulfide (OCS) were made along a horizontal transect and at six vertical profile stations. Unlike data from lower latitudes, the distributions of OCS and TDS were remarkably uniform, with surface water OCS averaging 108 pmol/l and TDS averaging 58 pmol/l; free sulfide was below the detection limits of 5 pmol/l at all stations. The vertical profiles of both OCS and TDS show surface maxima and rapid decreases into the major thermocline. For OCS this is indicative of production via photolysis of dissolved organic sulfur compounds, while TDS may be produced from the hydrolysis of OCS. The concentrations of OCS are similar to those found in coastal waters, and suggests that these sub-polar regions may be large OCS sources to the troposphere during summer. However, it is unclear whether higher concentrations of OCS precursors, a long photo period during summer, or slow rates of removal by hydrolysis due to low temperatures are responsible for the elevated OCS levels. TDS concentrations are primarily controlled by the rate of OCS hydrolysis, production by phytoplankton, and oxidative loss by oxygen and iodate. Both of the losses are affected by trace metal complexation, and to examine this, freshly collected seawater was amended by hydrogen sulfide gas and trace metal additions, and the concentration of free sulfide monitored as a function of metal concentration. This allowed the determinations of conditional stability constants for metal sulfides, with the log K_cond of Cd(HS)⁺ being 8.0±0.5, 7.0±0.6 for Ni(HS)⁺, and 7.4±0.7 for Zn(HS)⁺; attempts at measuring the K_cond of Cu(HS)⁺ were thwarted by the apparent reduction of Cu(II) to Cu(I) by sulfide. Using these constants in an equilibrium speciation model indicates that on average about 75% of the measured TDS was free, with the remaining fraction complexed with Ni, Cd, and Zn (in order of decreasing percentages). While closer to the field observations than would be found with stability constants reported by other workers, these values are still at variance with the actual speciation (i.e., <30% free). This suggests that the stability constants for Cd, Ni, and Zn are somewhat higher than found, thus reducing the concentration of free sulfide. Nevertheless, these speciation data are important for balancing the TDS budget since the loss by iodate oxidation of free sulfide exceeds all production estimates.     

西太平洋冬季上层水体有色溶解有机物的分布和转化特征

为深入解析西太平洋溶解有机碳的生物地球化学过程,本研究于2015年12月至2016年1月,开展了西太平洋上层水体有色溶解有机物（CDOM）吸收光谱和荧光光谱特征研究。研究结果表明,西太平洋上层水体CDOM吸收系数a（320）变化范围为0.01~1.07 m-1,平均值为0.18 m-1;其较高值位于100~200 m水层,表层的海水相对含量较低,主要以有机物的光化学分解为主。采用PARAFAC分析CDOM三维荧光光谱特征,得到1种类腐殖质组分C2（252（310 nm）/405 nm）及2种类蛋白组分C1（224（276 nm）/335 nm）和C3（224（260 nm）/300 nm）,其中类腐殖质荧光组分占总荧光强度的11%~22%,蛋白质荧光组分占总荧光强度的78%~89%,蛋白质荧光中类色氨酸和类络氨酸组分对荧光强度的贡献相当。洋流在大尺度上控制西太平洋CDOM的分布特征,两流交界处和环流形成区域的CDOM相对含量较高,荧光信号较强。西太上层水体CDOM相对含量和荧光信息,与温度、盐度、DO和营养盐等理化因素之间的相关分析结果表明,CDOM主要成分类蛋白质的产生主要受上层水体初级生产过程控制。     

Concentrations of cadmium,copper, lead and zinc in surface waters of the Northwest Atlantic Ocean — A comparison of Go-flo and teflon water samplers

The concentrations of cadmium, copper, lead and zinc were measured at two locations in surface waters of the western North Atlantic. Samples were collected upstream of the research vessel in 1-1 teflon bottles, and in a 30-1 teflon-coated Go-flo bottle. Surface mixed-layer samples were also collected at each location by ship cast using this same Go-flo sampler. A comparison of the three sampling modes shows that all the samples taken with the Go-flo sampler possessed much higher concentrations of zinc (7–10-fold) and lead (2–3-fold) than those collected directly in teflon bottles. No apparent differences were noted at each station in the concentrations of either copper or cadmium among the samples collected by the three different procedures. The measured values for copper and cadmium in these waters are in good agreement with recent reports for the western North Atlantic.     

Rare earth element geochemistry in cold-seep pore waters of Hydrate Ridge, northeast Pacific Ocean

The concentrations of rare earth elements (REEs), sulphate, hydrogen sulphide, total alkalinity, calcium, magnesium and phosphate were measured in shallow (<12 cm below seafloor) pore waters from cold-seep sediments on the northern and southern summits of Hydrate Ridge, offshore Oregon. Downward-decreasing sulphate and coevally increasing sulphide concentrations reveal sulphate reduction as dominant early diagenetic process from ~2 cm depth downwards. A strong increase of total dissolved REE (∑REE) concentrations is evident immediately below the sediment–water interface, which can be related to early diagenetic release of REEs into pore water resulting from the re-mineralization of particulate organic matter. The highest pore water ∑REE concentrations were measured close to the sediment–water interface at ~2 cm depth. Distinct shale-normalized REE patterns point to particulate organic matter and iron oxides as main REE sources in the upper ~2-cm depth interval. In general, the pore waters have shale-normalized patterns reflecting heavy REE (HREE) enrichment, which suggests preferential complexation of HREEs with carbonate ions. Below ~2 cm depth, a downward decrease in ∑REE correlates with a decrease in pore water calcium concentrations. At this depth, the anaerobic oxidation of methane (AOM) coupled to sulphate reduction increases carbonate alkalinity through the production of bicarbonate, which results in the precipitation of carbonate minerals. It seems therefore likely that the REEs and calcium are consumed during vast AOM-induced precipitation of carbonate in shallow Hydrate Ridge sediments. The analysis of pore waters from Hydrate Ridge shed new light on early diagenetic processes at cold seeps, corroborating the great potential of REEs to identify geochemical processes and to constrain environmental conditions.     

The return of Pacific waters to the upper layers of the central Arctic Ocean

Temperature, salinity, and chemical measurements, including the nutrients silicic acid (Si), nitrate (NO₃), nitrite (NO₂), ammonium (NH₄), and phosphate (PO₄ or P), the oxygen isotopic composition of seawater (δ¹⁸O), and barium (Ba) concentrations were obtained from the central Arctic Ocean along transects radiating from the North Pole in early spring, 2000–2006. Stations that were reoccupied over this time period were grouped into five regions: from Ellesmere Island, (1) north along 70°W and (2) northwest along 90°W; near the North Pole, (3) on the Amundsen Basin flank and (4) directly over the Lomonosov Ridge; (5) through the Makarov Basin along 170–180°W. These regions had been shown by others to have undergone marked changes in water-mass assemblies in the early 1990s, but our time series tracer hydrographic data indicate a partial return of Pacific origin water within the mixed layer and the upper halocline layers beginning in 2003–2004. Back-trajectories derived from satellite-tracked ice buoys for these stations indicate that the upper levels of Pacific water in the central Arctic in 2004–2006 transited westward from the Bering Strait along the Siberian continental slope into the East Siberian Sea before entering the Transpolar Drift Stream (TPD). By 2004, the TPD shifted back from an alignment over the Alpha-Mendeleev Ridge toward the Lomonosov Ridge, as was characteristic prior to the early 1990s. At most stations occupied in 2006, a decrease in the Pacific influence was observed, both in the mixed layer and in the upper halocline, which suggests the Canadian branch of the TPD was shifting back toward North America. Clearly the system is more variable than has been previously appreciated.     

太平洋潮波特征比较

本文对TOPEX/Poseidon高度计资料直接分析得到4个主要分潮(M2、K1、S2和O1)的调和常数,将其与全球大洋潮波模式TPXO6.2的模拟结果以及太平洋中48个验潮站观测资料的分析结果进行了系统比较,得出高度计资料直接分析结果与潮波模式模拟结果总体比较一致.模拟出的无潮点的位置和高度计资料直接分析结果有差异,且K1和O1分潮差异较大.与站点结果比较表明TPXO6.2模式模拟结果与验潮站观测结果的振幅绝对偏差小于2cm的站点的百分比达到85%,迟角绝对偏差小于40°的站点的百分比达到70%以上,比高度计资料直接分析结果精确;矢量均方根误差比较表明,太平洋中部结果比整个太平洋结果准确,太平洋矢量均方根误差的值和其他研究者、其他模式的结果近似.     

东北太平洋中国开辟区浮游植物的种类组成与分布

根据东北太平洋中国开辟区西部(151°W～155°W,8°N～11°30＇N)和东部(141°W～149°W,7°N～10°N)水域DY95-7航次(1997-07)和DY95-8航次(1998-07～-09)所采的36份网采样品,鉴定网采浮游植物180种,隶属于5个门类47属.其中主要的生态类群是大洋暖水类群(占总种数83.8%)和广布性类群(占14.5%).该区主要优势种是太阳漂流藻(Planktoniella sol)、密聚角毛藻(Chaetoceros coarctatus)、多瘤面角毛藻(C.bacteriastroides)、拟夜光梨甲藻(Pyrocystispseudonoctilluca)和三叉角藻(Cerattum trichoceros)等.硅藻类和甲藻类等的平均细胞密度(1 944～4 101个/m)和蓝藻类(主要是束毛藻Trichodesmium)的藻丝体密度(111～486条/m)都比较低.本文分别讨论了调查区浮游植物的平面分布和垂直分布趋势及其与温跃层和浮游动物的相互关系.     

Light scattering and size distribution of particles in the surface waters of the North Pacific Ocean

The volume scattering function and size distribution of suspended particles in the surface water were determined in the North Pacific. The relationship between the scattering coefficient estimated from observed volume scattering function and cross-section concentration of the particles greater than 2.4m in diameter was found to be linear in both northern and southern regions of central North Pacific. Difference in the constant of proportionality between two regions, however, was very great. Moreover the constant in the southern region was too large compared with the values obtained by the Mie theory. This is considered to be due to the fact that particles smaller than 2.4m which were not measureable by the Coulter Counter, were neglected in the calculation of cross-section concentration. If small particles are taken into consideration, total cross-section concentration and scattering coefficient in the two regions tend to follow a linear relation. From the correlation between the scattering coefficient computed from size distribution and the volume scattering function, the refractive index of particles was estimated to be 1.03–1.05. By the same procedure, the refractive index of particles in Tateyama Harbour where the water was very turbid, was estimated to be also 1.03–1.05. This is in contrast to the result for the refractive index of particles originating from the river which flows into the harbour. This index was found to be 1.10–1.20.     

北太平洋西部和印度洋东部及其邻近海域表层水体中137Cs的分布

对北太平洋西部海域、苏禄海及印尼海、中国南海、印度洋东部海域、孟加拉湾及安达曼海等表层水体中放射性核素137Cs的活度进行了测定。结果表明,上述海域表层水体中137Cs活度显示了较大的变化范围,最低值出现在南极附近的南大洋(1.1Bqm-3),较高的活度值则出现在北太平洋西部海域及中国南海(3Bqm-3)。在所研究水域范围内,137Cs活度的纬度分布特征并没有完全有效地反映出137Cs的全球理论大气沉降趋势及其纬度效应。综合本研究及Miyake等人(1988)的测定结果,我们计算出137Cs自表层海水中的析出速率在苏禄海及印尼海约为0.016/a,在孟加拉湾及安达曼海约为0.033/a,在中国南海约为0.029/a,这一结果明显低于西北太平洋日本沿海表层水体中137Cs的析出速率。这可能是因为在这些海域,横向及纵向的水体混合过程相对都较慢,而且颗粒物对137Cs的吸附析出过程也比较弱所致。     

Comparison of community structures between particle-associated and free-living prokaryotes in tropical and subtropical Pacific Ocean surface waters

The subtropical and tropical regions of the Pacific Ocean are less productive than other oceanic regions. Although particle association should be an important strategy for heterotrophic prokaryotes to survive in such environments, we have little information on particle-associated (PA) prokaryotes in these regions. The specific aim of this study was to determine bacterial and archaeal community structures in the PA assemblage in comparison to the free-living (FL) assemblage in the North Pacific Subtropical Gyre, the South Pacific Subtropical Gyre, and an eastern equatorial region of the Pacific Ocean. Community profiles and phylogenetic identities were obtained by denaturing gradient gel electrophoresis, 454-pyrosequencing, and cloning followed by Sanger sequencing of 16Sr RNA gene amplicons. The distribution patterns of some abundant groups in three regions and two lifestyles (PA and FL) are shown in this study. Also, the PA community structures of bacteria differed from the FL ones and exhibited higher diversity than the FL ones, while the archaeal community structures did not show significant differences between PA and FL assemblages. We found that specific phylotypes of Gammaproteobacteria and Flavobacteria were abundant in PA bacterial assemblages, suggesting that they prefer to attach and consume particulate organic matter. In summary, the surface seawater PA assemblages represent very different bacterial and archaeal community structures between three different oceanic regions, each of which had distinct PA and FL community structures. These results imply that environmental factors determine microbial community structures.