Nutrient gradients in the western North Atlantic Ocean: Relationship to microbial community structure and comparison to patterns in the Pacific Ocean

Studies of nitrogen and phosphorus dynamics in the oligotrophic surface waters of the western North Atlantic Ocean have been constrained because ambient concentrations are typically at or below the detection limits of standard colorometric methods, except during periods of deep vertical mixing. Here we report the application of high-sensitivity analytical methods—determinations of nitrate plus nitrite (N+N) by chemiluminescence and soluble reactive phosphorus (SRP) by the magnesium induced co-precipitation (MAGIC) protocol—to surface waters along a transect from the Sargasso Sea at 26°N through the Gulf Stream at 37°N, including sampling at the JGOFS Bermuda Atlantic Time-series Study (BATS) station. The results were compared with data from the BATS program, and the HOT station in the Pacific Ocean, permitting cross-ecosystem comparisons. Microbial populations were analyzed along the transect, and an attempt was made to interpret their distributions in the context of the measured nutrient concentrations.Surface concentrations of N+N and SRP during the March 1998 transect separated into 3 distinct regions, with the boundaries corresponding roughly to the locations of the BATS station (∼31°N) and the Gulf Stream (∼37°N). Although N+N and SRP co-varied, the [N+N] : [SRP] molar ratios increased systematically from ∼1 to 10 in the southern segment, remained relatively constant at ∼40–50 between 31°N and 37°N, then decreased again systematically to ratios <10 north of the Gulf Stream. Dissolved organic N (DON) and P (DOP) dominated (⩾90%) the total dissolved N (TDN) and P (TDP) pools except in the northern portion of the transect. The [DON] : [DOP] molar ratios were relatively invariant (∼30–60) across the entire transect.Heterotrophic prokaryotes (operationally defined as “bacteria”), Prochlorococcus, Synechococcus, ultra- and nanophytoplankton, cryptophytes, and coccolithophores were enumerated by flow cytometry. The abundance of bacteria was well correlated with the concentration of SRP, and that of the ultra- and nanophytoplankton was well correlated with the concentration of N+N. The only group whose concentration was correlated with temperature was Prochlorococcus, and its abundance was unrelated to the concentrations of nutrients measured at the surface.We combined our transect results with time-series measurements from the BATS site and data from select depth profiles, and contrasted these North Atlantic data sets with time-series of N and P nutrient measurements from a station in the North Pacific subtropical gyre near Hawaii [Hawaii Ocean Time-series (HOT) site]. Two prominent differences are readily observed from this comparison. The [N+N] : [SRP] molar ratios are much less than 16 : 1 during stratified periods in surface waters at the BATS site, as is the case at the HOT site year round. However, following deep winter mixing, this ratio is much higher than 16 : 1 at BATS. Also, SRP concentrations in the upper 100 m at BATS fall in the range 1–10 nM during stratified periods, which is at least one order of magnitude lower than at the HOT site. That two ecosystems with comparable rates of primary and export production would differ so dramatically in their nutrient dynamics is intriguing, and highlights the need for detailed cross ecosystem comparisons.     

气候-海洋变动的生态响应研究进展

以对太平洋与大西洋现象的观察和分析为主线,论述了年际与年代际变动及其可能的机制,综述了气候-海洋变动生态响应国际、国内的研究现状。在太平洋和大西洋都出现了类似的浮游动物、鱼类群落组成和丰度的年际及年代际变动的现象,并发现了直接与某些强E lN in~o事件对应的从营养盐到叶绿素含量变动的信号,虽然目前尚缺乏物理-化学-生物过程上长期、有力的观测证据,但是海流的强弱变动很可能是导致这种生态响应的关键驱动力。国内在该领域的研究相对比较薄弱,未来需要着力解决该领域中存在的生态响应机制、区域响应形态不清等关键的科学问题。     

Similarity in microbial amino acid uptake in surface waters of the North and South Atlantic (sub-)tropical gyres

The Earth’s most extensive biomes – the oceanic subtropical gyres – are considered to be expanding with current surface ocean warming. Although it is well established that microbial communities control gyre biogeochemistry, comparisons of their metabolic activities between gyres are limited. In order to estimate metabolic activities including production of microbial communities, the uptake rates of amino acids leucine, methionine and tyrosine at ambient concentrations were estimated in surface waters of the Atlantic Ocean using radioisotopically labelled tracers. Data were acquired during six research cruises covering main oceanic provinces herein termed: North and South Atlantic Gyres, Bermuda Atlantic Time-series Study site (BATS), Equatorial region, and Mauritanian Upwelling (off Cape Blanc). Data were divided between provinces, the extents of which were identified by ocean colour data, in order to achieve provincial mean uptake rates. Leucine and methionine uptake rates did not differ between sampling periods, and were comparable between the North and South subtropical gyres. Furthermore, variation in uptake rates measured throughout the two oligotrophic gyres, where sampling covered ∼4 × 10⁶ km², was considerably lower than that measured within the Mauritanian Upwelling and Equatorial regions, and even at the BATS site. Tyrosine was generally the slowest of the amino acids to be taken up, however, it was assimilated faster than methionine within the Mauritanian Upwelling region. Thus, we propose that one value for leucine (12.6 ± 3.2 pmol L⁻¹ h⁻¹) and methionine (10.0 ± 3.3 pmol L⁻¹ h⁻¹) uptake could be applied to the oligotrophic subtropical gyres of the Atlantic Ocean. However, with the significantly lower uptake rates observed at the BATS site, we would not advise extrapolation to the Sargasso Sea.     

Predicting plankton net community production in the Atlantic Ocean

We present, test and implement two contrasting models to predict euphotic zone net community production (NCP), which are based on ¹⁴C primary production (PO¹⁴CP) to NCP relationships over two latitudinal (ca. 30°S–45°N) transects traversing highly productive and oligotrophic provinces of the Atlantic Ocean (NADR, CNRY, BENG, NAST-E, ETRA and SATL, Longhurst et al., 1995 [An estimation of global primary production in the ocean from satellite radiometer data. Journal of Plankton Research 17, 1245–1271]). The two models include similar ranges of PO¹⁴CP and community structure, but differ in the relative influence of allochthonous organic matter in the oligotrophic provinces. Both models were used to predict NCP from PO¹⁴CP measurements obtained during 11 local and three seasonal studies in the Atlantic, Pacific and Indian Oceans, and from satellite-derived estimates of PO¹⁴CP. Comparison of these NCP predictions with concurrent in situ measurements and geochemical estimates of NCP showed that geographic and annual patterns of NCP can only be predicted when the relative trophic importance of local vs. distant processes is similar in both modeled and predicted ecosystems. The system-dependent ability of our models to predict NCP seasonality suggests that trophic-level dynamics are stronger than differences in hydrodynamic regime, taxonomic composition and phytoplankton growth. The regional differences in the predictive power of both models confirm the existence of biogeographic differences in the scale of trophic dynamics, which impede the use of a single generalized equation to estimate global marine plankton NCP.This paper shows the potential of a systematic empirical approach to predict plankton NCP from local and satellite-derived P estimates.     

Nutrient supply to anticyclonic meso-scale eddies off western Australia estimated with artificial tracers released in a circulation model

The phytoplankton distribution off western Australia in the period from April to October is unique in that high biomass is generally associated with anticyclonic eddies and not with cyclonic eddies. As the western Australian region is oligotrophic this anomalous feature must be related to differing nutrient supply pathways to the surface mixed layer of cyclonic and anticyclonic eddies. A suite of modelled abiotic tracers suggests that cyclonic eddies are predominantly supplied by diapycnal processes that remain relatively weak until June–July, when they rapidly increase because of deepening surface mixed layers, which start to tap into the nutrient-replete waters below the euphotic zone. To the contrary, we find that anticyclonic eddies are predominantly supplied by injection of shelf waters, which carry elevated levels of inorganic nutrients and biomass. These injections start with the formation of the eddies in April–May, continue well into the austral winter and reach as far as several hundred kilometers offshore. The diapycnal supply of nutrients is suppressed in anticyclonic eddies since the injection of warm, low-salinity shelf waters delays the erosion of the density gradient at the base of the mixed layer. Our results are consistent with the observed seasonal cycles of chlorophyll a and observation of particulate organic matter export out of the surface mixed layer of an anticyclonic eddy in the region.     

美洲黑石斑鱼含肉率及肌肉营养成分分析

利用常规肌肉营养测试方法,测定分析了美洲黑石斑鱼的含肉率及肌肉营养成分。测定结果显示,美洲黑石斑鱼含肉率平均值为(73.71±1.93)%,肌肉(鲜样)中粗蛋白、粗脂肪、水分和粗灰分含量分别为(19.09±1.34)%,(6.14±1.76)%,(71.86±1.58)%和(1.32±0.17)%;美洲黑石斑鱼肌肉中被测出的常见氨基酸(色氨酸未测定)有17种,其中包括7种必需氨基酸、2种半必需氨基酸和8种非必需氨基酸,其氨基酸含量占鲜体质量的百分比分别为(8.27±0.21)%,(1.84±0.08)%和(10.15±0.31)%,17种氨基酸总含量为(20.26±1.13)%(鲜样)。谷氨酸(Glu)含量占鲜体质量的百分比最高,为(3.27±0.16)%,其次是天冬氨酸(Asp)和赖氨酸(Lys),胱氨酸(Cys)含量占鲜体质量的百分比为最低,仅为(0.27±0.01)%。4种鲜味氨基酸含量占干样的(29.32±0.14)%。鲜样的美洲黑石斑鱼必需氨基酸总量占氨基酸总量的比值为40.82%,干样的为40.81%;鲜样的必需氨基酸总量与非必需氨基酸总量的比值为81.48%,干样的为81.43%,其构成符合FAO/WHO的标准。同时计算出的美洲黑石斑鱼肌肉蛋白质氨基酸评分(AAS)均大于1,化学评分(CS)均大于0.7,必需氨基酸指数(EAAI)达到91.18,高于多数海产经济鱼类,说明它能为人体提供大量必需氨基酸,且其组成接近人体的氨基酸需要量模式。美洲黑石斑鱼肌肉中主要含有16种脂肪酸,其中饱和脂肪酸(SFA)7种,含量占肌肉脂肪酸总量的(38.66±1.22)%;不饱和脂肪酸(UFA)9种,含量占肌肉脂肪酸总量的(61.36±0.98)%,其中单不饱和脂肪酸(MUFA)5种,多不饱和脂肪酸(PUFA)4种。多不饱和脂肪酸中的人和动物生长发育必需的脂肪酸EPA和DHA含量,分别占总脂肪酸的(9.02±0.59)%和(11.73±0.43)%。-ω3族与-ω6族PUFA总量的比值为5.30。分析表明,美洲黑石斑鱼肌肉含肉率高,含有较多的粗蛋白和粗脂肪,氨基酸总量及鲜味氨基酸含量均较高,是一种优质蛋白源;美洲黑石斑鱼肌肉富含PUFA,尤其是EPA和DHA含量丰富,并且∑n3/∑n6值较高,因而具有较高的食用营养价值和保健功效,是一种具有广阔市场前景的优良养殖品种。     

Meridional heat transport in the North Atlantic and the trends of its variations in the second half of the 20th century

The meridional heat transport in the ocean is computed according to the data of zonal sections of the World Ocean Circulation Experiment made in the North Atlantic in 1992–1998. We perform the generalized analysis of the estimates of meridional heat transport obtained by different authors by direct methods on the basis of the data of sections made between 7.5 and 48°N in the second half of the last century. The meridional heat transport averaged over the entire period of observations attains its maximum (1.38 ± 0.19 PW) in the Subtropical Atlantic. The meridional heat transport is characterized by fairly intense seasonal variability. Its maximum (about 1.9 PW) is observed in the Subtropical Atlantic at the end of summer and its minimum (about 0.8 PW) is attained at the end of winter. A significant trend toward the intensification of meridional heat transport is revealed near 36°N in 1959–1993 (from 0.75 to 1.1 PW). This is an indication of the intensification of meridional oceanic circulation in the North Atlantic. Dedicated to the 75th birthday of N. A. Timofeev, Honored Scientist of the Ukraine, Doctor of Geographical Sciences __________ Translated from Morskoi Gidrofizicheskii Zhurnal, No. 1, pp. 45–58, January–February, 2007.     

2017年春夏季西北太平洋浮游植物的区域差异及其与不同水团的关系

The West Pacific Ocean is considered as the provenance center of global marine life and has the highest species diversity of numerous marine taxa. The phytoplankton, as the primary producer at the base of the food chain,effects on climate change, fish resources as well as the entire ecosystem. However, there are few large-scale surveys covering several currents with different hydrographic characteristics. This study aimed to explore the relationships between the spatio-temporal variation in phytoplankton community structure and different water masses. A total of 630 water samples and 90 net samples of phytoplankton were collected at 45 stations in the Northwest Pacific Ocean(21.0°–42.0°N, 118.0°–156.0°E) during spring and summer 2017. A total of 281 phytoplankton taxa(5 μm) belonging to 61 genera were identified in the study area. The distribution pattern of the phytoplankton community differed significantly both spatially and temporally. The average abundances of phytoplankton in spring and summer were 797.07×10~2 cells/L and 84.94×10~2 cells/L, respectively. Whether in spring or summer, the maximum abundance always appeared in the northern transition region affected by the Oyashio Current, where nutrients were abundant and diatoms dominated the phytoplankton community;whereas the phytoplankton abundance was very low in the oligotrophic Kuroshio region, and the proportion of dinoflagellates in total abundance increased significantly. The horizontal distribution of phytoplankton abundance increased from low to high latitudes, which was consistent with the trend of nutrient distributions, but contrary to that of water temperature and salinity. In the northern area affected by the Oyashio Current, the phytoplankton abundance was mainly concentrated in the upper 30 m of water column, while the maximum abundance often occurred at depths of 50–75 m in the south-central area affected by the Kuroshio Current.Pearson correlation and redundancy analysis(RDA) showed that phytoplankton abundance was significant negatively correlated with temperature and salinity, but positively correlated with nutrient concentration. The phytoplankton community structure was mainly determined by nutrient availability, especially the N:P ratio.     

Cerium anomaly and cerium thermodynamics in the sea water

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Multiannual trends in fronts and distribution of nutrients and chlorophyll in the southwestern Atlantic (30–62°S)

This paper presents the first data on the vertical distribution of chlorophyll and nutrients in the upper layers of the southern southwestern Atlantic and interprets it in relation to frontal systems and the general hydrographic features. The survey covered quasi-synoptically the area between 30 and 62°S, at the beginning of the austral summers of three consecutive years (1993 through 1995). Our results show a rather consistent oceanographic structure, with similar patterns of chlorophyll and nutrient distributions with latitude. Outstanding features present throughout the three seasons are two zones of high phytoplankton production, where chlorophyll concentrations of >1 μg/l seem to occur frequently. The first is the upper euphotic zone of the Brazil–Malvinas Confluence Zone between approximately 36 and 50°S. The second is centered on subsurface layers of the Antarctic Surface Water south of the Polar Front as far as 62°S. The rest of the area covered shows low chlorophyll concentrations (<0.4 μg/l), due either to nutrient limitation in the oligotrophic subtropical waters of the Brazil Current or to excessive turbulence and upper-layer instability in the energetic Malvinas Current. The occurrence of a permanent meander around 38°S coincided with the cyclonic retroflexion of the Malvinas Current, causing upwelling of deep water. The ecological implications of this eddy-induced upwelling are discussed.     

Mercury methylation,demethylation and reduction rates in coastal and marine surface waters of the Mediterranean Sea

In situ experiments using isotopically labeled mercury species (¹⁹⁹Hg(II) and Me²⁰¹Hg) are used to investigate mercury transformation mechanisms, such as methylation, demethylation and reduction, in coastal and marine surface waters of the Mediterranean Sea. The aim of this work is to assess the relative contribution of photochemical versus biological processes to Hg transformation mechanisms. For this purpose, potential transformation rates measured under diurnal and dark incubation conditions are compared with major biogeochemical parameters (i.e. hydrological and biological data) in order to obtain the relative contribution of various biotic and abiotic mechanisms in both surface (high light) and bottom (low light) waters of the euphotic zone. The results demonstrate that coastal and marine euphotic zones are significant reactors for all Hg transformations investigated (i.e. methylation, demethylation, reduction). A major outcome demonstrates that Hg methylation is taking place in oxic surface seawater (0.3–6.3% day^− 1) and is mainly influenced by pelagic microorganism abundance and activities (phyto- and bacterioplankton). This evidences a new potential MeHg source in the marine water column, especially in oligotrophic deep-sea basins in which biogeochemistry is mostly governed by heterotrophic activity. For coastal and marine surface waters, although MeHg is mainly photochemically degraded (6.4–24.5% day^− 1), demethylation yields observed under dark condition may be attributed to microbial or chemical pathways (2.8–10.9% day^− 1). Photoreduction and photochemical reactions are the major mechanisms involved in DGM production for surface waters (3.2–16.9% day^− 1) but bacterial or phytoplanktonic reduction of Hg(II) cannot be excluded deeper in the euphotic zone (2.2–12.3% day^− 1). At the bottom of the euphotic zone, photochemical processes are thus avoided due to the attenuation of UV-visible sunlight radiation allowing biotic processes to be the most significant. These results suggest a new potential route for Hg species cycling in surface seawater and especially at the maximum biomass depth located at the bottom of the euphotic zone (i.e. maximum chlorophyll fluorescence). In this environment, DGM production and demethylation mechanisms are thus probably reduced whereas Hg methylation is enhanced by autotrophic and heterotrophic processes. Experimental results on mercury species uptake during these investigations further evidenced the strong affinity of MeHg for biogenic particles (i.e. microorganisms) that correspond to the first trophic level of the pelagic food web.     

北冰洋与邻近海区海洋-海冰模式的试算与校验

本文将目前先进的大尺度海洋、海冰模式(NEMO3.6和LIM3)应用于北大西洋–北冰洋–北太平洋(简称NAPA)，并进行了试验后报模拟。所建立的模式NAPA1/4和NAPA1/12的水平分辨率分别为(1/4)°和(1/12)°经、纬度，计算范围覆盖太平洋45°N以北海区、整个北冰洋及北大西洋；其中，NAPA1/4和NAPA1/12在北大西洋的边界分别为26°N和7°N。目前，已利用NAPA1/4完成了1993–2015年的后报模拟。本文基于观测数据和已发表文献对模拟结果中的北冰洋海冰变化、环流结构以及水文特征进行了校验。结果表明，NAPA1/4能够再现北冰洋的主要热力与动力过程，可以用来分析海冰、水团、大西洋/太平洋入/出流等的季节与年际变化规律。利用NAPA1/12进行了1993–1996年的模拟计算。初步结果分析表明，提高分辨率可更为精细地刻画北冰洋的海冰、水团和环流的结构。     

Quasiperiodic small meanders of the Kuroshio off Cape Ashizuri and their inter-annual modulation caused by quasiperiodic arrivals of mesoscale eddies

A quasiperiodic variation of 100–110 days in the Kuroshio path off Cape Ashizuri, resulting from the passage of small meanders, was detected by observation with moored current meters during 1993–1995. TOPEX/POSEIDON altimeter data covering 9 years showed that the quasiperiodic variation period was not persistent and modulated twice, with a ∼110-day period from mid-1993 to late 1996, a ∼150-day period from late 1996 to mid-1999, and a ∼110-day period from mid-1999 to late 2001. The quasiperiodic variations of the Kuroshio path migration were contemporaneous with the quasiperiodic arrivals of mesoscale eddies from the east along 27–32°N over the same ∼110- and ∼150-day period quasiperiodic variations. The periodic arrivals of the eddies configure the periodic variations of the Kuroshio path and its inter-annual modulation.     

A pelagic ecosystem model calibrated with BATS and OWSI data

Ocean ecosystems play an important role in the global carbon cycle. In this paper, we develop and calibrate a pelagic ocean ecosystem model by simultaneously fitting data from two sites in the North Atlantic: the site of the Bermuda Atlantic Time-series Study (BATS, 32°N, 64°W) and Ocean Weather Ship Station “I” (OWSI, 59°N, 20°W). These sites differ dramatically in the magnitude and timing of primary production, chlorophyll concentrations, and light and nutrient availabilities. We find that a relatively simple model can be simultaneously fit to ecosystem data at both sites. As in the model of Hurtt and Armstrong (1996, Deep-Sea Research II 43(2–3): 653–683), the fit largely depends on the inclusion of multiple size classes of phytoplankton and detritus and a variable chlorophyll-to-biomass (nitrogen) ratio for phyto-plankton. The inclusion of these features in the model enables it to adjust to predict important biological differences temporally within sites and spatially between sites. In addition, the model also includes a phytoplankton self-shading parameter to capture differences in water clarity between sites, and the parameterization of iron limitation at OWSI as a hypothesis for the moderately HNLC condition there. Finally, we suggest that the model performs reasonably well at the Hawaii Ocean Time-series (HOT, 23°N, 158°W), a site where no model calibration was done.     

The organic carbon pump in the Atlantic

The growth, sinking and remineralisation of phytoplankton constitute the soft-tissue carbon pump. Here we derive the expression for the strength of this carbon pump in terms of the nutrient utilisation and the carbon:nutrient ratio of plankton. Furthermore, we aim to determine how the physical environment affects this carbon pump. Thereto, we have used a plankton physiological model with a novel representation of the effect of temperature and light on plankton stoichiometry; it predicts that the effect of temperature on the carbon:nutrient ratio depends on the light conditions. Using this model combined with a mechanistic model for the mixed layer, we have studied the biological carbon pump at the BATS site and at various locations along a meridional transect through the Atlantic Ocean. Our results suggest that the soft-tissue carbon pump is stronger at mid-latitudes than in the (sub-)tropics and near the poles as a consequence of latitudinal variations in algal stoichiometry.     

Phytoplankton pigment and absorption characteristics along meridional transects in the Atlantic Ocean

Pigment patterns and associated absorption properties of phytoplankton were investigated in the euphotic zone along two meridional transects in the Atlantic Ocean, between the UK and the Falkland Islands, and between South Africa and the UK. Total chlorophyll a (TChla=MVChla+DVChla+chlorophyllide a) concentrations and the biomarker pigments for diatoms (fucoxanthin), nanoflagellates and cyanobacteria (zeaxanthin) appeared to have similar distribution patterns in the spring and in the autumn in the temperate NE Atlantic and the northern oligotrophic gyre. Divinyl chlorophyll a levels (prochlorophytes) were greater in spring at the deep chlorophyll maximum in the oligotrophic gyre, however. Marked seasonal differences were observed in the NW African upwelling region. TChla concentrations were twice as high in the upper mixed layer in the spring, with the community dominated by diatoms and prymnesiophytes (19′-hexanoyloxyfucoxanthin). A layered structure was prevalent in the autumn where cyanobacteria, diatoms and prymnesiophytes were located in the upper water column and diatoms and mixed nanoflagellates at the sub-surface maximum. In the South Atlantic, the Benguela upwelling ecosystem and the Brazil-Falklands Current Confluence Zone (BFCCZ) were the most productive regions with the TChla levels being twice as high in the Benguela. Diatoms dominated the Benguela system, while nanoflagellates were the most ubiquitous group in the BFCCZ. Pigment concentrations were greater along the eastern boundary of the southern oligotrophic gyre and distributed at shallower depths. Deep chlorophyll maxima were a feature of the western boundary oligotrophic waters, and cyanobacteria tended to dominate the upper water column along both transects with a mixed group of nanoflagellates at the chlorophyll maximum.Absorption coefficients were estimated from spectra reconstructed from pigment data. Although absorption was greater in the productive areas, the TChla-specific coefficients were higher in oligotrophic regions. In communities that were dominated by diatoms or nanoflagellates, pigment absorption was generally uniform with depth and attenuating irradiance, with TChla being the major absorbing pigment at 440 nm and photosynthetic carotenoids (PSC) at 490 nm. Absorption by chlorophyll c and photoprotective carotenoids (PPC) was much lower. Populations where cyanobacteria were prevalent were characterized by high PPC absorption, particularly at 490 nm, throughout most of the euphotic zone. The data suggested that the effect of pigments on the variability of phytoplankton absorption was due primarily to the variations in absorption by PPC.     

Storm-induced convective export of organic matter during spring in the northeast Atlantic Ocean

Observations during a spring phytoplankton bloom in the northeast Atlantic between March and May 1992 in the Biotrans region at 47°N, 20°W, are presented. During most of the observation period there was a positive heat flux into the ocean, winds were weak, and the mixed layer depth was shallow (<40 m). Phytoplankton growth conditions were favourable during this time. Phytoplankton biomass roughly doubled within the euphotic zone over the course of about 7 days during mid-April, and rapidly increased towards the end of the study until silicate was depleted. However, the stratification of the water column was transient, and the spring bloom development was repeatedly interrupted by gales. During two storms, in late March and late April, the mixed-layer depth increased to 250 and 175 m, respectively. After the storm events significant amounts of chlorophyll-a, particulate organic carbon and biogenic silica were found well below the euphotic zone. It is estimated that between 56% and 65% of the seasonal new production between winter and early May was exported from the euphotic zone by convective mixing, in particular, during the two storm events. Data from the NABE 47°N study during spring 1989 are re-evaluated. It is found that convective particle export was of importance during the early part of that bloom too, but negligible during the height of the bloom in May 1989. The overall impact of convective particle export during spring 1989 was equivalent to about 36% of new production. In view of these and previously published findings it is concluded that convective transport during spring is a significant process for the export of particulate matter from the euphotic zone in the temperate North Atlantic.     

Metabolism of Centropages species in the Mediterranean Sea and the North Atlantic Ocean

Information on the metabolism rates of Centropages typicus and congeneric species (C. hamatus, C. furcatus, C. brachiatus and C. abdominalis) in neritic areas of the Mediterranean Sea, the North Atlantic Ocean and the Pacific Ocean are reported here. Respiration rates and excretion rates are strongly influenced by abiotic (i.e. temperature, salinity) and biotic factors (i.e. food availability and composition). Differences in the response of respiratory rates to temperature of acclimated, acclimatized and adapted individuals are clearly observed among regions of the Mediterranean Sea and the West and East shores of the Atlantic Ocean. Food supply also strongly affects respiration and excretion rates, as well as the size, sex and stage development of the individuals. The co-measurement of these two rates allows confirmation of the omnivory or carnivory oriented feeding habits of these species. The role of this neritic genus in coastal environment is also discussed.     

北极王湾2010年夏季水体营养盐分布及影响因素

王湾海域位于北极斯瓦尔巴群岛西北侧,其水体特征主要受到北极冰川与大西洋的共同影响。为了研究冰川融水与大西洋水对王湾营养盐分布以及生态系统的影响,在2010年夏季黄河站考察期间,对王湾海水与地表径流进行采样分析,并测定了营养盐和叶绿素a。结果表明:2010年夏季王湾是大西洋水影响较弱的年份,以低温低盐高营养盐的本地变异水为主导。2010年7月王湾水体可以划分为4个水团,表层水(SW)、中层变异水(TIW)、本地变异水(TLW)和大西洋变异水(TAW),其中,表层水与中层变异水营养盐浓度较低,随着深度增加,本地变异水与大西洋变异水营养盐浓度都较高。大西洋变异水主要影响200m以深水柱,其营养盐浓度低于本地变异水影响的底部值,本地变异水中营养盐浓度的增加主要来自于颗粒物中营养盐的再生。表层水主要来源于地表径流与冰川融水,这些淡水输入与浮游植物的初级生产作用共同决定了表层水的营养盐浓度水平及结构。本地变异水中在水深100m上下出现的铵盐高值可能与浮游动物和/或微生物的代谢过程有关。