Seasonal and interannual variability in particle fluxes of carbon,nitrogen and silicon from time series of sediment traps at Ocean Station P, 1982–1993: relationship to changes in subarctic primary productivity     

《Deep Sea Research Part II: Topical Studies in Oceanography》1999,46(11-12):2735-2760

An extended time series of particle fluxes at 3800 m was recorded using automated sediment traps moored at Ocean Station Papa (OSP, 50°N, 145°W) in the northeast Pacific Ocean for more than a decade (1982–1993). Time-series observations at 200 and 1000 m, and short-term measurements using surface-tethered free-drifting sediment traps also were made intermittently. We present data for fluxes of total mass (dry weight), particulate organic carbon (POC), particulate organic nitrogen (PON), biogenic Si (BSi), and particulate inorganic carbon (PIC) in calcium carbonate. Mean monthly fluxes at 3800 m showed distinct seasonality with an annual minimum during winter months (December–March), and maximum during summer and fall (April–November). Fluxes of total mass, POC, PIC and BSi showed 4-, 10-, 7- and 5-fold increases between extreme months, respectively. Mean monthly fluxes of PIC often showed two plateaus, one in May–August dominated by <63 μm particles and one in October–November, which was mainly >63 μm particles. Dominant components of the mass flux throughout the year were CaCO₃ and opal in equal amounts. The mean annual fluxes at 3800 m were 32±9 g dry weight g m⁻² yr⁻¹, 1.1±0.5 g POC m⁻² yr⁻¹, 0.15±0.07 g PON m⁻² yr⁻¹, 5.9±2.0 g BSi m⁻² yr⁻¹ and 1.7±0.6 g PIC m⁻² yr⁻¹. These biogenic fluxes clearly decreased with depth, and increased during “warm” years (1983 and 1987) of the El Niño, Southern Oscillation cycle (ENSO). Enhancement of annual mass flux rates to 3800 m was 49% in 1983 and 36% in 1987 above the decadal average, and was especially rich in biogenic Si. Biological events allowed estimates of sinking rates of detritus that range from 175 to 300 m d⁻¹, and demonstrate that, during periods of high productivity, particles sink quickly to deep ocean with less loss of organic components. Average POC flux into the deep ocean approximated the “canonical” 1% of the surface primary production.  相似文献   

Amino acid and hexosamine composition and flux of sinking particulate matter in the equatorial Pacific at 175°E longitude     

《Deep Sea Research Part I: Oceanographic Research Papers》2000,47(10):1937-1960

Sinking matter collected by sediment traps, which were deployed in the equatorial Pacific Ocean at 175°E for about 11 months during 1992–1993, were analyzed for their flux and labile components in terms of amino acids and hexosamines. The samples provided a temporal resolution of 15 days and were collected from 1357 (shallow trap) and 4363 m (deep trap) depths where sea floor depth was 4880 m. Particle flux along with major components (carbonate, organic matter, biogenic opal and lithogenic material) and amino acid parameters showed distinct temporal variations, which were more pronounced in the shallow trap relative to deep trap. A coupling between the fluxes in the shallow and deep traps was more evident during the period of maximum particle flux, which seems to be connected with the short reappearance of non-El Niño conditions in equatorial Pacific during the 1991–1993 El Niño event. The biogeochemical indicators C/N, Asp/Bala, Glu/Gaba, Bala+Gaba mol%, THAA-C% and THAA-N% implied that the increase in sinking flux was associated with upwelling and enhanced surface production. Degradation of sinking particulate organic matter between the shallow and deep traps was also evident. Occasionally higher mass and major component fluxes in the deep trap relative to the shallow trap are attributed to contribution of resuspended particulates from sea floor (nepheloid layer) or to laterally advected particulates from nearby areas. Carbonate and opal composition of the sinking flux showed a predominance of calcareous plankton; however, Asp/Gly mol ratio and Ser+Thr mol% indicated enhanced occurrence of diatoms during the periods of higher flux.  相似文献   

Time-series observation of POC fluxes estimated from 234Th in the northwestern North Pacific     

《Deep Sea Research Part I: Oceanographic Research Papers》2007,54(7):1070-1090

Time-series measurements of ²³⁴Th activities and particulate organic carbon (POC) concentrations were made at time-series stations (K1, K2, K3, and KNOT) in the northwestern North Pacific from October 2002 to August 2004. Seasonal changes in POC export fluxes from the surface layer (∼100 m) were estimated using ²³⁴Th as a tracer. POC fluxes varied seasonally from approximately 0 to 180 mg C m⁻² d⁻¹ and were higher in spring–summer than in autumn–winter. The export ratio (e-ratio) ranged from 6% to 55% and was also higher in spring–summer. Annual POC fluxes were estimated to be 31 g C m⁻² y⁻¹ in the subarctic region (station K2) and 23 g C m⁻² y⁻¹ in the region between the subarctic and subtropical gyres (station K3). POC fluxes and e-ratios in the northwestern North Pacific were much higher than those in most other oceans. The annual POC flux corresponded to 69% of annual new production estimated from the seasonal difference of the nutrient in the Western Subarctic Gyre (45 g C m⁻² y⁻¹). These results indicate that much of the organic carbon assimilated in the surface layer of the northwestern North Pacific is transferred to the deep ocean in particulate form. Our conclusions support previous reports that diatoms play an important role in the biological pump.  相似文献   

Downward transport of organic carbon by diel migratory micronekton in the western equatorial Pacific:: its quantitative and qualitative importance     

《Deep Sea Research Part I: Oceanographic Research Papers》2001,48(8):1923-1939

Using simultaneous sampling with a commercial-sized trawl, a zooplankton net, and a sediment trap, we evaluated the contribution of vertically migrating micronekton to vertical material transport (biological pump) at two stations (3°00′N, 146°00′E and 3°30′N, 145°20′E) in the western equatorial North Pacific. The gravitational sinking particulate organic carbon flux out of the euphotic zone was 54.8 mg C m⁻² day⁻¹. The downward active carbon flux by diel migrant mesozooplankton was 23.53 and 9.97 mg C m⁻² day⁻¹, and by micronekton 4.40 and 2.26mg C m⁻² day⁻¹ at the two stations. Assuming that the micronekton sampling efficiency of the trawl was 14%, we corrected the downward carbon flux due to micronekton respiration to 29.9 and 15.2mg C m⁻² day⁻¹, or 54.6 and 27.7% of the sinking particle flux at the two stations. The corrected micronekton gut fluxes were 1.53 and 0.97mg C m⁻² day⁻¹. The role of myctophid fish fecal matter as a possible food resource for deep-sea organisms, based on its fatty acid and amino acid analysis, is discussed.  相似文献   

On the size of the Peru upwelling ecosystem     

《Deep Sea Research Part I: Oceanographic Research Papers》2001,48(11):2521-2528

Previously published estimates of the area of the Peru upwelling ecosystem vary by more than an order of magnitude. In an effort to improve this situation, we used a 24-month sequence of SeaWiFS satellite images of chlorophyll in the surface water off Peru from 5°S to 18.5°S during September 1997–August 1999 to estimate the size of the nutrient enhanced productive habitat associated with the upwelling. The first 12-month period was marked by El Niño conditions, the second by strong upwelling. Using a chlorophyll threshold of >1.0 mg m⁻³ to define the limit of the productive habitat resulted in maximum area estimates of 120×10³ km² during September 1997–August 1998, and 220×10³ km² during September 1998–August 1999. The latter result is consistent with an area estimate we calculated using total fishery landings and a regression relating fishery yields per unit area to annual primary production per unit area. Although year-to-year variation in the annual mean size of the upwelling ecosystem must be significant, even discounting El Niño events, our analysis has shown that at least five of the extreme earlier values are not good estimates of the size of the productive habitat. We may now be close to knowing the average size of the ecosystem to within a factor of about two.  相似文献   

Anomalous hydrographic and biological conditions in the northern South China Sea during the 1997–1998 El Niño and comparisons with the equatorial Pacific     

Chun-Mao Tseng  K.-K. Liu  L.-W. Wang  G.-C. Gong 《Deep Sea Research Part I: Oceanographic Research Papers》2009,56(12):2129-2143

It is demonstrated that weakened wind mixing and strengthened water column stratification resulted in the anomalously low sea surface chlorophyll in the northern South China Sea during the 1997–1998 El Niño event. Remotely sensed sea surface temperature, wind and chlorophyll, which were validated by shipboard observations at the SouthEast Asian Time-series Study (SEATS) station (18°N, 116°E) in the northern South China Sea (SCS) provided the basis for this study. During the 1997–1998 winter at the SEATS station, the sea surface temperature was elevated by about 2 °C above the climatological mean, while the wind speed of the northeast monsoon was reduced from a climatological mean of 9.4 to 6.8 m/s. The concentration of surface chlorophyll-a dropped from 0.2 to 0.1 mg/m³. The monthly area-averaged integrated primary production estimated for the northern SCS area (112–119°E, 15–21°N) was reduced by about 40% of the normal winter value. Under the anomalously high sea surface temperature and weak monsoon, the mixed-layer depth would have been reduced from an average of 65 to 45 m and the nutrients in the mixed layer would have been reduced by half, according to observations at the SEATS station in more recent years. During the 1997–1998 El Niño event, the onset of warming in the northern SCS lagged behind that in the eastern equatorial Pacific by about 5 months and lingered for 11 months. This course of change resembled that of the western Pacific warm pool region. However, contrary to the northern SCS, the sea surface chlorophyll was enhanced in the warm pool region during the event, probably mainly because of the uplifted nutricline. Unlike the eastern equatorial Pacific, the dramatic recovery of biological production did not happen in the SCS in the summer of 1998. These distinctive biogeochemical responses reflect fundamental differences between the SCS and the equatorial Pacific in terms of upper water column dynamics.  相似文献   

Variability in upper-ocean water properties in the NE Pacific Ocean     

《Deep Sea Research Part II: Topical Studies in Oceanography》1999,46(11-12):2351-2370

A review of oceanographic properties in the vicinity of Ocean Station Papa (OSP) is presented, using data collected over the past 42 years. Average annual signals at OSP and seasonal characteristics along Line P represent variability on a large scale in the Gulf of Alaska. Between winter and summer, the upper ocean mixed layer varies between 120 and 40 m, monthly average winds decrease from 12 m/s in winter to 7 m/s in July, seawater temperatures warm from lows of 6°C to highs >12°C, waters freshen slightly in summer, and macronutrients are partially depleted by phytoplankton growth (removal of 7.8 μM NO₃ in 1970s and 6.5 μM NO₃ in 1990s). El Niño events influence this area by transporting heat northward. During the prolonged El Niño of the early 1990s, warming persisted at OSP through 1994, resulting in a reduced macronutrient supply during winter mixing. Changes in water properties over the four decades of observations are evident. There are trends towards warmer and less saline surface waters, lower winter nitrate and silicate levels, and less macronutrient utilisation in the 1990s compared to the 1970s. We speculate that these changes must be reducing the productivity of NE subarctic Pacific waters.  相似文献   

ENSO related variations in biogeochemistry of AA and HA in settling particles along the equatorial Pacific Ocean     

Lallan P. Gupta  Hodaka Kawahata 《Journal of Oceanography》2007,63(4):695-709

Four year-long time-series sediment trap experiments were conducted along the equatorial Pacific Ocean in order to understand the biogeochemistry of particulate organic matter (POM) on the basis of amino acid (AA) and hexosamine (HA) compositions of the settling particles. Total mass flux in the study area varied over 4 orders of magnitude without a common seasonality among all trap sites. Planktonic blooms were apparent in terms of total mass and AA fluxes at the easternmost end of the Niño-4 region. AA fluxes closely followed the total mass flux profiles, suggesting that increased particle flux delivered a greater amount of labile OM to the deep ocean. A labile OM index (LI)-based classification showed that during the El Niño conditions in 2002, the eastern side of the equatorial Pacific transported relatively more labile OM than the western equatorial Pacific. An overall change in AA and HA composition of settling particles could be revealed with the help of discriminant analysis, suggesting that settling particles during El Niño were compositionally different from those settling during La Niña condition in the equatorial Pacific.  相似文献   

Export flux in the western and central equatorial Pacific: zonal and temporal variability     

《Deep Sea Research Part I: Oceanographic Research Papers》2000,47(5):901-936

  相似文献   

Biogenic fluxes in the Cariaco Basin: a combined study of sinking particulates and underlying sediments     

《Deep Sea Research Part I: Oceanographic Research Papers》2003,50(6):781-807

The fluxes of total mass, organic carbon (OC), biogenic opal, calcite (CaCO₃) and long-chain C₃₇ alkenones (ΣAlk₃₇) were measured at three water depths (275, 455 and 930 m) in the Cariaco Basin (Venezuela) over three separate annual upwelling cycles (1996–1999) as part of the CARIACO sediment trap time-series. The strength and timing of both the primary and secondary upwelling events in the Cariaco Basin varied significantly during the study period, directly affecting the rates of primary productivity (PP) and the vertical transport of biogenic materials. OC fluxes showed a weak positive correlation (r²=0.3) with PP rates throughout the 3 years of the study. The fluxes of opal, CaCO₃ and ΣAlk₃₇ were strongly correlated (0.6<r²<0.8) with those of OC. The major exception was the lower than expected ΣAlk₃₇ fluxes measured during periods of strong upwelling. All sediment trap fluxes were significantly attenuated with depth, consistent with marked losses during vertical transport. Annually, strong upwelling conditions, such as those observed during 1996–1997, led to elevated opal fluxes (e.g., 35 g m⁻² yr⁻¹ at 275 m) and diminished ΣAlk₃₇ fluxes (e.g., 5 mg m⁻² yr⁻¹ at 275 m). The opposite trends were evident during the year of weakest upwelling (1998–1999), indicating that diatom and haptophyte productivity in the Cariaco Basin are inversely correlated depending on upwelling conditions.The analyses of the Cariaco Basin sediments collected via a gravity core showed that the rates of OC and opal burial (10–12 g m⁻² yr⁻¹) over the past 5500 years were generally similar to the average annual water column fluxes measured in the deeper traps (10–14 g m⁻² yr⁻¹) over the 1996–1999 study period. CaCO₃ burial fluxes (30–40 g m⁻² yr⁻¹), on the other hand, were considerably higher than the fluxes measured in the deep traps (∼10 g m⁻² yr⁻¹) but comparable to those obtained from the shallowest trap (i.e. 38 g m⁻² yr⁻¹ at 275 m). In contrast, the burial rates of ΣAlk₃₇ (0.4–1 mg m⁻² yr⁻¹) in Cariaco sediments were significantly lower than the water column fluxes measured at all depths (4–6 mg m⁻² yr⁻¹), indicating the large attenuation in the flux of these compounds at the sediment–water interface. The major trend throughout the core was the general decrease in all biogenic fluxes with depth, most likely due to post-depositional in situ degradation. The major exception was the relatively low opal fluxes (∼5 g m⁻² yr⁻¹) and elevated ΣAlk₃₇ fluxes (∼2 mg m⁻² yr⁻¹) measured in the sedimentary interval corresponding to 1600–2000 yr BP. Such compositions are consistent with a period of low diatom and high haptophyte productivity, which based on the trends observed from the sediment traps, is indicative of low upwelling conditions relative to the modern day.  相似文献   

Regional variations in the fluxes of foraminifera carbonate,coccolithophorid carbonate and biogenic opal in the northern Indian Ocean     

《Deep Sea Research Part I: Oceanographic Research Papers》2006,53(2):271-293

Mass fluxes of diatom opal, planktonic foraminifera carbonate and coccolithophorid carbonate were measured with time-series sediment traps at six sites in the Arabian Sea, Bay of Bengal and Equatorial Indian Ocean (EIOT). The above fluxes were related to regional variations in salinity, temperature and nutrient distribution. Annual fluxes of diatom opal range between 3 and 28 g m⁻² yr⁻¹, while planktonic foraminifera carbonate fluxes range between 6 and 23 g m⁻² yr⁻¹ and coccolithophorid carbonate fluxes range between 4 and 24 g m⁻² yr⁻¹. Annual planktonic foraminifera carbonate to coccolithophorid carbonate ratios range between 0.8 and 2.2 and coccolithophorid carbonate to diatom opal ratios range between 0.5 and 3.3.In the western Arabian Sea, coccolithophorids are the major contributors to biogenic flux during periods of low nutrient concentrations. Coccolithophorid carbonate fluxes decrease and planktonic foraminiferal carbonate and diatom opal fluxes increase when nutrient-rich upwelled waters are advected over the trap site. In the oligotropic eastern Arabian Sea, coccolithophorid carbonate fluxes are high throughout the year. Planktonic foraminiferal carbonate fluxes are the major contributors to biogenic flux in the EIOT. In the northern and central Bay of Bengal, when surface salinity values drop sharply during the SW monsoon, there is a drastic reduction in planktonic foraminiferal carbonate fluxes, but coccolithophorid carbonate and diatom opal fluxes remain steady or continue to increase. Distinctly higher annual molar Si_bio/C_inorg (>1) and C_org/C_inorg (>1.5) ratios are observed in the northern and central Bay of Bengal mainly due to lower foraminiferal carbonate production as a result of sharp salinity variations. We can thus infer that the enhanced freshwater supply from rivers should increase oceanic CO₂ uptake. Its silicate supply favours the production of diatoms while the salinity drop produces conditions unfavourable for most planktonic foraminifera species.  相似文献   

Lithogenic and biogenic particle fluxes on the Lomonosov Ridge (central Arctic Ocean) and their relevance for sediment accumulation: Vertical vs. lateral transport     

《Deep Sea Research Part I: Oceanographic Research Papers》2007,54(8):1256-1272

Investigations of lithogenic and biogenic particle fluxes using long-term sediment traps are still very rare in the northern high latitudes and are restricted to the arctic marginal seas and sub-arctic regions. Here data on the variability of fluxes of lithogenic matter, CaCO₃, opal, and organic carbon and biomarker composition from the central Arctic Ocean are presented for a 1-year period. The study was carried out on material obtained from a long-term mooring system equipped with two multi-sampling traps, at 150 and 1550 m depth, and deployed on the southern Lomonosov Ridge close to the Laptev Sea continental margin from September 1995 to August 1996. In addition, data from surface sediments were included in the study. Annual fluxes of lithogenic matter, CaCO₃, opal, and particulate organic carbon were 3.9, 0.8, 2.6, and 1.5 g m⁻² y⁻¹, respectively, in the shallow trap and 11.3, 0.5, 2.9, and 1.05 g m⁻² y⁻¹, respectively, in the deep trap.Both the shallow and the deep trap showed significant variations in vertical flux over the year. Higher values were found from mid-July to the end of October (total mass flux of 75–130 mg m⁻² d⁻¹ in the shallow trap and 40–225 mg m⁻² d⁻¹ in the deep trap). During all other months, fluxes were fairly low in both traps (most total mass flux values <10 mg m⁻² d⁻¹). The interval of increased fluxes can be separated into (1) a mid-July/August maximum caused by increased primary production as documented in high abundances of marine biomarkers and diatoms and (2) a September/October maximum caused by increased influence of Lena River discharge indicated by maximum lithogenic flux and large amounts of terrigenous/fluvial biomarkers in both traps. During September/October, total mass fluxes in the deep trap were significantly higher than in the shallow trap, suggesting a lateral sediment flux at greater depth. The lithogenic flux data also support the importance of sediment input from the Laptev Sea for the sediment accumulation on the Lomonosov Ridge on geological time scales, as indicated in sedimentary records from this region.  相似文献   

Suspended particle organic composition and cycling in surface and midwaters of the equatorial Pacific Ocean     

《Deep Sea Research Part I: Oceanographic Research Papers》2002,49(11):1983-2008

In this study we relate spatial and temporal variation in the organic composition of suspended particles to current conceptual models of open-ocean particle cycling. Suspended particles in surface (0–200 m) and midwaters (200–1000 m) of the equatorial Pacific Ocean were collected during the 1992 US JGOFS Equatorial Pacific (EqPac) program. Samples collected during El Niño (Survey I) and normal conditions (Survey II) were analyzed for pigment, amino acid, fatty acid, and neutral lipid concentrations and compositions. Principal Components Analysis (PCA) and other statistical methods were used to assess changes in particulate organic composition between Surveys I and II, over 24° of latitude, from 15 to 850 m depth, and to compare our compositional data with previously published data from EqPac sinking particles. These analyses indicated that surface suspended particles (0–200 m) were similar in composition to surface ocean phytoplankton and were less degraded than particles sinking out of the euphotic zone (105 m). The organic composition of suspended particles in surface waters varied with latitudinal and El-Niño-induced changes in phytoplankton assemblages. Midwater suspended particles (200–1000 m) contained labile phytodetrital material derived from particles exiting the euphotic zone (105 m). However, labile organic constituents of midwater suspended particles were increasingly degraded by microbes or consumed by midwater metazoans with depth. The increase in degradation state observed for midwater suspended particles may also have been caused by dilution of deeper (450–850 m) suspended particle pools with more refractory material originating from fast-sinking particles, e.g., fecal pellets. However, the mechanism controlling midwater particle degradation state varied with flux regime; dilution of midwater suspended particles dominated only in the higher flux regime found at equatorial latitudes (5°N–5°S) during Survey II (normal conditions). In summary, it is apparent that organic matter alteration in midwaters, and not cycling within the euphotic zone, has the larger effect on organic composition of suspended particles in the deep equatorial Pacific Ocean.  相似文献   

Silicon flux and distribution of biogenic silica in deep-sea sediments in the western North Pacific Ocean     

Yoko Shibamoto  Koh Harada 《Deep Sea Research Part I: Oceanographic Research Papers》2010,57(2):163-174

We investigated biogenic silica, several biological components, and silicate in pore-water in the abyssal sediment to determine silicon flux of western North Pacific during several cruises. The surficial sediment biogenic silica content was high at high latitudes with the boundary running along the Kuroshio Extension, and maximum values (exceeding 20%) were found in the Oyashio region. In the subtropical region to the south, most stations showed less than 5% biogenic silica content. This distribution pattern reflected primary production and ocean currents in the surface layer very well. Pore-water samples were collected from 4 stations along the east coast of Japan. The highest asymptotic silicic acid concentration (670 μmol L^?1) in pore-water was observed at the junction of Kuroshio and Oyashio, followed by samples from the Oyashio region. It is at the southern station that the lowest value (450 μmol L^?1) was observed, and the primary production is low under the influence of Kuroshio there. The diffusive flux followed the same geographic trend as the asymptotic silicic acid concentrations did, ranging 77–389 mmol m^?2 yr ^?1. Multiple sampling of pore-water was conducted throughout the year at one station at high latitude. The average annual biogenic silica rain flux observed using sediment traps was 373 mmol m^?2 yr^?1; the diffusive flux and burial flux at the sediment–water interface were 305 and 9 mmol m^?2 yr^?1, respectively. We concluded that most of the settling silica particles dissolved and diffused at the sediment–water interface and approximately 3% only were preserved in this area. In addition, the obvious time lag observed between the peak rain flux and the maximum diffusive flux suggested that primary production in the surface layer has a great influence on the sedimentation environment of abyssal western North Pacific. These transitions of Si flux at the sediment–water interface were considerably greater in northwestern North Pacific than in southwestern North Pacific. In addition, a station in the Philippine Sea indicated high biogenic silica content because of Ethmodiscus ooze, which are scattered randomly on the sea floor in the subtropical region.  相似文献   

Oxygen dynamics in the North Atlantic subtropical gyre     

《Deep Sea Research Part II: Topical Studies in Oceanography》2013

Dissolved oxygen (DO) in the ocean is a tracer for most ocean biogeochemical processes including net community production and remineralization of organic matter which in turn constrains the biological carbon pump. Knowledge of oxygen dynamics in the North Atlantic Ocean is mainly derived from observations at the Bermuda Atlantic Time-series Study (BATS) site located in the western subtropical gyre which may skew our view of the biogeochemistry of the subtropical North Atlantic. This study presents and compares a 15 yr record of DO observations from ESTOC (European Station for Time-Series in the Ocean, Canary Islands) in the eastern subtropical North Atlantic with the 20 yr record at BATS. Our estimate for net community production of oxygen was 2.3±0.4 mol O₂ m⁻² yr⁻¹ and of oxygen consumption was −2.3±0.5 mol O₂ m⁻² yr⁻¹ at ESTOC, and 4 mol O₂ m⁻² yr⁻¹ and −4.4±1 mol m⁻² yr⁻¹ at BATS, respectively. These values were determined by analyzing the time-series using the Discrete Wavelet Transform (DWT) method. These flux values agree with similar estimates from in-situ observational studies but are higher than those from modeling studies. The difference in net oxygen production rates supports previous observations of a lower carbon export in the eastern compared to the western subtropical Atlantic. The inter-annual analysis showed clear annual cycles at BATS whereas longer cycles of nearly 4 years were apparent at ESTOC. The DWT analysis showed trends in DO anomalies dominated by long-term perturbations at a basin scale for the consumption zones at both sites, whereas yearly cycles dominated the production zone at BATS. The long-term perturbations found are likely associated with ventilation of the main thermocline, affecting the consumption and production zones at ESTOC.  相似文献   

Particulate carbon and nitrogen fluxes and compositions in the central equatorial Pacific     

《Deep Sea Research Part I: Oceanographic Research Papers》2001,48(9):1999-2023

Mass, carbon, and nitrogen fluxes and carbon and nitrogen compositions were determined for particulate samples from plankton net tows, shallow floating sediment traps, intermediate and deep moored sediment traps, and sediment cores collected along 140°W in the central equatorial Pacific Ocean during the US JGOFS EqPac program. Mass, particulate organic carbon (POC), and particulate inorganic carbon (PIC) fluxes measured by the floating sediment traps during the Survey I (El Niño) and Survey II (non-El Niño) cruises follow essentially the same pattern as primary production: high near the equator and decreasing poleward. POC fluxes caught in free-floating traps were compared with alternative estimates of export fluxes, including ²³⁴Th models, new production, and other sediment trap studies, resulting in widely differing estimates. Applying ²³⁴Th corrections to the trap-based fluxes yielded more consistent results relative to primary production and new production. Despite factors of five differences in measured fluxes between different trap types, POC : ²³⁴Th ratios of trap material were generally within a factor of two and provided a robust means of converting modeled ²³⁴Th export fluxes to POC export fluxes. All measured fluxes decrease with depth. Trap compositional data suggest that mineral “ballasting” may be a prerequisite for POC settling. POC remineralization is most pronounced in the epipelagic zone and at the sediment–water interface, with two orders of magnitude loss at each level. Despite seawater supersaturation with respect to calcium carbonate in the upper ocean, 80% of PIC is dissolved in the epipelagic zone. Given the time-scale differences of processes throughout the water column, the contrasting environments, and the fact that only 0.01% of primary production is buried, sedimentary organic carbon accumulation rates along the transect are remarkably well correlated to primary production in the overlying surface waters. POC to particulate total nitrogen (PTN) ratios for all samples are close to Redfield values, indicating that POC and PTN are non-selectively remineralized. This constancy is somewhat surprising given conventional wisdom and previous equatorial Pacific results suggesting that particulate nitrogen is lost preferentially to organic carbon.  相似文献   

El Niño/Southern Oscillation (ENSO) Related Variations in Particulate Export Fluxes in the Western and Central Equatorial Pacific     

Hodaka Kawahata  Lallan Prasad Gupta 《Journal of Oceanography》2003,59(5):663-670

Time-series data from sediment trap moorings intermittently deployed during 1991–1999 show that the fluxes of biogenic material (carbonate, opal and organic matter, including amino acids) and other related parameters are temporally and spatially distinct across the Western Pacific Warm Pool (WPWP). These variations resulted from the El Niño and La Niña conditions, which alternately prevailed over the equatorial Pacific Ocean during the mooring deployments. The westernmost WPWP (a hemipelagic region) recorded relatively high average total mass and amino acid fluxes during the El Niño event. This was in sharp contrast to the eastern part of the WPWP (oligotrophic and weak upwelling regions) which recorded higher flux values during the La Niña event. Settling particulate organic matter was rich in labile components (amino acids) during La Niña throughout the study area. Relative molar ratios of aspartic acid to β-alanine together with relative molar content of non-protein amino acids β-alanine and γ-aminobutyric acid) suggested that organic matter degradation was more intense during La Niña relative to that during El Niño in the WPWP. This study clearly shows that during an El Niño event the well documented decrease in export flux in the easternmost equatorial Pacific is accompanied by a significant increase in export flux in the westernmost equatorial Pacific Ocean.  相似文献   

High primary productivity and f-ratio in summer in the Ulleung basin of the East/Japan Sea     

《Deep Sea Research Part I: Oceanographic Research Papers》2013

To better understand the cause of high summer primary productivity in the Ulleung Basin located in the southwest part of the East/Japan Sea, the spatial dynamics of primary, new, and regenerated productivities (PP, NP, and RP) were examined along the path of the Tsushima Warm Current system in summer 2008. We compared hydrographic and chemical parameters in the Ulleung Basin with those of the Kuroshio Current in the Western Pacific Ocean and the East China Sea. In summer, integrated primary productivity (IPP, 0.37–0.96 g C m⁻² d⁻¹) and integrated new productivity (INP, 26–221 mg N m⁻² d⁻¹) within the euphotic zone in the Ulleung Basin were higher than those in the East China Sea and the Western Pacific Ocean (0.17–0.28 g C m⁻² d⁻¹, 2−5 mg N m⁻² d⁻¹, respectively). In contrast, there was no pronounced spatial variation in integrated regenerated productivity (IRP, 43–824 mg N m⁻² d⁻¹). Strong positive correlations between IPP and INP (also the f-ratio), and between nitrate uptake rate in the mixed layer and nitrate upward flux through the top of pycnocline in summer in the Ulleung Basin imply that the high IPP was mainly supported by supply of nitrate from the underlying water in the euphotic zone. Shallowing of the pycnocline depth as the current enters the East/Japan Sea facilitates nitrate supply from the nutrient-replete cold water immediately below the pycnocline through nitrate upward flux. A subsurface maximum in PP at or above the pycnocline and a high f-ratio further support the importance of this source of nitrate for maintaining the high summer PP in the Ulleung Basin. In comparison, the high PP layer was observed at the surface in the following fall and spring in the Ulleung Basin. Our results demonstrate the importance of hydrographic features in enhancing PP in this oligotrophic Tsushima Warm Current system.  相似文献   

Ascending and descending particle flux from hydrothermal plumes at Endeavour Segment,Juan de Fuca Ridge     

《Deep Sea Research Part I: Oceanographic Research Papers》2001,48(4):1093-1120

Bio-acoustic surveys and associated zooplankton net tows have documented anomalously high concentrations of zooplankton within a 100 m layer above the hydrothermal plumes at Endeavour Segment, Juan de Fuca Ridge. These and other data suggest that congregating epi-plume zooplankton are exploiting a food substrate associated with the hydrothermal plume. Ascending, organic-rich particles could provide a connection. Consequently, two paired sequentially sampling ascending and descending particle flux traps and a current meter were deployed on each of three moorings from July 1994 to May 1995. Mooring sites included an on-axis site (OAS; 47°57.0′N, 129°05.7′W) near the main Endeavour vent field, a “down-current” site 3 km west of the main vent field (WS), and a third background station 43 km northeast of the vent field (ES). Significant ascending and descending particle fluxes were measured at all sites and depths. Lipid analyses indicated that ascending POC was derived from mid-depth and deep zooplankton whereas descending POC also contained a component of photosynthetically derived products from the sea surface. Highest ascending POC fluxes were found at the hydrothermal plume-swept sites (OAS and WS). The limited data available, however, precludes an unequivocal conclusion that hydrothermal processes contribute to the ascending flux of organic carbon at each site. Highest ascending to descending POC flux ratios were also found at WS. Observed trends in POC, PMn/PTi, and PFe/PTi clearly support a hydrothermal component to the descending flux at the plume-swept WS site (no descending data was recovered at OAS) but not at the background ES site. Alternative explanations for ascending particle data are discussed. First-order calculations for the organic carbon input (5–22 mg C m⁻² d⁻¹) required to sustain observed epi-plume zooplankton anomalies at Endeavour are comparable both to measured total POC flux to epi-plume depths (2–5 mg C m⁻² d⁻¹: combined hydrothermal and surface derived organic carbon) and to estimates of the total potential in situ organic carbon production (2–9 mg C m⁻² d⁻¹) from microbial oxidation of hydrothermal plume H₂, CH₄ and NH₄⁺.  相似文献   

High-frequency fluxes of labile compounds in the central Ligurian Sea,northwestern Mediterranean     

《Deep Sea Research Part I: Oceanographic Research Papers》2000,47(3):533-556

Sinking particles were collected every 4 h with drifting sediment traps deployed at 200 m depth in May 1995 in a 1-D vertical system during the DYNAPROC observations in the northwestern Mediterranean sea. POC, proteins, glucosamine and lipid classes were used as indicators of the intensity and quality of the particle flux. The roles of day/night cycle and wind on the particle flux were examined. The transient regime of production from late spring bloom to pre-oligotrophy determined the flux intensity and quality. POC fluxes decreased from, on average, 34 to 11 mg m⁻² d⁻¹, representing 6–14% of the primary production under late spring bloom conditions to 1–2% under pre-oligotrophic conditions. Total protein and chloroplast lipid fluxes correlated with POC and reflected the input of algal biomass into the traps. As the season proceeded, changes in the biochemical composition of the exported material were observed. The C/N ratio rose from 7.8 to 12. Increases of serine (10–28% of total proteins), total lipids (7–9 to 14–28% of POC) and reserve lipids (1–5 to 5–22% of total lipids) were noticeable, whereas total protein content in POC decreased (20–27 to 18–7%). N-acetyl glucosamine, a tracer of fecal pellet flux, showed that zooplankton grazing was a major vector of downward export during the decaying bloom. Against this background pattern, episodic events specifically increased the flux, modifying the quality and the settling velocity of particles. Day/night signals in biotracers (POC, N-acetyl glucosamine, protein and chloroplast lipids) showed that zooplankton migrations were responsible for sedimentation of fresh material through fast sinking particles (V=170–180 m d⁻¹) at night. Periodic signatures of re-processed material (high lipolysis and bacterial biomass indices) suggested that other zooplankton fecal pellets or small aggregates, probably of lower settling velocities (V<170 m d⁻¹), contributed to the flux during calm periods. At the beginning of the experiment, during the development of a prymnesiophyte bloom in the upper layers, the sterol signal with no periodicity enabled us to estimate high particle settling velocities (⩾600 m d⁻¹) likely related to large aggregate formation. A wind event increased biotracer fluxes (POC, protein, chloroplast lipids). The rapid transmission of surface signals through extremely fast sinking particles could be a general feature of particle fluxes in marine areas unaffected by horizontal advection.  相似文献