The metabolic balance between autotrophy and heterotrophy in the western Arctic Ocean     

《Deep Sea Research Part I: Oceanographic Research Papers》2006,53(11):1831-1844

The goal of this study was to explore how net community production (NCP) is influenced by the relationship between primary production and community respiration in the western Arctic Ocean. Plankton NCP and respiration were determined by measuring changes in oxygen in light and dark bottle incubations, respectively. Rates of NCP averaged over shelf, slope and basin waters were positive in summer 2002 (57±191 mmol O₂ m⁻² d⁻¹) and spring 2004 (85±86 mmol O₂ m⁻² d⁻¹) and negative in summer 2004 (−25±176 mmol O₂ m⁻² d⁻¹). Determinations of NCP obtained from bottle incubations were similar to rates inferred from in situ changes in dissolved inorganic carbon. An examination of the spatial variability of primary production and community respiration indicated that respiration is distributed more uniformly than primary production. A spatial offset between photosynthesis and respiration from the shelf to the Arctic basin was present in spring 2004, but was not seen at other times. NCP and the potential for export appear to be dependent on an uncoupling of primary production and community respiration. NCP continued into the summer after the stock of NO₃⁻ had been depleted. Our data suggest that the uniform distribution of respiration relative to primary production is an important factor influencing NCP and the potential for export in the western Arctic.  相似文献   

Vertical distribution of zooplankton and active flux across an anticyclonic eddy in the Canary Island waters     

《Deep Sea Research Part I: Oceanographic Research Papers》2005,52(1):69-83

The vertical distribution (0–900 m) of zooplankton biomass and indices of feeding (gut fluorescence, GF) and metabolism (electron transfer system, ETS) were studied across an anticyclonic eddy south of Gran Canaria Island (Canary Islands). Two dense layers of organisms were clearly observed during the day, one above 200 m and the other at about 500 m, coincident with the deep scattering layer (DSL). The biomass displacement due to interzonal migrants in the euphotic zone was more than 2-fold higher than that previously reported for the southern area of this archipelago. The gut flux estimated (0.14–0.44 mgC m⁻² d⁻¹) was similar to the values previously found in the Canaries. The respiratory flux outside the eddy (1.85 mgC m⁻² d⁻¹) was in the lower range of values reported for this area. Inside the eddy, migrant biomass and respiration rates were 2- and 4- fold higher than in the surrounding waters. Active flux mediated by diel vertical migrants inside the eddy (8.28 mgC m⁻² d⁻¹) was up to 53% of the passive carbon flux to the mesopelagic zone (15.8 mgC m⁻² d⁻¹). It is, therefore, suggested that the anticyclonic eddy enhanced both migration from deep waters and active flux.  相似文献   

Seasonal dynamics of primary and new production in the northern South China Sea: The significance of river discharge and nutrient advection     

《Deep Sea Research Part I: Oceanographic Research Papers》2006,53(6):971-986

Biochemical and productivity measurements and nutrient enrichment experiments were conducted on three cruises in summer and two cruises in winter on the shelf and the basin of the northern South China Sea (SCS) between 2001 and 2004. Phytoplankton production, in terms of depth-integrated new production (INP) or depth-integrated primary production (IPP), was higher in winter than in summer and on the shelf than in the basin. In winter, with deepening of the mixed layer, nitrate from the shallow nitracline that characterized the SCS waters was made available in the surface and supported the highest production of the year. Averaged INP measured in winter (0.25 g C m⁻² d⁻¹) was about twice the summer average (0.12 g C m⁻² d⁻¹) and was 0.19 g C m⁻² d⁻¹ on the shelf compared with 0.15 g C m⁻² d⁻¹ in the basin. In winter, average INP on the shelf was higher than the basin (0.34 versus 0.21 g C m⁻² d⁻¹); whereas in summer, averaged INP on the shelf (0.13 g C m⁻² d⁻¹) and the basin (0.11 g C m⁻² d⁻¹) were similar. While averaged IPP measured in the basin was higher in winter than in summer (0.53 versus 0.35 g C m⁻² d⁻¹), IPP on the shelf showed little temporal variation (0.82 in winter versus 0.84 g C m⁻² d⁻¹ in summer). Considerable spatial and inter-annual variation in production was measured in the shelf waters during summer, which could be linked to discharge volume and plume flow direction of the Zhujiang River. While the shelf waters in summer were mostly nitrogen starved or nitrogen and phosphorus co-limited, excessive river runoff may cause the nutritive state to shift to phosphorus deficiency. Waters with low surface salinities and high fluorescence from riverine mixing could be found extending from the Zhujiang mouth to as far as offshore southern Taiwan after a typhoon passed the northern SCS and brought heavy rainfall. Overall, both nutrient advection in winter and river discharge from the China coast in summer made new nitrogen available and shaped the dynamics of phytoplankton production in these oligotrophic waters.  相似文献   

Latitudinal distribution of microbial plankton abundance,production, and respiration in the Equatorial Atlantic in autumn 2000     

《Deep Sea Research Part I: Oceanographic Research Papers》2005,52(5):861-880

Phytoplankton and bacterial abundance, size-fractionated phytoplankton chlorophyll-a (Chl-a) and production together with bacterial production, microbial oxygen production and respiration rates were measured along a transect that crossed the Equatorial Atlantic Ocean (10°N–10°S) in September 2000, as part of the Atlantic Meridional Transect 11 (AMT 11) cruise. From 2°N to 5°S, the equatorial divergence resulted in a shallowing of the pycnocline and the presence of relatively high nitrate (>1 μM) concentrations in surface waters. In contrast, a typical tropical structure (TTS) was found near the ends of the transect. Photic zone integrated ¹⁴C primary production ranged from ∼200 mg C m⁻² d⁻¹ in the TTS region to ∼1300 mg C m⁻² d⁻¹ in the equatorial divergence area. In spite of the relatively high primary production rates measured in the equatorial upwelling region, only a moderate rise in phytoplankton biomass was observed as compared to nearby nutrient-depleted areas (22 vs. 18 mg Chl-a m⁻², respectively). Picophytoplankton were the main contributors (>60%) to both Chl-a biomass and primary production throughout the region. The equatorial upwelling did not alter the phytoplankton size structure typically found in the tropical open ocean, which suggests a strong top-down control of primary producers by zooplankton. However, the impact of nutrient supply on net microbial community metabolism, integrated over the euphotic layer, was evidenced by an average net microbial community production within the equatorial divergence (1130 mg C m⁻² d⁻¹) three-fold larger than net production measured in the TTS region (370 mg C m⁻² d⁻¹). The entire region under study showed net autotrophic community metabolism, since respiration accounted on average for 51% of gross primary production integrated over the euphotic layer.  相似文献   

Microbial respiration in the Levantine Sea: evolution of the oxidative processes in relation to the main Mediterranean water masses     

《Deep Sea Research Part I: Oceanographic Research Papers》2001,48(10):2147-2159

First data on microbial respiration in the Levantine Sea are reported with the aim of assessing the distribution of oxidative processes in association with the main Mediterranean water masses and the changing physical structure determined by the Eastern Mediterranean Transient. Respiratory rates, in terms of metabolic carbon dioxide production, were estimated from measured electron transport system activities in the polygonal area of the Levantine Sea (32.5–36.5 N Latitude, 26.0–30.25 E Longitude) and at Station Geo’95, in the Ionian Sea (35°34.88 N; 17°14.99 E). At the Levantine Sea, the mean carbon dioxide production rate decreased from the upper to the deeper layers and varied from 22.0±12.4 μg C h⁻¹ m⁻³ in the euphotic layer to 1.30±0.5 μg C h⁻¹ m⁻³ in the depth range between 1600 and 3000 m. Significant differences were found among upper, intermediate and bottom layers. The euphotic zone supported a daily carbon dioxide production of 96.6 mg C d⁻¹ m⁻² while the aphotic zone (between 200 and 3000 m) sustained a 177.1 mg C d⁻¹ m⁻² carbon dioxide production. In Station Geo’95, the carbon dioxide production rates amounted to 170.4 and 102.2 mg C d⁻¹ m⁻² in the euphotic and aphotic zones, respectively. The rates determined in the identified water masses showed a tight coupling of respiratory processes and Mediterranean circulation patterns. The increasing respiratory rates in the deep layers of the Levantine Sea are explained by the introduction of younger waters recently formed in the Aegean Sea.  相似文献   

Primary productivity,differential size fraction and pigment composition responses in two Southern Ocean in situ iron enrichments     

《Deep Sea Research Part I: Oceanographic Research Papers》2007,54(5):747-773

Two in situ iron-enrichment experiments were conducted in the Pacific sector of the Southern Ocean during summer 2002 (SOFeX). The “north patch,” established within the Subantarctic Zone (∼56°S), was characterized by high nitrate (∼21 mmol m⁻³) but low silicic acid (2 mmol m⁻³) concentrations. North patch iron enrichment increased chlorophyll (Chl) by 12-fold to 2.1 mg m⁻³ and primary productivity (PP_EU) by 8-fold to 188 mmol C m⁻² d⁻¹. Surprisingly, despite low silicic acid concentrations, diagnostic pigment and size-fraction composition changes indicated an assemblage shift from prymnesiophytes toward diatoms. The “south patch,” poleward of the Southern Boundary of the Antarctic Circumpolar Current (SBACC) (∼66°S), had high concentrations of nitrate (∼27 mmol m⁻³) and silicic acid (64 mmol m⁻³). South patch iron enrichment increased Chl by 9-fold to 3.8 mg m⁻³ and PP_EU 5-fold to 161 mmol C m⁻² d⁻¹ but, notably, did not alter the phytoplankton assemblage from the initial composition of ∼50% diatoms. South patch iron addition also reduced total particulate organic carbon:Chl from ∼300 to 100; enhanced the presence of novel non-photosynthetic, but fluorescent, compounds; and counteracted a decrease in photosynthetic performance as photoperiod decreased. These experiments show unambiguously that in the contemporary, high nitrate Southern Ocean increasing iron supply increases primary productivity, confirming the initial premise of the Martin Iron Hypothesis. However, despite a 5-fold increase in PP_EU under iron-replete conditions in late summer, the effect of iron on annual productivity in the Southern Ocean poleward of the SBACC is limited by seasonal ice coverage and the dark of polar winter.  相似文献   

Dry atmospheric deposition and diazotrophy as sources of new nitrogen to northwestern Mediterranean oligotrophic surface waters     

《Deep Sea Research Part I: Oceanographic Research Papers》2007,54(11):1859-1870

Atmospheric dry deposition of nitrogen (N) and dinitrogen (N₂) fixation rates were assessed in 2004 at the time-series DYFAMED station (northwestern Mediterranean, 43°25′N, 7°52′E). The atmospheric input was monitored over the whole year. Dinitrogen fixation was measured during different seasonal trophic states (from mesotrophy to oligotrophy) sampled during nine cruises. The bioavailability of atmospherically deposited nutrients was estimated by apparent solubility after 96 h. The solubility of dry atmospheric N deposition was highly variable (from ∼18% to more than 96% of total N). New N supplied to surface waters by the dry atmospheric deposition was mainly nitrate (NO₃⁻) (∼57% of total N, compared to ∼6% released as ammonium (NH₄⁺)). The mean bioavailable dry flux of total N was estimated to be ∼112 μmol m⁻² d⁻¹ over the whole year. The NO₃⁻ contribution (70 μmol NO₃⁻ m⁻² d⁻¹) was much higher than the NH₄⁺ contribution (1.2 μmol NH₄⁺ m⁻² d⁻¹). The N:P ratios in the bioavailable fraction of atmospheric inputs (122.5–1340) were always much higher than the Redfield N:P ratio (16). Insoluble N in atmospheric dry deposition (referred to as “organic” and believed to be strongly related to anthropogenic emissions) was ∼40 μmol m⁻² d⁻¹. N₂ fixation rates ranged from 2 to 7.5 nmol L⁻¹ d⁻¹. The highest values were found in August, during the oligotrophic period (7.5 nmol L⁻¹ at 10 m depth), and in April, during the productive period (4 nmol L⁻¹ d⁻¹ at 10 m depth). Daily integrated values of N₂ fixation ranged from 22 to 100 μmol N m⁻² d⁻¹, with a maximum of 245 μmol N m⁻² d⁻¹ in August. No relationship was found between the availability of phosphorus or iron and the observed temporal variability of N₂ fixation rates. The atmospheric dry deposition and N₂ fixation represented 0.5–6% and 1–20% of the total biological nitrogen demand, respectively. Their contribution to new production was more significant: 1–28% and 2–55% for atmospheric dry deposition and N₂ fixation, respectively. The dry atmospheric input was particularly significant in conditions of water column stratification (16–28% of new production), while N₂ fixation reached its highest values in June (46% of new production) and in August (55%).  相似文献   

Standing stocks,production, and respiration of phytoplankton and heterotrophic bacteria in the western Arctic Ocean     

《Deep Sea Research Part II: Topical Studies in Oceanography》2009,56(17):1237-1248

Standing stocks and production rates for phytoplankton and heterotrophic bacteria were examined during four expeditions in the western Arctic Ocean (Chukchi Sea and Canada Basin) in the spring and summer of 2002 and 2004. Rates of primary production (PP) and bacterial production (BP) were higher in the summer than in spring and in shelf waters than in the basin. Most surprisingly, PP was 3-fold higher in 2004 than in 2002; ice-corrected rates were 1581 and 458 mg C m⁻² d⁻¹, respectively, for the entire region. The difference between years was mainly due to low ice coverage in the summer of 2004. The spatial and temporal variation in PP led to comparable variation in BP. Although temperature explained as much variability in BP as did PP or phytoplankton biomass, there was no relationship between temperature and bacterial growth rates above about 0 °C. The average ratio of BP to PP was 0.06 and 0.79 when ice-corrected PP rates were greater than and less than 100 mg C m⁻² d⁻¹, respectively; the overall average was 0.34. Bacteria accounted for a highly variable fraction of total respiration, from 3% to over 60% with a mean of 25%. Likewise, the fraction of PP consumed by bacterial respiration, when calculated from growth efficiency (average of 6.9%) and BP estimates, varied greatly over time and space (7% to >500%). The apparent uncoupling between respiration and PP has several implications for carbon export and storage in the western Arctic Ocean.  相似文献   

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   

Seasonal and mesoscale variability of primary production in the deep winter-mixing region of the NW Mediterranean     

《Deep Sea Research Part I: Oceanographic Research Papers》2014

  相似文献   

Phytoplankton dynamics in the NE subarctic Pacific     

《Deep Sea Research Part II: Topical Studies in Oceanography》1999,46(11-12):2405-2432

Ocean Station Papa (OSP, 50°N 145°W) in the NE subarctic Pacific is characterised as high nitrate low chlorophyll (HNLC). However, little is known about the spatial extent of these HNLC waters or the phytoplankton dynamics on the basin scale. Algal biomass, production and size-structure data are presented from winter, spring and summer between 1992 and 1997 for five stations ranging from coastal to open-ocean conditions. The inshore stations (P04–P16) are characterised by the classical seasonal cycle of spring and late summer blooms (production >3 g C m⁻² d⁻¹), diatoms are not Fe-stressed, and growth rate is probably controlled by macronutrient supply. The fate of the phytoplankton is likely sedimentation by diatom-dominated spring blooms, with a pelagic recycling system predominating at other times. The offshore stations (P20/OSP) display low seasonality in biomass and production (OSP, mean winter production 0.3 g C m⁻² d⁻¹, mean spring/summer production 0.85 g C m⁻² d⁻¹), and are dominated by small algal cells. Low Fe availability prevents the occurrence of diatom blooms observed inshore. The main fate of phytoplankton is probably recycling through the microbial food web, with relatively low sedimentation compared to inshore. However, the supply of macro- and micro-nutrients to the coastal and open ocean, respectively, may vary between years. Variability in macro-nutrient supply to the coastal ocean may result in decreased winter reserve nitrate, summer nitrate limitation, subsequent floristic shifts towards small cells, and reduced primary production. Offshore, higher diatom abundances are occasionally observed, perhaps indicating episodic Fe supply. The two distinct oceanic regimes have different phytoplankton dynamics resulting in different seasonality, community structure and fate of algal carbon. These differences will strongly influence the biogeochemical signatures of the coastal and open-oceanic NE subarctic Pacific.  相似文献   

The relative contributions of unicellular and filamentous diazotrophs to N2 fixation in the South China Sea and the upstream Kuroshio     

《Deep Sea Research Part I: Oceanographic Research Papers》2014

We studied the seasonal, diel, and vertical distribution of phytoplankton N₂ fixation to understand the relative contributions of unicellular and filamentous nitrogen fixers (diazotrophs) to N₂ fixation and nitrogen recycling in the northern South China Sea (SCS) and the neighboring upstream Kuroshio. N₂-fixation rates were measured by the ¹⁵N₂ tracer technique (addition by bubble) on unicellular (<10 or 20 µm) and the filamentous diazotrophs (>10 or 20 µm, mostly Trichodesmium and Richelia) fractionated by 10- or 20-µm mesh sizes. The mean depth-integrated total (unicellular+filamentous) N₂-fixation rates in the SCS (51.7±6.2 µmol N m⁻² d⁻¹) averaged 1/3 of that in the Kuroshio (142.7±29.6 µmol N m⁻² d⁻¹), with higher rates in the winter than in other seasons in the SCS and the opposite seasonal pattern in the Kuroshio. Unicellular diazotrophs contributed 65% of the total N₂ fixation in the SCS, which were negatively correlated with surface temperature and, as for total N₂ fixation, were higher in the winter when Trichodesmium spp. were scarce. In comparison, the unicellular diazotrophs contributed 50% of total N₂ fixation in the Kuroshio, and their contributions were not significantly correlated with surface temperature. In both the SCS and the Kuroshio, the unicellular N₂ fixation was more important during the night than during the day, and in the deep euphotic layer than in the surface layer, even in the daytime. Our results show that the unicellular diazotrophs were important N₂ fixers and contributed significantly to N₂ fixation in the tropical marginal seas, more so in the SCS than the Kuroshio.  相似文献   

Export fluxes of particulate organic carbon in the Chukchi Sea: A comparative study using 234Th/238U disequilibria and drifting sediment traps     

《Marine Chemistry》2007,103(1-2):185-196

Large-volume sampling of ²³⁴Th and drifting sediment trap deployments were conducted as part of the 2004 Western Arctic Shelf–Basin Interactions (SBI) spring (May 15–June 23) and summer (July 17–August 26) process cruises in the Chukchi Sea. Measurements of ²³⁴Th and particulate organic carbon (POC) export fluxes were obtained at five stations during the spring cruise and four stations during the summer cruise along Barrow Canyon (BC) and along a parallel shelf-to-basin transect from East Hanna Shoal (EHS) to the Canada Basin. ²³⁴Th and POC fluxes obtained with in situ pumps and drifting sediment traps agreed to within a factor of 2 for 70% of the measurements. POC export fluxes measured with in situ pumps at 50 m along BC were similar in spring and summer (average = 14.0 ± 8.0 mmol C m^− 2 day^− 1 and 16.5 ± 6.5 mmol C m^− 2 day^− 1, respectively), but increased from spring to summer at the EHS transect (average = 1.9 ± 1.1 mmol C m^− 2 day^− 1 and 19.5 ± 3.3 mmol C m^− 2 day^− 1, respectively). POC fluxes measured with sediment traps at 50 m along BC were also similar in both seasons (31.3 ± 9.3 mmol C m^− 2 day^− 1 and 29.1 ± 14.2 mmol C m^− 2 day^− 1, respectively), but were approximately twice as high as POC fluxes measured with in situ pumps. Sediment trap POC fluxes measured along the EHS transect also increased from spring to summer (3.0 ± 1.9 mmol C m^− 2 day^− 1 and 13.0 ± 6.4 mmol C m^− 2 day^− 1, respectively), and these fluxes were similar to the POC fluxes obtained with in situ pumps. Discrepancies in POC export fluxes measured using in situ pumps and sediment traps may be reasonably explained by differences in the estimated POC/²³⁴Th ratios that arise from differences between the techniques, such as time-scale of measurement and size and composition of the collected particles. Despite this variability, in situ pump and sediment trap-derived POC fluxes were only significantly different at a highly productive station in BC during the spring.  相似文献   

Diapycnal nutrient fluxes on the northern boundary of Cape Ghir upwelling region     

《Deep Sea Research Part I: Oceanographic Research Papers》2014

In this study we estimate diffusive nutrient fluxes in the northern region of Cape Ghir upwelling system (Northwest Africa) during autumn 2010. The contribution of two co-existing vertical mixing processes (turbulence and salt fingers) is estimated through micro- and fine-structure scale observations. The boundary between coastal upwelling and open ocean waters becomes apparent when nitrate is used as a tracer. Below the mixed layer (56.15±15.56 m), the water column is favorable to the occurrence of a salt finger regime. Vertical eddy diffusivity for salt (K_s) at the reference layer (57.86±8.51 m, CI 95%) was 3×10⁻⁵ (±1.89×10⁻⁹, CI 95%) m² s⁻¹. Average diapycnal fluxes indicate that there was a deficit in phosphate supply to the surface layer (6.61×10⁻⁴ mmol m⁻² d⁻¹), while these fluxes were 0.09 and 0.03 mmol m⁻² d⁻¹ for nitrate and silicate, respectively. There is a need to conduct more studies to obtain accurate estimations of vertical eddy diffusivity and nutrient supply in complex transitional zones, like Cape Ghir. This will provide us with information about salt and nutrients exchange in onshore–offshore zones.  相似文献   

Microzooplankton grazing impact in the Western Arctic Ocean     

《Deep Sea Research Part II: Topical Studies in Oceanography》2009,56(17):1264-1273

Microzooplankton grazing impact on phytoplankton was assessed using the Landry–Hassett dilution technique in the Western Arctic Ocean during spring and summer 2002 and 2004. Forty experiments were completed in a region encompassing productive shelf regions of the Chukchi Sea, mesotrophic slope regions of the Beaufort Sea off the North Slope of Alaska, and oligotrophic deep-water sites in the Canada Basin. A variety of conditions were encountered, from heavy sea-ice cover during both spring cruises, moderate sea-ice cover during summer of 2002, and light to no sea ice during summer of 2004, with a concomitant range of trophic conditions, from low chlorophyll-a (Chl-a; <0.5 μg L⁻¹) during heavy ice cover in spring and in the open basin, to late spring and summer shelf and slope open-water diatom blooms with Chl-a >5 μg L⁻¹. The microzooplankton community was dominated by large naked ciliates and heterotrophic gymnodinoid dinoflagellates. Significant, but low, rates of microzooplankton herbivory were found in half of the experiments. The maximum grazing rate was 0.16 d⁻¹ and average grazing rate, including experiments with no significant grazing, was 0.04±0.06 d⁻¹. Phytoplankton intrinsic growth rates varied from the highest values of about 0.4 d⁻¹ to the lowest values of zero to slightly negative growth, on average 0.16±0.15 d⁻¹. Light limitation in spring and post-bloom senescence during summer were likely explanations of observed low phytoplankton growth rates. Microzooplankton grazing consumed 0–120% (average 22±26%) of phytoplankton daily growth. Grazing and growth rates found in this study were low compared to rates reported in another Arctic system, the Barents Sea, and in major geographic regions of the world ocean.  相似文献   

Winter and spring phytoplankton composition and production in a shallow eutrophic Baltic lagoon     

《Estuarine, Coastal and Shelf Science》2005,62(1-2):169-181

Taxonomic composition and productivity of winter and spring phytoplankton in a eutrophic estuary have been investigated in order to elucidate the carbon flux under conditions of limitation by physical factors – light and temperature. In spite of the important differences in nutrients, solar radiation and water temperature between winter and spring season, mean concentrations of particulate organic carbon were equal to 13.2 and 13.0 mgC l⁻¹, respectively. Chlorophyll a averaged at 79 μgChl l⁻¹ in winter, that is 69% of spring. Although community respiration accounted for only 6–26% of light saturated photosynthesis, integrated net primary production of the 1.2 m deep water column was negative until April. High attenuation of the water body (K_o = 2.9 m⁻¹) lead to a negative carbon balance (net heterotrophy) below 35 cm for all sampling dates. Thus, the high winter POC and phytoplankton values can only originate from summer or autumn primary production. This assumption was supported by a carbon loss rate of just 3% of total organic carbon per day for the whole water column. The composition of phytoplankton was very constant through both seasons: 39% Chlorophyceae, 33% Cyanobacteria and 25% Bacillariophyceae. As expected, phytoplankton was low light acclimated, having high α values (slope of light limited photosynthesis), but moderate maximum photosynthesis rates at saturating irradiances, which were heavily affected by temperature. Calculation of net carbon flux yet showed net heterotrophy of the Bodden waters in winter and early spring were caused by external physical limitation (low surface irradiance and low temperature) in combination with a high light attenuation of the water body.  相似文献   

Plankton net community production and dark respiration in the Arabian Sea during September 1994     

《Deep Sea Research Part II: Topical Studies in Oceanography》1999,46(3-4):745-765

Plankton community net and gross production and dark respiration were determined from in vitro changes in dissolved inorganic carbon and dissolved oxygen during September 1994 along a southeast offshore transect in the Arabian Sea. Surface rates of gross production decreased from 17±0.7 mmol C m^-3 d^-1 at a coastal upwelling station to 3±0.8 mmol C m^-3 d^-1 at the most offshore station. The euphotic zone at the time of sampling was predominantly heterotrophic, with integrated net community production values ranging from 15±7 mmol C m^-2 d^-1 inshore to −253±32 mmol C m^-2 d^-1 offshore. Calculations of the respiration attributable to the major plankton groups could account for 61–87% of the dark community respiration measured at the inshore stations, but only 15–26% of the community respiration determined offshore. Comparison of the fluxes of dissolved inorganic carbon and oxygen revealed a tendency for higher respiratory quotients than those calculated for organic metabolism prevailing at the offshore stations.  相似文献   

Impacts of the wintertime mesozooplankton community to downward carbon flux in the subarctic and subtropical Pacific Oceans     

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

We compared wintertime depth distributions of the mesozooplankton community and dominant copepods between the subtropical (S1) and subarctic (K2) Pacific Oceans to evaluate the relative importance of actively transported carbon by vertical migrants to sinking particulate organic carbon flux. Primary production was higher and the ratio of sinking particulate organic carbon flux to primary production was lower at S1 compared with those at K2. The mesozooplankton community was lower in abundance and biomass at S1 compared to K2. Copepods were the dominant group among both mesozooplankton abundance and biomass throughout the water column down to 1000 m at both sites. The depth distribution showed that diel vertical migration was obvious for the mesozooplankton abundance and biomass at S1 but was not apparent for the abundance at K2, because the dominant component was diurnally migrating species at S1 and overwintering species residing at mesopelagic depths at K2. The major components of diel migrants were copepods and euphausiids at S1 and only euphausiids at K2. Respiratory flux by the diurnally migrating mesozooplankton was estimated to be 2 mgC m⁻² day⁻¹ at S1 and 7 mgC m⁻² day⁻¹ at K2. The respiratory flux was equivalent to 131% of sedimentary fecal pellet flux at S1 and 136% of that at K2. Because pathways of downward carbon flux are facilitated by the mesozooplankton community, the actively transported carbon (respiration of dissolved inorganic carbon, excretion of dissolved organic carbon and egestion of fecal pellets at depth) might be larger during winter than the flux of sinking fecal pellets.  相似文献   

Fate of biogenic carbon in the upper 200 m of the central Greenland Sea     

《Deep Sea Research Part II: Topical Studies in Oceanography》1999,46(6-7):1497-1509

Sedimentation of particulate carbon from the upper 200–300 m in the central Greenland Sea from August 1993 to June 1995 was less than 2 g C m⁻² yr⁻¹. Daily rates of sedimentation of particulate organic carbon reached highest values of about 18 mg m⁻² d⁻¹ in fall 1994. For total particulate material, maximum rates of sedimentation of about 250 mg m⁻² d⁻¹ were recorded in spring and fall 1994. For chlorophyll equivalent, highest rates of sedimentation of about 140 μg m⁻² d⁻¹ were recorded in spring 1994. As reported in related investigations, the transient accumulation of DOC in surface waters during summer, as well as respiration and mortality of deep overwintering zooplankton stocks, appeared to dominate the fate of photosynthetically fixed organic carbon. The above processes may account for roughly 43 g C m⁻² in the upper 200 m of the central Greenland Sea. For comparison, the seasonal deficit in dissolved inorganic carbon was reported to be about 23 g C m⁻² in the upper 20 m of surface water, and estimates for new annual production were reported to be about 57 g C m⁻². In our investigation, the biological carbon pump was not unusually effective in transporting carbon out of the productive surface layer.  相似文献   

Plankton community and bacterial metabolism in Arctic sea ice leads during summer 2010     

《Deep Sea Research Part I: Oceanographic Research Papers》2014

Microbial plankton metabolism was examined during summer 2010 in sea ice-influenced waters of the Fram Strait, eastern Arctic Ocean. Rates of gross primary production and community respiration were tightly coupled over a wide range of values (33±3–143±6 and 20±3–126±6 mmol O₂ m^{−2  −1}, respectively) leading to a prevalence of positive net community production. The high variability in community respiration, similar to that of gross primary production, suggests that heterotrophic metabolism may exhibit a significant response to environmental change. Bacterial respiration was assessed at similar time scales to bacterial production measurements, by determining the in vivo INT reduction capacity without pre-filtering the community. Bacteria seem to play a major role in total community respiration, contributing between 5% and 61% of total community respiration, indicating that a high fraction of the organic carbon in Arctic planktonic food webs could flow through these microbes.  相似文献