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1.
The macrotidal bay of Marennes-Oléron is the most important French site for shellfish production (oysters and mussels); yet the primary productivity of the phytoplankton compartment in this system is not well known. In this study, photosynthetic parameters were determined using 14C incubations of bottom and surface water samples, during fall, winter and summer (2001–2002), along a north–south transect in the bay. Estimates of primary productivity showed that water column primary production is light-limited in the bay and that a BZpI0 type model can be applied. Spatial differences existed in the bay, with a more productive northern zone and less productive river area. With a water column primary production of 185 g C m−2 yr−1, Marennes-Oléron Bay lies in the mean range for phytoplankton primary production capacity among European and North American estuaries.  相似文献   

2.
Net community biological production in the euphotic zone of the ocean fuels organic matter and oxygen export from the upper ocean, which has a large influence on the atmospheric pressure of carbon dioxide and is the driving force for metabolite distributions in the sea. We determine the net annual biological oxygen production in the mixed layer of the northeast subarctic Pacific Ocean from in situ O2 and N2 measurements. Temperature, salinity, total gas pressure and O2 were measured every 3 h for 9 months in 2007 at about 3 m depth on a surface mooring at Station P (50°N, 145°W). The concentration of nitrogen gas, N2, determined from separate total gas pressure and pO2 measurements, was used as an inert tracer of the physical processes that induce gas departure from thermodynamic equilibrium with the atmosphere. We use a simple model of the ocean’s mixed layer along with the nitrogen concentration to constrain the importance of bubbles, gas exchange and horizontal advection, which are then used in the oxygen mass balance to derive net biological oxygen production. The mixed-layer oxygen mass balance is dominated by exchange with the atmosphere, and we determine a mean summertime oxygen production of 24 mmol O2 m?2 d?1. The annual pattern in the difference between the supersaturation of oxygen and nitrogen in the surface waters reveals very little net oxygen production during the winter at this location. The calculated annual net community production (NCP) of carbon from this new method, 2.5 mol m?2 yr?1, agrees to within its error of about×40% with previous determinations at this location from oxygen mass balance, NO3? draw down and 234Th measurements. This value is either indistinguishable from or lower than annual NCP measurements in the subtropical North Pacific, indicating that there is no experimental evidence for differences in annual NCP between the subarctic and subtropical North Pacific Ocean.  相似文献   

3.
Measurement of dissolved oxygen using optodes in a FerryBox system   总被引：2，自引：0，他引：2  
Optode sensors can provide detailed information on concentrations of dissolved oxygen, which in turn may be used to quantify variations in net primary productivity. Throughout 2005 and 2006 the performance of commercially available oxygen optodes was examined, one in each year. The optode was part of an autonomous measurement system (FerryBox) on a ferry operating between Portsmouth (UK) and Bilbao (Spain). On crossings during which water samples were collected manually, the optode outputs were compared to measurements of dissolved oxygen made by Winkler titrations. The optodes maintained good stability with no evidence of instrumental drift during the course of a year. Over the observed concentration range (230–330 mM m−3) the optode data were approximately 2% low in both years. By fitting the optode data to the Winkler data the median difference between the optode and Winkler measurements is reduced to less than 1 mM m−3 (0.3%) in both years. The most appropriate calibration factor for 2005 was corrected O2 = Optode O2 × 1.018 and for 2006 the corresponding equation is corrected O2 = Optode O2 × 0.884 + 36.8. The standard deviation (95%) of the difference between the individual Winkler measurements was 5 mM m−3 and 3 mM m−3 in 2005 and 2006 respectively.Calculation of the oxygen saturation anomaly is required for calculation of the air sea exchange of oxygen and net biological production. This calculation requires the use of both salinity and temperature data. Salinity is measured to better than 0.1 so the corresponding error in anomaly is less than 0.2 mM m−3. Distortion of the temperature data is present due to warming of the water pumped to the optode. In winter this warming at the optode may be as great as 0.4 °C. The difference in the pumped water temperature can be corrected for by reference to other measurements of sea surface temperature reducing the error to less than 1 mM m−3.  相似文献   

4.
Laboratory and in situ experiments were performed to assess the use of bromide as a tracer forin situ studies of benthic solute exchange. Bromide was used in the benthic chamber lander ‘ Elinor ’ for flux measurements in coastal sediments of the German Bight, Kiel Bight and Skagerrak (28–700 m water depth). Tracer and total oxygen uptake were monitored simultaneously in the same chamber incubation. Concurrently, in situ oxygen micro-profiles were recorded at the same locations by the profiling lander ‘ Profilur ’. Deployment in an anoxic silt (Kiel Bight) confirmed that in the absence of bioturbation and advection, tracer transport into the sediment was driven solely by molecular diffusion. This flux could be well described by a simple box model accounting for molecular diffusion only. In oxic sediments (German Bight and Skagerrak) enhanced exchange of bromide tracer due to bioirrigation parallelled enhanced oxygen uptake equivalent to a 4-fold molecular diffusive flux. Our experiments showed that incubations can be short. Depending on irrigation activity of the fauna, however, incubation length should exceed 3 h in order to provide a useful data base for flux calculations. The method demonstrating caveats is discussed and indicate possible improvements. The results show how the bromide tracer addition can be used as a tool for determining solute fluxes exceeding diffusive flux in benthic chamber incubations.  相似文献   

5.
Studying the diversity‐ecosystem function relationship in the deep sea is of primary importance in the face of biodiversity loss and for our understanding of how the deep sea functions. Results from the first study of diversity‐ecosystem function relationships in the deep sea (Danovaro et al. 2008; Current Biology, 18, 1–8) are unexpected and show an exponential relationship between deep‐sea nematode diversity and ecosystem function and efficiency, although this relationship appears largely restricted to relatively low diversities [ES(51) <25]. Here, we investigate the relationship between nematode diversity and several independent measures/proxies of ecosystem function (sediment community oxygen consumption, bacterial biomass, bacterial extracellular enzyme activity) and efficiency (ratio of bacterial/nematode carbon to organic C content of the sediment) on the New Zealand continental slope. Nematode diversity at our study sites was relatively high [ES(51) = 30–42], and there was no relationship between species/functional diversity and ecosystem function/efficiency after accounting for the effects of water depth and food availability. Our results are consistent with a breakdown of the exponential diversity‐function relationship at high levels of diversity, which may be due to increased competition or greater functional redundancy. Future studies need to take into account as many environmental factors and as wide a range of diversities as possible to provide further insights into the diversity‐ecosystem function relationship in the largest ecosystem on Earth.  相似文献   

6.
A CEE (2.5 m by 16 m) has been used to study the budget of organic production by measuring the changes in POC/N, oxygen and 14CO, uptake through three-week period. 14C primary production measurements were conducted with 4-hours and 24-hours incubation periods, and with size fractionation. Different types and sizes of bottle effects were examined. Results showed that the oxygen method production was highest, followed by the 14CO2 uptake method, and POC gain showed the lowest. The value of PQ should be more than 1.7. The ratio of 4-hour incubation to 24-hour incubation was 2.42±0.22, indicating that net daily production is equal to 9.7±0.9 h of illuminated growth. Different types and sizes of bottles had little effect on primary production.  相似文献   

7.
余为  陈新军  易倩 《海洋学报》2016,38(2):64-72
海洋初级生产力在海洋生态中扮演重要角色,其变化影响了海洋渔业的潜在产量。本文根据2004-2013年中国鱿钓组提供的西北太平洋柔鱼(Ommastrephes bartramii)捕捞数据和海洋遥感净初级生产力数据,研究了柔鱼冬春生西部群体资源量变动与净初级生产力的关系。结果发现,柔鱼渔场范围内净初级生产力在经度方向上呈明显的季节性变化,冬春季低,夏秋季高。捕捞月份7-11月对应的适宜净初级生产力范围分别为500~700 mg/(m2·d)(以碳计),500~800 mg/(m2·d),500~1000 mg/(m2·d),500~800 mg/(m2·d)和300~500 mg/(m2·d),最适净初级生产力分别为700 mg/(m2·d),600 mg/(m2·d),700 mg/(m2·d),600 mg/(m2·d)和400 mg/(m2·d)。7-11各月最适净初级生产力平均纬度与捕捞努力量纬度重心呈显著正相关关系(P<0.05),说明了捕捞努力量位置在渔场中不是随机分布,可能受最适净初级生产力的纬度分布的影响。柔鱼年间资源丰度与各年3月份净初级生产力以及7-11月份平均净初级生产力大小显著正相关(P<0.05)。推测每年柔鱼资源量大小可能是由3月份产卵场海域和7-11月捕捞月份渔场净初级生产力水平交互作用的结果。研究表明,异常环境条件(厄尔尼诺和拉尼娜事件)对柔鱼产卵场和渔场的净初级生产力具有显著影响,但调控机制不同。  相似文献   

8.
Biomass and primary productivity of picophytoplankton (PP; phytoplankton <3 μm) and larger phytoplankton (>3 μm) were determined during an annual cycle along the salinity gradient in North Carolina’s Neuse River Estuary (NRE), a eutrophic, microtidal estuary. The PP were a major component of total phytoplankton biomass and productivity, contributing ∼35–44% of the total chlorophyll a (Chl a) and 42–55% of the total primary productivity. Chl a and productivity of PP decreased from the upper to lower estuary, although the PP contribution relative to larger phytoplankton remained nearly constant. Significant PP growth occurred in the spring, but PP productivity and biomass were maximal in summer. PP productivity and biomass were positively correlated with temperature and dissolved inorganic phosphorus concentrations, which were maximal in summer due to release from sediments. Biomass and productivity of PP and >3 μm phytoplankton were also positively correlated, suggesting that growth conditions favoring the onset of blooms of larger phytoplankton species will similarly affect PP. High PP productivity and biomass in the NRE support the notion that PP play an important role in the production and eutrophication potentials of this estuary. High PP productivity and biomass have been noted in several other temperate estuaries, all sharing a common feature with the NRE—long residence time. These findings challenge the assumption that PP relative importance should be minimal in eutrophic systems.  相似文献   

9.
Wet atmospheric deposition of dissolved N, P and Si species is studied in well-mixed coastal ecosystem to evaluate its potential to stimulate photosynthetic activities in nutrient-depleted conditions. Our results show that, during spring, seawater is greatly depleted in major nutrients: Dissolved Inorganic Nitrogen (DIN), Dissolved Inorganic Phosphorus (DIP) and Silicic acid (Si), in parallel with an increase of phytoplanktonic biomass. In spring (March–May) and summer (June–September), wet atmospheric deposition is the predominant source (>60%, relative to riverine contribution) for nitrates and ammonium inputs to this N-limited coastal ecosystem. During winter (October–February), riverine inputs of DIN predominate (>80%) and are annually the most important source of DIP (>90%). This situation allows us to calculate the possibility for a significant contribution to primary production in May 2003, from atmospheric deposition (total input for DIN ≈300 kg km−2 month−1). Based on usual Redfield ratios and assuming that all of the atmospheric-derived N (AD-N) in rainwater is bioavailable for phytoplankton growth, we can estimate new production due to AD-N of 950 mg C m−2 month−1, during this period of depletion in the water column. During the same episode (May 2003), photosynthetic activity rate, considered as gross primary production, was estimated to approximately 30 300 mg C m−2 month−1. Calculation indicates that new photosynthetic activity due to wet atmospheric inputs of nitrogen could be up to 3%.  相似文献   

10.
Bacterial productivity (BP) and respiration (BR) were examined in relation to primary productivity (PP) for the first time in a shallow tropical ecosystem (Cochin Estuary), India. The degree of dependence of BP (6.3–199.7 μg C L−1 d−1) and BR (6.6–430.4 μg C L−1 d−1) on PP (2.1–608.0 μg C L−1 d−1) was found to be extremely weak. The BP/PP (0.05–8.5) and PP/BR (0.02–7.9) ratios widely varied in the estuary depending on the season and location. There was a seasonal shift in net pelagic production from autotrophy to heterotrophy due to terrestrial organic matter input through rivers which enhanced the bacterial heterotrophic activity and very high pCO2 (106–6001 μatm) levels. The heterotrophic zones were characterized by low PP but high bacterial production and respiration leading to oxygen undersaturation and exceptionally high pCO2. We propose that the CO2 supersaturation caused by increased bacterial respiration (in excess of PP) was a result of bacterial degradation of allochthonous organic matter. This indicates that sources other than planktonic compartment need to be explored to understand the C-cycling in this estuary. These results are of particular relevance to tropical ecosystems in general, where the bulk of world's river discharges occur.  相似文献   

11.
High temporal resolution measurements of physical and bio-optical variables were made in the upper ocean using a mooring located at 0°, 140°W from 9 February 1992 to 15 March 1993 as part of the equatorial Pacific Ocean (EgPac) study. Chlorophyll and primary productivity time-series records were generated using the mooring data. Primary productivity varied by about 50% around the mean on time scales of weeks and by over a factor of four within our observational period. The mooring observations encompassed both El Niho and cool conditions. Kelvin waves were evident during the El Nifio phase, and tropical instability waves (TIWs) were dominant during the cool phase. The two extreme conditions also were observed concurrently with complementary ship-based measurements. In addition, bio-optical drifters provided simultaneous spatial data concerning net phytoplankton growth rates during passage of a TIW. The collective data sets have been used to examine the causes of the observed variability in phytoplankton biomass and productivity. Our joint results and analyses appear to support the hypothesis that the vertical transport of iron into the upper layer and primary production rates are modulated by variability of the depth of the Equatorial Undercurrent and by equatorial longwaves. In particular, our results are consonant with the suggestion of Barber et al. (1996) that passage of a TIW may be considered to be a natural analog of a small iron enrichment experiment. Predicting primary productivity and, thus, carbon flux in the equatorial Pacific requires continuous, long-term observations of a few physical, biological, and optical properties that can be used to parameterize the biological variability.  相似文献   

12.
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   

13.
A study was carried out to assess primary production and associated export flux in the coastal waters of the western Antarctic Peninsula at an oceanographic time-series site. New, i.e., exportable, primary production in the upper water-column was estimated in two ways; by nutrient deficit measurements, and by primary production rate measurements using separate 14C-labelled radioisotope and 15N-labelled stable isotope uptake incubations. The resulting average annual exportable primary production estimates at the time-series site from nutrient deficit and primary production rates were 13 and 16 mol C m−2, respectively. Regenerated primary production was measured using 15N-labelled ammonium and urea uptake, and was low throughout the sampling period.The exportable primary production measurements were compared with sediment trap flux measurements from 2 locations; the time-series site and at a site 40 km away in deeper water. Results showed ∼1% of the upper mixed layer exportable primary production was exported to traps at 200 m depth at the time-series site (total water column depth 520 m). The maximum particle flux rate to sediment traps at the deeper offshore site (total water column depth 820 m) was lower than the flux at the coastal time-series site. Flux of particulate organic carbon was similar throughout the spring–summer high flux period for both sites. Remineralisation of particulate organic matter predominantly occurred in the upper water-column (<200 m depth), with minimal remineralisation below 200 m, at both sites. This highly productive region on the Western Antarctic Peninsula is therefore best characterised as ‘high recycling, low export’.  相似文献   

14.
Iron (Fe) availability limits phytoplankton biomass and production in large regions of the Southern Ocean and influences community composition and size structure, which may affect C export and other system-level functions. To improve our understanding of Fe partitioning within communities and the response of different components to fertilization, we assessed the cellular Fe contents of individual diatoms, autotrophic flagellates, and heterotrophic flagellates during the recent Southern Ocean Fe Experiment using synchrotron-based X-ray fluorescence (SXRF). Dual 55Fe/14C radioisotope incubations were also conducted to estimate Fe:C ratios in size-fractionated plankton. Cellular Fe quotas determined by the two techniques were in close agreement when low amounts of 55Fe (0.2 nM) were added, but 55Fe additions of 2 nM resulted in 2–3-fold higher quotas. SXRF assessments of cellular Fe quotas (normalized to C) were generally in good agreement with prior bulk analyses of natural assemblages, but revealed compositional differences among protistan taxa not previously detected. Mean Fe:C ratios for diatoms, autotrophic flagellates, and heterotrophic flagellates from unfertilized waters were 6.0, 8.7, and 14.1 μmol mol C−1, respectively. Smaller cells had higher Fe:C ratios than larger cells. Fertilization enhanced Fe quotas in all cell types, with mean Fe:C ratios increasing approximately 4-fold (from about 10 to about 40 μmol mol C−1) after two Fe additions. This study provides some of the first measurements of Fe quotas in phytoplankton cells from natural communities and the first measurements of Fe quotas in natural protozoa.  相似文献   

15.
We deployed a profiling buoy system incorporating a fast repetition rate fluorometer in the western subarctic Pacific and carried out time-series observations of phytoplankton productivity from 9 June to 15 July 2006. The chlorophyll a (Chl a) biomass integrated over the euphotic layer was as high as 45–50 mg Chl a m−2 in the middle of June and remained in the 30–40 mg Chl a m−2 range during the rest of observation period; day-to-day variation in Chl a biomass was relatively small. The daily net primary productivity integrated over the euphotic layer ranged from 144 to 919 mg C m−2 day−1 and varied greatly, depending more on insolation rather than Chl a biomass. In addition, we found that part of primary production was exported to a 150-m depth within 2 days, indicating that the variations in primary productivity quickly influenced the organic carbon flux from the upper ocean. Our results suggest that the short-term variability in primary productivity is one of the key factors controlling the carbon cycle in the surface ocean in the western subarctic Pacific.  相似文献   

16.
Mesozooplankton and 63–200 μm net-collected microzooplankton grazing on phytoplankton and protozoans was evaluated by 24-h incubations on a latitudinal transect in the Atlantic Ocean, from 35°N to 38°S (AMT-15; September–October 2004). The sampling area comprised contrasting ecosystems, including upwelling zones and oligotrophic subtropical gyres. Grazing impacts of mesozooplankton and 63–200 μm microzooplankton on total chlorophyll a (Chl a), >5 μm Chl a, ciliates, and dinoflagellates were low for both zooplankton size fractions, always removing<1.5% of the standing stocks of these groups. Grazing had a slightly greater impact upon primary production (up to 10% of primary production consumed daily), although on most occasions grazing removed<1% of primary production per day. To account for the reduction of micrograzers by predators in the experimental bottles and the consequent reduction of grazing pressure, the data were corrected with knowledge on the decrease of microzooplankton during incubations and global estimates of microzooplankton grazing. The corrected grazing rates for mesozooplankton ranged from 4% to 28% of the primary production consumed daily, and from 1% to 2% of the standing stock of Chl a removed every day. The 63–200 μm microzooplankton corrected grazing impact was always<5% of the primary production and standing stock consumed per day. The corrected grazing activity of 63–200 μm microzooplankton and mesozooplankton rendered daily rations ranging from 3% to 38% of the body carbon consumed daily, not sufficient for basal metabolism in most of the areas studied. Finally, the data on mesozooplankton grazing on primary production confirm the recent hypothesis of a decline of the relative importance of mesozooplankton grazing on primary producers with increasing primary production [Calbet, A., 2001. Mesozooplankton grazing effect on primary production: a global comparative analysis in marine ecosystems. Limnology and Oceanography 46, 1824–1830].  相似文献   

17.
Conventional laboratory studies of deep-sea fish metabolism are not possible as these fish are typically killed during recovery to the surface. As these species are important members of deep-sea communities, the lack of these data represents a significant limitation to our understanding of the functioning of this ecosystem. An autonomous fish respirometer vehicle was developed in order to measure the oxygen consumption of deep-sea fish in situ. This new lander allows measurements to be made without handling or stressing the animals and without the logistical problems and great cost of submersible operations. The design, operation, and measurement methodology are described and preliminary data for Coryphaenoides armatus at 4000 m are presented. These Atlantic data appear to confirm the low metabolic rate measured in this species when compared to other gadid species.  相似文献   

18.
To determine the quantitative relationship between phytoplankton production and zooplankton grazing pressure in Atsumi Bay, a eutrophic and partially-mixed estuary, a series of investigations, including measurements of hydrographic conditions, dissolved oxygen, dissolved total nitrogen, particulate organic nitrogen, and phyto- and zooplankton biomass were conducted 13 times at intervals of 2–7 days in June and July 1984. Continuous measurements of water flow and salinity were also carried out to examine transverse flow and horizontal diffusivity. The supply of freshwater and nitrogen was estimated from given data. The changes of hydrographic condition, net photosynthetic rate and community primary production were calculated by a two-layered box model analysis. The grazing rate on phytoplankton obtained as the difference between net photosynthetic rate and community primary production was compared to the one estimated from zooplankton biomass and sardine,Sardinops melanosticta, biomass. The agreement between the data was remarkable in the upper layer, showing the grazing pressure on phytoplankton followed phytoplankton production, suggesting that a large part of produced phytoplankton was immediately grazed by zooplankton. Consequently, the community primary production was depressed to a fairly lower level. An important role of nutrient supply and water circulation, to limit phytoplankton production, was also confirmed. Dynamic response observed between the calculated grazing pressure and the biomass of phytoplankton and protozoa was also analyzed.  相似文献   

19.
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   

20.
Production of dissolved organic matter (DOM) by heterotrophic microbial communities isolated from Loch Creran (Scotland) was studied in time course incubations in which cells were re-suspended in artificial seawater amended with variable proportions of glucose, ammonium and phosphate. The incubation experiments demonstrated that microheterotrophs released part of the substrate as new DOM, with a production efficiency of 11 ± 1% for DOC, 18 ± 2% for DON and 17 ± 2% for DOP. Estimating the impact of this production in Loch Creran, showed that from 3 ± 1% (DOC) to 72 ± 16% (DOP) of DOM could originate from the heterotrophic microbial community. The produced DOM (PDOM) was both bioavailable (BDOM) and refractory (RDOM). Bioavailability as assessed by the difference between the maximum and the end DOM concentration, was generally higher than found in natural systems, with DOP (73 ± 15%, average ± SD) more bioavailable than DON (70 ± 15%), and DON than DOC (34 ± 13%).The stoichiometry of PDOM was linked to both nutrient uptake and BDOM ratios. Absorption and fluorescence of DOM increased significantly during the incubation time, indicating that microheterotrophs were also a source of coloured DOM (CDOM) and that they produce both bioavailable protein-like and refractory humic-like fluorophores.  相似文献   

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