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1.
The aim of this study was to investigate whether coral photosynthetic efficiencies and recovery processes are affected by CO2‐driven ocean acidification in symbiont photosynthesis and coral calcification. We investigated the effects of five CO2 partial pressure (pCO2) levels in adjusted seawater ranging from 300 μatm (pre‐industrial) to 800 μatm (near‐future) and strong and weak light intensity on maximum photosynthetic efficiency and calcification of a branching coral, Stylophora pistillata, as this species has often been used in rearing experiments to investigate the effects of acidified seawater on calcification and photosynthetic algae of corals. We found that, the photosynthetic efficiencies and recovery patterns under different light conditions did not differ among pCO2 treatments. Furthermore, calcification of S. pistillata was not affected by acidified seawater under weak or strong light conditions. Our results indicate that the photosynthetic efficiency and calcification of S. pistillata are insensitive to changes in ocean acidity.  相似文献   

2.
In September 1993 (M26) and June/July 1996 (M36), a total of 239 surface samples (7 m depth) were collected on two transects across the open Atlantic Ocean (224 samples) and northwest European shelf edge area. We present an overview of the horizontal variability of dissolved Cd, Co, Zn, and Pb in between the northwest and northeast Atlantic Ocean in relation to salinity and the nutrients. Our data show a preferential incorporation of Cd relative to P in the particulate material of the surface ocean when related to previously published parallel measurements on suspended particulate matter from the same cruise. There is a good agreement with results recently estimated from a model by Elderfield and Rickaby (Nature 405 (2000) 305), who predict for the North Atlantic Ocean a best fit for αCd/P=[Cd/P]POM/[Cd/P]SW of 2.5, whereas the approach of our transect shows a αCd/P value of 2.6. The Co concentrations of our transects varied from <5 to 131 pmol kg−1, with the lowest values in the subtropical gyre. There were pronounced elevations in the low-salinity ranges of the northwest Atlantic and towards the European shelf. The Co data are decoupled from the Mn distribution and support the hypothesis of marginal inputs as the dominant source. Zinc varied from a minimum of <0.07 nmol kg−1 to a maximum of 1.2 and 4.8 nmol kg−1 in regions influenced by Labrador shelf or European coastal waters, respectively. In subtropical and northeast Atlantic waters, the average Zn concentration was 0.16 nmol kg−1. Zinc concentrations at nearly three quarters of the stations between 40°N and 60°N were <0.1 nmol kg−1. This suggests that biological factors control Zn concentrations in large areas of the North Atlantic surface waters. The Pb data indicated that significant differences in concentration between the northwest and northeast Atlantic surface waters presently (1996) do not exist for this metal. The transects in 1993 and 1996 exhibited Pb concentrations in the northeast Atlantic surface waters of 30 to 40 pmol kg−1, about a fifth to a quarter of the concentrations observed in 1981. This decline is supported by our particle flux measurements in deep waters of the same region.  相似文献   

3.
The ocean is an important sink for carbon and heat, yet high-resolution measurements of biogeochemical properties relevant to global climate change are being made only sporadically in the ocean at present. There is a growing need for automated, real-time, long-term measurements of CO2 in the ocean using a network of sensors, strategically placed on ships, moorings, free-drifting buoys and autonomous remotely operated vehicles. The ground-truthing of new sensor technologies is a vital component of present and future efforts to monitor changes in the ocean carbon cycle and air–sea exchange of CO2.A comparison of a moored Carbon Interface Ocean Atmosphere (CARIOCA) buoy and shipboard fugacity of CO2 (fCO2) measurements was conducted in the western North Atlantic during two extended periods (>1 month) in 1997. The CARIOCA buoy was deployed on the Bermuda Testbed Mooring (BTM), which is located 5 km north of the site of the US Joint Global Ocean Flux Study (JGOFS) Bermuda Atlantic Time-series Study (BATS). The high frequency of sampling revealed that temperature and fCO2 responded to physical forcing by the atmosphere on timescales from diurnal to 4–8 days. Concurrent with the deployments of the CARIOCA buoy, frequent measurements of surface fCO2 were made from the R/V Weatherbird II during opportunistic visits to the BTM and BATS sites, providing a direct calibration of the CARIOCA buoy fCO2 data. Although, the in situ ground-truthing of the CARIOCA buoy was complicated by diurnal processes, sub-mesoscale and fine-scale variability, the CARIOCA buoy fCO2 data was accurate within 3±6 μatm of shipboard fCO2 data for periods up to 50 days. Longer-term assessments were not possible due to the CARIOCA buoy breaking free of the BTM and drifting into waters with different fCO2-temperature properties. Strategies are put forward for future calibration of other in situ sensors.  相似文献   

4.
Factors controlling the CO2 system parameters, including the partial pressure of CO2 (PCO2) in coral reef waters, were investigated in three mid-oceanic reefs of the Indo-Pacific region. Surface water PCO2 in the lagoons of Majuro Atoll and Palau barrier reef in the Pacific were 25 µatm and 48 µatm higher than those of the offshore waters, respectively, while South Male Atoll lagoon of the Maldives in the Indian Ocean exhibited relatively small difference in PCO2 compared to the offshore water. Observations from Majuro Atoll and Palau barrier reef are consistent with the view that calcium carbonate production predominates in coral reefs. On the other hand, results from South Male Atoll can be attributed to the thorough flushing of the lagoon, which is connected to the open ocean by numerous deep channels. The offshore-lagoon PCO2 difference depends on system-level net organic-to-inorganic carbon production ratio while reef topography, especially residence time of the lagoon, has a secondary effect on the magnitude of the offshore-lagoon difference. A potential for releasing CO2 might be more evident in an enclosed atoll where the reef water has a longer residence time. Oceanic atoll and barrier reef lagoons, which are in the terminal stage of evolutionary history of oceanic volcanic islands, have the potential to release CO2 to the atmosphere.  相似文献   

5.
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   

6.
This paper evaluates the simultaneous measurement of dissolved gases (CO2 and O2/Ar ratios) by membrane inlet mass spectrometry (MIMS) along the 180° meridian in the Southern Ocean. The calibration of pCO2 measurements by MIMS is reported for the first time using two independent methods of temperature correction. Multiple calibrations and method comparison exercises conducted in the Southern Ocean between New Zealand and the Ross Sea showed that the MIMS method provides pCO2 measurements that are consistent with those obtained by standard techniques (i.e. headspace equilibrator equipped with a Li–Cor NDIR analyser). The overall MIMS accuracy compared to Li–Cor measurements was 0.8 μatm. The O2/Ar ratio measurements were calibrated with air-equilibrated seawater standards stored at constant temperature (0 ± 1 °C). The reproducibility of the O2/Ar standards was better than 0.07% during the 9 days of transect between New Zealand and the Ross Sea.The high frequency, real-time measurements of dissolved gases with MIMS revealed significant small-scale heterogeneity in the distribution of pCO2 and biologically-induced O2 supersaturation (ΔO2/Ar). North of 65°S several prominent thermal fronts influenced CO2 concentrations, with biological factors also contributing to local variability. In contrast, the spatial variation of pCO2 in the Ross Sea gyre was almost entirely attributed to the biological utilization of CO2, with only small temperature effects. This high productivity region showed a strong inverse relationship between pCO2 and biologically-induced O2 disequilibria (r2 = 0.93). The daily sea air CO2 flux ranged from − 0.2 mmol/m2 in the Northern Sub-Antarctic Front to − 6.4 mmol/m2 on the Ross Sea shelves where the maximum CO2 influx reached values up to − 13.9 mmol/m2. This suggests that the Southern Ocean water (south of 58°S) acts as a seasonal sink for atmospheric CO2 at the time of our field study.  相似文献   

7.
The seasonal and interannual variability of the air–sea CO2 flux (F) in the Atlantic sector of the Barents Sea have been investigated. Data for seawater fugacity of CO2 (fCO2sw) acquired during five cruises in the region were used to identify and validate an empirical procedure to compute fCO2sw from phosphate (PO4), seawater temperature (T), and salinity (S). This procedure was then applied to time series data of T, S, and PO4 collected in the Barents Sea Opening during the period 1990–1999, and the resulting fCO2sw estimates were combined with data for the atmospheric mole fraction of CO2, sea level pressure, and wind speed to evaluate F.The results show that the Atlantic sector of the Barents Sea is an annual sink of atmospheric CO2. The monthly mean uptake increases nearly monotonically from 0.101 mol C m− 2 in midwinter to 0.656 mol C m− 2 in midfall before it gradually decreases to the winter value. Interannual variability in the monthly mean flux was evaluated for the winter, summer, and fall seasons and was found to be ± 0.071 mol C m− 2 month− 1. The variability is controlled mainly through combined variation of fCO2sw and wind speed. The annual mean uptake of atmospheric CO2 in the region was estimated to 4.27 ± 0.68 mol C m− 2.  相似文献   

8.
Calcification in the marine environment is the basis for the accretion of carbonate in structures such as coral reefs, algal ridges and carbonate sands. Among the organisms responsible for such calcification are the Corallinaceae (Rhodophyta), recognised as major contributors to the process world-wide. Hydrolithon sp. is a coralline alga that often forms rhodoliths in the Western Indian Ocean. In Zanzibar, it is commonly found in shallow lagoons, where it often grows within seagrass beds and/or surrounded by green algae such as Ulva sp. Since seagrasses in Zanzibar have recently been shown to raise the pH of the surrounding seawater during the day, and since calcification rates are sensitive to pH, which changes the saturation state of calcium carbonate, we measured the effects of pH on photosynthetic and calcification rates of this alga. It was found that pH had significant effects on both calcification and photosynthesis. While increased pH enhanced calcification rates both in the light and in the dark at pH >8.6, photosynthetic rates decreased. On the other hand, an increase in dissolved CO2 concentration to 26 μmol kg−1 (by bubbling with air containing 0.9 mbar CO2) caused a decrease in seawater pH which resulted in 20% less calcification after 5 days of exposure, while enhancing photosynthetic rates by 13%. The ecological implications of these findings is that photosynthetically driven changes in water chemistry by surrounding plants can affect calcification rates of coralline algae, as may future ocean acidification resulting from elevated atmospheric CO2.  相似文献   

9.
The distribution and optical absorption characteristics of chromophoric dissolved organic matter (CDOM) were systematically investigated along three meridional transects in the North Atlantic Ocean and Caribbean Sea conducted as part of the 2003 US CLIVAR/CO2 Repeat Hydrography survey. Hydrographic transects covered in aggregate a latitudinal range of 5° to 62° north along longitudes 20°W (line A16N, Leg 1), 52°W (A20), and 66°W (A22). Absorption spectra of filtered seawater samples were collected and analyzed for depths ranging from the surface to ∼6000 m, sampling all the ocean water masses in the western basin of the subtropical North Atlantic and several stations on the North and South American continental slopes. The lowest surface abundances of CDOM (< 0.1 m−1 absorption coefficient at 325 nm) were found in the central subtropical gyres while the highest surface abundances (∼0.7 m−1) were found along the continental shelves and within the subpolar gyre, confirming recent satellite-based assessments of surface CDOM distribution. Within the ocean interior, CDOM abundances were relatively high (0.1–0.2 m−1 absorption coefficient at 325 nm) except in the subtropical mode water, where a local minimum exists due to the subduction of low CDOM surface waters during mode water formation. In the subthermocline water masses of the western basin, changes in CDOM abundance are not correlated with increasing ventilation age as assessed using chlorofluorocarbon (CFC) concentrations and the atmospheric CFC history. But dissolved organic carbon (DOC) mass-specific absorption coefficients of CDOM increase with increasing ventilation age in the deep sea, indicating that CDOM is a refractory component of the DOC pool. The overall CDOM distribution in the North Atlantic reflects the rapid advection and mixing processes of the basin and demonstrates that remineralization in the ocean interior is not a significant sink for CDOM. This supports the potential of CDOM as a tracer of ocean circulation processes for subducted water masses.  相似文献   

10.
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11.
The Amazon River Plume delivers freshwater and nutrients to an otherwise oligotrophic western tropical North Atlantic (WTNA) Ocean. Plume waters create conditions favorable for carbon and nitrogen fixation, and blooms of diatoms and their diazotrophic cyanobacterial symbionts have been credited with significant CO2 uptake from the atmosphere. The fate of the carbon, however, has been measured previously by just a few moored or drifting sediment traps, allowing only speculation about the full extent of the plume's impact on carbon flux to the deep sea. Here, we used surface (0.5 m) sediment cores collected throughout the Demerara Slope and Abyssal Plain, at depths ranging from 1800 to 5000 m, to document benthic diagenetic processes indicative of carbon flux. Pore waters were extracted from sediments using both mm- and cm-scale extraction techniques. Profiles of nitrate (NO3) and silicate (Si(OH)4) were modeled with a diffusion-reaction equation to determine particulate organic carbon (POC) degradation and biogenic silica (bSi) remineralization rates. Model output was used to determine the spatial patterns of POC and bSi arrival at the sea floor. Our estimates of POC and Si remineralization fluxes ranged from 0.16 to 1.92 and 0.14 to 1.35 mmol m−2 d−1, respectively. A distinct axis of POC and bSi deposition on the deep sea floor aligned with the NW axis of the plume during peak springtime flood. POC flux showed a gradient along this axis with highest fluxes closest to the river mouth. bSi had a more diffuse zone of deposition and remineralization. The impact of the Amazon plume on benthic fluxes can be detected northward to 10°N and eastward to 47°W, indicating a footprint of nearly 1 million km2. We estimate that 0.15 Tmol C y−1 is remineralized in abyssal sediments underlying waters influenced by the Amazon River. This constitutes a relatively high fraction (~7%) of the estimated C export from the region.; the plume thus has a demonstrable impact on Corg export in the western Atlantic. Benthic fluxes under the plume were comparable to and in some cases greater than those observed in the eastern equatorial Atlantic, the southeastern Atlantic, and the Southern Ocean.  相似文献   

12.
We observed the partial pressure of oceanic CO2, pCO2 sea, and related surface properties in the westernmost region of the subarctic North Pacific, seasonally from 1998 to 2001. The pCO2 sea in the Oyashio region showed a large decrease from winter to spring. In winter, pCO2 sea was higher than 400 μatm in the Oyashio region and this region was a source of atmospheric CO2. In spring, pCO2 sea decreased to extremely low values, less than 200 μatm (minimum, 139 μatm in 2001), around the Oyashio region with low surface salinity and this region turned out to be a strong sink. The spatial variations of pCO2 sea were especially large in spring in this region. The typical Oyashio water with minimal mixing with subtropical warm water was extracted based on the criterion of potential alkalinity. The contribution of main oceanic processes to the changes in pCO2 sea from winter to spring was estimated from the changes in the concentrations of dissolved inorganic carbon and nutrients, total alkalinity, temperature and salinity observed in surface waters in respective years. These quantifications indicated that photosynthesis made the largest contribution to the observed pCO2 sea decreases in all years and its magnitude was variable year by year. These year-to-year differences in spring biological contribution could be linked to those in the development of the density stratification due to the decrease in surface salinity. Thus, the changes in the surface physical structure could induce those in pCO2 sea in the Oyashio region in spring. Furthermore, it is suggested that the direction and magnitude of the air-sea CO2 flux during this season could be controlled significantly by the onset time of the spring bloom. This revised version was published online in July 2006 with corrections to the Cover Date.  相似文献   

13.
Diurnal changes in seawater temperature affect the amount of air–sea gas exchange taking place through changes in solubility and buoyancy-driven nocturnal convection, which enhances the gas transfer velocity. We use a combination of in situ and satellite derived radiometric measurements and a modified version of the General Ocean Turbulence Model (GOTM), which includes the National Oceanic and Atmospheric Administration Coupled-Ocean Atmospheric Response Experiment (NOAA-COARE) air–sea gas transfer parameterization, to investigate heat and carbon dioxide exchange over the diurnal cycle in the Tropical Atlantic. A new term based on a water-side convective velocity scale (w*w) is included, to improve parameterization of convectively driven gas transfer. Meteorological data from the PIRATA mooring located at 10°S10°W in the Tropical Atlantic are used, in conjunction with cloud cover estimates from Meteosat-7, to calculate fluxes of longwave, latent and sensible heat along with a heat budget and temperature profiles during February 2002. Twin model experiments, representing idealistic and realistic conditions, reveal that over daily time scales the additional contribution to gas exchange from convective overturning is important. Increases in transfer velocity of up to 20% are observed during times of strong insolation and low wind speeds (<6 m s−1); the greatest enhancement from w*w to the CO2 flux occurs when diurnal warming is large. Hence, air–sea fluxes of CO2 calculated using simple parameterizations underestimate the contribution from convective processes. The results support the need for parameterizations of gas transfer that are based on more than wind speed alone and include information about the heat budget.  相似文献   

14.
The Earth’s most extensive biomes – the oceanic subtropical gyres – are considered to be expanding with current surface ocean warming. Although it is well established that microbial communities control gyre biogeochemistry, comparisons of their metabolic activities between gyres are limited. In order to estimate metabolic activities including production of microbial communities, the uptake rates of amino acids leucine, methionine and tyrosine at ambient concentrations were estimated in surface waters of the Atlantic Ocean using radioisotopically labelled tracers. Data were acquired during six research cruises covering main oceanic provinces herein termed: North and South Atlantic Gyres, Bermuda Atlantic Time-series Study site (BATS), Equatorial region, and Mauritanian Upwelling (off Cape Blanc). Data were divided between provinces, the extents of which were identified by ocean colour data, in order to achieve provincial mean uptake rates. Leucine and methionine uptake rates did not differ between sampling periods, and were comparable between the North and South subtropical gyres. Furthermore, variation in uptake rates measured throughout the two oligotrophic gyres, where sampling covered ∼4 × 106 km2, was considerably lower than that measured within the Mauritanian Upwelling and Equatorial regions, and even at the BATS site. Tyrosine was generally the slowest of the amino acids to be taken up, however, it was assimilated faster than methionine within the Mauritanian Upwelling region. Thus, we propose that one value for leucine (12.6 ± 3.2 pmol L−1 h−1) and methionine (10.0 ± 3.3 pmol L−1 h−1) uptake could be applied to the oligotrophic subtropical gyres of the Atlantic Ocean. However, with the significantly lower uptake rates observed at the BATS site, we would not advise extrapolation to the Sargasso Sea.  相似文献   

15.
Ocean acidification damages calcareous organisms, such as calcifying algae, foraminifera, corals, and shells. In this study, we made a device equipped with a Clark-type oxygen electrode and a pH-stat to examine how the most abundant calcifying phytoplankton, the coccolithophorid Emiliania huxleyi, responded to acidification and alkalization of the seawater medium. When E. huxleyi was incubated at pH 8.2, close to oceanic pH, the medium was alkalized during photosynthesis, and the alkalization rate [determined as μmol HCl added (mg Chl)−1 h−1] was identical to the activity of photosynthesis [determined as μmol O2 evolved (mg Chl)−1 h−1]. When pH was maintained at 7.2 by the pH-stat, alkalization activity was stimulated and exceeded photosynthetic activity, resulting in an increase in the ratio of alkalization to photosynthesis (Alk/PS). On the other hand, no alkalization and photosynthesis were observed at pH 9.2. In contrast, acidification of seawater was observed in the dark because of the release of respiratory CO2 from cells at pH 8.2–9.2, but not at pH 7.2. When orthophosphate was rapidly depleted within a day in the batch culture, intracellular calcification gradually increased, and both photosynthesis and alkalization decreased gradually. During the period the Alk/PS ratio also decreased gradually. These results indicate that E. huxleyi possesses an ability to compensate for the acidification of seawater when photosynthesis is more actively driven than respiration. These results suggest that the E. huxleyi cells may not be severely damaged by oceanic acidification during photosynthesis because of their homeostatic function to avoid negative effects on cellular activity. Finally, we concluded that E. huxleyi cells possess a buffering ability to reduce acidification effects when photosynthesis is actively driven.  相似文献   

16.
The interannual variations of CO2 sources and sinks in the surface waters of the Antarctic Ocean (south of 50°S) were studied between 1986 and 1994. An existing, slightly modified one-dimensional model describing the mixed-layer carbon cycle was used for this study and forced by available satellite-derived and climatological data. Between 1986 and 1994, the mean Antarctic Ocean CO2 uptake was 0.53 Pg C year−1 with an interannual variability of 0.15 Pg C year−1.Interannual variation of the Antarctic Ocean CO2 uptake is related to the Antarctic Circumpolar Wave (ACW), which affects sea surface temperature (SST), wind-speed and sea-ice extent. The CO2 uptake in the Antarctic Ocean has increased from 1986 to 1994 by 0.32 Pg C. It was found that over the 9 years, the surface ocean carbon dioxide fugacity (fCO2) increase was half that of the atmospheric CO2 increase inducing an increase of the air–sea fCO2 gradient. This effect is responsible for 60% of the Antarctic Ocean CO2 uptake increase between 1986 and 1994, as the ACW effect cancels out over the 9 years investigated.  相似文献   

17.
Coral community patterns on some Indonesian reefs influenced by CO2 from underwater volcanic vents and nutrients from eutrophication pressures were examined. The overall aim of the study was to provide an insight into the significance of future ocean acidification compared to eutrophication pressures on tropical coral communities. Coral cover and seawater characteristics at acidified sites (with varied levels of eutrophication), i.e., moderate acidification (pH: 7.87 ± 0.04), low acidification (pH: 8.01 ± 0.04) and reference (pH: 8.2 ± 0.02), were observed at reefs associated with Minahasa Seashore, and Mahengetang and Gunung Api Islands. Results showed that coral community patterns varied among locations and acidified sites, e.g., domination of families such as Alcyoniidae, Acroporidae, Poritidae and Heliporidae, and with different levels of abiotic cover. Surprisingly, pH was not detected as the major determining factor. This finding probably relates to tropical seawater temperatures being high enough to still allow for aragonite deposition even at pH values down to 7.8. Nutrients (phosphate and dissolved inorganic nitrogen) were shown to be the main determining factors that influenced community patterns on the observed coral reefs. Overall, the results indicate that tropical coral reef community patterns will continue to vary as pH decreases to the predicted oceanic value of pH 7.8 over the next 100 years, and bio‐geo‐ecological characteristics and anthropogenic pressures will be the major factors determining Indonesian tropical coral community structure, compared to pH.  相似文献   

18.
We compared in-situ and satellite-derived measures of the biological carbon pump efficiency at the two seemingly similar subtropical North Atlantic gyre time series sites, the Bermuda time series (BATS, Bermuda Atlantic time-series study and OFP, ocean flux program) in the western gyre and the ESTOC time series (European station for time-series in the ocean, Canary Islands) in the eastern gyre. Satellite-derived surface chlorophyll a was slightly lower at Bermuda compared to ESTOC (annual average of 0.10±0.04 vs. 0.14±0.05-mg-m?3), as was satellite-derived primary production (annual average of 380±77 vs. 440±80-mg C-m?2 d?1). However, export production normalized to primary production (export ratio) was higher at Bermuda by a factor of 2–3 when estimated using mesopelagic traps moored at 500-m depth and by a factor of 3–4 when estimated using surface-tethered drifting traps. When averaged seasonally, flux at BATS was highest in spring (March, April, May) at all depths followed by summer (June, July, August) and decreasing towards fall, but this seasonality was less visible at ESTOC. Seasonal comparison showed the fastest flux attenuation at Bermuda in winter and spring, coinciding with the highest POC flux. POC/PIC ratios derived from the moored traps were significantly higher at BATS than at ESTOC in fall and winter, but this difference was not significant in spring (p>0.05). This study shows that while the western and eastern Atlantic subtropical gyres have similar rates of primary production, the biological carbon pump differs between the two provinces. Higher new nutrient input observed at Bermuda compared to ESTOC might explain part of the difference in export ratio but alone is insufficient. Greater winter mixed-layer depths and higher mesoscale eddy activity at Bermuda resulting in pulsed production events of labile organic matter might explain both the higher export flux and export ratios found at Bermuda.  相似文献   

19.
王晓杰  肖潇  李超  岳娜 《海洋学报》2015,37(12):116-122
本文在实验室模拟近期海洋酸化水平,对海洋酸化对海水青鳉鱼(Oryzia melastigma)胚胎骨骼发育的影响进行了初步研究。实验中,通过往实验水体中充入一定浓度CO2气体酸化海水。对照组CO2分压为450×10-6,两个处理组CO2浓度分别为1 160×10-6和1 783×10-6,对应的水体pH值分别为8.14,7.85和7.67。将海水青鳉鱼受精卵放入实验水体中至仔鱼孵化出膜,对初孵仔鱼经骨骼染色、显微拍照,挑取了仔鱼头部、躯干及尾部骨骼染色清晰的28个骨骼参数的长度进行了显微软件测量及数据统计分析。结果发现,酸化处理对实验鱼所测量的骨骼长度影响均不显著。因此推测,未来100~200年间海洋酸化对海水青鳉鱼的胚胎及初孵仔鱼的骨骼发育没有显著影响。  相似文献   

20.
Coastal upwelling systems are regions with highly variable physical processes and very high rates of primary production and very little is known about the effect of these factors on the short-term variations of CO2 fugacity in seawater (fCO2w). This paper presents the effect of short-term variability (<1 week) of upwelling–downwelling events on CO2 fugacity in seawater (fCO2w), oxygen, temperature and salinity fields in the Ría de Vigo (a coastal upwelling ecosystem). The magnitude of fCO2w values is physically and biologically modulated and ranges from 285 μatm in July to 615 μatm in October. There is a sharp gradient in fCO2w between the inner and the outer zone of the Ría during almost all the sampling dates, with a landward increase in fCO2w.CO2 fluxes calculated from local wind speed and air–sea fCO2 differences indicate that the inner zone is a sink for atmospheric CO2 in December only (−0.30 mmol m−2 day−1). The middle zone absorbs CO2 in December and July (−0.05 and −0.27 mmol·m−2 day−1, respectively). The oceanic zone only emits CO2 in October (0.36 mmol·m−2 day−1) and absorbs at the highest rate in December (−1.53 mmol·m−2 day−1).  相似文献   

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