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1.
A sediment trap is a container deployed in the water column with the aim of providing a representative sample of the material settling through that water column before it passes to a greater depth and ultimately to the seabed or lake bottom. A review of the previous literature shows cylinders and baffled funnels to be the most efficient sediment trap design in flows less than 0.1 m/s. For flow velocities above 0.1 m/s recent evidence suggests upwelling from the trap base, and possible undercollection. The degree of undercollection depends on the flow velocity, the type of trap, the height: diameter (aspect) ratio of the trap, and the type of sediment. Recent experiments suggest that cylinders with an aspect ratio of 3 may be efficient collectors in velocities up to 0.2 m/s. The use of cylinders is not recommended in velocities above 0.2 m/s. For unbaffled asymmetric funnels a lower limit of 0.12 m/s is suggested.  相似文献   

2.
Disequilibrium between 234Th and 238U in water column profiles has been used to estimate the settling flux of Th (and, by proxy, of particulate organic carbon); yet potentially major non-steady-state influences on 234Th profiles are often not able to be considered in estimations of flux. We have compared temporal series of 234Th distributions in the upper water column at both coastal and deep-water sites in the northwestern Mediterranean Sea to coeval sediment trap records at the same sites. We have used sediment trap records of 234Th fluxes to predict temporal changes in water column 234Th deficits and have compared the predicted deficits to those measured to determine whether the time-evolution of the two coincide. At the coastal site (327 m water depth), trends in the two estimates of water column 234Th deficits are in fairly close agreement over the 1-month deployment during the spring bloom in 1999. In contrast, the pattern of water column 234Th deficits is poorly predicted by sediment trap records at the deep-water site (DYFAMED, 2300 m water depth) in both 2003 and 2005. In particular, the transition from a mesotrophic to an oligotrophic system, clearly seen in trap fluxes, is not evident in water column 234Th profiles, which show high-frequency variability. Allowing trapping efficiencies to vary from 100% does not reconcile the differences between trap and water column deficit observations; we conclude that substantial lateral and vertical advective influences must be invoked to account for the differences.Advective influences are potentially greater on 234Th fluxes derived from water column deficits relative to those obtained from traps because the calculation of deficits in open-ocean settings is dominated by the magnitude of the “dissolved” 234Th fraction. For observed current velocities of 5–20 cm s−1, in one radioactive mean-life of 234Th, the water column at the DYFAMED site can reflect 234Th scavenging produced tens to hundreds of kilometers away. In contrast, most of the 234Th flux collected in shallow sediment traps at the DFYFAMED site was in the fraction settling >200 m d−1; in effect the sediment trap can integrate the 234Th flux over distances 40-fold less than water column 234Th distributions. In some sense, sediment trap and water column sampling for 234Th provide complementary pictures of 234Th export. However, because the two methods can be dominated by different processes and are subject to different biases, their comparison must be treated with caution.  相似文献   

3.
《Oceanologica Acta》1998,21(4):521-532
A sediment trap experiment was carried out in the West Caroline Basin, located in the equatorial western Pacific between influences of the Asian monsoon and the open ocean. Annual mass flux at the shallow trap at Site 1 was 57.10 g m-2 yr-1. Generally, the higher flux of organic matter was associated with higher activities of biogenic opal-producing and carbonate-producing plankton communities. In addition, as the organic matter content increases, the organic carbon/carbonate carbon ratio shows a tendency to increase. Carbonate-producing plankton was predominant during periods 1 and 3 (May to July and November to the beginning of December), which could be due to limited silica supply to the euphotic zone. On the other hand, surface sea water was more nutrient-rich during periods 2 and 4 (August to October and the end of December to April) at Site 1. These high total mass fluxes could be stimulated by wind.The amount of biogenic components collected in the sediment traps and the accumulation in surface sediments at Site 1 could be compared with primary productivity values. Carbonate and biogenic opal fluxes were 99% and 90% less, respectively, in the surface sediments compared to those in the shallow sediment trap. This could be due to the reaction of sinking particles with undersaturated deep sea water just above the sea floor, rather than with the water column during sinking. About 20% of the organic matter was decomposed between the shallow and deep sediment traps and more than 98% between the deep sediment trap and final burial in the surface sediments. The relative amount of organic carbon preserved in surface sediments was about 0.10% of annual primary productivity.  相似文献   

4.
An array of four sediment trap moorings recorded the particulate flux across the Antarctic Circumpolar Current (ACC) at 170 °W, between November 1996 and January 1998, as part of the US JGOFS-Antarctic Environment and Southern Ocean Process Study (AESOPS) program. The trap locations represent sampling within the Polar Frontal Zone, the Antarctic Polar Front, the Antarctic Zone and the Southern Antarctic Zone. Here we report observations from 1000 m below the sea-surface compared to seafloor and surface water distributions. Sub-sample splits from each trap were obtained and total diatom flux and species composition were determined. The diatom fluxes were quantified using both a dilution and a ‘spike’ method to allow for the rapid repeatability of measurements. Diatom flux was found to be highly seasonal across the ACC particularly at higher latitudes. Marine snow aggregates of intact diatom cells and chains were the major components of the biogenic flux. Siliceous particle size was noted to decrease with increasing latitude, which could be aligned with a shift of the diatom assemblage to small-size species/sea-ice affiliated species. A ‘double-structured’ diatom flux was recorded at the location of the Antarctic Polar Front trap, with a shift in the diatom assemblage from larger to smaller diatoms in the second flux episode. The sediment trap assemblage shows deviations from the surface water assemblage, while surface sediment samples indicate that significant dissolution occurs after 1000 m and at the sediment–water interface. Estimation of diatom biovolumes across the ACC shows that large diatoms have the potential to greatly impact biogenic fluxes to the ocean interior despite their low fluxes. Small species of the genus Fragilariopsis could potentially export as much Corg as Fragilariopsis kerguelensis near the retreating ice edge. However, their low abundance in the surface sediments also suggests that these diatoms are a shallow export species.  相似文献   

5.
Chemistry of organic materials of the suspended and sinking particles, and the evaluation of the particulate materials for the carbon cycle of the ocean are described in this paper. Organic carbon (POC) and nitrogen (PON) of the suspended particles collected from various areas of the North through South Pacific were determined with considerably high variabilities in their concentration. Higher values of the POC and PON were obtained in the surface water of the higher latitudinal areas of both northern and southern hemispheres and the equatorial Pacific, while the lower values of these organic elements were measured in the middle latitudinal areas of the Pacific. These facts clearly indicate that inorganic nutrients supply to the surface water layers from the underlying water is primarily determinative factor to govern the concentration of the POC and PON in the surface water layer. POC and PON concentrations in the intermediate through deep waters, however, are much less variable in time and space. Carbohydrates, free and combined amino acids and lipid materials were major organic constituents of the suspended particles. The organic composition of the particles was extensively variable in region, time and depth. Such change in the organic composition was mainly caused by the production and decay of the free and combined amino acids, lipid materials and water extractable carbohydrate. Sinking particle which has high sinking rate over 100 m day−1 and can be collected only by sediment trap, also consists of carbohydrates, free and combined amino acids and lipid materials. A detailed analysis of the particle indicate that the sinking particle was much different from the suspended particle from the intermediate through deep waters in terms of the abundance of the biologically susceptible organic materials such as unsaturated hydrocarbon, fatty acid and water extractable carbohydrate often found in phytoplankton. These facts clearly indicate that the sinking particle plays an important role on the vertical transport of the biologically susceptible organic materials from the surface water to the deep water. Vertical flux of organic materials in various water depths was extensively measured in the North Pacific and Antarctic Ocean using the depth-series sediment trap system to collect the sinking particles from various depths of the waters. Regional and seasonal variabilities of the organic carbon flux at the various depths were obviously observed, however the attenuation rate of the organic carbon flux in the intermediate through deep water was not changed so much irrespective of the sampling time and region. The time-series sediment trap system was also using to determine the seasonal variation of the organic carbon flux. An average organic carbon flux at 1 km depth from this trap system was almost comparable to the amount of organic carbon degraded in the water deeper than 1 km depth, which was calculated from oxygen consumption rate of the deep water. Thus, it is clear that the sinking particle must play an important role in the carbon cycle of the deep water.  相似文献   

6.
Sinking particles collected from year-long time-series sediment traps at 1674, 4180, 5687 and 8688 m depths, the underlying bottom sediment at 9200 m depth, and suspended particles from surface and subsurface waters in the northwestern North Pacific off Japan were analyzed for long-chain alkenones and alkyl alkenoates (A&A) which are derived mainly from Gephyrocapsacean algae, especially Emiliania huxleyi and Gephyrocapsa oceanica. Alkenone temperature records in sediment trap samples at 1674 m were almost similar to observed sea surface temperatures (SST) with a time delay of one half to one full month. However, alkenone temperatures in trap samples were about slightly lower than measured SST in late spring to early fall. The lowering might be caused by formation of the seasonal thermocline. Nevertheless, these temperature drops observed in trap samples were smaller than those actually observed in a subsurface layer off central Japan. Vertical profiles of A&A concentrations and alkenone temperatures in suspended particles collected from the subsurface waters in early fall indicated that these compounds were produced mostly in a surface mixed layer above the depth of the chlorophyll maximum even in warm seasons. These results suggested that alkenone temperatures strongly reflected SST rather than the temperatures of thermocline waters in these study areas even in such a warm season. Pronounced maxima in A&A fluxes found in sediment trap samples at 1674 m in late spring to summer showed that A&A productions were highest during the periods of spring bloom, according to a time delay between alkenone temperatures and observed SST. Seasonal patterns of alkenone records in trap samples at 4180 and 5687 m could also preserve SST signals well, suggesting that A&A in deep sea waters were mainly derived from primary products in the surface layer. A&A fluxes tended to decrease with water depth, and the ratios of A&A to particulate organic carbon (POC) rapidly decreased in underlying bottom sediment. This clearly indicates that A&A were decomposed and diluted by other refractory organic materials in either the water column or the sediment–water interface. However, A&A compositions were consistently uniform between the trap samples and the underlying bottom sediments, so that A&A could not qualitatively alter during early diagenetic processes.  相似文献   

7.
Sediment traps are an important tool for studying the source, composition and sedimentation processes of sinking particulate matter in the ocean. An in situ observational mooring(TJ-A-1) is located in the northern South China Sea(20.05°N, 117.42°E) at a water depth of 2 100 m and equipped with two sediment traps deployed at 500 m and 1 950 m. Samples were collected at 18-day intervals, and 20 samples were obtained at both depths from May 2014 to May 2015. Large amounts of fecal matter and marine snow were collected in the lower trap. The fluxes of marine snow and fecal pellets exhibited a fluctuating decrease between May 2014 and early August 2014 and then stabilized at a relatively low level. Scanning electron microscopy observations revealed that the main components of the marine snow and fecal pellets were diatoms, coccolithophores, radiolarians, and other debris, all of which are planktons mostly produced in photic zone. Used in conjunction with the particle collection range estimates from the lower trap and data on ocean surface chlorophyll, these marine snow and fecal pellets were related to the lateral transport of deep water and not vertical migrations from overlying water column. Moreover, the source area might be southwest of Taiwan.  相似文献   

8.
Spatial and temporal variations in the vertical fluxes of amino acids and hexosamine were studied at coastal sites in the south of the Chukchi Sea, Otsuchi Bay, and the center and the entrance of Funka Bay. Amino acid fluxes were higher in the upper trap than in the lower trap material, but hexosamine fluxes were opposite to amino acid fluxes. The ratios between protein amino acids (Asp, Glu and Arg) and their decomposition products (β-Ala, γ-Aba and Orn) indicate that the labile organic matter was more abundant in the upper traps than in the lower ones and increased during periods of enhanced amino acid fluxes. The ratios of Ser/Gly did not vary temporally and spatially and were nearly constant, indicating that Ser and Gly were preserved in a stable form within sinking particles. Hexosamine/amino acid ratios of these particles were higher in the lower sediment trap than in the upper trap material. This implies that the sinking particles derived from zooplankton are relatively more abundant in deep layers than in the surface layer in the water column. We suggest that the difference in amino acid flux and the composition between the upper and lower trap material is influenced by the processes of microbial decomposition and zooplankton consumption of sinking particulate organic matter. This revised version was published online in July 2006 with corrections to the Cover Date.  相似文献   

9.
南海北部陆缘盆地与坎坡斯盆地   总被引：3，自引：1，他引：2  
我国南海是西太平洋最大的边缘海,其北部陆缘盆地深水区位于琼东南与珠江口盆地南侧.通过对该地区烃源条件、储层条件、圈闭条件及成藏模式等的初步研究,认为其具有良好的石油地质条件,有效勘探面积和勘探潜力巨大,具有良好的勘探前景.坎坡斯盆地位于巴西大西洋大陆边缘,是一个中生代到古新近纪含油气盆地,其内部的Garoupa, Carapeba, Namorado, Roncador, Marlim等深水油田的地质储量十分丰富,随着各个油田开发的深入,对该地区的深水含油气系统有了更加清晰的了解.本文通过两个地区在构造演化,烃源条件,储层条件,圈闭条件以及成藏模式的对比研究,对南海北部陆缘盆地深水区有了进一步的认识.  相似文献   

10.
Time-series Mark 7 sediment traps were deployed at three stations at 0°N, 13°N and 48°N along 175°E to investigate seasonal and spatial variations of particulate material flux. Chemical analysis of particulate material was performed for four major chemical components, viz. opal, CaCO3, organic material and clay minerals, Cd and P in the particulate material were also determined. We discuss the characteristics of particulate material at each site and the transportation of Cd and P to deep water by the particulate material. The total mass fluxes and variation of fluxes at each site reflect oceanographic conditions, such as biological productivity and kind of major planktonic organisms. At the northern site, large mass fluxes with a spring bloom and high ratios of opal are characteristic. Relatively small mass fluxes with high ratios of CaCO3 are distinct, and dissolution of CaCO3 due to sinking is recognized in the middle latitude and 0°N sites. The larger flux at the lower trap than the upper trap at the equatorial site suggests influence by lateral transport in the deep water. Distinctive decreasing Cd/P ratio and CaCO3 concentrations in the particulate material with increasing depth suggests that the change of Cd/P ratio in the intermediate and deep water occurs through the dissolution of CaCO3. The dissolved Cd/P ratios in the deep water are proportional to the age of the deep water in the Atlantic but not in the Pacific. This is explained by the difference of kinds of particulate material transporting Cd and P in the deep water between the oceans. That is, the major planktonic organisms are planktons of CaCO3 tests in the Atlantic Ocean and diatoms of opal tests in the North Pacific Ocean.  相似文献   

11.
Sediment traps were deployed at 5 depths of 100 through 5,250 m to collect suspended sediments in the northern North Pacific (47°51.1'N; 176°20.6'E, 5,300 m deep) in the summer of 1978. Fatty acid composition was determined in the samples of phytoplankton, particulate matter, trap sediment and bottom sediment.Fatty acid composition of the trap sediments revealed no significant vertical trend throughout the water column from depths of 100 to 5,250 m, and were also similar to those of the phytoplankton and the particulate matter from the euphotic layer. However, a marked difference in the fatty acid composition was observed between the trap sediments and the particulate matter from deep waters. Therefore, it can be concluded that the source of fatty acids in the trap sediments is the particulate matter from the euphotic layer but not from deep waters.Unsaturated fatty acids highly susceptible to biological agents were rather abundant in the trap sediments as well as in the phytoplankton and particulate matter from the euphotic layer, however no unsaturated fatty acid was found in the particulate matter from deep waters. From these findings, it is clear that the particulate matter of the euphotic layer is transported to deep waters very rapidly. As the sinking rate of fecal pellets produced by zooplankton is in the range of ten to hundreds of meters a day, fecal pellets are assumed to be the most likely carrier of rapid-transport of organic matter including fatty acids from the euphotic layer to deep waters.  相似文献   

12.
A time-series sediment trap was deployed from December 1994 to February 2002 at the mouth of Tokyo Bay (35°03′ N, 139°40′ E; water depth, 850 m). Sinking particles were obtained with a time interval of one week at a depth of approximately 100 m above the sea floor. Observed total mass fluxes varied from 3.3 to 226.7 g/m2/day with an average of 28.0 g/m2/day. Concentrations of rare earth elements, Al, Ca and Si in particulate materials were measured. The combustible fraction at 450°C is assumed to be equivalent to the organic matter content. Contents of biogenic materials, namely organic matter, opal and calcium carbonate, were about 30% and the content of lithogenic material was about 70%. Using La/Yb ratios of particles from the sediment trap and Tama-gawa River and surface sediment of Tokyo Bay, it was estimated that about 50% of the lithogenic particles collected in the sediment trap at the mouth of Tokyo Bay originated from resuspended surface sediment in Tokyo Bay. An increasing trend of Opal/CaCO3 ratio in the sinking particles was found in the spring season. It is suggested that the relative increase of diatoms is due to the decreasing dissolved inorganic nitrogen input into Tokyo Bay.  相似文献   

13.
《Journal of Sea Research》1999,41(1-2):19-33
Electron microprobe analysis of suspended-matter samples collected at different water depths at ten stations in the Angola Basin indicated that at each station, from top to bottom, the elementary composition of the suspended matter was very similar and differed from the composition of the suspended matter at the adjacent stations. This indicates that the downward settling of the suspended matter is much faster than the horizontal transport and mixing by the currents. Assuming that the suspended matter settles in the form of flocs, or is scavenged by settling flocs, the suspended matter can indeed reach the bottom in a shorter period than needed for the currents to cover the distance between adjacent stations. Comparison with sediment trap data from the literature shows that also lateral transports and/or deep water gyres have to be invoked to further increase residence times of suspended matter in the water column.  相似文献   

14.
Understanding biogenic silica (bSi) dissolution kinetics in margin environments is important in assessing the global silicon cycle, a cycle closely linked to the global carbon cycle. This understanding is also essential to answer the question of whether bSi content in marine sediment is a valid indicator of productivity in the overlying surface ocean. In this study, plankton tow, sediment trap, and sediment samples were collected at sites in three Southern California borderland basins. Batch dissolution experiments with plankton tow and sediment trap materials (conducted in the laboratory at 22 °C) showed linear dissolution kinetics, from which mean dissolution rate constants of 0.05 d? 1 for plankton tow samples and 0.07 d? 1 for sediment trap samples could be calculated. The dissolution rate constants for both types of samples showed seasonal variability but not the same seasonal patterns. Faster dissolution was observed with sediment trap samples collected at 800 m than at 550 m. With sediment multi-core samples, non-linear dissolution kinetics was observed, which complicates the direct comparison of dissolution rates. Nonetheless, dissolution appeared to be slower for the sediments samples than for samples collected from the water column and to decrease with depth in the sediments. Rate constants for surface sediment (0–0.5 cm) were at least 3–5 times less, and sediments at depths > 2 cm had rate constants at least 6–13 times less than those for material sinking to the sediment surface at these sites. Dissolution experiments conducted with Santa Barbara Basin surface sediment samples amended with dissolved aluminum (Al) and San Pedro Basin trap samples amended with enriched detrital materials (obtained by leaching bSi from sediment samples) suggested that dissolution was inhibited by Al and that the sediments from the different basins varied in the extent of Al release.  相似文献   

15.
The flux of planktonic foraminifera between 100 μm and 1 mm to the seafloor has been estimated for the central Pacific (abyssal plain east of Hawaii) and the tropical Atlantic (Demerara Abyssal Plain) based on sediment trap samples collected from various water depths. The faunas in each region are quite similar, with 4 to 5 species generally accounting for 70–80% of the total assemblage.

At both study sites, the total foraminiferal flux and the carbonate flux tend to decrease with depth. In addition, the flux of individual species of planktonic foraminifera varies significantly with depth, with the number of small, solution-susceptible species decreasing with increasing water depth. These results suggest that there is significant dissolution of small (< 150 μm) foraminifera as they settle through the water column. Material collected from the sediment-water interface directly below the Pacific sediment trap array contains no planktonic foraminifera, suggesting that the residence time of an individual on the seafloor before it dissolves, is extremely short.  相似文献   


16.
墨西哥湾深水勘探区带是近年深水勘探活动最活跃的地区之一,通过对其石油地质条件以及勘探特点的综合分析,认为其具有优越的石油地质条件,其勘探研究具有4个特点:1地震技术革新极大推进了该区的勘探研究;2盐岩活动控制圈闭和油气藏的形成;3墨西哥湾深水区圈闭勘探呈明显的分带性;4圈闭落实和储层发育程度是主要勘探难点。并指出盐下圈闭落实和储层预测是制约该盆地勘探成功率的两大关键问题,而盐下地震成像、古盐构造恢复和古沉积水道的预测是解决这两大关键问题的主要手段。  相似文献   

17.
Planktic foraminiferal (PF) flux and faunal composition from three sediment trap time series of 2002–2004 in the northeastern Atlantic show pronounced year-to-year variations despite similar sea surface temperature (SST). The averaged fauna of the in 2002/2003 is dominated by the species Globigerinita glutinata, whereas in 2003/2004 the averaged fauna is dominated by Globigerinoides ruber. We show that PF species respond primarily to productivity, triggered by the seasonal dynamics of vertical stratification of the upper water column. Multivariate statistical analysis reveals three distinct species groups, linked to bulk particle flux, to chlorophyll concentrations and to summer/fall oligotrophy with high SST and stratification. We speculate that the distinct nutrition strategies of strictly asymbiontic, facultatively symbiontic, and symbiontic species may play a key role in explaining their abundances and temporal succession. Advection of water masses within the Azores Current and species expatriation result in a highly diverse PF assemblage. The Azores Frontal Zone may have influenced the trap site in 2002, indicated by subsurface water cooling, by highest PF flux and high flux of the deep-dwelling species Globorotalia scitula. Similarity analyses with core top samples from the global ocean including 746 sites from the Atlantic suggest that the trap faunas have only poor analogs in the surface sediments. These differences have to be taken into account when estimating past oceanic properties from sediment PF data in the eastern subtropical North Atlantic.  相似文献   

18.
The DYFAMED sediment trap station in the Ligurian Sea (NW Mediterranean) has been active since 1986 and today comprises the longest time‐series of downward particle flux in the Mediterranean Sea. As such, it provides valuable information on the interannual variability of the particle flux, and also documents possible recent changes in the NW Mediterranean pelagic ecosystems. We report an unprecedented episode of downward flux of mucilaginous material at the DYFAMED station during summer 2002 in association with singular hydrometeorological conditions. The rain of mucilaginous aggregates clogged a PPS5 sediment trap at 260 m depth and was also clearly detected at 1080 m depth. The possible factors governing the development and sinking of the mucilaginous material are discussed. A very sharp increase of sea surface temperature during June and the presence of freshened waters in the surface the following month resulted in a stronger than usual stratification of the upper water column throughout the summer season. We suggest that the steepness of the vertical density gradient was responsible for the unusual accumulation of mucous aggregates. Additionally, a diatom bloom took place during the nutrient‐depleted conditions typical of summer, a factor which may have contributed to feed the pycnocline with transparent exopolymer substances. A storm occurring in the beginning of August relaxed the stratification and promoted the deposition of the mucilaginous aggregates accumulated in the upper water column during the preceding months. Important similarities of ambient conditions preceding the apparition of mucilaginous material in our open‐sea site and those reported in the Adriatic Sea during major mucilage events, suggest that general climatic conditions, rather than local factors, drive the occurrence of major accumulations of mucilaginous material in the water column at both sub‐basins of the Mediterranean Sea. In this regard, the strength of the air temperature increase during the onset of the stratified season is proposed as a major controlling factor.  相似文献   

19.
Downward particle flux was measured using sediment traps at various depths over the Porcupine Abyssal Plain (water depth 4850 m) for prolonged periods from 1989 to 1999. A strong seasonal pattern of flux was evident reaching a maximum in mid-summer. The composition of the material changed with depth, reflecting the processes of remineralisation and dissolution as the material sank through the water column. However, there was surprisingly little seasonal variation in its composition to reflect changes in the biology of the euphotic zone.Currents at the site have a strong tidal component with speeds almost always less than 15 cm/sec. In the deeper part of the water column they tend to be northerly in direction, when averaged over periods of several months.A model of upper ocean biogeochemistry forced by meteorology was run for the decade in order to provide an estimate of flux at 3000 m depth. Agreement with measured organic carbon flux is good, both in terms of the timings of the annual peaks and in the integrated annual flux. Interannual variations in the integrated flux are of similar magnitude for both the model output and sediment trap measurements, but there is no significant relationship between these two sets of estimates. No long-term trend in flux is evident, either from the model, or from the measurements.During two spring/summer periods, the marine snow concentration in the water column was assessed by time-lapse photography and showed a strong peak at the start of the downward pulse of material at 3000 m. This emphasises the importance of large particles during periods of maximum flux and at the start of flux peaks. Time lapse photographs of the seabed show a seasonal cycle of coverage of phytodetrital material, in agreement with the model output both in terms of timing and magnitude of coverage prior to 1996. However, after a change in the structure of the benthic community in 1996 no phytodetritus was evident on the seabed.The model output shows only a single peak in flux each year, whereas the measured data usually indicated a double peak. It is concluded that the observed double peak may be a reflection of lowered sediment trap efficiency when flux is very high and is dominated by large marine snow particles.Resuspension into the trap 100 m above the seabed, when compared to the primary flux at 3000 m depth (1800 mab) was lower during periods of high primary flux probably because of a reduction in the height of resuspension when the material is fresh. At 2 mab, the picture is more complex with resuspension being enhanced during the periods of higher flux in 1997, which is consistent with this hypothesis. However there was rather little relationship to flux at 3000 m in 1998.At 3000 m depth, the Flux Stability Index (FSI), which provides a measure of the constancy of the seasonal cycle of flux, exhibited an inverse relationship with flux, such that the highest flux of organic carbon was recorded during the year with the greatest seasonal variation.  相似文献   

20.
于2005年3月至2006年4月在大亚湾的大鹏澳养殖区采用沉积物捕捉器,对甲藻孢囊形成和水温、盐度、营养盐含量等环境因子进行了周年调查,探索该区孢囊形成特征及其与环境因子的关系.在一年的沉积物捕捉器研究中,共分析鉴定出27种甲藻孢囊类型,锥状斯氏藻Scrippsiella trochoidea孢囊为该区最优势孢囊类群,从孢囊的组成显示了该区的污染是以养殖和生活污染为主.孢囊形成没有明显的季节分布特征,两个站年平均为1.07×10<'5>cysts·(m<'2>·d)<'-1>.高、低温都能在一定程度上促进孢囊的生成,氮限制对孢囊的形成具有明显促进作用.首次发现亚历山大藻Alexandrium孢囊在冬季形成的高峰,最高值达4.26×10<'5>cysts·(m<'2>·d)<'-1>.这说明核电站温排水冬季高水温对大亚湾生态环境有较大的影响.  相似文献   

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