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1.
《Marine Chemistry》2001,73(1):37-51
Vertical profiles of 14C-uptake were acquired monthly from the mouths and landward stations of periodically anoxic Saanich Inlet and oxygenated Jervis Inlet, British Columbia, Canada from August 1985 to October 1989. Saanich Inlet (490 g C m−2 year−1) was 1.7 times more productive than Jervis Inlet (290 g C m−2 year−1) and primary production toward the mouths of both inlets was 1.4 times higher than at the landward stations. The elevated rates of primary production in Saanich Inlet may have been due to exchange with the nutrient-rich surface waters of the passages leading to the Pacific Ocean and the up-inlet gradients in both fjords also may have reflected relative nutrient supply. Sediment-trap results show enhanced fluxes of biogenic silica to the deep waters of Saanich Inlet; associated organic matter is likely to have caused a large oxygen demand. Combined with the high primary production and export flux, low rates of vertical mixing and particle-entrapment within the fjord, factors associated with weak estuarine circulation as well as weak winds and tides in Saanich Inlet, may also stimulate anoxia.Although in Jervis Inlet there is more stagnant water behind the sill and deep-water renewals appear to be less frequent than in Saanich Inlet, the deep sill allows degradation of a significant fraction of the sinking organic matter before the stagnant waters are reached, reducing the chances of oxygen depletion in the bottom waters.  相似文献   

2.
The mixing and circulation associated with a bathymetrically arrested estuarine front was studied using hydrographic and current data. A quasisteady front, exhibiting strongly convergent surface flows, is formed along the steeply sloping inner margins of the flood tide delta during each semidiurnal tide cycle. This front separates the brackish ambient water within a deep estuarine basin from the incoming oceanic tidal water. The position of the front is dependent on the local water depth and the difference in density between the two water masses. Beneath the surface there is an inclined frontal interface where static stability is very low and vertical mixing intense. A vertically integrated horizontal momentum equation was derived for flow in the upper layer and an estimate made as to the value of the associated entrainment coefficient.  相似文献   

3.
The concentration distribution was studied for dissolved oxygen, phosphorus forms, and particulate matter in Curonian Bay of the Baltic Sea in poorly known consolidated ice cover conditions during the winter seasons of 2010, 2011, and 2013. The surface and near-bottom waters were sampled at 51 stations. The ice cover exerts no significant effect on the typical seasonal variation of all considered parameters in the basin. The concentrations of mineral and organic phosphorus in the bay appeared to be lower by factors of 2–4 compared to summer values. A two- to threefold decrease in the concentrations of organic phosphorus since 2010 to 2011 and then to 2013 was recorded in the bay, which resulted from a decrease in phosphorus production by phytoplankton. Despite water being isolated from air by ice, the absence of wave mixing, and the decrease in oxygen production owing to the seasonal winter decrease in the intensity photosynthetic processes, no oxygen deficiency was found in the basin. This is because oxygen supplied to the bay by river runoff and production by photosynthesis in the bay exceed the utilization for oxidation of organic matter resulting from low bioproductivity of the waters during winter. The winter decrease in the fraction of biogenic particulate matter is seen as a four- to sevenfold drop in its total concentration in the waters compared to summer seasons. The absence of wave roiling of bottom sediments also caused a decrease in the secondary supply of biogenic particulate matter from sediments into near-bottom waters. No negative trends of geoecological conditions in the bay were revealed by the studied parameters under consolidated ice cover conditions.  相似文献   

4.
Worldwide estuarine ecosystems are by their privileged geographic location, anthropogenically impacted systems. Heavy metal contamination in estuarine waters and sediments are well known to be one of the most important outcomes driven from human activities. The partitioning of these elements has been widely focused, due to its importance not only on the estuarine biogeochemistry but also on its bioavailability to the trophic webs. As observed in other estuaries, in the Tagus basin, no increase in the partition coefficients with the increasing suspended particulate matter concentrations was observed, mostly due to a permanent dilution process of the suspended matter, rich in heavy metals and less contaminated and resuspended bottom sediments. Another important outcome of this study was the common origin of all the analysed heavy metals, probably due to the large industrialization process that the margins of the Tagus estuary suffered in the past, although no relationship was found with the presence of the different discharge areas. In fact, metal partitioning seems to be mostly influenced by the chemical species in which the pollutant is delivered to the system and on water chemistry, with a higher emphasis on the metal cycling essentially between the particulate and dissolved phase. This partitioning system acquires a relevant importance while evaluating the impacts of marine construction and the associated dredging operations, and consequent changes in the estuarine water chemistry.  相似文献   

5.
The concentrations of rare earth elements in the dissolved, acid-soluble and residual phases in surface waters of the Changjiang Estuary were determined using ICP-MS. The main purposes of the study are to understand the estuarine geochemistry of rare earth elements and to explore water-particle interactions in the Changjiang estuarine mixing zone. The results show that there are two distinct processes operating on dissolved rare earth elements in the estuary: large scale removal at low salinities due to salt-induced coagulation and remarkable release at mid to high salinities. These processes result in modification of the effective river water flux and the systematical fractionation of the dissolved rare earth elements toward the East China Sea. The increase in concentration of dissolved rare earth elements in the mid to high salinity waters of the Changjiang Estuary suggests a sediment source in the mixing zone of the estuary, which is located over a shallow, broad shelf where there is extensive physical contact between bottom sediment and estuarine waters. Acid-soluble rare earth elements, the concentrations of which also dropped sharply in the low salinity region, appear to be controlled by salt-induced coagulation process and intense deposition of suspended particulate matter in the low salinity region. In the mid to high salinities, all acid-soluble rare earth element concentrations increase slightly with increasing salinity, suggesting that resuspension of sediments occurred. In contrast, the residual rare earth element concentrations are relatively constant with salinity variation in the Changjiang estuarine surface waters.  相似文献   

6.
The distributions of dissolved and solid phase Fe and Mn have been variously determined in vertical profiles through the water column and sediments at three stations in Bolstadfjord, S.W. Norway. Elevated concentrations of dissolved and suspended particulate Fe and Mn are associated with restricted deep waters as a result of redox reactions and with river discharge. The basin sediments are anoxic throughout but because of the greatly restricted circulation, remobilized Fe and Mn appear to remain predominantly trapped within the fjord. Differentiation of Fe and Mn occurs to the extent that Fe sulphide precipitation is ubiquitous in the sediments whereas the entrapment of Mn, probably through Mn carbonate precipitation, is found only in the sediments of the more seaward basin (maximum Mn content of 1·5% by weight).  相似文献   

7.
Suspended particulate matter (SPM) collected at regular stations from the Mandovi and Zuari estuaries indicates that the peaks of high SPM coincide with peaks of high rainfall and low salinity and also with peaks of moderate/low rainfall coupled with high salinity during the monsoon. The estuarine turbidity maximum (ETM) is a characteristic feature, it occurs in the channel accompanying spring tide during the monsoon and pre-monsoon, and shifts to the bay on neap tide during post-monsoon. ETM remains at the same position in the Mandovi River, both during the monsoon and pre-monsoon, whereas in Zuari it stretched upstream during monsoon and migrates seaward of the channel during pre-monsoon. The ETM coincides with the freshwater–seawater interface during the monsoon and is formed by the interaction between tidal currents and river flows. The ETM during pre-monsoon is associated with high salinities and is generated by tidal and wind-induced currents. The turbidity maximum on neap tide during post-monsoon may be due to the erosion and resuspension of sediments from the emergent tidal flats and transport of these turbid waters into the bay. Funneling effect of the narrowing bay in the Zuari estuary and associated physical processes effectively enhance the magnitude of the currents and transports sediments to the channel. SPM retention percentage indicates that the estuarine channel is prone to siltation.  相似文献   

8.
The report considers the distribution of the salinity, the particulate matter, and the dissolved and particulate forms of iron in the Amur Liman and Sakhalin Gulf under different volumes of the riverine runoff during the summer periods. It was shown that the influence of the runoff variations is pronounced in the composition of the surface layer of the estuarine and coastal waters but smoothed within the bounds of the Sakhalin Gulf. The dissolved iron is additionally exposed to the smoothing effect of the coagulation processes under the mixing of the riverine and marine waters. The calculation of the iron utilization by the plankton points to the key role of the production processes in the Sakhalin Gulf for the further migration of iron over the Sea of Okhotsk.  相似文献   

9.
The distribution of the natural radionuclide 210Po in the water column along a horizontal transect of the continental shelf, slope and deep basin regions of the East Sea (Sea of Japan), a marginal sea of the Northwest Pacific Ocean, was investigated, and its behavior is described here. The settling fluxes of particulate 210Po in the deep basin along with 210Pb, 234Th and biogenic matter were also determined. 210Po inventories in the water column were observed to decrease from winter to summer in all stations, probably due to increased influx of 210Po-poor Kuroshio Water of the Northwest Pacific Ocean during summer. Vertical profiles of dissolved and particulate 210Po along with the settling fluxes of particulate 210Po in the deep basin station have enabled us to evaluate temporal variations and residence times of 210Po. In the slope and basin, activities of dissolved 210Po generally decreased from the surface to the bottom water, with maximum activity just below the subsurface chlorophyll a maximum at 50–75 m depth in spring and summer. These subsurface peaks of dissolved 210Po activity were attributed to the release of 210Po from the decomposition of 210Po-laden biogenic particulate organic matter. In the deep basin, despite the decrease in total mass flux, the sinking flux of particulate 210Po was higher in the deeper trap (2000 m) than in the shallower one (1000 m), probably due to scavenging of dissolved 210Po from the water column during particle descent and/or break-down of 210Po-depleted particulate matter between 1,000 m and 2,000 m depths. In general, the ratios of the particulate phase to the dissolved phase of 210Po (Kd) increased with depth in the slope and basin stations. 210Po removal from the water column appears to depend on the primary productivity in the upper waters. There is an inverse relationship between Kd and suspended particulate matter (SPM) concentration in the water column. From the 210Po activity/chlorophyll a concentration ratios, it appears that sinking particles arriving at 1000 m depth were similar to those in the surface waters.  相似文献   

10.
The winter oceanography of four New Zealand fiords is discussed using data obtained from July 1983, and comparisons are made with data collected on previous summers. Surface waters were more saline in winter than in summer and were everywhere cooler than the underlying water. Deep water renewal in the fiord basins was re‐examined using all available data. For Milford Sound and the other deep silled fiords renewal appears to be related to the arrival of dense water at sill depth offshore by an as yet unknown advective or meteorologically forced process. In the more isolated Long Sound, Preservation Inlet, deep water renewal requires the subtle interplay of tidal flows and mixing processes over the shallow double sill. Complete renewal of Long Sound bottom water appears to be a slow process.  相似文献   

11.
Stable carbon and nitrogen isotopic composition of particulate organic matter(POM) were measured for samples collected from the Bering Sea in 2010 summer. Particulate organic carbon(POC) and particulate nitrogen(PN) showed high concentrations in the shelf and slope regions and decreased with depth in the slope and basin, indicating that biological processes play an important role on POM distribution. The low C/N ratio and heavy isotopic composition of POM, compared to those from the Alaska River, suggested a predominant contribution of marine biogenic organic matter in the Bering Sea. The fact that δ13C and δ15N generally increased with depth in the Bering Sea basin demonstrated that organic components with light carbon or nitrogen were decomposed preferentially during their transport to deep water. However, the high δ13C and δ15N observed in shelf bottom water were mostly resulted from sediment resuspension.  相似文献   

12.
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   

13.
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14.
Previous observations in the Gareloch, a Scottish silled fjord, have identified yet failed to explain the baroclinic circulation pattern. Additional fieldwork was carried out in April 2005, showing the loch to be stratified with two distinct layers and currents in each layer 180° out of phase at the M2 frequency. The currents did not display the expected sinusoidal signal that is characteristic of the tide and instead were pulsated and stronger than predicted by barotropic forcing. Fourier analysis showed that the flow was dominated by short period non-linear oscillations that were harmonics of the semi-diurnal tide. Two hydrostatic estuarine models were applied to the Gareloch: a 2D vertical model (SLICE) and a 3D model (ECOMSED). Both models were capable of reproducing the observed (2005) baroclinic circulation at the M2 time scale but failed to simulate the higher frequency, non-linear oscillations. However, each model generated higher harmonics in idealised scenarios. Because lateral motion was negligible and SLICE was an order of magnitude more efficient than ECOMSED, the 2D model was used to simulate the higher harmonics and showed that their generation was attributed to the non-linear distortion of the internal tide. When the internal Froude number (determined by barotropic velocity, stratification and water depth) was increased from a sub-critical value, non-linear advection became more important and higher harmonics were generated. The internal tide was further modified by wave reflection and interaction off steep boundaries, and by flow over the sill.  相似文献   

15.
To investigate organic matter source and reactivity in the Zhujiang River (Pearl River)Estuary and its adjacent areas, particulate organic carbon (POC), particulate hydrolysable amino acids (PHAA), and Chl a during two cruises in July 1999 and July 2000 were measured. The highest POC and PHAA concentration was observed in the waters with maximum Chl a. The spectra distribution,relative content (dry weight in milligram per gram), PHAA-C% POC and other indicators such as the ratios of amino acids vs. amino sugars (AA/AS) and glucosamine vs. galactosamine (Glum/Gal) suggested that particulate amino acids in the water column and sediments in the Zhujiang River Estuary were mainly derived from biogenic processes rather than transported from terrestrial erosion. In inner estuary where high turbidity was often observable, organic matter was mainly contributed by re-suspension of bottom sediments with revealed zooplankton, microbial reworked characteristics, which suggest that these organic matters were relatively “old“. In the estuarine brackish region, organic matter in water column is mainly contributed by relatively fresh, easily degradable phytoplankton derived organic matter.During physical - biological processes within the eastuary, organic matter derived from phytoplankton was subjected to alteration by zooplankton grazing and bacterial reworking.  相似文献   

16.
Circulation in typical fjords is characterized by a shallow brackish layer at the surface over a deep long and narrow saltwater column. This surface layer is responsible for the outflow of water from the fjord and is important for flushing of the basin and water quality maintenance. The vertical structure of circulation and transport is known to be easily disrupted, and we postulate that the stability of fjordal circulation may also be vulnerable to impacts from anthropogenic alterations, such as floating structures, which could constrict the mixing and transport in the upper layers of the water column. First, using simplified fjord geometry and a three-dimensional finite volume coastal ocean model (FVCOM), a baseline examination of tidally averaged current profiles in basins with and without sills is presented. The response, varying from a partially mixed estuary regime to classical fjord conditions matches many fjord-like basins such as those in Puget Sound, Washington. The effect of surface obstruction on tidally averaged currents and residence times was then examined by incorporation of a narrow block in the surface layer of the model across the width of the simplified fjord channel such that normal velocity in the horizontal direction was forced to zero. This block approximated the presence of a floating bridge and was further tested using the geometry of Hood Canal, a fjordal sub-basin with a sill in Puget Sound. The results show that tidally averaged mean outflow under the influence of such a constraint at the water surface could be reduced significantly. In the case of Hood Canal, preliminary results indicate that the presence of the floating bridge might have increased the residence times in the basin by 8–13%, which could be an important factor affecting water quality.  相似文献   

17.
Water motion in estuarine waters is the result of the action of various dynamic factors. Firstly, based on the hydro-dynamic characteristics in estuarine waters, neglecting the nonlinear effects of various flow hydrodynamic factors, the logarithm velocity profile of tidal current and the cubic velocity profile of Hansen and Rattray (1965) made for linear superposition at a sense of first order, a new model for velocity profile in estuarine waters is established. Then, by introducing the least square method combination of enumeration, the velocity profile data of wind-driven current measured in the laboratory and that observed at the North and the South Branches of the Yangtze Estuary are verified and compared with other formulas, all with satisfactory results. The results show that the new model not only considers the influences of various dynamic factors, such as tide, wind force, run-off and density pressure with high accuracy, but also provides reasonable boundary conditions on the bottom for hydrodynamics numerical simulation in estuarine waters. Thereby, the accuracy and credibility of numerical computation and prediction of water flow are improved. The research is theoretically important for the estuarine hydrodynamics.  相似文献   

18.
Water column samples have been collected in the outer channel of the Ferrol Ria (NW Spain) during four occasions over a tidal cycle. The objective was to study the exchange of dissolved and particulate Cd, Cu, Pb and Zn and particulate Al, Fe and Si between the ria and the adjacent coastal waters. This study provides the first extensive dataset on dissolved and particulate metal concentrations in the water column of a Galician ria. Typical concentrations of dissolved Cd (96 ± 31 pM), Cu (8 ± 4 nM), Pb (270 ± 170 pM) and Zn (21 ± 10 nM) were similar than in other European Atlantic shelf and coastal waters. The fraction of metals in the particulate phase followed the trend: Pb > Cu Zn > Cd. The outgoing water from the ria was enriched in dissolved and particulate Cu, Pb and Zn compared with incoming waters, whereas Cd concentrations were similar for both waters. The suspended particulate matter was composed of a mixture of marine and continental material. The latter end-member was found to arise from the metal-rich ria bed sediments, which is diluted by the dominant metal-poor marine end-member. The net output flux of Cu from the channel is balanced by the freshwater inputs to the ria, and the net Zn flux gave a positive output to coastal waters. For Pb, the net flux to the coastal waters is less than that input from the rivers, as a result of its particle reactivity and deposition in sediments. On the contrary, a net input flux of dissolved Cd from coastal waters was observed, highlighting the oceanic source of this metal in the Galician rias. Results from the budget calculations are in agreement with the differential geochemical behavior of these elements in coastal waters.  相似文献   

19.
Mar Chiquita Coastal Lagoon is located on the Atlantic coast of Argentina, and it has been declared a Biosphere Reserve under the UNESCO Man and Biosphere Programme (MAB). This coastal lagoon constitutes an estuarine environment with a very particular behaviour and it is ecologically important due to its biological diversity. The aim of the present study was to evaluate the distribution and geochemical behaviour of several heavy metals in this coastal system, focusing on their distribution in both the dissolved phase (<0.45 μm) and the suspended particulate matter. Therefore, the general hydrochemical parameters (salinity, temperature, turbidity, pH and dissolved oxygen) and concentration of total particulate and dissolved metals (Cd, Cu, Ni, Zn, Fe, Pb, Cr and Mn) were measured along 2 years (2004–2006) at two different sites. As regards their distribution, hydrological parameters did not present any evidence of deviation with respect to historical values. Suspended particulate matter showed no seasonal variation or any relationship with the tide, thus indicating that in this shallow coastal lagoon neither tides nor freshwater sources regulate the particulate matter input. Heavy metals behaviour, both in dissolved and particulate phases did not reveal any relationship with tide or seasons. Mar Chiquita Coastal Lagoon showed a large input of dissolved and particulate metals, which is probably due to intensive agriculture within the drainage basin of this system.  相似文献   

20.
Copper concentrations have been measured in more than 200 samples collected from an Alaskan fjord and continental shelf and slope regions in the northwestern Gulf of Alaska. Concentrations were lowest (2·1 nmol kg−1) at depths of 400–1000 m in the continental slope waters of the Gulf of Alaska. Copper increased systematically with decreasing salinities shoreward to concentrations >30 nmol kg−1 in fjord surface waters during summer months of high freshwater runoff. Copper concentrations increased with depth at an inner fjord station where deep basin waters have restricted circulation, and these data together with surface (<5 cm) pore water copper concentrations (mean=122 nmol kg−1) about an order of magnitude higher than bottom water copper concentrations are indicative of a flux of copper across the sediment-seawater interface. This latter was estimated at 32±12 nmol cm−2 annually, and represented less than 20% of the annual input to fjord surface water (228–411 nmol cm−2) added during summer months. Mass balances in bottom waters indicate a vigorous recycling of copper with a residence time estimated at 21±11 days. Most copper that is remobilized in surface sediments is returned to bottom waters and little (3%) is removed by subsequent diagenetic reaction in the buried sediments. However, an estimate of copper accumulating in anoxic fjord sediments was comparable with copper added to fjord surface waters suggesting that input-removal reactions rather than internal cycling controls copper geochemistry in this estuary.  相似文献   

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