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1.
Suspended particle dynamics were investigated in the Ogeechee River Estuary during neap tide in July 1996. Samples were operationally separated into ‘ truly suspended ’ (settling velocity <0·006 cm s−1) and ‘ settleable ’ (settling velocity >0·006 cm s−1) fractions over the course of a tidal cycle to determine whether these two fractions were comprised of particles with differing biological and chemical characteristics. Total suspended sediment, organic carbon and nitrogen, chlorophyll a and phaeopigment concentrations were measured in each fraction, as well as rates of bacterial hydrolytic enzyme activity [β-1,4-glucosidase (βGase) and β-xylosidase (βXase)]. The majority of the suspended sediment (by weight) was in the truly suspended fraction; all measured parameters were largely associated with this fraction as well. When compared to the settleable material, the truly suspended material was significantly higher in % POC (5·7±0·6 vs. 3·9±1·8), % chlorophyll (0·07±0·02 vs. 0·03±0·01), % phaeopigment (0·030±0·006 vs. 0·018±0·012), and weight-specific maximal uptake rates (Vmaxper mg suspended sediment) of both enzymes (1·8±0·4 vs. 0·7± 0·2 nmol mg−1 h−1βGase and 1·1±0·3vs . 0·3±0·2 nmol mg−1 h−1βXase), providing clear evidence for a qualitative distinction between the two fractions. These results are interpreted to mean that the more organic-rich, biologically active material associated with the suspended fraction is likely to have a different fate in this Estuary, as ‘ truly suspended ’ sediments will be readily transported whereas ‘ settleable ’ sediments will settle and be resuspended with each tide. These types of qualitative differences should be incorporated into models of particle dynamics in estuaries.  相似文献   

2.
The interaction of selenium with mercury was studied in the shrimp Palaemon elegans. The release of 203HgCl2 (5·0 μg Hg per gramme body weight) from shrimp pretreated with selenium (SeO2 doses of 1·97, 3·95 and 7·90 μg Se per gramme fresh weight) was significantly decreased compared with the control group to which only 5·0 μg Hg/g had been administered.In the presence of HgCl2 (5·0 μg Hg per gramme fresh weight) the release of 75Se also diminished significantly at the higher stable Se pretreated dose (7·90 μg Se/g) while, at a lower selenium concentration, the release was not statistically different. Analyses for stable Hg and Se confirmed the decrease in rate of selenium loss in the presence of mercury which had been demonstrated with radiotracers.A dose of 7·9 μg Se per gramme fresh weight injected 12 h before exposure of the shrimp to the various mercuric chloride solutions did not produce a significant difference in the 24 h LC50 compared with the group not pretreated with selenium. However, during exposure to mercury at 3·8 mg/litre, the median lethal time (LT50) for the shrimp pretreated for 4 days with sublethal selenium (6·9 and 10·5 mg Se/litre) was delayed (19·2 and 33·2 h) compared with the group which was not pretreated. The results are discussed in relation to the role of selenium in the acutely toxic effects of inorganic mercury.  相似文献   

3.
The effect of ionic interactions on the kinetics of disproportionation of HO2, and the oxidation of Fe(II) and Cu(I) has been examined. The interactions of O2 with Mg2+ and Ca2+ ions in seawater increases the lifetime by 3–5 times compared to water. The effect of OH− on the oxidation of Fe(II) in water and seawater shows a second degree dependence from 5 to 45°C. The effect of salinity on the oxidation of Fe(II) was found to be independent of temperature, while the effect of temperature was found to be independent of salinity. The energy of activation for the overall rate constant was found to be 7 ± 0.5 kcal mol−1.The effect of pH, temperature, salinity and ionic composition on the oxidation of Cu(I) has also been examined. In NaCl solutions from 0.5 to 6 M, the log k for the oxidation was a linear function of pH (6–8) with a slope of 0.2 ± 0.05. The reaction was strongly dependent on the Cl− concentration with variation of from 0.3 to 340 min from 0.5 to 6 M Cl−. The rates of oxidation of Cu+ and CuCl0 responsible for these effects are dependent upon ionic strength. The energy of activation for the reaction was 8.5–9.9 kcal mol−1 from 0.5 to 6 M. Studies of the oxidation in various NaX salts (X = I−, Br− and Cl−) give rates in the order Cl− > Br− > I− as expected, due to complex formation of Cu+ with X−.  相似文献   

4.
Laboratory exposures of the urchin Lytechinus pictus to sediment dosed with varying concentrations of hydrogen sulfide (H2S), but without elevated organic material, were conducted. Changes in mortality, behavior, growth and gonad production were measured during 49 days' flow through exposures. Hydrogen sulfide concentrations of 165·8 μ liter−1 in pore water caused significant changes in all parameters measured. Concentrations as low as 32·9 μ liter−1 caused significant decreases in wet weight and male gonad production. A concentration of 91·8 μ liter−1 caused the mortality rate to increase 100-fold over control exposures (0·63 μ liter−1). Sublethal effects on growth and gonad production could have been caused by either direct biochemical inhibition by H2S or secondarily through behavioral modifications. Hydrogen sulfide concentrations above 165·8 μ liter−1 are common near sewage outfalls and could contribute to changes in species composition and sediment toxicity that occur there.  相似文献   

5.
Analyses of the concentration product (Ca2+) × (CO32−) in the pore waters of marine sediments have been used to estimate the apparent solubility products of sedimentary calcite (K′SPc) and aragonite (K′SPa) in seawater. Regression of the data gives the relation In K′PSPc = 1.94 × 10−3 δP − 14.59 The 2°C, 1 atm value of K′SPc is, then, 4.61 × 10−7 mol2 l−2. The pressure coefficient yields a at 2°C of −43.8 cm3 atm−1. A single station where aragonite is present in the sediments gives a value of K′SPa = 9.2 × 10−7 (4°C, 81 atm). The calcite data are very similar to those determined experimentally by Ingle et al. (1973) for K′SPc at 2°C and 1 atm. The calculated is also indistinguishable from the experimental results of Ingle (1975) if is assumed to be independent of pressure.  相似文献   

6.
Gross sedimentation rates (GSR) have been measured using sediment traps placed at nine different levels above the bed (0·3, 0·5, 0·8, 1·0, 2·0, 4·0, 6·0, 8·0 and 10·0 m). The sediment traps were deployed for 1·25 years and recovered 28 times during the study period. Low average GSR values of 5·5 g m-2 day-1 were obtained at 10·0 m, and high average GSR values of 114·8 g m-2 day-1 were obtained at 0·3 m. An expression for the eddy diffusion coefficient of suspended particulate matter (Ks), based on the measured GSR is given. The expression has been used for modelling of Ks at the different trap levels above the bed. High values (≈42 cm2 s-1) of Ks were obtained at the upper traps, whereas low values (≈2 cm2 s-1) were obtained near the bed. Comparison between level of turbulent energy in terms of shear stress at the boundaries of the water column, i.e. from the wind and the bed flow, showed that wind energy exceeded that of the bed flow by a factor 16. At 5·0 m Ks was positively correlated (r=0·66) to the eddy diffusion coefficient of momentum (Km) derived from the wind energy transfer to the water, giving an average β of 0·5 for Ks =βKm. The density difference between surface and bottom waters has been designated a parameter of stratification, and is discussed in relation to variations of Ks and Km .  相似文献   

7.
Midsummer (1 August) population estimates of about 2 million O-group plaice (Pleuronectes platessa L.) were derived for sandy bays around the Firth of Forth in 1979–1980. This is an order of magnitude less than similar estimates made for the Clyde Sea Area in 1973–1974. Autumn population estimates of 0·4–1·0 million fish were comparable to estimates by the Ministry of Agriculture, Fisheries and Food for the area between the Scottish border and Flamborough Head (2·3 million for 1970 and 1973) which represented 4·8% (1973) to 5·3% (1970) of the total number of O-group fish on the English east coast.Largo Bay was the most important nursery area holding 25% of the total population. It is particularly well situated to receive newly metamorphosed plaice carried in water currents along the north side of the Forth from the spawning ground off Fife Ness. Plaice in the Forth are mainly distributed on fine to medium sandy beaches (186–480 μm), the mean number per haul in midsummer (D) being correlated with the median diameter (m.d. in μm) of the low water sediments by the equation: D=−45·7666+0·2327 m.d. (n=11,r=0·68,P<0·02 but>0·01).The shallow inshore water in sandy bays in the outer Firth was well mixed and more marine than estuarine (27·7–35·0‰). The correlation coefficient between fish density and water temperature was low, while that with salinity (S‰) was: D=6·1618+0·2238S (n=23,r=0·62,P<0·005).Regression analysis demonstrated that the relationship between the instantaneous mortality rate (Z) and the initial population density (Dp) was: Z×100=0·7480+0·0546dp (n=12,r=0·87,P<0·001).The mean mortality rate for the O-group plaice in the Forth nursery areas was 53% month−1.  相似文献   

8.
Macroalgae biomass and concentrations of nitrogen, phosphorus and chlorophyll a were determined weekly or biweekly in water and sediments, during the spring-summer of 1985 in a hypertrophic area of the lagoon of Venice. Remarkable biomass production (up to 286 g m−2 day−1, wet weight), was interrupted during three periods of anoxia, when macroalgal decomposition (rate: up to 1000 g m−2 day−1) released extraordinary amounts of nutrients. Depending on the macroalgae distribution in the water column, the nutrients released in water varied from 3·3 to 19·1 μg-at litre−1 for total inorganic nitrogen and from 1·8 to 2·7 μg-at litre−1 for reactive phosphorus. Most nutrients, however, accumulated in the surficial sediment (up to 0·640 and to 3·06 mg g−1 for P and N respectively) redoubling the amounts already stored under aerobic conditions, Phytoplankton, systematically below 5 mg m−3 as Chl. a, sharply increased up to 100 mg m−3 only after the release of nutrients in water by anaerobic macroalgal decomposition. During the algal growth periods, the N:P atomic ratio in water decreased to 0·7, suggesting that nitrogen is a growth-limiting factor. This ratio for surficial sediment was between 6·6 and 13·1, similar to that of macroalgae (8·6–12·0).  相似文献   

9.
The effects of waterborne nitrite (3 mg/l NO2) on channel catfish were studied to evaluate changes in hematological parameters and phase I–II biotransformation in liver slices. Nitrite-exposed fish had significantly higher methemoglobin, blood and liver nitrite, and significantly lower pO2 than control fish. Total phase I-mediated metabolism of 7-ethoxycoumarin (EC) was not altered in nitrite-exposed fish compared with control fish (291±43 and 312±20 pmol/mg/h, respectively). However, phase II glucuronosyltransferase-mediated metabolism of 7-hydroxycoumarin (HC), both as a phase I metabolite of EC and as a parent substrate, was elevated in nitrite-exposed fish (204±17 and 1007±103 pmol/mg/h, respectively) as compared to control fish (149±14 and 735±87 pmol/mg/h) (P<0.05). Sulfotransferase-mediated metabolism of HC (as a metabolite of EC and as a parent substrate) was not notably altered in nitrite-exposed fish (95±16 and 617±33 pmol/mg protein/h, respectively) as compared with control fish (118±24 and 575±55 pmol/mg/h, respectively). These studies indicate that in vivo nitrite exposure and associated changes in hematological parameters do not appear to affect hepatic phase I EC biotransformation in channel catfish. However, subtle but significant changes in phase II glucuronidation, but not sulfation activity, were observed. The mechanism of these alterations is unclear. However, the data suggest that environmentally realistic concentrations of nitrite may affect the dynamics of conjugative metabolism in exposed fish.  相似文献   

10.
The apparent solubility product K′sp of calcite in seawater was measured as a function of temperature, salinity, and pressure using potentiometric saturometry techniques. The temperature effect was hardly discernible experimentally. The value of K′sp at 25°C was 4.59·10−7 mole2/(kg seawater)2 at 35‰S, 5.34·10−7 at 43‰S, and 3.24·10−7 at 27‰S. The apparent partial molal volume was found to be −34.4 cm3 at 25°C and −42.3 cm3 at 2°C from a linear fit of log(K′sp P/K′sp 1). These results were used in conjunction with field data to calculate the degree of saturation in the oceans and showed undersaturation at shallower depths than previously reported.  相似文献   

11.
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12.
In May and September 1999 11 stations were sampled in the southern and central North Sea, located in the German Bight, eastern Oyster Ground and Dogger Bank. The study focused on the influence of particle mixing on transport of chlorophyll a to deeper sediment layers and vertical bacterial distribution (max. DEPTH=10 cm). The sampling stations were chosen to reflect a gradient in environmental conditions in the North Sea. The sampling stations differed in respect to redox potential (eH up to −243 mV in the German Bight and up to 274 mV in the offshore regions), silt content (up to 54% in the German Bight and 0·34% at the northern Dogger Bank) and different proportion of fresh organic material on total organic matter content (C/N ratios ranging from 9·27 in the German Bight up to 1·72 in the offshore sediments). Although bacterial densities (8·55×109 g−1in the German Bight up to 0·35×109 g−1in offshore sediments) were significantly correlated to chlorophyll a content in the sediment (P<0·01), inconsistencies in the temporal pattern of both variables in the surficial sediment layer suggested, that the dynamics of bacterial densities is generally controlled by food supply but also by other variables. The chlorophyll a content in the surficial sediments of the German Bight (up to 1·84 μg g−1) was significantly higher than in the Oyster Ground (up to 0·58 μg g−1) and the Dogger Bank area (up to 0·68 μg g−1). With increasing chlorophyll a input to the benthic realm a subsequent enhanced burial of this compound into deeper sediment layers was expected either by biological (bioturbation) or by physical sediment mixing. However, the vertical profile of chlorophyll a decreased steeply in the sediments of the German Bight. Contrary, subsurface peaks were measured in the offshore areas. It was concluded from these results, that the vertical distribution of organic matter in sediments is less limited by the quantitative input from the water column but concomitant with particle mixing itself. The extent and possible mechanisms of particle mixing in the different study areas in relation to specific environmental factors is discussed.  相似文献   

13.
A worldwide literature survey of data on cadmium concentration in the soft tissue of the mussel, Mytilus spp., from 591 stations is presented. These stations are from 13 regions. Geometric means for the regions vary from 0·6 to 3·3 μg g−1 (dry weight) for the Barents Sea and the Northeastern Pacific coast, respectively.The averages of seven of these regions, for which reliable cadmium concentrations in seawater were available, were used to calculate a relationship between cadmium concentrations in seawater and mussel soft tissue. The relationship was highly significant: (Cd) mussel (μg g−1, dry weight) = 0·074 (Cd) water (ng litre−1) + 0·39 (P ≤ 0·0005).This model has been successfully applied in the context of the contamination of the Gironde estuary (France). It can also be used to define a water quality criterion for mussel maturing parks consistent with the quality criterion defined for shellfish for human consumption.  相似文献   

14.
The effect of cadmium was determined on some oxygen-binding characteristics (viz. oxygen affinity, subunit cooperativity, Bohr-effect and temperature effect) of the erythrocruorin of the lugworm, Arenicola marina.Oxygen affinity and subunit cooperativity were measured directly in the blood of Arenicola, both in blood collected from specimens kept under experimental conditions and from specimens obtained from their natural habitat.In the pH range of 7·3–7·8, which closely resembles in vivo blood pH values, cadmium does not affect the oxygen affinity at low concentrations (10−8-10−5 ), and decreases the O2-affinity only slightly at higher concentrations (10−5-2·10−3 ). In the more alkaline pH range, the oxygen affinity increases considerably with increasing cadmium concentrations.Cadmium exerts a facilitating influence on the haem cooperativity at lowest concentrations (10−8-10−7 ) and a minor inhibiting influence at higher concentrations.The oxygen affinity, subunit cooperativity, the Bohr-effect and the temperature effect are pH dependent.The influence of cadmium on the magnitude of the Bohr-effect is pH-dependent.In vivo measurement of the oxygen affinity of Arenicola erythrocruorin gives evidence of a more pronounced inhibition of oxygen binding at increasing cadmium concentrations in the blood, compared with the effect on purified erythrocruorin solutions.  相似文献   

15.
Surface water samples were collected in the north Atlantic Ocean in July–August 1983. Their apparent complexation capacity for copper (CCCu) was determined on board, using differential pulse anodic stripping voltammetry under clean room conditions. Measurements were carried out by direct titrations as well as after equilibration of copper spikes. CCCu and conditional stability constants (K′) were calculated, by means of three different methods, which are compared.On the basis of salinity, temperature, silicate and phosphate concentrations the following surface waters could be distinguished: North Atlantic Drift (I), East Greenland Current (II), Labrador Current (III) and Gulf Stream waters (IV, V). CCCu and K′ were found to differ between these waters. The range of values for CCCu and their mean values given in parentheses, as calculated from van den Berg plots for waters I–IV are: I, 53–65 (59); II, 47–66 (55); III, 37–53 (45); IV, 20–42 (33) nM Cu. The range and mean values for log K′ are: I, 8.23–8.33 (8.28); II, 7.89–8.11 (7.98); III, 8.40–8.41 (8.41); IV, 7.90–8.21 (8.06).Information on complexation kinetics extracted from the titration curve revealed that kf′ is area-specific. The complexation rate constant in the northern part (Area I) is about two times larger than that in the southern area IV, (3.6 ± 0.3) and (2.2 ± 0.2) × 104s−1M−1 Cu, respectively.Preliminary results for deep water samples suggest smaller but still existent CCCu and higher K′ than those found for surface waters.  相似文献   

16.
Uptake of inorganic carbon and ammonium by the plankton community of three North Carolina estuaries was measured using 14C and 15N isotope methods. At 0% light, C appeared to be lost via respiration, and at increasing light levels uptake of inorganic carbon increased linearly, saturated (mean Ik = 358±30 μEin m−2 s−1), and frequently showed inhibition at the highest light intensities. At 0% light NH4+ uptake was significantly greater than zero and was frequently equivalent to uptake in the light (light independent); at increasing light levels NH4+ uptake saturated (mean Ik = 172±44 μEin m−2 s−1) and frequently indicated strong inhibition. Light-saturated uptake rates of inorganic carbon and NH4+ were a function of chlorophyll a (r2 = 0·7−0·9); average assimilation numbers were 625 nmol CO2 (μg chl. a)−1 h−1 and 12·9 nmol NH4+ (μg chl. a)−1 h−1 and were positively correlated with temperature (r2 = 0·3−0·7). The ratio of dark to light-saturated NH4+ uptake tended to be near 1·0 for large algal populations at low NH4+ concentrations, indicating near light independence of uptake; whereas the ratio was lower for the opposite conditions. These data are interpreted as indicative of nitrogen stress, and it is suggested that uptake of NH4+ deep in the euphotic zone and at night are mechanisms for balancing the C:N of cellular pools. A 24-h study using summed short-term incubations confirmed this; the cumulative C:N of CO2 and NH4+ uptake during the daylight period was 10–20, whereas over the 24-h period the ratio was 6 due to dark NH4+ uptake. Annual carbon and nitrogen primary productivity were respectively estimated as 24 and 4·0 mol m−2 year−1 for the South River estuary, 42 and 7·3 mol m−2 year−1 for the Neuse River estuary, and 9·6 and 1·6 mol m−2 year−1 for the Newport River estuary.  相似文献   

17.
The Haustorius canadensis population at Long Sands beach in southern Maine was studied over a period of 45 months. The length-weight relationship was examined over 24 months; it showed no difference due to either sex or month. Caloric content of the population displayed a seasonal cycle around a mean of 18·381 KJ gm−1 dry weight, peaking in mid to late summer. The increment summation, instantaneous growth, removal summation and size-frequency methods of calculating production were used and the results compared. The increment summation and instantaneous growth methods provided the best estimates of production, averaging 98·1 gm m−1 y−1 and 100·2 gm m−1 y−1, respectively. The annual production to mean biomass ratio averaged 1·48. The population exhibited strong peaks of production; the four summer months accounting for 4·65 times the production during the remainder of the year. Most of the production was due to one-year-old individuals.  相似文献   

18.
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   

19.
Sediment samples were collected at stations along cross-shelf transects in Onslow Bay, North Carolina, during two cruises in 1984 and 1985. Station depths ranged from 11 to 285 m. Sediment chlorophyll a concentrations ranged from 0·06 to 1·87 μg g−1 sediment (mean, 0·55), or 2·6–62·0 mg m2. Areal sediment chlorophyll a exceeded water column chlorophyll a a at 16 of 17 stations, especially at inshore and mid-shelf stations. Sediment ATP concentrations ranged from 0 to 0·67 μg g−1 sediment (mean, 0·28). Values for both biomass indicators were lowest in the depth range including the shelf break (50–99 m). Organic carbon contents of the sediments were uniformly low across the shelf, averaging 0·159% by weight. Photography of the sediments revealed extensive patches of microalgae on the sediment surface.Our data suggest that viable benthic microalgae occur across the North Carolina continental shelf. The distribution of benthic macroflora on the North Carolina shelf indicates that sufficient light and nutrients are available to support primary production out to the shelf break. Frequent storm-induced perturbations do not favour settling of phytoplankton, an alternative explanation for the presence of microalgal pigments in the sediments. Therefore, we propose that a distinct, productive benthic microflora exists across the North Carolina continental shelf.  相似文献   

20.
Upogebia deltaura was collected quantitatively and qualitatively between June 1980 and August 1982 from a level, sandy bottom at a 12 m depth in the archipelago of Lysekil (on Gullmarsfjorden) about 70 km north of Göteborg, in western Sweden. A total of 347 individuals were obtained. The deepest burrows reached a depth of more than 65 cm into the substrate. During the cold season, U. deltaura was situated much deeper in the substrate than it was during the summer, probably as a result of ‘hibernation’. The average density was 5·0 individuals 0·1 m−2, and the maximum of 10 specimens was found in one 0·1 m2 sample. Out of the 341 individuals identifiable as to sex, 186 (54·6%) were females and 155 (45·4%) were males. Berried females were found between May and August, and the average number of eggs carried was 4757. Ecdysis took place between May and August; most females moulted in the middle of June and most males about one month later, in mid July. The chelipeds of large males were proportionally bigger than were those of large females. Maximum total body length of the females was 65·7 mm, and that of the males was 65·3 mm.  相似文献   

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