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1.
The effects of prolonged exposure to reduced oxygen levels (3.0 and 1.5 mg O2 l−1) on marine scavenging gastropods Nassarius festivus were studied for 8 weeks. The percentages of individuals engaged in feeding and amount of food consumed were reduced as oxygen level decreased; absorption efficiency, however, did not vary significantly with oxygen level. Oxygen consumption rates and specific oxygen consumption rates were lower at reduced oxygen levels. Reproduction occurred at all oxygen levels with less egg capsules being produced at lower oxygen levels. Egg size and number of eggs per capsule, however, were not significantly affected by oxygen level. The increase in shell length was 12%, 6% and 5% at 6.0 mg O2 l−1 (normoxia), 3.0 mg O2 l−1 and 1.5 mg O2 l−1, respectively. At the end of the experiment, the amount of energy allocated to growth and reproduction decreased at reduced oxygen levels with values obtained at 3.0 mg O2 l−1 and 1.5 mg O2 l−1 being 48% and 70% lower than those at 6.0 mg O2 l−1. At all oxygen levels, most of the accumulated energy was allocated to shell growth and reproduction, and the amount allocated to somatic growth was relatively insignificant. The reduction in energy allocated to reproduction was greater than that to shell growth as the oxygen level was reduced, indicating a strategic energy allocation of marine scavengers under stressful conditions to enhance survival.  相似文献   

2.
Since it is often difficult to estimate possible adverse effects due to contamination in selected ecosystems, multi-species biomonitoring may provide more information, taking into account different routes of exposure, ecological roles and metabolic capabilities of animals. In this context, we exposed for 7 days the mussel Mytilus galloprovincialis and the crab Carcinus aestuarii to 4-nonylphenol (NP), a well-known xenoestrogen. In mussels (0–0.2 mg NP l−1), we measured NP bioaccumulation in soft tissues and vitellogenin (Vg)-like protein levels in digestive glands from both males and females by the alkali-labile phosphate assay (ALP). As no reference data were available for crab exposure, the NP 96-h LC50 value was previously determined. Then, in sublethally exposed (0–1.0 mg NP l−1) male crabs, NP bioaccumulation and Vg levels were measured in hemolymph, gonads and digestive gland. Bioaccumulation of NP increased from 43 to 371 μg g−1 d.w. in mussels, and from 3.6 to 37 μg g−1 d.w. in crabs, depending on the NP concentration in water. Dose-dependent Vg-like protein induction was observed in both species, appearing to be related to NP bioaccumulation, although a partial decrease was recorded at the highest concentration tested. A similar trend was observed in both digestive gland and gonad of exposed crabs; Vg increased to a lesser extent, although significantly, in hemolymph. Results demonstrated that NP induces Vg synthesis both in male and female mussels, as well as in male crabs. On the basis of the responsiveness of both species investigated, a multi-species approach is indicated in biomonitoring programmes.  相似文献   

3.
The effects of Cu, Cd, Zn and Cr on the survival and feeding behaviour of the sandy shore scavenging gastropod Nassarius festivus were compared. The 96-h LC50 for Cu, Cd, Zn and Cr were 0.36, 1.52, 1.76 and 36.9 mg l−1, respectively. Four sublethal concentrations of each metal plus a control were prepared and the snails were exposed to experimental solutions for 96 h. Feeding behaviour was studied after the snails were starved for five days. As compared with the control, the number of individuals feeding was significantly reduced by exposure to 0.05 mg l−1 Cu, 0.2 mg l−1 Zn, 0.5 mg l−1 Cd and 5 mg l−1 Cr. The time spent feeding was greater for individuals exposed to greater concentrations of Zn and Cd but no effect was found for Cu and Cr. Chemoreception of food was studied by placing the snails at a fixed distance of 15 cm from the bait. The success rate of reaching the bait was less for individuals exposed to Cr but no effect was found for Zn, Cu or Cd. The time required for an individual to reach the bait decreased as the concentration of Zn increased. In contrast, a longer time was required for individuals exposed to Cr whereas the effect of Cd and Cu was insignificant. The potential of using feeding behaviour and chemoreception in contaminant evaluations is discussed.  相似文献   

4.
Distribution, abundance and life history characteristics of Mysis relicta were studied in the Feldberg Lake District (Lake Breiter Luzin, Lake Schmaler Luzin, Lake Zansen) located in northeastern Germany. Between July 2001 and November 2002 mysids were collected by vertical net hauls. In order to determine the impact of the current trophic conditions on the distribution of mysids in these lakes, oxygen concentration, total phosphorus, chlorophyll a and water transparency were also measured. All investigated lakes are mesotrophic at present. Lake Breiter Luzin exhibited great seasonal and spatial variations in mysid abundance. Density of adults and juveniles had a mean of 44.9 ± 57.1 and 68.7 ± 99.6 m−2, respectively. Highest abundance of adults was 110.4 ± 76.5 m−2 in summer, lowest abundances of 2.0 ± 4.0 m−2 occurred in spring. For juveniles, highest density of 218.4 ± 174.6 m−2 was detected in summer and lowest of 0.8 ± 1.8 m−2 in winter. No mysids were caught in any of the daytime hauls, but they were widely distributed throughout the water column at night. Size frequency distribution of mysids suggested that reproduction occurred year-round, the most consistent influx of juveniles occurred in early summer and a smaller second cohort in autumn. Highest mysid abundance was 189.2 ± 318.6 adults and 127.0 ± 66.3 juveniles m−2 in Lake Schmaler Luzin, and 59.6 ± 5.6 adults and 79.4 ± 11.2 juveniles m−2 in Lake Zansen. There were great spatial differences in abundance in both lakes.  相似文献   

5.
The effects of salinity, temperature, and light conditions on the reproduction and development of harpacticoid copepod, Nitocra affinis f. californica under controlled laboratory conditions were determined. Seven different salinity levels (5, 10, 15, 20, 25, 30, 35 ppt), four temperatures (20, 25, 30, 35 °C), three different light intensities (25, 56, 130 μmol m−2 s−1) and photoperiods (24 h:0 h, 1 h:23 h, 12 h:12 h LD cycle) were employed in this study. The highest (p < 0.05) overall reproduction and fastest development time were achieved by copepods reared under 30–35 ppt salinity. The optimum temperature required for the maximum reproduction was 30 °C while under 30 °C and 35 °C the copepod development time was shortest (p < 0.05) compared to other temperature levels. The overall reproduction was highest (p < 0.05) and development rate of N. affinis was shortest (p < 0.05) under lowest light intensity (25 μmol m−2 s−1). Continuous light (24 h:0 h LD) inhibited the egg production while, continuous darkness (1 h:23 h LD) and 12 h:12 h LD significantly favoured the overall reproductive activity of the female. Photoperiods 1 h:23 h and 12 h:12 h LD yielded highest total (p < 0.05) offspring female−1 coupled with highest (p < 0.05) survival percentage. This study illustrated that although N. affinis can tolerate wide range of environmental conditions, prolonged exposure to subnormal environments affect its reproduction and development. This study showed that this species can be mass cultured for commercial purposes and has a potential to be used for toxicity studies due to its high reproductive performance fast development and a wide range of tolerance to environmental conditions.  相似文献   

6.
We performed a field experiment in a tropical humic coastal lagoon to evaluate periphyton biomass accrual and metabolism on three different substrates (1) plastic ribbons, (2) green and (3) senescent leaves of the emergent macrophyte Typha domingensis) over 30 days. The contribution of autotrophic biomass decreased as total biomass increased over the time. Mean periphytic ash free dry weight ranged from 0.8 to 5.6 mg cm−2, but periphyton chlorophyll a concentrations presented shorter amplitudes, which oscillated from 0.12 to 0.44 μg cm−2 throughout the experiment. Periphyton metabolism was overall heterotrophic on all substrates, especially on senescent leaves. Our data show that substrate type influenced both biomass accrual and periphyton net productivity and respiration rates throughout periphyton development and highlighted the dominance of heterotrophic metabolism. The periphyton respiration may be subsidized by both water- and substrate-derived allochthonous energy pathways, shedding light on the role of periphytic assemblages to the carbon cycling, as a source of CO2 to the system.  相似文献   

7.
In the eustigmatophycean Nannochloropsis limnetica the content of polyunsaturated fatty acids (PUFA) is extremely high in comparison to different planktonic green algal taxa in freshwater ecosystems. The sums of n-6 and n-3 fatty acids in N. limnetica were ten-fold higher than in the other picoplankton Choricystis minor and Pseudodictyosphaerium jurisii, and higher than in the nanoplanktonic green algae Chlorella vulgaris, Monoraphidium neglectum and Scenedesmus obtusiusculus. The content of fatty acids in N. limnetica was highly variable under different culture conditions. The highest concentrations of PUFA in N. limnetica were found in non-aerated suspension cultures, with a high content of phosphate (40 mg l−1 K2HPO4) in the culture medium: linoleic acid 22.19 mg g−1 DW, arachidonic acid 10.52 mg g−1 DW, and eicosapentaenoic acid 55.56 mg g−1 DW. N. limnetica represent a high-quality food resource in freshwater food chains. Furthermore, cultures of this eustigmatophycean alga have a high potential for use in biotechnology and aquaculture.  相似文献   

8.
Specimens of Nassarius nitidus were collected in seven stations of the Venice Lagoon to assess the levels of tributyltin (TBT) and its metabolites monobutyltin and dibutyltin in the tissues and monitor their effect on organisms, in particular the phenomenon of imposex (superimposition of male sexual characteristics on females). The following values of population indices were found: vas deferens sequence: 1.2 ± 0.7–4.0 ± 0.5; relative penis length: 6–47%. The least impacted station was situated in the northern part of the Lagoon, where females without imposex were found and Butyltin (BuTs) concentrations in the organisms (average sum of BuTs = 43 ± 14 ng Sn g−1 w.) were significantly lower than in the other stations (range of average sum of BuTs: 101 ± 22–217 ± 27 ng Sn g−1 d.w.). Population indices were found to be related to the TBT content in the tissues. In particular VDSI had a significant logarithmic correlation: r = 0.95, n = 8, p < 0.05.  相似文献   

9.
We investigated the response of phytoplankton and zooplankton to experimental alteration of nitrate and phosphate levels in outdoor enclosures. Experiments were conducted in summer and winter and in the absence and presence of a layer of soil. The tubs (12 in all) except the two plain water controls were manured initially with a mixture of fresh cowdung (50g 1−1), mustard oil cake (25 g l−1) and poultry wastes (25 g l−1; mostly excreta), prior to enrichment. Water samples were collected from the experimental tubs twice a week to measure selected physico-chemical and biological variables. Water temperature in the summer experiments ranged from 20–30 °C and during the winter experiments from 11–15 °C. The pH values ranged from 8.0 to 9.5 and the dissolved oxygen levels from 8.2–10.0 mg l−1. The levels of soluble reactive phosphorus and nitrate nitrogen ranged from undetectable levels to 1800 μg l−1 and 6000 μg l−1, respectively. The increase in chlorophyll-a following enrichment was rapid (3–7 days) during summer, but slower in winter (7–14 days). The predominant phytoplankton species observed in the tubs belong to the genera Sphaerocystis, Chlorella, Scenedesmus, Cosmarium, Ulothrix, Zygnema, Gonium and Pandorina. The rotifer species observed were Brachionus calyciflorus, Rotaria neptunia, Lecane bulla, L. luna, L. unguitata, Euchlanis dilatata, Asplanchna intermedia, Pseudoharringia spp., Eosphora spp., Lepadella ovalis, Epiphanes brachionus, Hexarthra mira and Cephalodella gibba. The cladocerans observed were Macrothrix spp. and Alona spp.  相似文献   

10.
Oxygen self diffusion rates were determined in quartz samples exchanged with18O-enriched CO2 between 745 and 900°C and various pressures, and the diffusion profiles were measured using an ion microprobe. The activation energy (Q) and preexponential factor (D0) at P(CO2) = P(tot) = 100 bar, for diffusion parallel to the c-axis are 159 ( ± 13) kJ/g atom and 2.10 (+0.75/ −0.55) × 10−8 cm2/s. This rate is approximately 100 times slower than that obtained from hydrothermal experiments and 100 times faster than a previous 1-bar quartz-O2 exchange experiment. The oxygen diffusion rate measured at 0.6 bar, 888°C, and at 900°C in vacuum is in agreement with the previous 1-bar exchange experiments with18O2. The effect of higher CO2 pressures is small. At 900°C, the diffusion rate exchanged with CO2 is = 2.35 × 10−15 cm2/s at 100 bar, 2.24 × 10−15 cm2/s at 3.45 kbar and 8.13 × 10−15 cm2/s at 7.2 kbar.There is probably a diffusing species, other than oxygen, that enhances the oxygen diffusion rate in these quartz-CO2 systems, relative to that occurring at very low pressures or in a vacuum. The effect of this diffusing species, however, is not as strong as that associated with H2O. Preserved oxygen isotope fractionations between coexisting minerals in a slowly cooled, high-grade metamorphic terrane will vary depending upon whether a water-rich phase was present or not. Closure temperatures will be approximately 100°C higher in rocks where no water-rich phase was present during cooling. The measured fractionations between coexisting minerals in metamorphic rocks may potentially be used as a sensor of water presence during retrogression.  相似文献   

11.
We examined the effects of freshwater flow and light availability on phytoplankton biomass and production along the Louisiana continental shelf in the region characterized by persistent spring–summer stratification and widespread summer hypoxia. Data were collected on 7 cruises from 2005 to 2007, and spatially-averaged estimates of phytoplankton and light variables were calculated for the study area using Voronoi polygon normalization. Shelf-wide phytoplankton production ranged from 0.47 to 1.75 mg C m−2 d−1 across the 7 cruises. Shelf-wide average light attenuation (kd) ranged from 0.19–1.01 m−1 and strongly covaried with freshwater discharge from the Mississippi and Atchafalaya Rivers (R2=0.67). Interestingly, we observed that the euphotic zone (as defined by the 1% light depth) extended well below the pycnocline and to the bottom across much of the shelf. Shelf-wide average chlorophyll a (chl a) concentrations ranged from 1.4 to 5.9 mg m−3 and, similar to kd, covaried with river discharge (R2=0.83). Also, chl a concentrations were significantly higher in plume versus non-plume regions of the shelf. When integrated through the water-column, shelf-wide average chl a ranged from 26.3 to 47.6 mg m−2, but did not covary with river discharge, nor were plume versus non-plume averages statistically different. The high integrated chl a in the non-plume waters resulted from frequent sub-pycnocline chl a maxima. Phytoplankton production rates were highest in the vicinity of the Mississippi River bird's foot delta, but as with integrated chl a were not statistically different in plume versus non-plume waters across the rest of the shelf. Based on the vertical distribution of light and chl a, a substantial fraction of phytoplankton production occurred below the pycnocline, averaging from 25% to 50% among cruises. These results suggest that freshwater and nutrient inputs regulate shelf-wide kd and, consequently, the vertical distribution of primary production. The substantial below-pycnocline primary production we observed has not been previously quantified for this region, but has important implications about the formation and persistence of hypoxia on the Louisiana continental shelf.  相似文献   

12.
Surface partial pressure of CO2 (pCO2), temperature, salinity, nutrients, and chlorophyll a were measured in the East China Sea (ECS; 31°30′–34°00′N to 124°00′–127°30′E) in August 2003 (summer), May 2004 (spring), October 2004 (early fall), and November 2005 (fall). The warm and saline Tsushima Warm Current was observed in the eastern part of the survey area during four cruises, and relatively low salinity waters due to outflow from the Changjiang (Yangtze River) were observed over the western part of the survey area. Surface pCO2 ranged from 236 to 445 μatm in spring and summer, and from 326 to 517 μatm in fall. Large pCO2 (values >400 μatm) occurred in the western part of the study area in spring and fall, and in the eastern part in summer. A positive linear correlation existed between surface pCO2 and temperature in the eastern part of the study area, where the Tsushima Warm Current dominates; this correlation suggests that temperature is the major factor controlling surface pCO2 distribution in that area. In the western part of the study area, however, the main controlling factor is different and seasonally complex. There is large transport in this region of Changjiang Diluted Water in summer, causing low salinity and low pCO2 values. The relationship between surface pCO2 and water stability suggests that the amount of mixing and/or upwelling of CO2-rich water might be the important process controlling surface pCO2 levels during spring and fall in this shallow region. Sea–air CO2 flux, based on the application of a Wanninkhof [1992. Relationship between wind speed and gas exchange over the ocean. Journal of Geophysical Research 97, 7373–7382] formula for gas transfer velocity and a set of monthly averaged satellite wind data, were −5.04±1.59, −2.52±1.81, 1.71±2.87, and 0.39±0.18 mmol m−2 d−1 in spring, summer, early fall, and fall, respectively, in the northern ECS. The ocean in this study area is therefore a carbon sink in spring and summer, but a weak source or in equilibrium with the atmosphere in fall. If the winter flux value is assumed to have been the mean of autumnal and vernal values, then the northern ECS absorbs about 0.013 Pg C annually. That result suggests that the northern ECS is a net sink for atmospheric CO2, a result consistent with previous studies.  相似文献   

13.
Commercial antifouling formulations containing TBT are the major source of organotin contamination in coastal waters. In view of the persisting TBT residues (13 ng Sn l−1) in the coastal waters of South Korea, an attempt has been made to evaluate the growth response and biochemical composition of laboratory-cultured Nannochloropsis oculata to TBT toxicity. It is evident that the persisting concentration level of TBT is high enough to cause adverse effect on the microalgal species. The EC50 (24 h) was found to be at 0.89 nM level of TBT for this marine eustigmatophyte N. oculata. Photosynthetic pigment content was significantly affected. At elevated TBT concentrations of 1.0 nM, especially pronounced changes in biochemical composition was found. TBT tolerance of N. oculata and its growth as well as biochemical responses are discussed.  相似文献   

14.
Sulfur isotope effects during the SO2 disproportionation reaction to form elemental sulfur (3SO2+3H2O→2HSO4−+S+2H+) at 200–330°C and saturated water vapor pressures were experimentally determined. Initially, a large kinetic isotopic fractionation takes place between HSO4− and S, followed by a slow approach to equilibrium. The equilibrium fractionation factors, estimated from the longest run results, are expressed by 1000 ln αHSO4−–S=6.21×106/T2+3.62. The rates at which the initial kinetic fractionation factors approach the equilibrium ones were evaluated at the experimental conditions.δ34S values of HSO4− and elemental sulfur were examined for active crater lakes including Noboribetsu and Niseko, (Hokkaido, Japan), Khloridnoe, Bannoe and Maly Semiachik (Kamchatka), Poás (Costa Rica), Ruapehu (New Zealand) and Kawah Ijen and Keli Mutu (Indonesia). ΔHSO4−–S values are 28‰ for Keli Mutu, 26‰ for Kawah Ijen, 24‰ for Ruapehu, 23‰ for Poás, 22‰ for Maly Semiachik, 21‰ for Yugama, 13‰ for Bannoe, 9‰ for Niseko, 4‰ for Khloridonoe, and 0‰ for Noboribetsu, in the decreasing order. The SO2 disproportionation reaction in the magmatic hydrothermal system below crater lakes where magmatic gases condense is responsible for high ΔHSO4−–S values, whereas contribution of HSO4− produced through bacterial oxidation of reduced sulfur becomes progressively dominant for lakes with lower ΔHSO4−–S values. Currently, Noboribetsu crater lake contains no HSO4− of magmatic origin. A 40-year period observation of δ34SHSO4− and δ34SS values at Yugama indicated that the isotopic variations reflect changes in the supply rate of SO2 to the magmatic hydrothermal system. This implies a possibility of volcano monitoring by continuous observation of δ34SHSO4− values. The δ18O values of HSO4− and lake water from the studied lakes covary, indicating oxygen isotopic equilibration between them. The covariance gives strong evidence that lake water circulates through the sublimnic zone at temperatures of 140±30°C.  相似文献   

15.
Garnets in an amphibolite-facies metasediment from Sulitjelma, North Norway yield precise and concordant SmNd, UPb and RbSr ages that relate directly to the pressure (P) and temperature (T) conditions of mineral growth. Differential mineral reaction between graphitic and non-graphitic layers within this sample preserves a record of theP-T and time (t) history experienced during Barrovian regional metamorphism. Garnets in graphitic layers grew during prograde metamorphism at462 ± 16°C and5.2 ± 0.5 kbar under conditions of lowaH2O, and yield indistinguishable147Sm143Nd and238U206Pb ages of434.1 ± 1.2 Ma and433.9 ± 1.0 Ma, respectively. In contrast, garnet growth in adjacent graphite-free layers did not occur untilP-T conditions of540 ± 18°C and8.0 ± 1.0 kbar were attained, with continued growth in response to minor heating and decompression with final matrix equilibration at544 ± 16°C and7.0 ± 1.0 kbar. The inclusion-free garnet rims in this assemblage record indistinguishable147Sm143Nd and238U206Pb ages of424.6 ± 1.2 Ma and423.4± 1.7 Ma, respectively. These results provide precise estimates for average heating and burial rates during prograde metamorphism of 8.6−4.4+7.5°C Ma−1 and 0.8−0.5+0.9 km Ma−1, respectively. Rb and Sr exchange between coexisting silicates in the graphite-free assemblage continued for some 37 Ma after the “peak” of metamorphism, and require an average cooling rate of about 4.0°C Ma−1 during uplift. These results illustrate a clear relationship between reaction history and the timing of mineral growth and provide definitive constraints on the rates of thermal and tectonic processes accompanying regional metamorphism.  相似文献   

16.
This in situ study used photosynthetic activity (measured as chlorophyll a fluorescence) and photosynthetic pigment concentrations to assess the effect of copper, cadmium, lead and zinc on the seagrass Zostera capricorni. Custom-made portable in situ exposure (PIE) chambers were developed so seagrasses could be dosed within the meadow. Z. capricorni was exposed to 0.1 and 1 mg l−1 of metal solutions for 10 h. During this time and for the subsequent four-day recovery period, the effective quantum yield of photosystem II (PS II) (ΔF/Fm′) was measured. While the results were variable, copper and zinc exposed samples had a depressed ΔF/Fm′ during the exposure period. Samples exposed to zinc recovered to pre-exposure levels but those exposed to copper did not. Cadmium and lead did not impact on the chlorophyll a fluorescence and the chlorophyll pigment data supported these findings. This study presents an innovative new application of chlorophyll a fluorescence stress assessment.  相似文献   

17.
Here we present the first species-specific study of boron isotopes in the epibenthic foraminifer species Cibicidoides wuellerstorfi. Coretop samples from a water depth profile from 1000 to 4500 m on the northern flank of the Walvis Ridge are 4.4‰ lower than the values expected, based on calculations of the δ11Bborate of ambient seawater. Similar values for this foraminifer species are presented from ODP site 668B at the Sierra Leone Rise, in the equatorial Atlantic. The consistency between data of the same species suggests the offsets are primary, rather than diagenetic. Glacial C. wuellerstorfi from ODP 668B and Walvis Ridge have boron isotope compositions only slightly different to interglacial samples, that is no larger than + 0.10 pH units, or + 23 µmol kg− 1 in [CO32−] above the reconstructed glacial lysocline, and − 0.07 pH units, or − 14 µmol kg− 1 in [CO32−] below. We use these results to suggest that glacial deep water pH in the Atlantic was similar to interglacial pH. The new data resolve the inconsistency between the previously reported high bottom water pH and the lack of significant carbonate preservation of the glacial deep ocean.  相似文献   

18.
刘胜  陈宇炜 《湖泊科学》2017,29(6):1412-1420
于2014年10月到2015年5月鄱阳湖退水期,利用密闭箱—气相色谱法对鄱阳湖北部星子县洲滩两种代表性的植被群落——薹草(Carex cinerascens)和藜蒿(Artemisia selengensis)进行CO_2通量的对比观测,结果表明:薹草和藜蒿湿地的生态系统呼吸具有明显季节变化模式,其最小值均出现在冬季,最大值均出现在春季,平均值分别为3291.80和2581.89mg CO_2/(m~2·h),退水期薹草和藜蒿湿地累积的CO_2通量分别为213.71±2.27和176.39±11.48 t CO_2/hm~2.较高的生物量是薹草湿地CO_2通量高于藜蒿湿地的原因.5 cm土温是影响薹草和藜蒿湿地CO_2通量季节变化最重要的影响因子,藜蒿湿地生态系统呼吸的温度敏感性指数(Q10)高于薹草湿地.水分、植物生物量和湿地CO_2通量之间无显著相关性.  相似文献   

19.
Results are presented on scubadiving investigations carried out on thermal manifestations in the area of Panarea (Aeolian Islands). The area investigated falls inside a caldera which extends from the main island to the group of islets located to the northeast. The distribution of the gaseous manifestations is regulated by the NE-SW, NW-SE and N-S regional tectonic directrices, through which the more recent basic magma intruded, giving rise to dikes and pillow lavas. fO2-temperature relation of the gases sampled in the investigated area was calculated to be: logfO2 = 11−24,593/T which indicates that a buffering mechanism acted on the gases as they cooled down during their ascent. The high 3He/4He ratio (6 × 10−6) and the δ13C = −3.2%. (PDB), suggest the presence of a magmatic component in the gas feeding the investigated manifestations. The above relations and the almost constant high He/N2 ratio suggest that all the fumaroles are fed by the same deep hot fluids. On the basis of both the chemical characters of the fluids and the geothermo-barometric data, a deep geothermal body, having a temperature of about 240°C, is recognized. Two other shallower thermal aquifers, with a temperature of 170–210°C, are identified. A circulation pattern of the geothermal fluids is also proposed. On the basis of calculations regarding the convective energy released by the geothermal system of Panarea, and the magmatic mass responsible for the positive gravimetric anomaly of the area, it was estimated that the last volcanic activity took place less then 10,000 years ago.  相似文献   

20.
The effect of hexavalent chromium on the carp,Cyprinus carpio was assessed using static bioassay. The 96h LC50 was found to be 93.6mg · l–1. In carp exposed to sublethal concentrations of chromium (15 and 25 mg · l–1), significant depletion of liver and muscle glycogen and decreasing leucocyte counts were recorded during prolonged exposure and with increasing concentration of chromium. The other blood parameters examined (haemoglobin, erythrocyte count, hematocrit, serum protein, serum glucose) increased similarly during exposure to two chromium concentrations.  相似文献   

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