The action spectrum for maximal photosensitivity of germination

 Fruits of Garden Lettuce, imbibed in 0.01 M KNO₃, were depleted of maternal active phytochrome B by saturating deep-red exposure and photosensitized by chilling for 1 week at 4  °C. Twenty saturated fluence-response curves for photoinduced germination were elaborated between 300 and 800 nm, using exposure periods from 6 to 600 s at 22.5  °C; there is linear and closely parallel regression in the logarithmic probability net. The reciprocals of the half-response fluences obtained gave the apparent conversion spectrum of the controlling pigments and this was corrected for the transmittance of the seed-coat. It is a phytochrome spectrum of P _r with photoconversion cross-sections of 1.2·10⁹ and 4.5·10³ m² mol^–1 at 666 and 800 nm, respectively. This means that for half-saturated germination of sensitized seed, fewer than 1 out of 200,000 phytochrome A molecules have to be photoconverted to P _fr, and no photo-reversibility by deep-red was found. Therefore, all spectral colours of nightly moon- or skylight should stimulate the germination of sensitized weed seeds if they are exposed at the soil surface between sequential tillage operations. Received: 28 April 2000 / Accepted in revised form: 28 July 2000     

Significance of organic matter in Eocene turbidite sediments (SE Pyrenees,Spain)

Although turbidite deposits are classically considered to be good reservoir rocks for oil and gas, there are no reports concerning their source rock potential in the literature. The sediments from the Vallfogona Formation in the South-Eastern Pyrenees present numerous organic matter-rich levels interbedded in sandstones and coarse turbidite deposits. Two types of organic matter deposits were differentiated on the basis of organic geochemistry and petrography: type A and type B. Type A was deposited in a carbonate marine environment under hypersaline conditions as indicated mainly by even/odd n-alkane predominance, pristane and phytane ratio (Pr/Ph) < 1, presence of gammacerane, and trisnorneohopane over trisnorhopane ratio (Ts/Tm) > 1. Type B was deposited in a more mud-rich marine environment evidenced by the predominance of odd n-alkane, Pr/Ph ≥ 1, Ts/Tm < 1, the absence of gammacerane, similar concentrations of the C₂₇ and C₂₉ regular steranes, and the greater abundance of C₂₇ diasteranes. Turbidite facies can be regarded as an environment where organic matter sedimentation is heterogeneous in type and amount. This study suggests that turbidite deposits with interbedded organic matter-rich levels may act as a combined source–reservoir system.     

Numerical dating of the Eckfeld maar fossil site, Eifel, Germany: a calibration mark for the Eocene time scale

 Sediments of the Eckfeld maar (Eifel, Germany) bear a well-preserved Eocene fauna and flora. Biostratigraphically, Eckfeld corresponds to the Middle Eocene mammal reference level MP (Mammals Paleogene) 13 of the ELMA (European Land Mammal Age) Geiseltalian. In the maar crater, basalt fragments were drilled, representing explosion crater eruption products. By ⁴⁰Ar/³⁹Ar dating of the basalt, for the first time a direct numerical calibration mark for an Eocene European mammal locality has been established. The Eckfeld basalt inverse isochron date of 44.3±0.4 Ma suggests an age for the Geiseltalian/Robiacian boundary at 44 Ma and, together with the 1995 time scale of Berggren et al., a time span ranging from 49 to 44 Ma for the Geiseltalian and from 44 to 37 Ma for the Robiacian, respectively. Additional ⁴⁰Ar/³⁹Ar dating on a genetically related basalt occurrence close to the maar confirms a period of volcanism of ca. 0.6 m.y. in the Eckfeld area, matching the oldest Eocene volcanic activity of the Hocheifel volcanic field. Received: 27 December 1999 / Accepted in revised form: 6 April 2000     

Light-dependent magnetoreception in birds: the effect of intensity of 565-nm green light

 In a previous study, Australian silvereyes tested in autumn under monochromatic 565-nm green light at intensities of 2.1 and 7.5 mW m^–2 preferred their normal northerly migratory direction, whereas they showed a significantly different tendency towards northwest at 15.0 mW m^–2. Repeating these experiments in spring with silvereyes migrating southward, we again observed well-oriented tendencies in the migratory direction at 2.1 and 7.5 mW m^–2. At 15.0 mW m^–2, however, the birds once more preferred northwesterly directions, i.e. their response under this condition proved to be independent of the migratory direction. This contradicts the interpretation that monochromatic green light of this high intensity leads to a rotation of compass information; instead, it appears to produce sensory input that causes birds to give up their migratory direction in favor of a fixed direction of as yet unknown origin. Received: 3 April 2000 / Accepted in revised form: 19 June 2000     

Mycotoxin production on rice, pulses and oilseeds

 Mycotoxin-producing fungi were isolated from contaminated grains of rice, pulses and oilseeds sold in the local markets of Calcutta for human consumption. It was found that aflatoxin B₁ was produced by Aspergillus flavus and Aspergillus parasiticus, aflatoxin G₁ by A. flavus, ochratoxin by Aspergillus ochraceous, sterigmatocystin by Aspergillus japonicus and citrinin by Penicillium citrinum. Aflatoxin B₁ (333–10416 μg/kg) was produced by Aspergillus spp. in rice, pulses and oilseeds. Received: 11 May 1999 / Accepted in revised form: 10 April 2000     

Heat and carbon dioxide generated by honeybees jointly act to kill hornets

We have found that giant hornets (Vespa mandarinia japonica) are killed in less than 10 min when they are trapped in a bee ball created by the Japanese honeybees Apis cerana japonica, but their death cannot be solely accounted for by the elevated temperature in the bee ball. In controlled experiments, hornets can survive for 10 min at the temperature up to 47°C, whereas the temperature inside the bee balls does not rise higher than 45.9°C. We have found here that the CO₂ concentration inside the bee ball also reaches a maximum (3.6 ± 0.2%) in the initial 0–5 min phase after bee ball formation. The lethal temperature of the hornet (45–46°C) under conditions of CO₂ concentration (3.7 ± 0.44%) produced using human expiratory air is almost the same as that in the bee ball. The lethal temperature of the honeybee is 50–51°C under the same air conditions. We concluded that CO₂ produced inside the bee ball by honeybees is a major factor together with the temperature involved in defense against giant hornets.     

Isolation and fractionation of soil humin using alkaline urea and dimethylsulphoxide plus sulphuric acid

Humin, the most recalcitrant and abundant organic fraction of soils and of sediments, is a significant contributor to the stable carbon pool in soils and is important for the global carbon budget. It has significant resistance to transformations by microorganisms. Based on the classical operational definition, humin can include any humic-type substance that is not soluble in water at any pH. We demonstrate in this study how sequential exhaustive extractions with 0.1 M sodium hydroxide (NaOH) + 6 M urea, followed by dimethylsulphoxide (DMSO) + 6% (v/v) sulphuric acid (H₂SO₄) solvent systems, can extract 70–80% of the residual materials remaining after prior exhaustive extractions in neutral and aqueous basic media. Solid-state ¹³C NMR spectra have shown that the components isolated in the base + urea system were compositionally similar to the humic and fulvic acid fractions isolated at pH 12.6 in the aqueous media. The NMR spectra indicated that the major components isolated in the DMSO + H₂SO₄ medium had aliphatic hydrocarbon associated with carboxyl functionalities and with lesser amounts of carbohydrate and peptide and minor amounts of lignin-derived components. The major components will have significant contributions from long-chain fatty acids, waxes, to cuticular materials. The isolates in the DMSO + H₂SO₄ medium were compositionally similar to the organic components that resisted solvation and remained associated with the soil clays. It is concluded that the base + urea system released humic and fulvic acids held by hydrogen bonding or by entrapment within the humin matrix. The recalcitrant humin materials extracted in DMSO + H₂SO₄ are largely biological molecules (from plants and the soil microbial population) that are likely to be protected from degradation by their hydrophobic moieties and by sorption on the soil clays. Thus, the major components of humin do not satisfy the classical definitions for humic substances which emphasise that these arise from microbial or chemical transformations in soils of the components of organic debris.     

Electric Organ Discharges of Mormyrid Fish as a Possible Cue for Predatory Catfish

During reproductive migration the electroreceptive African sharptooth catfish, Clarias gariepinus (Siluriformes), preys mainly on a weakly electric fish, the bulldog Marcusenius macrolepidotus (Mormyridae; Merron 1993). This is puzzling because the electric organ discharges of known Marcusenius species are pulses of a duration (<1 ms) too short for being detected by the catfishes' low-frequency electroreceptive system (optimum sensitivity, 10–30 Hz; Peters and Bretschneider 1981). On the recent discovery that M. macrolepidotus males emit discharges lasting approximately ten times longer than those of females (Kramer 1997a) we determined behavioral thresholds for discharges of both sexes, using synthetic playbacks of field-recorded discharges. C. gariepinus detected M. macrolepidotus male discharges down to a field gradient of 103 μV_peak-peak/cm and up to a distance of 1.5 m at natural field conditions. In contrast, thresholds for female discharges were not reached with our setup, and we presume the bulldogs eaten by catfish are predominantly male. Received: 7 October 1998 / Accepted in revised form: 29 December 1998     

Cerumen of Australian stingless bees (<Emphasis Type="Italic">Tetragonula carbonaria</Emphasis>): gas chromatography-mass spectrometry fingerprints and potential anti-inflammatory properties

Cerumen, or propolis, is a mixture of plant resins enriched with bee secretions. In Australia, stingless bees are important pollinators that use cerumen for nest construction and possibly for colony’s health. While extensive research attests to the therapeutic properties of honeybee (Apis mellifera) propolis, the biological and medicinal properties of Australian stingless bee cerumen are largely unknown. In this study, the chemical and biological properties of polar extracts of cerumen from Tetragonula carbonaria in South East Queensland, Australia were investigated using gas chromatography-mass spectrometry (GC-MS) analyses and in vitro 5-lipoxygenase (5-LOX) cell-free assays. Extracts were tested against comparative (commercial tincture of A. mellifera propolis) and positive controls (Trolox and gallic acid). Distinct GC-MS fingerprints of a mixed diterpenic profile typical of native bee cerumen were obtained with pimaric acid (6.31 ± 0.97%, w/w), isopimaric acid (12.23 ± 3.03%, w/w), and gallic acid (5.79 ± 0.81%, w/w) tentatively identified as useful chemical markers. Characteristic flavonoids and prenylated phenolics found in honeybee propolis were absent. Cerumen extracts from T. carbonaria inhibited activity of 5-LOX, an enzyme known to catalyse production of proinflammatory mediators (IC₅₀ 19.97 ± 2.67 μg/ml, mean ± SEM, n = 4). Extracts had similar potency to Trolox (IC₅₀ 12.78 ± 1.82 μg/ml), but were less potent than honeybee propolis (IC₅₀ 5.90 ± 0.62 μg/ml) or gallic acid (IC₅₀ 5.62 ± 0.35 μg/ml, P < 0.001). These findings warrant further investigation of the ecological and medicinal properties of this stingless bee cerumen, which may herald a commercial potential for the Australian beekeeping industry.     

Carbon sequestration of paddy fields in Western Jilin of China during 1989–2004

The study area of this article, Western Jilin province of China, was a typical area responding to global changing in middle latitude areas. In this paper, by interpreting the thematic mapper (TM) images of the study area in the years of 1989, 1996, 2000 and 2004, the land use/cover change (LUCC) data were achieved, which included the area of paddy fields and its spatial distributions. 113 soil samples were collected to obtain soil organic carbon (SOC) data of different land use types. After that, the organic matter contents of these samples were measured by using the potassium dichromate oxidation-outer heating method. Based on the data above, the amount of SOC sequestrated by the surface soil (0~30 cm) of paddy fields was calculated. The result showed that: the area of paddy fields was increasing continuously in western Jilin, from 11.28 × 10⁴ hm² in 1989 to 22.77 × 10⁴ hm² in 2004. Paddy fields transferred from wetlands, grasslands and water areas accounted for the main part of the paddy fields in 2004, the areas were 3.09 × 10⁴ hm², 2.98 × 10⁴ hm² and 2.8 × 10⁴ hm², respectively. And paddy fields with a total area of 0.83 × 10⁴ hm² degraded into saline-alkali lands. The amount of organic carbon sequestration in the surface layer (0–30 cm) of paddy fields was 658.86 × 10⁴ t. The primary SOC sinks located around the joint of Baicheng City and Zhenlai County, while the major SOC source located at Songyuan City and northern Qianguo County.     

Strategic 3-hydroxy-2-butanone release in the dominant male lobster cockroach, <Emphasis Type="Italic">Nauphoeta cinerea</Emphasis>

In the lobster cockroach Nauphoete cinerea, the dominant–subordinate hierarchy formed via the agonistic interactions is unstable, and changes in rank order are common. Our previous results showed that in the first encounter fight during initial rank formation, microgram levels of 3H-2B are released by the aggressive posture (AP)-adopting dominant male. In the present study, the pattern of daily pheromone (3H-2B) release during the domination period and on the day of rank switch, rank duration, and rank switch frequency were investigated in three-male groups and six-male groups to examine the effect of higher frequency of agonistic encounters. The results showed that, in the three-male groups (50-day observation period), daily 3H-2B release rate was not constant, but fluctuated, the average duration of dominant rank was 16.6 ± 2.0 days, rank switch occurred in 58.8% of groups, and the frequency of rank switching (average number of rank switches/group/50 days) was 1.4 ± 0.2. For the six-male groups (30-day observation period), the daily 3H-2B release rate also fluctuated, but the duration of dominant rank was significantly shorter at 4.2 ± 0.6 days, rank switch occurred in 100% of groups, and the frequency of rank switching (average number of rank switches/group/30 days) was significantly higher at 6.9 ± 0.6. The results for both sets of male groups showed that as a new rank formed (either on the first encounter day or on the day of rank switching), the dominant status was significantly associated with a higher 3H-2B release rate. In the animal kingdom, fighting usually involves communication or the exchange of signals, and the results of this study indicated that the fluctuating daily 3H-2B release rate adopted by the dominants is a kind of strategic release and the 3H-2B release rate is a signal used to determine dominance.     

High-field 1H T1 and T2 NMR relaxation time measurements of H2O in homeopathic preparations of quartz, sulfur, and copper sulfate

Quantitative meta-analyses of randomized clinical trials investigating the specific therapeutic efficacy of homeopathic remedies yielded statistically significant differences compared to placebo. Since the remedies used contained mostly only very low concentrations of pharmacologically active compounds, these effects cannot be accounted for within the framework of current pharmacology. Theories to explain clinical effects of homeopathic remedies are partially based upon changes in diluent structure. To investigate the latter, we measured for the first time high-field (600/500 MHz) ¹H T₁ and T₂ nuclear magnetic resonance relaxation times of H₂O in homeopathic preparations with concurrent contamination control by inductively coupled plasma mass spectrometry (ICP-MS). Homeopathic preparations of quartz (10c–30c, n = 21, corresponding to iterative dilutions of 100⁻¹⁰–100⁻³⁰), sulfur (13x–30x, n = 18, 10⁻¹³–10⁻³⁰), and copper sulfate (11c–30c, n = 20, 100⁻¹¹–100⁻³⁰) were compared to n = 10 independent controls each (analogously agitated dilution medium) in randomized and blinded experiments. In none of the samples, the concentration of any element analyzed by ICP-MS exceeded 10 ppb. In the first measurement series (600 MHz), there was a significant increase in T₁ for all samples as a function of time, and there were no significant differences between homeopathic potencies and controls. In the second measurement series (500 MHz) 1 year after preparation, we observed statistically significant increased T₁ relaxation times for homeopathic sulfur preparations compared to controls. Fifteen out of 18 correlations between sample triplicates were higher for controls than for homeopathic preparations. No conclusive explanation for these phenomena can be given at present. Possible hypotheses involve differential leaching from the measurement vessel walls or a change in water molecule dynamics, i.e., in rotational correlation time and/or diffusion. Homeopathic preparations thus may exhibit specific physicochemical properties that need to be determined in detail in future investigations. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Global warming potential of emissions from rice paddies in Northeastern China

In this study, paddy fields in Jilin province which are flooded parcel of arable lands used for growing rice (Oryza sativa Linn.) were selected as the object. Long-term exploitation of paddy fields led to variations of soil organic carbon (SOC) and green house gases (GHGs) emissions which might contribute to global warming. In order to calculate the amount of global warming potentials (GWPs) of emissions from ricepaddies and find the correlations among rice yield, SOC storage and GWP, DeNitrification-DeComposition (DNDC) model was used to simulate SOC densities and fluxes of main GHGs emitted from paddy fields. After verification, simulation results were used to calculate SOC storages and 100-year GWPs from 1949 to 2009. Results indicated that SOC densities in depths of 0–10 cm, 10–20 cm and 20–30 cm all kept increasing. Average methane (CH₄) and nitrous oxide (N₂O) fluxes were 278.55 kg carbon (kgC) ha⁻¹ a⁻¹ and 2.22 kg nitrogen (kgN) ha⁻¹ a⁻¹. The SOC storage (0–30 cm) had increased from 3.96 × 10⁹kgC in 1949 to 47.85 × 10⁹kgC in 2009. In addition, GWP emission was increasing exponentially in the past 61 years, from 0.16 × 10⁶ Mg carbon dioxide equivalents (CO₂-equivalents) to 66.36 × 10⁶ Mg CO₂-equivalents. Both SOC storage and GWP presented obviously linear relation to rice yields. Overall, the research suggested that long-term rice yields could be used to estimate the SOC storage and GWP variations.     

Anatomic and acoustic sexual dimorphism in the sound emission system of Phoenicoprocta capistrata (Lepidoptera: Arctiidae)

Both sexes of Phoenicoprocta capistrata have functional tymbals. The scanning electron microscopy revealed differences in the morphology of these organs in males and females. Male tymbals have a well-developed striated band, constituted by 21 ± 2 regularly arranged striae whereas female tymbals lack a striated band. This type of sexual dimorphism is rare in Arctiidae. The recording of the sound produced by moths held by the wings revealed that while males produced trains of pulses organized in modulation cycles, females produced clicks at low repetition rate following very irregular patterns. Statistically, there are differences between sexes in terms of the duration of pulses, which were 355 ± 24 μs in the case of males and 289 ± 29 μs for females. The spectral characteristics of the pulses also show sexual dimorphism. Male pulses are more tuned (Q ₁₀ = 5.2 ± 0.5) than female pulses (Q ₁₀ = 2.7 ± 0.5) and have a higher best frequency (42 ± 1 kHz vs. 29 ± 2 kHz). To our knowledge, this is the first report on an arctiid moth showing sexual dimorphism in tymbal’s anatomy that leads to a best frequency dimorphism. Males produce sound at mating attempts. The sounds recorded during mating are modulation cycles with the same spectral characteristics as those recorded when males are held by the wings. The morphological and acoustic features of female tymbals could indicate a process of degeneration and adaptation to conditions under which the emission of complex patterns is not necessary. Frank Coro no longer works at Universidad de La Habana.     

Seed drops and caches by the harvester ant Messor barbarus: do they contribute to seed dispersal in Mediterranean grasslands?

 To determine whether the harvester ant Messor barbarus acts as a seed disperser in Mediterranean grasslands, the accuracy level of seed processing was assessed in the field by quantifying seed drops by loaded foragers. In the vicinity of exploited seed patches 3 times as many diaspores were found as in controls due to seed losses by foragers. Over trails, up to 30% of harvested seeds were dropped, singly, by workers but all were recovered by nestmates within 24 h. Seeds were also dropped within temporary caches with very few viable diaspores being left per cache when ants no longer used the trail. Globally, ant-dispersed diaspores accounted for only 0.1% of seeds harvested by M. barbarus. We discuss the possible significance for grassland vegetation of harvester-ant-mediated seed dispersal. Received: 26 January 2000 / Accepted in revised form: 20 June 2000     

In vivo measurements of the internal pH of Hediste (Nereis) diversicolor (Annelida, Polychaeta) exposed to ambient sulphidic conditions using pH microelectrodes

 The effect of different ambient sulphide concentrations on the internal pH regime of Hediste (Nereis) diversicolor was studied under in vivo conditions using liquid membrane pH microelectrodes, a method which is new to marine sciences. As a case study, the hypothesis was tested whether organisms exposed to ambient sulphidic conditions are able to lower their internal pH which, in effect, would reduce sulphide influx into the animals and thus could represent an effective detoxification mechanism. It was shown that a significant lowering of the internal pH occurred within only 20 min after adding sulphide. This pH lowering appeared to be dependent on the external sulphide concentration of the ambient medium and showed a saturation beyond a threshold level of about 130 μM. It is discussed whether this sulphide-induced pH drop is an active regulatory mechanism and acts as an effective protection mechanism against sulphide during short-term exposures. Received: 1 June 1999 / Accepted in revised form: 3 May 2000     

How water saving irrigation contributes to climate change resilience—a case study of practices in China

A warming climate system is now an indisputable fact. An effective response to climate change should include both mitigation and adaptation. Water is essential to human survival and social development. But the shortage of water resources is a worldwide problem, which in China has been exacerbated by climate change. In order to find out how to cope with climate change successfully, this study, on the basis of China statistical data 2007–2009, quantitatively analyzes the role of water saving irrigation (WSI) in addressing climate change. The study shows that water saving irrigation (WSI) can serve as a useful enabler in dealing with climate change. From the perspective of mitigation, the 3-year total CO₂ emission reduction stands at 34.67 (21.83 ~ 47.48) Mt, about per year 11.56(7.28 ~ 15.83)Mt. From the perspective of adaptation, the total water saved from 2007 to 2009 stands at 96.85 (61.81 ~ 129.66) Gm³. If per unit farmland irrigation takes a 3-year average of agricultural water consumption, the water saved in 2009 is enough to irrigate additional 5.70 (3.80 ~ 7.80) Mhm², or to increase the grain yield by 22.04 (14.68 ~ 30.15) Gt. In addition, WSI can reduce soil salinization and conserve soil to sustain land productivity and environmental benefits. So WSI can be a positive measure in coping with climate change when it is rightly deployed. However, the costs and local context of such practices call for further studies.     

The key to winter survival: daily torpor in a small arid-zone marsupial

Mammalian hibernation, which lasts on average for about 6 months, can reduce energy expenditure by >90% in comparison to active individuals. In contrast, the widely held view is that daily torpor reduces energy expenditure usually by about 30%, is employed for a few hours every few days, and often occurs only under acute energetic stress. This interpretation is largely based on laboratory studies, whereas knowledge on daily torpor in the field is scant. We used temperature telemetry to quantify thermal biology and activity patterns of a small arid-zone marsupial, the stripe-faced dunnart Sminthopsis macroura (16.9 g), in the wild and to test the hypothesis that daily torpor is a crucial survival strategy of this species in winter. All individuals entered torpor daily with the exception of a single male that remained normothermic for a single day (torpor on 212 of 213 observation days, 99.5%). Torpor was employed at air temperatures (T _a) ranging from approximately −1°C to 36°C. Dunnarts usually entered torpor during the night and aroused at midday with the daily increase of T _a. Torpor was on average about twice as long (mean 11.0 ± 4.7 h, n = 8) than in captivity. Animals employed sun basking during rewarming, reduced foraging time significantly, and occasionally omitted activity for several days in sequence. Consequently, we estimate that daily torpor in this species can reduce daily energy expenditure by up to 90%. Our study shows that for wild stripe-faced dunnarts daily torpor is an essential mechanism for overcoming energetic challenges during winter and that torpor data obtained in the laboratory can substantially underestimate the ecological significance of daily torpor in the wild.     

Separating method and dynamic processes of Nano-Al13

In order to investigate the characteristics of pure Nano-Al₁₃, Nano-Al₁₃ was separated and purified from a series of poly-aluminum chloride (PAC) solutions which had the same Al₁₃ percentage but different total Al concentrations, by using column chromatography, ethanol-acetone resolving and SO²⁻ ₄/Ba²⁺ displacement. The Al₁₃ species yield was characterized by Al-ferron timed complexation spectrophotometry and ²⁷Al-NMR (nuclear magnetic resonance). The coagulation efficiency of Nano-Al₁₃, PAC and AlCl₃ in synthetic water was also investigated by Jar tests. The dynamic process and aggregation state of kaolin suspensions coagulating with Nano-Al₁₃, PAC and AlCl₃ were similarly investigated using a photometric dispersion analyzer 2000 (PDA2000). The experimental results indicated that the ethanol-acetone resolving method was simple and could separate the PAC solution at different concentrations, while column chromatography could separate PAC solutions at low concentrations. The SO₄ ²⁻/Ba²⁺ displacement method could separate PAC solutions at high concentrations. However, extra inorganic cation and anion could be added in the solution during separation. The coagulation efficiency and dynamic experimental results showed that Nano-Al₁₃ with high positive-charged species was effective in removing turbidity and color. The dynamic process results showed that Nano-Al₁₃ also had the best recovery capability after shearing compared with PAC and AlCl₃ because the Nano-Al₁₃ conformation is more effective in charge neutralization. Translated from Acta Scientiae Circumstantiae, 2005, 25(6): 767–772 [译自: 环境科学学报]     

Contrasting factors controlling microbial respiratory activity in the sediment of two adjacent Mediterranean wetlands

Electron transport system (ETS) activity of sediments as an indication of microbial metabolic activity was examined in two adjacent Mediterranean wetlands (southern Spain). We determined the spatio-temporal variation in ETS, and we explored the potential biological [organic matter (OM), chlorophyll a (Chl a), aerobic and anaerobic bacteria] drivers of sediment ETS activity. ETS activity was notably higher in the eutrophic Lake Nueva (34.91 μl O₂ g⁻¹ D.W. h⁻¹) than in the hypertrophic Lake Honda (24.99 μl O₂ g⁻¹ D.W. h⁻¹). Strong spatial differences were observed in ETS in both study sites. Highest ETS values were achieved at the surface sediment at the deepest sampling station in each lake and a notable reduction in ETS with sediment depth was observed. By using linear regression and multiple regression analysis, OM was identified as the best predictor of ETS in Lake Honda while Chl a was the best predictor in Lake Nueva. The strong influence of OM supply on ETS activity in sediment from Lake Honda was the consequence of the labile nature of sedimentary OM, while a more refractory OM (with a higher contribution of vascular plants) comprised most of the sedimentary OM from Lake Nueva. By contrast, a large contribution of phytobenthos (supported by a higher lake water transparency) to ETS has been recognized in sediments from Lake Nueva. In summary, the results of this study revealed that the relative importance of planktonic primary producers (phytoplankton), benthic algae and vascular plants in the study sites could explain the differences observed in the intensity of sediment ETS as well as in their drivers.