Ornithogenic soils of the cape bird adelie penguin rookeries,Antarctica

Summary The activity of soil-forming processes in the ornithogenic soils under the adelie penguin rookeries at Cape Bird, Ross Island, Antarctica, is limited by low temperatures and aridity, and is dominated by the influence of organic input from the penguins. A study of soil chemistry, biochemistry and biology of ornithogenic soils was carried out during the austral summers of 1981/1982 and 1983/1984. For the study, five sites were used to represent a relative age sequence in biological activity, from a presently occupied colony, a recently (previous season) abandoned colony, a re-worked guano site, and a long abandoned (many years) colony, to compare with a site that apparently had never been occupied by penguins. The sites were selected by the apparent age of the guano based on its morphology. Characteristics of the soils and guanos within the sequence are now described and illustrated, to complement the chemistry, biochemistry and biology of these sites, results of which have been published previously in this journal. A conventional radiocarbon age of 8 080±160 years BP (14C No. 5990) was obtained from a penguin bone in the long abandoned colony guano. A few temperature records indicated that soil temperatures were higher from soils with guano cover than from adjacent soils without guano cover. This difference in temperature should contribute to the increased biological and biochemical activity in the guano soils.     

Precipitation nitrogen at maritime Signy Island and continental Cape Bird,Antarctica

Summary The mineral nitrogen (NH₄-N + NO₃-N) in precipitation occurring at continental and maritime Antarctic sites has been determined. Precipitation at sites remote from animal activity contained much less mineral N than that occurring at sites influenced by such activity. Estimates for nitrogen input at two contrasting fellfield sites, one at continental Cape Bird (dry site), the other at maritime Signy Island (wet site) are presented. At both sites precipitation N represented the major N input to fellfield biota than did wind blown particulate matter containing organic nitrogen or ammonia volatilized from adjacent guano soils and becoming absorbed by moist artificial soils traps.     

Changes in alkaline phosphatase activity and phosphate uptake in P-limited phytoplankton,induced by light intensity and spectral quality

Alkaline phosphatase activity and P uptake were determined in P-limited Dunaliella tertiolecta, Thalassiosira pseudonana, Phaeodactylum tricornumtum, and Prymnesium parvum grown under different light intensities and colors. Both intracellular and extracellular enzyme activities varied with the intensity and quality of light in a species-specific manner. The spectral composition of the light also affected P uptake kinetics. No correlation was found between enzyme activity and V_max both within a species and for pooled data for all four species, indicating that the change in uptake kinetics and enzyme activity was not related to P limitation, but induced by the light conditions. Changes in the optimum N:P ratio induced by light were also not related to P uptake kinetics or enzyme activity. These data suggest that light conditions may in themselves have profound effects on species competition for limiting nutrients. Furthermore, since both alkaline phosphatase activity and P uptake were influenced by the prevailing light conditions we suggest that these parameters be used cautiously when determining the P nutritional status of phytoplankton in nature.Address for reprint requests     

Microbial Responses to Long-Term N Deposition in a Semiarid Grassland

Nitrogen (N) enrichment of the biosphere is an expanding problem to which arid ecosystems may be particularly sensitive. In semiarid grasslands, scarce precipitation uncouples plant and microbial activities, and creates within the soil a spatial mosaic of rhizosphere and cyanobacterial crust communities. We investigated the impact of elevated N deposition on these soil microbial communities at a grama-dominated study site located incentral New Mexico (USA). The study plots were established in 1995 and receive 10 kg ha⁻¹ year⁻¹ of supplemental N in the form of NH₄NO₃. Soil samples were collected in July 2004, following 2 years of severe drought, and again in March 2005 following a winter of record high precipitation. Soils were assayed for potential activities of 20 extracellular enzymes and N₂O production. The rhizosphere and crust-associated soils had peptidase and peroxidase potentials that were extreme in relation to those of temperate soils. N addition enhanced glycosidase and phosphatase activities and depressed peptidase. In contrast to temperate forest soils, oxidative enzyme activity did not respond to N treatment. Across sampling dates, extracellular enzyme activity responses correlated with inorganic N concentrations. N₂O generation did not vary significantly with soil cover or N treatment. Microbial responses to N deposition in this semiarid grassland were distinct from those of forest ecosystems and appear to be modulated by inorganic N accumulation, which is linked to precipitation patterns.     

Prediction of nitrogen availability and rice yield in lowland soils: Nitrogen mineralization parameters

Field experiments were conducted under flooded soil conditions using Maahas clay amended with urea and rice straw-sesbania mixtures during the wet and dry seasons. Parallel laboratory incubation tests were done. The objectives were 1) to determine N mineralization patterns and establish the relationship between mineralization parameters and either N availability or grain yield, and 2) to correlate the results of organic N mineralization studies in the laboratory with data from field experiments. The N mineralization patterns of flooded soils in the laboratory followed a logistic function. In laboratory studies, mineralization potential was positively correlated with extractable soil NH₄ ⁺-N at the end of the incubation period (cumulative available N). Likewise, mineralization potential calculated from laboratory studies was positively correlated with N uptake and grain yield from field studies. Extractable (NH₄ ⁺+NO₃ ^–)-N in the field correlated positively with extractable NH₄ ⁺-N in the laboratory. The extractable NH₄ ⁺-N from laboratory incubations at 14 days after transplanting, panicle initiation, and maturity was also highly and positively correlated with grain yield from field experiments.     

Synthesis and secretion of phosphatases by endophytic isolates of Colletotrichum musae grown under conditions of nutritional starvation

Even though fungal phosphatases are widely used to study ambient-regulated gene expression, little is known about these enzymes in the agriculturally important genus Colletotrichum. We have therefore identified several phosphatase activities in endophytic isolates of Colletotrichum musae grown under conditions of nutritional sufficiency or starvation for sources of phosphorus (P), nitrogen (N), carbon (C), and sulphur (S). These enzyme forms could be distinguished by substrate specificity, optimum pH, activation and inhibition by some substances, response to nutritional starvation, and pattern of migration in native gel electrophoresis. At least four individual phosphatase activities were identified under the growth conditions employed. A pH 5.0 acid phosphatase and an Mg(2+)-dependent pH 7.5 phosphodiesterase were expressed under all growth conditions at constant rates. Under conditions of P-starvation, derepression of a major pH 6.0-acid phosphatase was observed in cell-free extracts and the culture medium. A synthesis of alkaline phosphatase activities followed a more distinct pattern. Under conditions of nutritional sufficiency of P- or N-starvation, only a single intracellular enzyme form (optimum pH 10) was observed, which was resolved as a single electrophoretic activity band. However, in media lacking C or S sources additional alkaline phosphatase forms were derepressed with a concomitant increase in the overall enzyme activity level measured at pH 10. To our knowledge, this report represents the most detailed study of phosphatases in Colletotrichum and the first partial characterization of the phosphatase system in an endophytic fungus.     

A telescopic method for photographing within 8×8 cm minirhizotrons

The volatile organic compounds produced during a sequence of soil incubations under controlled conditions, with either added NH₄ ⁺-N or NO₃ ^--N, were collected and identified. The nature and relative amounts of the volatile organic compounds produced by the microorganisms in the soils were remarkably reproducible and consistent.     

Ex-situ enzyme activity and bacterial community diversity through soil depth profiles in penguin and seal colonies on Vestfold Hills, East Antarctica

The soils impacted by sea animal excreta are important sources of nutrients in Antarctic terrestrial ecosystems, and soil microorganisms are the principal drivers of carbon and nitrogen cycling. However, microbial diversity and enzyme activities in these soils have still received little attention. In this paper, we investigated the distribution characteristics of bacterial community in four penguin and seal colony soil profiles collected in East Antarctica, using 16S rDNA-DGGE and real-time quantitative PCR. Soil microbial biomass carbon (C_mic), soil respiration (SR), and enzyme activities involved in carbon, nitrogen, and phosphorus metabolisms were also measured. Overall soil C_mic, SR, enzyme activities, and bacterial abundance decreased with depth. The bacterial abundance had a significant correlation with soil organic carbon and total nitrogen and highly corresponded to the relative content of penguin guano or seal excreta in these soil profiles. The 16S rDNA-DGGE revealed the complicated bacterial community structure in penguin and seal colony soils, and the band richness and dominant bands decreased with soil depth. Cluster analysis of DGGE profiles indicated that bacterial community in those soil profiles were divided into four main categories with the bacterial genetic similarity of 22 %, and the majority of the sequenced bands were Proteobacteria (α, β, γ), Actinobacteria, Bacteroidetes, Deinococcus-Thermus, Chloroflexi, and Firmicutes. Our results indicated that the deposition of penguin guano or seal excreta, which caused the variability in soil soil organic carbon, total nitrogen, pH, and soil moisture, might have an important effect on the vertical distribution pattern of bacterial abundance and diversity in Antarctic soil profiles.     

Different temperature sensitivity and kinetics of soil enzymes indicate seasonal shifts in C,N and P nutrient stoichiometry in acid forest soil

Acid forest soils in the Bohemian Forest in Central Europe are biogeochemically imbalanced in organic C, N and P processing. We hypothesized that these imbalances can be due to different temperature sensitivities of soil enzyme activities and their affinities to substrate in litter and organic soil horizons. We measured potential activities of five main soil enzymes (β-glucosidase, cellobiohydrolase, Leu-aminopeptidase, Ala-aminopeptidase, and phosphatase) responsible for organic carbon, nitrogen and phosphorus acquisition. We also modeled potential in situ enzyme activities and nutrient release based on continuous in situ temperature measurements. We determined basic kinetic parameters (K_m, V_max), enzyme efficiencies (k_cat) and temperature sensitivities (E_a and Q₁₀) according to Michaelis–Menten kinetic and modified Arrhenius models. Our results showed significant differences in substrate affinities between the litter and organic soil horizons. Higher aminopeptidase affinity (lower K_m) in the litter soil horizon can lead to leaching of peptidic compounds to lower soil horizons. β-Glucosidase and phosphatase showed high temperature response following the Arrhenius model. However, both aminopeptidases showed no or even decreased activity with increasing temperature. The aminopeptidase temperature insensitivity means that peptidic compounds are degraded at the same or even lower rate in warmer and colder periods of the year in acid forest soils. This imbalance results in different release of available nutrients from plant litter and soil organic matter which may affect bacterial and fungal community composition and nutrient leaching from these ecosystems.     

The winter migration of Adelie penguins breeding in the Ross Sea sector of Antarctica

Satellite telemetry was used to monitor the migratory movements of a single Adelie penguin (Pygoscelis adeliae) from Cape Hallett (72.31°S, 170.21°E) following the 1997/1998 breeding season. Locations were obtained using the ARGOS satellite system and compared with the migratory paths taken by two penguins from the Northern Colony at Cape Bird, Ross Island (77.22°S, 166.48°E) following the 1990/1991 breeding season. Although the sample sizes are small, if representative they would indicate that: (1) Adelie penguins breeding in the Ross Sea follow a common migratory path, (2) Adelie penguins breeding in the Ross Sea may travel to a common over-winter feeding ground west and north of the Balleny Islands, and (3) Adelie penguins breeding at 77°S on Ross Island travel nearly twice the distance during their over-winter migration as do those penguins breeding at Cape Hallett and colonies further north. While the Cape Hallett penguin was tracked successfully for 172 days, a record for Adelie penguins, the problem of long-term attachment of transmitters to penguins remains.     

Elevated CO2 increases microbial carbon substrate use and nitrogen cycling in Mojave Desert soils

Identifying soil microbial responses to anthropogenically driven environmental changes is critically important as concerns intensify over the potential degradation of ecosystem function. We assessed the effects of elevated atmospheric CO₂ on microbial carbon (C) and nitrogen (N) cycling in Mojave Desert soils using extracellular enzyme activities (EEAs), community‐level physiological profiles (CLPPs), and gross N transformation rates. Soils were collected from unvegetated interspaces between plants and under the dominant shrub (Larrea tridentata) during the 2004–2005 growing season, an above‐average rainfall year. Because most measured variables responded strongly to soil water availability, all significant effects of soil water content were used as covariates to remove potential confounding effects of water availability on microbial responses to experimental treatment effects of cover type, CO₂, and sampling date. Microbial C and N activities were lower in interspace soils compared with soils under Larrea, and responses to date and CO₂ treatments were cover specific. Over the growing season, EEAs involved in cellulose (cellobiohydrolase) and orthophosphate (alkaline phosphatase) degradation decreased under ambient CO₂, but increased under elevated CO₂. Microbial C use and substrate use diversity in CLPPs decreased over time, and elevated CO₂ positively affected both. Elevated CO₂ also altered microbial C use patterns, suggesting changes in the quantity and/or quality of soil C inputs. In contrast, microbial biomass N was higher in interspace soils than soils under Larrea, and was lower in soils exposed to elevated CO₂. Gross rates of NH₄⁺ transformations increased over the growing season, and late‐season NH₄⁺ fluxes were negatively affected by elevated CO₂. Gross NO₃⁻ fluxes decreased over time, with early season interspace soils positively affected by elevated CO₂. General increases in microbial activities under elevated CO₂ are likely attributable to greater microbial biomass in interspace soils, and to increased microbial turnover rates and/or metabolic levels rather than pool size in soils under Larrea. Because soil water content and plant cover type dominates microbial C and N responses to CO₂, the ability of desert landscapes to mitigate or intensify the impacts of global change will ultimately depend on how changes in precipitation and increasing atmospheric CO₂ shift the spatial distribution of Mojave Desert plant communities.     

Soil minerals and humic acids alter enzyme stability: implications for ecosystem processes

In most ecosystems, the degradation of complex organic material depends on extracellular enzymes produced by microbes. These enzymes can exist in bound or free form within the soil, but the dynamics of these different enzyme pools remain uncertain. To address this uncertainty, I determined rates of enzyme turnover in a volcanic soil with and without added enzymes. I also tested whether or not soil minerals and humic acids would alter enzyme activity. In soils that were gamma-irradiated to stop enzyme production, 35–70% of the enzyme activity was stable throughout the 21-day incubation. The remaining enzyme fraction decayed at rates ranging from − 0.032 to − 0.628 day⁻¹. In both the irradiated soils and in soils with added enzymes, addition of the mineral allophane had a strong positive effect on most enzyme activities. Another added mineral, ferrihydrite, had a weak positive effect on some enzymes. Added humic acids strongly inhibited enzyme activity. These findings suggest that minerals, especially allophane, enhance potential enzyme activities in young volcanic soils. However, the actual activity and function of these enzymes may be low under field conditions if stabilization results in less efficient enzyme-substrate interactions. If this is the case, then much of the measured enzyme activity in bulk soil may be stabilized but unlikely to contribute greatly to ecosystem processes.     

The effect of burning on soil enzyme activities in natural grasslands in southern India

Soil amylase, cellulase, invertase and phosphatase activities were determined following wildfire in a savanna type grassland in southern India. Activities of these enzymes increased substanially in burned soils compared to those in adjacent unburned soils. Surface soil (0–10 cm) exhibited a greater increase in enzyme activities than subsurface soil (10–20 cm). Amylase activity was more pronounced following fire than the other enzyme activities.     

十万大山地区典型次生阔叶林土壤微生物数量及酶活性的季节动态

为了评价广西十万大山南麓次生阔叶林土壤质量的变化,该研究以广西十万大山南麓典型季雨林中的次生阔叶林土壤为对象,采用实地调查与实验分析相结合的方法,对其土壤微生物数量和土壤蔗糖酶、脲酶、磷酸酶、过氧化氢酶的季节动态规律进行研究。结果表明:土壤过氧化氢酶、脲酶、蔗糖酶和酸性磷酸酶在垂直分布上均表现为0~10 cm土层高于10~20、20~30 cm土层,差异显著(P0.05);随季节性水热状况的变化,各种土壤酶活性有明显的季节性变化,其中0~10、10~20和20~30 cm土层中过氧化氢酶活性呈双峰模式,高峰出现在春季和秋季;土壤脲酶、酸性磷酸酶活性均呈单峰模式,高峰均出现在夏季;而蔗糖酶活性呈现秋季夏季春季冬季趋势。土壤细菌、放线菌和真菌含量均随着土壤深度的增加而减小,差异显著(P0.05);细菌、放线菌和真菌数量的季节变化大小顺序呈夏季秋季春季冬季的变化趋势。相对于旱季,在十万大山南麓地区,典型次生阔叶林土壤微生物数量及酶活性季节性变化对高温多降水的雨季响应更明显。     

Satellite telemetry of the winter migration of Adélie penguins (Pygoscelis adeliae)

Adélie penguins (Pygoscelis adeliae), after breeding in Antarctica during the austral summer, undergo a winter migration before returning to the breeding grounds 8 months later. It is the major source of adult mortality, with about a quarter of them not returning. Here we describe the first attempt to track the winter migration of Adélie penguins using satellite telemetry. Transmitters were attached to two penguins on 16 February 1991 after their post-breeding moult at Cape Bird, Ross Island, Antarctica. Transmissions were received from one penguin (bird #1) for 4.4 months, during which time it travelled 2792.6 km from the rookery (nearly 1500 km straight-line distance). Transmissions were received from the other penguin (bird #2) for 2.5 months during which time it followed a path remarkably similar to that of bird #1. The penguins travelled northwards up the coast of Victoria Land, keeping within 100 km of the coast, rounding Cape Adare soon after 29 March and were midway between the Balleny Islands and the Antarctic coast on 3 May. Thereafter, the record from bird #1 shows that it travelled further westwards until, when opposite the Mastusevich Glacier Tongue of the Mastusevich Glacier, it turned due north and moved away from the coast. By 29 June, when transmissions ended, its progression had slowed and it was northwest of the Balleny Islands near a zone where pack ice covered 75% of the surface of the sea. Two novel points that arise from this study are: (1) that Adélie penguins from Cape Bird undergo winter migrations of not less than 5000 km, and (2) that they may be travelling to common overwinter feeding grounds.     

Production of fungal rennet byMucor miehei using solid state fermentation

Summary Investigations have been carried out on the production of fungal rennet using a thermophilic strain ofMucor miehei under solid state fermentation conditions. A high milk clotting enzyme activity (58000 Soxhlet units/g) was achieved when optimum conditions were used. Further, a high ratio of 6.6:1 between milk clotting and proteolytic activities for this enzyme was obtained. Cheese prepared using this enzyme was also found to be acceptable in organoleptic quality. Large scale production of the enzyme in trays using the optimum conditions gave milk-clotting enzyme activities comparable to those in flask experiments.     

模拟氮沉降增加条件下土壤团聚体对酶活性的影响

氮沉降增加改变了森林土壤生态系统物质输入,影响土壤生物及酶活性,而土壤团聚体内相对稳定的微域生境可能减弱或延缓土壤生物和酶对氮沉降增加的响应强度。以广东省东莞大岭山森林公园荷木人工林为研究对象,用模拟N沉降方法,分析了2011年12月到2012年11月一年内氮沉降增加条件下表层混合土壤和土壤团聚体内脲酶、蔗糖酶和酸性磷酸酶活性的变化及影响因素,旨在理解氮沉降增加条件下土壤团聚体对酶活性的影响。结果表明:氮沉降增加对表层混合土壤中脲酶和蔗糖酶的抑制作用不显著,而酸性磷酸酶受氮沉降显著影响,表现为低氮(50 kg N hm-2a-1)促进,高氮(300 kg N hm-2a-1)抑制的规律。表层土壤团聚体内脲酶活性随氮沉降增加而降低,N300处理显著低于对照;蔗糖酶和酸性磷酸酶活性随氮沉降增加先降低后增加,N100处理最低,分别比其他处理降低了6.46%—25.53%和42.33%—68.25%。试验区内各粒径土壤团聚体内酶活性高于混合土壤,且随团聚体粒径增加酶活性均为先增加后降低。不同粒径土壤团聚体的3种酶活性均以2—5 mm最高,但脲酶、酸性磷酸酶在各团聚体粒径间差异不显著,蔗糖酶活性2—5 mm显著高于5—8 mm。土壤酶相对活性指数和相对活性综合指数结果显示,超过85%的团聚体粒径内的相对酶活性指数大于1,而土壤酶相对活性综合指数均大于1。以上结果表明,氮沉降增加条件下土壤团聚体对其团聚体内的土壤酶活性有隔离保护作用,但其隔离保护效果与酶的种类和土壤团聚体粒径有关。     

Field investigations of ammonia exchange between barley plants and the atmosphere. II. Nitrogen realiocation, free ammonium content and activities of ammonium-assimilating enzymes in different leaves

The activities of glutamine synthetase (GS) and glutamate synthase (GOGAT) in different leaves of field-grown spring barley were measured during the reproductive growth phase in 2 consecutive years. Concurrently, the contents of soluble ammonium ions and free amides in the leaves were determined. The studies were carried out to investigate the relationship between variations in these parameters and emission of NH3 from the plant foliage. GS and GOGAT activities declined very rapidly with leafage. The decline in enzyme activities was followed by an increase in soluble ammonium ions and amides in the leaf tissues. During the same period, about 75% of leaf and stem nitrogen was reallocated to the developing ear. The amount of NH₃ volatilized from the foliage during the reproductive growth phase amounted to about 1% of the reallocated nitrogen. The experimental years were characterized by very favourable conditions for grain dry matter formation and for re-utilization of nitrogen mobilized from leaves and stems. Ammonia volatilization occurring under conditions with declining GS and GOGAT activities and increasing tissue concentrations of NH₄⁺ may be useful in protecting the plant from accumulation of toxic NH₃ and NH₄⁺ concentrations in the tissues.     

Regulation of extracellular acid phosphatase biosynthesis by culture conditions in entomopathogenic fungusMetarhizium anisopliae strain CQMa102

Metarhizium anisopliae is an imperfect entomopathogenic fungus. Once invading into its host,M. anisopliae needs to absorb basic nutrients such as phosphorus from the host haemolymph. A large number of phosphorylated compounds in haemolymph cannot be directly utilised by the fungal cell and must be hydrolysed into available form by phosphatase before ingested. Aims of this paper were to investigate optimum fermentation conditions for production of acid phosphatase and phosphatase isoenzymes byMetarhizium anisopliae. The optimum fermentation conditions were: glucose, 20 g/l; (NH₄)₂SO₄, 2 g/l; casein, 4 g/l; MgSO₄, 0.5 g; KCl, 0.5 g; microelement salt solution, 10 ml; inoculum size, 1×10⁷ spores per 100 ml medium; initial medium pH, 6.0. Under these conditions, the highest total acid phosphatase activity was 3.05 U/ml in 4 days at 27 °C and 160 rpm. Synthesis of the acid phosphatase was repressed by 0.01% inorganic phosphate in culture medium. The spectrum of isoenzymes produced byM. anisopliae varied depending on the phosphorus source employed in the culture. A specific isoform with pI 9.45 was induced by casein, and another isoform of pI 8.21 was induced by phytic acid and disodium phenyl phosphate.     

Properties and partial purification of mevalonate kinase from Agave americana

Mevalonate kinase activity was demonstrated in acetone powder extracts from Agave americana leaves, flowers and scape. ATP was the most effective phosphate donor. The enzyme had an optimum pH of 7.9 in Tris-HCl buffer. Dialysis decreased the ability to phosphorylate mevalonic acid (MVA). Partially purified mevalonate kinase reached maximum activity in the presence of 2 mM Mn²⁺ or 6–8 mM Mg²⁺. Higher concentrations of Mn²⁺ were inhibitory, whereas higher concentrations of Mg²⁺ produced only a small decrease in the activity. The amount of mevalonate-5-phosphate (MVAP) formed depended on protein concentration and incubation time. During short incubations, the MVAP formed increased as protein concentration rose, whereas during prolonged incubations (1–6 hr), there was a decrease in the MVAP formed when a certain amount of protein was exceeded. It is suggested that MVAP formed was hydrolysed by a phosphatase present in the extracts. This interfering activity was eliminated when mevalonate kinase is partially purified. The apparent K_m values of the enzyme from leaves were 0.05 mM for MVA and 0. 14 mM for ATP. Similar K_m values are obtained with partially purified mevalonate kinase. The enzyme was purified by ammonium sulphate precipitation, Sephadex G-100 filtration and DEAE-Sephadex A-50 fractionation.