Terrestrial ecosystem processes of Victoria Land, Antarctica

Terrestrial environments of Victoria Land, Antarctica are ideal systems to test hypotheses about the sensitivity of ecosystem processes to climate variability, and the relationships between soil biodiversity and ecosystem functioning because of their high sensitivity to climate change and their limited diversity. This region is also considered among the most pristine of ecosystems, and therefore may serve as an indicator for detecting the response of other ecosystems to global environmental change. Rates and controls over key ecosystem processes remain poorly documented over much of Victoria Land, but it is generally held that the distribution and functioning of soil communities are most limited by the availability of liquid water and organic carbon. Here we review examples of ecosystem processes from several sites in North and South Victoria Land and develop a regional synthesis accounting for variation in the availability of soil resources (i.e. liquid water, organic matter, inorganic nutrients). Variation in soil microclimate, organic matter, moisture and salinity encountered over gradients of coastal to interior sites, latitude, and soil chronosequences are the primary controls over the structure of soil communities and their functioning. Imbalanced stoichiometric nutrient ratios frequently encountered in Victoria Land ecosystems also contribute to limited distribution of soil biota, and where they occur these elemental imbalances indicate lower biological activity and little biotic control over bulk element ratios in soils. Priorities and future directions of Victoria Land soil and ecosystem research are also discussed.     

Shifting microbial community structure across a marine terrace grassland chronosequence, Santa Cruz, California

Changes in the biomass and structure of soil microbial communities have the potential to impact ecosystems via interactions with plants and weathering minerals. Previous studies of forested long-term (1000s - 100,000s of years) chronosequences suggest that surface microbial communities change with soil age. However, significant gaps remain in our understanding of long-term soil microbial community dynamics, especially for non-forested ecosystems and in subsurface soil horizons. We investigated soil chemistry, aboveground plant productivity, and soil microbial communities across a grassland chronosequence (65,000-226,000 yrs old) located near Santa Cruz, CA. Aboveground net primary productivity (ANPP) initially increased to a maximum and then decreased for the older soils. We used polar lipid fatty acids (PLFA) to investigate microbial communities including both surface (<0.1 m) and subsurface (≥0.2 m) soil horizons. PLFAs characteristic of Gram-positive bacteria and actinobacteria increased as a fraction of the microbial community with depth while the fungal fraction decreased relative to the surface. Differences among microbial communities from each chronosequence soil were found primarily in the subsurface where older subsurface soils had smaller microbial community biomass, a higher proportion of fungi, and a different community structure than the younger subsurface soil. Subsurface microbial community shifts in biomass and community structure correlated with, and were likely driven by, decreasing soil P availability and Ca concentrations, respectively. Trends in soil chemistry as a function of soil age led to the separation of the biological (≤1 m depth) and geochemical (>1 m) cycles in the old, slowly eroding landscape we investigated, indicating that this separation, commonly observed in tropical and subtropical ecosystems, can also occur in temperate climates. This study is the first to investigate subsurface microbial communities in a long-term chronosequence. Our results highlight connections between soil chemistry and both the aboveground and belowground parts of an ecosystem.     

Bioremediation of Mangroves Impacted by Petroleum

The majority of oil from oceanic oil spills (e.g. the recent accident in the Gulf of Mexico) converges on coastal ecosystems such as mangroves. Microorganisms are directly involved in biogeochemical cycles as key drivers of the degradation of many carbon sources, including petroleum hydrocarbons. When properly understood and managed, microorganisms provide a wide range of ecosystem services, such as bioremediation, and are a promising alternative for the recovery of impacted environments. Previous studies have been conducted with emphasis on developing and selecting strategies for bioremediation of mangroves, mostly in vitro, with few field applications described in the literature. Many factors can affect the success of bioremediation of oil in mangroves, including the presence and activity of the oil-degrading microorganisms in the sediment, availability and concentration of oil and nutrients, salinity, temperature and oil toxicity. More studies are needed to provide efficient bioremediation strategies to be applicable in large areas of mangroves impacted with oil. A major challenge to mangrove bioremediation is defining pollution levels and measuring recuperation of a mangrove. Typically, chemical parameters of pollution levels, such as polycyclic aromatic hydrocarbons (PAHs), are used but are extremely variable in field measurements. Therefore, meaningful mangrove monitoring strategies must be developed. This review will present the state of the art of bioremediation in oil-contaminated mangroves, new data about the use of different mangrove microcosms with and without tide simulation, the main factors that influence the success of bioremediation in mangroves and new prospects for the use of molecular tools to monitor the bioremediation process. We believe that in some environments, such as mangroves, bioremediation may be the most appropriate approach for cleanup. Because of the peculiarities and heterogeneity of these environments, which hinder the use of other physical and chemical analyses, we suggest that measuring plant recuperation should be considered with reduction in polycyclic aromatic hydrocarbons (PAHs). This is a crucial discussion because these key marine environments are threatened with worldwide disappearance. We highlight the need for and suggest new ways to conserve, protect and restore these environments.     

Carbon sinks in mangroves and their implications to carbon budget of tropical coastal ecosystems

Nearly 50% of terrigenous materials delivered to the world's oceans are delivered through just twenty-one major river systems. These river-dominated coastal margins (including estuarine and shelf ecosystems) are thus important both to the regional enhancement of productivity and to the global flux of C that is observed in land-margin ecosystems. The tropical regions of the biosphere are the most biogeochemically active coastal regions and represent potentially important sinks of C in the biosphere. Rates of net primary productivity and biomass accumulation depend on a combination of global factors such as latitude and local factors such as hydrology. The global storage of C in mangrove biomass is estimated at 4.03 Pg C; and 70% of this C occurs in coastal margins from 0° to 10° latitude. The average rate of wood production is 12.08 Mg ha^?1 yr^?1, which is equivalent to a global estimate of 0.16 Pg C/yr stored in mangrove biomass. Together with carbon accumulation in mangrove sediments (0.02 Pg C/yr), the net ecosystem production in mangroves is about 0.18 Pg C/yr. Global estimates of export from coastal wetlands is about 0.08 Pg C/yr compared to input of 0.36 Pg C/yr from rivers to coastal ecosystems. Total allochthonous input of 0.44 Pg C/yr is lower than in situ production of 6.65 Pg C/yr. The trophic condition of coastal ecosystems depends on the fate of this total supply of 7.09 Pg C/yr as either contributing to system respiration, or becoming permanently stored in sediments. Accumulation of carbon in coastal sediments is only 0.41 Pg C/yr; about 6% of the total input. The NEP of coastal wetlands also contribute to the C sink of coastal margins, but the source of this C is part of the terrestrial C exchange with the atmosphere. Accumulation of C in wood and sediments of coastal wetlands is 0.205 Pg C/yr, half the estimate for sequestering of C in coastal sediments. Burial of C in shelf sediments is probably underestimated, particularly in tropical river-dominated coastal margins. Better estimates of these two C sinks in the tropics, coastal wetlands and shelf sediments, is needed to better understand the contribution of coastal ecosystems to the global carbon budget.     

Deforesting the riverscape: the effects of wood on fish diversity in a Venezuelan piedmont stream

While deforestation of tropical ecosystems has been shown to have significant impacts on terrestrial habitats, its effects on aquatic habitats are poorly studied. Deforestation dramatically reduces the input of woody debris to streams, and given the importance of large woody debris to fish communities in temperate streams, this might be one mechanism by which logging could affect aquatic ecosystems in the tropics. To examine the effects of large woody debris on the diverse fish assemblage of a tropical stream, we surveyed pools with and without wood at Rio Las Marias, Venezuela. Pools containing wood contained greater numbers of individuals and more species of fish than pools without wood, and the two types of pools differed in their composition. To test whether these results were due to the presence of woody debris, we conducted an experimental wood addition. Pools to which wood was added showed marked increases in both fish abundance and species richness relative to wood-free pools, and the composition of the fish assemblage in experimental pools approached that of pools with naturally occurring woody debris. These results demonstrate that large woody debris plays a major role in structuring fish communities in tropical streams. As a consequence, logging practices that reduce the input of woody debris to tropical streams or directly remove wood from streams could have serious impacts on aquatic habitats, affecting both the diverse fish communities and local economies dependent on stream fisheries.     

Assessing the effects of environmental pollutants on soil organisms,communities, processes and ecosystems

A wide range of pollutants reach the soils of natural and managed ecosystems in concentrations that can affect their function. These chemicals, which include pesticides, heavy metals, acid deposition and a range of industrial chemicals, can reach soils in many different ways and by various routes. The ecological impacts of these chemicals on agricultural systems can involve effects at the: (i) organism population level, in terms of individual life histories (birth rate, numbers, growth, mortality); (ii) at the community level in terms of effects on plant/plant, plant/microbial, or plant/faunal interactions, species diversity and on soil food webs; (iii) at the ecosystem level, effects on primary and secondary productivity, organic matter breakdown and nutrient cycling; (iv) at the landscape level, changes in spatial heterogeneity of plants and soil organisms, material transfer of soil and nutrients, and hydrologic transfers of nutrients. Currently available methods of assessing the effect of pollutants include single species laboratory tests, a few multi-species assays, and integrated soil microcosms and terrestrial model ecosystems. The latter two methods produce data on the effects of pollutants on populations, communities and ecosystems as well as the fate of pollutants.     

Contrasting recreational and commercial fishing: Searching for common issues to promote unified conservation of fisheries resources and aquatic environments

Commercial fishing has repeatedly been identified as a major causal factor for global declines in fish stocks. Recently, recreational fisheries have also been considered as having the potential to contribute to fisheries declines. Here, we take a global focus, contrasting the characteristics of commercial and recreational fisheries relevant to conservation and sustainability of exploited fishes in both marine and freshwater environments. We provide evidence to support our assertion that the same issues that have led to global fisheries concerns regarding commercial fishing can have equivalent, and in some cases, magnified effects in recreational fisheries. Contrasts revealed that the issues of bycatch and catch-and-release, fisheries-induced selection, trophic changes, habitat degradation, gear technology, fishing effort, and production regimes are remarkably similar among fishery sectors. In recognition of this conclusion, we present a new vision for recreational fishing that positions it on the same scale and urgency as commercial fisheries. Efforts to manage and conserve fisheries must recognise that issues and threats are similar in these fundamentally and philosophically different fisheries, as may be the solutions. Failure to recognise the similarities will further polarise these sectors and retard efforts to conserve aquatic resources. Fishing activity of any kind, whether commercial or recreational, has the potential to affect negatively fish and fisheries, as well as aquatic environments.     

Soil carbon stocks and their primary origin at mature mangrove ecosystems in the estuary of Fukido River,Ishigaki Island,southwestern Japan

ABSTRACT

Mangrove ecosystems play an important role in carbon (C) accumulation in tropical and subtropical regions. Below-ground deep anoxic soil is especially important for C accumulation. However, quantitative data on below-ground soil C stocks in mangrove ecosystems are lacking compared with data on above-ground biomass. In addition, soil C accumulation processes in mangrove ecosystems have not been sufficiently clarified. In this study, we quantified soil C stocks and focused on the mass of fallen litter and below-ground roots, which are produced by tree and that may directly influence soil C stocks in a mature subtropical mangrove in the estuary of Fukido River, Ishigaki Island, southwestern Japan. The principal species in this study site were Bruguiera gymnorhiza and Rhizophora stylosa, and total above-ground biomass at the site was 80.7 ± 1.3 (mean ± SD) Mg C ha^?1 over the period from 2014 to 2016. Litter was collected in six litter traps from May 2013 to November 2016, it ranged from 7.8 to 11.5 Mg C ha^?1, with the major proportion of litter being from foliage (leaves and stipules). The root C density at 90-cm depth was 27.1 ± 11.3 Mg C ha^?1. The soil C stock in the mangrove forest at a depth of 90 cm at the study site was 251.0 ± 34.8 Mg C ha^?1, and it seems to be lower value in the tropical region but it to be higher in subtropical East Asian mangrove sites. Dead roots, especially dead fine roots, but not fallen litter, were significantly positively correlated with soil C stocks. The δ¹³C values obtained from soils ranged from ?29.3‰ to ?27.0‰; these values are consistent with those for below-ground fine roots. These results strongly suggest that dead fine roots could be a main factor controlling soil C stocks at this study site.     

Coupling of nutrient cycling and carbon dynamics in the Arctic,integration of soil microbial and plant processes

Most studies of nutrient cycling in arctic ecosystems have either addressed questions of plant nutrient acquisition or of decomposition and mineralization processes, while few studies have integrated processes in both the soil and plant compartments. Here, we synthesize information on nutrient cycling within, and between, the soil/microbial and the plant compartments of the ecosystems and integrate the cycling of nutrients with the turnover of organic matter and the carbon balance in tundra ecosystems. Based on this compilation and integration, we discuss implications for ecosystem function in response to predicted climatic changes.Many arctic ecosystems have high amounts of nutrients in the microbial biomass compared to the pools in the plant biomass both due to large nutrient-containing organic deposits in the soil and low plant biomass. The microbial pools of N and P, which are the most commonly limiting nutrients for plant production, may approach (N) or even exceed (P) the plant pools. Net nutrient mineralization is low, the residence time of nutrients in the soil is long and the nutrients are strongly immobilized in the soil microorganisms. This contributes to pronounced nutrient limitation for plant productivity, implies that the microbial sink strength for nutrients is strong and that the microbes may compete with plants for nutrients, but also that they are a potential source of plant nutrients during periods of declining microbial populations. The extent of this competition is poorly explored and it is uncertain whether plants mainly take up nutrients continuously during the summer when the microbial activity and, presumably, also the microbial sink strength is high, or whether the main nutrient uptake occurs during pulses of nutrient release when the microbial sink strength declines.Improved knowledge of mechanisms for plant-microbial interactions in these nutrient-limited systems is important, because it will form a basis also for our understanding of the C exchange between the ecosystems and the atmosphere under the predicted, future climatic change. High microbial nutrient immobilization, i.e. low release of plant-available nutrients, paired with high microbial decomposition of soil organic matter will lead to a loss of C from the soil to the atmosphere, which may not be compensated fully by increased plant C fixation. Hence, the system will be a net source of atmospheric C. Conversely, if plants are able to sequester extra nutrients efficiently, their productivity will increase and the systems may accumulate more C and turn into a C sink, particularly if nutrients are allocated to woody tissues of low nutrient concentrations.     

Effect of understory fern (Dicranopteris dichotoma) removal on substrate utilization patterns of culturable soil bacterial communities in subtropical Eucalyptus plantations

Although understory vegetation is known to play an important role in driving the processes and functions of forest ecosystems, little is known about how understory vegetation affects the composition and function of soil microbial communities in forest ecosystems, especially in subtropical and tropical forests. This study used the experimental removal of understory fern (Dicranopteris dichotoma) to investigate the effect of the fern on substrate utilization patterns of culturable soil bacterial communities in two subtropical Eucalyptus plantations. One year after treatment, the removal of understory fern significantly increased soil temperature by 2–3 °C and retarded litter decomposition by 5.6–23.1%. However, understory fern removal did not affect the substrate utilization pattern of soil bacterial communities. Our study provides evidence that, although understory fern removal significantly alters soil temperature and litter decomposition rate, the disturbance caused by understory removal one year after treatment is too weak to cause detectable changes in substrate utilization pattern of culturable soil bacterial communities in subtropical Eucalyptus plantations.     

Linking spatial metrics and fish catch reveals the importance of coastal wetland connectivity to inshore fisheries in Queensland, Australia

Many commercially important fish species use coastal marine environments such as mangroves, tidal flats and seagrass beds as nurseries or breeding grounds. The ecological importance of spatially connected habitats to conservation is well established for terrestrial environments. However, few studies have applied spatial metrics, including measures of structural connectivity to marine environments. We examined the relationship between catch-per-unit-effort for commercially caught species and the spatial patterning of mapped benthic habitat types along the coast of Queensland, Australia in their dominant fisheries (trawl, line, net or pot fisheries). We quantified the composition and spatial configuration of seascapes and calculated coastline length, number of estuaries, river length and geographical latitude using 12 metrics within ninety 30-nautical-mile grid cells, which supported inshore fish catch data from 21 species groups. Multiple regression analysis and non-metric multidimensional scaling plots indicated that ecological linkages may exist between geomorphic coastal features and nearshore fisheries production for a number of species groups. Connectivity indices for mangroves, salt marsh and channels explained the largest proportion (30–70%), suggesting the importance of connected tidal wetlands for fisheries. Barramundi (Lates calcarifer) catch-per-unit-effort was best explained by the number of wetland patches, mangrove connectivity and wetland connectivity (r² = 0.38, n = 28). Catch-per-unit-effort for the Gulf of Carpentaria was highly correlated with wetland connectivity, the number of estuaries and seagrass patch density (r = 0.57, n = 29). The findings could guide the spatial design of marine protected area networks to maintain ecosystem services and avoid potential disruption to connectivity caused by habitat removal or modification. Application of the same approach to analyses of finer spatial scales would enable catch information to be related to particular estuarine habitats and provide better understanding of the importance of habitat connectivity for fisheries.     

More than just indicators: A review of tropical butterfly ecology and conservation

Roughly 90% of butterfly species live in the tropics. Despite this, we know very little about tropical butterfly ecology particularly when compared to temperate butterfly systems. The relative scarcity of data on tropical butterfly populations hampers our ability to effectively conserve them. In this review we summarize recurring themes from ecological research on tropical butterflies to serve as a framework for understanding their conservation. Key themes include: (1) the tropics represent the evolutionary origins of butterfly diversity, (2) while some tropical butterflies exhibit relatively stable population dynamics, longer-lived adult stages, and more continuous age-specific reproduction compared to temperate zone species, the generality of these patterns is debatable, and (3) complex species interactions (e.g. mimicry, parasitism and predation) can have significantly greater influences on ecological and evolutionary processes in tropical butterflies than in temperate ones. This state of ecological knowledge, combined with scarce resources, has traditionally constrained tropical butterfly conservation efforts to habitat level approaches, unlike the species- and population-specific approaches familiar in North America and Europe. Consequently, much conservation research on butterflies in the tropics has focused on the relationship between habitat quality (e.g. forest fragmentation) and butterfly diversity, though predictive patterns even in this regard remain elusive. We argue that with the increasing threats of habitat destruction, fragmentation and climate change, it is necessary to move beyond this diversity and habitat relationship if we are to improve predictive capabilities when evaluating anthropogenic impacts on tropical butterfly communities. Tropical butterflies are more than just useful indicator species. They represent some of the most spectacular and visually appealing organisms in the world and play many vital roles in tropical ecosystems. We hope that this synthesis will lay the groundwork for future ecological studies of tropical butterfly populations, species, communities and conservation.     

转Bt基因棉花根际细菌与古菌群落结构分析

在一年内棉花的四个生长时期（苗期,蕾期,花铃期,吐絮期）分别采集转Bt基因抗虫棉GK12和非转基因亲本棉花泗棉3号根际土壤,以及未种植棉花的背景土壤,利用末端标记限制性片段长度多态性（T-RFLP）分析技术,分析三种土壤中细菌和古菌的16S rRNA基因片段多态性,结合克隆文库建立和测序,研究了土壤中细菌和古菌群落结构的变化.结果表明：在棉花生长的各个时期,背景土壤中细菌群落结构发生了明显的变化,生物多样性指数明显降低,古菌群落结构也有一定的变化,说明季节性变化对土壤中微生物群落产生了明显的影响.与背景土壤相比,棉花种植后根际土壤中细菌和古菌群落发生显著的变化.转基因棉花与非转基因棉花相比,根际土壤细菌和古菌的种类和种群大小的分布也发生了明显的改变.克隆文库和测序结果表明土壤中主体微生物为目前未培养的、功能特性未知的细菌和古菌,转基因棉花种植对这些细菌和古菌影响的原因、环境危害和生态风险目前尚不清楚.与古菌群落相比,棉花种植对细菌群落结构的影响较小.     

Simulated grazer effects on microbial respiration in a subarctic meadow: Implications for nutrient competition between plants and soil microorganisms

Plant-microbial competition for nutrients is considered to be a strong mechanism affecting nutrient distribution in subarctic ecosystems, but the role of grazers on the distribution of nutrients between the plants and soil microorganisms remain poorly understood. We designed a factorial fertilization and clipping experiment to study the potential competition between plants and soil microorganisms for soil nitrogen in an ecosystem under grazing. We assumed that clipping reduces plant photosynthetic capacity and C flux to the soil, which ultimately results in lower microbial substrate availability and reduced potential for N immobilization. In concurrence with microbial substrate availability, increased nutrient availability through fertilization was expected to enhance microbial N in the unclipped but not in the clipped treatment.Clipping significantly reduced microbial respiration, suggesting that grazing reduces the labile C available for soil microbes in the system. Clipping had no effect on microbial C and N and the amount of NH₄-N captured in ion exchange resin bags, which was used as an index of net N mineralization. Microbial potential for N immobilization thus seemed insensitive to grazer-mediated changes in microbial availability of labile substrates. Fertilization had no effects or interactions with clipping on microbial C and N. By contrast, we found a close negative correlation between the plant root biomass and microbial N, indicating that plants had a negative impact on the microbial nutrient acquisition. The subarctic grassland vegetation seemed superior to the soil microorganisms in the competition for nutrients even when the plants were subjected to artificial grazing. We suggest that nutrient competition by higher plants constrained the microbial N immobilization in the system, which could explain why the reduction in microbial C availability by clipping had little effects on microbial N acquisition. In this subarctic system, grazing has significant influences on soil C cycling, but due to plant predominance in the competition for nutrients, does not affect N allocation between the plants and the soil microorganisms.     

Enzyme activities as a component of soil biodiversity: A review

Soil enzyme activities are the direct expression of the soil community to metabolic requirements and available nutrients. While the diversity of soil organisms is important, the capacity of soil microbial communities to maintain functional diversity of those critical soil processes through disturbance, stress or succession could ultimately be more important to ecosystem productivity and stability than taxonomic diversity. This review examines selected papers containing soil enzyme data that could be used to distinguish enzyme sources and substrate specificity, at scales within and between major nutrient cycles. Developing approaches to assess soil enzyme functional diversity will increase our understanding of the linkages between resource availability, microbial community structure and function, and ecosystem processes.     

Linking species richness, biodiversity and ecosystem function in soil systems

Soils are the central organizing entities in terrestrial ecosystems and possess extremely diverse prokaryotic and eukaryotic biota. They are physically and chemically complex, with micro- and macro-aggregates embedded within a solid, liquid and gaseous matrix that is continually changing in response to natural and human-induced perturbations. Recent advances in molecular techniques in systematics have provided opportunities for the study of biodiversity and biocomplexity of soil biota. A symposium and workshop on soil biogeochemistry and biodiversity International Symposium on Impacts of Soil Biodiversity on Biogeochemical Processes in Ecosystems, Taiwan Forestry Research Institute, Taipei, Taiwan April 18-24, 2004. Convened an international array of participants working in biomes on virtually every continent on the planet (ranging from polar to tropical regions). This special issue reports on the theoretical bases and applications of molecular methods for the measurement of soil biodiversity.

Themes addressed include a melding of classical taxonomic investigations with biochemical fingerprinting and molecular probing of organism identities. Several papers highlight new advances in identifications of prokaryotic and eukaryotic organisms. Examples include new developments in “fingerprinting” of microbes active in “mycorrhizospheres” using immunocapture and other innovative techniques. Developments in the study of impacts of invasive plant and animal species on ecosystem function and subsequent microbial community composition and function have been very great in the last 2-3 years. Soils are major repositories of legacies, including fine and coarse woody debris and other organic products, which have feedbacks on soil diversity. The ways in which species diversity and function of microbial and faunal communities interact and their importance to ecosystem function are examined in biological and biochemical detail. This paper provides an overview of soil biodiversity and its feedbacks on soil biogeochemical processes in ecosystems.     

The Selection Exerted by Oil Contamination on Mangrove Fungal Communities

Mangrove ecosystems are tropical environments that are characterized by the interaction between the land and the sea. As such, this ecosystem is vulnerable to oil spills. Here, we show a culture-independent survey of fungal communities that are found in the sediments of the following two mangroves that are located on the coast of Sao Paulo State (Brazil): (1) an oil-spill-affected mangrove and (2) a nearby unaffected mangrove. Samples were collected from each mangrove forest at three distinct locations (transect from sea to land), and the samples were analyzed by quantitative PCR and internal transcribed spacer (ITS)-based PCR-DGGE analysis. The abundance of fungi was found to be higher in the oil-affected mangrove. Visual observation and correspondence analysis (CA) of the ITS-based PCR-DGGE profiles revealed differences in the fungal communities between the sampled areas. Remarkably, the oil-spilled area was quite distinct from the unaffected sampling areas. On the basis of the ITS sequences, fungi that are associated with the Basidiomycota and Ascomycota taxa were most common and belonged primarily to the genera Epicoccum, Nigrospora, and Cladosporium. Moreover, the Nigrospora fungal species were shown to be sensitive to oil, whereas a group that was described as ??uncultured Basidiomycota?? was found more frequently in oil-contaminated areas. Our results showed an increase in fungal abundance in the oil-polluted mangrove regions, and these data indicated potential fungal candidates for remediation of the oil-affected mangroves.     

木质素与蚯蚓对黑麦草生物量及土壤微生物群落的影响

采集农田土壤,设置添加木质素和蚯蚓不同组合处理的黑麦草盆栽试验,在测定植物生物量的基础上,结合定量PCR、高通量测序等方法,研究木质素和蚯蚓及其联合作用对土壤细菌、真菌群落的影响。结果显示:木质素显著降低了黑麦草的生物量,而蚯蚓能够缓解木质素的抑制作用,促进黑麦草生长。木质素明显抑制了土壤细菌、真菌数量,并改变群落结构,以Sphingomonadaceae、Methylophilaceae为标志的降解细菌和担子菌等潜在降解真菌显著富集;单一加入蚯蚓对土壤微生物的影响相对较小,木质素和蚯蚓组合处理显著提高细菌、真菌数量,改变上述降解微生物的丰度。这些结果表明,木质素降低土壤微生物数量,并可能通过其自身降解释放的酚类化感物质抑制植物生长,对土壤生态系统健康产生不利影响;蚯蚓与木质素联合处理影响土壤中木质素降解微生物组成,微生物数量与植物生物量均表现增加趋势,蚯蚓有利于土壤中木质素的微生物代谢,并为植物生长提供更多的养分。本研究为农田生态系统木质素资源化利用提供了科学依据。     

From common to rare: The case of the Mediterranean common dolphin

Although overfishing has been recognized as responsible for the decline of major fish stocks, it has been less easy to demonstrate its indirect and detrimental effects on marine mammals, particularly dolphins. Competition with fisheries for the same food resources has been hypothesized to have led to the decline of several species of dolphins, including the endangered Mediterranean short-beaked common dolphin. Based on an ecosystem model for the Inner Ionian Sea Archipelago, a former hotspot for common dolphins in the Mediterranean Sea, we investigated the effect of increasing fishing effort on common dolphins, its prey and on marine biodiversity and we evaluated the outcomes of different fisheries closures (1 – closure of the purse seine fishery, 2 – closure of purse seine, trawl and beach seine fisheries, 3 – entire area closed to fisheries) ran between the years 2011 and 2030. Our results showed that local fisheries have negatively impacted the marine biodiversity of the ecosystem causing sharp declines of common dolphins and major fish stocks and weakening the robustness of the marine food web. The implementation of fisheries closures would gradually recover fish stocks, while common dolphins would increase more pronouncedly only if the study area was to be closed to all fisheries. As shown in this study, common dolphins have reflected ecosystem changes and degradation over time. Ensuring the survival of dolphin populations is thereby essential to enhance marine ecosystems and ensure sustainable fishing.     

Ecoenzymatic stoichiometry at the extremes: How microbes cope in an ultra-oligotrophic desert soil

Arid ecosystems are characterized by stressful conditions of low energy and nutrient availability for soil microorganisms. It has been observed that the ecoenzymes needed for the transformation of organic compounds into assimilable products show similar scaling relationships in different habitats (logarithmic C:N:P scaling ratios ∼1:1:1). In this study in Cuatro Ciénegas Basin (CCB) in the Chihuahuan desert of México, we report among the lowest ecoenzymatic activities yet quantified in soil. Nevertheless, activities for both organic N and organic P acquisition enzymes scale with C acquisition with a slope of ∼1.0, indicating that the soil microbial communities of this ultra-oligotrophic desert ecosystem follow the global ecoenzymatic stoichiometry patterns. CCB soil microbial communities were co-limited by C and either by N or P but this co-limitation played out differently in different parts of the CCB as indicated by microbial ecoenzymatic shift to allocate more resources to acquire and immobilize the scarcer nutrient. By extending ecoenzymatic analyses to these ultra-oligotrophic soils, our findings support the broad utility of the approach in illuminating how microbes acquire limiting resources in arid ecosystems.