Overview of the biogenic sources of atmospheric trace compounds due to agricultural activities

All human activities profoundly affect the chemical composition and properties of the atmosphere. The present overview highlights the impact of agricultural practices, including livestock raising, on the biogeochemical cycles of carbon and nitrogen and discusses the relevant environmental issues. Emissions from agriculture significantly contribute to the atmospheric budget of methane and nitrous oxide, which in turn contribute to the greenhouse effect. Agricultural activities are also the predominant source of ammonia to the atmosphere, so affecting the acidity of atmospheric depositions. A minor role is expected from agriculture in the production of tropospheric ozone through nitrogen oxides and volatile organic compound emissions.     

Overview of the biogenic sources of atmospheric trace compounds due to agricultural activities

All human activities profoundly affect the chemical composition and properties of the atmosphere. The present overview highlights the impact of agricultural practices, including livestock raising, on the biogeochemical cycles of carbon and nitrogen and discusses the relevant environmental issues. Emissions from agriculture significantly contribute to the atmospheric budget of methane and nitrous oxide, which in turn contribute to the greenhouse effect. Agricultural activities are also the predominant source of ammonia to the atmosphere, so affecting the acidity of atmospheric depositions. A minor role is expected from agriculture in the production of tropospheric ozone through nitrogen oxides and volatile organic compound emissions.     

The effects of herbivore-induced plant volatiles on interactions between plants and flower-visiting insects

Plants are faced with a trade-off between on the one hand growth, development and reproduction and on the other hand defence against environmental stresses. Yet, research on insect-plant interactions has addressed plant-pollinator interactions and plant-attacker interactions separately. Plants have evolved a high diversity of constitutive and induced responses to attack, including the systemic emission of herbivore-induced plant volatiles (HIPVs). The effect of HIPVs on the behaviour of carnivorous insects has received ample attention for leaf-feeding (folivorous) species and their parasitoids and predators. Here, we review whether and to what extent HIPVs affect the interaction of plants in the flowering stage with mutualistic and antagonistic insects. Whereas the role of flower volatiles in the interactions between plants and insect pollinators has received increased attention over the last decade, studies addressing both HIPVs and pollinator behaviour are rare, despite the fact that in a number of plant species herbivory is known to affect flower traits, including size, nectar secretion and composition. In addition, folivory and florivory can also result in significant changes in flower volatile emission and in most systems investigated, pollinator visitation decreased, although exceptions have been found. Negative effects of HIPVs on pollinator visitation rates likely exert negative selection pressure on HIPV emission. The systemic nature of herbivore-induced plant responses and the behavioural responses of antagonistic and mutualistic insects, requires the study of volatile emission of entire plants in the flowering stage. We conclude that approaches to integrate the study of plant defences and pollination are essential to advance plant biology, in particular in the context of the trade-off between defence and growth/reproduction.     

Trophic interactions in a changing world: modelling aboveground–belowground interactions

The rate and scale of human-driven changes can exert profound impacts on ecosystems, the species that make them up and the services they provide that sustain humanity. Given the speed at which these changes are occurring, one of society's major challenges is to coexist within ecosystems and to manage ecosystem services in a sustainable way. The effect of possible scenarios of global change on ecosystem services can be explored using ecosystem models. Such models should adequately represent ecosystem processes above and below the soil surface (aboveground and belowground) and the interactions between them. We explore possibilities to include such interactions into ecosystem models at scales that range from global to local. At the regional to global scale we suggest to expand the plant functional type concept (aggregating plants into groups according to their physiological attributes) to include functional types of aboveground–belowground interactions. At the scale of discrete plant communities, process-based and organism-oriented models could be combined into “hybrid approaches” that include organism-oriented mechanistic representation of a limited number of trophic interactions in an otherwise process-oriented approach. Under global change the density and activity of organisms determining the processes may change non-linearly and therefore explicit knowledge of the organisms and their responses should ideally be included. At the individual plant scale a common organism-based conceptual model of aboveground–belowground interactions has emerged. This conceptual model facilitates the formulation of research questions to guide experiments aiming to identify patterns that are common within, but differ between, ecosystem types and biomes. Such experiments inform modelling approaches at larger scales. Future ecosystem models should better include this evolving knowledge of common patterns of aboveground–belowground interactions. Improved ecosystem models are necessary tools to reduce the uncertainty in the information that assists us in the sustainable management of our environment in a changing world.

Zusammenfassung

Rate und Ausmaß menschen-gemachter Veränderungen wirken sich auf Ökosysteme, die Arten die diese zusammensetzen und Ökosystemfunktionen von denen die Menschheit abhängt aus. Angesichts der Geschwindigkeit dieser Veränderungen ist es eine der großen Herausforderungen der Gesellschaft miteinander und in Ökosystemen zu leben und deren Ökosystemfunktionen nachhaltig zu nutzen. Die Auswirkungen plausibler Szenarien des Globalen Wandels auf Ökosystemfunktionen können mit Hilfe von Ökosystemmodellen untersucht werden. Solche Modelle sollten die Ökosystemprozesse oberhalb und unterhalb der Erdoberfläche („oberirdisch und unterirdisch“) und die Interaktionen zwischen diesen Prozessen angemessen abbilden. Auf Skalenebenen, die von global bis lokal reichen, erkunden wir in diesem Artikel Möglichkeiten solche Interaktionen in Modelle einzubauen. Auf der regionalen bis globalen Ebene schlagen wir vor das Konzept der funktionellen Pflanzentypen (Pflanzenarten, die aufgrund von physiologischen Ähnlichkeiten in Gruppen zusammengefasst sind) auszudehnen, so dass Typen von oberirdisch-unterirdischen Interaktionen mitenthalten sind. Auf der Skalenebene eigenständiger Pflanzengesellschaften könnten prozessbasierte und organsimen-orientierte Modelle zu „Hybridmodellen“verschmolzen werden, die organismen-orientierte, mechanistische Abbildungen einiger trophischer Interaktionen enthalten, aber ansonsten prozess-basiert sind. Der Einfluss des Globalen Wandels auf die Häufigkeit und Aktivität von Organismen und die Ökosystemprozesse, die sie bestimmen, ist sehr wahrscheinlich häufig nicht-linear, so dass im Idealfall explizites Wissen über die Organismen und ihre Reaktionen in Modellen enthalten sein sollte. Auf der Skalenebene der einzelnen Pflanze hat sich ein gebräuchliches, organismen-basiertes Konzeptmodell der oberirdisch-unterirdisch Interaktionen herausgebildet. Dies erleichtert die Formulierung von Hypothesen und Fragestellungen in Experimenten, die nach gemeinsamen Mustern innerhalb von Ökosystemen und Unterschieden zwischen Ökosystemtypen und Biomen suchen. Dies ist die Basis für Modellierungsansätze auf größeren Skalenebenen. Zukünftige Ökosystemmodelle sollten die gemeinsamen Muster oberirdisch-unterirdischer Interaktionen besser berücksichtigen, die sich neuerdings abzuzeichnen beginnen. Verbesserte Ökosystemmodelle sind notwendige Werkzeuge um die Unsicherheit in der Information zu vermindern, auf der nachhaltiges Umweltmanagement in einer sich wandelnden Welt beruht.     

Effects of environmental air pollution on endogenous oxidative DNA damage in humans

Epidemiological studies conducted in metropolitan areas have demonstrated that exposure to environmental air pollution is associated with increases in mortality. Carcinogenic polycyclic aromatic hydrocarbons (c-PAHs) are the major source of genotoxic activities of organic mixtures associated with respirable particulate matter, which is a constituent of environmental air pollution. In this study,we wanted to evaluate the relationship between exposure to these genotoxic compounds present in the air and endogenous oxidative DNA damage in three different human populations exposed to varying levels of environmental air pollution. As measures of oxidative DNA damage we have determined 8-oxo-7,8-dihydro-2′-deoxyguanosine (8-oxodG) by liquid chromatography–tandem mass spectrometry (LC–MS/MS) and cyclic pyrimidopurinone N-1,N² malondialdehyde-2′-deoxyguanosine (M₁dG) by the immunoslot blot assay from lymphocyte DNA of participating individuals. The level of endogenous oxidative DNA damage was significantly increased in individuals exposed to environmental air pollution compared to unexposed individuals from Kosice (8-oxodG adducts) and Sofia (M₁dG adducts). However, there was no significant difference in the level of endogenous oxidative DNA and exposure to environmental air pollution in individuals from Prague (8-oxodG and M₁dG adducts) and Kosice (M₁dG adducts). The average level of M₁dG adducts was significantly lower in unexposed and exposed individuals from Kosice compared to those from Prague and Sofia. The average level of 8-oxodG adducts was significantly higher in unexposed and exposed individuals from Kosice compared to those from Prague. A significant increasing trend according to the interaction of c-PAHs exposure and smoking status was observed in levels of 8-oxodG adducts in individuals from Kosice. However, no other relationship was observed for M₁dG and 8-oxodG adduct levels with regard to the smoking status and c-PAH exposure status of the individuals. The conclusion that can be made from this study is that environmental air pollution may alter the endogenous oxidative DNA damage levels in humans but the effect appears to be related to the country where the individuals reside. Genetic polymorphisms of the genes involved in metabolism and detoxification and also differences in the DNA repair capacity and antioxidant status of the individuals could be possible explanations for the variation observed in the level of endogenous oxidative DNA damage for the different populations.     

湖泊生态系统服务功能评估初探--以湖北保安湖为例

随着生物资源价值估算方法的日益成熟 ,生态系统的服务评估成为生态系统研究的热点 .鉴于国内对于湖泊生态系统的服务评价的研究较少 ,本文运用生态系统学与生态经济学方法研究了湖北保安湖生态系统的部分生态服务 .计算得到 1992年保安湖水生态系统有机质生产价值为 15 14 .93万元 ,固定CO2 的价值为 4 772 .99万元 ,释放O2 的价值为 36 2 6 .5 3万元 ,主要初级生产者储存N、P的价值为 4 4 .4 8万元 ,而年吸收量的价值为 15 0 7.99万元 ,调蓄和供水的价值为 10 92 8.93万元 ,消除排入湖水SO2 价值为5 1.5 0万元 ,合计 2 .2 4× 10 8元 .据不完全估计 ,可以认为 ,生态系统具有巨大的生态经济效益。     

An index to measure the effects of temperature change on trophic interactions

Experimental studies document the fact that environmental temperature changes can affect the timing of interactions in many consumer-resource systems through altered, or shifted, phenologies of the species involved. We develop a simple mathematical model that shows one method to measure, quantitatively, the magnitude of the shift. Under different temperature regimes we compute the intersection of two regions in a joint phenology space: the region where temporal interactions can occur and the region where particular-sized predators consume particular-sized prey. The area of the intersection provides a numerical value for measuring the effective interaction. A comparison of the areas for different temperature histories defines an index, or yardstick, for quantitatively assessing the effects of temperature variations on phenological shifts.     

Influence of bacteria and salinity on diatom biogenic silica dissolution in estuarine systems

Dissolution of diatom biogenic silica (bSiO₂) in estuaries and its control by water salinity and bacteria were investigated using the river euryhaline species Cyclotella meneghiniana as a model. Laboratory-controlled bioassays conducted at different salinities with an estuarine bacteria inoculum showed a faster dissolution of diatom bSiO₂ at the lowest salinity where bacteria were the most abundant. However in another experiment, salinity increase clearly enhanced the dissolution of cleaned frustules (organic matter free). The presence of active bacteria might therefore predominate on the effect of salinity for freshly lysed diatoms whereas salinity might rather control dissolution of organic-matter-free frustule remains. Incubation of cultivated diatoms at different protease concentrations revealed that high proteolytic activities had little effect on bSiO₂ dissolution at a 1-month scale in spite of an efficient removal of organic matter from the frustules. Altogether it is hypothesized that bacterial colonization increases bSiO₂ dissolution by creating a microenvironment at the diatom surface with high ectoproteolytic activity but also via the release of metabolic byproducts since the presence of organic matter seems generally to facilitate diatom bSiO₂ dissolution.     

Impact of nitrogen and climate change interactions on ambient air pollution and human health

Nitrogen oxides (NO_x) are important components of ambient and indoor air pollution and are emitted from a range of combustion sources, including on-road mobile sources, electric power generators, and non-road mobile sources. While anthropogenic sources dominate, NO_x is also formed by lightning strikes and wildland fires and is also emitted by soil. Reduced nitrogen (e.g., ammonia, NH₃) is also emitted by various sources, including fertilizer application and animal waste decomposition. Nitrogen oxides, ozone (O₃) and fine particulate matter (PM_2.5) pollution related to atmospheric emissions of nitrogen (N) and other pollutants can cause premature death and a variety of serious health effects. Climate change is expected to impact how N-related pollutants affect human health. For example, changes in temperature and precipitation patterns are projected to both lengthen the O₃ season and intensify high O₃ episodes in some areas. Other climate-related changes may increase the atmospheric release of N compounds through impacts on wildfire regimes, soil emissions, and biogenic emissions from terrestrial ecosystems. This paper examines the potential human health implications of climate change and N cycle interactions related to ambient air pollution.     

Effects of egg removal on maternal aggression, biogenic amines, and stress indicators in ovigerous lobsters (Homarus americanus)

In many disparate taxa, including crayfish, a freshwater decapod crustacean, the presence of one's offspring has been shown to be an important variable in the level of maternal aggression. Ovigerous American lobsters (Homarus americanus) show a territorial advantage against nonmaternal females, even though no posthatch care is provided. The eggs are attached to the pleopods (swimmerets) throughout embryogenesis. We evaluated the effect of stripping ovigerous H. americanus females of their eggs on maternal territoriality. In one treatment group, maternal females were stripped of all eggs. Twelve days later, including being individually isolated for an additional 48 h in a test tank, each resident was serially intruded upon by 4 non-maternal conspecific females. An identically treated control group of ovigerous female residents was left intact prior to the serial intrusions. Various biochemical parameters of the stripped and unstripped animals were measured before and after the experimental treatment (or control). The behavioral modulators measured were the biogenic amines, octopamine and serotonin, and the stress indicators were a heat-shock protein (HSP70), methyl farnesoate, and crustacean hyperglycemic hormone. The intact ovigerous residents showed a significant territorial advantage over the intruders, whereas the contest outcomes of stripped residents were reduced to chance. The presence of eggs in maternal H. americanus is therefore necessary for the maintenance of the shelter-related territorial advantage. However, no significant differences in any of the biochemical parameters were observed between or within treatment conditions. It appears that these amines are not prominently involved in the mechanism of maternal aggression, and that these changes in territorial defense are not simply due to changes in general stress as a result of stripping the females of their eggs.     

Brain glucose and insulin: effects on food intake and brain biogenic amines of rainbow trout

The effects of central (intracerebroventricular, 9 g fish^–1) and peripheral (intraperitoneal, 4 mg kg^–1) administration of bovine insulin, as well as the effect of hyperglycemia (oral administration of 1 g glucose fish^–1) and brain glucodeprivation (intracerebroventricular administration of 2-deoxy-D-glucose) on food intake and levels of brain (telencephalon, preoptic area, and hypothalamus) biogenic amines (serotonin, dopamine, noradrenaline and their metabolites 5-hydroxyindoleacetic acid, and dihydroxyphenylacetic acid) were assessed on rainbow trout (Oncorhynchus mykiss). Treatment with insulin inhibited food intake after 26 or 52 h of administration, central or peripheral, respectively. This effect was still apparent after 74 h of central treatment. When assessing changes in the levels of biogenic amines after 26 h of central insulin administration, there was a significant increase in the levels of 5-hydroxyindoleacetic acid, and in the ratio of dihydroxyphenylacetic acid/dopamine of insulin-treated fish, in telencephalon and hypothalamus, respectively. These results suggest that peripherally administered insulin is involved in a feedback regulatory loop with food intake and body weight. Moreover, at least part of the effects of insulin could be mediated by hypothalamic dopaminergic activity. The strong hyperglycemia induced by oral administration of glucose did not induce significant changes either on food intake (control versus treated), or in brain levels of biogenic amines. The intracerebroventricular administration of 2-deoxy-D-glucose induced an increase in food intake without altering plasma glucose levels, suggesting that fish brain possesses a control system for detecting hypoglycemia in plasma and therefore keep brain glucose levels high enough for brain function.Abbreviations 2-DG 2 Deoxy-D-glucose - 5-HIAA 5-Hydroxyindoleacetic acid - 5-HT 5-Hydroxytryptamine or serotonin - DA Dopamine - DOPAC Dihydroxyphenylacetic acid - EDTA Ethylenediaminetetraacetic acid - FI Food intake - HPLC High pressure liquid chromatography - icv Intracerebroventricular - i.p. Intraperitoneal - MS 222 3-Aminobenzoic acid ethyl esther methanesulfonate salt - NA Noradrenaline     

Health status of Pomatoschistus microps populations in relation to pollution and natural stressors: implications for ecological risk assessment

Effects induced on wild populations by recurrent environmental contamination may difficult the ecological risk assessment of punctual pollution events such as oil spills. Here, the issue was addressed by comparing the health status of Pomatoschistus microps populations from four NW Iberian estuaries, using an integrated chemical–biological monitoring. Despite high seasonal variability, the parameters measured discriminated estuaries with different contamination levels and associated biological effects with chemical and abiotic stress. The decreased health status of fish from polluted sites strengthens the need of considering pollution-induced background effects and seasonal variability when assessing impacts and risks of oil and other chemical spills.     

Interplay of JH, 20E and biogenic amines under normal and stress conditions and its effect on reproduction

Juvenile hormone (JH) and 20-hydroxyecdysone (20E) are well known to play a gonadotropic role in adult insects. In Drosophila the mechanism of reciprocal regulation of JH and 20E is shown to be responsible for their proper balance. Dopamine is a mediator in this JH and 20E interplay. A proper balance between JH and 20E is crucial for the normal progress of oogenesis. An imbalance of gonadotropins leads to reproductive defects: a rise in JH titre leads to oviposition arrest, a rise in 20E level, to the degradation of vitellogenic oocytes. Upon a change in the level of one of the gonadotropins, the balance is restored owing to the relative change in the titre of the other.     

Consequences of renal mass reduction on amino acid and biogenic amine levels in nephrectomized mice

Summary. Amino acid and biogenic amine changes were investigated in nephrectomized mice ten days postsurgery. Uremic mice exhibited changes in amino acid concentrations in plasma, urine and brain. Particularly plasma methionine, citrulline and arginine levels were significantly enhanced in nephrectomized mice compared to controls whereas serine was decreased. Urinary excretion of methionine, citrulline and alanine was higher in nephrectomized mice compared to controls whereas many amino acids were increased in brain of nephrectomized mice. Brain and urinary amino acid changes were more pronounced in the 75% than in the 50% nephrectomized mice. Brain norepinephrine and dopamine and its metabolites 3,4-dihydroxyphenylacetic acid and homovanillic acid were significantly increased whereas serotonin was decreased comparing the 75% nephrectomized mice to the sham-operated mice. This study demonstrates that at very early stages of renal insufficiency, specific amino acid and biogenic amine changes occur in plasma, urine and brain. These alterations might depend qualitatively and quantitatively on the degree of functional renal mass reduction. Received April 5, 1999     

Bridging the gap between micro - and macro-scale perspectives on the role of microbial communities in global change ecology

In order to understand the role microbial communities play in mediating ecosystem response to disturbances it is essential to address the methodological and conceptual gap that exists between micro- and macro-scale perspectives in ecology. While there is little doubt microorganisms play a central role in ecosystem functioning and therefore in ecosystem response to global change-induced disturbance, our ability to investigate the exact nature of that role is limited by disciplinary and methodological differences among microbial and ecosystem ecologists. In this paper we present results from an interdisciplinary graduate-level seminar class focused on this topic. Through the medium of case studies in global change ecology (soil respiration, nitrogen cycling, plant species invasion and land use/cover change) we highlight differences in our respective approach to ecology and give examples where disciplinary perspective influences our interpretation of the system under study. Finally, we suggest a model for integrating perspectives that may lead to greater interdisciplinary collaboration and enhanced conceptual and mechanistic modeling of ecosystem response to disturbance.     

Effects of drought on fish across axes of space, time and ecological complexity

• 1 We evaluate the position of 50 previously published studies of fish and drought with respect to spatial scale of study (individual stream pools to subcontinents), length of the dry period (weeks to centuries), and level of system complexity (individual fish to ecosystems). Most papers address short (months to a year) droughts or dry periods, in local reaches of streams, and impacts on populations or local assemblages. In these 50 papers, the most frequently demonstrated effects of drought were population declines, loss of habitat, changes in the community, negative effects from changes in water quality, movement within catchments, and crowding of fish in reduced microhabitats. Thirteen other less frequent effects also were identified.
• 2 Gaps in knowledge exist on effects of long‐term droughts (decades to centuries), influence of drought on fish effects in ecosystems, and at the spatial scale of river basins to subcontinents. However, some of these gaps have recently been addressed, particularly additive effects of repeated drying episodes and whole‐lake or basin‐wide effects of drought, and in using molecular techniques to seek signals of drought at wide geographic scales because of events in the deep past. Gaps in knowledge remain for effects of very short dry periods, on drought effects on higher levels of complexity, and on the manner in which droughts at the scale of decades affect fish.
• 3 Data from streams in Oklahoma and elsewhere in the south‐western U.S.A. suggest that most droughts may leave little persistent signal in the existing fish fauna, i.e. that recovery from drought by fish populations or assemblages in the region can be rapid. However, species that are vulnerable to drought or water loss in streams may have disappeared from some basins in the region before the mid‐1900s, and recent evidence also suggests that extreme droughts do sometimes alter fish assemblages.
• 4 Little is known about mechanisms by which droughts have direct or indirect effects on fish, the roles of droughts in the evolution of fish species, and the ways droughts alter effects of fish in ecosystems. Global climate changes may have serious consequences for future local or regional fish faunas, but ongoing studies of fish experiencing drought may aid in future conservation of what will become species at risk under climate‐change scenarios.