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PubMed1990

Malaria as anthropo-ecosystem (MAES): Part V. Self-regulation and stability of MAES.

In biological ecosystems, population tends to fluctuate above or below asymptotic level or the 'carrying capacity'. Self-regulation is achieved by extrinsic, that is, environmental limiting factors and intrinsic, that is, physiological and genetic factors. In Malaria Anthropo-Ecosystem (MAES) which is much more intricate and complex system, Plasmodium being endoparasite is required not only to interact with intrinsic factors of its vertebrate and invertebrate host but also to regulate itself to environmental factors to which its both the hosts are subjected. Attempt has been made to provide, on the basis of present knowledge, the probable explanation of self-regulatory mechanisms from molecular, cell, organ/organism, population/community levels of vertebrate and invertebrate hosts which give stability to MAES as a whole system.

Animals↗

PubMed1976

Laboratory model ecosystem evaluation of the chemical and biological behavior of radiolabeled micropollutants.

A standardized laboratory model ecosystem has been used to evaluate the comparative behavior of radiolabeled micropollutants including organochlorine, organophosphorus, carbamate, and hormone-mimic insecticides; herbicides; important industrial organic compounds including phthalate esters and PCB's; and specific pollutants such as TCBD and hexachlorobenzene. The compounds have been studies for ecological effects over a terrestrial-aquatic interface and through several food chains, especially with regard to the development of quantitative information on ecological magnification and biodegradability index. The pathways of chemical degradation in the various organisms have been evaluated and the ecological effects of degradation products investigated. Illustrations are given of the use of the model ecosystem technology for screening new candidate pesticides for effects on environmental quality; for evaluating the hazards of environmental pollution by industrial waste effluents; and for fundamental studies of the principles fo biodegradability of organic chemicals in a variety of organisms.

Animals↗

PubMed1989

Ecosystemic approach to contact dermatitis.

Contact dermatitis is looked upon as an ecosystem, including the allgergens from environment and the mechanisms of contact sensitivity. The methods of investigation and the indirect immunological tests are methodologically discussed by ecosystemic approach.

Allergens↗

PubMed1989

Malaria as anthropo-ecosystem. Part III: Diversity of MAES.

Diversity being one of the main characteristics of Malaria Anthropo-Ecosystem (MAES) is reflected in time and space. Temporal diversity of MAES generally may be divided into two types--long time periods usually on a global scale, and various local fluctuations expressed as malaria periodicity. Geographical confinement of MAES is determined by interactions of various elements of the latter with biotic and abiotic components of the environment. The diversity of the MAES within climatic zones of South and South-East Asia is shown to be of many types of sub-systems depending, apart from climatic conditions, on types of human activity in those ecosystems.

Animals↗

PubMed2026

Global Patterns of Net Ecosystem Exchange in peatlands: A Systematic Review and Meta-analysis of Drivers Across Land Use and Environmental Gradients.

Peatlands play an essential role in the global carbon cycle, storing approximately one-third of the world's soil carbon despite covering less than 3% of the land surface. Peatland degradation from anthropogenic activities and climate change can convert peatlands from net carbon sinks to sources by altering carbon cycling. Net Ecosystem Exchange (NEE), the balance between CO2 uptake and emission, is a critical indicator for assessing peatland condition and restoration efforts. We conducted a systematic quantitative literature review to investigate global patterns of NEE in peatlands and identify key environmental and anthropogenic drivers of CO2 flux variability. Annual NEE values from 120 globally distributed sites reported in peer-reviewed literature were analyzed in relation to climatic zone, land use, vegetation type, peatland condition, and water table depth. Our synthesis revealed significant geographic gaps, with peatland NEE studies substantially underrepresented in the Tropics, Africa, and Oceania. Agricultural peatlands emitted significantly more CO2 than sites under natural land uses or peat extraction, while degraded peatlands were significantly greater net CO2 sources than intact and restored systems. Restored peatlands remained net CO2 sources on average, emphasizing the importance of long-term monitoring and adaptive management following restoration interventions. Water table depth significantly affected NEE variability, with CO2 emissions increasing approximately 7.2 gCO2-C m-2yr-1 for every centimeter of water table drawdown. A substantial variability in measurement methods, data processing software, and protocols highlighted the critical need for methodological standardization. Our findings provide evidence-based targets for peatland conservation and restoration monitoring as nature-based climate solutions.

Ecosystem↗

PubMed1996

Lipid biomarkers for bacterial ecosystems: studies of cultured organisms, hydrothermal environments and ancient sediments.

This paper forms part of our long-term goal of using molecular structure and carbon isotopic signals preserved as hydrocarbons in ancient sediments to improve understanding of the early evolution of Earth's surface environment. We are particularly concerned with biomarkers which are informative about aerobiosis. Here, we combine bacterial biochemistry with the organic geochemistry of contemporary and ancient hydrothermal ecosystems to construct models for the nature, behaviour and preservation potential of primitive microbial communities. We use a combined molecular and isotopic approach to characterize lipids produced by cultured bacteria and test a variety of culture conditions which affect their biosynthesis. This information is then compared with lipid mixtures isolated from contemporary hot springs and evaluated for the kinds of chemical change that would accompany burial and incorporation into the sedimentary record. In this study we have shown that growth temperature does not appear to alter isotopic fractionation within the lipid classes produced by a methanotropic bacterium. We also found that cultured cyanobacteria biosynthesize diagnostic methylalkanes and dimethylalkanes with the latter only made when growing under low pCO2. In an examination of a microbial mat sample from Octopus Spring, Yellowstone National Park (USA), we could readily identify chemical structures with 13C contents which were diagnostic for the phototrophic organisms such as cyanobacteria and Chloroflexus. We could not, however, find molecular evidence for operation of a methane cycle in the particular mat samples we studied.

Alkanes↗

PubMed1996

Phylogenetic perspective on microbial life in hydrothermal ecosystems, past and present.

Understanding hydrothermal ecosystems, both past and present, requires basic information on the types of organisms present. Traditional methods, which require cultivation of microorganisms, fail to detect many taxa. We have used phylogenetic analyses of small subunit rRNA sequences obtained from microorganisms of a hot spring in Yellowstone National Park to explore the archael (archaebacterial) diversity present. Analysis of these sequences reveals several novel groups of archaea, greatly expanding our conception of the diversity of high temperature microorganisms, and demonstrating that hydrothermal systems harbour a rich variety of life. Many of these groups diverged from the archael line of descent early during evolution, and an understanding of their common properties may assist in inference of the nature of the last common ancestor of all life. The data also show a specific relationship between low-temperature marine archaea and some hot spring archaea, consistent with a thermophilic origin of life. Future use of rRNA-sequence-based techniques in exploration of hydrothermal systems should greatly facilitate study of modern thermophiles and give us insight into the activities of extinct communities as well.

Archaea↗

PubMed1996

High temperature ecosystems and their chemical interactions with their environment.

Phototrophic thermal ecosystems consist of microbial mats whose composition is largely determined by water temperature, dissolved oxygen, sulfide and pH. Mats exposed to sunlight consist of an upper zone of phototrophic bacteria and cyanobacteria and an undermat of heterotrophic bacteria. There is little or no net accumulation of reduced carbon and a quasi-equilibrium is established between the synthesis and oxidation of reduced carbon. The flux of carbon and other metabolites induces chemical change in the interstitial water which may assist the deposition of hydrothermal minerals. Uptake of carbon dioxide by phototrophs is favourable to calcium carbonate (travertine) deposition. Thermal systems also contain a range of chemolithotrophs and sulfate reducers potentially capable of depositing carbonate. Acid production by sulfate reducers may have the ability to precipitate silica from alkaline thermal waters but has not yet been demonstrated in vivo. Deposition of thermal ochre is also possible via bacterial oxidation of reduced iron and manganese. It appears that bacteria play a minor role in the deposition of hydrothermal minerals through chemical interaction. However, they may play a more important physical role by providing a large surface are suitable for mineral nucleation. If hydrothermal deposits occur on Mars, the distribution of travertine is likely to be restricted if there is a lack of pre-existing sedimentary carbonate. Less biologically interactive deposits of silica and ochre may predominate.

Archaea↗

PubMed1996

Ancient hydrothermal ecosystems on earth: a new palaeobiological frontier.

Thermal springs are common in the oceans and on land. Early in the history of the Earth they would have been even more abundant, because of a higher heat flow. A thermophilic lifestyle has been proposed for the common ancestor of extant life, and hydrothermal ecosystems can be expected to have existed on Earth since life arose. Though there has been a great deal of recent research on this topic by biologists, palaeobiologists have done little to explore ancient high temperature environments. Exploration geologists and miners have long known the importance of hydrothermal systems, as they are sources for much of our gold, silver, copper, lead and zinc. Such systems are particularly abundant in Archaean and Proterozoic successions. Despite the rarity of systematic searches of these by palaeobiologists, already 12 fossiliferous Phanerozoic deposits are known. Five are 'black smoker' type submarine deposits that formed in the deep ocean and preserve a vent fauna like that in the modern oceans; the oldest is Devonian. Three are from shallow marine deposits of Carboniferous age. As well as 'worm tubes', several of these contain morphological or isotopic evidence of microbial life. The oldest well established fossiliferous submarine thermal spring deposit is Cambro-Ordovician; microorganisms of at least three or four types are preserved in this. One example each of Carboniferous and Jurassic sub-lacustrine fossiliferous thermal springs are known. There are two convincing examples of fossiliferous subaerial hydrothermal deposits. Both are Devonian. Several known Proterozoic and Archaean deposits are likely to preserve a substantial palaeobiological record, and all the indications are that there must be numerous deposits suitable for study. Already it is demonstrable that in ancient thermal spring deposits there is a record of microbial communities preserved as stromatolites, microfossils, isotope distribution patterns and hydrocarbon biomarkers.

Animals↗

PubMedDate not supplied

Senio river ecosystem: characterization and distribution of inorganic species in water and sediments.

Analytical results are reported for the determination of inorganic species in water and sediments sampled in the Senio river ecosystem. The species determined are Cu, Pb, Cd, Zn, Co, Cr, Ni, Fe, Mn, Hg, F-, Cl-, Br, NO3-, SO4-, Na+, K+, Ca++, Mg++, NH4+ in integrated water, and Cu, Pb, Cd, Zn, Co, Cr, Ni, Fe, Mn, Hg in sediments. For all the elements, in addition to detection limits, precision and accuracy are given: the former, expressed as relative standard deviation (sr), and the latter, expressed as relative error (e), were good, being in all cases lower than 6%. Limitedly to Cu, Pb, Cd and Zn a critical comparison with voltammetric measurements is also discussed.

Ecosystem↗

PubMed2006

Potential of the marine sponge Hymeniacidon perleve as a bioremediator of pathogenic bacteria in integrated aquaculture ecosystems.

The aim of this article is to investigate the potential of using sponges as a bioremediator to remove pathogenic bacteria in integrated aquaculture ecosystems. Using the inter-tidal marine sponge Hymeniacidon perleve as a model system, the ability of removing the most common pathogens Escherichia coli and Vibrio anguillarum II in aquaculture waters was screened in laboratory tests. In sterilized natural seawater (SNSW) supplemented with E. coli at (7.0-8.3) x 10(6) cells/mL, H. perleve can remove an average 96% of E.coli within 10.5 h at a filter rate of ca. (7.53-8.03) x 10(7) cells/h x g of fresh sponge in two independent tests. Despite the removal efficiency and filter rate are similar; the clearance rates (CR) vary significantly among individual sponge specimens and between two batches. For the tests on V. anguillarum II in SNSW, about 1.5 g fresh sponges can keep the pathogen growth under control at a lower initial density 3.6 x 10(4) cells/mL of 200 mL water volume. Further tests were done for 24 h using about 12 g fresh sponge in 2-L actual seawater collected from two aquaculture sites that have ca. eightfold difference in pathogenic bacteria load. The concentrations of E. coli, Vibrio, and total bacteria at 24 h in treatment groups were markedly lower, at about 0.9%, 6.2%-34.5%, and 13.7%-22.5%, respectively, of those in the control. Using a fluoresce stain 1,1'-dioctadecyl-3,3,3',3'-tetramethylindocarbocyanine perchlorate, E. coli, and V. anguillarum II cells were stained and fed to sponges in two independent tests. The confocal microscope observation confirmed that the sponges filtering-retained and digested these bacteria by phagocytosis.

Animals↗

PubMed2006

Characterisation of new strains of atrazine-degrading Nocardioides sp. isolated from Japanese riverbed sediment using naturally derived river ecosystem.

A Gram-positive bacterial strain able to degrade the herbicide atrazine was isolated using a simple model ecosystem constituted with Japanese riverbed sediment and its associated water (microcosm). Treatment of the water phase of the microcosm with 1 mg litre-1 [ring-14C]atrazine resulted in the rapid degradation of atrazine after a 10 day lag phase period. The [ring-14C]cyanuric acid formed was transiently accumulated as an intermediary metabolite in the water phase and was subsequently mineralised through triazine ring cleavage. Possible atrazine-degrading microbes suspended in the water phase of the microcosm were isolated by the plating method while rapid degradation of atrazine was in progress. Among the 48 strains that were isolated, 47 exhibited atrazine-degrading activity. From these 47 isolates, 12 strains that were randomly selected were found to identically convert atrazine to cyanuric acid via hydroxyatrazine. Polymerase chain reaction (PCR) amplification of the genes corresponding to atrazine degradation revealed that these strains at least carried the genes trzN (atrazine chlorohydrolase from Nocardioides C190) and atzC (N-isopropylammelide isopropyl amidohydrolase from Pseudomonas ADP). Physiological characteristics and 16S rDNA partial sequences of six strains that were further selected strongly suggested that all these isolates originated from the same Nocardioides sp. strain. Additionally, only one isolate could mineralise the triazine ring of cyanuric acid. Based on microscopic observations, this strain appears to be a two-membered microbial consortium consisting of Nocardioides sp. and a Gram-negative bacterium. In conclusion, atrazine biodegradation in the microcosm appeared to occur predominantly by Nocardioides sp. to yield cyanuric acid, which could be mineralised by the other relatively ubiquitous microbes.

Actinomycetales↗

PubMedDate not supplied

Following sustainable development in relation to the north-south dialogue: ecosystem health and sustainability indicators.

The necessity for policy makers to follow the processes in relation to sustainability demands new tools for management, a major aspect of which is integrated attention to economic and sociocultural influences together with environmental issues. North and South have specific positions and responsibilities with regard to sustainable development, and management tools--such as indicators--should reflect them. Because the North-South dialogue is changing, different approaches to deal with the relationships are needed (e.g., introduction of reciprocity, equity, and participation), while at the same time doing justice to the individual social, economic, and cultural characteristics of a country. Ecosystem health can be defined by requirements such as resilience, vigor, organization, and relations, which may be used for totally different systems as well. Because integration is a crucial aspect of the new tools, it is argued that integrating conceptual tools such as the environment-economy-society triangle, the PSIR-causality chain, and the Daly triangle in addition to other described integration tools is fundamental for decision makers. Crucial issues when dealing with indicators for sustainable development are integration and balance, attention to users, use of system characteristics, and understanding southern perspectives in this context.

Conservation of Natural Resources↗

PubMed2001

Enchytraeids as indicator organisms for chemical stress in terrestrial ecosystems.

This review article surveys the available data on enchytraeid sensitivity toward chemical stress, and the effects of chemical stress on enchytraeid communities in terrestrial ecosystems. The factors affecting bioavailability of stressors to enchytraeids and the nature of direct and indirect effects that may occur are discussed, and the importance of laboratory tests and field studies for the evaluation of toxic effects is underlined. The existing data on specific types of stressors such as pesticides, metals, fertilizers, and industrial and domestic chemicals often show clear responses of enchytraeids, and in many cases interspecific differences in sensitivity are recorded. It is concluded that, although in several fields additional data are required, there are good perspectives for the use of enchytraeids as indicator organisms.

Animals↗

PubMed2002

Stoichiometry, herbivory and competition for nutrients: simple models based on planktonic ecosystems.

Models are examined in which two prey species compete for two nutrient resources, and are preyed upon by a predator that recycles both nutrients. Two factors determine the effective relative supply of the nutrients, hence competitive outcomes: the external nutrient supply ratio, and the relative recycling of the two nutrients within the system. This second factor is governed by predator stoichiometry--its relative requirements for nutrients in its own biomass. A model with nutrient resources that are essential for the competing prey is detailed. Criteria are given to identify the limiting nutrient for a food chain of one competitor with the predator. Increased supply of this limiting nutrient increases predator density and concentration of this nutrient at equilibrium, while decreasing the concentration of a non-limiting nutrient. Changes in supply or recycling of a non-limiting nutrient affect only the concentration of that nutrient. Criteria for the invasion of a second prey competitor are presented. When different nutrients limit growth of the resident prey and the invader, increased supply or recycling of the invader's limiting nutrient assists invasion, while increased supply or recycling of the resident's limiting nutrient hinders invasion. If the same nutrient limits both resident and invader, then changes in supply and recycling have complex effects on invasion, depending on species properties. In a parameterized model of a planktonic ecosystem, green algae and cyanobacteria coexist over a wide range of nitrogen:phosphorus supply ratios, without predators. When the herbivore Daphnia is added, coexistence is eliminated or greatly restricted, and green algae dominate over a wide range of supply conditions, because the effective supply of P is greatly reduced as Daphnia rapidly recycles N.

Animals↗

PubMed2002

Scaling of differentiation in networks: nervous systems, organisms, ant colonies, ecosystems, businesses, universities, cities, electronic circuits, and Legos.

Nodes in networks are often of different types, and in this sense networks are differentiated. Here we examine the relationship between network differentiation and network size in networks under economic or natural selective pressure, such as electronic circuits (networks of electronic components), Legos (networks of Lego pieces), businesses (networks of employees), universities (networks of faculty), organisms (networks of cells), ant colonies (networks of ants), and nervous systems (networks of neurons). For each of these we find that (i) differentiation increases with network size, and (ii) the relationship is consistent with a power law. These results are explained by a hypothesis that, because nodes are costly to build and maintain in such "selected networks", network size is optimized, and from this the power-law relationship may be derived. The scaling exponent depends on the particular kind of network, and is determined by the degree to which nodes are used in a combinatorial fashion to carry out network-level functions. We find that networks under natural selection (organisms, ant colonies, and nervous systems) have much higher combinatorial abilities than the networks for which human ingenuity is involved (electronic circuits, Legos, businesses, and universities). A distinct but related optimization hypothesis may be used to explain scaling of differentiation in competitive networks (networks where the nodes themselves, rather than the entire network, are under selective pressure) such as ecosystems (networks of organisms).

Animals↗

PubMed1999

The impact of rice pesticides on the aquatic ecosystems of the Sacramento River and Delta (California).

Since the early 1980s, when molinate was demonstrated to have killed carp in agricultural drains, an intensive research effort has been undertaken to assess the impact of rice pesticides on aquatic ecosystems in the Sacramento River and Delta. No impact has been found that can be clearly attributed to rice pesticides. However, the rice insecticides methyl parathion and carbofuran, and probably also bufencarb, reached levels in the River and Delta that, based on laboratory bioassays, would have been toxic to aquatic microinvertebrates and, in the case of bufencarb, to early life stages of striped bass. Reductions in microinvertebrate populations could have impacted higher organisms in the aquatic food chain such as striped bass and chinook salmon. Bufencarb was not used after 1981. Since then, changes in the management of the remaining rice pesticides have resulted in dramatic decreases in the levels of these chemicals in the River and Delta. Levels achieved today have no known toxicity to aquatic organisms. As releases of rice pesticides were reduced to achieve nontoxic levels in the River and Delta, however, commensurate recoveries of striped bass and chinook salmon did not occur, suggesting that rice pesticides may have had little or no role in the decline of these species.

Animals↗

PubMed1995

Ascomycetous yeast communities of marine invertebrates in a southeast Brazilian mangrove ecosystem.

The ascomycetous yeast communities associated with 3 bivalve mollusk, and 4 crab species were studied in the mangrove at Coroa Grande on Sepetiba Bay in Rio de Janeiro, Brazil. These were made up mostly of diverse but sparse and apparently allochtonous yeast populations. The striking exception was a prevalent population of the species Kluyveromyces aestuarii, which predominated the yeast communities of 2 detritus feeding crabs, Sesarma rectum and Uca spp., and the shipworm Neoteredo reynei. However, K. aestuarii was absent from the omnivorous crabs Aratus pisonii and Goniopsis cruentata, and the clam Anomalocardia brasiliana, and was rare in the clam Tagelus plebeius from mostly submerged more sandy sediments. Pichia membranaefaciens, Candida valida-like, Candida krusei, Candida sorbosa, Candida colliculosa-like, Candida famata-like, Kloeckera spp., Candida guilliermondii, Candida albicans, Candida silvae, Geotrichum spp., Rhodotorula spp., Cryptococcus spp., and the methylotrophic yeast Candida boidinii were frequently isolated. The 322 ascomycetous yeast cultures representing 252 isolates from crabs and mollusks were classified as 40 species that fit standard descriptions, and 44 putative new species. The ascomycetous yeast communities of the mangrove ecosystem include many new biotypes that require better taxonomic definition.

Animals↗