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PubMed1984

The fate and impact of oil and oil-dispersant mixtures in freshwater pond ecosystems: introduction.

Oil and oil-dispersant mixtures were added to the surface waters of a series of man-made ponds. The fate of the oil and dispersant (Norman Wells crude and Corexit 9527 respectively) were studied as well as the impact of the added chemicals on the ponds' ecosystems. Elements of the ecosystems studied include bacteria, fungi, phytoplankton, periphyton , proto- and mesozooplankton , zoobenthos and surface insects. In addition a number of water quality parameters were regularly monitored. Comparisons were made between oil-treated and control ponds, as well as oil-dispersant treated and oil and/or control ponds. This paper describes the experimental set up and provides a summary of the findings reported in the following five papers.

Animals↗

PubMed1992

Arctic terrestrial ecosystem contamination.

Limited data have been collected on the presence of contaminants in the Arctic terrestrial ecosystem, with the exception of radioactive fallout from atmospheric weapons testing. Although southern and temperate biological systems have largely cleansed themselves of radioactive fallout deposited during the 1950s and 1960s, Arctic environments have not. Lichens accumulate radioactivity more than many other plants because of their large surface area and long life span; the presence and persistence of radioisotopes in the Arctic is of concern because of the lichen----reindeer----human ecosystem. Effective biological half-life of cesium 137 is reckoned to be substantially less than its physical half-life. The database on organochlorines in Canadian Arctic terrestrial mammals and birds is very limited, but indications are that the air/plant/animal contaminant pathway is the major route of these compounds into the terrestrial food chain. For terrestrial herbivores, the most abundant organochlorine is usually hexachlorobenzene followed by hexachlorocyclohexane isomers. PCB accumulation favours the hexachlorobiphenyl, pentachlorobiphenyl and heptachlorobiphenyl homologous series. The concentrations of the various classes of organochlorine compounds are substantially lower in terrestrial herbivore tissues than in marine mammal tissues. PCBs and DDT are the most abundant residues in peregrine falcons (a terrestrial carnivore) reaching average levels of 9.2 and 10.4 micrograms.g-1, respectively, more than 10 times higher than other organochlorines and higher than in marine mammals, including the polar bear. Contaminants from local sources include metals from mining activities, hydrocarbons and waste drilling fluids from oil and gas exploration and production, wastes from DEW line sites, naturally occurring radionuclides associated with uranium mineralization, and smoke containing SO2 and H2SO4 aerosol from the Smoking Hills at Cape Bathurst, N.W.T.

Animals↗

PubMed1995

The characterization of algal and microbial mucilages and their aggregates in aquatic ecosystems.

The mucilage 'phenomenon' of marine waters, a sporadic but massive accumulation of gelatinous material at and below the water surface, can create serious environmental and economic problems. To address these problems, we must understand better the causes of the phenomenon, its modulation by environmental factors and its adverse effects on ecosystems. In the context of an improved understanding, this brief review describes the means to characterize mucilage types and mucilage aggregates in their native condition, or as close to native as state-of-the-art technology will permit. Biological, chemical and physical factors interact to determine mucilage 'speciation' and thus the specific properties of mucilaginous materials. These factors and their interactions are described briefly in relation to the molecular biology of mucilage synthesis, the formation of submicroscopic 'particles' of mucilage and the morphology of mucilage aggregates. To facilitate current attempts to relate mucilage fine structure to the macroscale morphology of large aggregates (e.g., as found in the Adriatic Sea), attention will be focused on the 'fibril', a ribbon-like colloid rich in polysaccharide molecules. Such colloids (submicrometre particles) present many morphotypes which are identifiable by transmission electron microscopy; several fibril types appear as basic structural units in many kinds of mucilage aggregates in aquatic ecosystems. Attention will also be focused on (1) the problems of coping with analyzing mixtures of highly-hydrated, physically-unstable materials and (2) the detection, assessment and minimization of colloid instability artifacts which have confounded morphological analyses of mucilage aggregates in the past.

Adhesives↗

PubMed1994

A coupled carbon-water-energy-vegetation model to assess responses of temperate forest ecosystems to changes in climate and atmospheric CO2. Part I. Model concept.

Predictions of forest ecosystem response to changes in climate and atmospheric CO(2) concentration require hierarchically structured process models. Present forest simulation models have conceptual limitations that restrict their application to climate-change studies. A major drawback of forest succession models is that they often lack physiological details in the simulation of annual tree growth. On the other hand, aggregated ecosystem models assume spatially homogeneous forests, and do not account for successional changes in forest composition and canopy structure. The concept of a new coupled carbon-water-energy-forest vegetation model is presented which attempts to overcome the main limitations of existing models by implementing a modern view of ecological hierarchy and a robust approach for scaling ecological processes in space and time.

Journal Article↗

PubMed1994

Response of a grassland ecosystem to air pollutants: III--The chemical climate: Vertical flux densities of gaseous species in the atmosphere near the ground.

The establishment of element balances for ecosystems presupposes a knowledge of the amounts of the respective element exchanged between the ecosystem and the atmosphere near the ground by determining their vertical flux densities. Any adequate approach to calculate flux densities of gaseous species in the atmosphere has to use micrometeorological techniques. The authors applied the ratiometric method, which is described in detail. Results of flux density calculations for sulfur dioxide, nitrogen dioxide, nitric oxide and ammonia obtained during two years of measurement are discussed with regard to their role in element balances. Flux densities and deposition velocities of ozone are interpreted as functions of meteorological parameters as well as of the biological activity of the canopy. The latter is characterized by the flux density and flux-to-concentration ratio of carbon dioxide.

Journal Article↗

PubMed1995

Air quality and its possible impacts on the terrestrial ecosystems of the North American Great Plains: an overview.

Over the past several decades, numerous studies have been conducted on the impacts of air pollutants (air quality) on terrestrial ecosystems (crops and forests). Although ambient air is always composed of pollutant mixtures, in determining the relative air quality and its ecosystem impacts at a given geographic location and time, a predominant number of studies have shown that at the present time surface-level O(3) is the most important phytotoxic air pollutant. Within the North American Great Plains, the precursors for surface-level O(3) are mainly anthropogenic NO(x) and VOCs (volatile organic compounds). Texas and Alberta are the top regions of such emissions in the United States and Canada, respectively. This appears to be due mainly to the prevalence of natural gas and/or oil industry in the two regions and the consequent urbanization. Nevertheless, the total emissions of NO(x) and VOCs within the North American Great Plains represent only about 25-36% of the corresponding total emissions within the contiguous United States and the whole of Canada. Within the Great Plains many major crop and tree species are known to be sensitive to O(3). This sensitivity assessment, however, is based mainly on our knowledge from univariate (O(3) only) exposure-plant response studies. In the context of global climate change, in almost all similar univariate studies, elevated CO(2) concentrations have produced increases in plant biomass (both crop and tree species). The question remains as to whether this stimulation will offset any adverse effects of elevated surface O(3) concentrations. Future research must address this important issue both for the Great Plains and for all other geographic locations, taking into consideration spatial and temporal variabilities in the ambient concentrations of the two trace gases.

Journal Article↗

PubMed1992

Symbiotic interactions in the EVOLVE III ecosystem model.

Parasitic feeding mechanisms were introduced into the EVOLVE III ecosystem model. The modified system exhibited a number of interesting behaviors, including obligative and facultative parasitism, transient facultative mutualism and nonsymbiotic feeding. Speciation and massive die-offs were also observed. The introduction of a symbiotic capability altered the co-evolutionary development of traits that exhibited an arms race when the symbiotic capability was not present. Stable mutualisms were not possible in the present version of the model due to the restriction that organisms were not allowed to feed both on other organisms and from the environment at the same time. The ecosystem biomass increased with increased symbiotic activity. Biomass was influenced by the balance of virulence and resistance traits in the population and decreased as these traits became more disparate.

Animals↗

PubMed1991

Haemolysin occurrence among Aeromonas hydrophila, Aeromonas caviae and Aeromonas sobria strains isolated from different aquatic ecosystems.

A total of 909 Aeromonas spp. isolates from different aquatic ecosystems were tested for haemolysin production by both sheep and horse blood agar-plate assays and by rabbit erythrocytes in broth assay. A comparison of these different methods was undertaken in order to appreciate their capacity to evaluate the haemolytic activity of Aeromonas spp. isolated from aquatic ecosystems. The haemolytic activity was associated particularly with A. hydrophila and A. sobria (about 95% of strains), whereas A. caviae did not produce haemolysin (about 95% of strains). A method suitable for use in routine diagnostic microbiology laboratories is proposed for quantifying both groups of A. hydrophila/A. sobria and A. caviae in environmental water.

Aeromonas↗

PubMed2006

A failure of resilience: estimating response of New York City's public health ecosystem to sudden disaster.

Adapting methodology from resilience theory in ecology, we develop an empirical model of the response of the New York City public health ecosystem to sudden disaster. Contrary to cultural expectation, 'good' and 'bad' neighborhoods-starkly differentiated by public health status reflecting longstanding economic and racial segregation-respond similarly to challenge. This suggests that the difference in health between neighborhoods is primarily predicated on the extent to which they have been, and continue to be, exposed to differing patterns of stressors and affordances, rather than to any difference in underlying socio-economic vulnerability. Paradoxically, then, these urban neighborhoods constitute a single, highly interdependent, health ecosystem, despite substantial socioeconomic and racial segregation.

Disasters↗

PubMed2004

Ecosystem response to antibiotics entering the aquatic environment.

Awareness of antibiotics in wastewaters and aquatic ecosystems is growing as investigations into alternate pollutants increase and analytical techniques for detecting these chemicals improve. The presence of three antibiotics (ciprofloxacin, norfloxacin and cephalexin) was evaluated in both sewage effluent and environmental waters downstream from a sewage discharge. Bacteria cultured from the sewage bioreactor and receiving waters were tested for resistance against six antibiotics (ciprofloxacin, tetracycline, ampicillin, trimethoprim, erythromycin and trimethoprim/sulphamethoxazole) and effects of short term exposure (24 h) to antibiotics on bacterial denitrification rates were examined. Antibiotics were detected entering the sewage treatment plant with varying levels of removal during the treatment process. Antibiotics were also detected in effluent entering receiving waters and detectable 500 m from the source. Among the bacteria cultured from the sewage bioreactor, resistance was displayed against all six antibiotics tested and bacteria cultured from receiving waters were resistant against two of the antibiotics tested. Rates of denitrification were observed to decrease in response to some antibiotics and not to others, though this was only observed at concentrations exceeding those likely to be found in the environment. Findings from this preliminary research have indicated that antibiotics are entering our aquatic systems and pose a potential threat to ecosystem function and potentially human health.

Animals↗

PubMed2005

Fire as a global 'herbivore': the ecology and evolution of flammable ecosystems.

It is difficult to find references to fire in general textbooks on ecology, conservation biology or biogeography, in spite of the fact that large parts of the world burn on a regular basis, and that there is a considerable literature on the ecology of fire and its use for managing ecosystems. Fire has been burning ecosystems for hundreds of millions of years, helping to shape global biome distribution and to maintain the structure and function of fire-prone communities. Fire is also a significant evolutionary force, and is one of the first tools that humans used to re-shape their world. Here, we review the recent literature, drawing parallels between fire and herbivores as alternative consumers of vegetation. We point to the common questions, and some surprisingly different answers, that emerge from viewing fire as a globally significant consumer that is analogous to herbivory.

Journal Article↗

PubMed2001

Change in the concentrations of iron in different size fractions during a phytoplankton bloom in controlled ecosystem enclosures.

To observe micronutrient dynamics in the plankton ecosystem, controlled ecosystem enclosure (CEE) experiments were conducted in Saanich Inlet, B.C., Canada. Two CEEs (2.5 m in diameter, 16 m in length, one for Fe studies and the other for biological studies) were launched for the period 22 July to 5 August 1996 and enriched with 10 µM nitrate and 5.2 nM Fe (13% of total Fe) on day 1. Sampling from three integrated depths, intervals 0-4, 4-8 and 8-12 m, was performed on days 0, 1, 2, 3, 4, 5, 7, 9 and 11. Iron concentrations were measured for five size fractions: >25 µm particles, 2-25 µm particles, 0.2-2 µm particles, 0.2 µm-200 kDa small colloidal particles and <200 kDa soluble species. The sediment in the Fe enclosure was also collected on every sampling day after day 2 and its Fe was determined. Size-fractionated particulate organic carbon and total chlorophyll-a were also analyzed.The Fe in small colloidal particles (200 kDa-0.2 µm) comprised 78% of the traditionally defined dissolved phase (<0.2 µm) on day 1. Of all the size fractions of Fe, the small colloidal particulate fraction decreased most significantly during the phytoplankton bloom. In the dissolved fraction (<0.2 µm), the small colloidal particle fraction comprised 79% of the decrease. The decrease in concentration of Fe in small colloidal particles was larger than that of total Fe from day 1 to day 4. In contrast, the >25 µm Fe particles increased over the same period. These results suggest that Fe in small colloidal particles changed to >25 µm Fe particles during phytoplankton growth. A large amount of Fe was kept in the surface layer with the phytoplankton, and transported to the deep layer by phytoplankton sedimentation, at the end of the bloom. From these results, the small colloidal particulate Fe seems to be the most dynamic size fraction and a high percentage of Fe in small colloidal particles changed to large particles due to chemical/physical aggregation and/or physical adsorption to suspended particles such as phytoplankton cells.

Journal Article↗

PubMed2002

Could microbial symbionts of arthropod guts contribute significantly to nitrogen fixation in terrestrial ecosystems?

Fixed nitrogen is a limiting nutrient in most terrestrial ecosystems and has been assumed to be supplied almost entirely by free-living bacteria as well as by bacteria living in association with plants. The survival and growth of many arthropods on diets with extremely high carbon to nitrogen (C:N) ratios suggest that these arthropods are not obtaining sufficient nitrogen from their diets but must be obtaining additional nitrogen from some other source(s). Estimates of N(2) fixation have suggested that symbiotic microbes of some arthropod hindguts could be obtaining this additional nitrogen as a result of nitrogen fixation. With the recent availability of antibody and nucleic acid probes, the presence of the enzyme that reduces dinitrogen gas to ammonia (nitrogenase) as well as the presence of its transcripts can be detected and localized with great sensitivity. A preliminary survey of a few detritivores indicates that nitrogen-fixing microbes of diverse forms are widespread in arthropod hindguts. In calculating nitrogen budgets, the possible contributions of nitrogen fixation by symbionts in arthropod guts, however, has been largely ignored. N(2) fixation in arthropod guts, with rates as high as 10-40 kg/ha/year being possible, may represent a significant contribution both to the growth of arthropods and to their ecosystem functions of processing carbon and nitrogen.

Journal Article↗

PubMed1997

Indicators of the sustainability of heavy-metal management in agro-ecosystems.

The aim of sustainable heavy-metal management in agro-ecosystems is to ensure that the soil continues to fulfil its function in agricultural production, in environmental processes such as the cycling of elements, and as a habitat of numerous organisms. Assessment of sustainability has to be carried out in time, since metal accumulation in soil is largely irreversible and may cause problems if certain concentration levels are exceeded. In this study, we provide a concept to assess the sustainability of current metal cycles in agro-ecosystems based on dynamic heavy-metal balances for the plough layer. After presenting some general aspects of dynamic metal balances, we introduce 'sustainability indices'. These characteristic numbers can be used as indicators for potentially adverse effects of current agricultural practices, since they account for (ecotoxicologically founded) soil quality standards and for quality standards for produce, groundwater and surface water. They can also be used to assess the effects of different management options that aim to prevent quality standards from being exceeded as they provide insight in the dynamics governing input-output relationships. This is illustrated with a case study on heavy-metal flows in different arable farming systems.

Agriculture↗

PubMed2000

Heavy metal fluxes at the sediment-water interface of three coastal ecosystems from south-west of the Iberian Peninsula

Concentrations of the heavy metals Cr, Cu, Fe and Mn were measured in sediments and porewater samples collected in three coastal ecosystems southwest of the Iberian Peninsula: the Odiel and Barbate River Salt Marshes and the Bay of Cadiz. Both the sediment and the porewater metal concentrations in the Odiel River Salt Marshes are higher than the values found in the Bay of Cadiz and Barbate River Salt Marsh, particularly for copper, a metal associated with mining activity. In porewater, the profiles were not the same as those in the solid phase and reflect the different behaviours of the elements in relation to the redox conditions. The heavy metals Cr and Cu show a typical enrichment in the porewater of the oxic zone. The heavy metals Mn and Fe show an increase in the porewater at the depths where the maximum nitrate and phosphate concentrations occur, respectively. Significant differences between background levels for each heavy metal in the various studied zones exist. Iron and Cu showed larger background levels in the Odiel River Salt Marshes than those in the Cadiz Bay and the Barbate River Salt Marshes. In the Bay of Cadiz the background levels are also high, particularly for Cr. At the Odiel River Salt Marshes the diffusive flux of Cu is high (1.3-230.1 microg cm(-2) year(-1)), which suggests that the Odiel River Salt Marshes are subject to strong contamination by Cu, which is presumably introduced to the sediment in particulate form. In the Bay of Cadiz, Cr is the only metal with positive diffusive flux (2.15 microg cm(-2) year(-1)). It is higher than those obtained in other coastal ecosystems including the Odiel River Salt Marshes. The positive diffusive flux of Cr has been associated with the input of this metal by the naval industry and the manufacturing of car and aircraft components.

Journal Article↗

PubMed2001

The Martian and extraterrestrial UV radiation environment. Part II: further considerations on materials and design criteria for artificial ecosystems.

Ultraviolet radiation is an important natural physical influence on organism function and ecosystem interactions. The UV radiation fluxes in extraterrestrial environments are substantially different from those experienced on Earth. On Mars, the moon and in Earth orbit they are more biologically detrimental than on Earth. Based on previously presented fluxes and biologically weighted irradiances, this paper considers in more detail measures to mitigate UV radiation damage and methods to modify extraterrestrial UV radiation environments in artificial ecosystems that use natural sunlight. The transmission characteristics of a Martian material that will mimic the terrestrial UV radiation environment are presented. Transmissivity characteristics of other Martian and lunar materials are described. Manufacturing processes for the production of plastics and glass on the lunar and Martian surface are presented with special emphasis on photobiological requirements. Novel UV absorbing configurations are suggested.

Animals↗

PubMed1999

The Martian and extraterrestrial UV radiation environment--1. Biological and closed-loop ecosystem considerations.

The Martian surface is exposed to both UVC radiation (<280 nm) and higher doses of UVB (280-315 nm) compared to the surface of the Earth. Terrestrial organisms have not evolved to cope with such high levels of UVC and UVB and thus any attempts to introduce organisms to Mars, particularly in closed-loop life support systems that use ambient sunlight, must address this problem. Here we examine the UV radiation environment of Mars with respect to biological systems. Action spectra and UV surface fluxes are used to estimate the UV stress that both DNA and chloroplasts would experience. From this vantage point it is possible to consider appropriate measures to address the problem of the Martian UV environment for future long term human exploration and settlement strategies. Some prospects for improving the UV tolerance of organisms are also discussed. Existing artificial ecosystems such as Biosphere 2 can provide some insights into design strategies pertinent to high UV environments. Some prospects for improving the UV tolerance of organisms are also discussed. The data also have implications for the establishment of closed-loop ecosystems using natural sunlight on the lunar surface and elsewhere in the Solar System.

Animals↗

PubMed2001

Root dynamics in an artificially constructed regenerating longleaf pine ecosystem are affected by atmospheric CO(2) enrichment.

Differential responses to elevated atmospheric CO(2) concentration exhibited by different plant functional types may alter competition for above- and belowground resources in a higher CO(2) world. Because C allocation to roots is often favored over C allocation to shoots in plants grown with CO(2) enrichment, belowground function of forest ecosystems may change significantly. We established an outdoor facility to examine the effects of elevated CO(2) on root dynamics in artificially constructed communities of five early successional forest species: (1) a C(3) evergreen conifer (longleaf pine, Pinus palustris Mill.); (2) a C(4) monocotyledonous bunch grass (wiregrass, Aristida stricta Michx.); (3) a C(3) broadleaf tree (sand post oak, Quercus margaretta); (4) a C(3) perennial herbaceous legume (rattlebox, Crotalaria rotundifolia Walt. ex Gemel); and (5) an herbaceous C(3) dicotyledonous perennial (butterfly weed, Asclepias tuberosa L.). These species are common associates in early successional longleaf pine savannahs throughout the southeastern USA and represent species that differ in life-form, growth habit, physiology, and symbiotic relationships. A combination of minirhizotrons and soil coring was used to examine temporal and spatial rooting dynamics from October 1998 to October 1999. CO(2)-enriched plots exhibited 35% higher standing root crop length, 37% greater root length production per day, and 47% greater root length mortality per day. These variables, however, were enhanced by CO(2) enrichment only at the 10-30 cm depth. Relative root turnover (flux/standing crop) was unchanged by elevated CO(2). Sixteen months after planting, root biomass of pine was 62% higher in elevated compared to ambient CO(2) plots. Conversely, the combined biomass of rattlebox, wiregrass, and butterfly weed was 28% greater in ambient compared to high CO(2) plots. There was no difference in root biomass of oaks after 16 months of exposure to elevated CO(2). Using root and shoot biomass as a metric, longleaf pine realized the greatest and most consistent benefit from exposure to elevated CO(2). This finding suggests that the ability of longleaf pine to compete with sand post oak, a common deciduous tree competitor, and wiregrass, the dominant understory herbaceous species, in regenerating ecosystems may be significantly enhanced by rising atmospheric CO(2) concentrations.

Journal Article↗