Ecological field observations

A series of ecological field observations were carried out. Many different types of analyses were performed because the aim of this pilot study was to focus extra attention on this leg of the Triad. The selection of tests was based on the biological indicator for soil quality (BiSQ Schouten et al., 2000), comprising several microbial parameters (biomass, leucine and thymidine incorporation rate, potential carbon and nitrogen utilisation, microbial community structure), nematode community structure and species abundances, enchytraeid community structure 

Microtox (EC50 in % elutriate) (95% confidence interval) 182a, (11-2843) 106a (34-332) 76 (54-105) 

Extrapolated values (EC50 was not reached in undiluted sample). 

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In the practice of soil and sediment analysis, bioassays often are used in conjunction with chemical analysis and ecological field observations. This approach, named the TRIAD approach, was first introduced for sediment analysis by Chapman (1986) and is becoming more common for contaminated land assessment (Jensen and Mesman 2006). Such multimetric methods allow for reduction of uncertainties in risk assessment as evaluation is based on several independent lines of evidence (Chapman et al. 2002). 

TRIAD approach Integrated approach to determine ecological effects of pollution by a complex mixture, applying a combination of chemical analysis, bioassays, and ecological field observations. 

Studies conducted in the laboratory provide fundamental data on processes by which a pesticide is degraded and on its mobility. In combination with field observations, which integrate multiple processes, these data describe a pesticide s environmental fate. This section provides a discussion of several important specific analytical issues which should be considered in the design of environmental fate studies to ensure that the data generated address the needs of scientists and regulatory agencies for information on the environmental fate and environmental and ecological impacts of a pesticide to the fullest extent. 

Research on wild species in the temperate zones is limited by low species diversity and population density, but in tropical and subtropical areas cockroaches are surprisingly diverse, and valuable field observations in chemical ecology have been made in the tropics. Nevertheless, some temperate zone species, such as Parcoblatta in the New World and Ectobius in the Old, offer excellent opportunities for research under natural conditions. 

There are different, complementary approaches to assessing ecological risks of multiple stressors at the landscape level. The reductionist approach aims at identifying risks to populations and ecosystems of concern on the basis of accumulated data on simple stressor-effect relationships, and by identifying the main stressors of concern. This can be achieved by combining field observations and experimentation. Experimentation has the advantage of providing evidence of causation. 

Sources of data that might be used in the construction of stressor-response functions include the results of toxicity tests (lethal, chronic) performed under controlled laboratory conditions, direct measures of exposure and response in controlled field experiments, and the application of statistical relationships that estimate the biological effects of chemicals based on physical or chemical properties of specific toxicants. The order of preference among these sources of data lists field observations as the most valuable, followed by laboratory toxicity tests, and finally by the use of empirical relationships. In the absence of directly relevant data, the development of stressor-response functions may require the use of extrapolations among similar stressors or ecological effects for which data are available. For example, effects might have to be extrapolated from the available test species to an untested species of concern in an ERA. Similarly, toxicity data might be available only for a chemical similar to the specific chemical stressor of concern in an ERA, and thereby require an extrapolation from one chemical to another to perform the assessment. 

Ecological effects data may come from a variety of sources. Relevant sources of information include field observations (e.g., fish or bird kills, changes in aquatic community structure), field tests (e.g., microcosm or mesocosm tests), laboratory tests (e.g., single species or microcosm tests), and chemical structure-activity relationships. Available information on ecological effects can help focus the assessment on specific stressors and on ecological components that should be evaluated. 

Many factors can influence the utility of available ecological effects data for problem formulation. For example, the applicability of laboratory-based tests may be affected by any extrapolations required to specific field situations, while the interpretation of field observations may be influenced by factors such as natural variability or the possible presence of stressors other than the ones that are the primary focus of the risk assessment... 

Data from both field observations and experiments in controlled settings can be used to evaluate ecological effects. In some cases, such as for chemicals that have yet to be manufactured, test data for the specific stressor are not available. Quantitative structure-activity relationships (QSARs) are useful in these situations (Auer et al. 1990, Clements et al. 1988, McKim et al. 1987). 

There is a need for field experiments to complement general field observations and laboratory experiments on olfaction in mammals. Field experiments could include studying olfaction within the wider framework of ecological variation and adaptation. 

Ecological Parasitology. Ecological parasitologists investigate the role of parasites in nature. This includes making field observations of the various methods parasites use to survive in their environments and their ultimate effect on the evolution of species. 

Similarly, the reductions in toxicity observed in laboratory toxicity tests where exposure is modified (either through the addition of sediment or by removal to clean water) are also apparent in the field. Field effect concentrations are generally observed to occur at concentrations around three to ten times above those based on standard laboratory data. Dissipation and degradation are therefore clearly the critical factors in mitigating effects of pyrethroids under field conditions. This provides reassurance that preliminary ecological risk assessments based on... 

Giddings JM, Solomon KR, Maund SJ (2001) Probabilistic risk assessment of cotton pyrethroids in aquatic ecosystems 2. Aquatic mesocosm and field studies observed effects and their ecological significance. Environ Toxicol Chem 20 660-668... 

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