Ecosystem level

Organisms evolving under aimual temperature cycles and in environments with varying temperatures spatially have incorporated thermal cues in reproductive behavior, habitat selection, and certain other features which act at the population level. Thus, the balance of births and mortaUties, which determines whether a species survives, is akin to the metaboHc balance at the physiological level in being dependent upon the match, within certain limits, to prescribed temperatures at different times of year. At the ecosystem level, relationships among species, eg, predators, competitors, prey animals, and plant foods, are related to environmental temperatures in complex ways. Many of these interactions are poorly understood. 

Figure 1. Conceptual model illustrating examples of major anthropogenic contaminant sources and contaminants, their distribution within the abiotic environmental media, their movement into biota with potential food chain contamination, and potential effects at the organismal, population, conmiunity and ecosystem level of organization.

Fairchild, J.F., T.W. La Point, J.L. Zajicek, M.K. Nelson, F.J. Dwyer, and P.A. Lovely. 1992. Population-, community- and ecosystem-level responses of aquatic mesocosms to pulsed doses of a pyrethroid insecticide. Environ. Toxicol. Chem. 11 115-129. 

Webber, E.C., W.G. Deutsch, D.R. Bayne, and W.C. Seesock. 1992. Ecosystem-level testing of a synthetic pyrethroid insecticide in aquatic mesocosms. Environ. Toxicol. Chem. 11 87-105. 

Indicators of microbial activity in soil represent measurements at the ecosystem level (e.g., processes regulating decomposition of organic residues and nutrient cycling, especially nitrogen, sulfur and phosphorus). Measurements at the community level include bacterial DNA and protein synthesis. Frequency of bacteriophages is a measurement at the population level. 

CLL approach and ecosystem, risk analysis. This approach provides insights on assessment and measurement endpoints for ecosystem-level EcoRA since it has a set of environmental criteria to detect the state of ecosystems critical load itself can be treated as a criterion for ecosystem sustainability (Bashkin, 2002). Moreover, one can derive spatial ecosystem risk estimates based on the percentage of ecosystems protected/potentially at risk under the current and predicted level of pollutant loads. 

There are a number of approaches to measuring risks depending on assessment and measurement endpoints selected. At ecosystem level, one can propose a percentage of the affected area with CLs exceeded as an acceptable quantitative parameter for ecosystem risk magnitude. In pristine areas, actual state of the environment may be taken as a reference point for risk characterization. 

Hay ME, Kubanek J (2002) Community and ecosystem level consequences of chemical cues in the plankton. J Chem Ecol 28 2001-2016... 

Risk assessment Some participants suggested that further development and validation of appropriate methods to assess the ecological risks of chemical agents are required. Dose-response curves should be established at the community and ecosystem levels. Several participants suggested that when applying for an exemption of chemicals according to the Stockholm Convention, China might need to support its application with risk-based analysis. 

A final assessment can conclude that organic farming creates "comparatively more favourable" conditions on the species and ecosystem level of floral and faunal diversity than conventional farming systems. This is due to a plant protection management (ban of synthetic pesticides) that is better for the biotic... 

Biodiversity can also be examined at ecosystem level. This is of special concern for ecology, because, although attention to ecological problems is increasing, the choice of the appropriate scale to look at the events is problematic (Levin 1999). The spatial and temporal scales needed are often of such large size to make any reliable observation difficult. This is especially true for the sea, due to the lack of barriers which, therefore, makes any subdivision into ecosystems difficult. This is why any quantitative evaluation of biodiversity at ecosystem level is far fi-om being an easy task. 

Part III. Natural product diversity at ecosystem level... 

---