The role of laboratory terrestrial model ecosystems in the testing of potentially harmful substances

Abstract

: A classification of terrestrial model ecosystems (TMEs) was introduced which is based upon the physical properties of intactness of the physical medium and openness to the atmosphere. This gave rise to four types of system, namely open and closed intact systems and open and closed homogeneous' systems. These systems have different capabilities with respect to fate and effect end-points with various substances. The large closed TMEs are generally very complex, require a high degree of operator skill, expensive and therefore not replicable. Whilst these can provide estimates of losses due to volatility, they are not useful for determining effect end-points because of low replicability; high replicability being necessary because of natural variation in organism response. Open systems, especially those having intact soil-cores, are usually smaller, less complex and therefore more replicable. These have provided useful information on integrative functional effect end-points, but can only produce mass balances with non-volatile substances. Homogenization of the medium has also helped elucidate ecotoxicological effects by increasing replicability, but may introduce artifacts because of the disruption to soil organisms.A major limitation of TME studies would seem to be that few effect end-points can be non-destructively sampled. Further investigations into these may provide information on recovery of terrestrial ecosystems over time after substance application, perhaps using multivariate statistical techniques. Other problems concerning TMEs are related to complexity and scale. In this respect ecosystem functions in which microorganisms play a major role, such as nutrient cycling, provide the greatest similarity when compared to field evaluations of the same substances, especially where the TME is intact. However, effects upon structural aspects of biological communities have in general not been well researched in TMEs. Once these have been added to the more complete set of functional end-points, TMEs will provide a very useful tool in hazard assessments of potentially harmful substances.

Ecotoxicological and Fertilizing Effects of Dewatered, Composted and Dry Sewage Sludge on Soil Mesofauna: A TME Experiment

“…However, these tests are performed under specific field conditions and the results are not easily transferable to other geographic areas. Mesocosms or ''Terrestrial Model Ecosystems'' (TMEs) are being used as a compromise alternative between microcosms and field methodologies (Anderson, 1978;Ha˚gvar, 1988;Mothes-Wagner et al, 1992;Teuben and Verhoef, 1992;Morgan and Knacker, 1994;Burrows and Edwards, 2004;Fo¨rster et al, 2004;Knacker et al, 2004;Koolhaas et al, 2004).…”

Effects of Organic Pesticides on Enchytraeids (Oligochaeta) in Agroecosystems: Laboratory and Higher-Tier Tests

“…When all components of such a microcosm (including organisms) are selected by the experimenter, they are called gnotobiotic systems (gnotos (gr.) = known) (Mothes-Wagner et al, 1992;Born, 1993;Morgan and Knacker, 1994;Scott-Fordsmand et al, 2008;Schaeffer et al, 2010). The earliest known example is a study in Azalea cultures with various stressors, e.g., the herbicide DBCP (e.g., Heungens, 1968).…”

A farewell to Dr Thomas Knacker (* 29.04.1951 – † 30.10.2011): scientific contributions and personal memories

“…Although Thomas was formally responsible for aquatic ecotoxicology at ECT GmbH, his research interests were much broader [4][5][6][7]. His influence was probably most visible in the environmental risk assessment of chemicals [8][9][10], such as their regulation in the marine environment (OSPAR process), the effects of endocrine disruptors [11,12] or their testing in higher-tier studies, especially Terrestrial Model Ecosystems (TMEs) [13][14][15].…”