Small-scale ecosystems

Small-scale freshwater toxicity testing is but a modest fraction of a diverse array of scientific activities connected to the field of ecotoxicology. Yet, within this still emerging discipline, few will argue the fact that tools and approaches developed to measure the undesirable effects that countless chemicals (alone or in mixtures) and complex (liquid and solid) media can exert on biota have markedly contributed to aquatic ecosystem preservation. Indeed, the breadth and scope of application of bioassays thus far directed toward obtaining relevant information aimed at problemsolving and prevention of contaminant-based issues has progressed well. 

Spatial variation in the abundance of electron donors and acceptors explains large-scale and small-scale patterns of anaerobic metabolism. Sulfate reduction dominates anaerobic carbon metabohsm on about two-thirds of the planet because of the high abundance of SO4 in seawater (Capone and Kiene, 1988). Fe(III) reduction is important in aU anaerobic ecosystems with mineral-dominated soils or sediments, regardless of whether they are marine or freshwater (Thamdrup, 2000). Methanogenesis is important in freshwater environments generally, and it dominates the anaerobic carbon metabolism of bogs, fens, and other wetlands that exist on organic (i.e., peat) soils. 

Transport of Organic and Inorganic Materials in Small-Scale Ecosystems... 

A small-scale ecosystem (research flume) has been used successfully to investigate the transport phenomena of radionuclides added as dissolved inorganics and to study and evaluate the parameters affecting a stream when it is subjected to organic stresses. 

Small-scale ecosystems are useful tools for simulating stream processes and evaluating the complex factors which interact with various pollutional stresses. 

The Biosphere II experiment is an interesting project from which we can learn a lot about Earth and its inhabitants. If nothing else, it has shown ns how complex Earth s ecosystems are and how difficult it is to mimic nature, even on a small scale. 

The differential sensitivity of aquatic species to surfactants (as illustrated in the toxicity ranges table) can lead to misinterpretations of the overall ecotoxicity of surfactants. Recent novel approaches have used small-scale ecosystems which are surveyed for the effects on a broader range of aqnatic organisms. This stategy, called mesocosm testing, has been nsed for a C12-13AE65 surfactant, and tests produced a mesocosm NOEC of 0.28 mg [29]. 

Yousef, Y. A., T. J. Padden, and E. F. Gloyna. 1975. Diurnal changes in radionuclides uptake by phytoplankton in small scale ecosystems. Water Res. 9(2) 181-187. 

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