Mesocosm studies

Schief J, Mutz M (2009) Effects of sudden flow reduction on the decomposition of alder leaves (Alnus glutinosa L (Gaertn.)) in a temperate lowland stream. A mesocosm study. Hydrobiologia 624 205-217... 

Considering evidence from both field and mesocosm studies, it may be concluded that certain groups of aquatic macroinvertebrates are sensitive to pyrethroids and that there can be changes, in the short term, at the population level and above with exposure to environmentally realistic concentrations of them. It should be possible to pick up effects of this kind in natural waters using ecological profiling, for example, the River Invertebrate Prediction and Classification System (RIVPACS). There is... 

Section 4.5). Of these, mesocosms have stimulated the greatest interest. In these, replicated and controlled tests can be carried out to establish the effects of chemicals upon the structure and function of the (artihcial) communities they contain. The major problem is relating effects produced in mesocosms to events in the real world (see Crossland 1994). Nevertheless, it can be argued that mesocosms do incorporate certain relationships (e.g., predator/prey) and processes (e.g., carbon cycle) that are found in the outside world, and they test the effects of chemicals on these. Once again, the judicious use of biomarker assays during the course of mesocosm studies may help to relate effects of chemicals measured by them with similar effects in the natural environment. 

Hendricks B, and 11 coauthors (2005) Dynamics of an oligotrophic bacterial aquifer community during contact with a groundwater plume contaminated with benzene, toluene, ethylbenzene, and xylenes an in situ mesocosm study. Appl Environ Microbiol 71 3815-3823. 

Several large-scale mesocosm studies were conducted with esfenvalerate, the most active form of fenvalerate (Fairchild et al. 1992 Heinis and Knuth 1992 Lozano et al. 1992 Webber et al. 1992). These investigators demonstrated that ... 

Stenalt, E., Johansen, B., Lillienskjold, S., and Hansen, B.W. Mesocosm study of Mytllus edulls larvae and postlarvae, including the settlement phase, exposed to a gradient of tributyltin, Ecotoxlcol Environ. Sal, 40(3) 212-225, 1998. 

However, the effect of a harmful compound should be studied with respect to the community level, not only for the organism tested. Tests with several species are realized in microcosm and mesocosm studies. Mesocosms are larger with respect to both the species number and the species diversity and are often performed outdoors and under natural conditions. 

In most cases, limited information is available regarding the toxic effects of chemicals. Empirical guidelines are then used in an attempt to protect most of the aquatic ecosystem s biota. The regulation of chemicals, for instance, generally uses safety factors from 10 to 1000 depending on the number of species tested. Mesocosm studies or comparisons with real field situations are accepted with lower safety factors on a case by case basis, since these studies reduce the uncertainty linked to the relevance of laboratory models in terms of site-specific data. 

Multispecies, microcosm, and mesocosm experiments Microcosm and mesocosm studies... 

Juttner I, Peither A, Lay JP, Kettrup A, Ormerod SJ. 1995. An outdoor mesocosm study to assess ecotoxicological effects of atrazine on a natural plankton community. Arch Environ Contam Toxicol 29 435-441. 

Mesocosm no-effect data on a rapidly dissipating compound such as a pyrethroid insecticide may not be suitable for a chronic EQS applied to a river. Furthermore, most existing micro- and mesocosm studies are inappropriate for EQS derivation if fish are the most sensitive species because fish have generally been excluded from such tests. There is consequently a need for evidence-based decision making for interpretation of nonstandard mesocosm studies. Microcosm and mesocosm tests can, however, be used directly for EQS derivation if algae, macrophytes, and invertebrates are appropriately represented in the test systems and if they concern substances subject to transient exposure. They are then directly applicable for the derivation of M AC-EQSs. For this purpose, the NOEAEC can be used as it represents the highest initial concentration that causes no ecologically relevant effects. 

Microcosm and mesocosm studies can be directly designed for the purpose of EQS derivation (e.g., the exposure scenario, communities to be monitored, etc.). Guidance for design and conduction of microcosm and mesocosm studies can be found in the references given for pesticide risk assessment, but OECD has recently published a guideline for a lentic field test that is not focused on pesticides alone (OECD 2006b). 

A variety of methods for validation of environmental standards can be used. The choice of the best method depends both on the standard and on the aspect that is to be validated. For example, mesocosm studies or other semiheld studies may be useful for validation purposes. The use of biomarkers may also help to generate confidence in a standard. Preferably, the standard itself should be validated, but often validation for methods is lacking. In these cases, one can decide to validate the separate building blocks of the standard-setting process. 

STUART R. BORRETT / Gaining integrated understanding of Phaeocystis spp. (Prymnesiophyceae) through model-driven laboratory and mesocosm studies 293-309... 

Brussaard CPD, Kuipers B, Veldhuis MJW (2005a) A mesocosm study of Phaeocystis globosa population dynamics - 1. Regulatory role of viruses in bloom. Harmful Algae 4 859-874... 

Brussaard CPD, Mari X, Van Bleijswijk JDL, Veldhuis MJW (2005b) A mesocosm study of Phaeocystis globosa (Prymnesiophyceae) population dynamics -II. Significance for the microbial community. Harmful Algae 4 875-893... 

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