title: How realistic are outdoor microcosms? A comparison of the biota of microcosms and natural ponds.
abstract: This study investigated the extent to which aquatic plant and macroinvertebrate assemblages in small outdoor microcosms (cylinders 1.25-m diameter x 1.25 m deep) resembled assemblages found in natural ponds in Britain. Comparisons were made in terms of community structure, species richness, and numbers of uncommon species. Multivariate analysis indicated that, although the microcosms had no exact natural analogues, their plant and animal assemblages were most like those of deep, circumneutral ponds. Unlike natural ponds, the microcosms supported relatively species-poor invertebrate assemblages, lacking uncommon species. Among individual taxa, microcosms supported similar numbers of species of Gastropoda, Isopoda, Amphipoda, and Odonata as natural ponds but significantly fewer Coleoptera, Hemiptera, and Trichoptera species. This was most likely due to the absence of a shallow littoral area in the microcosms. Because of their vertical sides, the microcosms supported no marginal wetland plants, but submerged and floating-leaved plant assemblages were similar in community type and species richness to natural ponds. Refinements to microcosm and mesocosm designs are identified that would enable experimental systems to more closely replicate the assemblages found in natural ponds. In particular, the incorporation of natural margins would be likely to lead to experimental communities that were closer analogues of natural ponds.
authors.affiliation: Ponds Conservation Trust: Policy and Research, Oxford Brookes University, Headington, United Kingdom.
authors.forename: Penny
authors.initials: P
authors.lastname: Williams
authors.forename: Mericia
authors.initials: M
authors.lastname: Whitfield
authors.forename: Jeremy
authors.initials: J
authors.lastname: Biggs
authors.forename: Gill
authors.initials: G
authors.lastname: Fox
authors.forename: Pascale
authors.initials: P
authors.lastname: Nicolet
authors.forename: Nigel
authors.initials: N
authors.lastname: Shillabeer
authors.forename: Tom
authors.initials: T
authors.lastname: Sherratt
authors.forename: Phil
authors.initials: P
authors.lastname: Heneghan
authors.forename: Paul
authors.initials: P
authors.lastname: Jepson
authors.forename: Steve
authors.initials: S
authors.lastname: Maund
mesh_terms: D000818:Animals; D017753:Ecosystem; D005618:Fresh Water / Q000032:analysis*; D006863:Hydrogen-Ion Concentration; D007448:Invertebrates; D010944:Plants; D013045:Species Specificity; D006113:United Kingdom