Microcosms as an Ecological Tool to Assess the Environmental Effect Caused by Introduced Species in Temporary Wetlands

Abstract

Microcosms are small-sized constructed ecosystems that are used as tool for ecological research focused in understanding natural ecosystem functioning and how human activities disturb some ecological processes at different spatial and temporal scales. The many major environmental changes in a system does not allow in fact performing experiments with microcosms, so that studies of trial and error are common and statistical analysis is through the theory of pseudo-experimentation. In this paper we describe different microcosm experiments used to examine the impact of introduced red swamp crayfish (Procambarus clarkii) at different densities in biological communities (aquatic macrophytes, algae and macroinvertebrates) in a temporary freshwater wetland. Through accumulation of data from five different the trials we could gain insight into the environmental impact of P. clarkii. Crayfish consume all type of macrophytes and algae, but especially the most abundant algae, Chara connivens. Final macroinvertebrates density (ind/liter) was reduced about 58% of the initial measure; the specific composition of the macroinvertebrates community also declined considerably as a result of the crayfish. Use microcosm for understanding the ecological functioning of aquatic systems subject to high environmental variations is very important, but it requires patience and dedication to complete them and have reliable results.