The Management ofTypha domingensis(Typhaceae) affects Macroinvertebrate Assemblages in the Palo Verde Wetland, Guanacaste, Costa Rica

Abstract

The Palo Verde wetland, one of the most important places for aquatic organisms in Costa Rica, is currently recovering from an invasive expansion of Typha domingensis (cattail). A monitoring program was designed to understand the potential impacts of different management plans on aquatic fauna and flora. Macroinvertebrates were sampled monthly for one year (Aug 2003–Aug 2004) using an artificial substrate method in three plots: Plot A, T. domingensis has been managed since 1987 by manual and mechanical underwater cutting and posterior grazing; Plot B, T. domingensis has been mechanically crushed since 2002; and Plot C, a homogeneous T. domingensis stand without active management. We identified 112 macroinvertebrate taxa from 53 families and 18 orders. Typha domingensis removal in plots under active management did not increase family or taxa richness. Instead, a greater number of rare taxa persisted in the unmanaged plot, and macroinvertebrate communities differed among plots with less than 60% of taxa shared among them. Furthermore, mean taxa richness was higher in T. domingensis cover (X = 8.56) than in the other vegetation covers (X = 4.6 to 5.54). Macroinvertebrate richness was affected by vegetation cover, sampling date, and depth while abundance was affected by depth and dissolved oxygen. Typha domingensis management is necessary to open areas that allow the development of other vegetation types, a variety of communities of macroinvertebrates, and habitat for birds. However, in order to promote a high macroinvertebrates biodiversity and ensure food sources for waterfowl, the Palo Verde wetland should retain some patches of T. domingensis distributed throughout.