Suitcase Sampler for Vegetation-Dwelling Aquatic Macroinvertebrates

Aquatic macrophytes play an important role in aquatic systems, providing shelter, breeding habitat, and food for fishes and aquatic macroinvertebrates, and serving as indicators of water and habitat quality. Quantitative sampling macrophytes and their associated macrofauna, however, is often difficult due to high plant densities and differences in macrophyte morphology. Since 1960, many lentic habitats in the southern U.S. have been invaded by hydrilla Hydrilla verticillata, an aggressive submerged macrophyte native to Asia. Hydrilla has become the dominant submerged macrophyte in the Atchafalaya Basin in southcentral Louisiana, and we are currently assessing the impacts of dense, virtually mono-specific hydrilla stands on water quality and macroinvertebrate distribution and abundance. As part of this study, we needed to develop an efficient, quantitative method of sampling macroinvertebrates in the dense canopy and understory habitats in littoral hydrilla beds. We devised a 60 x 45 cm suitcase trap constructed of 0.5-mm thick angle aluminum with 600-µ stainless steel mesh walls, and used it to collect vegetation-dwelling macroinvertebrates from May to September 2001. Results indicate the sampler is easy to deploy and retrieve, effective in all plant densities, permits estimation of macroinvertebrate densities by plant volume or dry weight, and is more effective than traditional net sweeps in describing the structure of the macroinvertebrate community.