XVI International Botanical Congess

Two methods of studying submersed macrophytes are compared to determine their accuracy, consistency and variability. During two years of study, in-water censusing produced higher values of total species richness, mean species richness, mean stem densities and species frequency than did census data derived from boat surveys. Small species were particularly vulnerable to under-estimation in surveys conducted from a boat. In-water censusing was more consistent and displayed less variability in richness estimates. Although commonly used, sampling from a boat provides only a coarse estimation of submersed macrophyte community composition and structure and, therefore, is unsuitable for ecological studies of dynamic aquatic systems, especially where precise estimates and identification of rare species are essential.