One of the primary goals of forensic pathology is the determination of time of death. In aquatic systems, one method to do this is to analyze the colonization of a corpse by algae. Algal communities typically follow a serial colonization pattern; therefore, the taxa present at any given time may provide clues about postmortem submersion time. In the current study, two habitats were involved: a low flow pool and a high flow riffle, with rats being removed from each site every 3 to 6 days over 31 days. The diversity of colonizing taxa increased at both sites as the study progressed, and after 17 days similar taxa were present (Sorensen's similarity index > 60 percent) in each site. Some taxa, such as desmids (chlorophyta), tended to increase in diversity throughout the study, making them possible indicators of submersion time. Diatoms were the most abundant taxa found in each site and accounted for 63 of the 92 total taxa identified. Due to their ubiquitous presence in nearly all streams, the researchers suggest that diatoms may be the key organisms for the study of postmortem submersion in lotic systems. 4 tables, 2 figures, and 28 references