Algal colonization of submerged carcasses in a mid-order woodland stream

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 colo nization of a corpse by algae. Algal communities typically follow a serial colonization pattern, therefore the taxa present at any given time may prov ide clues about postmortem submersion time. This study was undertaken to ex amine the algal colonization on rat carcasses in a medium-order woodland st ream. Two habitats were studied: a low flow pool and a high flow riffle, wi th rats being removed from each site every 3 to 6 days over 31 days. The di versity of colonizing taxa increased at both sites as the study progressed, and after 17 days similar taxa were present (Sorensen's similarity index > 60%) in each site. Some taxa, such as desmids (Chlorophyta), tended to incr ease 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, we suggest that diatoms may be the key orga nisms for the study of postmortem submersion in lotic systems.