Utilization of freshwater sponges in paleolimnological studies
Abstract Prior to the past decade, freshwater sponges had not been utilized in paleolimnological studies. There were valid reasons for this: the taxonomy of the spongillid freshwater sponges of the world was in complete disarray; the ecological parameters of freshwater sponge species either were not known or were presented in scattered publications that were not readily available to paleolimnologists. The revisionary work of Penney and Racek finally brought order into the chaos of spongillid systematics. Shortly after the appearance of the Penney-Racek landmark monograph, Poirrier, and later Harrison, described the ecological parameters of North American spongillid freshwater sponges in a series of species-by-species treatments. Racek, in a body of pioneering studies, evaluated spicular remains of freshwater sponges in cores dating to 30,000 yr B.P. from several lakes, i.e., Lake Huleh, Lago di Monterosi, Laguna de Petenxil, while Harrison and colleagues characterized the past history of Lake Okeechobee (3000–4000 yr B.P.) and of Serendipity Bog, Graham Island, British Columbia (9400-8500 yr B.P.) using spicular components. It is now evident that freshwater sponge skeletal and reproductive structures can be used to characterize accurately past ecological conditions of freshwater habitats. In this paper, I will introduce the reader to the pertinent literature in freshwater sponge taxonomy, will characterize spongillid species into broad groups based upon their environmental parameters, and will summarize present paleolimnological studies using freshwater sponge remains as a diagnostic tool.