A Limnological Investigation of the Microbiota of an Illinois Pond

This study entailed an intensive one-year limnological investigation of the microbiota of a small Illinois pond with emphasis on physico-chemical interrelations and physico-chemical vs. organismal interactions. The numbers of organisms/liter belonging to a given taxon were determined, and these data were related to the physico-chemical data at a given time by means of multiple regression programs. Most phytoplankton populations were correlated with nitrate-nitrogen and water temperature. Less frequent negative correlations were observed with ammonia-nitrogen and nitrite-nitrogen, and positive or negative correlations occurred with total alkalinity. Diatoms were the first phytoplankters to produce a spring bloom. They were followed by desmids and other green algae. The presence of ciliate Protozoa usually was not correlated with any specific physico-chemical factor, lending credence to the supposition that their numbers and species composition are controlled by the presence and abundance of particulate food material. Several species belonging to the same genus, e.g., Euglena spp. and Vorticella spp., were present at the same time in samples collected from the pond. Intensive long-term sampling presented a panorama of the changes occurring in taxon composition and numbers of organisms within a period of several days and throughout the year. Sudden fluctuations in population size and taxon presence reemphasized the need for such intensive sampling during the studies of the interrelationships between taxa and the physico-chemical factors producing changes in the population density of the affected taxa.