Among all eukaryotic organisms, the diversity of microscopic algae is perhaps the least understood. Yet coccoid algae are extremely important primary producers in many freshwater systems. It has been demonstrated that Chlorella sp. contributes over 70% of the total carbon fixed in some lakes. It is estimated that as many as 1 million species of algae remain to be discovered. This problem is probably most acute for the unicellular autosporic coccoid algae, where a lack of morphological characteristics has severely hampered species identification. These algae are all nearly spherical in shape, lack any flagellate stage, and do not sexually reproduce. Coccoid algae that are green in color and represent at least three evolutionarily divergent types of organisms; xanthophytes (Xanthophyceae), eustigmatophytes (Eustigmatophyceae), and green algae (Chlorophyta). These organisms can not be distinguished from each other (even at the class level) by light microscopy and thus have typically been identified as "little green balls", or (usually incorrectly) Chlorella spp. Coccoid algae are present in high numbers in oligotrophic, mesotrophic, eutrophic, and dystrophic lakes. However, because the organisms have not been identified, studies of the coccoid algae have been very limited in scope. Researchers have generally assumed that there are only a few widely distributed species of coccoid algae. This collaborative (with Dr. Jeffrey Bailey at the University of North Carolina, Wilmington, Award 0084197) project is investigating the diversity, population dynamics, and physiological ecology of green-colored autosporic coccoid algae in Itasca State Park, Minnesota. Itasca possesses a high diversity of lakes, ponds, and bogs that are ideal for this study. The project encompasses several specific goals, including the 1) discovery of new taxa of coccoid algae; 2) development of reliable genetic criteria for the identification of coccoid algae; 3) establishment of a reference collection of coccoid algae; 4) determination of the distribution patterns of coccoid algae in different lake types; 5) study of the population dynamics of coccoid algae; 6) investigation of the higher-level systematics of coccoid algae; 7) investigation of the physiological tolerances of the coccoid isolates; and 8) development of a database of identification criteria and distribution data. Other phycologists working with additional algal groups will be involved. These studies should revolutionize the understanding of the temporal distribution, environmental requirements, and population dynamics of these important organisms. This project will provide conclusive evidence for new, more realistic hypotheses concerning populations of coccoid algae.
