The amount of carbon dioxide available for plant growth varies substantially among aquatic ecosystems. Submersed aquatic macrophytes differ in the forms of CO2 that they are able to use. Different species are differentially sensitive to different carbon levels. It is hypothesized that differences in CO2 availability will be related to the types of plant species that occur in acid and circumneutral lakes because of species' differential sensitivities to carbon levels. Differential sensitivity to CO2 levels is expected to explain many of the among-lake differences that are observed in macrophyte community composition. To test this, growth sensitivity to CO2 will be tested for most submersed plant species in lakes in the Adirondack Mountains in NY. Lakes in this regions exhibit a wide range of chemical conditions and CO2 levels. Plant responses will be tested in controlled greenhouse tank experiments to determine a CO2 sensitivity index (CSI) for each species. These indices will be combined with information to be collected on the distribution of submersed macrophytes across a range of lakes. Information on these lakes' chemical conditions will also be determined to test for relationships between the CSI and lake environmental conditions. In addition, artificial communities will be established with 6 species with varying CSI's to test the macrophyte distribution hypothesis experimentally. This work, combining lab, greenhouse, and in situ experiments with surveys of natural habitats will provide a thorough assessment of the importance of differential CO2 exposure to natural community composition.
