Tuesday, August 4, 2009
Exhibit Hall NE & SE, Albuquerque Convention Center
Background/Question/Methods The swollen bladderwort, Utricularia inflata, is a submersed freshwater macrophyte expanding its range into northeastern New York lakes. By understanding the environmental circumstances that favor an accumulation of U. inflata, predictions can be made as to where the impact of this invasive plant will be greatest. The three objectives of this field study were to (1) measure in situ growth rate to determine the potential for U. inflata to thrive at varying depths and on different lake sediments, (2) compare this free-floating plant's displacement from sites with different exposure to wind and water movement, and (3) quantitatively sample submersed vegetation to determine U. inflata's community importance along five depth contours (0.5 m, 1.0 m, 1.5 m, 2.0 m, 2.5 m) at nine sites of varying exposure from five Adirondack lakes.
Results/Conclusions Growth experiments in situ determined that U. inflata was quite capable of growth over a range of depths, with length more than doubling within two weeks at all depths tested (1-3 m; but relative growth rate—RGR—was significantly greater at shallower depths, P<0.01) and over a broad range of natural sandy, silty, and highly organic lake sediments (RGR did not differ significantly over 11 different sediments). Water movement displaced free-floating U. inflata deployed on the substrate. The most exposed site had fewer than 8% of plants remaining at the end of a two-week period, while the most sheltered site had as many as 46% remaining. Across all sites and depths, percent of U. inflata plants remaining was negatively correlated to index of fetch (R2=0.62; p<0.01). In accord with the displacement experiment, vegetation sampling revealed relative frequency values for U. inflata ranging from 0% to 38.4%, with greater values at sheltered sites and at greater depth. Despite its potential to grow well in shallow water, water movement can prevent the accumulation of Utricularia inflata there, and thus provide refuge for native species able to withstand wave exposure.
Results/Conclusions Growth experiments in situ determined that U. inflata was quite capable of growth over a range of depths, with length more than doubling within two weeks at all depths tested (1-3 m; but relative growth rate—RGR—was significantly greater at shallower depths, P<0.01) and over a broad range of natural sandy, silty, and highly organic lake sediments (RGR did not differ significantly over 11 different sediments). Water movement displaced free-floating U. inflata deployed on the substrate. The most exposed site had fewer than 8% of plants remaining at the end of a two-week period, while the most sheltered site had as many as 46% remaining. Across all sites and depths, percent of U. inflata plants remaining was negatively correlated to index of fetch (R2=0.62; p<0.01). In accord with the displacement experiment, vegetation sampling revealed relative frequency values for U. inflata ranging from 0% to 38.4%, with greater values at sheltered sites and at greater depth. Despite its potential to grow well in shallow water, water movement can prevent the accumulation of Utricularia inflata there, and thus provide refuge for native species able to withstand wave exposure.
