The first known infestation of Bellamya japonica in the Savannah River Basin was discovered in 2006 near Clemson, SC. Investigations of this population led to the subsequent discovery of an industrial impact and several questions regarding their distribution and behavior. Teams of undergraduate research students have completed experiments on phototaxis and geotaxis and concluded that there exists a significant negative phototactic response but no detectable geotactic response. In addition, a study of dispersal using mark-recapture methods concluded that while this technique was useful to follow the life history of individual snails, they did not meet the assumptions of the mark-recapture technique and therefore this method could not produce a reliable population estimate. Studies of fecundity have shown a seasonal trend with an unsurprising correlation to water temperature and time-of-year. Fecundity rates are still being assessed for size-dependent relationships. Age is difficult to determine and the life history studies using marked specimens will assist with this as well. While fecundity is one important factor for population growth, individual metabolism is also important and unknown for this species and studies of the metabolism of this species are described in a separate presentation. Early anecdotal observations suggested a possible circadian rhythm with regard to fecundity as well. A systematic study of this possible phenomenon is also in progress. If successful we hope that our studies will provide a better understanding of the basic biology of this organism which will help with management in the future.
Dept of Biological Sciences, Clemson University, Clemson, SC
23 • Sarah Fishburne, Jessica Logan, Brittany Broome, Lauren Frees, Rebecca Helstern, Joshua Howard, Garrett Woollen, John Hains
Metabolism of Bellamya japonica : Experimental Design and Limitations
The metabolism of the Japanese Mystery Snail Bellamya japonica has not been reported previously, in spite of its ecological importance as an invasive species in North America. Little is known about this species as an invasive and while our research includes ecological investigations of distribution, behavior, and fecundity, we also are beginning basic biological studies related to growth and metabolism. At this time we have begun studies of respiration using measurements of oxygen consumption and are refining our methods. In order to remove any error in the measurement of oxygen consumption by external bacteria, the specimen must be cleaned. Bacterial culture trials using a variety of disinfectants indicated that physical scrubbing without any disinfecting agent was sufficient to prevent error. The metabolism of cleaned specimens will employ a sealed, respiration chamber, filled with filtered lake water. The oxygen consumption will then be measured over an empirically derived time. The rate of oxygen consumption will then be used to determine the specimen’s respiratory rate and this will be repeated to determine the effect, if any of habitat conditions such as temperature. Locally-collected specimens from the wild’ are employed with sufficient replications to meet normal’ statistical assumptions. In addition, specimens are subdivided into gender classes as well as controlled for biomass. Controlled metabolic estimates are made for varying thermal and pO2 conditions to determine the niche limits of this invasive species. Preliminary results for this study are presented here as well as plans for proposed extensions of this research.
Dept of Biological Sciences, Clemson University, Clemson, SC
24 • Amy R. Wethington
Distributional Differences in the Freshwater Pulmonate Snails Physa acuta And Physa gyrina: Competitive Exclusion or Habitat Choice?
Experiments were designed to test the effects of water quality and biological interaction on two congeneric species of freshwater pulmonate snails, Physa acuta and Physa gyrina, in order to understand their distributional patterns in the Griffy lake reservoir and surrounding wetland areas. It was my intent to discover what ecological factors restrict P. acuta to the reservoir and P. gyrina to the adjacent wetland area (Griffy Pond). I conducted three biological interaction treatments (two intraspecific and one interspecific) and two different water treatments (lake water and pond water), each treatment containing ten cultures of four snails. These results suggest that P. acuta negatively impacts P. gyrina’s growth and egg laying while P. gyrina is left to take advantage of the more rich pond environment perhaps due to P. gyrina’s high tolerance to heat and dessication. These two species are rarely found in the same water body and when they are, they tend to occupy different ecological space.
Chowan University
25 • Daniel Hoffman, Troy Mutchler, William Ensign
Quantifying Potential Differences in Trophic Relationships Across Freshwater Streams of Varying Urbanization
Interactions between terrestrial and aquatic ecosystems play an important role in ecosystem structure and function. For instance, urbanization near watersheds and riparian zones modifies not only the physical landscape, but also alters the linkages to nearby stream habitats through hydrology, sediment transport, and nutrient cycling. Modification to nutrient cycling through the addition or reduction of allocthonous material from surrounding terrestrial ecosystems may alter the nutrient and organic matter composition of the local aquatic system and affect the relative abundance of organisms at different trophic levels. To examine the potential differences in stream food web composition between urbanized and rural environments we selected three streams of similar size from two counties in the metropolitan Atlanta, GA area. Representatives of each trophic level (including periphyton from various substrata, plant material, invertebrates, and fish) were collected from each study site, dried, pulverized, and analyzed for 13C and 15N content. Feeding relationships will be identified based on these stable isotope signatures and comparisons will be made to detect changes in various trophic levels between the streams. Additionally, nutrient content of the tissues will be used to assess the differences in nutritional value of food sources across streams.
