MSU NSF C-RUI
|
||
C-RUI Faculty C-RUI Students C-RUI Publications C-RUI Presentations Other Links
|
David White Professor, Department of Biological Sciences Director, Center for Reservoir Research A.B. DePauw University ZOOPLANKTON AND BENTHOS STUDIES FOR THE CRUI STUDY. Zooplankton Most freshwater zooplankton are seasonal, existing as diapausing eggs in sediments for much of the year. Eggs of many species can withstand drying and wetting cycles, hatching when environmental conditions are appropriate while the eggs of other species must remain constantly wet (Wetzel 1983, Marzolf 1990, Hairston 1996). Reservoir fluctuations provide a unique set of both permanent and temporary aquatic conditions, and changes in the littoral zone may lead to complex interactions between competitive exclusion and disturbance. Species that may be excluded due to competition or predation in permanent water may be able to coexist in reservoirs with variable littoral conditions, leading to increased species diversity. Approach and Methods: The distribution and abundance of zooplankton throughout the embayment will be monitored by vertical tows to determine hatching times, diversity, and areal distribution patterns. Mesocosm studies: Most of the research, however, will take place in the mesocosm facility. Sediment samples from throughout the littoral zone and from permanently wetted areas will be collected, returned to the mesocosm facility, and cultures established for a array of manipulations. Manipulations will follow a general Latin square design. For example, permanently wetted sediments will be monitored for zooplankton hatching both under continually wetted conditions and following periods of drying and rewetting. Similarly, littoral sediments will be examined under different periods of wetting and drying and under different temperature regimes. Preliminary experiments have shown that a large number of species, primarily rotifers, appear in the cultures that are rarely collected in field samples, particularly from littoral zone sediments, but these observations have not been quantified nor have data been compared with samples from permanently wetted sediments. Benthos Approach and methods: Larger mobile invertebrates may utilize littoral zones in seasonal manner, with subsequent effects on their foraging behaviors and life histories. Seasonal changes in the abundance of crayfish (Cambarus sp.) have been documented in Kentucky Lake, apparently as a result of seasonal flooding within the littoral zone (Whiteman, unpubl. data). Crayfish are important predators and detritivores, recycling nutrients into the littoral and benthic zones of aquatic habitats (Pennak 1978). However, whether these animals move to deeper habitats, or are simply consumed as predators move into the flooded rocks, is unknown. In either case, their relative influence within the littoral zone ecosystem is diminished. Crayfish will be sampled at each site using traps designed specifically for these organisms. One crayfish trap placed at each site across the array of drying treatments will allow us to assess changes in distribution and abundance of these organisms, as well as movement rates and direction of movement, across the yearly water fluctuations. Crayfish abundance also will be evaluated by marking individuals with unique numbers (Whiteman, unpubl. data). We will measure the size and sex of crayfish to distinguish whether there are size- or sex-specific patterns across the littoral areas. One interesting mobile invertebrate is the opossum shrimp Taphromysis louisianae that has begun to commonly appear in the stomachs of juvenile bass from Ledbetter embayment (Brooks et al. 1998). Regular sampling methods have failed to collect this species as only one individual has been found in over 10,000 plankton samples (CRR database). Specimens can be collected, however, using light traps. Special attention will be paid to this species in order to understand its life history and distribution. We expect that Taphromysis is an inhabitant of the littoral zone. The less mobile benthos in Kentucky Lake are typical of eastern North American lakes and reservoirs in that they are almost exclusively species of permanent water. Thus we expect to see a very different community composition and structure in permanently wetted areas versus the littoral zone. Species in the littoral zone should be limited to those that produce an overwintering egg or cocoon (e.g., oligochaetes) or those that deposit eggs (chironomids) once the littoral zone is flooded. We would expect that shredders and gatherers that can utilize the larger allochthonous organic inputs from the stream and floodplain would dominate littoral zone species. These questions will be addressed in the general surveys. Further, we will utilize results from the zooplankton mesocosm experiments to determine what type of benthos survive the wetting and drying process. Selected Publications White, D. S. and R. Roughly. 2000. Marine Coleoptera. In: The Light Manual of intertidal processes. (invited book chapter). White, D. S., and S. P. Hendricks. 2000. Lotic macrophytes and surface-subsurface exchange processes. In: Streams and Groundwater. J. Jones and P. Mulholand (eds.). Academic Press. Pp 363-379. Hendricks, S. P., and D. S. White. 2000. Stream and Groundwater influences on phosphorus biogeochemistry. In: Streams and groundwater. J. Jones and P. Mulholand (eds.). Academic Press. Pp 221-235. Soranno, Patricia A., Katherine E. Webster, Joan L. Riera, Timothy K. Kratz, Jill S. Baron, Paul A. Bukaveckas, George W. Kling, David S. White, Nel Caine, Richard C. Lathrop, and Peter R. Leavitt. 1999. Spatial variation among lakes within landscapes: Ecological organization along lake chains. Ecosystems 2:395-410. Yurista, P. M., G. T. Rice, and D. S. White. 1999. Long-term establishment of Daphnia lumholtzi in Kentucky Lake, USA. Verh. Internat. Verein. Limnol. (in press). Brooks, C., D. Dreves, and D. White. 1998. Distribution records for Taphromysis louisianae with notes on ecology. Crustaceana 71:955-960. Spencer, W. E., S. Delaney, G. T. Rice, K. L. Johnston, R. Seither, and D. S. White. 1998. Optimum temperature for photosynthetic carbon assimilation in Kentucky Lake follows seasonal change in ambient temperature. Archiv. für Hydrobiol. 141:389-401. White, D. S., and W. U. Brigham. 1997. Aquatic Coleoptera. pp. 399-473. In: R. W. Merritt and K. W. Cummins. An introduction to the aquatic insects of North America. Kendall/Hunt Publ. Co. 862 pp. |