The presence of Hyallela in live Corbicula is a previously undescribed interaction that may have implications in the successful management of clam monocultures (See Background Information section). The purpose of this project is to investigate possible negative interactions of clams and amphipods within closed systems. Experiments will be performed on live clams on both population and individual scales in order to reproduce shell chipping and amphipod invasion of live clams as seen at the Hague system. Temperature variation and the potential for using sediment sizing or fish to limit these interactions will also be investigated.
Students actively participate in experiment startup, monitoring and dismantling with emphasis placed on clam/amphipod measurements and periodic sampling water quality parameters. This experience will provide students with exposure to experimental design, system construction, specimen collection, execution of prescribed methodologies and data handling. Students will also be encouraged to participate in discussions of the experimental results.
An indoor laboratory established at the Alee Academy School is used to carry out all of the described experiments and provide easy access for students. The laboratory is equipped with a bench containing ten glass aquaria, each having a combination pump/filter device and an air pump for circulation and aeration in order to simulate closed-system environments. In-tank heaters were installed to regulate water temperature. The facility is also equipped with a timed fluorescent lighting system set on a continuous 12-hour ON, 12-hour OFF cycle in order to mimic natural diurnal changes in light.
Population Scale Experiments
Population scale experiments will focus on the affect of increased temperature on clam/amphipod interactions in a coarse sand substrate type used at the Hague facility. The potential for using fish, substrate size or a combination of the two will also be evaluated in order to limit shell chipping and amphipod invasion in clam monocultures. High temperatures (28-32°C) at the Hague system may have contributed to clam physiological stress, possibly aiding in the invasion potential of the amphipods. In order to test this hypothesis, one experiment will be performed at a lower temperature range to eliminate effects from heat stress. The rest of the experiments will be performed at an increased temperature, 26°C, approximating the upper non-lethal biological limit. This investigation of temperature effects on shell chipping and amphipod invasion is important because the warmer climate of Florida may expose future clam aquaculture systems to temperatures in excess of 28°C. If amphipod interactions are found to increase with temperature then further study of fish addition and substrate sizing as amphipod control mechanisms becomes just as important for the success of future clam monocultures. These experiments will focus on clam mortality, shell chipping and occurrences of amphipods in clam tissue in order to evaluate fish and sediment size as potential controls. Clam growth and health status will also be assessed at the beginning and end of each experiment.
Individual Scale Experiments
Individual-scale experiments will be used to examine the survival of clams following an amphipod introduction to the shell cavity at various temperatures. Live clams will be directly injected with amphipods in order to determine clam mortality rate in response to amphipod addition and the ability of clams to expel amphipods from within the shell cavity. This experiment will be used to establish the impact of amphipod invasion on clam survival and possibly support the idea that shell notching occurs post-amphipod introduction. Experiments at 28, 26 and 24°C water temperatures will be used to assess the effect of heat stress on possible clam/amphipod interactions.