Integrated Biological and Chemical Monitoring: In situ Physiological Responses of Freshwater Crayfish to Fluctuations in Environmental Ammonia Concentrations

A portable, computer-aided physiological monitoring system (CAPMON) has been integrated with an automated, flow injection (FI) based chemical monitor to enable continuous, long-term recording of cardiac activity in selected aquatic organisms, and total ammonia concentration in the surrounding environment. Heart rate of the freshwater crayfish Pacifastacus leniusculus was recorded using non-invasive infrared emitter/detectors to transduce heart beat from 4 animals simultaneously. Data were collected continuously and stored on a laptop computer. The chemical monitor incorporated a gas diffusion unit and a solid state photometric detector. Remote control and data processing were accomplished using an in-house designed microcomputer. The instrumentation was fully evaluated in the laboratory and the field and was shown to be capable of operating unattended for periods of at least 1 week. An exposure-response experiment showed that 4 h exposures to concentrations of ammonia greater than 5 mg l^-1 had a significant stimulatory effect on heart rate (ANOVA F=7.6; df=5; P<0.0005). The feasibility of using the system in situ was demonstrated in a 2 week field trial in which the integrated monitors were successfully deployed at a landfill leachate lagoon.