Suitability of Crangonyx pseudogracilis (Crustacea: Amphipoda) as an early warning indicator in the multispecies freshwater biomonitor.

BACKGROUND

Biological monitors are increasingly important in 'Biological Early Warning Systems' (BEWS) for monitoring water quality. This study examines the freshwater amphipod Crangonyx pseudogracilis as a potential new indicator species when used in the Multispecies Freshwater Biomonitor (MFB). The MFB is an online continuous biomonitor which uses impedance conversion to record behavioural responses of vertebrates and invertebrates.

METHODS

Four experiments were undertaken to establish: (1) if the electrical field generated by the MFB affected the organisms' behaviour, (2) if defined behaviours and their response to a gradient of ammonium chloride could be detected by the MFB, (3) if there was variation in the behaviour of C. pseudogracilis over a diel cycle, and (4) if behaviour changed significantly in response to a pulse of ammonium chloride.

RESULTS AND DISCUSSION

Results showed no significant effect of the MFB's current on behaviour of C. pseudogracilis. Four behaviours; swimming, walking, grooming and inactivity, were observed and identified in the MFB. In the MFB, each behaviour changed significantly in response to an increasing gradient of ammonium chloride exposure. The MFB also detected increases in nocturnal activity by C. pseudogracilis. The MFB also detected a significant increase in activity after a pulse of ammonium chloride.

CONCLUSION

The range of behaviours exhibited by Crangonyx pseudogracilis, together with its ease of culture, suggest future potential of this species as an indicator species for the Multispecies Freshwater Biomonitor.

RECOMMENDATIONS AND OUTLOOK

Further testing is required over a range of toxicants and concentration gradients to establish threshold responses and the full compliment of behaviours that could be useful in online biomonitoring.