The macroinvertebrate fauna in a polluted alluvial gravel aquifer downstream of a sewage irrigation area at Templeton, New Zealand, was surveyed using an existing array of unpumped wells. Three crustacean species -Phreatoicus t,lspicus, Phreatogammarus.fragilis and Paracrangon!*x compactus accounted for 98% of the organisms present. The remainder consisted of turbellarian and oligochaete worms and two further crustacean taxa ~ Paraleptamphopus subterraneus and a new species of the genus Paracrangonyx. Smaller invertebrates found included juveniles of the macroinvertebrate Crustacea and a new amphipod genus and species. Mean population density and dry weight biomass estimates for the three principal crustacean species in the groundwater underlying the disposal area were, respectively, 192 m 2 and 0.43 g m 2 for P. t.spicus, 55 m 2 and 0.16 g m~2 for P. fragilis, and 18 m~2 and 0.04 g mm2 for P. compactus.
Approximately 10% of the crustacean specimens tested contained coliform bacteria and had apparently been feeding on sewage-derived material. The organisms tended to be more abundant in the more polluted wells but incidents of heavy contamination caused high mortality rates. Some calculations using energetics data from surface water studies suggested that the standing crop of aquifer macroinvertebrates could play a significant role in the consumption of sewage-derived organic matter reaching the phreatic zone beneath the Templeton site.