Biological aspects of pollution in the Heathcote river,Christchurch, New Zealand

The presence and degree of pollution in the Heathcote River was estimated from bacterial and chemical analyses of water sampled at low tide from five stations in summer 1967–68. The river is very badly polluted in the industrial area and downstream of it, but is fairly clean upstream of the industrial area. Results of analyses of micro‐organisms and macrofauna at 20 stations are presented and distributions of these organisms are related to salinity and pollution in the river. Pollution is restricting the macrofauna of the river but is encouraging micro‐organism populations. Three groups of macrofauna are present:

• Those present in clean freshwater only,

• Those tolerating pollution but restricted to freshwater, and

• Those tolerating pollution but restricted to saline water.

The use of these groups of species as biological indicators of pollution in the Heathcote River has been evaluated; pollution appears to be indicated by absence of a group of species rather than by presence of one species.