Water quality and macroinvertebrate response to acidification following intensified summer droughts in a Western Australian wetland

Abstract

A decline in pH from ˜6 –8 to ˜4 –5 over a period of 4 years was detected during routine monitoring of surface waters at Lake Jandabup.This was accompanied by lower water levels,shorter periods of inundation and measurable changes in other attributes of the water:sulfate,iron and ammonium concentrations increased markedly,and filterable reactive phosphorus and colour (gilvin)decreased.Macroinvertebrate family richness did not change notably over this period,but there were shifts in community structure:ostracods,isopods and oligochaete worms became less abundant;amphipods,mayflies and gastropods disappeared,while ceratopogonids (Diptera)and macrothricid cladocerans increased in abundance.Historical evidence suggests that at least one other acidification event has occurred in the recent past.Mechanisms associated with the acidification,and the wetland ’s capacity to recover from such events,are discussed.