The Peel-Harvey system shows marked symptoms of eutrophication, but the responses of the two basins within the system have been quite different. In the Harvey Estuary dense blooms of Nodularia spumigenaoccur in most summers, reaching a maximum in mid-December before collapsing abruptly (Lukatelich and McComb, 1986). In Peel Inlet a more obvious symptom of eutrophication is the presence of massive populations of macroalgae which are washed onto the beach throughout the year, and lead to the need for 'cosmetic' harvesting of the algae, either from the beaches or immediately offshore (McComb et al.,1981).
The eutrophication of both systems has attracted considerable public attention, largely because of the visual pollution, and the nauseous smell of rotting blue-green algae or macroalgae, which foul what were once clean, sandy beaches in an area of considerable aesthetic appeal. As well as local residents, many visitors come to the area to swim, sail, and use power boats, and there is a well-developed amateur fishery. There is also a professional fishery, and the catch of fish 'per unit effort' has increased in Peel Inlet with increasing macroalgal biomass, but fish leave the area during Nodulariablooms (Potter et al.,1983a, b).
A major study of eutrophication in the system, including the monitoring work discussed here, was funded because of public perception of the magnitude of the problem. It began as an investigation of macroalgal growth in 1976, followed by a two year study to examine the major sources of nutrients to the system, in collaboration with the Centre for Resource and Environmental Studies in Canberra (CRES) .
At the commencement of the work only the macroalgal problem appeared significant, and sampling was carried out at 6 sites in Peel Inlet, chosen to represent sectors of the inlet, and 1 site in Harvey Estuary. However, in the third year there occurred the first massive blue-green bloom in Harvey Estuary to attract public attention, and the number of sites in Harvey Estuary was increased to 6. For both systems it was clearly established that the major source of nutrients to the systems is river flow, which occurs in winter (Humphries et al.,1981; Birch, 1982). The intensity of monitoring was then reduced for logistical reasons to three sites in each basin.