FARM PONDS IN NEW-SOUTH-WALES, AUSTRALIA - RELATIONSHIP BETWEEN MACROPHYTE AND PHYTOPLANKTON ABUNDANCES

The physical, chemical and biological characteristics of 65 farm ponds in the Northern Tablelands and Central Western Slopes regions of New South Wales, Australia, were similar to those recorded for Australian ponds in other studies. The strongest single relationship between phys icochemical characteristics and biological characteristics was for hig h abundance of phytoplankton, low abundance of macrophytes, high turbi dity, and high nutrient concentrations in ponds on granitic soil. Vari ation among the ponds was such that no other relationship was signific ant. Five groups of ponds were discerned on the basis of their biologi cal and physico-chemical characteristics. One group could be classed a s reasonably 'pristine', with high water clarity and high abundance of macrophytes; another group presented highly eutrophic, phytoplankton- dominated conditions. Ponds in these two groups can be described as be ing in 'alternative stable states'. A third group had been modified wi th the intention of improving the appearance or utility of the ponds. The last two groups identified in this analysis had no specific parall els in the literature. Abundance of macrophytes was related to good wa ter quality, and encouragement of increased abundance of submerged pla nts in farm ponds could result in improved water quality.