Farm ponds in New South Wales, Australia: relationship between macrophyte and phytoplankton abundances

Abstract

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 physico-chemical characteristics and biological characteristics was for high abundance of phytoplankton, low abundance of macrophytes, high turbidity, and high nutrient concentrations in ponds on granitic soil. Variation among the ponds was such that no other relationship was significant. Five groups of ponds were discerned on the basis of their biological and physico-chemical characteristics. One group could be classed as 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 being in ‘alternative stable states’. A third group had been modified with the intention of improving the appearance or utility of the ponds. The last two groups identified in this analysis had no specific parallels in the literature. Abundance of macrophytes was related to good water quality, and encouragement of increased abundance of submerged plants in farm ponds could result in improved water quality.