The water quality status of the Great Barrier Reef World Heritage Area J Brodie Great Barrier Reef Marine Park Authority, PO Box 1379, Townsville Qld 4810 Abstract Water quality monitoring programs in the Great Barrier Reef (GBR) region are primarily focussed on sediment and nutrient concentrations in the water column. Far fewer results are available from monitoring of persistent organic compounds, trace metals or hydrocarbons or from the sediment or biota compartments. Relatively comprehensive monitoring of the river discharge of sediment and nutrients has occurred over the last decade. Results show the extreme temporal variability in these inputs. Limited monitoring of nutrient upwelling at the shelf-break, nutrient content of rainfall and nitrogen fixation over the last few years has allowed first order estimates of a nutrient budget for the central GBR. Biological oceanographic research from the last 15 years has allowed a synthetic monitoring data set for nutrients to be constructed for a large part of the GBR lagoon. This shows the lack of temporal trends in nutrient concentrations over this period but does quantify some cross-shelf and latitudinal spatial trends. These trends are corroborated by results from the long-term chlorophyll monitoring program, now in its fourth year, and the Australian Institute of Marine Science (AIMS) long-term monitoring program for nutrients and chlorophyll. Results from long-term nutrient programs listed above are for ‘ambient’ conditions in the GBR lagoon and are supplemented by specific monitoring programs during river flood plume conditions. These highlight the extreme sediment and nutrient concentrations found in these plumes and the oceanographic/meteorological control of the dispersion of the plumes. Few monitoring surveys for chlorinated hydrocarbons, pesticide residues, trace metals and petroleum hydrocarbons have been carried out in the last decade. Low levels of these contaminants were generally found in surveys conducted between 1975 and 1985. The Torres Strait Baseline Study is the largest recent program examining any of these contaminants (trace metals). Introduction Source of this review This review draws extensively from a Iarge body of work carried out in the last 70 years in the GBR region and reference is made to this work throughout the document. In addition, however, the review draws directly on a number of recent comprehensive papers and passages of these papers are directly reproduced in this review. The papers concerned are: Fumas, M. and J. Brodie 1997. Current status of nutrient levels and other water quality parameters in the Great Barrier Reef, pp. 9-21. In H.M. Hunter, A.G. Eyles and G.E. Rayment (eds), Downstream Efsects of fund Use, A National Conference on Downstream Effects of Land Use, held in Rockhampton, Queensland, Australia, 26-28 April, 1995. Brodie, J. and M. Fumas 1997. Cyclones, river flood plumes and natural water quality extremes in the Central Great Barrier Reef, pp. 367-374. In H.M. Hunter, A.G. Eyles and G.E. Rayment (eds), Downstream Effects of Land Use, A National Conference on Downstream Effects of Land Use, held in Rockhampton, Queensland, Australia, 26-28 April, 1995. 69