NUTRIENT INPUTS INTO THE CENTRAL GREAT-BARRIER-REEF (AUSTRALIA) FROM SUBSURFACE INTRUSIONS OF CORAL SEA WATERS - A 2-DIMENSIONAL DISPLACEMENT MODEL

In the central Great Barrier Reef (17 degrees-20 degrees S), near-bott om intrusions of coal, nutrient-rich water upwell episodically onto th e outer shelf several times each summer (October-April). Near-bottom w ater temperature at the shelf break was found to be a useful but conse rvative predictor of the volume of intruded water and inorganic nutrie nt (N, P) inputs in cross-shelf sections. Large upwelling events that occur at least once per summer may displace up to 1/3 of the water on the outer shelf and import phosphate and nitrate stocks 2-6 times thos e normally present in outer-shelf waters. The concurrently displaced o uter-shelf waters export substantial amounts of organic N and P. Net N and P imports are on the order of 75% and 30% of gross N and P import s, respectively. Interannual variations in nutrient inputs from the Co ral Sea are related to the number and intensity of intrusive upwelling events occurring each summer. Comparison with other nutrient fluxes s uggests upwelling is a substantial source of ''new'' N and P to the ce ntral Great Barrier Reef. (C) 1996 Elsevier Science Ltd.