The Great Barrier Reef shelf ecosystem is examined for nutrient enrichment from within the seasonal thermocline of the adjacent Coral Sea using moored current and temperature recorders and chemical data from a year of hydrology cruises at 3 to 5 wk intervals. The East Australian Current is found to pulsate in strength over the continental slope with a period near 90 d and to pump cold, saline, nutrient rich water u p the slope to the shelf break. The nutrients are then pumped inshore in a bottom Ekman layer forced by periodic reversals in the longshore wind component. The period of this cycle is 12 to 25 d in summer (30 d year round average) and the bottom surges have a n alternating onshoreoffshore speed up to 10 cm S-'. Upwelling intrusions tend to b e confined near the bottom and phytoplankton development quickly takes place inshore of the shelf break. There are return surface flows which preserve the mass budget and carry silicate rich Lagoon water offshore while nitrogen rich shelf break water is carried onshore. Upwelling intrusions penetrate across the entire zone of reefs, but rarely into the Lagoon. Nutrition is del~vered out of the shelf thermocline to the living coral of reefs by localised upwelling induced by the reefs. Bottom chlorophyll concentrations average 0.4 mg m-3 a t the inner reefs and 0.8 mg m-3 near the shelf break while surface concentrations average 0.3 mg m-3; annual top and bottom variances are respectively 0.5 and 1.9 m g m-3 and there is no apparent seasonal cycle. The estimated onshore nitrogen flux in a 10 m thick bottom layer gives an annual nitrogen input of 20 yg at 1-' throughout the water column in a 50 km zone of reefs, a n enormous value for tropical waters.

Thermocline waves are found on the continental slope and shelf of Queensland. Slope waves of period near 90 days accompany upwelling and downwelling. Shelf thermal waves are created by onshore surges of shelf- break water, which is 1-4.5�C cooler than lagoon water, depending on the season. The bottom surges are investigated by means of the cross-spectra of temperatures with longshore winds, with atmospheric pressure and with mean sea level. Longshore winds are found to be the driving mechanism and significant coherence is found near periods of 4 and 8 days (summer and winter, respectively) and in a band with periods of 10-70 days, perhaps peaking near 30 days. Correlation and cross-spectral analyses of temperature at sites 100 km apart suggest that the short period thermal waves popagate equatorward wheras the long period waves, which contain most of the thermal covariance, form a standing mode. Cross-spectral analysis of the root mean square amplitude of diurnal thermal variations with the longer-period thermal waves suggests that localized tidal upwelling brings bottom water over reefs.