Water Properties of Ashmore Reef, North-west Shelf, Australia

Brief description

Ashmore Reef is a tropical marine reserve positioned at the confluence of Indian Ocean waters and the Indonesian Through Flow, has three vegetated cays all with fresh water lenses and two lagoons, separated by a calcareous algal rise. Both lagoons have two entrances on the northern side of the reef. The reef is subject to a 4.75 m semi-diurnal tide and on a spring tide ~7.5 km3 of water washes over the reef. The regional, lagoonal and well water qualities in and around Ashmore Reef have been observed from 1991 with a more intensive program since 1999 to ascertain it's chemistry and possible relationships with biodiversity. Sea surface temperatures of the surrounding oceanic water seasonally range from 25.48°C to 30.2°C and salinity from 34.51 to 34.75. Satellite derived lagoonal temperatures range from 25.4°C - 34.5 °C with an average of 29.4 °C, salinity ranges from 39.6 to 31.2.

The fresh water lens on West Island has up to 150 000 ltr/yr pumped from the well. Well water temperature varies between 28°C and 29°C, and salinity has ranged from 0.03 to 3.94 with a pH of 7.64 dissolved oxygen percentage ranged from 27% to 51 %.

This reef is within the tropical monsoonal belt, with thunderstorms occurring on ~85 days/yr and where evaporation potential is ~1820 mm, almost twice that of annual rainfall of ~950 mm.

This article can be found in The Beagle, pp. 9-12. The Beagle is a print only journal.

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