Exchange of water, salt, nutrients and photoplankton between Peel Inlet, Western Australia, and the indian Ocean

Abstract

Two 5-day intensive exercises were undertaken to measure the exchange between Peel Inlet and the Indian Ocean under summer and winter conditions. During both exercises there were tides of small amplitude, with a periodicity of 24 h, typical of this part of the Western Australian coast. There was a substantial net gain of water by the estuary on both occasions (25-28% of estuary volume) due to longer term oscillations in water level which gave increased ocean levels of c. 22 cm during each study. In the summer exercise estuarine nutrient concentrations approximated those in the ocean, so that nutrient flux depended largely on long- term volume exchange as controlled by meteorological tides. There was a net gain of both nutrients and marine phytoplankton to the estuary. However, in the winter exercise river inflow produced low salinity and high nutrient levels in the estuary and, despite the net gain of water by the inlet, there was a large loss of nutrients and phytoplankton to the sea where they were apparently removed by longshore currents from near the mouth of the inlet channel.