Effects of mixed-layer depth and an isolated coral reef on the strong complexing capacity of oligotropic waters

Abstract

The strong copper complexing capacity of seawater was determined along three transects enclosing Wreck Reef, an isolated reef in the Coral Sea. Measurements of ship's drift and geostrophic calculations relative to 300 m indicated that little of the surface waters flowed through the reef system. The values of copper complexing capacity and dissolved organic carbon close to Wreck Reef were similar to those found within the Great Barrier Reef system. Within the top 100 m, values of complexing capacity ranged from 2.5 to 26 nM, with the elevated values being associated with a deep mixed layer on the leeward side of the reef and possibly with processes occurring within the reef itself. There was no correlation between copper complexing capacity and concentrations of nutrients or dissolved organic carbon. The copper complexing capacity within the euphotic zone was generally higher than that observed previously for surface waters of south-eastern Australia and the North West Shelf of Australia.