A study of oxic/anoxic effects on degradation of sterols at the simulated sediment-water interface of coastal sediments

Laboratory incubation experiments were conducted to determine the behavior of sterols at the sediment-water interface in oxic and anoxic sediments. Both plankton and 4-(14)C-cholesterol were used as tracers. Cholesterol was rapidly degraded at the sediment-water interface: 55% of (14)C-cholesterol was lost from sediments under anoxic conditions and 78% under oxic conditions over three and one-half months. About 3% of initially-added free radiolabel was incorporated into a bound pool that was released only by saponification of solvent-extracted sediment. Less than 1% of initially-added radiolabel remained in pore waters after three and one-half months. Rate constants for degradation of cholesterol in oxic and anoxic surficial sediments were estimated by tracking variations in radioactivity and sterol concentration as a function of time. We discuss our results in terms of factors affecting sterol degradation in coastal marine sediments, including molecular structure, sediment matrix effect, and redox conditions; (C) 1998 Elsevier Science Ltd. All rights reserved.