Rates in Aquatic Environments D. Sources of DON: Research Priorities IV. Sinks for DON A. Heterotrophic versus Autotrophic DON Utilization B. Methods for Estimating Biotic DON Uptake C. Literature Values of DON Uptake in Aquatic Environments D. Photochemical Decomposition as a Sink for DON E. Sinks for DON: Research Priorities V. DON Thrnover Times VI. Summary References