“…[15] Previous examples of high NO 3 À uptake, or uptake in excess of local production requirements, at the nitracline are known [Eppley and Renger, 1986;Eppley and Koeve, 1990;Eppley and Renger, 1992;Allen et al, 1996;Varela et al, 2005]. Suggested causes for this observation include (1) heterotrophic bacterial uptake [Eppley and Renger, 1992], (2) transiently or permanently decoupled algal C:N uptake ratios [Eppley and Renger, 1986;Banse, 1994;Anderson and Pondaven, 2003;Falkowski and Davis, 2004;Christian, 2005], (3) uptake by vertically migrating species of phytoplankton such as Rhizosolenia spp.…”