Bulk delta15N values in surface sediment samples off the southwestern coast of Africa were measured to investigate the biogeochemical processes occurring in the water column. Nitrate concentrations and the degree of utilization of the nitrate pool are the predominant controls on sedimentary delta15N in the Benguela Current region. Denitrification does not appear to have had an important effect on the delta15N signal of these sediments and, based on delta15N and delta13C, there is little terrestrial input.

f = Nitrate unutilized from the ratio of [NO3] in surface water (from Conkright et al., 1994) to [NO3] in upwelled water and f estimated based on sedimentary 15N using Eqs. 1 and 2 from Altabet and Francois (1994, doi:10.1029/93GB03396)

Supplement to: Holmes, M Elizabeth; Müller, Peter J; Schneider, Ralph R; Segl, Monika; Wefer, Gerold (1998): Spatial variation in euphotic zone nitrate utilization based on 15N in surface sediments. Geo-Marine Letters, 18(1), 58-65