Dissolved organic carbon in the INDEX area of the Central Indian basin

Dissolved organic carbon (DOC) concentrations at the Indian Deep-Sea Enviro nment Experiment (INDEX) site of the Central Indian Basin can be divided in to three depth intervals. The subsurface layer (25-200 m) shows highly vari able distribution with concentrations ranging from 52 to 191 muM. Between 5 00 and 800 m, DOC shows a minimum (41-57 muM) and is associated with decrea sed oxygen. The bottom waters (3500-5300m) show decrease with little variab ility in the DOC concentrations (41-64 muM) suggesting its refractory natur e in the deep ocean. The variable concentration of DOC with depth is relate d to the biochemical activity as well as to the chemical features of the wa ter column. Both high and low values of DOC with high apparent oxygen utili sation (AOU) indicate no significant correlation between DOC and AOU and su ggest simultaneous utilisation of oxygen for the oxidation of other species of organic matter in the water column. (C) 2001 Elsevier Science Ltd. All rights reserved.