Number 1

Six cores were obtained along a 70-km transect perpendicular to the Peru coast in the highly productive upwelling region near 15”S, at depths ranging from 90 to 5,300 m. All of the sediments sampled were diatomaceous oozes. Three cores overlain by poorly oxygenated water had Thioploca-like filamentous bacteria in surface sediments. Total organic carbon and total nitrogen contents of the sediments ranged from 0.8 to 10 % and from 0.1 to 1 % (dry wt). For the 90-m and 268-m cores, which had 210Pb surface sediment accumulation rates of about 0.6 and 1.1 cm. yr-I, surface sediment organic carbon accumulation rates were 40 and 70 g C.m-*.yr-I. The organic carbon and total nitrogen distributions in the three cores from the oxygen minimum zone indicate that there have been variations in the rate of accumulation of organic matter over time. These variations may be related in part to the frequency and intensity of El Niiio events. Porewater ammonium, nitrate, nitrite, total carbon dioxide, sulfate, and sulfide concentrations were measured. Remineralization rates in sediments calculated from the dissolved carbon dioxide profiles range from 0.6 to 20 g C. m- *. yr-I. Total carbon dioxide concentrations in porewaters of two oxygen-minimum-zone sediments were modeled using both steady state and nonsteady state distributions of metabolizable organic matter. The coastal waters of Peru are highly pro- 197 1). These rates are about an order of ductive because of upwelling in the Peru magnitude greater than the average daily current system. Two areas of consistent rates reported for open ocean surface water, strong upwelling were identified by Zuta et 0.1-0.2 g C.m-2.d-1 (Menzel and Ryther al. (1975) one between 4’S and 6’S and the 1960). other between 14”s and 16”s. Primary pro- The high rates of primary production re-ductivity during upwelling typically ranges from 1 to 3 g Cm m-2. d-l (Zuta and Guillen 1970; Barber et al. 1978; Gagosian et al. 1980) and may exceed 10 (Ryther et al