Particulate protein in the Peru upwelling system

Abstract

Particulate protein was measured in depth profiles along sections normal to the coast of Peru at 15, 10, and 5°S latitude. A subsurface maximu that coincided with the depth of the secondary nitrite maximum was found between 130 and 230m at 15°S. Protein concentration decreased offshore in the upper 370m, but below 370m horizontal variations were undectable. Vertical profiles show an exponential decrease with depth to 1000m. This rate of decrease was used with oxygen consumption rates to determine mean sinking rates of 1 to 5 m day−1 from 75 to 1000m. Protein was highly correlated with chlorophyll in the euphotic zone and with ETS activity at all depths. Concentrations of protein in the surface waters ranged from 28 to 1157 μg1−1; below 250m concentrations were less than 50 μg1−1.