Amino acids in suspended particulate matter from oceanic and coastal waters of the Pacific

Abstract

Abstract The concentration of 15 amino acids in hydrolyzed particulate matter from different regions and depths of the Pacific Ocean has been measured by gas—liquid chromatography. The relative composition was similar for all samples in the euphotic zone, where the particulate amino acid (PAA) concentration ranged from 370 to 2260 nmoles/1 in coastal waters and from 90 to 260 nmoles/1 in the open ocean. Total PAA concentration dropped rapidly with depth, levelling off at 10–40 nmoles/1 below 200 m. Glycine, serine, glutamic acid and aspartic acid were the most abundant PAA in deep equatorial water and in deep off-shore California water. The nitrogen content of PAA could often account for 100% of the total particulate organic nitrogen present, while PAA carbon contributed up to 50% of the total particulate organic carbon in euphotic waters and down to 20% in deep waters. The protein equivalent to the total PAA content of particulate matter in near-surface waters amounted to 11–32 μg/1 at oceanic stations and up to 270 μg/1 at coastal stations.