Peru upwelling region sediments near 15°S. 2. Dissolved free and total hydrolyzable amino acids1

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Abstract
Dissolved free and total hydrolyzable amino acid concentrations were measured in five cores of Peru coastal sediments collected along a 70‐km transect perpendicular to the coast in the upwelling region near 15°S at depths of 92, 268, 506, 1,428, and 5,300 m. Total hydrolyzable amino acids (THAA) made up 20–70% of the total nitrogen in these sediments, with the highest proportions in surface sediments of the 92‐, 268‐, and 506‐m cores. Variations in THAA content with depth were attributable to a combination of remineralization and varying inputs to the sediment surface over time. The individual amino acid residue composition was remarkably uniform, both with depth in core and between stations.Dissolved free amino acid (DFAA) concentrations ranged from about 1 µM to µM. The highest concentrations were found near the sediment‐water interface of sulfide‐containing sediments. Concentrations generally decreased with depth in sediment. Glutamic acid was a major constituent of nearly all samples, suggesting a bacterial source for most of the DFAA. A nonprotein amino acid, β‐aminoglutaric acid, was also a major component and was the most abundant DFAA below 20‐cm depth in the 92‐, 268‐, and 506‐m cores. The major trends in DFAA concentration and composition appear to be the net result of biological (largely bacterial) sources and sinks.
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