Amino Acids in Interstitial Waters from Sites 790 and 791 in the Izu-Bonin Island Arc

Abstract

Sites 790 and 791 lie in the eastern half graben of the Sumisu Rift, a backarc graben west of the active Izu-Bonin arc volcanoes Sumisu Jima and Tori Shima, at 30°54.96'N, 139°50.66Ti, in 2223 m water depth and 30°54.97'N, 139°52.20'E, in 2268 m water depth, respectively. A small decrease in the sulfate concentration in the interstitial waters from these sites suggests fairly low microbial activity by sulfate-reducing bacteria.The values of the dissolved free amino acids (DFAA) in the interstitial waters from both sites range from 1.26 to 6.82 µmol/L, with an average of 3.81 µmol/L. The acidic, basic, neutral, aromatic, and sulfur-containing amino acids have average values of 0.32, 0.50, 2.71, 0.15, and 0.09 µmol/L, respectively. The relative abundances of the acidic, basic, neutral, aromatic, and sulfur-containing amino acids average 8, 13,72,4, and 1 mol%, respectively. Glycine, serine, alanine, ornithine, and aspartic acid are major constituent amino acids. The dissolved combined amino acids (DCAA) values range between 1.25 and 44.35 µmol/L, with an average of 10.36 µmol/L. The mean concentrations and relative abundances of the acidic, basic, neutral, aromatic, and sulfur-containing amino acids are 2.29 (22 mol%), 0.60 (6 mol%), 6.70 (65 mol%), 0.09 (1 mol%), and 0.00 µmol/L (0 mol%), respectively. Glycine is the most abundant amino acid residue, followed by glutamic acid, serine, and alanine. The predominance of DCAA over DFAA present in the interstitial waters from Sites 790 and 791 is consistent with previous results from interstitial-water and seawater analyses.The most plausible source for the DCAA is biogenic calcareous debris. A much greater depletion of aspartic acid and the basic fraction, except for ornithine, is found in the DCAA. The decomposition of the basic amino acid fraction or its incorporation to clay minerals would result in a decrease in its relative abundance, whereas ornithine is produced during early diagenesis. The characteristics of the amino acids in the interstitial waters are (1) a greater depletion of the acidic amino acid fraction in the DFAA than in the DCAA and (2) the enrichment of glycine and serine in both. The adsorption or reaction of the amino acids in interstitial waters with biogenic carbonates would be responsible for the lower relative abundance of the acidic fraction of the DFAA. The production of glycine during early diagenesis and its stability in solution would raise its relative abundance in the interstitial waters.

Amino acids in interstitial waters from ODP Sites 689 and 690 on the Maud Rise, Antarctic Ocean.

“…Kawahata andIshizuka (1989, 1993) found greater concentrations of the total DCAA (average, 5.1 µmol L -1 ) than the total DFAA (average, 3.2 µmol L -1 ) in the interstitial water from biogenic carbonate and silica-rich sediments from the Panama Basin. Similar results were obtained from interstitial waters from Sites 790 and 791 lying on a backarc graben west of the active Izu-Bonin volcanoes (Kawahata and Ishizuka, 1992). The total DCAA and the total DFAA values were on average 10.36 and 3.81 µmol L -1 , respectively.…”

Amino acids in water samples from deep sea hydrothermal vents at Suiyo Seamount, Izu-Bonin Arc, Pacific Ocean

“…It is lower by one order of magnitude than THAA in interstitial waters sampled from Izu-Bonin Island Arc. (Kawahata et al,1992).…”