13C/ 12C and 15N/ 14N ratios of vesicomyid clams and a vestimentiferan tube worm in the subduction zone east of Japan

Abstract

The 13C/ 12C and 15N/ 14N ratios were measured for a vesicomyid clam, Calyptogena phaseoliformis collected at a depth of 5960 m in the Japan Trench, and the vesicomyid clam C. soyoae and a vestimentiferan tube worm Lamellibrachia sp. collected at a depth of 1170 m in Sagami Bay. The 13C/ 12C of clams varied from −35.9 to − 38.7% in C. phaseoliformis and from − 34.3 to − 35.5% in C. soyoae. 13C/ 12C of the tube worm (−19.9% in tube, and −25.8% in trophosome) differed markedly from that of C. soyoae collected at the same location. 15N/ 14N of the clams varied from −3.3 to + 0.8% in C. phaseoliformis and from −4.1 to +9.6% in C. soyoae. 15N/ 14N of the tube worm were −3.6% in tube, and − 4.1% in trophosome. In Calyptogena, gills showed the lowest 13C/ 12C and 15N/ 14N ratios. The 15N/ 14N of the gill of C. soyoae reported here was the lowest (−9.6%) ever reported for animals in hydrothermal vents and cold seeps. A possibility of seepage of isotopically depleted ammonium is briefly discussed.