13C/12C and 15N/14N ratios of vesicomyid clams and a vestimentiferan tube worm in the subduction zone east of Japan
Abstract The 13 C/ 12 C and 15 N/ 14 N 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 13 C/ 12 C of clams varied from −35.9 to − 38.7% in C. phaseoliformis and from − 34.3 to − 35.5% in C. soyoae . 13 C/ 12 C 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. 15 N/ 14 N of the clams varied from −3.3 to + 0.8% in C. phaseoliformis and from −4.1 to +9.6% in C. soyoae . 15 N/ 14 N of the tube worm were −3.6% in tube, and − 4.1% in trophosome. In Calyptogena , gills showed the lowest 13 C/ 12 C and 15 N/ 14 N ratios. The 15 N/ 14 N 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.