Elemental and Isotopic Signatures in the Sediments Influenced by Seal Excrement on Antarctic Fildes Peninsula and Their Potential Paleoecological Applications

摘要

The elemental and isotopic signatures in the sediments influenced by seal excrement on Antarctic Fildes Peninsula are examined for their potential palaeoecological applications. The seal hair abundance in sediments exhibits remarkable fluctuation versus depth, indicating similar changes in historical populations of the seals visiting the marine terrace. The combination of δ~(13)C, total organic carbon concentration (TOC), total nitrogen concentration (TN) and atomic C/N ratio shows that the organic matters in sediments with numerous seal hairs have a marine origin and are predominantly derived from seal excrements. The large δ~(15) N values in sediments are attributed to trophic enrichment and NH_3 volatilization processes. The large variations in the δ~(15) N values and the negative correlation between the δ~(15) N values and the seal hair abundances seem to be the results of changes in the paleoclimates and the volatilization rates of the ammonia produced in the seal excrements. The ~(87)Sr/~(86) Sr ratios in the acid-soluble fraction of sediments are interpreted as a mixture of the ones from the seal excrements (30%-50%) and the chemically weathered local bedrocks (70%-50%). The calculated proportion of seal-derived Sr based on the ~(87)Sr/~(86) Sr ratios has a significant correlation with seal hair abundances in sediments. These results suggest that δ~(15) N values and the ~(87)Sr/~(86) Sr ratios in the acid-soluble fraction of sediments were influenced by seal excrements, similar to seal hair numbers, and thus can potentially be used to estimate the historical seal population in the Antarctic region.