Marine Mammal Bone as Recorder of Trace Element Dynamics during the Past 5500 Years in the North Pacific Ocean

Marine Mammal Bone as Recorder of Trace Element Dynamics during the Past 5500 Years in the North Pacific Ocean

Alvin Sherman Library

The North Pacific Ocean has been geologically dynamic and biologically diverse since the Last Glacial Maximum (20,000 ybp). Natural fluctuations in island arc volcanism and climate likely influence the input of essential and nonessential trace elements to the Aleutian Island Archipelago, even to present day. Accumulation of these elements in the region's marine food webs provides a measure of natural fluctuations in the environment. Ninety-eight samples of tephra-preserved marine mammal bone (primarily pinnipeds) sourced from temporally identified archeological Aleut midden sites on Unalaska Island (5500-200 ypb), were analyzed for 20 trace elements using inductively coupled plasma mass spectrometry (ICP-MS). Concentrations were compared temporally with historical and contemporary Alaskan bones (ca. 1850-1980). Archaeological samples were highest in aluminum (Al), calcium (Ca), iron (Fe), strontium (Sr), vanadium (V), and zinc (Zn). Concentrations of 14 elements were significantly greater in archeological samples than historic ones, and much greater than typically observed in mammal bone. These concentrations were aligned with data from the surrounding volcanic-sourced geology, suggesting diagenetic alteration during burial. Differences in arsenic (As) and lead (Pb) concentrations between pinniped species may be attributed to variances in diet. Concentrations of Pb and tin (Sn) were greater in contemporary samples, possibly reflecting anthropogenic input following the Industrial Revolution. This study establishes a baseline of pre-anthropogenic trace element concentrations and provides evidence of further enrichment via industrial activities in the North Pacific Ocean through archaeological and historic marine mammal bone analysis.