Changes in northeast Pacific marine ecosystems over the last 4500 years: evidence from stable isotope analysis of bone collagen from archeological middens

Abstract

Changes in food web dynamics and ocean productivity over the past 4500 years are investigated using stable isotope analysis of nitrogen and carbon in collagen from animal bones preserved in coastal archeological middens on Sanak Island, along the eastern edge of the Aleutian archipelgo. Samples included Steller sea lions, Harbor seals, Northern fur seals, sea otters, Pacific cod and sockeye salmon. Sea otters had the highest δ13C (−11.9 ± 0.7‰) and lowest δ15N values (14.5 ± 1.4‰), Northern fur seals had the lowest δ13C values (−13.6 ± 1.4‰), and Steller sea lions had the highest δ15N values (18.4 ± 1.4‰) of the marine mammals. Cod isotope values were consistent with those of demersal organisms from near shore habitats (−12.5 ± 0.9‰ δ13C, 16.1 ± 1.4‰ δ15N), while salmon values were consistent with those of organisms existing in an open ocean habitat and at a lower trophic level (−15.2 ± 1.4‰ δ13C, 11.5 ± 1.7‰ δ15N). When comparing six different prehistoric time periods, two time periods had significantly different δ 13C for salmon. Otters had significantly different δ15N values in two out of the six prehistoric time periods but no differences in δ13C. The mean δ13C, corrected for the oceanic Suess Effect, of modern specimens of all species (except Northern fur seals) were significantly lower than prehistoric animals. Several hypotheses are explored to explain these differences including a reduction in productivity during the twentieth century in this region of the Gulf of Alaska. If true, this suggests that North Pacific climate regimes experienced during the twentieth century may not be good analogs of North Pacific marine ecosystems during the late Holocene.

Chemical profiling of ancient hearths reveals recurrent salmon use in Ice Age Beringia

“…4). These results are significant in terms of (28)(29)(30)(31)(32)(33)(34)(35)(36), from modern interior Alaska (in this study), and bone collagen from USR fauna (in this study), and other ancient salmon in Alaska (23,(37)(38)(39). AB, aquatic bird (red square); FF, freshwater fish (blue square); SA, salmon (pink square); TA, terrestrial animals (green square).…”

“…Bulk δ 13 C and δ 15 N values from analyses of hearth sediment, bone collagen, and muscle tissue samples were measured at the Alaska Stable Isotope Facility (ASIF), University of Alaska Fairbanks, following established protocols (ref. 37 and SI Materials and Methods). Lipids in hearth and muscle samples were extracted by using standard protocols (refs.…”

Stable isotope evidence supports pelagic fishing by hunter-gatherers in southern South America during the Late Holocene

“…It is well known that fish species distributions are likely to have fluctuated during the Holocene as a consequence of sea surface temperature and marine productivity, among other factors (Finney et al, 2002;Jackson et al, 2001;Misarti et al, 2009). It is also widely recognized that modern commercial fisheries had significant impacts on fish communities (Jackson et al, 2001;Maschner et al, 2008).…”

Stable isotopes reveal inter-annual and inter-individual variation in the diet of female Australian fur seals

“…Marine ecosystems are highly dynamic, changing on a range of spatial and temporal scales under a variety of influences (Bertram et al 2001, Misarti et al 2009). Detecting such changes may be challenging at times, due to the complex trophic interactions that occur and the logistical restrictions that limit the range and extent to which oceanic regions can be feasibly sampled (Fulton et al 2004).…”