PALEOECOLOGICAL CHANGE IN THE SOUTHERN ALASKA COASTAL REGIONS DURING THE HOLOCENE: THE HISTORY AND IMPORTANCE OF PACIFIC SALMON RUNS

In the south coastal regions of Alaska (Northeast Gulf of Alaska/Southeast Bering Sea), changes in marine resource abundance have the potential to impact humans and terrestrial and freshwater ecosystems. Pacific salmon are a primary vector in the movement of biomass from ocean to land. Several recent studies have demonstrated that salmon deliver substantial amounts of marine-derived nutrients to coastal terrestrial and freshwater environments when they return to spawn and die. Salmon abundance can be reconstructed from stable nitrogen isotope (¹⁵ N) analysis of lake sediment cores, because returning salmon supply significant quantities of nitrogen, relatively enriched in ¹⁵ N, into freshwater systems. Temporal changes in the input of salmon-derived nutrients, and hence abundance, can be quantified through downcore analysis of d ¹⁵N. Analyses of cores from sockeye salmon lakes from this region (Bristol Bay, Kodiak Island, Southcentral and Southeast Alaska) typically show similar temporal patterns in d ¹⁵N, with significant variability ranging from decadal to millennial timescales. Reconstructed salmon abundance is generally high during the Little Ice Age, and from ~ 2000 - 4000 yr BP. Correspondence between these records and paleoclimatic data from this region suggest that changes in salmon abundance are driven by large scale climatic changes over the North Pacific. Several significant changes in salmon abundance also correspond to cultural changes inferred from the archeological record. This research continues to draw inspiration from David Hopkins, and his holistic approach to Beringian paleoecology.