Kelly Kearney¹, Charles Stock², Desiree Tommasi², Jorge Sarmiento³

¹ University of Miami, RSMAS/NOAA Atlantic Oceanographic and Meteorological Laboratory, USA

² NOAA Geophysical Fluid Dynamics Laboratory, USA

³ Princeton University, USA

In Aug. 2008, the Kasatochi volcano, located in the Aleutian Islands, erupted. The resulting ash plume drifted over the Gulf of Alaska region, which is typically a high-nutrient, low-chlorophyll region, leading to an anomalously high bloom of diatoms. Parsons and Whitney (2012) suggest that this volcano-induced bloom may be responsible for higher than average returns of Fraser River salmon in 2010; this particular cohort of salmon would have been migrating into the Gulf of Alaska during the high productivity period. However, McKinnel (2013) counters that survival levels in this cohort were no higher than in previous years, and that the increases in diatom and mesozooplankton abundance associated with the eruption would have little effect on salmon who feed primarily on euphausiids and larval fishes; he instead attributes the high returns to a high spawner population in 2006. Here, we use an end-to-end ecosystem model that couples physics, biogeochemistry, and food web dynamics for the subarctic Pacific food web to further investigate these competing hypotheses. The model has previously been demonstrated to capture seasonal patterns in nutrient cycling and primary production while maintaining upper trophic level populations at levels consistent with observation. It therefore provides a useful tool to quantify how volcano-induced primary production may propagate to higher trophic levels, and whether the increased salmon returns may be attributed to direct bottom-up food web processes.