A Temporal comparison of the eelgrass (Zostera marina L.) food web and community structure at Izembek Lagoon, Alaska from the mid-1970's to 2008

Abstract

This thesis investigates food web and community structure in Izembek Lagoon, Alaska, an ecologically important sub-arctic seagrass system. Unprecedented environmental changes in high latitudes, such as increased sea-surface temperatures and a shorter duration of shore-fast sea ice, may now favor seagrass over phytoplankton production as compared to forty years ago. Any resulting shifts in food web and community dynamics could have substantial consequences given the importance of seagrass habitat for Alaskan fisheries, global migratory bird populations and benthic energy transformation. Recent (2008) stable isotope (C and N) values and benthic community metrics were gathered and compared to results from a similar study from the mid-1970’s to gauge temporal food web and community structure differences. An increase in reliance on seagrass carbon was detected in organisms involved in detrital and sediment processing. An increase in abundance of certain benthic organisms and a decrease in overall community evenness were also seen. These findings suggest an escalation in delivery of seagrass carbon to the food web, possibly induced by changing seagrass morphology or bed density at this location.