Food Webs in Flux: Trophic Ecology in Glacially Influenced Estuaries of Southeast Alaska

Estuaries are highly productive mixing zones at the intersection of the terrestrial, freshwater, and marine environments. In Southeast Alaska, numerous ecologically and economically important species use these areas. Receding glaciers and changes in rainfall predicted in climate change models for Southeast Alaska will affect the delivery and volume of freshwater and nutrients to estuaries, potentially altering the composition, functioning, and productivity of estuarine food webs. There are gaps in our understanding of how these effects will play out in estuaries given their dynamic nature and the scarcity of baseline information. This study contributes to our understanding of this variability through identifying food web linkages and energy flow in three glacially influenced estuaries. We studied diets of estuarine fishes including Pacific staghorn sculpin (Leptocottus armatus), starry flounder (Platichthys stellatus), and Dolly Varden (Salvelinus malma) using analysis of similarity and nonmetric multidimensional scaling to examine temporal and spatial variation in diets. The diets capture seasonal changes in prey composition and variation between sites. The diet analysis will be used in conjunction with our stable isotope (carbon, nitrogen, and sulfur) analyses to examine feeding habits and the relative importance of organic matter delivered from adjacent terrestrial and freshwater to systems to estuarine fishes.