Hydrological and ecological observations along the eastern Beaufort Sea coast of Alaska

The US Beaufort Sea coast is fringed by barrier islands, which enclose numerous bays and lagoons that provide habitat for migratory fish and waterfowl that are essential to the subsistence and culture of Iñupiat communities of northern Alaska. In the eastern Beaufort, in particular, residents of Kaktovik rely heavily on the high benthic productivity of these lagoon systems to support the fish and bird populations that they depend on for subsistence. We monitored aspects of hydrology and ecology in several lagoons in the eastern Alaskan Beaufort Sea coast from 2011 to 2014. Our hydrographic data from continuous in situ measurements of temperature and salinity revealed that lagoons possess unique regimes that vary seasonally and reflect unique hydrologic and geomorphic characteristics. H2O-δ18O and salinity measurements revealed that meteoric water is the dominant source of low-salinity water in all lagoons in June and August, though sea ice melt water was also present. Most differences among lagoons were caused by variation in circulation and connection to adjacent marine waters. We also used stable C and N isotopic analysis to determine trophic structure and assess dependence of fauna on terrestrial (CT) vs. marine sources of carbon, with particular focus on animals widely used by local subsistence hunters. Our mixing model results suggest that terrestrial carbon (CT) may be assimilated by upper trophic level consumers, though marine-derived C sources dominate. For example, 15 - 70% of polar bear and 0 - 60% of beluga whale carbon was of terrestrial origin. Our results suggest that 1) CT assimilated by benthic omnivorous invertebrates is transferred to the highest trophic levels in the Beaufort Sea, and 2) arctic cod are the most likely intermediary for transferring CT from lower to upper trophic levels.