| Summary: | Thesis (M.S.) University of Alaska Fairbanks, 1978 Natural abundance ¹³C/¹²C ratios provide a tracer for the origin of organic carbon in complex coastal marine food-webs and also appear to be useful for examining trophic organization and food transfer efficiencies in more strictly oceanic environments. The tracer approach proved useful for analyzing the role of eel-grass (Zostera marina) in the food-web of Izembek Lagoon, Alaska. Both eelgrass and phytoplankton contribute to the productivity of that community. That analysis was complicated by non-ideal tracer behavior, however. Animal ¹³C/¹²C ratios appeared to depend on biochemical composition, and ways to deal with this were investigated. Furthermore, animal metabolism tended to retain ¹³C relative to ¹²C, resulting in progressive elevation of ¹³C/¹²C ratios in higher trophic levels. By assuming a uniform relation between ¹³C enrichment and metabolic stoichiometry, it was possible to deduce animal 'trophic positions' and food transfer efficiencies from ¹³C/¹²C data taken from the Bering Sea 1. Statement of the problem -- Introduction -- Isotope fractionalism in chemical and biochemical systems -- 2. Food-web structure and the fractionation of carbon isotopes in the Bering Sea -- Abstract -- Introduction -- Oceanographic setting -- Methods -- Results -- Biochemical composition of the samples -- Discussion -- Modeling the food-web distribution of carbon isotopes -- Conclusions -- 3. Eelgrass as a food source of marine communities: an evaluation based on carbon isotopic evidence -- Abstract -- Introduction -- Methods -- Results and discussion -- Primary production -- Food-web effects -- Isotopic comparisons between lagoon and ocean animals -- ¹³C/¹²C ratios in the lagoon food-web -- Eelgrass grazers -- Migratory animals -- Conclusions -- 4. Feeding relations of the fish community in Izembek Lagoon -- Abstract -- Introduction -- Study site -- Methods -- Results -- The diets of fishes -- Eelgrass as a primary food source and carbon-13 studies -- Discussion -- ...
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