HR: 0800h
AN: B31D-0615    [Abstracts]
TI: Ontogenic increase of metabolic carbon in freshwater mussel shells
AU: * Gillikin, D P
EM: dagillikin@vassar.edu
AF: Department of Earth Science and Geography, Vassar College, Box 475, 124 Raymond Avenue, Poughkeepsie, NY 12604, United States
AU: Hutchinson, K A
EM: kahutchinson@vassar.edu
AF: Department of Earth Science and Geography, Vassar College, Box 475, 124 Raymond Avenue, Poughkeepsie, NY 12604, United States
AU: Kumai, Y
EM: yusuke.kumai@gmail.com
AF: Department of Biology, Vassar College, 124 Raymond Avenue, Poughkeepsie, NY 12604, United States
AB: The carbon isotopic signature of dissolved inorganic carbon (δ¹³C_DIC) is a powerful tool for understanding biogeochemical cycling. Biological carbonates are a potential tool to reconstruct past δ¹³C_DIC, but are not always easy to decipher. Metabolic carbon can be incorporated in the carbonate and interfere with the environmental signal. The amount of metabolic carbon is usually considered to be low, around 10%, but up to 37% has been reported. Recently, it has been noted that the amount of metabolic carbon incorporated into marine bivalve shells is dependent on the carbon demand during calcification. When the bivalve is young and shell growth is fast they incorporate less metabolic carbon. This is also a time when the total amount of respiring tissues between the valves is small and therefore less metabolic CO₂ is produced in total. When they age, shell growth slows and the amount of tissues increases, and thus total respired CO₂ increases, thereby increasing the amount of metabolic carbon in the shell. We tested to see if this was also the case for freshwater bivalves. Four living individuals of Pyganodon cataracta ranging in size from 21 to 88 mm in height were collected from a 0.5 m² area of a small stream in November 2006. Tissue δ¹³C and δ¹⁵N, the last year of shell carbonate δ¹³C and δ¹⁸O and δ¹³C_DIC were analyzed. From these data, the percent metabolic carbon in each shell was calculated. The δ¹⁸O values were not significantly different between individuals illustrating that similar time is represented in each shell and that they utilized the same water source. δ¹³C on the other hand shows a clear ontogenic decrease, with the older individuals having more negative values indicating a higher metabolic carbon incorporation into the shell. This is consistent with the model described above. Interestingly, the relationship between size and percent metabolic carbon is similar between freshwater and marine bivalves.
DE: 0419 Biomineralization
DE: 0428 Carbon cycling (4806)
DE: 0454 Isotopic composition and chemistry (1041, 4870)
DE: 0473 Paleoclimatology and paleoceanography (3344, 4900)
SC: Biogeosciences [B]
MN: 2007 Fall Meeting