Ochi Agostini, Vanessa Ritter, Matias do Nascimento José Macedo, Alexandre Muxagata, Erik Erthal, FernandoĮmpty mollusk shells may act as colonization surfaces for sclerobionts depending on the physical, chemical, and biological attributes of the shells. What determines sclerobiont colonization on marine mollusk shells? Carbon isotopes in biogenic carbonates are clearly complex, but cautious interpretation can provide a wealth of information, especially after vital effects are better understood. Ca2+ ATPase-based models of calcification physiology developed for corals and algae likely apply to mollusks, too, but lower pH and carbonic anhydrase at the calcification site probably suppress kinetic isotope effects. Shell Î♁3C retains clues about processes such as ecosystem metabolism and estuarine mixing. Shell Î♁3C is typically a few ‰ lower than ambient DIC, and often decreases with age. Fluid exchange with the environment also brings additional dissolved inorganic carbon (DIC) into the calcification site. Respired CO2 contributes less to the shells of aquatic mollusks, because CO2/O2 ratios are usually higher in water than in air, leading to more replacement of respired CO2 by environmental CO2. Shell Î♁3C is typically >10‰ heavier than diet, probably because respiratory gas exchange discards CO2, and retains the isotopically heavier HCO3. Land snails construct their shells mainly from respired CO2, and shell Î♁3C reflects the local mix of C3 and C4 plants consumed. In this review, we use both published and unpublished data to discuss carbon isotopes in both bivalve and gastropod shell carbonates. Mollusk shells contain many isotopic clues about calcification physiology and environmental conditions at the time of shell formation. Carbon isotopes in mollusk shell carbonates
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