Seasonal stable isotope variations of the modern Amazonian freshwater bivalve Anodontites trapesialis

• Published in: Palaeogeography, palaeoclimatology, palaeoecology palaeoclimatology, palaeoecology, 2003-05, Vol.194 (4), p.339-354
• Main Authors: Kaandorp, Ron J.G., Vonhof, Hubert B., Del Busto, Cahuide, Wesselingh, Frank P., Ganssen, Gerald M., Marmól, Andrés E., Romero Pittman, Lidia, van Hinte, Jan E.
• Format: Article
• Language: English
• Subjects: Amazonas Peru; Anodontites trapesialis; atmospheric precipitation; Bivalvia; evaporation; Freshwater; stable isotopes
• ISSN: 0031-0182; 1872-616X
• DOI: 10.1016/S0031-0182(03)00332-8

In a floodplain lake of the Amazon River near the city of Iquitos, northeastern Peru, a one-year monitoring experiment was conducted during which water samples and living bivalves ( Anodontites trapesialis) were collected with the aim to investigate seasonal δ 18O variation in and fractionation between bivalve aragonite and host water. Both host water and molluscan growth increments show more than 8‰ seasonal variation in δ 18O. In the floodplain lake under study the δ 18O variation of the water is controlled by contrasting dry and wet season evaporation–precipitation regimes. Molluscan δ 18O appears to be in equilibrium with the host water. Although an approximately 4.0‰ offset occurs, δ 13C records of water and bivalves are in good agreement, suggesting that both δ 18O and δ 13C of the shells of freshwater bivalve A. trapesialis are good recorders of (palaeo-)environmental conditions. The δ 13C of Dissolved Inorganic Carbon (DIC) is governed by plant growth and/or by changes in aquatic chemistry, affecting the DIC pool.