Evaluating growth patterns and element-to-calcium ratios of "Arctica islandica" (Bivalvia) shells as environmental proxies

• Main Author: Marali-Djame-Khiabani, Soraya
• Format: Doctoral or Postdoctoral Thesis
• Language: English
• Published: Johannes Gutenberg-Universität Mainz 2017
• Subjects: ddc:560; Arctica islandica; Iceland; North Atlantic
• Online Access: https://openscience.ub.uni-mainz.de/handle/20.500.12030/3303; https://hdl.handle.net/20.500.12030/3303; https://doi.org/10.25358/openscience-3301

Long-term, coherent, multi-regional records of environmental parameters are needed to quantify the rapidity, persistence and geographic extent of climatic phenomena and/or (extreme) weather events. The aragonitic shell of the long-lived marine bivalve mollusk Arctica islandica records past environmental conditions in the climate-sensitive, extra-tropical North Atlantic Ocean over decades to centuries at an annual or even higher resolution. Due to synchronous shell growth, individual growth records can be stacked together to form so-called composite chronologies. These chronologies provide uninterrupted annual to sub-annual environmental proxy data over several centuries or even millennia. Although previous studies demonstrated that A. islandica shells are reliable paleoclimate archives, there are still research questions. The present study addresses the following issues: (1) Are shells from shallow water specimens also suitable to construct stacked chronologies? (2) Can chronology construction be facilitated and increment-based crossdating be tested by means of geochemical properties? (3) Are environmental factors driving the growth and trace element-to-calcium ratios of A. islandica shells? In the first manuscript of this thesis, it has been demonstrated that the shell growth patterns of A. islandica from shallow (ca. 9 – 23 m), unpolluted waters off northeastern Iceland (1) grew synchronously over discrete time intervals and (2) shell growth responded to the local oceanographic conditions. (3) The degree to which the environmental signals are expressed in the chronology (i.e. the degree of growth synchrony between the specimens) is high, when the environmental year-to-year variability reaches a critical level, the strength of which needs to be determined in future studies. The second and third manuscript explored the trace element-to-calcium ratios of A. islandica shells by means of laser ablation-inductively coupled plasma-mass spectrometry (LA-ICP-MS) in line scan mode. The second article focused on shell ...