Response of testate amoeba assemblages to environmental and climatic changes during the Lateglacial-Holocene transition at Lake Lautrey (Jura Mountains, eastern France)
Résumé
High resolution multi-proxy studies on a sediment sequence from Lake Lautrey (Jura Mountains, eastern France) gave a palaeoenvironmental data base for the present study. Thus, this sequence offered the opportunity to test the response of lacustrine testate amoebae to climate changes for the Lateglacial-Holocene transition. Testate amoeba assemblages showed variations to successive climatic events at Lake Lautrey. On one hand, changes in the composition of testate amoeba assemblages (dominating species and assemblage structure), as well as in the accumulation rate (tests/cm²/year) corresponded to major climatic phases (i.e. Oldest Dryas, Bølling/Allerød Interstadial, Younger Dryas, Preboreal). On the other hand, decreases in the accumulation rate preferentially marked the minor short-lived cooling events, such as Older Dryas event or Gerzensee oscillation. However, the Preboreal oscillation, well registered by other proxies at Lake Lautrey, cannot be recognised in the testate amoeba record. In addition, the influence of environmental factors such as organic matter inputs is highlighted in this study. This work supports the interest of lacustrine testate amoebae for palaeoclimatic reconstructions. Nevertheless, a better understanding of the relation between climate and lacustrine testate amoebae requires (1) further high-resolution studies based on multi-proxy approaches, and (2) the development of modern analogues (present-day ecology of species).