We reconstruct environmental conditions of the period 53-14 kyr BP in the continental northern Neotropical region. We evaluate in detail the magnitude of climatic fluctuations and their effects on aquatic communities during six Heinrich Stadials (HS1-HS5a), using sediments from Lake Petén Itzá Guatemala, and a multiproxy approach. In Lake Petén Itzá typical Heinrich Stadials (HSs) are recorded in sediments as alternations of gypsum and clay, and abrupt changes in magnetic susceptibility, CaCO3 and biological compositions. This suggests that HSs were periods of hydrological unbalance, characterized by dry spells, punctuating the predominant humid conditions characterizing the period 53-14 kyr BP. The ultrastructure of HSs allows us to identify four different types of climatic conditions associated to HSs: 1) prevailing dry conditions but changing to humid (HS5, HS3); 2) predominantly humid conditions but changing to arid (HS2); 3) fluctuating humid-dry-humid (HS4, HS1); and 4) arid with high lake water conductivity (HS5a). The continuous presence of tropical ostracode species during HSs suggests that lake water temperatures were not drastically lowered. Ostracode-based transfer functions indicate that during HSs, epilimnetic water temperatures decreased by 1–3 °C compared to mean modern temperatures. Lake solute composition and conductivity were strongly affected by HSs. During HS5a and HS1 we estimate conductivity values > 800 μS cm−1. Diversity indices show significant differences (F5,70 = 3.74, p = 0.004) of ostracode species composition among HSs. Highest diversities occurred during HS5a, HS4 and HS1, which display greater climatic alterations than the other HSs. Fluctuating climates seem to have exerted positive effects on diversity of aquatic communities by producing an increase in habitat heterogeneity.
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The student team from the Instituto Tecnológico de Chetumal (México): Christian Vera, León E. Ibarra, Miguel A. Valadéz, Cuauhtémoc Ruiz. Ramón Beltrán (Centro Interdisciplinario de Ciencias Marinas, México) and Lisa Heise (Universidad Autónoma de San Luis Potosí, México) all deserve thanks for their excellent work in the field. We thank Manuel Elías (El Colegio de la Frontera sur, Chetumal Unit, México), Margarita Caballero, Socorro Lozano (Instituto de Geología, Universidad Nacional Autónoma de México, UNAM), Alexis Oliva and the team from the Asociación de Municipios del Lago de Yojoa y su área de influencia (AMUPROLAGO, Honduras), María Renée Álvarez, Margarita Palmieri, Eleonor de Tott, Roberto moreno (Universidad del Valle de Guatemala, Guatemala), Consejo Nacional de Áreas Protegidas (CONAP, Guatemala), Néstor Herrera and Ministerio de Medio Ambiente (San Salvador, El Salvador). Funding was provided by the Deutsche Forschungsgemeinschaft (DFG, SCHW 671/16-1 , KU 2685/3-1 ), Technische Universität Braunschweig , Institut de Recherche pour le Développement and the Polish Ministry of Science (Grant NCN 2014/13/B/ST10/02534 ). CONACYT (Mexico) provided fellowships ( 218604 , 218639 ) to the first two authors.
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- Central America
- Multiproxy approach
- Transfer functions
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