Effects of Abrupt Climate Change on Ice Age Ecosystem of Lake Petén Itzá and on Distribution Patterns of Ostracodes across the Yucatán Peninsula
Final Report Abstract
Tropical regions are important components of the Earth system as they control the distribution of the incoming radiant energy, are responsible for one-third of the global terrestrial net primary production and represent the largest reservoir of biodiversity. How tropical regions react to long-term and abrupt climate changes, and what implications this has for the environment, is one of the most uncharted ecological topics globally. This study aimed to reconstruct the environmental history of the last ~400 ka BP in the northern Neotropical region. Sediment cores from Lake Petén Itzá and a multiproxy approach were used to test qualitatively and quantitatively the magnitude of climatic alterations during Marine Isotope Stages (MIS) and episodes of abrupt climate change. Furthermore, using freshwater ostracodes as model group the responses of aquatic communities to such changes were evaluated. First, a limnological survey to calibrate biological and geochemical proxies was conducted. Bedrock type, elevation (representing temperature), precipitation-evaporation balance and the influence of marine environments were the main controls of limnological properties of aquatic ecosystems. Freshwater ostracodes as bioindicators were calibrated by determining species distribution and ecological niche optima and tolerances. Diversity of three of the most frequent groups in fossil records, Darwinulidae, Cypretta and Cypridopsis, were evaluated using an integrative approach, combining morphological, molecular and ecological evidences. Six hidden species were detected in three clades previously considered as widely distributed nominal species. All these species correlate with specific environmental conditions thus refining interpretations of fossil assemblages. Using the geochemical and biological indicators, we reconstructed the climatic and environmental history of the northern Neotropical region. Lithological and geochemical evidence suggest that Lake Petén Itza was an open-basin lake from ~400 to 85 ka BP and changed to a closed-basin lake at around 85 ka. During MIS 11 to MIS 5 environmental fluctuations at Lake Petén Itzá follow global temperature trends observed in ice core records, i.e. cold Glacials and warm Interglacials. Precipitation regimes were highly variable as suggested by lake level high and low stands occurring during both Glacials and Interglacials. Periods of low lake levels were detected during MIS 11 and MIS 7. Inferred littoral conditions at site PI-1 imply a lake level decrease of around 30 m during these periods. MIS 5, MIS 4 and early MIS 3 were periods of relative climatic stability. Late MIS 3, MIS 2 and MIS 1 were periods characterized by frequent abrupt climatic changes such as the period from 85 to 84 ka BP, Heinrich Stadials (HS1-HS6) and the Younger Dryas. Detailed analysis of HSs suggests that climatic conditions were extremely dry, thus abruptly disrupting the predominantly wet conditions characterizing the last glaciation. Ostracode-based transfer functions (RMSEP= 0.78°C) indicate that water temperatures were not drastically affected during HSs, likely decreasing by 1-3°C during the coldest phases compared to present-day values. In contrast, lake water solute composition and conductivity were strongly affected, especially during HS5a and HS1, where estimated values increase to >800 µS cm^-1. The overall response of aquatic biological assemblages during HSs is assumed as moderately, because tropical species prevailed during all stadials in Lake Petén Itzá. An episode of species replacement on centennial scale was observed during the HS5a, associated to the increase of solute concentration in the lake waters. The ostracode-based results did not confirm the extreme cooling of the Neotropics of up to 10°C during HS as suggested by Hodell et al. (2012) but rather support a relatively stable climate, low velocities of climate change and low disruptions of the aquatic ecosystems in the northern Neotropical region, even during periods of global strong climatic alterations, similarly as observed globally for most tropical areas.
Publications
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2014. Modern ostracodes from central america as models for paleoenvironmental reconstructions, a proxy calibration. LOTRED-SA 3rd International Symposium “Climate change and human impact in Central and South America over the last 2000 years: Observation and Models” (Medellín, Colombia)
Macario, L., Cohuo, S., Pérez, L., Schwalb, A.
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2015. Integrating Biogeography, Ecology, Taxonomy and Molecular Analysis for the Improvement of ostracode-based Environmental Reconstructions in the Northern Neotropics. The Sixth International Limnogeology Congress (Tahoe, Nevada, USA)
Macario L., Cohuo S., Perez L., Vences M., Schwalb A.
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2016. A 400-ka tephrochronological framework for Central America from Lake Petén Itzá (Guatemala) sediments. Quaternary Science Reviews 150, 200-220
Kutterolf, S., Schindlbeck, J.C., Anselmetti, F.A., Ariztegui, D., Brenner, M., Curtis, J., Schmid, D., Hodell, D.A., Mueller, A., Pérez, L., Schwalb, A., Frische, M., Wang, K.-L.
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2016. Ecology of Cladocera species from Central America based on subfossil assemblages. Advances in Oceanography and Limnology, 7, 2, 145-156
Wojewódka, M., Zawisza, E., Cohuo, S., Macario-González, L., Schwalb, A., Zawiska, I., Pérez, L.
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2016. Linking altitudinal effects of current biota with modeled scenarios and paleo-records of freshwater ostracodes from the Neotropics. European Conference of Tropical Ecology (Göttingen, Germany)
Macario, L., Cohuo, S., Wagner, S., Naumann, K., Pérez, L., Schwalb, A.
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2016. Tracking the history of geographical parthenogenesis in Neotropical freshwater ostracode species (Crustacea, Ostracoda), consequence of climate fluctuations? A view from fossil and molecular data. European Conference of Tropical Ecology. (Göttingen, Germany)
Cohuo, S., Macario, L., Elías-Gutiérrez, M., Pérez, L., Vences, M, Schwalb, A.
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2017. Overview of Neotropical- Caribbean freshwater ostracode fauna (Crustacea, Ostracoda): identifying areas of endemism and assessing biogeographical affinities. Hydrobiologia 786, 1, 5–21
Cohuo, S., Macario-González, L., Pérez, L., Schwalb, A.
