Changes in oxygen 18 as a measure of long‐term fluctuations in tropical lake levels and molluscan populations1

Abstract

In Laguna Chichancanab, the largest closed basin in northern Yucatan, large-scale changes in lake levels have been documented by "0 analyses of snail shell carbonates. A continuous 9-m series of lake sediments has been deposited during the last 8,000 years, whereas a discontinuous sedimentary record extends from 9 m to beyond 12 m in depth. At least one marked hiatus occurred in this older record during which time the lake is thought to have been seasonally dry (or very much reduced in size). The fluctuations are verified by other stratigraphic evidence including absolute numbers of shells, loss on ignition, carbon:nitrogen ratios, and major cations (calcium, magnesium, and sodium).We here consider a new approach to determine lake level stability in tropical, closed lake basins where mean annual temperatures have remained relatively stable in comparison with changes in rates of inflow and evaporation. The general goal is to document long term changes in the lake's water balance and to relate this information to population dynamics of aquatic organisms, particularly benthic molluscs living in the littoral zone. We use "closed lake" to mean a lake which receives inflow from precipitation and its drainage basin but loses water only by evaporation. Many previous studies on lake level stability ( see Richardson 1969 for a review ) have emphasized the need to correlate several independent lines of evidence. This isotopic analysis is another direct approach which can yield unique information unavailable from other types of analyses of closed, tropical lakes.Naturally occurring isotopes of 180 and 14C can be considered tagged atoms and their movements monitored for the long term study of water balance. These iso-'

Historical Biogeography of the New-World Pupfish Genus Cyprinodon (Teleostei: Cyprinodontidae)

“…2) and the wide-ranging maritime clade (2A), which, with one exception, C. tularosa from southcentral New Mexico, occurs in coastal mainland pupfishes of North and South America and islands of the West Indies. The monophyly of the Yucatan clade is consistent with the suggestion from genetic similarities that the coastal species, C. artifrons, was ancestral to the Laguna Chichancanab species flock, a complex of six ecologically diverse taxa that, based on past lake levels (Covich and Stuiver, 1974) and low levels of genetic divergence, might be only 8,000 years old (Humphries, 1984;Strecker et al, 1996).…”

Synchronous interhemispheric Holocene climate trends in the tropical Andes

“…4) (24, 28, 34, 35). Sites that are antiphased with Laguna Blanca include Lake Valencia, Lake Cichancanab (Yucatan Peninsula, Mexico) (36,37), and Lake Miragoane (Haiti) (38,39). In each of these cases, precipitation correlates positively with equatorial Pacific SSTs, explaining their different responses relative to the Andean region.…”

Variacion genetica de Procambarus llamasi (Decapoda: Cambaridae) en la peninsula de Yucatan: evidencia de conectividad en un paisaje fragmentado

“…El tiempo de divergencia entre estos dos haplotipos coincide con un periodo de cambios constantes en el nivel del mar ya que hace 125.000 años el nivel del mar era 7 m más y hace 18.000 de 100 m menos con respecto al nivel actual (Beddows, 2003). Estas fluctuaciones debieron ocasionar grandes cambios en el acuífero de la península de Yucatán que, en el caso de la disminución del nivel mar, debió haber perdido la mayoría de los cuerpos de agua superficiales como lo describe Covich & Stuiver (1974). En este escenario, las poblaciones de P. llamasi debieron haberse contraído a refugios en los que el tamaño poblacional y la variación genética disminuyeron generando cuellos de botella.…”