Physical and chemical characteristics of ephemeral pond habitats in the Maracaibo basin and Llanos region of Venezuela
Physical and chemical variables of ephemeral rainwaterpond habitats in the Maracaibo basin and Llanos regionof Venezuela were investigated to assess environmentalfeatures important for future studies of thephysiological ecology and bioenergetics of annualkillifish. Dissolved oxygen, temperature, pH, Eh, andconductivity measurements were made in the field ateach collection site. Water and filter samples werecollected and analyzed for trace metals, cations,anions, and osmolality. Physical and chemicalcharacteristics of rainwater ponds are highly variableboth temporally and spatially. Large diurnalfluctuations occur in temperature and dissolvedoxygen. Dissolved oxygen content, temperature, pH andconductivity values exhibit a high degree of interpoolvariation. All pools sampled have a high amount ofsuspended solids consistent with high turbidity. Poolsediments appear to be anoxic as indicated bymeasurement of Eh. Llanos region pools are dominatedby calcium as the major cation, while Maracaibo basinpools are dominated by sodium as the major cation. Maracaibo pools can be further separated into twodistinct regions, inland savanna and coastal desert,based on ionic composition. Annual killifishinhabiting ephemeral ponds may be exposed to extremesin dissolved oxygen concentration, temperature and pHvalues during adult, juvenile, and embryonic stages.
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