Toxic mercury, aquatic ecosystem collapse, and the ancient Lowland Maya.

Classic Period sediment cores from two Yucatán Peninsula lakes show mercury concentrations exceeding modern Hg toxicity thresholds by orders of magnitude for centuries during ancient Maya occupation.

• Why it matters: The Lowland Maya faced multiple environmental stressors, but the specific toxicity and ecosystem consequences of prehistoric mercury exposure remained unclear.
• What they did: The study measured mercury levels in lake sediment cores and compared them with modern sediment Hg toxicity thresholds, then checked for aquatic food web collapse signals over the same intervals.
• The result: Evidence of collapse across algae, bacteria, cyanobacteria, ostracods, snails, and nonbiting midges coincided with periods of high Hg, supporting Hg toxicity as an added stressor for Classic Maya populations.

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