Data for: Harmful algal blooms and cyanotoxins in Lake Amatitlán, Guatemala, coincided with ancient Maya occupation in the watershed

Human-induced deforestation and soil erosion were environmental stressors for the ancient Maya of Mesoamerica. Furthermore, intense, periodic droughts during the Terminal Classic Period, ca. CE (Common Era) 830-950, have been documented from lake sediment cores and speleothems. Today, lakes worldwide that are surrounded by dense human settlement and intense riparian land use, often develop algae/cyanobacteria blooms that can compromise water quality by depleting oxygen and producing toxins. Such environmental impacts have rarely been explored in the context of ancient Maya settlement. We measured nutrients, biomarkers for cyanobacteria and the cyanotoxin microcystin, in a sediment core from Lake Amatitlán, highland Guatemala, which spans the last ~2100 years. The lake is currently hypereutrophic and characterized by high cyanotoxin concentrations from persistent blooms of the cyanobacterium Microcystis aeruginosa. Our paleolimnological data show that harmful cyanobacteria blooms and cyanotoxin production occurred during periods of ancient Maya occupation. Highest concentrations of cyanotoxins in the sediment coincided with alterations of the water system in the Maya city of Kaminaljuyú, and changes in nutrient stoichiometry and maximum cyanobacteria abundance were coeval with times of greatest ancient human populations in the watershed. These prehistoric episodes of cyanobacteria proliferation and cyanotoxin production rivaled modern conditions in the lake, with respect to both bloom magnitude and toxicity. This suggests that pre-Columbian Maya occupation of the Lake Amatitlán watershed negatively impacted water potability. Prehistoric cultural eutrophication indicates that human-driven nutrient enrichment of water bodies is not an exclusively modern phenomenon, and may well have been a stressor for the ancient Maya.

人为森林砍伐与水土流失，曾是中美洲古玛雅文明所面临的环境压力因子。此外，通过湖泊沉积物岩芯与洞穴碳酸盐沉积（speleothems）的研究记录，学界已证实中美洲古典期晚期曾发生剧烈的周期性干旱事件，时间跨度约为公元830年至950年（Common Era, CE）。如今，全球范围内被密集人类聚落与高强度河岸土地利用环绕的湖泊，常暴发藻类/蓝细菌（cyanobacteria）水华，这类水华会通过消耗水体溶解氧、产生毒素的方式破坏水质。这类环境影响在古玛雅聚落的研究语境中却鲜有涉及。我们对危地马拉高地阿马蒂特兰湖（Lake Amatitlán）一根覆盖过去约2100年的沉积物岩芯展开了分析，测定了其中的营养盐、蓝细菌生物标志物以及蓝藻毒素（cyanotoxin）微囊藻毒素（microcystin）。该湖泊目前处于超富营养化状态，因蓝细菌铜绿微囊藻（Microcystis aeruginosa）持续暴发水华，蓝藻毒素浓度居高不下。我们的古湖沼学（paleolimnology）数据显示，有害蓝藻水华与蓝藻毒素产生的时段，恰好对应古玛雅人在此活动的时期。沉积物中蓝藻毒素的最高浓度峰值，与玛雅城邦卡米纳尔胡尤（Kaminaljuyú）的水系改造时期相吻合；而水体营养盐化学计量比的变化以及蓝细菌丰度的峰值，则与该流域古人类人口规模达到顶峰的时期同期。就水华规模与毒素毒性而言，史前时期的蓝细菌增殖与蓝藻毒素产生事件，其严重程度可与该湖泊当前的状况相媲美。这表明，哥伦布到达美洲前玛雅人对阿马蒂特兰湖流域的开发活动，曾对水体饮用安全性造成负面影响。史前人类活动引发的水体富营养化现象表明，人类驱动的水体营养盐富集并非仅存在于现代社会，其完全可能曾是古玛雅文明所面临的环境压力之一。