Response of diatom communities to climate and human disturbance: A 4200-year record from Costa Rica
Response of diatom communities to climate and human disturbance: A 4200-year record from Costa Rica
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DOI：
10.1177/09596836231197775
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发表时间：
2023-09
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影响因子：
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通讯作者：
Madeleine Bitting;Erik N. Johanson;Kurt A. Haberyan;Sally P. Horn
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作者：
Madeleine Bitting;Erik N. Johanson;Kurt A. Haberyan;Sally P. Horn
本研究将硅藻分析与现有的花粉，木炭，元素组成和稳定的光同位素的记录，以扩大4200年的人类活动和气候变化的历史，从拉古纳洛杉矶芒果在南太平洋哥斯达黎加。我们计算了硅藻在过氧化物处理的样品和分析的社区组成，聚类分析，揭示了四个不同的组合区与硅藻的变化最密切相关的磷，钛，和有机含量。最早的组合（D区，4150-3430卡尔年BP）是由Encyonema silesiacum和Nitzschia incognita为主，并与一个时期的森林砍伐，侵蚀，和丰富的大型植物对齐。Gomphonema affine在C区（3430-2450卡BP）增殖，反映了可能由农业引起的营养负荷引起的pH值和生产力的增加。我们归因于保存的差距从3290至2970卡年BP在C区的二氧化硅耗尽和侵蚀沉积，导致硅藻丰度下降稀释阀浓度在湖泊沉积物。Nitzschia incognita和G.在B带（2450-1400 cal yr BP），affine成为优势类群，可能反映了富营养化、电导率增加和气候干燥。占主导地位的Diadesmis confervacea表示在A区（1400卡BP现代）的发病的终端经典干旱（TCD）的湖泊水位降低。记录中的一个间断表明，从950到450卡年BP的湖泊干燥。在小冰期（LIA），硅藻反映了类似于B区的条件，表明湖泊水位上升，环中性pH值和富营养化。湖泊的重新填充表明在LIA期间降水量增加，尽管有证据表明其他地点报告了严重的区域干旱。在此期间，降水量的变化可能是由于西班牙的接触，农业崩溃，森林恢复，以及大西洋和太平洋气候强迫机制的变化的综合影响。总的来说，Los Mangos的硅藻记录反映了浅，微碱性，富营养化条件的影响，营养富集，侵蚀和森林砍伐与玉米农业。
This study integrates diatom analysis with existing records of pollen, charcoal, elemental composition, and stable light isotopes to expand upon the 4200-year history of human activity and climate change from Laguna Los Mangos in southern Pacific Costa Rica. We counted diatoms in peroxide-treated samples and analyzed community composition using cluster analysis, revealing four distinct assemblage zones with diatom variability most closely correlated with phosphorus, titanium, and organic content. The earliest assemblage (Zone D, 4150–3430 cal yr BP) was dominated by Encyonema silesiacum and Nitzschia incognita and aligned with a period of deforestation, erosion, and abundant macrophytes. Gomphonema affine proliferated in Zone C (3430–2450 cal yr BP), reflecting increased pH and productivity likely caused by agriculture-induced nutrient loading. We attributed the preservation gap from 3290 to 2970 cal yr BP in Zone C to silica depletion and erosional deposition that induced decline in diatom abundance by diluting valve concentrations in lake sediments. Nitzschia incognita and G. affine became the dominant taxa in Zone B (2450–1400 cal yr BP), likely reflecting eutrophy, increasing conductivity, and drying climate. Dominance of Diadesmis confervacea indicated reduced lake level in Zone A (1400 cal yr BP–modern) at the onset of the Terminal Classic Drought (TCD). A hiatus in the record indicates lake desiccation from 950 to 450 cal yr BP. During the Little Ice Age (LIA), diatoms reflect conditions similar to Zone B indicating increased lake level, circumneutral pH, and eutrophy. Refilling of the lake indicates increased precipitation during the LIA despite evidence of severe regional drought reported at other sites. Variable precipitation during this period likely resulted from the combined effects of Spanish contact, agricultural collapse, forest recovery, and shifts in Atlantic and Pacific climate forcing mechanisms. Overall, the Los Mangos diatom record reflects shallow, slightly alkaline, eutrophic conditions influenced by nutrient enrichment, erosion, and deforestation associated with maize agriculture.