The world's most extensive and active deltas, Louisiana's wetlands, are deteriorating rapidly due to multiple stressors. Their ecological and anthropogenic histories on a multimillennial timescale have not been thoroughly documented. This study investigates hydrological and anthropogenic impacts on southern Louisiana wetlands to guide future efforts toward environmental restoration. A 3.6 m sediment core (JOYWMA) extracted from a freshwater wetland adjacent to Lake Pontchartrain yielded a 5000-year record. Multiproxy data indicate four distinct stages, with the earliest period representing an oyster reef (~4.5 cal yr bp) marked by elevated Ca and Sr concentrations. Evolution to a freshwater marsh occurred 4.5–4.0 cal yr bp during the St. Bernard delta progradation, marked by increased Zr and Br concentrations. The site transitioned to a lake due to the isolation from the St. Bernard delta and local subsidence (4.0–2.0 cal yr bp), marked by increased Ti, Fe, Mn and K concentrations. The site altered to a cypress swamp after 2.0 cal yr bp due to increased sediment supply during the St. Bernard subdelta progradation. Both natural (delta progradation and subsidence) and anthropogenic (fire, deforestation) stressors have impacted the site over the last 4500 years. Delta-switching of the Mississippi River caused the significant geomorphological and ecological changes.

中文翻译：

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路易斯安那州南部淡水湿地的全新世环境史：三角洲发展、海岸演化和人类活动的沉积记录

世界上最广泛和最活跃的三角洲，路易斯安那州的湿地，由于多重压力因素正在迅速恶化。他们在千年时间尺度上的生态和人为历史还没有被彻底记录下来。这项研究调查了路易斯安那州南部湿地的水文和人为影响，以指导未来的环境恢复工作。从庞恰特雷恩湖附近的淡水湿地中提取的 3.6 m 沉积物芯 (JOYWMA) 创造了 5000 年的记录。Multiproxy 数据表明四个不同的阶段，最早的时期代表牡蛎礁（~4.5 cal yr bp），以 Ca 和 Sr 浓度升高为标志。4.5–4.0 cal yr bp进化为淡水沼泽在圣伯纳德三角洲进积过程中，以 Zr 和 Br 浓度增加为标志。由于与圣伯纳德三角洲的隔离和局部沉降（4.0-2.0 cal yr bp），该地点转变为湖泊，以 Ti、Fe、Mn 和 K 浓度增加为标志。由于圣伯纳德亚三角洲进积期间沉积物供应增加，该地点在 2.0 cal yr bp后变成了柏树沼泽。在过去的 4500 年中，自然（三角洲退化和沉降）和人为（火灾、森林砍伐）压力因素都影响了该地点。密西西比河的三角洲转换引起了显着的地貌和生态变化。