LTREB Renewal: Climate driven acidification in lowland Neotropical streams: building on a 30-year study of groundwater-surface water interactions

LTREB 更新：气候驱动的低地新热带溪流酸化：以 30 年地下水与地表水相互作用研究为基础

• 批准号: 2154228
• 负责人: Luis Ramirez-Ulate
• 金额: $ 59.74万
• 依托单位: North Carolina State University
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2022
• 资助国家: 美国
• 起止时间: 2022-04-15 至 2027-03-31
• 项目状态: 未结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=2154228&HistoricalAwards=false
• 关键词: LTREB; Renewal; Climate; driven; acidification

Ongoing long-term studies in Costa Rica streams have found strong implications of drought on the relationship between the water chemistry and the adjacent forest soils. Prior long-term studies in environmental biology uncovered the occurrence of acidification events in these lowland streams. Acidification events are short periods, from hours to days, when the water becomes moderately acid (low pH values). Their occurrence is the result of interactions between the stream and the surrounding forest and result from changes in rainfall. During the dry season organic materials accumulate on the forest floor, when the rains start these materials breakdown, releasing carbon dioxide that moves with the water into streams, creating acid conditions in streams (or lowering the water pH). Acidification events become extreme during El Niño years, which in Costa Rica has drier and wetter seasons than normal. Changes in acidification affect how streams function and the associated stream biodiversity. Projected changes in rainfall associated with global climate change could exacerbate the effects of acidification events on stream ecosystems. Prior research in lowland streams in Costa Rica indicate that stream invertebrates and algae can withstand moderately acid conditions, but are affected when conditions are extreme or more frequent. This Long-term Research in Environmental Biology (LTREB) award will investigate acidification effects on stream ecosystems in lowland Costa Rica. Research will take place at La Selva Biological Station, on the Caribbean slope of Costa Rica, where streams have been under study for more than 30 years. The main objective of this award is to understand the mechanisms and consequences of changing rainfall patterns on the acidity and biotic response of tropical streams. This study would provide training opportunities for graduate students as well as outreach to the public.This award will explore the consequences of the episodic acidification events and the hypothesis that an influx of soil-derived CO2 via subsurface flow paths contributes to those pH declines, signaling a tight coupling among rainfall, terrestrial, and aquatic ecosystems. Climate-driven acidification events are stronger and more common in solute-poor, poorly-buffered, streams than in solute-rich, well-buffered, streams - another characteristic of the study landscape. The award will continue evaluating this hypothesis by addressing three main objectives: (1) to assess relations among daily, seasonal, annual, and decadal patterns in stream water chemistry with major climate events (e.g., El Niño and La Niña - ENSO), focusing on extreme events using high frequency sampling. (2) Assess biotic responses to climate-driven acidification, focusing on event duration under laboratory conditions. Finally, (3) to supplement the experimental buffering of a low-solute stream with laboratory experiments of individual taxa. An analysis of the long-term records of stream macroinvertebrates indicates an overall decline in insects and strong differences in assemblage composition between solute-poor, poorly-buffered, streams compared to solute-rich, well-buffered, streams. Climate trends and global circulation models predict changes in the frequency and intensity of weather extremes. For Central America, models predict greater seasonality, similar to patterns observed during ENSO years. In the Caribbean lowlands of Costa Rica, El Niño events result in abnormally low precipitation during the dry season, while La Niña results is high precipitation. Thus, the award will advance the understanding of the consequences of extreme climate events on tropical lowland stream ecosystems.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.

对哥斯达黎加溪流正在进行的长期研究发现，干旱对水化学与邻近森林土壤之间的关系有很大影响。之前的环境生物学长期研究发现，这些低地溪流中发生了酸化事件。它们的发生是由于溪流与周围森林之间的相互作用以及旱季有机物质在地面上积累的结果，从几小时到几天不等。森林地面，当雨开始时这些物质分解，释放出二氧化碳，随水进入溪流，在溪流中形成酸性条件（或降低水的 pH 值），在厄尔尼诺现象期间，酸化事件变得极端，哥斯达黎加的季节比正常情况更干燥和更湿润。酸化影响河流的功能和相关河流的生物多样性，预计与全球气候变化相关的降雨量变化可能会加剧酸化事件对哥斯达黎加低地生态系统的影响。能够承受中等酸性条件，但在极端或更频繁的条件下会受到影响。这项环境生物学长期研究 (LTREB) 奖项将调查酸化对哥斯达黎加低地河流生态系统的影响。研究将在拉塞尔瓦生物站进行。该奖项的主要目的是研究降雨模式变化对热带溪流酸度和生物反应的机制和影响。培训机会该奖项将探讨间歇性酸化事件的后果，以及土壤中的二氧化碳通过地下流动路径流入导致 pH 值下降的假设，表明降雨、陆地和水生生态系统中，气候驱动的酸化事件在溶质贫乏、缓冲不良的溪流中比在溶质丰富、缓冲良好的溪流中更强烈、更常见——这是该研究的另一个特点。该奖项将通过解决三个主要目标来继续评估这一假设：（1）评估河流水化学的每日、季节性、年度和十年模式与主要气候事件（例如厄尔尼诺和拉尼娜 - ENSO）之间的关系。 ，重点关注使用高频采样的极端事件。（2）评估生物对气候驱动的酸化的反应，重点关注实验室条件下的事件持续时间，（3）通过实验室实验补充低溶质流的实验缓冲。个人对河流大型无脊椎动物的长期记录的分析表明，与溶质丰富、缓冲良好的河流相比，昆虫数量总体下降，且溶质贫乏、缓冲不良的河流之间的组合组成存在显着差异。全球环流模型预测中美洲极端天气的频率和强度的变化，与厄尔尼诺事件在哥斯达黎加加勒比海低地观测到的模式类似。旱季降水量异常低，而拉尼娜现象的结果是降水量高。因此，该奖项将促进人们对极端气候事件对热带低地溪流生态系统影响的理解。该奖项反映了 NSF 的法定使命，并被认为是值得的。通过使用基金会的智力优势和更广泛的影响审查标准进行评估来提供支持。

项目成果

Can we see the nitrate from the trees? Long-term linkages between tropical forest productivity and stream nitrogen concentrations

我们能从树上看到硝酸盐吗？

• DOI: 10.1007/s10533-023-01030-1
• 发表时间: 2023
• 期刊: Biogeochemistry
• 影响因子: 4
• 作者: Ardón, Marcelo;Clark, Deborah A.;Marzolf, Nicholas S.;Ramirez, Alonso;Pringle, Catherine M.
• 通讯作者: Pringle, Catherine M.