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.

在哥斯达黎加溪流中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关系的影响很大。先前在环境生物学的长期研究发现了这些低地流中酸化事件的发生。酸化事件是短时间的短期，当水变成适度的酸（低pH值）时。它们的发生是溪流与周围森林之间相互作用的结果，以及降雨变化的结果。在干旱季节，有机材料积聚在森林地面上，当降雨开始这些材料崩溃时，释放了二氧化碳，将二氧化碳与水一起流入溪流，从而在溪流中产生酸性条件（或降低水pH值）。在厄尔尼诺时代，酸化事件变得极为明显，在哥斯达黎加，驾驶和潮湿的季节比正常情况。酸化的变化会影响流的功能和相关的流生物多样性。与全球气候变化相关的降雨变化的预计变化可能会加剧酸化事件对溪流生态系统的影响。哥斯达黎加低地流的先前研究表明，溪流无脊椎动物和藻类可以承受适度的酸条件，但在条件极端或更频繁时会受到影响。这项在环境生物学（LTREB）奖中的长期研究将调查对低地哥斯达黎加河流生态系统的酸化影响。研究将在哥斯达黎加加勒比海坡的La Selva生物站进行，那里的流已经研究了30多年。该奖项的主要目的是了解变化降雨模式对热带流的酸度和生物反应的机制和后果。这项研究将为研究生提供培训机会，并向公众提供宣传。该奖项将探讨情节酸化事件的后果以及通过地下流动路径对土壤来源的CO2的影响，这会导致pH值的下降，这表明降雨，地面和水上生态系统之间的紧密结合。气候驱动的酸化事件在固体贫困，缓冲不良，溪流中比固体富裕，良好的溪流（研究景观的另一个特征）更强烈，更常见。该奖项将通过解决三个主要目标来继续评估这一假设：（1）评估溪流水化学中每日，季节性，年度和十年型模式之间的关系与重大气候事件（例如Elniño和LaNiña -enso），重点介绍使用高频采样的极端事件。 （2）评估对气候驱动酸化的生物反应，重点是实验室条件下的事件持续时间。最后，（3）通过单个分类单元的实验室实验来补充低糖流的实验缓冲。对溪流大型无脊椎动物的长期记录的分析表明，与固体富裕，延迟良好的流相比，固体贫困，延迟不良的溪流之间的组合组成的总体差异和强烈的差异。气候趋势和全球循环模型预测了极端天气的频率和强度的变化。对于中美洲而言，模型预测季节性更大，类似于ENSO年期间观察到的模式。在哥斯达黎加的加勒比海低地，厄尔尼诺事件在旱季中导致绝对低降水量，而拉尼娜的结果是很高的降水。这是该奖项将提高对热带低地流生态系统极端气候事件的后果的理解。该奖项反映了NSF的法定任务，并通过使用基金会的知识分子优点和更广泛的影响评估标准来评估值得支持。

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.