• Energy Research

Lake sediments are the physical remnants of past allochthonous and autochthonous carbon and mineral inputs and therefore have the potential to illuminate both past terrestrial carbon cycling and wi...

Abstract Acid rain has the potential to significantly impact the quantity and quality of dissolved organic matter (DOM) leached from soil to groundwater. Yet, to date, the effects of acid rain have not been investigated in karstic systems, which are expected to strongly buffer the pH of atmospheric rainfall. This study presents a nine-year DOM fluorescence dataset from a karst unsaturated zone collected from two drip sites (HS4, HS6) in Heshang Cave, southern China between 2005 and 2014. Cross-correlograms show that fluorescence intensity of both dripwaters lagged behind rainfall by ∼1 year (∼11 months lag for HS4, and ∼13 months for HS6), whereas drip rates responded quite quickly to rainfall (0 months lag for HS4, and ∼3 months for HS6), based on optimal correlation coefficients. The rapid response of drip rates to rainfall is related to the change of reservoir head pressure in summer, associated with higher rainfall. In winter, low rainfall has a limited effect on head pressure, and drip rates gradually slow to a constant value associated with base flow from the overlying reservoir- this effect being most evident on inter-annual timescales (R2 = 0.80 for HS4 and R2 = 0.86 for HS6, n = 9, p

AbstractGroundwater is a vital ecosystem of the global water cycle, hosting unique biodiversity and providing essential services to societies. Despite being the largest unfrozen freshwater resource, in a period of depletion by extraction and pollution, groundwater environments have been repeatedly overlooked in global biodiversity conservation agendas. Disregarding the importance of groundwater as an ecosystem ignores its critical role in preserving surface biomes. To foster timely global conservation of groundwater, we propose elevating the concept of keystone species into the realm of ecosystems, claiming groundwater as a keystone ecosystem that influences the integrity of many dependent ecosystems. Our global analysis shows that over half of land surface areas (52.6%) has a medium‐to‐high interaction with groundwater, reaching up to 74.9% when deserts and high mountains are excluded. We postulate that the intrinsic transboundary features of groundwater are critical for shifting perspectives towards more holistic approaches in aquatic ecology and beyond. Furthermore, we propose eight key themes to develop a science‐policy integrated groundwater conservation agenda. Given ecosystems above and below the ground intersect at many levels, considering groundwater as an essential component of planetary health is pivotal to reduce biodiversity loss and buffer against climate change.