The distribution, magnitude, and endemic species of US springs

Frontiers in Environmental Science, 2023

Editorial on the Research Topic Threatened aquatic gems: freshwater springs and groundwaterdependent ecosystems Groundwater constitutes the Earth's largest liquid freshwater reserve (Stephens et al., 2020). Although awareness is growing that human water demands threaten finite groundwater resources worldwide (Bierkens and Wada, 2019), there remains a dearth of information on how those water demands impact terrestrial and aquatic groundwaterdependent ecosystems (GDEs), including springs. Groundwater withdrawals have reduced inputs to GDEs even in high rainfall areas (Work, 2020), but the threat of groundwater extraction on GDE persistence and condition is especially acute in arid zones where globally, groundwater extraction already exceeds recharge (Aeschback-Hertig and Gleeson, 2012). Worldwide, springs often contain high endemism and can be biodiversity hotspots that contribute to regional biodiversity disproportionate to their size, so ecological consequences of groundwater extraction are potentially severe (Davis et al., 2017). The Research Topic "Threatened Aquatic Gems: Freshwater Springs and Groundwaterdependent Ecosystems" advances our knowledge of the critical role that GDEs play in maintaining biodiversity, and highlights research and conservation strategies needed to protect GDEs, especially in a warming climate. Arid-zone springs have been called "precious jewels of the desert", a reflection of their vulnerability and ecologic importance (Box et al., 2008). The arid spring ecosystems investigated by Fensham et al. in Australia, the southwestern US and Mexico exemplify this vulnerability, as they harbor some of the highest documented concentrations of endemic species in the world. The high endemism of these systems highlights the importance of stability and permanence over evolutionary timescales (up to 47 MYA, Murphy et al., 2015) in producing and maintaining biodiversity. To preserve these biodiversity hotspots will require recognition of their importance and the specific land and water uses that affect their persistence. Globally, climate change will significantly stress GDE health, in part due to groundwater recharge reductions in regions with annual rainfall declines (Wu et al., 2020; Schenk and Stevens, 2022). An investigation of Copepoda from karst springs in Italy by Cerasoli et al.

Ecological Indicators, 2020

Bellunesi, eastern Alps, Italy) a s t ypical f or a quatic h abitats characterized by d olostone i nfluence on t heir GW-flow system. The species c ould a lso be c haracterized a s e piphytic (living on p lant-like substratum, f or i nstance on bryophytes i n springs, or on vascular plants i n lakes), a nd t ypically i nhabiting t he d epth z one influenced by water-level f luctuations i n lakes a nd springs a ffected by d ischarge f luctuations (Cantonati e t a l., 2 012). More recently, A. dolomiticum was f ound a lso i n springs e merging f rom ophiolitic rocks, mainly p eridotite a nd serpen-tinite (Kamberović e t a l., 2 019), and t his c onfirmed a supposed p reference of t he species f or a boveaverage magnesium c oncentrations. 3.3.2. Vascular plants Some aquatic and terrestrial vascular plant species are nearly or entirely restricted to springs. For example, aquatic Texas wild rice (Zizania texana) occurs only along the spring-fed headwaters of the San Marcos River in Texas (Poole and Bowles, 1999). Spring-supported alkaline meadows in Ash Meadows, Nevada support several endemic plant species (i.e., Nitrophila mohavensis and Zeltnera namophilum; Beatley, 1977). Floating-mat and iron-precipitating fens in central Rocky Mountains support populations of the rare roundleaf sundew plants (Drosera rotundifolia; Wolf et al., 2006).

Science of The Total Environment, 2020

This study explores the factors affecting the biodiversity of diatoms, vegetation with focus on bryophytes, and invertebrates with focus on water mites, in a series of 16 spring-habitats. The springs are located primarily from the mountainous part of the Emilia-Romagna Region (Northern Apennines, Italy), and two pool-springs from agricultural and industrial lowland locations. Overall, data indicate that biological diversity (Shannon-Wiener, αdiversity) within individual springs was relatively low, e.g.: S diatoms = 0-46, S water-mites = 0-11. However, when examined at the regional scale, they hosted a very high total number of taxa (γ-diversity; S diatoms = 285, S water-mites = 40), including several new or putatively-new species, and many Red-List taxa. This pattern suggested there is high species turnover among springs, as well as high distinctiveness of individual spring systems. A key goal was to assess the hydrogeological and hydrochemical conditions associated with this high regionalpool species richness, and to provide a guide to future conservation strategies. There was a striking variety of geological conditions (geodiversity, captured mainly with lithotype and aquifer structure) across the study region, which led to wide variation in the hydrosphere, especially in conductivity and pH. Agriculture and industrial activities (anthroposphere) in the lowlands resulted in nutrient enrichment and other forms of pollution. Across all 16 spring-systems, several hydrogeological conditions most strongly influenced the presence or absence of particular biota and were determinants of species importance: spring-head morphology, hydroperiod, discharge, current velocity, and elemental concentration. These findings have important practical consequences for conservation strategies. Our data show that it is imperative to protect entire regional groups of springs, including

2021

Springs are interfaces between groundwater and surface habitats and may play an important role in the study of subterranean animals. In this systematic evidence review and meta-analysis, we explore whether observations of stygobionts in springs are relevant and more common than observations of epigean animals in groundwater. We searched the Web of Science database for papers on groundwater fauna and spring fauna. For each paper we found, we recorded whether the paper reported the occurrence of typical stygobionts in springs, of surface animals in groundwater, or of the same taxa in both habitats. If so, we recorded how many such species were reported. We also recorded the scientific discipline of each study and the year of publication. Our search yielded 342 papers. A considerable number of these papers reported stygobionts in springs: 20% of papers dealing with groundwater fauna and 16% of papers dealing with spring fauna reported the occurrence of stygobionts in spring habitats. Both the number of papers that mentioned stygobionts in springs, and the number of stygobiont species that were documented in springs, were higher than equivalent measures for the occurrence of surface fauna underground. We also detected a positive relationship between year of publication and the number of reports of stygofauna in springs. To broaden the insights from biological research on underground environments, we suggest that springs should be considered not only as simple sampling points of stygobionts but also as core stygobiont habitats.

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2010

Our report describes the ecological significance of several springs and seeps within Devils Tower National Monument. Special attention is given to the potential restoration of sites that were developed for human use in the early 20th century. Invertebrate assemblages and water quality are characterized and compared between natural and developed springs. Springs that were developed for human use were capped and boxed, essentially cutting them off from the surrounding flora and fauna. Lower taxonomic richness and density in the invertebrate assemblage at capped springs describe the isolation after development. Options for restoration are suggested with regard to minimizing site disturbance. Suggestions for monitoring after restoration are also presented.

Frontiers in Environmental Science

Desert ecosystems are an environment of climatic extremes, to which many forms of life have adapted. These systems are characterized by scarce water and often sparsely vegetated lands where ecological adaptation to arid conditions has its underpinnings in the universal dependency on water to support life. Understanding the ecohydrological similarity of springs in water-limited areas requires integration of multiple lines of evidence from diverse disciplines. A unique dataset of hydrological and ecological characteristics of Mojave and Sonoran Desert spring ecosystems in California has been developed, incorporating a wide range of spring conditions that enables a broad evaluation of similarity in ecohydrological characteristics across springs in the region. The lack of observed correlation between hydrologic and ecological parameters suggests that the springs in the California Desert each represent a somewhat unique ecosystem that has developed in relative isolation from the other sp...