A Brief Overview of the GLObal RIver Chemistry Database, GLORICH

AbstractOver the last decade the number of regional to global scale studies of river chemical fluxes and their steering factors increased rapidly, entailing a growing demand for appropriate databases to calculate mass budgets, to calibrate models, or to test hypotheses. We present a short overview of the recently established GLObal RIver CHemistry database GLORICH, which combines an assemblage of hydrochemical data from varying sources with catchment characteristics of the sampling locations. The information provided include e.g. catchment size, lithology, soil, climate, land cover, net primary production, population density and average slope gradient. The data base comprises 1.27 million samples distributed over 17,000 sampling locations

Enhanced Productivity and Fish Abundance at a Submarine Spring in a Coastal Lagoon on Tahiti, French Polynesia

Submarine groundwater discharge (SGD), the direct discharge of groundwater into the sea, is abundant around the globe. Fresh SGD can occur as focused flow in submarine springs. However, little is known on the impact of submarine springs on marine organisms. For a better understanding of the interaction between SGD and its surrounding organisms, the impact of SGD on the abundance of fish was investigated in a coastal lagoon of Tahiti, French Polynesia. The study is based on the assumption of an enhanced biological production due to increased amounts of nutrient input caused by terrestrial groundwater supply into the sea. Biofouling processes and zooplankton samples were used as indicators for elevated nutrient input due to submarine springs. The main objective was to investigate the effect on the abundance of fish assuming a higher fish abundance possibly caused by a bottom-up control. Presented data show a significantly higher abundance around a submarine spring as well as significantly larger growth of algal turfs exposed to groundwater discharge. Zooplankton evaluations suggest slightly higher abundances around the submarine spring. The results suggest elevated nutrient concentrations transmitted by submarine springs may cause a bottom-up control resulting in a higher abundance of fish around the investigated submarine spring

DSi as a tracer for submarine groundwater discharge

© The Author(s), 2019. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Oehler, T., Tamborski, J., Rahman, S., Moosdorf, N., Ahrens, J., Mori, C., Neuholz, R., Schnetger, B., & Beck, M. DSi as a tracer for submarine groundwater discharge. Frontiers in Marine Science, 6, (2019): 563, doi:10.3389/fmars.2019.00563.Submarine groundwater discharge (SGD) is an important source of nutrients and metals to the coastal ocean, affects coastal ecosystems, and is gaining recognition as a relevant water resource. SGD is usually quantified using geochemical tracers such as radon or radium. However, a few studies have also used dissolved silicon (DSi) as a tracer for SGD, as DSi is usually enriched in groundwater when compared to surface waters. In this study, we discuss the potential of DSi as a tracer in SGD studies based on a literature review and two case studies from contrasting environments. In the first case study, DSi is used to calculate SGD fluxes in a tropical volcanic-carbonate karstic region (southern Java, Indonesia), where SGD is dominated by terrestrial groundwater discharge. The second case study discusses DSi as a tracer for marine SGD (i.e., recirculated seawater) in the tidal flat area of Spiekeroog (southern North Sea), where SGD is dominantly driven by tidal pumping through beach sands. Our results indicate that DSi is a useful tracer for SGD in various lithologies (e.g., karstic, volcanic, complex) to quantify terrestrial and marine SGD fluxes. DSi can also be used to trace groundwater transport processes in the sediment and the coastal aquifer. Care has to be taken that all sources and sinks of DSi are known and can be quantified or neglected. One major limitation is that DSi is used by siliceous phytoplankton and therefore limits its applicability to times of the year when primary production of siliceous phytoplankton is low. In general, DSi is a powerful tracer for SGD in many environments. We recommend that DSi should be used to complement other conventionally used tracers, such as radon or radium, to help account for their own shortcomings.TO, NM, and the presented case study 1 were funded through the BMBF junior research group SGD-NUT (grant #01LN1307A). Open access publication fees are paid by Leibniz-Centre for Tropical Marine Research internal funds. The presented case study 2 was financially supported by the DFG Research Group “BioGeoChemsitry of Tidal Flats”, the Ph.D. Research Training Group “The ecology of molecules” funded by the Ministry for Science and Culture of Lower Saxony, and the Institute for Chemistry and Biology of the Marine Environment, University of Oldenburg

Glacial weathering, sulfide oxidation, and global carbon cycle feedbacks

Connections between glaciation, chemical weathering, and the global carbon cycle could steer the evolution of global climate over geologic time, but even the directionality of feedbacks in this system remain to be resolved. Here, we assemble a compilation of hydrochemical data from glacierized catchments, use this data to evaluate the dominant chemical reactions associated with glacial weathering, and explore the implications for long-term geochemical cycles. Weathering yields from catchments in our compilation are higher than the global average, which results, in part, from higher runoff in glaciated catchments. Our analysis supports the theory that glacial weathering is characterized predominantly by weathering of trace sulfide and carbonate minerals. To evaluate the effects of glacial weathering on atmospheric pCO_2, we use a solute mixing model to predict the ratio of alkalinity to dissolved inorganic carbon (DIC) generated by weathering reactions. Compared with nonglacial weathering, glacial weathering is more likely to yield alkalinity/DIC ratios less than 1, suggesting that enhanced sulfide oxidation as a result of glaciation may act as a source of CO_2 to the atmosphere. Back-of-the-envelope calculations indicate that oxidative fluxes could change ocean–atmosphere CO_2 equilibrium by 25 ppm or more over 10 ky. Over longer timescales, CO_2 release could act as a negative feedback, limiting progress of glaciation, dependent on lithology and the concentration of atmospheric O_2. Future work on glaciation–weathering–carbon cycle feedbacks should consider weathering of trace sulfide minerals in addition to silicate minerals

Submarine groundwater discharge: updates on its measurement techniques, geophysical drivers, magnitudes, and effects

The number of studies concerning Submarine Groundwater Discharge (SGD) grew quickly as we entered the twenty-first century. Many hydrological and oceanographic processes that drive and influence SGD were identified and characterized during this period. These processes included tidal effects on SGD, water and solute fluxes, biogeochemical transformations through the subterranean estuary, and material transport via SGD from land to sea. Here we compile and summarize the significant progress in SGD assessment methodologies, considering both the terrestrial and marine driving forces, and local as well as global evaluations of groundwater discharge with an emphasis on investigations published over the past decade. Our treatment presents the state-of-the-art progress of SGD studies from geophysical, geochemical, bio-ecological, economic, and cultural perspectives. We identify and summarize remaining research questions, make recommendations for future research directions, and discuss potential future challenges, including impacts of climate change on SGD and improved estimates of the global magnitude of SGD

Global distribution of carbonate rocks and karst water resources

Karstregionen beinhalten eine Vielzahl natürlicher Ressourcen, wie Süßwasser und Biodiversität, sowie zahlreiche kulturelle und historische Ressourcen. Die Welt-Karstaquifer-Karte (WOKAM) ist die erste detaillierte und vollständige globale Datenbasis über die Verbreitung von verkarstungsfähigen Gesteinen (Carbonate und Evaporite), welche potentielle Karstaquifere darstellen. Diese Studie präsentiert eine statistische Auswertung von WOKAM, mit dem Fokus auf Karst in Carbonatgesteinen, und adressiert vier wesentliche Aspekte: (i) globales Vorkommen und geografische Verteilung von Karst; (ii) Karst in verschiedenen topografischen Settings und in Küstengebieten; (iii) Karst in verschiedenen Klimazonen; und (iv) Bevölkerung in Karstgebieten. Die Analyse ergibt, dass 15,2 % der globalen, eisfreien Kontinentalfläche durch Carbonatgesteine charakterisiert sind. Der höchste prozentuale Anteil tritt in Europa auf (21,8 %); die größte absolute Fläche in Asien (8,35 Mio. km²). Weltweit treten 31,1 % aller anstehenden Carbonatgesteine in Ebenen auf, 28,1 % im Hügelland und 40,8 % in Gebirgen; 151,400 km oder 15,7 % der globalen marinen Küstenlinie wird von Carbonatgesteinen geprägt. Etwa 34,2 % aller Carbonatgesteine kommen im ariden Klima vor, gefolgt von 28,2 % in kalten und 15,9 % in gemäßigten Klimaten, während nur 13,1 % bzw. 8,6 % im tropischen bzw. polaren Klima anzutreffen sind. Global leben etwa 1,18 Milliarden Menschen (16,5 % der Weltbevölkerung) in Karstgebieten. Die höchste absolute Anzahl wurde in Asien ermittelt (661,7 Mio.), während die höchsten prozentualen Anteile in Europa (25,3 %) und Nordamerika (23,5 %) auftreten. Diese Ergebnisse zeigen die globale Bedeutung von Karst und dienen als Basis für weitere Forschung und internationale Wassermanagement-Strategien

Global distribution of carbonate rocks and karst water resources

Karstregionen beinhalten eine Vielzahl natürlicher Ressourcen, wie Süßwasser und Biodiversität, sowie zahlreiche kulturelle und historische Ressourcen. Die Welt-Karstaquifer-Karte (WOKAM) ist die erste detaillierte und vollständige globale Datenbasis über die Verbreitung von verkarstungsfähigen Gesteinen (Carbonate und Evaporite), welche potentielle Karstaquifere darstellen. Diese Studie präsentiert eine statistische Auswertung von WOKAM, mit dem Fokus auf Karst in Carbonatgesteinen, und adressiert vier wesentliche Aspekte: (i) globales Vorkommen und geografische Verteilung von Karst; (ii) Karst in verschiedenen topografischen Settings und in Küstengebieten; (iii) Karst in verschiedenen Klimazonen; und (iv) Bevölkerung in Karstgebieten. Die Analyse ergibt, dass 15,2 % der globalen, eisfreien Kontinentalfläche durch Carbonatgesteine charakterisiert sind. Der höchste prozentuale Anteil tritt in Europa auf (21,8 %); die größte absolute Fläche in Asien (8,35 Mio. km²). Weltweit treten 31,1 % aller anstehenden Carbonatgesteine in Ebenen auf, 28,1 % im Hügelland und 40,8 % in Gebirgen; 151,400 km oder 15,7 % der globalen marinen Küstenlinie wird von Carbonatgesteinen geprägt. Etwa 34,2 % aller Carbonatgesteine kommen im ariden Klima vor, gefolgt von 28,2 % in kalten und 15,9 % in gemäßigten Klimaten, während nur 13,1 % bzw. 8,6 % im tropischen bzw. polaren Klima anzutreffen sind. Global leben etwa 1,18 Milliarden Menschen (16,5 % der Weltbevölkerung) in Karstgebieten. Die höchste absolute Anzahl wurde in Asien ermittelt (661,7 Mio.), während die höchsten prozentualen Anteile in Europa (25,3 %) und Nordamerika (23,5 %) auftreten. Diese Ergebnisse zeigen die globale Bedeutung von Karst und dienen als Basis für weitere Forschung und internationale Wassermanagement-Strategien

A Typology for Reef Passages

Coral reefs host exceptionally diverse and abundant marine life. Connecting coasts and sheltered lagoons to the open ocean, reef passages are important yet poorly studied components of these ecosystems. Abiotic and biotic elements ‘pass’ through these reef passages, supporting critical ecological processes (e.g. fish spawning). Reef passages provide multiple social and ecological benefits for islands and their peoples, but are so far neither characterized nor recognized for their multifaceted significance. This study investigated 113 reef passages across nine Pacific islands (Fiji, New Caledonia, Vanuatu). GIS-based visual interpretations of satellite imagery were used to develop criteria to define three distinct types, mainly based on distance to coastline and presence/absence of an enclosed water body. The discussion identifies ways to refine and augment this preliminary typology as part of a research agenda for reef passages. With these next steps, this typology will be extendable to other regions to better document reef passages and their various roles, supporting biodiversity conservation and sustainable fisheries management

Groundwater discharge impacts marine isotope budgets of Li, Mg, Ca, Sr, and Ba

© The Author(s), 2021. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Mayfield, K. K., Eisenhauer, A., Santiago Ramos, D. P., Higgins, J. A., Horner, T. J., Auro, M., Magna, T., Moosdorf, N., Charette, M. A., Gonneea, M. E., Brady, C. E., Komar, N., Peucker-Ehrenbrink, B., & Paytan, A. Groundwater discharge impacts marine isotope budgets of Li, Mg, Ca, Sr, and Ba. Nature Communications, 12(1), (2021): 148-020-20248-3, doi:10.1038/s41467-020-20248-3.Groundwater-derived solute fluxes to the ocean have long been assumed static and subordinate to riverine fluxes, if not neglected entirely, in marine isotope budgets. Here we present concentration and isotope data for Li, Mg, Ca, Sr, and Ba in coastal groundwaters to constrain the importance of groundwater discharge in mediating the magnitude and isotopic composition of terrestrially derived solute fluxes to the ocean. Data were extrapolated globally using three independent volumetric estimates of groundwater discharge to coastal waters, from which we estimate that groundwater-derived solute fluxes represent, at a minimum, 5% of riverine fluxes for Li, Mg, Ca, Sr, and Ba. The isotopic compositions of the groundwater-derived Mg, Ca, and Sr fluxes are distinct from global riverine averages, while Li and Ba fluxes are isotopically indistinguishable from rivers. These differences reflect a strong dependence on coastal lithology that should be considered a priority for parameterization in Earth-system models.We thank A. Beck, H. Dulai, I. Santos, C. Benitez-Nelson, W. Moore, A. Martin, and H. Windom for sample access. We also thank A. Kolevica, A. Heuser, H. Pryer, J. Middleton, R. Franks, F. Lon, N. Slater, and O. Šebek for their laboratory and analytical assistance. This material is based upon research supported by the National Science Foundation Graduate Research Fellowship Program and an internship provided through the U.S. Geological Survey Graduate Research Internship Program (GRIP). This research was also supported by grants from: the German Academic Exchange Service (DAAD), Northern California chapter of the Achievement Rewards for College Scientists Foundation, International Association of GeoChemistry, Geological Society of America, Northern California Geological Society, Myers Trust, Friends of Long Marine Lab, and UC MEXUS (to K.K.M.). We acknowledge funding from EU-ITN Horizon project 643084 (to A.E. and T.M.) and NSF grant Award Number 1259440 (to A.P.). We also acknowledge funding from NSF grant award number OCE-1736949 (to T.J.H.). Any use of trade, firm or product names is for descriptive purposes only and does not imply endorsement by the U.S. Government