| 1. |
- Balestra, Barbara, et al.
(författare)
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Bottom-water oxygenation and environmental change in Santa Monica Basin, Southern California during the last 23kyr
- 2018
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Ingår i: Palaeogeography, Palaeoclimatology, Palaeoecology. - : Elsevier BV. - 0031-0182. ; 490, s. 17-37
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Tidskriftsartikel (refereegranskat)abstract
- The Southern California Borderland is a region that experiences strong natural variations in bottom water oxygen and pH. We use marine sediments from Santa Monica Basin to reconstruct environmental conditions in the basin's bottom water from the Last Glacial Maximum (LGM) to present. We then compare the records to the adjacent Santa Barbara Basin and Santa Lucia Slope. High-resolution records of benthic foraminiferal oxygen and carbon isotopes (δ18O and δ13C), benthic foraminiferal assemblages, and bulk sedimentary organic matter geochemistry records exhibit major changes associated with late Quaternary millennial-scale global climate oscillations. Our data show the dominance of low-oxygen benthic foraminiferal assemblages during warm intervals, and assemblages representing higher dissolved oxygen during cooler intervals, as also seen in Santa Barbara Basin and Santa Lucia Slope. However, our record shows a stronger and longer-lasting oxygen minimum zone (OMZ) between the mid Younger Dryas (YD) and the Early Holocene than at neighboring sites, indicated by dominance of Bolivina tumida (characteristic of major hypoxia) in the assemblage. The middle to late Holocene (from ∼9 to 0kyr) had weaker hypoxia than the early Holocene, with assemblages mainly composed of Bolivina argentea and Uvigerina peregrina. Santa Monica Basin remained slightly hypoxic throughout the past 23kyr, however, differences in the degree of hypoxia from Santa Barbara Basin and Santa Lucia Slope (especially from the B-A to the Early Holocene) are seen. The Santa Monica Basin bottom water is affected by regional processes, such as changes in the source of intermediate water and/or changing ventilation (oxygenation) of the intermediate water source. This is due to the greater depth and the more southern geographic position of the Basin, which reduces exposure to the oxygenated North Pacific Intermediate Water current. Additional local processes also affect the basin, such as the effects of sediment influx from submarine canyons. This analysis utilizing parallel geochemical and micropaleontological records brings new insights into bottom water and climate conditions in Santa Monica Basin, indicating regional similarities and differences from adjacent basins, and provides insight into the causes for changes in bottom water oxygenation.
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| 2. |
- Glaser, Marion, et al.
(författare)
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Analysis across case-based global sustainability projects : an emerging challenge for ocean conflict research in the Anthropocene
- 2023
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Ingår i: Maritime Studies. - : Springer Nature. - 1872-7859 .- 2212-9790. ; 22:4
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Tidskriftsartikel (refereegranskat)abstract
- A growing number of global ocean conflict studies over the last decade have set out to advance sustainability in the Anthropocene. Many of these research projects use multiple case studies to extract lessons for wider contexts. The methods used by these studies, and the extent to which their results have validity beyond the individual case study, often remain unclear. This paper explores the challenges in performing cross-case analysis within what we denote as case-based globally focussed sustainability projects (CB-GSPs) and indicates solutions by combining information from semi-structured interviews with leading scientists from eight CB-GSPs. We identify six distinct challenges that are common across these studies with regard to generating actionable knowledge through cross-case analysis. Based on these findings, we propose a set of best practice recommendations for scientists, project partners, and funders to co-produce actionable knowledge for global projects on ocean conflict.
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| 3. |
- Knee, Karen, et al.
(författare)
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Submarine Groundwater Discharge: A Source of Nutrients, Metals, and Pollutants to the Coastal Ocean
- 2024
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Ingår i: Treatise on Estuarine and Coastal Science, 2nd Edition. - : Elsevier. ; , s. 123-163
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Bokkapitel (refereegranskat)abstract
- This chapter reviews the current knowledge on submarine groundwater discharge (SGD) and the associated fluxes of nutrients, trace metals, microbes, pharmaceuticals, and other terrestrial constituents to coastal waters. We review methods of estimating SGD, present flux estimates from different locations worldwide, and discuss how various hydrogeologic features such as topography, aquifer substrate, climate, waves, and tides affect SGD. We discuss the range of material concentrations and fluxes, their relationship to land use, and the chemical changes that nutrients and metals undergo during their seaward journey through the aquifer. Climate change is likely to affect both the quantity and the quality of SGD, and we review these effects. The chapter concludes with a discussion of active areas of SGD research, including expanding the geographic scope of SGD studies; characterizing and reducing the uncertainty associated with SGD measurements; understanding the behavior of nutrients, metals, and other pollutants in the subterranean estuary; and modeling SGD on a global scale.
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| 4. |
- Petersen, Karen Lykkebo, et al.
(författare)
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Biological and Physical Effects of Brine Discharge from the Carlsbad Desalination Plant and Implications for Future Desalination Plant Constructions
- 2019
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Ingår i: Water. - : MDPI AG. - 2073-4441. ; 11:2
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Tidskriftsartikel (refereegranskat)abstract
- Seawater reverse osmosis (SWRO) desalination is increasingly used as a technology for addressing shortages of freshwater supply and desalination plants are in operation or being planned world-wide and specifically in California, USA. However, the effects of continuous discharge of high-salinity brine into coastal environments are ill-constrained and in California are an issue of public debate. We collected in situ measurements of water chemistry and biological indicators in coastal waters (up to 2 km from shore) before and after the newly constructed Carlsbad Desalination Plant (Carlsbad, CA, USA) began operations. A bottom water salinity anomaly indicates that the spatial footprint of the brine discharge plume extended about 600 m offshore with salinity up to 2.7 units above ambient (33.2). This exceeds the maximum salinity permitted for this location based on the California Ocean Plan (2015 Amendment to Water Quality Control Plan). However, no significant changes in the assessed biological indicators (benthic macrofauna, BOPA-index, brittle-star survival and growth) were observed at the discharge site. A model of mean ocean wave potential was used as an indicator of coastal mixing at Carlsbad Beach and at other locations in southern and central CA where desalination facilities are proposed. Our results indicated that to minimize environmental impacts discharge should target waters where a long history of anthropogenic activity has already compromised the natural setting. To ensure adequate mixing of the discharge brine desalination plants should be constructed at high-energy sites with sandy substrates, and discharge through diffusor systems.
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| 5. |
- Silva-Tamayo, Juan Carlos, et al.
(författare)
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Global perturbation of the marine calcium cycle during the Permian-Triassic transition
- 2018
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Ingår i: Geological Society of America Bulletin. - 0016-7606. ; 130:7-8, s. 1323-1338
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Tidskriftsartikel (refereegranskat)abstract
- A negative shift in the calcium isotopiccomposition of marine carbonate rocksspanning the end-Permian extinction horizonin South China has been used to arguefor an ocean acidification event coincidentwith mass extinction. This interpretationhas proven controversial, both because theexcursion has not been demonstrated acrossmultiple, widely separated localities, and becausemodeling results of coupled carbon andcalcium isotope records illustrate that calciumcycle imbalances alone cannot accountfor the full magnitude of the isotope excursion.Here, we further test potential controlson the Permian-Triassic calcium isotoperecord by measuring calcium isotope ratiosfrom shallow-marine carbonate successionsspanning the Permian-Triassic boundary inTurkey, Italy, and Oman. All measured sectionsdisplay negative shifts in δ44/40Ca of upto 0.6‰. Consistency in the direction, magnitude,and timing of the calcium isotope excursionacross these widely separated localitiesimplies a primary and global δ44/40Ca signature.Based on the results of a coupled boxmodel of the geological carbon and calciumcycles, we interpret the excursion to reflect aseries of consequences arising from volcanicCO2 release, including a temporary decreasein seawater δ44/40Ca due to short-lived oceanacidification and a more protracted increasein calcium isotope fractionation associatedwith a shift toward more primary aragonitein the sediment and, potentially, subsequentlyelevated carbonate saturation statescaused by the persistence of elevated CO2delivery from volcanism. Locally, changingbalances between aragonite and calcite productionare sufficient to account for the calciumisotope excursions, but this effect alonedoes not explain the globally observed negativeexcursion in the δ13C values of carbonatesediments and organic matter as well. Onlya carbon release event and related geochemicalconsequences are consistent both withcalcium and carbon isotope data. The carbonrelease scenario can also account for oxygenisotope evidence for dramatic and protractedglobal warming as well as paleontologicalevidencefor the preferential extinction ofmarine animals most susceptible to acidification,warming, and anoxia.
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| 6. |
- Wilson, Stephanie J., et al.
(författare)
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Global subterranean estuaries modify groundwater nutrient loading to the ocean
- 2024
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Ingår i: Limnology And Oceanography Letters. - 2378-2242.
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Tidskriftsartikel (refereegranskat)abstract
- Terrestrial groundwater travels through subterranean estuaries before reaching the sea. Groundwater-derived nutrients drive coastal water quality, primary production, and eutrophication. We determined how dissolved inorganic nitrogen (DIN), dissolved inorganic phosphorus (DIP), and dissolved organic nitrogen (DON) are transformed within subterranean estuaries and estimated submarine groundwater discharge (SGD) nutrient loads compiling > 10,000 groundwater samples from 216 sites worldwide. Nutrients exhibited complex, nonconservative behavior in subterranean estuaries. Fresh groundwater DIN and DIP are usually produced, and DON is consumed during transport. Median total SGD (saline and fresh) fluxes globally were 5.4, 2.6, and 0.18 Tmol yr−1 for DIN, DON, and DIP, respectively. Despite large natural variability, total SGD fluxes likely exceed global riverine nutrient export. Fresh SGD is a small source of new nutrients, but saline SGD is an important source of mostly recycled nutrients. Nutrients exported via SGD via subterranean estuaries are critical to coastal biogeochemistry and a significant nutrient source to the oceans.
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