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The isotopic composition of barium (δ¹³⁸Ba) has emerged as a powerful tracer of deep-ocean circulation, water mass provenance, and the oceanic Ba cycle. Although the δ¹³⁸Ba of water masses is primarily controlled by the balance between pelagic barite precipitation and Ba resupply from ocean circulation, questions remain regarding the isotopic offset associated with pelagic barite formation and how the resultant Ba isotope compositions are transmitted through the water column to marine sediments. To address these questions, we conducted a time series study of dissolved, particulate, and sedimentary Ba chemistry in the Gulf of Aqaba (GOA), in the northern Red Sea, from January 2015 to April 2016. These data span significant seasonal changes in hydrography, primary productivity, and aerosol deposition, revealing three principal findings. First, the dissolved Ba chemistry of the GOA is vertically uniform across the time series, largely reflecting water mass advection from the Red Sea, with mean dissolved Ba concentrations of 47.9 ± 4.7 nmol kg⁻¹and mean δ¹³⁸Ba = +0.55‰ ± 0.07‰ (±2 SD,n= 18). Second, despite significant variations in particulate matter composition and flux, the δ¹³⁸Ba of sinking particulate Ba maintained a consistent isotope composition across different depths and over time at +0.09‰ ± 0.06‰ (n= 26). Consequently, these data imply a consistent Ba isotope offset of −0.46‰ ± 0.10‰ (±2 SD) between sinking particulates and seawater. This offset is similar to those determined in previous studies and indicates that it applies to particulates formed across diverse environmental conditions. Third, barite-containing sediment samples deposited in the GOA exhibit δ¹³⁸Ba = +0.34‰ ± 0.03‰, which is offset by approximately +0.2‰ relative to sinking particles. While the specific mechanism driving this offset remains unresolved, our results highlight the importance of performing site-specific proxy validations and exercising careful site selection when applying novel paleoceanographic proxies. 

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. 

Solutions to waste management in informal settlements in South Africa South Africa has retained some of the unjust laws following the Apartheid system, but rapid urbanisation has resulted in burgeoning informal settlements, often situated on the periphery of major cities and towns, where clean water is often inaccessible and waste management is limited. Clean water is the main catalyst for the projects conducted by the Waste FEW ULL team, Kevin Winter, Adina Paytan, Sue Charlesworth, and Jana Fried. The motivation for developing the ULL arose out of concern about the contaminated water and its impact on human health and the environment. Rising demand for land and houses has made people struggle to overcome existing income and wealth disparities, with high levels of unemployment and poverty remaining, leaving many only able to live in so-called informal settlements. The concept of Urban Living Labs (ULLs) has advanced from centres that were largely seen as test beds of innovation to become sites of learning and places where stakeholders can co-create solutions to address critical issues and challenges. 

Zero food waste city 2049: Identifying barriers to transition pathways Daniel Black, Ian Roderick, Adina Paytan, Sue Charlesworth and Joy Carey from an Urban Living Lab in the UK have tested newly integrated systems approaches and valuation methods to understand how to reduce the city's food waste. Food waste costs the UK billions of pounds each year and much of it is avoidable. The challenge for the WASTE FEW ULL research project was to produce and test methods for identifying inefficiencies in the food-energy-water (FEW) nexus in urban settings. Looking in particular at Bristol city, which throws away 48,000 tonnes of food waste each year, the team looked into how they could transform Bristol into a sustainable food city. Stakeholder concerns arose including the nutrient overload problem in water systems and the economic recovery of phosphate; the large amount of food waste from the city linked to food security issues; the energy and carbon footprint of the digestate produced from the anaerobic digestors; the economic challenges of reducing food waste; the plastic contamination of waste streams; sewage system blockages; and the difficulties of recycling sewage and wastewater. This research looks at the challenge of phosphorous recapture from sewage through extensive discussions agreed to shift the project focus to residential food waste reduction and processing (and the associated plastic contamination). The team eventually began looking at the critical concept of resilience and economic efficiency, working to substantially reduce inefficiencies in a city-regions FEW nexuses. 

Achieving societal impact, as opposed to academic impact, is a growing area of focus for the research community globally. Central to this changing mission is the focus on multiple interconnected complex systems and the need for research that is not just interdisciplinary, but also transdisciplinary and grounded in stakeholder co-production. This document compares multiple approaches to impact planning and evaluation across four newly formed urban living labs in Sao Paolo (Brazil), Western Cape (South Africa), Bristol (UK) and Rotterdam (Netherlands), each of which sought to address societal issues linked to the food-energy-water nexus. A comparison matrix and a disaggregated impact table are derived from a comprehensive review of key definitions. These new tools were completed by each ULL alongside a post hoc pathway to impact statements. Comparisons are presented and discussed, the strengths and weaknesses of this approach are considered and opportunities for improvement in societal impact planning and evaluation are provided. Our main findings include the importance of establishing clear shared definitions while accepting plural understandings, the need to acknowledge resource as a critical factor in impact delivery and the headline need for far greater focus in this area from both funders and research groups. 

Sustainable urban systems and just FEW nexus transitions Water, food, and energy systems are providing fundamental services for human wellbeing. However, the current management of these systems is often wasteful, creating inefficiencies that need to be urgently addressed to reduce the over-consumption of our limited natural resources. Here, Jana Fried, Adina Paytan and Waste FEW ULL project participants look at lessons from the Waste FEW ULL project for reducing waste and increasing efficiency in the FEW nexus. 

The triple oxygen isotope composition (Δ’ 17 O) of sulfate minerals is widely used to constrain ancient atmospheric p O 2 / p CO 2 and rates of gross primary production. The utility of this tool is based on a model that sulfate oxygen carries an isotope fingerprint of tropospheric O 2 incorporated through oxidative weathering of reduced sulfur minerals, particularly pyrite. Work to date has targeted Proterozoic environments (2.5 billion to 0.542 billion years ago) where large isotope anomalies persist; younger timescale records, which would ground ancient environmental interpretation in what we know from modern Earth, are lacking. Here we present a high-resolution record of the δ 18 O and Δ’ 17 O in marine sulfate for the last 130 million years of Earth history. This record carries a Δ’ 17 O close to 0o, suggesting that the marine sulfate reservoir is under strict control by biogeochemical cycling (namely, microbial sulfate reduction), as these reactions follow mass-dependent fractionation. We identify no discernible contribution from atmospheric oxygen on this timescale. We interpret a steady fractional contribution of microbial sulfur cycling (terrestrial and marine) over the last 100 million years, even as global weathering rates are thought to vary considerably. 

Our understanding of phosphorus (P) dynamics in the deep subseafloor environment remains limited. Here we investigate potential microbial P uptake mechanisms in oligotrophic marine sediments beneath the North Atlantic Gyre and their effects on the relative distribution of organic P compounds as a function of burial depth and changing redox conditions. We use metagenomic analyses to determine the presence of microbial functional genes pertaining to P uptake and metabolism, and solution 31 P nuclear magnetic resonance spectroscopy ( 31 P NMR) to characterize and quantify P substrates. Phosphorus compounds or compound classes identified with 31 P NMR include inorganic P compounds (orthophosphate, pyrophosphate, polyphosphate), phosphonates, orthophosphate monoesters (including inositol hexakisphosphate stereoisomers) and orthophosphate diesters (including DNA and phospholipid degradation products). Some of the genes identified include genes related to phosphate transport, phosphonate and polyphosphate metabolism, as well as phosphite uptake. Our findings suggest that the deep sedimentary biosphere may have adapted to take advantage of a wide array of P substrates and could play a role in the gradual breakdown of inositol and sugar phosphates, as well as reduced P compounds and polyphosphates.