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1.
  • 2021
  • swepub:Mat__t
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2.
  • 2021
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3.
  • Glasbey, JC, et al. (author)
  • 2021
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6.
  • 2019
  • Journal article (peer-reviewed)
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7.
  • Lozano, Rafael, et al. (author)
  • Measuring progress from 1990 to 2017 and projecting attainment to 2030 of the health-related Sustainable Development Goals for 195 countries and territories: a systematic analysis for the Global Burden of Disease Study 2017
  • 2018
  • In: The Lancet. - : Elsevier. - 1474-547X .- 0140-6736. ; 392:10159, s. 2091-2138
  • Journal article (peer-reviewed)abstract
    • Background: Efforts to establish the 2015 baseline and monitor early implementation of the UN Sustainable Development Goals (SDGs) highlight both great potential for and threats to improving health by 2030. To fully deliver on the SDG aim of “leaving no one behind”, it is increasingly important to examine the health-related SDGs beyond national-level estimates. As part of the Global Burden of Diseases, Injuries, and Risk Factors Study 2017 (GBD 2017), we measured progress on 41 of 52 health-related SDG indicators and estimated the health-related SDG index for 195 countries and territories for the period 1990–2017, projected indicators to 2030, and analysed global attainment. Methods: We measured progress on 41 health-related SDG indicators from 1990 to 2017, an increase of four indicators since GBD 2016 (new indicators were health worker density, sexual violence by non-intimate partners, population census status, and prevalence of physical and sexual violence [reported separately]). We also improved the measurement of several previously reported indicators. We constructed national-level estimates and, for a subset of health-related SDGs, examined indicator-level differences by sex and Socio-demographic Index (SDI) quintile. We also did subnational assessments of performance for selected countries. To construct the health-related SDG index, we transformed the value for each indicator on a scale of 0–100, with 0 as the 2·5th percentile and 100 as the 97·5th percentile of 1000 draws calculated from 1990 to 2030, and took the geometric mean of the scaled indicators by target. To generate projections through 2030, we used a forecasting framework that drew estimates from the broader GBD study and used weighted averages of indicator-specific and country-specific annualised rates of change from 1990 to 2017 to inform future estimates. We assessed attainment of indicators with defined targets in two ways: first, using mean values projected for 2030, and then using the probability of attainment in 2030 calculated from 1000 draws. We also did a global attainment analysis of the feasibility of attaining SDG targets on the basis of past trends. Using 2015 global averages of indicators with defined SDG targets, we calculated the global annualised rates of change required from 2015 to 2030 to meet these targets, and then identified in what percentiles the required global annualised rates of change fell in the distribution of country-level rates of change from 1990 to 2015. We took the mean of these global percentile values across indicators and applied the past rate of change at this mean global percentile to all health-related SDG indicators, irrespective of target definition, to estimate the equivalent 2030 global average value and percentage change from 2015 to 2030 for each indicator. Findings: The global median health-related SDG index in 2017 was 59·4 (IQR 35·4–67·3), ranging from a low of 11·6 (95% uncertainty interval 9·6–14·0) to a high of 84·9 (83·1–86·7). SDG index values in countries assessed at the subnational level varied substantially, particularly in China and India, although scores in Japan and the UK were more homogeneous. Indicators also varied by SDI quintile and sex, with males having worse outcomes than females for non-communicable disease (NCD) mortality, alcohol use, and smoking, among others. Most countries were projected to have a higher health-related SDG index in 2030 than in 2017, while country-level probabilities of attainment by 2030 varied widely by indicator. Under-5 mortality, neonatal mortality, maternal mortality ratio, and malaria indicators had the most countries with at least 95% probability of target attainment. Other indicators, including NCD mortality and suicide mortality, had no countries projected to meet corresponding SDG targets on the basis of projected mean values for 2030 but showed some probability of attainment by 2030. For some indicators, including child malnutrition, several infectious diseases, and most violence measures, the annualised rates of change required to meet SDG targets far exceeded the pace of progress achieved by any country in the recent past. We found that applying the mean global annualised rate of change to indicators without defined targets would equate to about 19% and 22% reductions in global smoking and alcohol consumption, respectively; a 47% decline in adolescent birth rates; and a more than 85% increase in health worker density per 1000 population by 2030. Interpretation: The GBD study offers a unique, robust platform for monitoring the health-related SDGs across demographic and geographic dimensions. Our findings underscore the importance of increased collection and analysis of disaggregated data and highlight where more deliberate design or targeting of interventions could accelerate progress in attaining the SDGs. Current projections show that many health-related SDG indicators, NCDs, NCD-related risks, and violence-related indicators will require a concerted shift away from what might have driven past gains—curative interventions in the case of NCDs—towards multisectoral, prevention-oriented policy action and investments to achieve SDG aims. Notably, several targets, if they are to be met by 2030, demand a pace of progress that no country has achieved in the recent past. The future is fundamentally uncertain, and no model can fully predict what breakthroughs or events might alter the course of the SDGs. What is clear is that our actions—or inaction—today will ultimately dictate how close the world, collectively, can get to leaving no one behind by 2030.
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8.
  • Kassebaum, Nicholas J., et al. (author)
  • Global, regional, and national disability-adjusted life-years (DALYs) for 315 diseases and injuries and healthy life expectancy (HALE), 1990-2015 : a systematic analysis for the Global Burden of Disease Study 2015
  • 2016
  • In: The Lancet. - 0140-6736 .- 1474-547X. ; 388:10053, s. 1603-1658
  • Journal article (peer-reviewed)abstract
    • Background Healthy life expectancy (HALE) and disability-adjusted life-years (DALYs) provide summary measures of health across geographies and time that can inform assessments of epidemiological patterns and health system performance, help to prioritise investments in research and development, and monitor progress toward the Sustainable Development Goals (SDGs). We aimed to provide updated HALE and DALYs for geographies worldwide and evaluate how disease burden changes with development. Methods We used results from the Global Burden of Diseases, Injuries, and Risk Factors Study 2015 (GBD 2015) for all-cause mortality, cause-specific mortality, and non-fatal disease burden to derive HALE and DALYs by sex for 195 countries and territories from 1990 to 2015. We calculated DALYs by summing years of life lost (YLLs) and years of life lived with disability (YLDs) for each geography, age group, sex, and year. We estimated HALE using the Sullivan method, which draws from age-specific death rates and YLDs per capita. We then assessed how observed levels of DALYs and HALE differed from expected trends calculated with the Socio-demographic Index (SDI), a composite indicator constructed from measures of income per capita, average years of schooling, and total fertility rate. Findings Total global DALYs remained largely unchanged from 1990 to 2015, with decreases in communicable, neonatal, maternal, and nutritional (Group 1) disease DALYs off set by increased DALYs due to non-communicable diseases (NCDs). Much of this epidemiological transition was caused by changes in population growth and ageing, but it was accelerated by widespread improvements in SDI that also correlated strongly with the increasing importance of NCDs. Both total DALYs and age-standardised DALY rates due to most Group 1 causes significantly decreased by 2015, and although total burden climbed for the majority of NCDs, age-standardised DALY rates due to NCDs declined. Nonetheless, age-standardised DALY rates due to several high-burden NCDs (including osteoarthritis, drug use disorders, depression, diabetes, congenital birth defects, and skin, oral, and sense organ diseases) either increased or remained unchanged, leading to increases in their relative ranking in many geographies. From 2005 to 2015, HALE at birth increased by an average of 2.9 years (95% uncertainty interval 2.9-3.0) for men and 3.5 years (3.4-3.7) for women, while HALE at age 65 years improved by 0.85 years (0.78-0.92) and 1.2 years (1.1-1.3), respectively. Rising SDI was associated with consistently higher HALE and a somewhat smaller proportion of life spent with functional health loss; however, rising SDI was related to increases in total disability. Many countries and territories in central America and eastern sub-Saharan Africa had increasingly lower rates of disease burden than expected given their SDI. At the same time, a subset of geographies recorded a growing gap between observed and expected levels of DALYs, a trend driven mainly by rising burden due to war, interpersonal violence, and various NCDs. Interpretation Health is improving globally, but this means more populations are spending more time with functional health loss, an absolute expansion of morbidity. The proportion of life spent in ill health decreases somewhat with increasing SDI, a relative compression of morbidity, which supports continued efforts to elevate personal income, improve education, and limit fertility. Our analysis of DALYs and HALE and their relationship to SDI represents a robust framework on which to benchmark geography-specific health performance and SDG progress. Country-specific drivers of disease burden, particularly for causes with higher-than-expected DALYs, should inform financial and research investments, prevention efforts, health policies, and health system improvement initiatives for all countries along the development continuum.
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9.
  • Kattge, Jens, et al. (author)
  • TRY plant trait database - enhanced coverage and open access
  • 2020
  • In: Global Change Biology. - : Wiley-Blackwell. - 1354-1013 .- 1365-2486. ; 26:1, s. 119-188
  • Journal article (peer-reviewed)abstract
    • Plant traits-the morphological, anatomical, physiological, biochemical and phenological characteristics of plants-determine how plants respond to environmental factors, affect other trophic levels, and influence ecosystem properties and their benefits and detriments to people. Plant trait data thus represent the basis for a vast area of research spanning from evolutionary biology, community and functional ecology, to biodiversity conservation, ecosystem and landscape management, restoration, biogeography and earth system modelling. Since its foundation in 2007, the TRY database of plant traits has grown continuously. It now provides unprecedented data coverage under an open access data policy and is the main plant trait database used by the research community worldwide. Increasingly, the TRY database also supports new frontiers of trait-based plant research, including the identification of data gaps and the subsequent mobilization or measurement of new data. To support this development, in this article we evaluate the extent of the trait data compiled in TRY and analyse emerging patterns of data coverage and representativeness. Best species coverage is achieved for categorical traits-almost complete coverage for 'plant growth form'. However, most traits relevant for ecology and vegetation modelling are characterized by continuous intraspecific variation and trait-environmental relationships. These traits have to be measured on individual plants in their respective environment. Despite unprecedented data coverage, we observe a humbling lack of completeness and representativeness of these continuous traits in many aspects. We, therefore, conclude that reducing data gaps and biases in the TRY database remains a key challenge and requires a coordinated approach to data mobilization and trait measurements. This can only be achieved in collaboration with other initiatives.
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10.
  • Murray, Christopher J. L., et al. (author)
  • Population and fertility by age and sex for 195 countries and territories, 1950–2017: a systematic analysis for the Global Burden of Disease Study 2017
  • 2018
  • In: The Lancet. - 1474-547X .- 0140-6736. ; 392:10159, s. 1995-2051
  • Journal article (peer-reviewed)abstract
    • Background: Population estimates underpin demographic and epidemiological research and are used to track progress on numerous international indicators of health and development. To date, internationally available estimates of population and fertility, although useful, have not been produced with transparent and replicable methods and do not use standardised estimates of mortality. We present single-calendar year and single-year of age estimates of fertility and population by sex with standardised and replicable methods. Methods: We estimated population in 195 locations by single year of age and single calendar year from 1950 to 2017 with standardised and replicable methods. We based the estimates on the demographic balancing equation, with inputs of fertility, mortality, population, and migration data. Fertility data came from 7817 location-years of vital registration data, 429 surveys reporting complete birth histories, and 977 surveys and censuses reporting summary birth histories. We estimated age-specific fertility rates (ASFRs; the annual number of livebirths to women of a specified age group per 1000 women in that age group) by use of spatiotemporal Gaussian process regression and used the ASFRs to estimate total fertility rates (TFRs; the average number of children a woman would bear if she survived through the end of the reproductive age span [age 10–54 years] and experienced at each age a particular set of ASFRs observed in the year of interest). Because of sparse data, fertility at ages 10–14 years and 50–54 years was estimated from data on fertility in women aged 15–19 years and 45–49 years, through use of linear regression. Age-specific mortality data came from the Global Burden of Diseases, Injuries, and Risk Factors Study (GBD) 2017 estimates. Data on population came from 1257 censuses and 761 population registry location-years and were adjusted for underenumeration and age misreporting with standard demographic methods. Migration was estimated with the GBD Bayesian demographic balancing model, after incorporating information about refugee migration into the model prior. Final population estimates used the cohort-component method of population projection, with inputs of fertility, mortality, and migration data. Population uncertainty was estimated by use of out-of-sample predictive validity testing. With these data, we estimated the trends in population by age and sex and in fertility by age between 1950 and 2017 in 195 countries and territories. Findings: From 1950 to 2017, TFRs decreased by 49·4% (95% uncertainty interval [UI] 46·4–52·0). The TFR decreased from 4·7 livebirths (4·5–4·9) to 2·4 livebirths (2·2–2·5), and the ASFR of mothers aged 10–19 years decreased from 37 livebirths (34–40) to 22 livebirths (19–24) per 1000 women. Despite reductions in the TFR, the global population has been increasing by an average of 83·8 million people per year since 1985. The global population increased by 197·2% (193·3–200·8) since 1950, from 2·6 billion (2·5–2·6) to 7·6 billion (7·4–7·9) people in 2017; much of this increase was in the proportion of the global population in south Asia and sub-Saharan Africa. The global annual rate of population growth increased between 1950 and 1964, when it peaked at 2·0%; this rate then remained nearly constant until 1970 and then decreased to 1·1% in 2017. Population growth rates in the southeast Asia, east Asia, and Oceania GBD super-region decreased from 2·5% in 1963 to 0·7% in 2017, whereas in sub-Saharan Africa, population growth rates were almost at the highest reported levels ever in 2017, when they were at 2·7%. The global average age increased from 26·6 years in 1950 to 32·1 years in 2017, and the proportion of the population that is of working age (age 15–64 years) increased from 59·9% to 65·3%. At the national level, the TFR decreased in all countries and territories between 1950 and 2017; in 2017, TFRs ranged from a low of 1·0 livebirths (95% UI 0·9–1·2) in Cyprus to a high of 7·1 livebirths (6·8–7·4) in Niger. The TFR under age 25 years (TFU25; number of livebirths expected by age 25 years for a hypothetical woman who survived the age group and was exposed to current ASFRs) in 2017 ranged from 0·08 livebirths (0·07–0·09) in South Korea to 2·4 livebirths (2·2–2·6) in Niger, and the TFR over age 30 years (TFO30; number of livebirths expected for a hypothetical woman ageing from 30 to 54 years who survived the age group and was exposed to current ASFRs) ranged from a low of 0·3 livebirths (0·3–0·4) in Puerto Rico to a high of 3·1 livebirths (3·0–3·2) in Niger. TFO30 was higher than TFU25 in 145 countries and territories in 2017. 33 countries had a negative population growth rate from 2010 to 2017, most of which were located in central, eastern, and western Europe, whereas population growth rates of more than 2·0% were seen in 33 of 46 countries in sub-Saharan Africa. In 2017, less than 65% of the national population was of working age in 12 of 34 high-income countries, and less than 50% of the national population was of working age in Mali, Chad, and Niger. Interpretation: Population trends create demographic dividends and headwinds (ie, economic benefits and detriments) that affect national economies and determine national planning needs. Although TFRs are decreasing, the global population continues to grow as mortality declines, with diverse patterns at the national level and across age groups. To our knowledge, this is the first study to provide transparent and replicable estimates of population and fertility, which can be used to inform decision making and to monitor progress. Funding: Bill & Melinda Gates Foundation.
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11.
  • Jones, Benedict C, et al. (author)
  • To which world regions does the valence-dominance model of social perception apply?
  • 2021
  • In: Nature Human Behaviour. - : Springer Science and Business Media LLC. - 2397-3374. ; 5:1, s. 159-169
  • Journal article (peer-reviewed)abstract
    • Over the past 10 years, Oosterhof and Todorov's valence-dominance model has emerged as the most prominent account of how people evaluate faces on social dimensions. In this model, two dimensions (valence and dominance) underpin social judgements of faces. Because this model has primarily been developed and tested in Western regions, it is unclear whether these findings apply to other regions. We addressed this question by replicating Oosterhof and Todorov's methodology across 11 world regions, 41 countries and 11,570 participants. When we used Oosterhof and Todorov's original analysis strategy, the valence-dominance model generalized across regions. When we used an alternative methodology to allow for correlated dimensions, we observed much less generalization. Collectively, these results suggest that, while the valence-dominance model generalizes very well across regions when dimensions are forced to be orthogonal, regional differences are revealed when we use different extraction methods and correlate and rotate the dimension reduction solution. PROTOCOL REGISTRATION: The stage 1 protocol for this Registered Report was accepted in principle on 5 November 2018. The protocol, as accepted by the journal, can be found at https://doi.org/10.6084/m9.figshare.7611443.v1 .
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12.
  • Conrad, S. R., et al. (author)
  • Land use change increases contaminant sequestration in blue carbon sediments
  • 2023
  • In: Science of the Total Environment. - : Elsevier BV. - 0048-9697. ; 873
  • Journal article (peer-reviewed)abstract
    • Coastal blue carbon habitats perform many important environmental functions, including long-term carbon and an-thropogenic contaminant storage. Here, we analysed twenty-five 210Pb-dated mangrove, saltmarsh, and seagrass sed-iment cores from six estuaries across a land-use gradient to determine metal, metalloid, and phosphorous sedimentary fluxes. Cadmium, arsenic, iron, and manganese had linear to exponential positive correlations between concentrations, sediment flux, geoaccumulation index, and catchment development. Increases in anthropogenic development (agricul-tural or urban land uses) from > 30 % of the total catchment area enhanced mean concentrations of arsenic, copper, iron, manganese, and zinc between 1.5 and 4.3-fold. A similar to 30 % anthropogenic land-use was the threshold in which blue carbon sediment quality begins to be detrimentally impacted on an entire estuary scale. Fluxes of phosphorous, cadmium, lead, and aluminium responded similarly, increasing 1.2 to 2.5-fold when anthropogenic land-use increased by at least 5 %. Exponential increases in phosphorus flux to estuary sediments seem to precede eutrophication as ob-served in more developed estuaries. Overall, multiple lines of evidence revealed how catchment development drives blue carbon sediment quality across a regional scale.
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13.
  • Correa, R. E., et al. (author)
  • Submarine groundwater discharge and associated nutrient and carbon inputs into Sydney Harbour (Australia)
  • 2020
  • In: Journal of Hydrology. - : Elsevier BV. - 0022-1694. ; 580
  • Journal article (peer-reviewed)abstract
    • The effects of urbanization and scales on submarine groundwater discharge (SGD) remain poorly understood. Here, we used radium isotopes to quantify SGD-derived fluxes of nitrogen, phosphorus and dissolved organic carbon (DOC) into Sydney Harbour estuary, Australia. Sydney is the most populated city of Oceania, with several localised cases of historical groundwater pollution. We sampled top and bottom waters at the harbour scale (~20 km) and also at four small scale embayments (~2 km). A decreasing gradient in radium isotope concentrations from upstream to downstream was observed. Mass balances constructed with 224Ra, 223Ra, and 226Ra revealed that total SGD ranged from 42 to 121 × 104 m3 d−1 depending on assumptions and isotope. These fluxes were related mostly to saline SGD (recirculated seawater), and are equivalent to >60 times the mean annual freshwater river discharge into Sydney Harbour (0.68 × 104 m3 d−1). The estimated SGD rates (2.2 ± 1.5 cm d−1) were comparable to the global average radium-derived-SGD in other urban estuaries (~3.1 cm d−1). No obvious relationships were observed between SGD and scale in Sydney Harbour. However, higher SGD rates estimated for embayments closer to the ocean indicate that a combination of waves, tides and urbanization control SGD. SGD derived fluxes exceeded maximum riverine nutrient fluxes by a factor of 2 for DOC, 6 for PO4 3−, 40 for NH4 + and 1.3 for NOX. Previous work has suggested that nutrients enter Sydney Harbour primarily through rivers or stormwater following episodic rain events. Our results imply that diffuse saline SGD can also be an important but overlooked source of nutrients, potentially sustaining primary productivity in times of no river flow. © 2019 Elsevier B.V.
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14.
  • Wang, Haidong, et al. (author)
  • Estimates of global, regional, and national incidence, prevalence, and mortality of HIV, 1980-2015 : the Global Burden of Disease Study 2015.
  • 2016
  • In: The lancet. HIV. - : Elsevier. - 2352-3018. ; 3:8, s. e361-e387
  • Journal article (peer-reviewed)abstract
    • BACKGROUND: Timely assessment of the burden of HIV/AIDS is essential for policy setting and programme evaluation. In this report from the Global Burden of Disease Study 2015 (GBD 2015), we provide national estimates of levels and trends of HIV/AIDS incidence, prevalence, coverage of antiretroviral therapy (ART), and mortality for 195 countries and territories from 1980 to 2015.METHODS: For countries without high-quality vital registration data, we estimated prevalence and incidence with data from antenatal care clinics and population-based seroprevalence surveys, and with assumptions by age and sex on initial CD4 distribution at infection, CD4 progression rates (probability of progression from higher to lower CD4 cell-count category), on and off antiretroviral therapy (ART) mortality, and mortality from all other causes. Our estimation strategy links the GBD 2015 assessment of all-cause mortality and estimation of incidence and prevalence so that for each draw from the uncertainty distribution all assumptions used in each step are internally consistent. We estimated incidence, prevalence, and death with GBD versions of the Estimation and Projection Package (EPP) and Spectrum software originally developed by the Joint United Nations Programme on HIV/AIDS (UNAIDS). We used an open-source version of EPP and recoded Spectrum for speed, and used updated assumptions from systematic reviews of the literature and GBD demographic data. For countries with high-quality vital registration data, we developed the cohort incidence bias adjustment model to estimate HIV incidence and prevalence largely from the number of deaths caused by HIV recorded in cause-of-death statistics. We corrected these statistics for garbage coding and HIV misclassification.FINDINGS: Global HIV incidence reached its peak in 1997, at 3·3 million new infections (95% uncertainty interval [UI] 3·1-3·4 million). Annual incidence has stayed relatively constant at about 2·6 million per year (range 2·5-2·8 million) since 2005, after a period of fast decline between 1997 and 2005. The number of people living with HIV/AIDS has been steadily increasing and reached 38·8 million (95% UI 37·6-40·4 million) in 2015. At the same time, HIV/AIDS mortality has been declining at a steady pace, from a peak of 1·8 million deaths (95% UI 1·7-1·9 million) in 2005, to 1·2 million deaths (1·1-1·3 million) in 2015. We recorded substantial heterogeneity in the levels and trends of HIV/AIDS across countries. Although many countries have experienced decreases in HIV/AIDS mortality and in annual new infections, other countries have had slowdowns or increases in rates of change in annual new infections.INTERPRETATION: Scale-up of ART and prevention of mother-to-child transmission has been one of the great successes of global health in the past two decades. However, in the past decade, progress in reducing new infections has been slow, development assistance for health devoted to HIV has stagnated, and resources for health in low-income countries have grown slowly. Achievement of the new ambitious goals for HIV enshrined in Sustainable Development Goal 3 and the 90-90-90 UNAIDS targets will be challenging, and will need continued efforts from governments and international agencies in the next 15 years to end AIDS by 2030.
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15.
  • Beal, Jacob, et al. (author)
  • Robust estimation of bacterial cell count from optical density
  • 2020
  • In: Communications Biology. - : Springer Science and Business Media LLC. - 2399-3642. ; 3:1
  • Journal article (peer-reviewed)abstract
    • Optical density (OD) is widely used to estimate the density of cells in liquid culture, but cannot be compared between instruments without a standardized calibration protocol and is challenging to relate to actual cell count. We address this with an interlaboratory study comparing three simple, low-cost, and highly accessible OD calibration protocols across 244 laboratories, applied to eight strains of constitutive GFP-expressing E. coli. Based on our results, we recommend calibrating OD to estimated cell count using serial dilution of silica microspheres, which produces highly precise calibration (95.5% of residuals <1.2-fold), is easily assessed for quality control, also assesses instrument effective linear range, and can be combined with fluorescence calibration to obtain units of Molecules of Equivalent Fluorescein (MEFL) per cell, allowing direct comparison and data fusion with flow cytometry measurements: in our study, fluorescence per cell measurements showed only a 1.07-fold mean difference between plate reader and flow cytometry data.
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16.
  • Conrad, S. R., et al. (author)
  • Cryptic night-time trace metal and metalloid contamination in an intensively cultivated coastal catchment
  • 2021
  • In: Environmental Pollution. - : Elsevier BV. - 0269-7491. ; 276
  • Journal article (peer-reviewed)abstract
    • Detailed, high resolution time-series observations were performed to investigate sources, diel cycling, natural attenuation, and loadings of dissolved trace metals/metalloids in a subtropical headwater stream draining intensive horticulture in Australia. A transect of similar to 3 km away from the source (farms) showed >75% reduction in concentration and loads of most trace elements. Mercury and arsenic had elevated loads downstream relative to other elements. Hourly time-series sampling revealed elevated creek discharge at night, accompanied by elevated nickel, selenium, copper, and mercury loads. Inputs from groundwater or treated sewage used for irrigation within the catchment are likely sources. Groundwater bore and treated sewage samples were highly contaminated with either zinc, copper, or mercury. Comparisons of daily and hourly samples indicated common sampling strategies can underestimate horticultural contaminant loadings. Load estimates for mercury and copper derived from hourly samples were 1.6- to 7- fold greater than loads from daily sample data collected over 79 days with varying rainfall. These high contaminant concentrations and loads are of concern to food products receiving irrigation and protected waterbodies downstream. (C) 2021 Elsevier Ltd. All rights reserved.
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17.
  • Correa, R. E., et al. (author)
  • Groundwater Carbon Exports Exceed Sediment Carbon Burial in a Salt Marsh
  • 2022
  • In: Estuaries and Coasts. - : Springer Science and Business Media LLC. - 1559-2723 .- 1559-2731. ; 45, s. 1545-61
  • Journal article (peer-reviewed)abstract
    • Salt marshes can sequester large amounts of carbon in sediments, but the relation between carbon storage and exportation remains poorly understood. Groundwater exchange can flush sediment carbon to surface waters and potentially reduce storage. In this study, we estimated groundwater fluxes and associated carbon fluxes using a radon (Rn-222) mass balance and sediment carbon burial rates using lead (Pb-210) in a pristine salt marsh (North Inlet, SC, USA). We used delta C-13 to trace carbon origins. We found that groundwater releases large amounts of carbon to the open ocean. These groundwater fluxes have the potential to export 7.2 +/- 5.5 g m(-2) of dissolved inorganic carbon (DIC), 0.2 +/- 0.2 g m(-2) of dissolved organic carbon (DOC) and 0.7 +/- 0.5 g m(-2) of carbon dioxide (CO2) per day. The fluxes exceed the average surface water CO2 emissions (0.6 +/- 0.2 g m(-2) day(-1)) and the average sediment carbon burial rates (0.17 +/- 0.09 g m(-2) day(-1)). The delta C-13 results suggest that groundwater carbon originated from salt marsh soils, while the sediment carbon source is derived from salt marsh vegetation. We propose that the impact of salt marshes in carbon cycling depends not only on their capacity to bury carbon in sediments, but also on their high potential to export carbon to the ocean via groundwater pathways.
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18.
  • Reading, M. J., et al. (author)
  • Submarine groundwater discharge drives nitrous oxide source/sink dynamics in a metropolitan estuary
  • 2021
  • In: Limnology and Oceanography. - : Wiley. - 0024-3590 .- 1939-5590. ; 66:5, s. 1665-1686
  • Journal article (peer-reviewed)abstract
    • Coastal waterways can be significant sources of the potent greenhouse gas nitrous oxide (N2O) due to nitrogen inputs and eutrophication. Here, we quantify groundwater derived N2O inputs and atmospheric emissions within a modified urban embayment (Sydney Harbour, Australia). Overall, we found low N2O saturation (91-171%) and air-water fluxes (-2.2 to 24.6 mu mol m(-2) d(-1)). Concentrations were highest in upstream brackish areas and a commercial/industrial subembayment. Dissolved inorganic nitrogen concentrations were low and inversely correlated to N2O throughout the harbor. N2O surface water dynamics were apparently driven by saline submarine groundwater discharge, as quantified by the radioisotope tracer radon-222. Groundwater discharge was highest within the embayments and mangrove-lined upper estuary. While groundwater was a net N2O source to surface waters, two upstream sub-embayments featured groundwater N2O concentrations lower than surface water, suggesting a sink driven by surface waters recirculating in intertidal sediments. Surface-water N2O was undersaturated within one upstream embayment, likely due to N2O consumption within sediments. Contrastingly, the downstream embayments featured higher groundwater N2O and accounted for 45% +/- 21% of the groundwater N2O flux. Sydney Harbour was a net source of N2O to the atmosphere (mean 0.6 +/- 0.3 mu mol m(-2) d(-1)) with larger N2O fluxes occurring from relatively small areas. N2O emissions (expressed in CO2 equilivents) were equivalent to 17% of CO2 emission estimates from previous studies. The low N2O emissions in Sydney Harbour contrast with other modified estuaries which often emit higher N2O fluxes due to larger nitrogen inputs.
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19.
  • Wadnerkar, P. D., et al. (author)
  • Contrasting Radium-Derived Groundwater Exchange and Nutrient Lateral Fluxes in a Natural Mangrove Versus an Artificial Canal
  • 2021
  • In: Estuaries and Coasts. - : Springer Science and Business Media LLC. - 1559-2723 .- 1559-2731. ; 44, s. 123-136
  • Journal article (peer-reviewed)abstract
    • Artificial canals may function differently than the natural coastal wetlands, floodplains, and estuaries they often replace. Here, we assess the impact of canal estate development on saline groundwater exchange (tidal pumping) and associated nutrient fluxes. Time series observations of short-lived radium isotopes and dissolved nutrients were performed in a canal estate and a nearby mangrove creek in subtropical Australia. A mass balance model based on(223)Ra (1.3 +/- 0.4 and 3.4 +/- 0.9 cm day(-1)in the mangrove and canal, respectively) and(224)Ra (2.8 +/- 3.0 and 5.4 +/- 4.6 cm day(-1)) revealed tidally driven groundwater exchange rates were similar to 2-fold greater in the canal. Lateral fluxes of total dissolved nitrogen (TDN) from the nearby estuary into the canal estate were comparable with the mangrove creek (8.4 and 9.1 mmol m(-2) day(-1)in the mangrove and canal, respectively). Groundwater flows into the canal released similar to 5-fold more TDN than the mangrove. As expected, mangroves appear to be more efficient at retaining groundwater-derived nitrogen than vegetation-stripped, sandy canals. Overall, this study demonstrates that land reclamation for canal estate development not only drives losses of ecosystem services, but also modifies groundwater and related nutrient exchange with coastal surface waters.
  •  
20.
  • Wadnerkar, P. D., et al. (author)
  • Nitrate removal and nitrous oxide production from hothouse effluent draining to a pipe bioreactor
  • 2022
  • In: Ecological Engineering. - : Elsevier BV. - 0925-8574. ; 178
  • Journal article (peer-reviewed)abstract
    • Agricultural hothouses are intensive food production systems relying on high fertilization and irrigation. Runoff from hothouses can contain high levels of nitrogen (N) and drain into streams. Here, we investigate the effectiveness of buried, inline woodchip bioreactors constructed using PVC pipes in removing nitrate (NO3−-N) and the possibility of pollution swapping from nitrate to the greenhouse gas nitrous oxide (N2O). Mean dissolved NO3−-N removal and N2O gas production were 6.0 ± 5.2 g N m−3 h−1 (0.9–12.3 g N m−3 h−1), and 35.1 ± 31.4 mg N L−1 h−1 (14–83 mg N L−1 h−1) respectively, across five surveys. NO3−-N removal and N2O-N production occurred primarily in hypoxic to anoxic conditions. Overall, these inline pipe bioreactors achieved nitrate removal efficiencies (NRE) of 14.5 ± 6.8% (8.2%–25.0%) and N2O production equivalent to 0.7 ± 0.6% (0.3–1.4%) of nitrate removal. Comparisons to the literature indicate that our bioreactors have a low NRE but a very high nitrate removal rate (NRR) on a woodchip volume basis. The bioreactor was operating at 21% water capacity. Therefore, increasing the bioreactor water height would be needed to maximize nitrate removal. Our results imply that these bioreactors can efficiently remove NO3-N without major N2O release to the atmosphere. © 2022 Elsevier B.V.
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21.
  • White, S. A., et al. (author)
  • Anthropogenic nitrate attenuation versus nitrous oxide release from a woodchip bioreactor
  • 2022
  • In: Environmental Pollution. - : Elsevier BV. - 0269-7491. ; 300
  • Journal article (peer-reviewed)abstract
    • Nitrogen loss via overland flow from agricultural land use is a global threat to waterways. On-farm denitrifying woodchip bioreactors can mitigate NO3− exports by increasing denitrification capacity. However, denitrification in sub-optimal conditions releases the greenhouse gas nitrous oxide (N2O), swapping the pollution from aquatic to atmospheric reservoirs. Here, we assess NO3−-N removal and N2O emissions from a new edge-of-field surface-flow bioreactor during ten rain events on intensive farming land. Nitrate removal rates (NRR) varied between 5.4 and 76.2 g NO3−-N m−3 wetted woodchip d−1 with a mean of 30.3 ± 7.3 g NO3−-N m−3. The nitrate removal efficiency (NRE) was ∼73% in ideal hydrological conditions and ∼18% in non-ideal conditions. The fraction of NO3−-N converted to N2O (rN2O) in the bioreactor was ∼3.3 fold lower than the expected 0.75% IPCC emission factor. We update the global bioreactor estimated Q10 (NRR increase every 10 °C) from a recent meta-analysis with previously unavailable data to >20 °C, yielding a new global Q10 factor of 3.1. Mean N2O CO2-eq emissions (431.9 ± 125.4 g CO2-eq emissions day−1) indicate that the bioreactor was not significantly swapping aquatic NO3− for N2O pollution. Our estimated NO3−-N removal from the bioreactor (9.9 kg NO3−-N ha−1 yr−1) costs US$13.14 per kg NO3−-N removed and represents ∼30% NO3−-N removal when incorporating all flow and overflow events. Overall, edge-of-field surface-flow bioreactors seem to be a cost-effective solution to reduce NO3−-N runoff with minor pollution swapping to N2O. © 2022
  •  
22.
  • White, S. A., et al. (author)
  • Natural attenuation of large anthropogenic nitrate loads in a subtropical stream revealed by delta N-15 and delta O-18
  • 2021
  • In: Journal of Hydrology. - : Elsevier BV. - 0022-1694. ; 598
  • Journal article (peer-reviewed)abstract
    • Nitrogen pollution in subtropical waters is rapidly increasing due to land-use change, but specific sources, transformations, and attenuation rates remain understudied compared to cooler temperate catchments. Here, we quantify high-resolution nitrate (NO3--N) loads, sources and natural attenuation in a subtropical creek in Australia over contrasting hydrological conditions. We observed large creek NO3-N loads (ranging from 44 to 2938 mu mol m(-2) catchment d(-1)) exceeding the bottom-up estimates of nitrogen input to the catchment at the most upstream sites. Stable isotope natural abundances (delta N-15 and delta O-18 in NO3--N) and Bayesian analysis revealed that greywater was the dominant source accounting for similar to 55% of NO3--N in the upper creek, but fertilisers (similar to 29%) and rainfall (similar to 16%) were also relevant NO3--N sources. NO3--N loads at the most downstream site were only 0.2-9.7% of loads at the most upstream site. The resulting NO3--N attenuation efficiency (mainly via denitrification) was 52-84% of original upstream load per km of creek, depending on hydrological conditions. This large capacity to attenuate NO3--N during dry and first-flush events exceeds the attenuation found in temperate creeks subject to several decades of pollution in the northern hemisphere. During periods of high water flow and saturated soils, high NO3--N loads were exported downstream, turning the creek from a natural bioreactor to a system resembling a flow-through pipe. In spite of effective natural nitrogen attenuation providing a valuable ecosystem service, concentrations and loads remained well above expected for natural systems and water quality guidelines. Overall, our results highlight the need for modifying fertiliser use, capturing nitrogen on farms and reducing greywater nitrogen to prevent significant losses to subtropical waterways.
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23.
  • Woodrow, R. L., et al. (author)
  • Nitrous oxide hot moments and cold spots in a subtropical estuary: Floods and mangroves
  • 2022
  • In: Estuarine, Coastal and Shelf Science. - : Elsevier BV. - 0272-7714. ; 264
  • Journal article (peer-reviewed)abstract
    • Flood events can transport large nitrogen loads to the ocean in short periods with the potential to produce significant nitrous oxide (N2O) emissions along an estuarine gradient. Here, we evaluate temporal and spatial N2O air-water fluxes from both seasonal, and flood-event timescales in an urban subtropical estuary surrounded by mangroves (Coffs Creek, Australia). Overall, the estuary was a minor atmospheric source of N2O with emissions of 3.9 ± 1.2 μmol m−2 d−1. However, the mangrove-dominated lower estuary was a sink of N2O in the dry months (−5.4 ± 2.2 μmol m−2 d−1), then a source in the wet months (11.7 ± 1.6 μmol m−2 d−1) and also during an eight-day flood event (66.9 ± 9.8 μmol m−2 d−1). The flood event drove changes in estuary N2O dynamics, creating a ‘hot moment’ with the highest N2O emissions following the transport of nitrate + nitrite (NOX) from the modified catchment. The hot moment coincided with a 13-fold increase in mean daily N2O emissions and increased annual net emissions estimates to the atmosphere by 41%. In the mangrove-dominated creek sections, N2O was consumed in the dry conditions (cold spots). Seasonal variation was prominent in the attenuation and consumption of N2O in the mangrove dominated sections of the creek, while flood events potentially reduce natural creek NOX attenuation capacity and elevate N2O emissions. Without observation s in both seasonal and episodic rainfall timeframes, estuarine N2O studies in subtropical regions may underestimate N2O emissions and budgets. © 2021 Elsevier Ltd
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24.
  • Andrews, L. F., et al. (author)
  • Hydrological, geochemical and land use drivers of greenhouse gas dynamics in eleven sub-tropical streams
  • 2021
  • In: Aquatic Sciences. - : Springer Science and Business Media LLC. - 1015-1621 .- 1420-9055. ; 83:2
  • Journal article (peer-reviewed)abstract
    • Greenhouse gas (GHG) emissions from freshwater streams are poorly quantified in sub-tropical climates, especially in the southern hemisphere where land use is rapidly changing. Here, we examined the distribution, potential drivers, and emissions of carbon dioxide (CO2), nitrous oxide (N2O) and methane (CH4) from eleven Australian freshwater streams with varying catchment land uses yet similar hydrology, geomorphology, and climate. These sub-tropical streams were a source of CO2 (74 +/- 39 mmol m(-2) day(-1)), CH4 (0.04 +/- 0.06 mmol m(-2) day(-1)), and N2O (4.01 +/- 5.98 mu mol m(-2) day(-1)) to the atmosphere. CO2 accounted for similar to 97% of all CO2-equivalent emissions with CH4 (similar to 1.5%) and N2O (similar to 1.5%) playing a minor role. Episodic rainfall events drove changes in stream GHG due to the release of soil NOx (nitrate + nitrite) and dissolved organic carbon (DOC). Groundwater discharge as traced by radon (Rn-222, a natural groundwater tracer) was not an apparent source of CO2 and CH4, but was a source of N2O in both agricultural and forest catchments. Land use played a subtle role on greenhouse gas dynamics. CO2 and CH4 increased with catchment forest cover during the wet period, while N2O and CH4 increased with agricultural catchment area during the dry period. Overall, this study showed how DOC and NOx land use, and rainfall events interact to drive spatial and temporal dynamics of GHG emissions in sub-tropical streams using multiple linear regression modelling. Increasing intensive agricultural land use will likely decrease regional CO2 and CH4 emissions, but increase N2O.
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25.
  • Brown, Dylan R., et al. (author)
  • Hypersaline tidal flats as important "blue carbon" systems : a case study from three ecosystems
  • 2021
  • In: Biogeosciences. - : COPERNICUS GESELLSCHAFT MBH. - 1726-4170 .- 1726-4189. ; 18:8, s. 2527-2538
  • Journal article (peer-reviewed)abstract
    • Hypersaline tidal flats (HTFs) are coastal ecosystems with freshwater deficits often occurring in arid or semiarid regions near mangrove supratidal zones with no major fluvial contributions. Here, we estimate that organic carbon (OC), total nitrogen (TN) and total phosphorus (TP) were buried at rates averaging 21 (+/- 6), 1.7 (+/- 0.3) and 1.4 (+/- 0.3) gm(-2) yr(-1), respectively, during the previous century in three contrasting HTF systems, one in Brazil (eutrophic) and two in Australia (oligotrophic). Although these rates are lower than those from nearby mangrove, saltmarsh and seagrass systems, the importance of HTFs as sinks for OC, TN and TP may be significant given their extensive coverage. Despite the measured short-term variability between net air-saltpan CO2 influx and emission estimates found during the dry and wet season in the Brazilian HTF, the only site with seasonal CO2 flux measurements, the OC sedimentary profiles over several decades suggest efficient OC burial at all sites. Indeed, the stable isotopes of OC and TN (delta C-13 and delta N-1(5)) along with C : N ratios show that microphytobenthos are the major source of the buried OC in these HTFs. Our findings highlight a previously unquantified carbon as well as a nutrient sink and suggest that coastal HTF ecosystems could be included in the emerging blue carbon framework.
  •  
26.
  • Cabral dos Santos, Alex, 1990, et al. (author)
  • Carbon and alkalinity outwelling across the groundwater-creek-shelf continuum off Amazonian mangroves
  • 2021
  • In: Limnology And Oceanography Letters. - : Wiley. - 2378-2242. ; 6:6, s. 369-378
  • Journal article (peer-reviewed)abstract
    • Lateral fluxes (i.e., outwelling) of dissolved organic (DOC) and inorganic (DIC) carbon and total alkalinity were estimated using radium isotopes at the groundwater, mangrove creek, and continental shelf scales in the Amazon region. Observations of salinity and radium isotopes in the creek indicated tidally driven groundwater exchange as the main source of carbon. Radium-derived transport rates indicate that mangrove carbon is exported out of the continental shelf on timescales of 22 ± 7d. Bicarbonate was the main form (82% ± 11%) of total dissolved carbon in all samples, followed by DOC (13% ± 12%) and CO2 (5% ± 4%). DIC (18.7 ± 15.7 mmol m−2d−1) exceeded DOC (3.0 ± 4.1 mmol m−2d−1) outwelling at all spatial scales. The interpretation of outwelling across the mangrove-ocean continuum is related to the spatial and temporal scales investigated. At all scales, outwelling represented a major coastal carbon pathway driving bicarbonate storage in the ocean.
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27.
  • Cabral dos Santos, Alex, 1990, et al. (author)
  • Fresh and saline submarine groundwater discharge as sources of carbon and nutrients to the Japan Sea
  • 2023
  • In: Marine Chemistry. - : Elsevier BV. - 0304-4203. ; 249
  • Journal article (peer-reviewed)abstract
    • Submarine groundwater discharge (SGD) is an important pathway for carbon and nutrients to the coastal ocean, sometimes exceeding river inputs. SGD fluxes can have implications for long-term carbon storage, ocean acidification and nutrient dynamics. Here, we used radium (223Ra and 226Ra) isotopes to quantify SGD-derived fluxes of dissolved inorganic (DIC) and organic (DOC) carbon, nitrate (NO3−), nitrite (NO2−), ammonium (NH4+) and phosphate (PO43−) in a spring-fed coastal bay in the Japan Sea. The average coastal water residence times using 223Ra/226Ra ratios was 32.5 ± 17.9 days. Fresh and saline SGD were estimated using a radium mixing model with short- and long-lived isotopes. The volume of fresh SGD entering the bay (4.6 ± 4.6 cm day−1) was more than twice that of the volume of saline SGD (1.9 ± 2.1 cm day−1). Fresh SGD (mmol m2 day−1) was the main source of DOC (2.7 ± 2.6), DIC (13.9 ± 13.7), PO43− (0.3 ± 0.3) and NO3− (6.6 ± 6.5) to the coastal ocean, whereas saline SGD was the main source of NH4+ (0.2 ± 0.2). Total SGD-derived carbon and nutrient fluxes were 4 – 7 and 2–16 times greater than local river inputs. Positive correlations between chlorophyll-a, 226Ra and δ13C-DIC indicate that SGD significantly (p < 0.05) enhances primary productivity nearshore. Overall, fresh SGD of nitrogen and carbon to seawater drove chlorophyll-a, decreased DIC/Alkalinity ratios, and modified the carbonate biogeochemistry of the coastal ocean.
  •  
28.
  • Cabral dos Santos, Alex, 1990, et al. (author)
  • Tidally driven porewater exchange and diel cycles control CO2 fluxes in mangroves on local and global scales
  • 2024
  • In: Geochimica et Cosmochimica Acta. - 0016-7037. ; 374, s. 121-135
  • Journal article (peer-reviewed)abstract
    • Mangrove soils are highly enriched in organic carbon. Tidal pumping drives seawater and oxygen into mangrove soils during flood tide and releases carbon-rich porewater during ebb tides. Here, we resolve semi-diurnal (flood/ebb tides), diel (day/night) and weekly (neap/spring tides) drivers of porewater-derived CO2 fluxes in two mangroves and update global estimates of CO2 emissions building on earlier observations from other sites. Tidal pumping controlled pCO2 variability within the two mangrove creeks. The highest values of pCO2 (2,585–6,856 µatm) and 222Rn (2,315–6,159 dpm m−3) and lowest values of pH (6.8–7.1) and dissolved oxygen (1.7–3.7 mg L−1) at low tides were due to enhanced porewater export. 222Rn and pCO2 in mangrove porewater were 4–15 and 38–41 times greater than surface waters, respectively. pCO2 increased by 50 ± 30 % from high to low tide, 9 ± 22 % from day to night and 57 ± 5 % from neap to spring tide with clear changes in hourly, diel, and weekly time scales. Combining our new estimates with literature data, global porewater-derived (16 sites) and water-atmosphere (52 sites) CO2 fluxes in mangroves would upscale to 45 ± 12 and 41 ± 10 Tg C y−1, respectively. These fluxes represent 25 % of net primary production and are twice as high as the sediment carbon burial rates in global mangroves. Overall, our local observations and global compilation suggest that porewater-derived CO2 exchange is a major but often unaccounted source of CO2 in mangroves. The porewater-derived CO2 can be emitted to the atmosphere or laterally exported to the ocean and should be included in carbon budgets to solve global imbalances.
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29.
  • Cheung, Henry Lok Shan, et al. (author)
  • Denitrification, anammox, and DNRA in oligotrophic continental shelf sediments
  • 2024
  • In: Limnology and Oceanography. - 1939-5590 .- 0024-3590.
  • Journal article (peer-reviewed)abstract
    • Continental shelf sediments are considered hotspots for nitrogen (N) removal. While most investigations have quantified denitrification in shelves receiving large amounts of anthropogenic nutrient supply, we lack insight into the key drivers of N removal on oligotrophic shelves. Here, we measured rates of N removal through denitrification and anammox by the revised-isotope pairing technique (r-IPT) along the Northeastern New Zealand shelf. Denitrification dominated total N2 production at depths between 30 and 128 m with average rates (± SE) ranging from 65 ± 28 to 284 ± 72 μmol N m−2 d−1. N2 production by anammox ranged from 3 ± 1 to 28 ± 11 μmol N m−2 d−1 and accounted for 2–19% of total N2 production. DNRA was negligible in these oligotrophic settings. Parallel microbial community analysis showed that both Proteobacteria and Planctomycetota were key taxa driving denitrification. Denitrification displayed a negative correlation with oxygen penetration depth, and a positive correlation with macrofauna abundance. Our denitrification rates were comparable to oligotrophic shelves from the Arctic, but were lower than those from nutrient-rich Pacific and Atlantic shelves. Based on our results and existing IPT measurements, the global shelf denitrification rate was reassessed to be 53.5 ± 8.1 Tg N yr−1, equivalent to 20 ± 2% of marine N removal. We suggest that previous estimates of global shelf N loss might have been overestimated due to sampling bias toward areas with high N loads in the Northern Hemisphere.
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30.
  • Conrad, S. R., et al. (author)
  • Assessing pesticide, trace metal, and arsenic contamination in soils and dam sediments in a rapidly expanding horticultural area in Australia
  • 2021
  • In: Environmental Geochemistry and Health. - : Springer Science and Business Media LLC. - 0269-4042 .- 1573-2983. ; 43, s. 3189-3211
  • Journal article (peer-reviewed)abstract
    • Industrial horticulture can release pesticides and trace metals/metalloids to terrestrial and aquatic environments. To assess long-term and more recent land contamination from an expanding horticultural region, we sampled soils from chemical mixing, crop production, and drainage areas, as well as retention reservoirs (dam) sediments, from 3 blueberry farms with varying land-use history in subtropical Australia. Soils were analysed for 97 different pesticides and trace metal/metalloid contents. The most recent farm had fungicides propiconazole and cyprodinil contents that may compromise soil invertebrate survival and/or nutrient recycling (5-125 mg kg(-1)). A site previously used to cultivate bananas had 6 dam sediment subsamples with arsenic contents over sediment quality guidelines (SQG); however, the soil content values were just below Australian health investigation levels (100 mg kg(-1)). Arsenic is suspected to originate from pesticide application during previous banana cultivation in the region. Dam sediment cores at all sites had mercury contents over the SQG likely due to fungicides or fertiliser impurities. Mean contents of mercury from dam sediments (141 +/- 15.5 mu g kg(-1)) were greater than terrestrial soils (78 +/- 6.5 mu g kg(-1)), and sediment profiles suggest mercury retention in anoxic sediments. Soils in chemical mixing areas at two sites were contaminated with copper and zinc which were above the national soil ecological investigation levels. Based on toxicity data, distribution, persistence, and mobility, we identified the fungicide cyprodinil, mercury, and phosphorus as contaminants of the greatest concern in this intensive horticulture area of Australia. Additional sampling (spatial, chemical speciation, biotic) is required to support mitigation efforts of the emerging contamination in the rapidly expanding blueberry farms of this region of Australia.
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31.
  • Conrad, S. R., et al. (author)
  • Elevated dissolved heavy metal discharge following rainfall downstream of intensive horticulture
  • 2020
  • In: Applied Geochemistry. - : Elsevier BV. - 0883-2927. ; 113
  • Journal article (peer-reviewed)abstract
    • Heavy metals may be released from soils during rain events. Observations during the first flush (rain event preceded by dry period) are difficult, but may account for a large fraction of annual loads. Here, we report detailed time series measurements of dissolved heavy metals and the groundwater tracer radon (Rn-222) over multiple rain events from a creek draining a catchment dominated by intensive horticulture on the subtropical east coast of Australia. The creek drains to an intermittently closed and open lake or lagoon (ICOLL), a typical estuary type along the east coast of Australia. A sandbank prevents the estuary mouth from connecting with the ocean during dry conditions. Following a 109 mm rain event, the ICOLL began to drain to the coastal ocean. Mean export of Hg, Cu, and Zn was 0.23 +/- 0.05, 1.06 +/- 0.25, and 15.70 +/- 2.69 g m(-2) day(-1) for the entire time series and 0.72 +/- 0.17, 1.27 +/- 0.12, 24.14 +/- 3.82 g m(-2) day(-1) averaged from high resolution sampling over 72 h of the first flush event. Trends of Hg export differed from the other heavy metals. Over 79% of the estimated Hg export occurred within 72 h of the ICOLL opening, compared to 30 and 38% of Cu and Zn. The first flush and subsequent major rain events (> 50 mm day(-1)) drove concentrations of Hg, Cu and Zn to exceed the Australia and New Zealand Environment and Conservation Council (ANZECC) water quality guidelines (WQG) for both fresh and marine water. Comparisons of heavy metal export to downstream estuary sediment burial rates revealed that the estuary is likely a source of dissolved Hg and Cd to the coastal ocean when the ICOLL is open.
  •  
32.
  • Cotovicz Jr, Luiz C., et al. (author)
  • Methane oxidation minimizes emissions and offsets to carbon burial in mangroves
  • 2024
  • In: NATURE CLIMATE CHANGE. - 1758-678X .- 1758-6798.
  • Journal article (peer-reviewed)abstract
    • Maximizing carbon sequestration in mangroves is part of the global effort to combat the climate crisis. However, methane (CH4) emissions can partially offset carbon sequestration in mangroves. Previous estimates have suggested that CH4 emissions offset organic carbon burial by 20% in mangroves with substantial freshwater inputs and/or in highly impacted mangroves. Here we resolve the magnitude and drivers of the mangrove CH4 offset using multiple isotopic tracers across a latitudinal gradient. CH4 emission offsets were smaller in high-salinity (similar to 7%) than in freshwater-influenced (similar to 27%) mangroves. Carbon sequestration was disproportionally high compared with CH4 emissions in understudied tropical areas. Low CH4 emissions were explained by minor freshwater inputs minimizing CH4 production in saline, high-sulfate conditions and intense CH4 oxidation in porewaters and surface waters. CH4 oxidation in mangrove surface waters reduced potential aquatic CH4 emissions by 10-33%. Overall, carbon sequestration through mangrove preservation and restoration is less affected by CH4 emissions than previously thought.
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33.
  • Davis, K., et al. (author)
  • Altered groundwater discharge and associated carbon fluxes in a wetland-drained coastal canal
  • 2020
  • In: Estuarine, Coastal and Shelf Science. - : Elsevier BV. - 0272-7714. ; 235
  • Journal article (peer-reviewed)abstract
    • Residential canal systems are becoming increasingly popular with the rising demand for absolute coastal waterfront properties. We hypothesize that canals alter groundwater-surface water connectivity and related carbon fluxes into coastal surface waters. Here, we quantified submarine groundwater discharge (SGD) in a residential canal system on Bribie Island (Australia) and associated carbon fluxes. SGD rates estimated from a radon (222Rn) mass balance model were 3.1 ± 1.5 cm d−1. These fluxes delivered 68 ± 44 and 70 ± 48 mmol m−2 d−1 of dissolved inorganic carbon (DIC) and dissolved organic carbon (DOC) into the canal, respectively. Carbon dioxide (CO2) emissions to the atmosphere ranged from 15 to 28 mmol m−2 d−1. Multiple lines of evidence, including flux estimates and groundwater observations, converge to the conclusion that SGD was a major source of DOC and free CO2, but not carbonate alkalinity nor DIC to canal surface waters. In comparison to mangrove tidal creeks that often precede canals, the canal had (1) lower tidally-driven saline groundwater exchange rates but higher fresh groundwater discharge, (2) lower CO2 emissions to the atmosphere; and (3) acted as a driver rather than a buffer of local ocean acidification. These differences seem to be driven by the replacement of intertidal wetland vegetation with urban areas that prevent soil carbon accumulation and related biogeochemical processes around the canals. We suggest that decisions on canal construction should consider potential changes to groundwater-derived soil carbon losses and carbon cycling in receiving coastal waters. © 2020 Elsevier Ltd
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34.
  • Davis, K. L., et al. (author)
  • Calcification and organic productivity at the world's southernmost coral reef
  • 2020
  • In: Marine Chemistry. - : Elsevier BV. - 0304-4203. ; 227
  • Journal article (peer-reviewed)abstract
    • Estimates of coral reef calcification and organic productivity provide valuable insight to community functionality and the response of an ecosystem to stress events. High-latitude coral reefs are expected to experience rapid changes in calcification rates and become refugia for tropical species following climate change and increasing bleaching events. Here, we estimate ecosystem-scale calcification and organic productivity at the world's southernmost coral reef using seawater carbon chemistry observations (Lord Howe Island, Australia). We reduce uncertainties in metabolic calculations by producing a detailed bathymetric model and deploying two current meters to refine residence time and volume estimates. Bathymetry-modelled transect depths ranged from 74% shallower to 20% deeper than depths averaged from reef crest/flat current meters, indicating that higher-resolution depth observations help to reduce uncertainties in reef metabolic calculations. Rates of ecosystem calcification were 56.6 +/- 14.8 mmol m(-2) d(-1) in the winter and 125.3 +/- 39.4 mmol m(-2) d(-1) in the summer. These rates are lower than most other high-latitude reefs according to our compilation of high-latitude coral ecosystem metabolism estimates. Coral cover ranged from 14.7 +/- 2.3% in winter to 19.8 +/- 2.1% in the summer. A concurrent bleaching event and cyclone occurred during summer sampling (February - March 2019), resulting in 47% of corals bleached at the study site and 2% mortality due to cyclonal damage. Therefore, it is likely that the summertime G(net) rates underestimate baseline calcification. Our results enable future assessments of long-term change, but do not resolve the impact of bleaching at Lord Howe Island.
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35.
  • Giles, A. B., et al. (author)
  • Using multispectral drones to predict water quality in a subtropical estuary
  • 2022
  • In: Environmental Technology. - : Informa UK Limited. - 0959-3330 .- 1479-487X.
  • Journal article (peer-reviewed)abstract
    • Drones are revolutionising earth system observations, and are increasingly used for high resolution monitoring of water quality. The objective of this research was to test whether drone-based multispectral imagery could predict important water quality parameters in an ICOLL (intermittently closed and opened lake or lagoon). Three water quality sampling campaigns were undertaken, measuring temperature, salinity, pH, dissolved oxygen (DO), chlorophyll (CHL), turbidity, total suspended sediments (TSS), coloured dissolved organic matter (CDOM), green algae, crytophyta, diatoms, bluegreen algae and total algal concentrations. DistilM statistical analyses were conducted to reveal the bands accounting for the most variation across all water quality data, then linear correlations between specific band/band ratios and individual water quality parameters were performed. DistilM analyses revealed the NIR band accounted for most variation in March, the Green band in April and the RE band in May, and showed that the most important contributors varied significantly among campaigns and variables. Significant linear correlations with R-2 > 0.4 were obtained for eleven of the water quality parameters tested, with the strongest correlation obtained for CHL and the green band (R-2 = 0.72). The relative importance of predictor bands and observed water quality parameters varied temporally. We conclude that drones with a multispectral sensor can produce useful 'snapshot' prediction maps for a range of water quality parameters, such as chlorophyll, bluegreen algae and dissolved oxygen. However, a single model was insufficient to reproduce the temporal variation of water parameters in dynamic estuarine systems.
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36.
  • Ljungberg, Wilma, et al. (author)
  • Carbon Outwelling and Uptake Along a Tidal Glacier-Lagoon-Ocean Continuum
  • 2024
  • In: Journal of Geophysical Research (JGR): Biogeosciences. - 2169-8953 .- 2169-8961. ; 129:e2023JG007895
  • Journal article (peer-reviewed)abstract
    • Tidewater glaciers are highly vulnerable to climate change due to warming from both atmospheric and seawater sources. Most tidewater glaciers are rapidly retreating, but little is known about how glacial melting modifies coastal biogeochemical cycles. Here, we investigate carbonate and nutrient dynamics and fluxes in an expanding proglacial tidal lagoon connected to Europe's largest glacier in Iceland (Vatnajökull). The lagoon N:P:Si ratios (2:1:30) imply a system deficient in nitrogen. The large variations in the freshwater endmembers highlighted the complexity of resolving sources and transformations. The lagoon acted as a sink of dissolved inorganic carbon (DIC). Floating chamber incubations revealed a CO2 uptake of 26±15mmolm−2d−1. Lagoon waters near the glacier had a 170% higher CO2 uptake than near the lagoon mouth, likely driven by primary production stimulated by nitrogen-rich bottom water upwelling. The lateral DIC and total alkalinity (TA) flux rates (outwelling) from the lagoon to the ocean were −1.5±0.1 (export to ocean) and 23±5mmolm−2d−1 (import into the lagoon) respectively. All samples were undersaturated with respect to aragonite due to glacial meltwater dilution of TA and CO2 uptake. This implies dilution of oceanic alkalinity, lowering the nearshore buffering capacity against ocean acidification.
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37.
  • McDonough, L. K., et al. (author)
  • Changes in global groundwater organic carbon driven by climate change and urbanization
  • 2020
  • In: Nature Communications. - : Springer Science and Business Media LLC. - 2041-1723. ; 11:1
  • Journal article (peer-reviewed)abstract
    • Climate change and urbanization can increase pressures on groundwater resources, but little is known about how groundwater quality will change. Here, we use a global synthesis (n = 9,404) to reveal the drivers of dissolved organic carbon (DOC), which is an important component of water chemistry and substrate for microorganisms that control biogeochemical reactions. Dissolved inorganic chemistry, local climate and land use explained ~ 31% of observed variability in groundwater DOC, whilst aquifer age explained an additional 16%. We identify a 19% increase in DOC associated with urban land cover. We predict major groundwater DOC increases following changes in precipitation and temperature in key areas relying on groundwater. Climate change and conversion of natural or agricultural areas to urban areas will decrease groundwater quality and increase water treatment costs, compounding existing constraints on groundwater resources. © 2020, The Author(s).
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38.
  • Nobrega, M. S., et al. (author)
  • Mangrove microbiome reveals importance of sulfur metabolism in tropical coastal waters
  • 2022
  • In: Science of the Total Environment. - : Elsevier BV. - 0048-9697. ; 813
  • Journal article (peer-reviewed)abstract
    • Mangroves under macro-tidal regimes are global carbon sequestration hotspots but the microbial drivers of biogeochemical cycles remain poorly understood. Here, we investigate the drivers of mangrove microbial community composition across a porewater-creek-estuary-ocean continuum. Observations were performed on the Amazon region in one of the largest mangrove systems worldwide with effective sequestration of organic carbon buried in soils and dissolved carbon via outwelling to the ocean. The potential export to the adjacent oceanic region ranged from 57 to 380 kg of dissolved and particulate organic carbon per second (up to 33 thousand tons C per day). Macro tides modulated microbial communities and their metabolic processes, e.g., anoxygenic phototrophy, sulfur, and nitrogen cycling. Respiration, sulfur metabolism and dissolved organic carbon (DOC) levels were linked to functional groups and microbial cell counts. Total microbial counts decreased and cyanobacteria counts peaked in the spring tide. The microbial groups driving carbon, nitrogen, sulfur and methane cycles were consistent across all spatial scales. Taxonomic groups engaged in sulfur cycling (Allochromatium, Desulfovibrio, and Thibacillus) within mangroves were abundant at all scales. Tidally-driven porewater exchange within mangroves drove a progressive increase of sulfur cycle taxonomic groups and their functional genes both temporally (tidal cycles) and spatially (from mangrove porewater to continental shelf). Overall, we revealed a unified and consistent response of microbiomes at different spatial and temporal scales to tidally-driven mangrove porewater exchange.
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39.
  • Passos, T., et al. (author)
  • Increasing carbon, nutrient and trace metal accumulation driven by development in a mangrove estuary in south Asia
  • 2022
  • In: SCIENCE OF THE TOTAL ENVIRONMENT. - : Elsevier BV. - 0048-9697. ; 832
  • Journal article (peer-reviewed)abstract
    • Mangrove forests sequester organic carbon, nutrients and toxic metals sorbed to fine sediment, and thus restrict the mobility of pollutants through estuarine environments. However, mangrove removal and environmental degradation caused by industrial activity and urban growth can impact the ability of mangrove communities to provide these critical ecosystem services. Here, we use sediment profiles from an impacted tropical estuary in southwest India to provide a c. 70-year record of carbon, nutrient and trace metal burial in the context of rapid urban development and the systemic removal of mangrove communities. Our results show that carbon and nutrient accumulation rates increase sharply during the 1990's in accordance with the high rates of deforestation. Nitrogen and phosphorus accumulation rates increased fourfold and twofold, respectively, during the same period. Organic carbon accumulation was fivefold higher than the global average during this period, reflecting intense deforestation during the last three decades. The enrichment of Hg, Zn, Pb, Mo, Ni, Cu and Mn demonstrate clear anthropogenic impact starting in the 1950's and peaking in 1990. Mercury, the trace metal with the highest enrichment factor, increased sevenfold in the most recent sediments due to increased fossil fuel emissions, untreated water and incineration of medical waste and/or fertilizers used in aquaculture. Organic carbon isotope (delta C-13) and C:N molar ratios indicate shifts to more terrestrial-derived source of organic matter in the most recent sediments reflecting growing deforestation of which may be prevalent in southeast Asia due to increasing development. This study emphasizes the critical role played by mangrove ecosystems in attenuating anthropogenically-derived pollutants, including carbon sequestration, and reveals the long-term consequences of mangrove deforestation in the context of rapidly developing economies.
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40.
  • Reading, M. J., et al. (author)
  • Land use drives nitrous oxide dynamics in estuaries on regional and global scales
  • 2020
  • In: Limnology and Oceanography. - : Wiley. - 0024-3590 .- 1939-5590. ; 65:8, s. 1903-20
  • Journal article (peer-reviewed)abstract
    • Urban and agricultural development of coastal catchments is known to increase dissolved nitrogen inputs into estuaries; however, much less is known about how land use influences the production of the powerful greenhouse gas nitrous oxide (N2O). Here, we assess dissolved N2O dynamics in four nearby estuaries across a regional land use gradient and summarize the literature to put the observations into global perspective. During summer dry conditions, N2O saturation ranged from 131.4% +/- 45.0% in the most pristine system (28% modified) to 198.6% +/- 52.3% within the most modified urban system (91% modified). The N2O saturation in the wetter winter campaign was higher and more variable than the summer dry campaign (range 84.7-677.7%) likely due to direct transport of N2O into the estuaries from catchment runoff and/or produced through denitrification fueled by high nitrate inputs. During both seasons, N2O was lowest in areas adjacent to fringing mangroves and highest in upstream fresh/saltwater mixing areas. Coupling our results with previously published N2O data from 50 estuarine systems worldwide revealed that estuarine N2O increases concomitantly with catchment modification, dissolved inorganic nitrogen availability, and decreasing oxygen concentrations. Based on these results, a 1% increase in anthropogenic modification to global catchments (i.e., agricultural development and/or urbanization) may increase estuarine N2O saturation by 2.6% +/- 1.2%. These findings indicate that future estuarine N2O emissions are likely to increase as anthropogenic modification of coastal catchments intensifies.
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41.
  • Reading, M. J., et al. (author)
  • Spatial Distribution of CO2, CH4, and N2O in the Great Barrier Reef Revealed Through High Resolution Sampling and Isotopic Analysis
  • 2021
  • In: Geophysical Research Letters. - : American Geophysical Union (AGU). - 0094-8276 .- 1944-8007. ; 48:15
  • Journal article (peer-reviewed)abstract
    • Methane (CH4) and nitrous oxide (N2O) dynamics in coastal coral reef areas are poorly understood. We measured dissolved carbon dioxide (CO2) and CH4 (with delta C-13-CO2 and delta C-13-CH4 isotope fractions) and N2O in the Great Barrier Reef (GBR) to determine spatial distributions and emissions. CO2 (379-589 mu atm) was oversaturated due to calcification and riverine sources, as indicated by depleted delta C-13-CO2 values. CH4 (1.5-13.5 nM) was also oversaturated from nearshore biogenic sources indicated by depleted delta C-13-CH4 and probable offshore aerobic production. N2O (5.5-6.6 nM) was generally undersaturated, with uptake highest near the coast. Daily CO2 emissions were 5826 +/- 1191 tonnes, with CO2 equivalent ((eq)) N2O uptake (191 +/- 44 tonnes) offsetting 3.3% of CO2 or 89% of CH4eq (214 +/- 45 tonnes) emissions based on 20-year global warming potentials. The GBR was a slight CO2 and CH4 source and N2O sink during our study. However, further work is required to constrain diurnal, seasonal, and spatial dynamics.
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42.
  • Reithmaier, Gloria M.S., et al. (author)
  • Carbonate chemistry and carbon sequestration driven by inorganic carbon outwelling from mangroves and saltmarshes
  • 2023
  • In: Nature Communications. - 2041-1723. ; 14:1
  • Journal article (peer-reviewed)abstract
    • Mangroves and saltmarshes are biogeochemical hotspots storing carbon in sediments and in the ocean following lateral carbon export (outwelling). Coastal seawater pH is modified by both uptake of anthropogenic carbon dioxide and natural biogeochemical processes, e.g., wetland inputs. Here, we investigate how mangroves and saltmarshes influence coastal carbonate chemistry and quantify the contribution of alkalinity and dissolved inorganic carbon (DIC) outwelling to blue carbon budgets. Observations from 45 mangroves and 16 saltmarshes worldwide revealed that >70% of intertidal wetlands export more DIC than alkalinity, potentially decreasing thepH of coastal waters. Porewater-derived DIC outwelling (81 ± 47 mmol m−2 d−1 in mangroves and 57 ± 104 mmol m−2 d−1 in saltmarshes) was the major term in blue carbon budgets. However, substantial amounts of fixed carbon remain unaccounted for. Concurrently, alkalinity outwelling was similar or higher than sediment carbon burial and is therefore a significant but often overlooked carbon sequestration mechanism.
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43.
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44.
  • Santos, Isaac R., et al. (author)
  • Submarine groundwater discharge impacts on coastal nutrient biogeochemistry
  • 2021
  • In: Nature Reviews Earth & Environment. - : Springer Science and Business Media LLC. - 2662-138X. ; 2:5, s. 307-323
  • Journal article (peer-reviewed)abstract
    • Submarine groundwater discharge (SGD) links terrestrial and marine systems, but has often been overlooked in coastal nutrient budgets because it is difficult to quantify. In this Review, we examine SGD nutrient fluxes in over 200 locations globally, explain their impact on biogeochemistry and discuss broader management implications. SGD nutrient fluxes exceed river inputs in similar to 60% of study sites, with median total SGD fluxes of 6.0 mmol m(-2) per day for dissolved inorganic nitrogen, 0.1 mmol m(-2) per day for dissolved inorganic phosphorus and 6.5 mmol m(-2) per day for dissolved silicate. SGD nitrogen input (mostly in the form of ammonium and dissolved organic nitrogen) often mitigates nitrogen limitation in coastal waters, since SGD tends to have high nitrogen concentrations relative to phosphorus (76% of studies showed N:P values above the Redfield ratio). It is notable that most investigations do not distinguish saline and fresh SGD, although they have different properties. Saline SGD is a ubiquitous, diffuse pathway releasing mostly recycled nutrients to global coastal waters, whereas fresh SGD is occasionally a local, point source of new nutrients. SGD-derived nutrient fluxes must be considered in water quality management plans, as these inputs can promote eutrophication if not properly managed.
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45.
  • Santos, Isaac R., et al. (author)
  • The renaissance of Odum's outwelling hypothesis in 'Blue Carbon' science
  • 2021
  • In: Estuarine, Coastal and Shelf Science. - : Elsevier BV. - 0272-7714 .- 1096-0015. ; 255
  • Journal article (peer-reviewed)abstract
    • The term ‘Blue Carbon’ was coined about a decade ago to highlight the important carbon sequestration capacity of coastal vegetated ecosystems. The term has paved the way for the development of programs and policies that preserve and restore these threatened coastal ecosystems for climate change mitigation. Blue carbon research has focused on quantifying carbon stocks and burial rates in sediments or accumulating as biomass. This focus on habitat-bound carbon led us to losing sight of the mobile blue carbon fraction. Oceans, the largest active reservoir of carbon, have become somewhat of a blind spot. Multiple recent investigations have revealed high outwelling (i.e., lateral fluxes or horizontal exports) of dissolved inorganic (DIC) and organic (DOC) carbon, as well as particulate organic carbon (POC) from blue carbon habitats. In this paper, we conceptualize outwelling in mangrove, saltmarsh, seagrass and macroalgae ecosystems, diagnose key challenges preventing robust quantification, and pave the way for future work integrating mobile carbon in the blue carbon framework. Outwelling in mangroves and saltmarshes is usually dominated by DIC (mostly as bicarbonate), while POC seems to be the major carbon species exported from seagrass meadows and macroalgae forests. Carbon outwelling science is still in its infancy, and estimates remain limited spatially and temporally. Nevertheless, the existing datasets imply that carbon outwelling followed by ocean storage is relevant and may exceed local sediment burial as a long-term (>centuries) blue carbon sequestration mechanism. If this proves correct as more data emerge, ignoring carbon outwelling may underestimate the perceived sequestration capacity of blue carbon ecosystems.
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46.
  • Sippo, J. Z., et al. (author)
  • Coastal carbon cycle changes following mangrove loss
  • 2020
  • In: Limnology and Oceanography. - : Wiley. - 0024-3590 .- 1939-5590. ; 65:11, s. 2642-2656
  • Journal article (peer-reviewed)abstract
    • Global mangrove loss is occurring from deforestation and extreme climatic events, but changes to the coastal carbon cycle following mangrove mortality and/or loss are not well understood. In 2015/2016, a massive climate-driven mangrove dieback event occurred over similar to 1000 km of Australian coastline. To assess carbon loss following mortality, carbon fluxes in adjacent living and dead forest areas were compared 8 and 20 months postforest dieback. Dead areas experienced an increase in soil CO2 efflux by similar to 189%, and a decrease in oceanic dissolved inorganic carbon (DIC) outwelling of similar to 50% relative to living areas. DIC outwelling (predominantly carbonate alkalinity) and soil CO2 efflux accounted for 81% and 16% of losses from the living forest, in comparison to 51% and 47%, respectively, from the dead forest. The dieback drove a shift from a dominance of oceanic carbon outwelling to increased atmospheric CO2 emissions and decreased alkalinity exports. This shift was likely driven by increased oxygen sediment permeation and the loss of mangrove net primary productivity. Combining our new observations with literature data, we found a logarithmic relationship between soil carbon loss and time since mangrove loss. Using this relationship, we estimate ongoing global carbon losses from historical mangrove deforestation and dieback could be 13.7 +/- 9.4 Tg C yr(-1), which is eightfold higher than previous estimates and offsets global mangrove carbon burial by similar to 60%. Even if no future deforestation occurred, we estimate ongoing carbon losses to the atmosphere and ocean from current global mangrove losses of 27 Tg C over the next 30 yr.
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47.
  • Tait, D. R., et al. (author)
  • Submarine Groundwater Discharge Exceeds River Inputs as a Source of Nutrients to the Great Barrier Reef
  • 2023
  • In: Environmental Science & Technology. - 0013-936X. ; 57:41, s. 15627-15634
  • Journal article (peer-reviewed)abstract
    • Rivers are often assumed to be the main source of nutrients triggering eutrophication in the Great Barrier Reef (GBR). However, existing nutrient budgets suggest a major missing source of nitrogen and phosphorus sustaining primary production. Here, we used radium isotopes to resolve submarine groundwater discharge (SGD)-derived, shelf-scale nutrient inputs to the GBR. The total SGD was similar to 10-15 times greater than average river inputs, with nearshore groundwater discharge accounting for similar to 30% of this. Total SGD accounted for >30% of all known dissolved inorganic N and >60% of inorganic P inputs and exceeded regional river inputs. However, SGD was only a small proportion of the nutrients necessary to sustain primary productivity, suggesting that internal recycling processes still dominate the nutrient budget. With millions of dollars spent managing surface water nutrient inputs to reef systems globally, we argue for a shift in the focus of management to safeguard reefs from the impacts of excess nutrients.
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48.
  • Taniguchi, M., et al. (author)
  • Submarine Groundwater Discharge: Updates on Its Measurement Techniques, Geophysical Drivers, Magnitudes, and Effects
  • 2019
  • In: Frontiers in Environmental Science. - : Frontiers Media SA. - 2296-665X. ; 7
  • Journal article (peer-reviewed)abstract
    • 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.
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49.
  • Wang, F. F., et al. (author)
  • Porewater exchange drives nutrient cycling and export in a mangrove-salt marsh ecotone
  • 2022
  • In: Journal of Hydrology. - : Elsevier BV. - 0022-1694. ; 606
  • Journal article (peer-reviewed)abstract
    • Coastal wetlands regulate nutrient fluxes from the continents to the oceans. Salt marshes are rapidly encroaching into mudflat area in mangrove wetlands, shaping a mangrove-salt marsh ecotone, with unknown implications to coastal biogeochemical cycles. Here, we hypothesized that nitrogen and phosphorus cycling varied in mangrove and salt marsh, having significant implication on coastal waters. We investigated a tidal creek with a marked mangrove-salt marsh gradient in China using high-frequency time-series sampling of dissolved nutrients and observations of porewater exchange rate across the sediment-water interface over a spring-neap tidal cycle. The nitrogen transformation rates and microbiological activities were also investigated to explain the variability in nitrogen concentrations. The mangrove had net groundwater outflow rates of 3.6-4.3 mm d(-1) while the salt marsh had net infiltration of surface water with rates of 0.5-2.9 mm d(-1). Salt marsh had less capacity for ammonium (NH4-N) production (mineralization and dissimilatory nitrate reduction to ammonium DNRA) than mangrove. Denitrification dominated nitrogen removal reaching 97% and 83% in mangrove and salt marsh, respectively. Microbe distributions were consistent with nitrogen transformations with larger nirS and nrfA abundances for denitrification and DNRA in the mangrove than salt marsh. The mangrove had a net export of NH4-N but a net import of NOx-N (sum of nitrate and nitrite) and dissolved inorganic phosphorus (DIP) during the monitoring period. In contrast, the salt marsh had lower efflux of nutrient than influx leading to a net nutrient import during the monitoring period. Porewater released from the mangrove had a large DIN:DIP mole ratio (706 +/- 236) due to high NH4-N concentrations, while NH4-N in the salt marsh were lower than in the mangrove. Overall, this study revealed that mangrove-salt marsh ecotone will push the native mangrove wetlands from being a source towards a sink of NH4-N to coastal waters by decreasing porewater exchange, modifying the nutrients stoichiometry, and ultimately alleviating the potential of N-associated eutrophication in nearby coastal waters.
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50.
  • Wang, F. M., et al. (author)
  • Global blue carbon accumulation in tidal wetlands increases with climate change
  • 2021
  • In: National Science Review. - : Oxford University Press (OUP). - 2095-5138 .- 2053-714X. ; 8:9
  • Journal article (peer-reviewed)abstract
    • Coastal tidal wetlands produce and accumulate significant amounts of organic carbon (C) that help to mitigate climate change. However, previous data limitations have prevented a robust evaluation of the global rates and mechanisms driving C accumulation. Here, we go beyond recent soil C stock estimates to reveal global tidal wetland C accumulation and predict changes under relative sea level rise, temperature and precipitation. We use data from literature study sites and our new observations spanning wide latitudinal gradients and 20 countries. Globally, tidal wetlands accumulate 53.65 (95%CI: 48.52-59.01) Tg C yr(-1), which is similar to 30% of the organic C buried on the ocean floor. Modeling based on current climatic drivers and under projected emissions scenarios revealed a net increase in the global C accumulation by 2100. This rapid increase is driven by sea level rise in tidal marshes, and higher temperature and precipitation in mangroves. Countries with large areas of coastal wetlands, like Indonesia and Mexico, are more susceptible to tidal wetland C losses under climate change, while regions such as Australia, Brazil, the USA and China will experience a significant C accumulation increase under all projected scenarios.
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