ORCID Profile
0000-0003-3556-7616
Current Organisation
Nova Southeastern University
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Inorganic Geochemistry | Ecosystem Function | Geochemistry |
Physical and Chemical Conditions of Water in Marine Environments | Ecosystem Assessment and Management of Marine Environments
Publisher: Frontiers Media SA
Date: 23-09-2016
Publisher: American Geophysical Union (AGU)
Date: 04-2014
DOI: 10.1002/2013GB004598
Publisher: Wiley
Date: 20-12-2019
DOI: 10.1002/LOL2.10129
Abstract: Coral reefs are facing intensifying stressors, largely due to global increases in seawater temperature and decreases in pH. However, there is extensive environmental variability within coral reef ecosystems, which can impact how organisms respond to global trends. We deployed spatial arrays of autonomous sensors across distinct shallow coral reef habitats to determine patterns of spatiotemporal variability in seawater physicochemical parameters. Temperature and pH were positively correlated over the course of a day due to solar heating and light‐driven metabolism. The mean temporal and spatial ranges of temperature and pH were positively correlated across all sites, with different regimes of variability observed in different reef types. Ultimately, depth was a reliable predictor of the average diel ranges in both seawater temperature and pH. These results demonstrate that there is widespread environmental variability on diel timescales within coral reefs related to water column depth, which needs to be included in assessments of how global change will locally affect reef ecosystems.
Publisher: Cambridge University Press (CUP)
Date: 06-2014
Abstract: Empirical studies in economics traditionally use a limited range of methods, usually based on particular types of regression analysis. Increasingly, sophisticated regression techniques require the availability of appropriate data sets, often longitudinal and typically collected at a national level. This raises challenges for researchers seeking to investigate issues requiring data that are not typically included in regular large-scale data. It also raises questions of the adequacy of relying mainly or solely on regression analysis for investigating key issues of economic theory and policy. One way of addressing these issues is to employ a mixed-methods research framework to investigate important research questions. In this article, we provide an ex le of applying a mixed-methods design to investigate the employment decisions of mature age women working in the aged care sector. We outline the use of a coherent and robust framework to allow the integrated collection and analysis of quantitative and qualitative data. Drawing on particular ex les from our analysis, we show how a mixed-methods approach facilitates richer insights, more finely grained understandings of causal relationships and identification of emergent issues. We conclude that mixed-methods research has the capacity to provide surprises and generate new insights through detailed exploratory data analysis.
Publisher: American Geophysical Union (AGU)
Date: 08-2021
DOI: 10.1029/2021GL092534
Abstract: Methane (CH 4 ) and nitrous oxide (N 2 O) dynamics in coastal coral reef areas are poorly understood. We measured dissolved carbon dioxide (CO 2 ) and CH 4 (with δ 13 C‐CO 2 and δ 13 C‐CH 4 isotope fractions) and N 2 O in the Great Barrier Reef (GBR) to determine spatial distributions and emissions. CO 2 (379–589 μatm) was oversaturated due to calcification and riverine sources, as indicated by depleted δ 13 C‐CO 2 values. CH 4 (1.5–13.5 nM) was also oversaturated from nearshore biogenic sources indicated by depleted δ 13 C‐CH 4 and probable offshore aerobic production. N 2 O (5.5–6.6 nM) was generally undersaturated, with uptake highest near the coast. Daily CO 2 emissions were 5826 ± 1191 tonnes, with CO 2 equivalent ( eq ) N 2 O uptake (191 ± 44 tonnes) offsetting 3.3% of CO 2 or 89% of CH 4 eq (214 ± 45 tonnes) emissions based on 20‐year global warming potentials. The GBR was a slight CO 2 and CH 4 source and N 2 O sink during our study. However, further work is required to constrain diurnal, seasonal, and spatial dynamics.
Publisher: Public Library of Science (PLoS)
Date: 18-11-2014
Publisher: Frontiers Media SA
Date: 02-11-2017
Publisher: PeerJ
Date: 05-04-2022
DOI: 10.7717/PEERJ.13116
Abstract: Benthic incubation chambers facilitate in-situ metabolism studies in shallow water environments. They are used to isolate the water surrounding a study organism or community so that changes in water chemistry can be quantified to characterise physiological processes such as photosynthesis, respiration, and calcification. Such field measurements capture the biological processes taking place within the benthic community while incorporating the influence of environmental variables that are often difficult to recreate in ex-situ settings. Variations in benthic chamber designs have evolved for a range of applications. In this study, we built upon previous designs to create a novel chamber, which is (1) low-cost and assembled without specialised equipment, (2) easily reproducible, (3) minimally invasive, (4) adaptable to varied substrates, and (5) comparable with other available designs in performance. We tested the design in the laboratory and field and found that it achieved the outlined objectives. Using non-specialised materials, we were able to construct the chamber at a low cost (under $20 USD per unit), while maintaining similar performance and reproducibility with that of existing designs. Laboratory and field tests demonstrated minimal leakage (2.08 ± 0.78% water exchange over 4 h) and acceptable light transmission (86.9 ± 1.9%), results comparable to those reported for other chambers. In the field, chambers were deployed in a shallow coastal environment in Akumal, Mexico, to measure productivity of seagrass, and coral-, algae-, and sand-dominated reef patches. In both case studies, production rates aligned with those of comparable benthic chamber deployments in the literature and followed established trends with light, the primary driver of benthic metabolism, indicating robust performance under field conditions. We demonstrate that our low-cost benthic chamber design uses locally accessible and minimal resources, is adaptable for a variety of field settings, and can be used to collect reliable and repeatable benthic metabolism data. This chamber has the potential to broaden accessibility and applications of in-situ incubations for future studies.
Publisher: SAGE Publications
Date: 21-08-2013
Abstract: This article uses longitudinal data to measure the effects of ill health and informal care roles on the employment chances of mid-life women, and to examine how these effects are mediated by workplace characteristics. We find that women in jobs with lower skills/status encounter the greatest difficulty in finding accommodations for changes in their health and informal care roles. We identify an important role for paid sick leave and holiday leave in boosting employment retention. However, we find that the positive employment effects of permanent contracts do not extend to women experiencing increased informal care roles. Additionally, we do not identify a positive link between employment retention and flexible working time arrangements. However, we do establish a link between a preference for reduced working hours and employment cessation, suggesting that some women experience problems in achieving flexible working hours and that this causes some of them to leave work altogether. We argue that these findings are relevant to the design of policy initiatives aimed at lifting rates of workforce participation as part of the response to population ageing.
Publisher: Wiley
Date: 09-01-2021
DOI: 10.1002/LOM3.10410
Publisher: Wiley
Date: 21-08-2023
DOI: 10.1002/LOM3.10570
Abstract: Accurate measurements of seawater carbonate chemistry are crucial for marine carbon cycle research. Certified reference materials (CRMs) are typically analyzed alongside s les to correct measurements for calibration drift. However, the COVID‐19 pandemic led to a limited access to CRMs. In response to this shortage, we prepared and monitored in‐house reference materials (IHRMs) for total alkalinity (TA) and dissolved inorganic carbon (DIC), over 12 and 15 months, respectively. Overall, TA was stable, but a slight increase in DIC of about 2 μ mol kg −1 occurred over 15 months. The increase could potentially be attributed to bacterial growth, despite mercuric chloride fixation and repeated UV exposure. It is noted that this small increase was most likely within our instrument and measurements uncertainties. Our repeated measurements also identified a few bottles that had TA or DIC concentrations 4–5 μ mol kg −1 higher than the rest, indicating issues during cleaning, fixation, or storage of in idual bottles. This study emphasizes the importance of careful and continuous monitoring if self‐prepared IHRMs are used. Given that the amount of work required is very high, IHRM preparation is only recommended when CRMs are not available.
Publisher: Public Library of Science (PLoS)
Date: 09-01-2018
Publisher: American Geophysical Union (AGU)
Date: 21-04-2015
DOI: 10.1002/2015GL063126
Publisher: Elsevier BV
Date: 06-2020
Publisher: Springer Science and Business Media LLC
Date: 04-10-2021
Publisher: Elsevier BV
Date: 02-2022
Publisher: Oxford University Press (OUP)
Date: 13-12-2015
Publisher: American Geophysical Union (AGU)
Date: 05-08-2014
DOI: 10.1002/2014GL060849
Publisher: Frontiers Media SA
Date: 02-11-2016
Publisher: Elsevier BV
Date: 12-2016
Publisher: Elsevier BV
Date: 03-2015
Publisher: American Geophysical Union (AGU)
Date: 20-09-2013
DOI: 10.1002/GRL.50948
Publisher: Wiley
Date: 24-09-2019
DOI: 10.1002/LNO.11028
Publisher: Informa UK Limited
Date: 03-07-2014
Publisher: Springer Science and Business Media LLC
Date: 29-10-2014
DOI: 10.1038/NCLIMATE2380
Publisher: Copernicus GmbH
Date: 08-2022
Abstract: Abstract. Ocean alkalinity enhancement (OAE) is a method that can remove carbon dioxide (CO2) from the atmosphere and counteract ocean acidification through the dissolution of alkaline minerals. Currently, critical knowledge gaps exist regarding the dissolution of different minerals suitable for OAE in natural seawater. Of particular importance is to understand how much alkaline mineral can be dissolved before secondary precipitation of calcium carbonate (CaCO3) occurs, since secondary CaCO3 precipitation reduces the atmospheric CO2 uptake potential of OAE. Using two types of mineral proposed for OAE, quick lime (CaO) and hydrated lime (Ca(OH)2), we show that both ( µm of diameter) dissolved in seawater within a few hours. No CaCO3 precipitation occurred at a saturation state (ΩA) of ∼5, but CaCO3 precipitation in the form of aragonite occurred above an ΩA value of 7. This limit is lower than expected for typical pseudo-homogeneous precipitation, i.e. in the presence of colloids and organic matter. Secondary precipitation at low ΩA (∼ 7) was the result of heterogeneous precipitation onto mineral surfaces, most likely onto the added CaO and Ca(OH)2 particles. Most importantly, runaway CaCO3 precipitation was observed, a condition where significantly more total alkalinity (TA) was removed than initially added. Such runaway precipitation could reduce the OAE CO2 uptake efficiency from ∼ 0.8 mol of CO2 per mole of added TA down to 0.1 mol of CO2 per mole of TA. Runaway precipitation appears to be avoidable by dilution below the critical ΩA threshold of 5, ideally within hours of the mineral additions to minimise initial CaCO3 precipitation. Finally, OAE simulations suggest that for the same ΩA threshold, the amount of TA that can be added to seawater would be more than 3 times higher at 5 ∘C than at 30 ∘C. The maximum TA addition could also be increased by equilibrating the seawater to atmospheric CO2 levels (i.e. to a pCO2 of ∼ 416 µatm) during addition. This would allow for more TA to be added in seawater without inducing CaCO3 precipitation, using OAE at its CO2 removal potential.
Publisher: Copernicus GmbH
Date: 15-04-2013
Abstract: Abstract. To better predict how ocean acidification will affect coral reefs, it is important to understand how biogeochemical cycles on reefs alter carbonate chemistry over various temporal and spatial scales. This study quantifies the contribution of shallow porewater exchange (as quantified from advective chamber incubations) and fresh groundwater discharge (as traced by 222Rn) to total alkalinity (TA) dynamics on a fringing coral reef lagoon along the southern Pacific island of Rarotonga over a tidal and diel cycle. Benthic alkalinity fluxes were affected by the advective circulation of water through permeable sediments, with net daily flux rates of carbonate alkalinity ranging from −1.55 to 7.76 mmol m−2 d−1, depending on the advection rate. Submarine groundwater discharge (SGD) was a source of TA to the lagoon, with the highest flux rates measured at low tide, and an average daily TA flux of 1080 mmol m−2 d−1 at the s ling site. Both sources of TA were important on a reef-wide basis, although SGD acted solely as a delivery mechanism of TA to the lagoon, while porewater advection was either a sink or source of TA dependent on the time of day. This study describes overlooked sources of TA to coral reef ecosystems that can potentially alter water column carbonate chemistry. We suggest that porewater and groundwater fluxes of TA should be taken into account in ocean acidification models in order to properly address changing carbonate chemistry within coral reef ecosystems.
Publisher: Springer Science and Business Media LLC
Date: 16-03-2023
Publisher: Springer Science and Business Media LLC
Date: 26-10-2022
DOI: 10.1038/S41598-022-21831-Y
Abstract: The California Current System experiences seasonal ocean acidification and hypoxia (OAH) owing to wind-driven upwelling, but little is known about the intensity, frequency, and depth distribution of OAH in the shallow nearshore environment. Here we present observations of OAH and dissolved inorganic carbon and nutrient parameters based on monthly transects from March 2017 to September 2018 extending from the surf zone to the ~ 40 m depth contour in La Jolla, California. Biologically concerning OAH conditions were observed at depths as shallow as 10 m and as close as 700 m to the shoreline. Below 20 m depth, 8% of observations were undersaturated with respect to aragonite, 28% of observations had a pH T less than 7.85, and 19% of observations were below the sublethal oxygen threshold of 157 µmol kg −1 . These observations raise important questions about the impacts of OAH on coastal organisms and ecosystems and how future intensified upwelling may exacerbate these conditions.
Publisher: Wiley
Date: 07-12-2015
DOI: 10.1111/JPY.12364
Abstract: Various life cycle stages of cyst-producing dinoflagellates often appear differently colored under the microscope gametes appear paler while zygotes are darker in comparison to vegetative cells. To compare physiological and photochemical competency, the pigment composition of discrete life cycle stages was determined for the common resting cyst-producing dinoflagellate Scrippsiella lachrymosa. Vegetative cells had the highest cellular pigment content (25.2 ± 0.5 pg · cell(-1) ), whereas gamete pigment content was 22% lower. The pigment content of zygotes was 82% lower than vegetative cells, even though they appeared darker under the microscope. Zygotes of S. lachrymosa contained significantly higher cellular concentrations of β-carotene (0.65 ± 0.15 pg · cell(-1) ) than all other life stages. Photoprotective pigments and the de-epoxidation ratio of xanthophylls-cycle pigments in S. lachrymosa were significantly elevated in zygotes and cysts compared to other stages. This suggests a role for accessory pigments in combating intracellular oxidative stress during sexual reproduction or encystment. Resting cysts contained some pigments even though chloroplasts were not visible, suggesting that the brightly colored accumulation body contained photosynthetic pigments. The differences in pigmentation between life stages have implications for interpretation of pigment data from field s les when s led during dinoflagellate blooms.
Publisher: Elsevier BV
Date: 07-2016
Publisher: Oxford University Press (OUP)
Date: 21-05-2015
Abstract: The literature on ocean acidification (OA) contains a prevalent misconception that reduced organismal calcification rates in an acidifying ocean are driven by a reduction in carbonate ion (CO32−) substrate availability (e.g. Omega or Ω). However, recent research in erse organisms suggests that a reduction in seawater pH (i.e. increasing proton concentrations, [H+]) is the most likely driver of reduced calcification rates in these organisms. OA leads to higher [H+] in seawater which alters the proton gradient between internal cellular reservoirs and external bulk seawater, making it difficult for organisms to maintain pH homeostasis. Biologically mediated calcification is a complex process, so it is unlikely that simple CO32− substrate limitation is responsible for the observed decreases in calcification rates under OA conditions. Despite these inherent complexities, current predictions concerning the fate of calcifying organisms in an acidifying ocean have relied on the relationship between calcification rates and Ω. To more accurately predict how OA will affect the calcification of marine organisms, and consequently the global carbon cycle, we need to further elucidate the mechanisms driving observed decreases in calcification under acidified conditions.
Publisher: Public Library of Science (PLoS)
Date: 29-12-2021
DOI: 10.1371/JOURNAL.PONE.0261210
Abstract: Salinity normalization of total alkalinity (TA) and dissolved inorganic carbon (DIC) data is commonly used to account for conservative mixing processes when inferring net metabolic modification of seawater by coral reefs. Salinity (S), TA, and DIC can be accurately and precisely measured, but salinity normalization of TA (nTA) and DIC (nDIC) can generate considerable and unrecognized uncertainties in coral reef metabolic rate estimates. While salinity normalization errors apply to nTA, nDIC, and other ions of interest in coral reefs, here, we focus on nTA due to its application as a proxy for net coral reef calcification and the importance for reefs to maintain calcium carbonate production under environmental change. We used global datasets of coral reef TA, S, and modeled groundwater discharge to assess the effect of different volumetric ratios of multiple freshwater TA inputs (i.e., groundwater, river, surface runoff, and precipitation) on nTA. Coral reef freshwater endmember TA ranged from -2 up to 3032 μmol/kg in hypothetical reef locations with freshwater inputs dominated by riverine, surface runoff, or precipitation mixing with groundwater. The upper bound of freshwater TA in these scenarios can result in an uncertainty in reef TA of up to 90 μmol/kg per unit S normalization if the freshwater endmember is erroneously assumed to have 0 μmol/kg alkalinity. The uncertainty associated with S normalization can, under some circumstances, even shift the interpretation of whether reefs are net calcifying to net dissolving, or vice versa. Moreover, the choice of reference salinity for normalization implicitly makes assumptions about whether biogeochemical processes occur before or after mixing between different water masses, which can add uncertainties of ±1.4% nTA per unit S normalization. Additional considerations in identifying potential freshwater sources of TA and their relative volumetric impact on seawater are required to reduce uncertainties associated with S normalization of coral reef carbonate chemistry data in some environments. However, at a minimum, researchers should minimize the range of salinities over which the normalization is applied, precisely measure salinity, and normalize TA values to a carefully selected reference salinity that takes local factors into account.
Publisher: American Chemical Society (ACS)
Date: 18-03-2013
DOI: 10.1021/ES304538G
Publisher: MDPI AG
Date: 24-02-2021
DOI: 10.3390/RS13050841
Abstract: The accuracy and precision of satellite sea surface temperature (SST) products in nearshore coastal waters are not well known, owing to a lack of in-situ data available for validation. It has been suggested that recreational watersports enthusiasts, who immerse themselves in nearshore coastal waters, be used as a platform to improve s ling and fill this gap. One tool that has been used worldwide by surfers is the Smartfin, which contains a temperature sensor integrated into a surfboard fin. If tools such as the Smartfin are to be considered for satellite validation work, they must be carefully evaluated against state-of-the-art techniques to quantify data quality. In this study, we developed a Simple Oceanographic floating Device (SOD), designed to float on the ocean surface, and deployed it during the 28th Atlantic Meridional Transect (AMT28) research cruise (September and October 2018). We attached a Smartfin to the underside of the SOD, which measured temperature at a depth of ∼0.1 m, in a manner consistent with how it collects data on a surfboard. Additional temperature sensors (an iButton and a TidbiT v2), shaded and positioned a depth of ∼1 m, were also attached to the SOD at some of the stations. Four laboratory comparisons of the SOD sensors (Smartfin, iButton and TidbiT v2) with an accurate temperature probe (±0.0043 K over a range of 273.15 to 323.15 K) were also conducted during the AMT28 voyage, over a temperature range of 290–309 K in a recirculating water bath. Mean differences (δ), referenced to the temperature probe, were removed from the iButton (δ=0.292 K) and a TidbiT v2 sensors (δ=0.089 K), but not from the Smartfin, as it was found to be in excellent agreement with the temperature probe (δ=0.005 K). The SOD was deployed for 20 min periods at 62 stations (predawn and noon) spanning 100 degrees latitude and a gradient in SST of 19 K. Simultaneous measurements of skin SST were collected using an Infrared Sea surface temperature Autonomous Radiometer (ISAR), a state-of-the-art instrument used for satellite validation. Additionally, we extracted simultaneous SST measurements, collected at slightly different depths, from an underway conductivity, temperature and depth (CTD) system. Over all 62 stations, the mean difference (δ) and mean absolute difference (ϵ) between Smartfin and the underway CTD were −0.01 and 0.06 K respectively (similar results obtained from comparisons between Smartfin and iButton and Smartfin and TidbiT v2), and the δ and ϵ between Smartfin and ISAR were 0.09 and 0.12 K respectively. In both comparisons, statistics varied between noon and predawn stations, with differences related to environmental variability (wind speed and sea-air temperature differences) and depth of s ling. Our results add confidence to the use of Smartfin as a citizen science tool for evaluating satellite SST data, and data collected using the SOD and ISAR were shown to be useful for quantifying near-surface temperature gradients.
Publisher: Springer Science and Business Media LLC
Date: 06-12-2017
Publisher: Elsevier BV
Date: 09-2018
Publisher: Wiley
Date: 30-07-2019
DOI: 10.1111/GCB.14730
Abstract: Climate change refugia in the terrestrial biosphere are areas where species are protected from global environmental change and arise from natural heterogeneity in landscapes and climate. Within the marine realm, ocean acidification, or the global decline in seawater pH, remains a pervasive threat to organisms and ecosystems. Natural variability in seawater carbon dioxide (CO 2 ) chemistry, however, presents an opportunity to identify ocean acidification refugia (OAR) for marine species. Here, we review the literature to examine the impacts of variable CO 2 chemistry on biological responses to ocean acidification and develop a framework of definitions and criteria that connects current OAR research to management goals. Under the concept of managing vulnerability, the most likely mechanisms by which OAR can mitigate ocean acidification impacts are by reducing exposure to harmful conditions or enhancing adaptive capacity. While local management options, such as OAR, show some promise, they present unique challenges, and reducing global anthropogenic CO 2 emissions must remain a priority.
Publisher: Wiley
Date: 20-11-2019
DOI: 10.1002/LNO.11357
Publisher: Springer Science and Business Media LLC
Date: 03-01-2018
Publisher: Copernicus GmbH
Date: 30-10-2014
Publisher: Wiley
Date: 08-01-2022
DOI: 10.1002/LNO.12002
Abstract: Coral reef metabolism underpins ecosystem function and is defined by the processes of photosynthesis, respiration, calcification, and calcium carbonate dissolution. However, the relationships between these physiological processes at the organismal level and their interactions with light remain unclear. We examined metabolic rates across a range of photosynthesising calcifiers in the Caribbean: the scleractinian corals Acropora cervicornis , Orbicella faveolata , Porites astreoides , and Siderastrea siderea , and crustose coralline algae (CCA) under varying natural light conditions. Net photosynthesis and calcification showed a parabolic response to light across all species, with differences among massive corals, branching corals, and CCA that reflect their relative functional roles on the reef. At night, all organisms were net respiring, and most were net calcifying, although some incubations demonstrated instances of net calcium carbonate (CaCO 3 ) dissolution. Peak metabolic rates at light‐saturation (maximum photosynthesis and calcification) and average dark rates (respiration and dark calcification) were positively correlated across species. Interspecies relationships among photosynthesis, respiration, and calcification indicate that calcification rates are linked to energy production at the organismal level in calcifying reef organisms. The species‐specific ratios of net calcification to photosynthesis varied with light over a diurnal cycle. The dynamic nature of calcification hotosynthesis ratios over a diurnal cycle questions the use of this metric as an indicator for reef function and health at the ecosystem scale unless temporal variability is accounted for, and a new metric is proposed. The complex light‐driven dynamics of metabolic processes in coral reef organisms indicate that a more comprehensive understanding of reef metabolism is needed for predicting the future impacts of global change.
Publisher: American Association for the Advancement of Science (AAAS)
Date: 23-02-2018
Abstract: The uptake of anthropogenic carbon dioxide from the atmosphere is reducing the pH of the oceans. Ocean acidification means that calcium carbonate—the material with which coral reefs are built—will be more difficult for organisms to generate and will dissolve more quickly. Eyre et al. report that some reefs are already experiencing net sediment dissolution. Worryingly, the rates of loss will increase as ocean acidification intensifies. Science , this issue p. 908
Publisher: Wiley
Date: 17-10-2012
DOI: 10.1111/J.1741-6612.2012.00599.X
Abstract: To provide new measures of employee retention in the aged care sector and to identify how employment retention varies across key groups of workers in the sector. The techniques of survival analysis were applied to staff record data from a representative provider of aged and community care services. We showed that 63% of carer employment spells end within 2 years. Fifty-seven per cent of nurse employment spells ended within this time period. Employment retention was poorest among young recruits, men and workers on casual contracts. The high rates of staff turnover add substantial costs and risks to aged care organisations and should be the focus of workforce strategies. Casual employment is one potential contributory factor. However, the role of wages and other working conditions should also be examined. Given the importance of mature-age women in the sector, strategies should focus on their circumstances and needs.
Publisher: Elsevier BV
Date: 11-2014
Publisher: Informa UK Limited
Date: 09-05-2014
Publisher: Frontiers Media SA
Date: 22-05-2018
Publisher: Copernicus GmbH
Date: 27-06-2023
DOI: 10.5194/SP-2023-9
Abstract: Abstract. This chapter focuses on considerations for conducting open-system field experiments in the context of ocean alkalinity enhancement (OAE) research. By conducting experiments in real-world marine systems, researchers can gain valuable insights into ecological dynamics, biogeochemical cycles, and the safety, efficacy, and scalability of OAE techniques under natural conditions. However, logistical constraints and complex natural dynamics pose challenges for successful field trials. To date, only a limited number of OAE field studies have been conducted, and guidelines for such experiments are still evolving. Due to the fast pace of carbon dioxide removal (CDR) research and development, we advocate for openly sharing knowledge and lessons learned as quickly as possible within the broader OAE community and beyond. Considering the potential ecological and societal consequences of field experiments, active engagement with the public and other stakeholders is essential. Collaboration, data sharing, and transdisciplinary teams are vital for maximizing the return on investment during field trials. The outcomes of early field deployments are likely to shape the future of OAE, emphasizing the need for transparent and open scientific practices.
Publisher: American Geophysical Union (AGU)
Date: 10-09-2013
DOI: 10.1002/GRL.50802
Publisher: Wiley
Date: 17-03-2021
DOI: 10.1002/LNO.11722
Publisher: Springer Science and Business Media LLC
Date: 16-05-2020
DOI: 10.1007/S10498-020-09378-8
Abstract: Seagrass systems are integral components of both local and global carbon cycles and can substantially modify seawater biogeochemistry, which has ecological ramifications. However, the influence of seagrass on porewater biogeochemistry has not been fully described, and the exact role of this marine macrophyte and associated microbial communities in the modification of porewater chemistry remains equivocal. In the present study, carbonate chemistry in the water column and porewater was investigated over diel timescales in contrasting, tidally influenced seagrass systems in Southern California and Bermuda, including vegetated ( Zostera marina ) and unvegetated biomes (0–16 cm) in Mission Bay, San Diego, USA and a vegetated system ( Thallasia testudinium ) in Mangrove Bay, Ferry Reach, Bermuda. In Mission Bay, dissolved inorganic carbon (DIC) and total alkalinity (TA) exhibited strong increasing gradients with sediment depth. Vertical porewater profiles differed between the sites, with almost twice as high concentrations of DIC and TA observed in the vegetated compared to the unvegetated sediments. In Mangrove Bay, both the range and vertical profiles of porewater carbonate parameters such as DIC and TA were much lower and, in contrast to Mission Bay where no distinct temporal signal was observed, biogeochemical parameters followed the semi-diurnal tidal signal in the water column. The observed differences between the study sites most likely reflect a differential influence of biological (biomass, detritus and infauna) and physical processes (e.g., sediment permeability, residence time and mixing) on porewater carbonate chemistry in the different settings.
Publisher: American Geophysical Union (AGU)
Date: 19-03-2021
DOI: 10.1029/2020GL090811
Abstract: There are concerns that reefs will transition from net calcifying to net dissolving in the near future due to decreasing calcification and increasing dissolution rates. Here, we present in situ rates of net ecosystem calcification (NEC) and net ecosystem production (NEP) on a coral reef flat using a slack‐water approach. Up until dusk, the reef was net calcifying in most months but shifted to net dissolution in austral summer, coinciding with high respiration rates and a lower aragonite saturation state (Ω arag ). The estimated sediment contribution to NEC ranged from 8% to 21% during the day and 45% to 78% at night, indicating that high rates of sediment dissolution may cause the transition to reef dissolution. This late afternoon seasonal transition to negative NEC may be an early warning sign of the reef shifting to a net dissolving state and may be occurring on other reefs.
Publisher: Wiley
Date: 25-11-2012
Publisher: Copernicus GmbH
Date: 10-12-2021
DOI: 10.5194/BG-2021-330
Abstract: Abstract. Ocean Alkalinity Enhancement (OAE) has been proposed as a method to remove carbon dioxide (CO2) from the atmosphere and to counteract ocean acidification. It involves the dissolution of alkaline minerals such as quick lime, CaO, and hydrated lime, Ca(OH)2. However, a critical knowledge gap exists regarding their dissolution in natural seawater. Particularly, how much can be dissolved before secondary precipitation of calcium carbonate (CaCO3) occurs is yet to be established. Secondary precipitation should be avoided as it reduces the atmospheric CO2 uptake potential of OAE. Here we show that both CaO and Ca(OH)2 powders ( 63 µm of diameter) dissolved in seawater within a few hours. However, CaCO3 precipitation, in the form of aragonite, occurred at a saturation (ΩAr) threshold of about 5. This limit is much lower than what would be expected for typical pseudo-homogeneous precipitation in the presence of colloids and organic materials. Secondary precipitation at unexpectedly low ΩAr was the result of so-called heterogeneous precipitation onto mineral phases, most likely onto CaO and Ca(OH)2 prior to full dissolution. Most importantly, this led to runaway CaCO3 precipitation by which significantly more alkalinity (TA) was removed than initially added, until ΩAr reached levels below 2. Such runaway precipitation would reduce the CO2 uptake efficiency from about 0.8 moles of CO2 per mole of TA down to only 0.1 mole of CO2 per mole of TA. Runaway precipitation appears to be avoidable by dilution below the critical ΩAr threshold of 5, ideally within hours of the addition to minimise initial CaCO3 precipitation. Finally, model considerations suggest that for the same ΩAr threshold, the amount of TA that can be added to seawater would be more than three times higher at 5 °C than at 30 °C, and that equilibration to atmospheric CO2 levels during mineral dissolution would further increase it by a factor of ~6 and ~3 respectively.
Publisher: Elsevier BV
Date: 06-2022
Location: United States of America
Location: United States of America
Start Date: 06-2023
End Date: 12-2026
Amount: $437,000.00
Funder: Australian Research Council
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