46 results on '"Kennedy, Hilary"'
Search Results
2. Integrating blue: How do we make nationally determined contributions work for both blue carbon and local coastal communities?
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Dencer-Brown, Amrit Melissa, Shilland, Robyn, Friess, Daniel, Herr, Dorothée, Benson, Lisa, Berry, Nicholas J., Cifuentes-Jara, Miguel, Colas, Patrick, Damayanti, Ellyn, García, Elisa López, Gavaldão, Marina, Grimsditch, Gabriel, Hejnowicz, Adam P., Howard, Jennifer, Islam, Sheikh Tawhidul, Kennedy, Hilary, Kivugo, Rahma Rashid, Lang’at, Joseph K. S., Lovelock, Catherine, Malleson, Ruth, Macreadie, Peter I., Andrade-Medina, Rosalía, Mohamed, Ahmed, Pidgeon, Emily, Ramos, Jorge, Rosette, Minerva, Salim, Mwanarusi Mwafrica, Schoof, Eva, Talukder, Byomkesh, Thomas, Tamara, Vanderklift, Mathew A., and Huxham, Mark
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- 2022
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3. Characterization of meta-Cresol Purple for spectrophotometric pH measurements in saline and hypersaline media at sub-zero temperatures.
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Loucaides, Socratis, Rèrolle, Victoire MC, Papadimitriou, Stathys, Kennedy, Hilary, Mowlem, Matthew C, Dickson, Andrew G, Gledhill, Martha, and Achterberg, Eric P
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Accurate pH measurements in polar waters and sea ice brines require pH indicator dyes characterized at near-zero and below-zero temperatures and high salinities. We present experimentally determined physical and chemical characteristics of purified meta-Cresol Purple (mCP) pH indicator dye suitable for pH measurements in seawater and conservative seawater-derived brines at salinities (S) between 35 and 100 and temperatures (T) between their freezing point and 298.15 K (25 °C). Within this temperature and salinity range, using purified mCP and a novel thermostated spectrophotometric device, the pH on the total scale (pHT) can be calculated from direct measurements of the absorbance ratio R of the dye in natural samples as[Formula: see text] Based on the mCP characterization in these extended conditions, the temperature and salinity dependence of the molar absorptivity ratios and - [Formula: see text] of purified mCP is described by the following functions: e 1 = -0.004363 + 3.598 × 10-5 T, e 3/e 2 = -0.016224 + 2.42851 × 10-4 T + 5.05663 × 10-5(S - 35), and - [Formula: see text] = -319.8369 + 0.688159 S -0.00018374 S 2 + (10508.724 - 32.9599 S + 0.059082S 2) T-1 + (55.54253 - 0.101639 S) ln T -0.08112151T. This work takes the characterisation of mCP beyond the currently available ranges of 278.15 K ≤ T ≤ 308.15 K and 20 ≤ S ≤ 40 in natural seawater, thereby allowing high quality pHT measurements in polar systems.
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- 2017
4. Losses of Soil Organic Carbon with Deforestation in Mangroves of Madagascar
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Arias-Ortiz, Ariane, Masqué, Pere, Glass, Leah, Benson, Lisa, Kennedy, Hilary, Duarte, Carlos M., Garcia-Orellana, Jordi, Benitez-Nelson, Claudia R., Humphries, Marc S., Ratefinjanahary, Ismaël, Ravelonjatovo, Jaona, and Lovelock, Catherine E.
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- 2021
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5. One hundred priority questions for advancing seagrass conservation in Europe.
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Nordlund, Lina Mtwana, Unsworth, Richard K. F., Wallner‐Hahn, Sieglind, Ratnarajah, Lavenia, Beca‐Carretero, Pedro, Boikova, Elmira, Bull, James C., Chefaoui, Rosa M., de los Santos, Carmen B., Gagnon, Karine, Garmendia, Joxe Mikel, Gizzi, Francesca, Govers, Laura L., Gustafsson, Camilla, Hineva, Elitsa, Infantes, Eduardo, Canning‐Clode, João, Jahnke, Marlene, Kleitou, Periklis, and Kennedy, Hilary
- Abstract
Societal Impact Statement: Seagrass ecosystems are of fundamental importance to our planet and wellbeing. Seagrasses are marine flowering plants, which engineer ecosystems that provide a multitude of ecosystem services, for example, blue foods and carbon sequestration. Seagrass ecosystems have largely been degraded across much of their global range. There is now increasing interest in the conservation and restoration of these systems, particularly in the context of the climate emergency and the biodiversity crisis. The collation of 100 questions from experts across Europe could, if answered, improve our ability to conserve and restore these systems by facilitating a fundamental shift in the success of such work. Summary: Seagrass meadows provide numerous ecosystem services including biodiversity, coastal protection, and carbon sequestration. In Europe, seagrasses can be found in shallow sheltered waters along coastlines, in estuaries & lagoons, and around islands, but their distribution has declined. Factors such as poor water quality, coastal modification, mechanical damage, overfishing, land‐sea interactions, climate change and disease have reduced the coverage of Europe's seagrasses necessitating their recovery. Research, monitoring and conservation efforts on seagrass ecosystems in Europe are mostly uncoordinated and biased towards certain species and regions, resulting in inadequate delivery of critical information for their management. Here, we aim to identify the 100 priority questions, that if addressed would strongly advance seagrass monitoring, research and conservation in Europe. Using a Delphi method, researchers, practitioners, and policymakers with seagrass experience from across Europe and with diverse seagrass expertise participated in the process that involved the formulation of research questions, a voting process and an online workshop to identify the final list of the 100 questions. The final list of questions covers areas across nine themes: Biodiversity & Ecology; Ecosystem services; Blue carbon; Fishery support; Drivers, Threats, Resilience & Response; Monitoring & Assessment; Conservation & Restoration; Governance, Policy & Management; and Communication. Answering these questions will fill current knowledge gaps and place European seagrass onto a positive trajectory of recovery. [ABSTRACT FROM AUTHOR]
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- 2024
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6. Temporal and Spatial Variation of Sulfide Invasion in Eelgrass (Zostera marina) as Reflected by Its Sulfur Isotopic Composition
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Frederiksen, Morten S., Holmer, Marianne, Borum, Jens, and Kennedy, Hilary
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- 2006
7. Community Metabolism and Carbon Budget along a Gradient of Seagrass (Cymodocea nodosa) Colonization
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Barrón, Cristina, Marbà, Núria, Terrados, Jorge, Kennedy, Hilary, and Duarte, Carlos M.
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- 2004
8. Dynamics of estuarine drift macroalgae : growth cycles and contributions to sediments in shallow areas
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Lanari, Marianna, Kennedy, Hilary, Copertino, Margareth S., Wallner-Kersanach, Mônica, and Claudino, Marlucy Coelho
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- 2017
9. On the Relative Constancy of Iodate and Total-Iodine Concentrations Accompanying Phytoplankton Blooms Initiated in Mesocosm Experiments in Antarctica
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Truesdale, Victor W., Kennedy, Hilary, Agustí, Susana, and Waite, Tim J.
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- 2003
10. Climate action requires new accounting guidance and governance frameworks to manage carbon in shelf seas
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Luisetti, Tiziana, Ferrini, Silvia, Grilli, Gaetano, Jickells, Timothy D., Kennedy, Hilary, Kröger, Silke, Lorenzoni, Irene, Milligan, Ben, van der Molen, Johan, Parker, Ruth, Pryce, Tim, Turner, R. Kerry, and Tyllianakis, Emmanouil
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- 2020
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11. Author Correction: The future of Blue Carbon science
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Macreadie, Peter I., Anton, Andrea, Raven, John A., Beaumont, Nicola, Connolly, Rod M., Friess, Daniel A., Kelleway, Jeffrey J., Kennedy, Hilary, Kuwae, Tomohiro, Lavery, Paul S., Lovelock, Catherine E., Smale, Dan A., Apostolaki, Eugenia T., Atwood, Trisha B., Baldock, Jeff, Bianchi, Thomas S., Chmura, Gail L., Eyre, Bradley D., Fourqurean, James W., Hall-Spencer, Jason M., Huxham, Mark, Hendriks, Iris E., Krause-Jensen, Dorte, Laffoley, Dan, Luisetti, Tiziana, Marbà, Núria, Masque, Pere, McGlathery, Karen J., Megonigal, J. Patrick, Murdiyarso, Daniel, Russell, Bayden D., Santos, Rui, Serrano, Oscar, Silliman, Brian R., Watanabe, Kenta, and Duarte, Carlos M.
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- 2019
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12. The future of Blue Carbon science
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Macreadie, Peter I., Anton, Andrea, Raven, John A., Beaumont, Nicola, Connolly, Rod M., Friess, Daniel A., Kelleway, Jeffrey J., Kennedy, Hilary, Kuwae, Tomohiro, Lavery, Paul S., Lovelock, Catherine E., Smale, Dan A., Apostolaki, Eugenia T., Atwood, Trisha B., Baldock, Jeff, Bianchi, Thomas S., Chmura, Gail L., Eyre, Bradley D., Fourqurean, James W., Hall-Spencer, Jason M., Huxham, Mark, Hendriks, Iris E., Krause-Jensen, Dorte, Laffoley, Dan, Luisetti, Tiziana, Marbà, Núria, Masque, Pere, McGlathery, Karen J., Megonigal, J. Patrick, Murdiyarso, Daniel, Russell, Bayden D., Santos, Rui, Serrano, Oscar, Silliman, Brian R., Watanabe, Kenta, and Duarte, Carlos M.
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- 2019
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13. Shifts in the phytoplankton community in response to zinc and iron enrichments in the north-eastern subarctic Pacific
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Crawford, D.W., Purdie, Duncan, Lohan, Maeve Carroll, Statham, Peter John, Peterson, Tawnya D., Kennedy, Hilary A., Lipsen, Michael S., Putland, Jennifer N., and Whitney, Frank A.
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The offshore Gulf of Alaska—in the north-eastern subarctic Pacific—is a high nitrate, low chlorophyll (HNLC) oceanic region where concentrations of dissolved iron (DFe) and zinc (DZn) are of the order ~0.1 nmol kg-1 in surface waters. At the average winter mixed layer depth of ~120 m, concentrations of DFe and DZn are of the orders ~0.1–0.2 nmol kg-1 and ~1–2 nmol kg-1 respectively. Vertical supply of Fe to surface waters is therefore limited, with phytoplankton blooms driven by episodic inputs of Fe. In contrast, DZn is presumably replenished through seasonal vertical mixing, though maintained at low levels in surface waters, even in winter, implying that removal processes are in operation.Previous supplementation experiments have demonstrated that phytoplankton biomass (chl-a) and growth, and drawdown of nitrate (NO3-), are stimulated strongly by Fe but only minimally, if at all, by Zn alone. Using on-deck bioassay incubations of surface waters, we confirm that addition of Fe stimulates significant increases in chl-a and large diatoms, and drawdown of NO3-and silicic acid (Si(OH)4). Associated drawdown of DZn and dissolved cadmium (DCd) indicated Zn stress in control and +Fe treatments. Supplementation with Zn alone had no significant impact on dissolved NO3- and commonly monitored pigments such as chl-a and fucoxanthin. However, in +Zn treatments, DFe and coccolithophore abundance were significantly lower, and the concentration of particulate organic carbon (POC) and the pigments alloxanthin and chlorophyll c1+2 were significantly higher than in control incubations. Our experiment corroborates previously observed relationships between DZn and alloxanthin and chlorophyll c across the subarctic north Pacific and Bering Sea and could help to explain the low or undetectable concentrations of alloxanthin frequently observed in this region. Alloxanthin is a pigment specific to the cryptophytes, either within free-living cells, or within functional plastids retained by mixotrophic protists. Both cryptophytes and mixotrophic ciliates, such as Laboea sp. and Stombidium spp., make a variable but significant contribution to phytoplankton biomass in this area. In the absence of Fe supply to surface waters, Zn could play a hitherto unsuspected role in shaping plankton communities in the HNLC Gulf of Alaska.
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- 2022
14. Apparent shifts in the microplankton community in response to zinc and iron enrichments in the Northeastern Subarctic Pacific
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Crawford, David W., primary, Purdie, Duncan A., additional, Lohan, Maeve C., additional, Statham, Peter J., additional, Peterson, Tawnya D., additional, Kennedy, Hilary A., additional, Lipsen, Michael S., additional, Putland, Jennifer N., additional, and Whitney, Frank A., additional
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- 2022
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15. Operationalizing marketable blue carbon
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Macreadie, Peter I., primary, Robertson, Alistar I., additional, Spinks, Bernadette, additional, Adams, Matthew P., additional, Atchison, Jennifer M., additional, Bell-James, Justine, additional, Bryan, Brett A., additional, Chu, Long, additional, Filbee-Dexter, Karen, additional, Drake, Lauren, additional, Duarte, Carlos M., additional, Friess, Daniel A., additional, Gonzalez, Felipe, additional, Grafton, R. Quentin, additional, Helmstedt, Kate J., additional, Kaebernick, Melanie, additional, Kelleway, Jeffrey, additional, Kendrick, Gary A., additional, Kennedy, Hilary, additional, Lovelock, Catherine E., additional, Megonigal, J. Patrick, additional, Maher, Damien T., additional, Pidgeon, Emily, additional, Rogers, Abbie A., additional, Sturgiss, Rob, additional, Trevathan-Tackett, Stacey M., additional, Wartman, Melissa, additional, Wilson, Kerrie A., additional, and Rogers, Kerrylee, additional
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- 2022
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16. Species traits and geomorphic setting as drivers of global soil carbon stocks in seagrass meadows
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Kennedy, Hilary, Pagès, Jordi, Lagomasino, D., Arias Ortiz, Ariane, Colarusso, Phil, Fourqurean, James, Githaiga, M. N., Howard, J. L., Krause-Jensen, D., Kuwae, Tomohiro, Lavery, Paul S, Macreadie, P. I., Marbà, Núria, Masqué Barri, Pere, Mazarrasa, Inés, Miyajima, Toshihiro, Serrano, Oscar, Duarte, Carlos M., and Universitat Autònoma de Barcelona. Departament de Física
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Atmospheric Science ,Global and Planetary Change ,vegetated coastal ecosystems ,blue carbon ,Environmental Chemistry ,seagrass meadows ,carbon storage ,ecosystem services ,General Environmental Science - Abstract
Este artículo contiene 18 páginas, 6 figuras, 1 tabla., Our knowledge of the factors that can influence the stock of organic carbon (OC) that is stored in the soil of seagrass meadows is evolving, and several causal effects have been used to explain the variation of stocks observed at local to national scales. To gain a global-scale appreciation of the drivers that cause variation in soil OC stocks, we compiled data on published species-specific traits and OC stocks from monospecific and mixed meadows at multiple geomorphological settings. Species identity was recognized as an influential driver of soil OC stocks, despite their large intraspecific variation. The most important seagrass species traits associated with OC stocks were the number of leaves per seagrass shoot, belowground biomass, leaf lifespan, aboveground biomass, leaf lignin, leaf breaking force and leaf OC plus the coastal geomorphology of the area, particularly for lagoon environments. A revised estimate of the global average soil OC stock to 20 cm depth of 15.4 Mg C ha −1 is lower than previously reported. The largest stocks were still recorded in Mediterranean seagrass meadows. Our results specifically identify Posidonia oceanica from the Mediterranean and, more generally, large and persistent species as key in providing climate regulation services, and as priority species for conservation for this specific ecosystem service., HK was supported by the Ecosystem Services for Poverty Alleviation program Coastal Ecosystem Services in East Africa (NE/L001535/1). JFP acknowledges financial support from the European Union's Horizon 2020 research and innovation programme under the Marie Skłodowska-Curie Grant 795315. JWF and JLH were supported by the Florida Coastal Everglades Long-Term Ecological Research program under the U.S. National Science Foundation Grant DEB-2025954, and this paper is contribution #1494 from the Institute of Environment at Florida International University. TK was supported in part by Grants-in-Aid for Scientific Research (KAKENHI) Grant 18H04156 from the Japan Society for the Promotion of Science. DKJ was funded by European Union H2020 (FutureMARES, contract #869300). OS was supported by I+D+i projects RYC2019-027073-I and PIE HOLOCENO 20213AT014 funded by MCIN/AEI/10.13039/501100011033 and FEDER. PIM was supported by an Australian Research Council Discovery Grant (DP200100575). PM This work is contributing to the ICTA ‘‘Unit of Excellence’’ (MinECo, MDM2015-0552). The IAEA is grateful for the support provided to its Environment Laboratories by the Government of the Principality of Monaco. NM was supported by the project RTI2018-095441-B-C21 funded by MCIN/AEI/10.13039/501100011033 and by FEDER. IM was supported by a Juan de la Cierva Incorporación postdoctoral fellowship (IJC2020-045917-I I) from the Ministry of Science and Innovation (Spanish Government).
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- 2022
17. Future Mangrove Carbon Storage Under Climate Change and Deforestation
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Chatting, Mark, primary, Al-Maslamani, Ibrahim, additional, Walton, Mark, additional, Skov, Martin W., additional, Kennedy, Hilary, additional, Husrevoglu, Y. Sinan, additional, and Le Vay, Lewis, additional
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- 2022
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18. A question of standards: adapting carbon and other PES markets to work for community seagrass conservation
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Shilland, Robyn, Grimsditch, Gabriel, Ahmed, Mohamed, Bandeira, Salomão, Kennedy, Hilary, Potouroglou, Maria, and Huxham, Mark
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Seagrass, Community-based management, Voluntary carbon market - Abstract
Seagrass meadows deliver multiple ecosystem services that are of particular importance to resource-poor coastal communities, yet they are rapidly declining globally. The Payments for Ecosystem Services (PES) approach has been used to fund the protection of other ‘Blue Carbon’ Ecosystems (BCE), yet seagrass has been incorporated in just one PES project worldwide. Some of the ecosystem services delivered by seagrass have the potential for inclusion under a PES framework but multiple challenges currently make this difficult, particularly under community-based management. PES programmes typically focus on carbon as the tradable service, but scientific uncertainties regarding seagrass carbon are likely to remain significant barriers to using carbon as the sole commodity under current carbon trading standards and market conditions. It is recommended here that project developers demonstrate the multiple ecosystem services delivered by seagrass meadows, along with their importance to coastal communities, in the planning and marketing of seagrass PES projects. Moreover, they should consider approaches that incorporate seagrass meadows into other blue carbon certified projects. The capacities of the communities that rely most heavily on seagrass are generally very limited. Consequently, demanding high levels of scientific certainty over carbon stocks and flows will exclude most of these communities. Standards, buyers and policy makers should consider building community capacity in the technical and marketing requirements of voluntary carbon standards. The voluntary carbon market has the flexibility to pioneer certified seagrass carbon, potentially leading to the inclusion of seagrass carbon in formal policy instruments, such as Nationally Determined Contributions (NDCs).
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- 2021
19. Nutrient Dynamics and Ecosystem Metabolism in the Bay of Blanes (NW Mediterranean)
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Lucea, Anna, Duarte, Carlos M., Agusti, Susana, and Kennedy, Hilary
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- 2005
20. Surface ice and gap layers in Antarctic sea ice : highly productive habitats
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Kattner, Gerhard, Thomas, David N., Haas, Christian, Kennedy, Hilary, and Dieckmann, Gerhard S.
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- 2004
21. Mangrove carbon stocks and biomass partitioning in an extreme environment
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Mark, Chatting, LeVay, Lewis, Walton, Mark, Skov, Martin W., Kennedy, Hilary, Wilson, Simon, and Al-Maslamani, Ibrahim
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Mangrove carbon stock ,Blue carbon ,Mangrove allometry ,Biomass allocation ,Mangrove below ground - Abstract
Global inventories that show mangrove forests have rich carbon stores currently lack data from arid areas where carbon stocks may be functionally impoverished relative to humid regions. We quantified total carbon stocks (C) of three arid Avicennia marina stands in Qatar and report an aboveground biomass allometric equation and the first below ground biomass allometric equation in the region. The allometric relationships indicate that below ground mangrove C stocks in arid locations are more important than previously reported. Comparison of previously published and our locally developed allometric equations show that A. marina in Qatar allocate comparatively more biomass to below ground components than the same species in tropical humid settings, which is consistent with plant adaptations to living in stressed conditions. Total C stocks were 45.70 ± 3.70 Mg C ha−1, of which tree and soil C stocks to 50 cm depth represented 10.18 ± 0.82 Mg C ha−1 and 35.52 ± 2.88 Mg ha−1 respectively. Soil C stocks to 1 m depth were 50.17 ± 6.27 Mg C ha−1. Overall, mangroves sustain relatively small C stocks in the arid, hypersaline environment of Qatar, which may be due to both relatively low tree productivity and growth, as well as limited rainfall-driven transport of terrigenous sediment inputs. By providing further estimates of mangrove carbon at their climatic extremes, these results can contribute to a better quantification of global mangrove carbon, reduce uncertainty in below ground tree C estimates from arid mangroves and have implications for mangrove carbon stocks in the face of climate change. Qatar National Research Fund, National Priorities Research Program (NPRP) [grant number 7–1302 – 1–242
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- 2020
22. Seagrass ecosystem services: assessment and scale of benefits
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de los Santos, Carmen B., Scott, Abbi, Arias-Ortiz, Ariane, Jones, Benjamin, Kennedy, Hilary, Mazarrasa, Inés, McKenzie, Len, Nordlund, Lina Mtwana, de la Torre-Castro, Maricela de la T, Unsworth, Richard K.F., Ambo-Rappe, Rohani, Potouroglou, M, Grimsditch, G, Weatherdon, L, and Lutz, S
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Seagrass ecosystems - Abstract
Seagrass ecosystems provide a wide variety of services that support human well-being around the world (Barbier et al. 2011). It is estimated that more than 1 billion people live within 100 km of a coast with seagrass meadows, thus potentially benefiting from their provisioning, regulating and cultural services. Seagrasses play a significant global role in supporting food security, mitigating climate change, enriching biodiversity, purifying water, protecting the coastline and controlling diseases (Figure 2). The integrity and provision of services by seagrass meadows are enhanced by their proximity and connectivity to other coastal ecosystems such as tidal marshes, coral reefs, mangrove and kelp forests, and oyster and mussel beds. The maintenance and regulation of these services is therefore essential to support human well-being and promote development in the future. info:eu-repo/semantics/publishedVersion
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- 2020
23. Losses of Soil Organic Carbon with Deforestation in Mangroves of Madagascar
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Arias-Ortiz, Ariane, primary, Masqué, Pere, additional, Glass, Leah, additional, Benson, Lisa, additional, Kennedy, Hilary, additional, Duarte, Carlos M., additional, Garcia-Orellana, Jordi, additional, Benitez-Nelson, Claudia R., additional, Humphries, Marc S., additional, Ratefinjanahary, Ismaël, additional, Ravelonjatovo, Jaona, additional, and Lovelock, Catherine E., additional
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- 2020
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24. The measurement of pH in saline and hypersaline media at sub-zero temperatures: Characterization of Tris buffers
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Papadimitriou, Stathys, Loucaides, Socratis, Rérolle, Victoire, Achterberg, Eric P., Dickson, Andrew G., Mowlem, Matthew, Kennedy, Hilary, Bangor University, National Oceanography Centre [Southampton] (NOC), University of Southampton, Austral, Boréal et Carbone (ABC), Laboratoire d'Océanographie et du Climat : Expérimentations et Approches Numériques (LOCEAN), Institut de Recherche pour le Développement (IRD)-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Pierre et Marie Curie - Paris 6 (UPMC)-Muséum national d'Histoire naturelle (MNHN)-Institut Pierre-Simon-Laplace (IPSL (FR_636)), École normale supérieure - Paris (ENS Paris), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris Diderot - Paris 7 (UPD7)-École polytechnique (X)-Centre National d'Études Spatiales [Toulouse] (CNES)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-École normale supérieure - Paris (ENS Paris), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Paris Diderot - Paris 7 (UPD7)-École polytechnique (X)-Centre National d'Études Spatiales [Toulouse] (CNES)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Pierre et Marie Curie - Paris 6 (UPMC)-Muséum national d'Histoire naturelle (MNHN)-Institut Pierre-Simon-Laplace (IPSL (FR_636)), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Paris Diderot - Paris 7 (UPD7)-École polytechnique (X)-Centre National d'Études Spatiales [Toulouse] (CNES)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS), Helmholtz Centre for Ocean Research [Kiel] (GEOMAR), Muséum national d'Histoire naturelle (MNHN)-Institut de Recherche pour le Développement (IRD)-Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Institut Pierre-Simon-Laplace (IPSL (FR_636)), École normale supérieure - Paris (ENS-PSL), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris Diderot - Paris 7 (UPD7)-École polytechnique (X)-Centre National d'Études Spatiales [Toulouse] (CNES)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-École normale supérieure - Paris (ENS-PSL), and Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Paris Diderot - Paris 7 (UPD7)-École polytechnique (X)-Centre National d'Études Spatiales [Toulouse] (CNES)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-Muséum national d'Histoire naturelle (MNHN)-Institut de Recherche pour le Développement (IRD)-Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Institut Pierre-Simon-Laplace (IPSL (FR_636))
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Chemistry(all) ,Environmental Chemistry ,[PHYS.PHYS.PHYS-GEO-PH]Physics [physics]/Physics [physics]/Geophysics [physics.geo-ph] ,Oceanography ,ComputingMilieux_MISCELLANEOUS ,Water Science and Technology - Abstract
Highlights • pH of Tris buffers determined in synthetic seawater and brines with the Harned cell. • pH determination of Tris buffers to the freezing point of synthetic solutions. • pH determination of the equimolal and non-equimolal Tris buffer variants. • pH measurement is facilitated at below-zero temperatures, such as in sea ice brines. The pH on the total proton scale of the Tris-HCl buffer system (pH(Tris)) was characterized rigorously with the electrochemical Flamed cell in salinity (S) 35 synthetic seawater and S = 45-100 synthetic seawater-derived brines at 25 and 0 degrees C, as well as at the freezing point of the synthetic solutions (-1.93 degrees C at S = 35 to -6 degrees C at S = 100). The electrochemical characterization of the common equimolal Tris buffer [R-Tris = m(Tris)/m(Tris-H+) = 1.0, with m(Tris) = m(Tris-H+) = 0.04 mol kg(H2O)(-1) = molality of the conjugate acid-base pair of 2-amino-2-hydroxymethyl-1,3-propanediol (Tris)] yielded pH(Tris) values which increased with increasing salinity and decreasing temperature. The electrochemical characterization of a non-equimolal Tris buffer variant (R-Tris = 0.5, with m(Tris) = 0.02 mol kg(H2O)(-1) and MTris-H+ = 0.04 mol kg(H2O)(-1)) yielded pH(Tris) values that were consistently less alkaline by 03 pH unit than those of the equimolal Tris buffer. This is in agreement with the values derived from the stoichiometric equilibrium of the Tris-H+ dissociation reaction, described by the Henderson - Hasselbalch equation, pH(Tris) = pK(Tris)* + logR(Tris), with pK(Tris)* = stoichiometric equilibrium dissociation constant of Tris-H+, equivalent to equimolal pH(Tris). This consistency allows reliable use of other R-Tris variants of the Tris-HCl buffer system within the experimental conditions reported here. The results of this study will facilitate the pH measurement in saline and hypersaline systems at below-zero temperatures, such as sea ice brines.
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- 2016
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25. Mirabilite solubility in equilibrium sea ice brines
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Butler, Benjamin Miles, Papadimitriou, Stathys, Santoro, Anna, and Kennedy, Hilary
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Geochemistry and Petrology - Abstract
The sea ice microstructure is permeated by brine channels and pockets that contain concentrated seawater-derived brine. Cooling the sea ice results in further formation of pure ice within these pockets as thermal equilibrium is attained, resulting in a smaller volume of increasingly concentrated residual brine. The coupled changes in temperature and ionic composition result in supersaturation of the brine with respect to mirabilite (Na2SO4·10H2O) at temperatures below −6.38 °C, which consequently precipitates within the sea ice microstructure. Here, mirabilite solubility in natural and synthetic seawater derived brines, representative of sea ice at thermal equilibrium, has been measured in laboratory experiments between 0.2 and −20.6 °C, and hence we present a detailed examination of mirabilite dynamics within the sea ice system. Below −6.38 °C mirabilite displays particularly large changes in solubility as the temperature decreases, and by −20.6 °C its precipitation results in 12.90% and 91.97% reductions in the total dissolved Na+ and SO42− concentrations respectively, compared to that of conservative seawater concentration. Such large non-conservative changes in brine composition could potentially impact upon the measurement of sea ice brine salinity and pH, whilst the altered osmotic conditions may create additional challenges for the sympagic organisms that inhabit the sea ice system. At temperatures above −6.38 °C, mirabilite again displays large changes in solubility that likely aid in impeding its identification in field samples of sea ice. Our solubility measurements display excellent agreement with that of the FREZCHEM model, which was therefore used to supplement our measurements to colder temperatures. Measured and modelled solubility data were incorporated into a 1D model for the growth of first-year Arctic sea ice. Model results ultimately suggest that mirabilite has a near ubiquitous presence in much of the sea ice on Earth, and illustrate the spatial and temporal evolution of mirabilite within sea ice as it grows throughout an Arctic winter, reaching maximum concentrations of 2.3 g kg−1.
- Published
- 2016
- Full Text
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26. Fingerprinting Blue Carbon: Rationale and Tools to Determine the Source of Organic Carbon in Marine Depositional Environments
- Author
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Geraldi, Nathan R., primary, Ortega, Alejandra, additional, Serrano, Oscar, additional, Macreadie, Peter I., additional, Lovelock, Catherine E., additional, Krause-Jensen, Dorte, additional, Kennedy, Hilary, additional, Lavery, Paul S., additional, Pace, Michael L., additional, Kaal, Joeri, additional, and Duarte, Carlos M., additional
- Published
- 2019
- Full Text
- View/download PDF
27. Measuring the role of seagrasses in regulating sediment surface elevation
- Author
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Potouroglou, Maria, primary, Bull, James C., additional, Krauss, Ken W., additional, Kennedy, Hilary A., additional, Fusi, Marco, additional, Daffonchio, Daniele, additional, Mangora, Mwita M., additional, Githaiga, Michael N., additional, Diele, Karen, additional, and Huxham, Mark, additional
- Published
- 2017
- Full Text
- View/download PDF
28. Macro-nutrient concentrations in Antarctic pack ice: Overall patterns and overlooked processes
- Author
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Fripiat, François, primary, Meiners, Klaus M., additional, Vancoppenolle, Martin, additional, Papadimitriou, Stathys, additional, Thomas, David N., additional, Ackley, Stephen F., additional, Arrigo, Kevin R., additional, Carnat, Gauthier, additional, Cozzi, Stefano, additional, Delille, Bruno, additional, Dieckmann, Gerhard S., additional, Dunbar, Robert B., additional, Fransson, Agneta, additional, Kattner, Gerhard, additional, Kennedy, Hilary, additional, Lannuzel, Delphine, additional, Munro, David R., additional, Nomura, Daiki, additional, Rintala, Janne-Markus, additional, Schoemann, Véronique, additional, Stefels, Jacqueline, additional, Steiner, Nadja, additional, and Tison, Jean-Louis, additional
- Published
- 2017
- Full Text
- View/download PDF
29. Harnessing the climate mitigation, conservation and poverty alleviation potential of seagrasses: prospects for developing blue carbon initiatives and payment for ecosystem service programmes
- Author
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Hejnowicz, Adam P., primary, Kennedy, Hilary, additional, Rudd, Murray A., additional, and Huxham, Mark R., additional
- Published
- 2015
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30. Seagrass sediments as a global carbon sink: isotopic constraints
- Author
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Kennedy, Hilary, Beggins, Jeff, Duarte, Carlos M., Fourqurean, James W., Holmer, Marianne, Marbà, Núria, and Middelburg, Jack J.
- Subjects
Stable isotope ,Seagrass ,Carbon sink - Abstract
8 páginas, 4 figuras, 1 tabla., Seagrass meadows are highly productive habitats found along many of the world's coastline, providing important services that support the overall functioning of the coastal zone. The organic carbon that accumulates in seagrass meadows is derived not only from seagrass production but from the trapping of other particles, as the seagrass canopies facilitate sedimentation and reduce resuspension. Here we provide a comprehensive synthesis of the available data to obtain a better understanding of the relative contribution of seagrass and other possible sources of organic matter that accumulate in the sediments of seagrass meadows. The data set includes 219 paired analyses of the carbon isotopic composition of seagrass leaves and sediments from 207 seagrass sites at 88 locations worldwide. Using a three source mixing model and literature values for putative sources, we calculate that the average proportional contribution of seagrass to the surface sediment organic carbon pool is ∼50%. When using the best available estimates of carbon burial rates in seagrass meadows, our data indicate that between 41 and 66 gC m−2 yr−1 originates from seagrass production. Using our global average for allochthonous carbon trapped in seagrass sediments together with a recent estimate of global average net community production, we estimate that carbon burial in seagrass meadows is between 48 and 112 Tg yr−1, showing that seagrass meadows are natural hot spots for carbon sequestration., Finaciación proveniente de Florida Keys National Marine Sanctuary Water Quality Protection Program, de U.S. Environmental Protection Agency (contract X97468102-0), la National Science Foundation a través del programa Florida Coastal Everglades Long-Term Ecological Research en virtud de las concesiones DBI-0620409 y DEB-9910514, y Seagrass Recovery, Inc.
- Published
- 2010
31. Organic carbon sources to SE Asian coastal sediments
- Author
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Kennedy, Hilary, Gacia, Esperança, Kennedy, D. P., Papadimitriou, S., and Duarte, Carlos M.
- Subjects
Total organic carbon ,chemistry.chemical_classification ,biology ,Sediment ,Aquatic Science ,Oceanography ,biology.organism_classification ,Sedimentary depositional environment ,Seagrass ,chemistry ,Outwelling ,Sediment trap ,Environmental science ,Sedimentary organic matter ,Organic matter - Abstract
The carbon, nitrogen and the stable carbon isotopic composition, δ13C, of organic matter has been used to elucidate the source(s) of this material to coastal sediments. Sediments were collected at 15 coastal locations in the Philippines and Vietnam, which broadly represented different depositional environments ranging from seagrass meadows, through seagrass meadows located near mangroves and to mangrove stands. In addition, short-term sediment traps were deployed at 12 of the sites where seagrass was present. Mean sediment organic carbon concentration and C/N increased and δ13C of organic matter decreased from seagrass to mangrove dominated settings. The organic carbon flux measured by the sediment trap deployments was very variable (32 ± 3 to ∼ 700 mmol m-2 d-1) and represented only a small fraction of the total particle flux. The importance of seagrass as a source of organic matter to the sediments was assessed by using a simple mixing model and the average δ 13C values for seagrass, their epiphytic community and surface water particulate matter (seston). A positive correlation between seagrass leaf biomass and sediment δ13C in seagrass dominated settings suggests that these macrophytes do significantly influence the composition of sedimentary organic matter. Seagrass was however rarely found to be the dominant source of organic matter to the underlying sediments. Both sediment trap and sediment data suggest that material of planktonic origin was the dominant source of sedimentary organic matter in these settings. At the sites dominated by mangroves the concentration of organic matter (∼ 1-13 × 103 mmol g-1) in the sediment is generally higher than at seagrass dominated sites due to the outwelling of organic matter from the mangrove stands. Mangrove organic matter often dominates the sedimentary input but other sources of organic matter must contribute to cause the observed range in sediment δ13C. © 2004 Elsevier Ltd. All rights reserved.
- Published
- 2004
32. Sea ice contribution to the air–sea CO2 exchange in the Arctic and Southern Oceans
- Author
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Rysgaard, Søren, primary, Bendtsen, Jørgen, additional, Delille, Bruno, additional, Dieckmann, Gerhard S., additional, Glud, Ronnie N., additional, Kennedy, Hilary, additional, Mortensen, John, additional, Papadimitriou, Stathys, additional, Thomas, David N., additional, and Tison, Jean-Louis, additional
- Published
- 2011
- Full Text
- View/download PDF
33. Calcium carbonate as ikaite crystals in Antarctic sea ice
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Dieckmann, Gerhard S., primary, Nehrke, Gernot, additional, Papadimitriou, Stathys, additional, Göttlicher, Jörg, additional, Steininger, Ralph, additional, Kennedy, Hilary, additional, Wolf-Gladrow, Dieter, additional, and Thomas, David N., additional
- Published
- 2008
- Full Text
- View/download PDF
34. Responses of Bovine WC1+γδ T Cells to Protein and Nonprotein Antigens ofMycobacterium bovis
- Author
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Welsh, Michael D., primary, Kennedy, Hilary E., additional, Smyth, Allister J., additional, Girvin, R. Martyn, additional, Andersen, Peter, additional, and Pollock, John M., additional
- Published
- 2002
- Full Text
- View/download PDF
35. Modulation of Immune Responses toMycobacterium bovisin Cattle Depleted of WC1+γδ T Cells
- Author
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Kennedy, Hilary E., primary, Welsh, Michael D., additional, Bryson, David G., additional, Cassidy, Joseph P., additional, Forster, Fiona I., additional, Howard, Christopher J., additional, Collins, Robert A., additional, and Pollock, John M., additional
- Published
- 2002
- Full Text
- View/download PDF
36. Detection of Chlamydial Antibody by Fetal Serology—An Aid to the Diagnosis of Ovine Abortion
- Author
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Kennedy, Hilary E., primary, McCullough, Samuel J., additional, Graham, David, additional, Cassidy, Joseph, additional, Malone, Frank E., additional, and Ellis, William A., additional
- Published
- 2001
- Full Text
- View/download PDF
37. Gelatinase A not alpha-secretase?
- Author
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Walsh, Dominic M., primary, Williams, Carvell H., additional, Kennedy, Hilary E., additional, Allsop, David, additional, and Murphy, Gillian, additional
- Published
- 1994
- Full Text
- View/download PDF
38. Sea ice contribution to the air-sea CO2 exchange in the Arctic and Southern Oceans.
- Author
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RYSGAARD, SØREN, BENDTSEN, JØRGEN, DELILLE, BRUNO, DIECKMANN, GERHARD S., GLUD, RONNIE N., KENNEDY, HILARY, MORTENSEN, JOHN, PAPADIMITRIOU, STATHYS, THOMAS, DAVID N., and TISON, JEAN-LOUIS
- Subjects
SEA ice ,OCEAN-atmosphere interaction ,CARBON dioxide ,PRIMARY productivity (Biology) ,MELTWATER - Abstract
ABSTRACT Although salt rejection from sea ice is a key process in deep-water formation in ice-covered seas, the concurrent rejection of CO
2 and the subsequent effect on air-sea CO2 exchange have received little attention. We review the mechanisms by which sea ice directly and indirectly controls the air-sea CO2 exchange and use recent measurements of inorganic carbon compounds in bulk sea ice to estimate that oceanic CO2 uptake during the seasonal cycle of sea-ice growth and decay in ice-covered oceanic regions equals almost half of the net atmospheric CO2 uptake in ice-free polar seas. This sea-ice driven CO2 uptake has not been considered so far in estimates of global oceanic CO2 uptake. Net CO2 uptake in sea-ice-covered oceans can be driven by; (1) rejection during sea-ice formation and sinking of CO2 -rich brine into intermediate and abyssal oceanic water masses, (2) blocking of air-sea CO2 exchange during winter, and (3) release of CO2 -depleted melt water with excess total alkalinity during sea-ice decay and (4) biological CO2 drawdown during primary production in sea ice and surface oceanic waters. [ABSTRACT FROM AUTHOR]- Published
- 2011
- Full Text
- View/download PDF
39. Responses of bovine WC1(+) gammadelta T cells to protein and nonprotein antigens of Mycobacterium bovis.
- Author
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Welsh, Michael D, Kennedy, Hilary E, Smyth, Allister J, Girvin, R Martyn, Andersen, Peter, and Pollock, John M
- Abstract
WC1(+) gammadelta T cells of Mycobacterium bovis-infected cattle are highly responsive to M. bovis sonic extract (MBSE). In mycobacterial infections of other species, gammadelta T cells have been shown to respond to protein and nonprotein antigens, but the bovine WC1(+) gammadelta T-cell antigenic targets within MBSE require further definition in terms of the dominance of protein versus nonprotein components. The present study sought to characterize the WC1(+) gammadelta T-cell antigenic targets, together with the role of interleukin-2 (IL-2), in the context of M. bovis infection. This was achieved by testing crude and defined antigens to assess protein versus nonprotein recognition by WC1(+) gammadelta T cells in comparison with CD4(+) alphabeta T cells. Both cell types proliferated strongly in response to MBSE, with CD4(+) T cells being the major producers of gamma interferon (IFN-gamma). However, enzymatic digestion of the protein in MBSE removed its ability to stimulate CD4(+) T-cell responses, whereas some WC1(+) gammadelta T-cell proliferation remained. The most antigenic protein inducing proliferation and IFN-gamma secretion in WC1(+) gammadelta T-cell cultures was found to be ESAT-6, which is a potential novel diagnostic reagent and vaccine candidate. In addition, WC1(+) gammadelta T-cell proliferation was observed in response to stimulation with prenyl pyrophosphate antigens (isopentenyl pyrophosphate and monomethyl phosphate). High levels of cellular activation (CD25 expression) resulted from MBSE stimulation of WC1(+) gammadelta T cells from infected animals. A similar degree of activation was induced by IL-2 alone, but for WC1(+) gammadelta T-cell division IL-2 was found to act only as a costimulatory signal, enhancing antigen-driven responses. Overall, the data indicate that protein antigens are important stimulators of WC1(+) gammadelta T-cell proliferation and IFN-gamma secretion in M. bovis infection, with nonprotein antigens inducing significant proliferation. These findings have important implications for diagnostic and vaccine development.
- Published
- 2002
40. Responses of Bovine WC1+γδ T Cells to Protein and Nonprotein Antigens of Mycobacterium bovis
- Author
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Welsh, Michael D., Kennedy, Hilary E., Smyth, Allister J., Girvin, R. Martyn, Andersen, Peter, and Pollock, John M.
- Abstract
ABSTRACTWC1+γδ T cells of Mycobacterium bovis-infected cattle are highly responsive to M. bovissonic extract (MBSE). In mycobacterial infections of other species, γδ T cells have been shown to respond to protein and nonprotein antigens, but the bovine WC1+γδ T-cell antigenic targets within MBSE require further definition in terms of the dominance of protein versus nonprotein components. The present study sought to characterize the WC1+γδ T-cell antigenic targets, together with the role of interleukin-2 (IL-2), in the context of M. bovisinfection. This was achieved by testing crude and defined antigens to assess protein versus nonprotein recognition by WC1+γδ T cells in comparison with CD4+αβ T cells. Both cell types proliferated strongly in response to MBSE, with CD4+T cells being the major producers of gamma interferon (IFN-γ). However, enzymatic digestion of the protein in MBSE removed its ability to stimulate CD4+T-cell responses, whereas some WC1+γδ T-cell proliferation remained. The most antigenic protein inducing proliferation and IFN-γ secretion in WC1+γδ T-cell cultures was found to be ESAT-6, which is a potential novel diagnostic reagent and vaccine candidate. In addition, WC1+γδ T-cell proliferation was observed in response to stimulation with prenyl pyrophosphate antigens (isopentenyl pyrophosphate and monomethyl phosphate). High levels of cellular activation (CD25 expression) resulted from MBSE stimulation of WC1+γδ T cells from infected animals. A similar degree of activation was induced by IL-2 alone, but for WC1+γδ T-cell division IL-2 was found to act only as a costimulatory signal, enhancing antigen-driven responses. Overall, the data indicate that protein antigens are important stimulators of WC1+γδ T-cell proliferation and IFN-γ secretion in M. bovisinfection, with nonprotein antigens inducing significant proliferation. These findings have important implications for diagnostic and vaccine development.
- Published
- 2002
- Full Text
- View/download PDF
41. Modulation of immune responses to Mycobacterium bovis in cattle depleted of WC1(+) gamma delta T cells.
- Author
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Kennedy, Hilary E, Welsh, Michael D, Bryson, David G, Cassidy, Joseph P, Forster, Fiona I, Howard, Christopher J, Collins, Robert A, and Pollock, John M
- Abstract
It is accepted that cell-mediated immune responses predominate in mycobacterial infections. Many studies have shown that CD4(+) T cells produce Th1 cytokines, such as gamma interferon (IFN-gamma), in response to mycobacterial antigens and that the cytolytic activity of CD8(+) cells toward infected macrophages is important. However, the extent and manner in which gamma delta T cells participate in this response remain unclear. In ruminants, gamma delta T cells comprise a major proportion of the peripheral blood mononuclear cell population. We have previously shown that WC1(+) gamma delta T cells are involved early in Mycobacterium bovis infection of cattle, but their specific functions are not well understood. Here we describe an in vivo model of bovine tuberculosis in which the WC1(+) gamma delta T cells were depleted from the peripheral circulation and respiratory tract, by infusion of WC1(+)-specific monoclonal antibody, prior to infection. While no effects on disease pathology were observed in this experiment, results indicate that WC1(+) gamma delta T cells, which become significantly activated (CD25(+)) in the circulation of control calves from 21 days postinfection, may play a role in modulating the developing immune response to M. bovis. WC1(+)-depleted animals exhibited decreased antigen-specific lymphocyte proliferative response, an increased antigen-specific production of interleukin-4, and a lack of specific immunoglobulin G2 antibody. This suggests that WC1(+) gamma delta TCR(+) cells contribute, either directly or indirectly, toward the Th1 bias of the immune response in bovine tuberculosis--a hypothesis supported by the decreased innate production of IFN-gamma, which was observed in WC1(+)-depleted calves.
- Published
- 2002
42. Modulation of Immune Responses to Mycobacterium bovisin Cattle Depleted of WC1+γδ T Cells
- Author
-
Kennedy, Hilary E., Welsh, Michael D., Bryson, David G., Cassidy, Joseph P., Forster, Fiona I., Howard, Christopher J., Collins, Robert A., and Pollock, John M.
- Abstract
ABSTRACTIt is accepted that cell-mediated immune responses predominate in mycobacterial infections. Many studies have shown that CD4+T cells produce Th1 cytokines, such as gamma interferon (IFN-γ), in response to mycobacterial antigens and that the cytolytic activity of CD8+cells toward infected macrophages is important. However, the extent and manner in which γδ T cells participate in this response remain unclear. In ruminants, γδ T cells comprise a major proportion of the peripheral blood mononuclear cell population. We have previously shown that WC1+γδ T cells are involved early in Mycobacterium bovisinfection of cattle, but their specific functions are not well understood. Here we describe an in vivo model of bovine tuberculosis in which the WC1+γδ T cells were depleted from the peripheral circulation and respiratory tract, by infusion of WC1+-specific monoclonal antibody, prior to infection. While no effects on disease pathology were observed in this experiment, results indicate that WC1+γδ T cells, which become significantly activated (CD25+) in the circulation of control calves from 21 days postinfection, may play a role in modulating the developing immune response to M. bovis. WC1+-depleted animals exhibited decreased antigen-specific lymphocyte proliferative response, an increased antigen-specific production of interleukin-4, and a lack of specific immunoglobulin G2 antibody. This suggests that WC1+γδ TCR+cells contribute, either directly or indirectly, toward the Th1 bias of the immune response in bovine tuberculosis—a hypothesis supported by the decreased innate production of IFN-γ, which was observed in WC1+-depleted calves.
- Published
- 2002
- Full Text
- View/download PDF
43. Kinetics of ikaite precipitation and dissolution in seawater-derived brines at sub-zero temperatures to 265K
- Author
-
Papadimitriou, Stathys, Kennedy, Hilary, Kennedy, Paul, and Thomas, David N.
- Subjects
Geochemistry and Petrology - Abstract
The kinetics of calcium carbonate hexahydrate (ikaite) precipitation and dissolution were investigated in seawater and seawater-derived brines at sub-zero temperatures using the constant addition experimental technique. The steady state rate of these two processes was found to be a function of the deviation of the solution from equilibrium with respect to ikaite and conformed to the same empirical rate law as the anhydrous CaCO3 polymorphs, calcite and aragonite. In addition to the saturation state of the brine with respect to ikaite, the salinity of the brine and the temperature of the reaction evidently exerted some control on the ikaite precipitation kinetics, while the dissolution kinetics of the polymorph were not noticeably influenced by these two parameters. The experimental salinity and temperature conditions were equivalent to those at thermal equilibrium between brine and ice in the sea ice cover of polar seas. Simple modelling of the CO2 system by extrapolation of the oceanic equivalent to sea ice brines showed that the physical concentration of seawater ions and the changes in ikaite solubility as a function of salinity and temperature, both inherent in the sea ice system, would be insufficient to drive the emergent brines to ikaite supersaturation and precipitation in sea ice down to −8°C. The loss of dissolved inorganic carbon to the gas phase of sea ice and to sympagic autotrophs are two independent mechanisms which, in nature, could prompt the brine CO2 system towards ikaite supersaturation and precipitation. Under these conditions, the steady state precipitation rate of ikaite was found to be fast enough for rapid formation within short time scales (days to weeks) in sea ice. The observed ikaite dissolution kinetics were also found conducive to short turn-over time scales of a few hours to a few days in corrosive solutions, such as surface seawater.
- Full Text
- View/download PDF
44. Assessing the role of intertidal seagrasses as coastal carbon sinks in Scotland
- Author
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Potouroglou, Maria, Diele, Karen, and Kennedy, Hilary
- Subjects
577 ,Ecology ,ecosystem ,biomass ,carbon ,sediment ,GE Environmental Sciences - Abstract
Seagrasses are marine foundation species that form ecologically important habitats in coastal areas around the world. They provide a range of ecosystem services, including coastal protection and the recently recognised large contribution to global carbon sequestration and storage. To date, the majority of published studies on the aforementioned ecosystem services is limited to specific geographic regions and seagrass species. This PhD study attempted to explore and provide the first evidence, to the best of our knowledge, on the role of Scottishseagrasses as carbon sinks and sediment stabilisers. In 2013, shoot dynamics of Zostera noltii plots were monitored biweekly and seasonally in the Forth estuary and digital images of the surveyed plots were taken for the development of a remote sensing technique which would accurately estimate the vegetation cover. In 2014, sediment samples from vegetated and unvegetated plots within beds of Z. marina and Z. noltii were collected from all the major estuaries along the east coast of Scotland, from the Firth of Forth in the south to Dornoch Firth in the north. Samples were analysed for organic matter, organic carbon, radionuclides 210Pb, 137Cs and 241Am, and δ13C in order to determine the organic matter and organic carbon density, longevity and sources of carbon respectively. To explore the role of seagrass in sediment deposition and stability, surface elevation was measured monthly in seagrass plots and bare sediment in the Forth estuary over two years. The results and main mechanisms underlying these findings are reported and discussed in detail in each chapter. In short, the proposed method based on digital images provided estimates of seagrass coverage that are more accurate than observers' estimates, with some constraints when macroalge and/or extreme light are present. Intertidal seagrass meadows in Scotland showed significantly enhanced carbon storage compared with bare sediment. Seagrass plots contained variable quantities of carbon in their sediments with species composition having a significant effect on carbon stocks, whereas depth and seagrass abundance had no effect on carbon stores. Despite their small above-ground biomass Scottish seagrass plots had a strong influence on sediment deposition and prevented erosion. Further research is needed to understand what factors drive large carbon sequestration and storage at some sites, thus contributing policy-relevant information on the prediction of the seagrass carbon hot-spots. Also, long-term datasets on surface elevation change are important in order to understand the effect of all the processes involved on sediment deposition in seagrass beds.
- Published
- 2017
45. Mineral dynamics in sea ice brines
- Author
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Butler, Benjamin Miles and Kennedy, Hilary
- Subjects
551.34 - Abstract
The sea ice microstructure is permeated by millimetre to micrometre sized inclusions filled with concentrated seawater-derived brine. It is within these brines that the in-situ chemical and biological reactions occur. The brines are confined to a temperature-dependent composition, becoming more concentrated and reducing in volume with decreasing temperature. Upon sufficient cooling the coupled effects of lower temperature and higher salinity results in the brine exceeding the solubility of a mineral, which precipitates. Given the complex composition of seawater, there are several minerals that can exceed saturation within the polar temperature spectrum, each with their own dynamics and environmental significance. This thesis investigates mirabilite (Na2SO4 10H2O), gypsum (CaSO4 2H2O) and hydrohalite (NaCl 2H2O). The small crystal size ( m), temperature dependence, and solubility of these minerals acts to limit the scope for studying their existence and behaviour in sea ice with field experiments. For these reasons, their dynamics have been investigated in a laboratory setting using synchrotron X-ray powder distraction experiments, and measurements of mineral solubility in solutions representative of sea ice brines at thermal equilibrium. The experimental observations are supplemented with model predictions, and together are used to provide a comprehensive assessment of the existence, role and e ects of mineral precipitation in sea ice. Mirabilite and hydrohalite are found to cause substantial changes to brine composition and the sea ice microstructure, and are observed to interact in accordance with equilibrium crystallisation. The precipitation of mirabilite is also found to have implications for the measurement of sea ice brine salinity. In contrast, the solubility of gypsum displays complex dynamics between 0.2 and -25 °C, and is shown to be highly dependent upon the SO²⁻₄ concentration, resulting in the processes of mirabilite precipitation and dissolution controlling the fate of gypsum in sea ice.
- Published
- 2016
46. Evaluation design and technical assistance opportunities: early findings from the Beacon Community Program evaluation teams.
- Author
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Rein A, Kennedy H, DeCoudres B, Singer Cohen R, Sabharwal R, and Fairbrother G
- Subjects
- Accountable Care Organizations, American Recovery and Reinvestment Act, Chronic Disease, Cost Control, Cost-Benefit Analysis, Healthcare Disparities, Humans, Outcome and Process Assessment, Health Care, Quality of Health Care, United States, Community Health Services organization & administration, Evaluation Studies as Topic, Government Programs organization & administration, Medical Informatics organization & administration, Research Design
- Abstract
The Beacon Community Cooperative Agreement Program is funding 17 communities to build and strengthen their health information technology (IT) capabilities to enhance care coordination, improve patient and population health, and reduce or restrain costs. Based on the experiences and evidence generated by these communities, the program hopes to illustrate the possibilities of leveraging health IT to achieve desired goals. Doing so requires rigorous evaluation work, which is the subject of this issue brief. Based on semistructured interviews with representatives from each Beacon Community, the brief outlines various study designs, evaluation approaches, outcome measures, and data sources in use. It also identifies some common challenges, including establishing governance models, determining baseline measures, and assessing impact in a relatively constrained timeframe. Technical assistance in disseminating and publishing findings and assessing return on investments will be offered in the coming year.
- Published
- 2012
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