1,721,023 research outputs found
The changing carbonate chemistry of coral reefs : ocean acidification, submarine groundwater discharge, and calcium carbonate (CaCO3) sediment dissolution
No full textUptake of atmospheric CO2 is the dominant driver of ocean acidification (OA) in the open ocean, which is lowering the pH of seawater at an unprecedented rate. However, multiple processes can influence the CO2 of coral reef ecosystems on diel and seasonal timescales, potentially masking or intensifying any effects of increasing atmospheric CO2. Therefore, it is important to quantify any biogeochemical drivers of CO2 variability in coral reefs that could act as feedbacks to OA. This thesis focuses on how permeable sediment metabolism and submarine groundwater discharge affect the carbonate system of coral reefs and, subsequently, the dissolution of sediments
Understanding the Biogeochemical Function of the World\u27s Coral Reefs
No full textCoral reefs throughout the world are under increasing pressure from anthropogenic perturbations which threaten to shift reefs from a state of net CaCO3 production to net dissolution. Once a reef becomes net dissolving it can no longer maintain the growth of CaCO3 structures critical for sustaining the diversity and abundance of life on coral reefs. Therefore it is critical to monitor and predict how anthropogenic forcings will affect the balance of net ecosystem calcification in reef ecosystems. Currently, most coral reef monitoring projects rely on visual measurements of benthic composition and do not measure seawater chemistry parameters such as total alkalinity (TA) and dissolved inorganic carbon (DIC). Vector analysis of TA and DIC can be used to determine the relative influence of organic (photosynthesis/respiration) versus inorganic (CaCO3 production/ dissolution) processes occurring on a coral reef. Results from a mesocosm study demonstrate that benthic community composition is reflected in the TA-DIC slope of the overlying seawater. An analysis of 23 coral reef locations around the globe showed that there is a diverse range in TA-DIC slopes (0.24 to 1.36), indicating a large range in the biogeochemical function of reef ecosystems. A simple model demonstrated that reefs with slopes greatly different from 0.95 have a dramatic increase in the diel variability of seawater pH, which is exacerbated by ocean acidification. Monitoring the pulse of coral reefs via TA and DIC measurements through time and space could help to better inform conservation and management efforts
Porewater Carbonate Chemistry Dynamics in a Temperate and a Subtropical Seagrass System
Get PDFSeagrass 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
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Spatial and Temporal Variability of Seawater Chemistry in Coastal Ecosystems in the Context of Global Change
No full textThis eBook is a collection of articles from a Frontiers Research Topic. Frontiers Research Topics are very popular trademarks of the Frontiers Journals Series: they are collections of at least ten articles, all centered on a particular subject. With their unique mix of varied contributions from Original Research to Review Articles, Frontiers Research Topics unify the most influential researchers, the latest key findings and historical advances in a hot research area! Find out more on how to host your own Frontiers Research Topic or contribute to one as an author by contacting the Frontiers Editorial Office: frontiersin.org/about/contac
Spatial and Temporal Variability of Seawater Chemistry in Coastal Ecosystems in the Context of Global Change
No full textThis eBook is a collection of articles from a Frontiers Research Topic. Frontiers Research Topics are very popular trademarks of the Frontiers Journals Series: they are collections of at least ten articles, all centered on a particular subject. With their unique mix of varied contributions from Original Research to Review Articles, Frontiers Research Topics unify the most influential researchers, the latest key findings and historical advances in a hot research area! Find out more on how to host your own Frontiers Research Topic or contribute to one as an author by contacting the Frontiers Editorial Office: frontiersin.org/about/contac
The Currency of Climate Change - Tracing carbon through coastal ecosystems
No full textGlobal change is occurring due to human induced perturbations of the carbon cycle. Coastal ecosystems, such as mangroves, seagrass beds, and coral reefs play a disproportionate role in the global carbon cycle compared to their relatively small footprint. Tracing the flow of carbon through these systems is critical to evaluating their role in and susceptibility to ongoing climate change. This talk will highlight some of the ongoing and future research projects in the NSU Marine Biogeochemistry Laboratory. Research focuses on tracing carbon flows in coastal systems, including measuring methane and carbon dioxide fluxes across different interfaces (e.g., air-sea, sediment-water, and soil-air). Current projects include measuring the calcium carbonate production rates of coral reefs, using novel techniques to determine the relative contribution of different calcifying groups to a coral reef, and monitoring environmental variability within mangrove, seagrass, and reef habitats. Future projects include measuring the decomposition rates of Sargassum on local Florida beaches and anything related to the coastal carbon cycle
Variations on the Author
Get PDF“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
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