Dissertations / Theses on the topic 'Seagrass ecosystems'
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au, keulen@murdoch edu, and Michael van Keulen. "Water Flow in Seagrass Ecosystems." Murdoch University, 1998. http://wwwlib.murdoch.edu.au/adt/browse/view/adt-MU20040518.91242.
Full textvan, Keulen Michael. "Water flow in seagrass ecosystems." Thesis, van Keulen, Michael ORCID: 0000-0001-6235-5788 (1998) Water flow in seagrass ecosystems. PhD thesis, Murdoch University, 1998. https://researchrepository.murdoch.edu.au/id/eprint/377/.
Full textvan, Keulen Michael. "Water flow in seagrass ecosystems." van Keulen, Michael (1998) Water flow in seagrass ecosystems. PhD thesis, Murdoch University, 1998. http://researchrepository.murdoch.edu.au/377/.
Full textSanmartí, Boixeda Neus. "Biological interactions and resilience of seagrass ecosystems." Doctoral thesis, Universitat de Barcelona, 2020. http://hdl.handle.net/10803/672259.
Full textEl nostre món està sotmès a un ampli ventall de forces que tendeixen a provocar canvis. En aquest context, entendre com la biosfera resisteix, absorbeix o és alterada per aquestes forces resulta una qüestió candent, especialment per l'ecologia. Al respecte, dos conceptes ecològics esdevenen essencials: la resiliència i les interaccions biològiques. La resiliència és la capacitat de persistència o recuperació que tenen els ecosistemes sotmesos a estrès o pertorbacions. Les interaccions entre espècies (efectes de l'existència d'una espècie sobre la fitness d'una altra) contribueixen al manteniment de les funcions ecosistèmiques i, en un cert sentit, constitueixen l'arquitectura de la biodiversitat. A més, la resiliència dels ecosistemes depèn , en gran part, d’aquestes interaccions. Aquesta tesi és un intent d’aprofundir en els aspectes esmentats a través d'una sèrie de casos d’estudi en ecosistemes d’angiospermes marines. Concretament, el que fem és estudiar com els ecosistemes d’angiospermes marines responen a les forces causants de canvis, com aquestes respostes vénen mitjançades per canvis en la interacció entre espècies, i provar d'esbrinar els mecanismes que permeten la coexistència d’espècies que es troben vinculades per interaccions positives i negatives. La nostra aproximació es basa tant en observacions com en experiments en el camp. El Capítol 1 mostra com un increment de matèria orgànica en el sediment debilita el mutualisme entre el bivalve Loripes lucinalis i l’angiosperma marina Cymodocea nodosa. El mecanisme implicat que es proposa per explicar-ho està relacionat amb la plasticitat morfològica de la planta. Així, un increment en la matèria orgànica del sediment (i, probablement, l’anòxia que se'n segueix), fa que la planta modifiqui la morfologia de les seves arrels, que esdevenen molt menys ramificades i fan disminuir per tant la disponibilitat d'hàbitat per als bivalves. Una debilitació del mutualisme pot, potencialment, disminuir la resiliència d’aquests ecosistemes a l’eutrofització i, per tant, comprometre la seva persistència. El Capítol 2 descriu una cascada de facilitació en la qual l’angiosperma marina C. nodosa afavoreix l’abundància del gran bivalve Pinna nobilis, que ajuda a incrementar l'abundància de la garota Paracentrotus lividus, que al seu torn consumeix l’angiosperma. Suggerim que la persistència d’aquest sistema de tres espècies, aparentment inestable (tres interaccions concatenades circularment, dues de positives i una de negativa) es basa en què la interacció negativa (l’efecte de les garotes sobre l’angiosperma) té un abast molt limitat, probablement degut tant al seu comportament alimentari com a les defenses de la planta enfront de l'herbivorisme. Els Capítols 3 i 4 mostren que les espècies de creixement ràpid, com ara C. nodosa, són altament resilients a l'estrès o a les pertorbacions quan aquestes afecten només les parts aèries de les plantes (defoliació parcial o total), recuperant-se ràpidament (dues setmanes) després d'una pertorbació puntual en el temps. C. nodosa mostra diversos mecanismes de tolerància a la defoliació, com ara el creixement compensatori, la reassignació de recursos interns i l’increment en la taxa de formació de nous mòduls. Tanmateix, quan les pertorbacions provoquen la pèrdua de les parts subterrànies (rizomes i arrels), la recuperació és molt més lenta, i triga fins a dos anys. A més, aquesta recuperació depèn de les característiques de la pertorbació com ara la mida de l'àrea afectada i l’època de l'any en què es produeix. En general, aquesta tesi ha contribuït a comprendre millor les respostes dels ecosistemes als canvis. Hem pogut documentar alguns processos que permeten la coexistència entre espècies, així com mecanismes de resiliència específics que esdevenen ecosistèmics quan es manifesten en espècies fundadores d'hàbitat. També hem demostrat com els canvis, més enllà d'afectar espècies individuals més o menys emblemàtiques, poden provocar alteracions de formes més subtils, com ara erosionant la seva resiliència mitjançant la modificació d’interaccions biològiques. Els avenços en totes aquestes direccions complementàries i interrelacionades són crucials per a gestionar i preservar els ecosistemes i evitar el seu possible col·lapse.
Eklöf, Johan S. "Anthropogenic Disturbances and Shifts in Tropical Seagrass Ecosystems." Doctoral thesis, Stockholm University, Department of Systems Ecology, 2008. http://urn.kb.se/resolve?urn=urn:nbn:se:su:diva-7285.
Full textSeagrasses constitute the basis for diverse and productive ecosystems worldwide. In East Africa, they provide important ecosystem services (e.g. fisheries) but are potentially threatened by increasing resource use and lack of enforced management regulations. The major aim of this PhD thesis was to investigate effects of anthropogenic distur-bances, primarily seaweed farming and coastal fishery, in East African seagrass beds. Seaweed farming, often depicted as a sustainable form of aquaculture, had short- and long-term effects on seagrass growth and abundance that cascaded up through the food web to the level of fishery catches. The coastal fishery, a major subsistence activity in the region, can by removing urchin predators indirectly increase densities of the sea urchin Tripneustes gratilla, which has overgrazed seagrasses in several areas. A study using simulated grazing showed that high magnitude leaf removal – typical of grazing urchins – affected seagrasses more than low magnitude removal, typical of fish grazing. Different responses in two co-occurring seagrass species furthermore indicate that high seagrass diversity in tropical seagrass beds could buffer overgrazing effects in the long run. Finally, a literature synthesis suggests that anthropogenic disturbances could drive shifts in seagrass ecosystems to an array of alternative regimes dominated by other or-ganisms (macroalgae, bivalves, burrowing shrimp, polychaetes, etc.). The formation of novel feedback mechanisms makes these regimes resilient to disturbances like seagrass recovery and transplantation projects. Overall, this suggests that resource use activities linked to seagrasses can have large-scale implications if the scale exceeds critical levels. This emphasizes the need for holistic and adaptive management at the seascape level, specifically involving improved techniques for seaweed farming and fisheries, protection of keystone species, and ecosystem-based management approaches.
Sweatman, Jennifer L. "Gammaridean Amphipods as Bioindicators in Subtropical Seagrass Ecosystems." FIU Digital Commons, 2016. http://digitalcommons.fiu.edu/etd/2603.
Full textEklöf, Johan S. "Anthropogenic disturbances and shifts in tropical seagrass ecosystems /." Stockholm : Department of Systems Ecology, Stockholm University, 2008. http://urn.kb.se/resolve?urn=urn:nbn:se:su:diva-7285.
Full textHoward, Jason Lee. "PATTERNS OF CARBON METABOLISM, STORAGE, AND REMINERALIZATION IN SEAGRASS ECOSYSTEMS." FIU Digital Commons, 2018. https://digitalcommons.fiu.edu/etd/3719.
Full textBuñuel, Moreno Xavier. "The role of behavioural and feedback mechanisms in mediating herbivory processes in Mediterranean seagrass ecosystems." Doctoral thesis, Universitat de Barcelona, 2021. http://hdl.handle.net/10803/673886.
Full textEl papel de la relación consumidor-recurso es la base de la estructura y el funcionamiento de las comunidades ecológicas. La óptica tradicional usada en el estudio de estas interacciones ha tendido a omitir la importancia del comportamiento de las especies, sobre todo en el caso de las interacciones planta-herbívoro. Sin embargo, tanto la forma en la que el herbívoro explota a la planta y como la manera en que ésta responde a esa presión son cruciales para determinar la estabilidad de la interacción. Por lo tanto, las actuaciones del herbívoro y la de la planta, contextualizadas en el entorno en el que tiene lugar la interacción, pueden actuar como mediadores de la resiliencia del sistema. Esta tesis se centra en los ecosistemas de Posidonia oceanica y, concretamente, en la interacción entre esta fanerógama con sus dos principales herbívoros -el pez Sarpa salpa y el erizo de mar Paracentrotus lividus-. En esta tesis se evlaúa la importancia del comportamiento de los herbívoros (los patrones de agregación y las estrategias de alimentación de S. salpa y la dependencia de la cobertura foliar de P. lividus) y la resiliencia proporcionada por los mecanismos de retroalimentación (respuestas directas de la planta y procesos indirectos del ecosistema) bajo condiciones cambiantes resultantes del cambio global. Desentrañar estos componentes de la interacción nos permite evaluar su sensibilidad a cada uno de los dichos componentes y comprobar la respuesta y la resiliencia del sistema bajo diferentes condiciones. En el capítulo 1 se muestra la importancia del tamaño del cuerpo de los individuos de Sarpa salpa en sus tasas de consumo individual, en sus patrones de agregación y en las estrategias alimenticias de grupos, además de las potenciales consecuencias de estos procesos sobre la fanerógama Posidonia oceanica. Por un lado, cuanto mayores son los individuos, mayores tasas de consumo muestran. Por otro, los individuos de S.salpa tienden a agregarse con conspecíficos de la misma talla, mientras que el tamaño de los grupos se relaciona positivamente con la talla de los individuos que lo forman. Además, las estrategias de alimentación aumentan en complejidad con el tamaño del grupo y tienden a focalizarse en puntos muy concretos de la pradera. Así, a medida que los individuos crecen, aumentan su potencial impacto en la fanerógama, tanto por su capacidad de consumo como la formación de grandes bancos capaces de concentrar su herbivoría en áreas muy concretas de las praderas. Esta distribución de la herbivoría puede provocar una heterogeneidad espacial con consecuencias sobre el funcionamiento del ecosistema dominado por P. oceanica En el capítulo 2 se comprueba la existencia de una serie de mecanismos reguladores surgidos de un episodio de herbivoría intensa que aportan resiliencia al sistema de Posidonia oceanica una vez disminuida su bóveda foliar. Cuatro de los mecanismos evaluados funcionan como mecanismos de retroalimentación, siendo uno de ellos desplegado activamente por la planta (crecimiento compensatorio) mientras que los tres restantes (preferencia por un recurso alternativo, incremento del riesgo de depredación y disminución del número de erizos por competencia por el recurso y pérdida de cobertura) se desencadenan de forma indirecta y su eficacia se basa en inducir cambios en el comportamiento del herbívoro Paracentrotus lividus. Los resultados obtenidos muestran como P. oceanica es capaz de invertir esfuerzos en recuperar parte de la biomasa foliar perdida, mientras que el mismo sistema es capaz de regular la presión de herbivoría siempre que las condiciones del entorno sean propicias para la aparición de dichos mecanismos. El papel resiliente de estos mecanismos es clave para evitar el potencial colapso de las praderas de P. oceanica bajo el estrés provocado por un episodio de herbivoría intensa. En el capítulo 3 se evalúa el efecto del calentamiento global en la interacción Posidonia oceanica – Sarpa salpa a través de una combinación de aproximaciones de gradiente en campo con experimentos manipulativos de laboratorio. Por un lado, los resultados muestran que el aumento de la temperatura del agua incrementa significativamente las tasas de crecimiento de S.salpa durante su etapa larval, acorta su período en dicha etapa (menos días en la columna de agua) y limita su dispersión, mientras que no muestra ningún efecto en la actividad herbívora durante su fase adulta. Por otro lado, el calentamiento afecta negativamente las tasas de crecimiento de P. oceanica y la vuelve más palatable frente a S. salpa de acuerdo con los resultados en el experimento de preferencia. Nuestro estudio muestra que S. salpa podría desarrollarse más rápido en su etapa más vulnerable, aumentando su supervivencia, pero disminuyendo su capacidad de dispersión, mientras que podría incrementar su preferencia por P. oceanica en su etapa adulta, lo que, junto con la reducción del crecimiento de la fanerógama, podría intensificar considerablemente la fuerza de la interacción. En definitiva, los resultados de esta tesis han servido para constatar la relevancia del comportamiento de los herbívoros en su forma de explotar el recurso, principalmente las estrategias de alimentación de S. salpa, y como los mecanismos de retroalimentación aportan resiliencia y permiten al ecosistema mantenerse en un estado óptimo. Todo ello cobra más importancia al contextualizarlo dentro del proceso del cambio global, dado el probable fortalecimiento de la interacción planta-herbívoro. Conocer la sensibilidad de la interacción a cada uno de los componentes es crucial para decidir donde hay que invertir los esfuerzos de conservación en estos ecosistemas y poder así anticiparnos a como los cambios en las condiciones de contorno pueden alterar el equilibrio final de la interacción.
Leiva, Dueñas Carmen. "The environmental change in coastal ecosystems during the Late Holocene as recorded in seagrass sedimentary archives." Doctoral thesis, Universitat de Barcelona, 2021. http://hdl.handle.net/10803/674010.
Full textLos ecosistemas costeros, especialmente aquellos dominados por macrófitos sumergidos o semi-sumergidos, se encuentran entre los ecosistemas más amenazados del mundo, sufriendo un rápido y constante declive. Sus pérdidas son motivo de grave preocupación debido a su elevada producción, y a que proporcionan muchos servicios ecosistémicos esenciales para el bienestar de nuestras sociedades. Detrás de las tendencias regresivas de los ecosistemas costeros, se encuentra una plétora de presiones humanas adversas, que van desde impactos locales y regionales, incluidas actividades antropogénicas dentro y fuera de las regiones costeras, hasta agentes de cambio a gran escala, como el calentamiento global. Sin embargo, existe una falta crítica sobre el cambio a largo plazo de los ecosistemas costeros vegetados, información que puede proporcionar datos ecológicos de referencia sobre sus dinámicas naturales y vulnerabilidad. Las fanerógamas marinas son plantas superiores creadoras de estructuras tridimensionales complejas que, entre otros muchos servicios, dan lugar a un hábitat de elevada biodiversidad. Estos macrófitos están experimentando un declive generalizado desde principios del siglo XX, regresión especialmente acelerada para la especie endémica mediterránea, Posidonia oceanica. Los estudios a largo plazo son de particular interés en las praderas de P. oceánica, pues al ser una planta marina de gran tamaño, de crecimiento lento y de vida larga, sus cambios y respuestas sustanciales se manifiestan en escalas de tiempo de décadas a siglos. Una comprensión más profunda de la dinámica a largo plazo de las fanerógamas marinas puede ayudar a los gestores a aplicar acciones específicas y actuar en las escalas temporales adecuadas. La disciplina de la paleoecología permite el estudio de la dinámica de los ecosistemas a largo plazo en escalas de tiempo de siglos a milenios, y se puede aplicar en praderas de fanerógamas de P. oceanica gracias a los depósitos orgánicos acumulados bajo ellas. Las reconstrucciones paleoecológicas que usan suelos de praderas marinas aún son escasas y las que hay se han centrado principalmente en procesos alogénicos del ecosistema (controlados externamente). En esta tesis se ha hecho uso de reconstrucciones paleoecológicas en praderas de fanerógamas mediterráneas, principalmente de P. oceánica, a una escala espacial regional con el objetivo de explorar la dinámica a largo plazo de los componentes ecológicos autogénicos y bióticos. Inicialmente, se investigó la utilidad de varios proxies (indicadores) biogeoquímicos y de una técnica (espectroscopía FTIR-ATR) hasta ahora inexplorados en depósitos de praderas marinas, así como cuáles eran los principales procesos biogeoquímicos registrados por estos depósitos. Los resultados obtenidos permitieron describir la dinámica a largo plazo de las praderas marinas, así como sus principales impulsores del cambio a largo plazo y su importancia relativa. Se observó que la dinámica a largo plazo es oscilante, y que la mayoría de las praderas mostraban tendencias regresivas durante los últimos 150 años. Sin embargo, estas tendencias de declive variaban espacialmente, ocurriendo las principales diferencias a escala interregional. Las diferencias en la dinámica a largo plazo entre localidades parecían depender principalmente del contexto ambiental de cada sitio, lo que también afectaba a la resiliencia a largo plazo de las praderas. Los resultados revelan que los principales factores responsables de la variabilidad a largo plazo son múltiples, incluyendo factores de carácter local pero también regional y global. Sin embargo, la contribución relativa entre los factores de influencia local y de gran escala varia espacialmente. La influencia del clima parece especialmente crucial en praderas creciendo en aguas más turbias, bajo la influencia de descargas fluviales más abundantes. Estas praderas mostraron una menor resiliencia ecosistémica a largo plazo. En resumen, esta investigación ha demostrado que las dinámicas a largo plazo de las fanerógamas marinas se pueden estudiar a través de su registro paleoecológico, proporcionando un valioso marco de referencia para evaluar la magnitud de cambios actuales y las consecuencias de diversos impactos combinados en estos ecosistemas marinos. Los resultados de esta tesis revelan que, a pesar de cierta variabilidad espacial de las dinámicas a largo plazo, los cambios más importantes han ocurrido durante el último siglo, predominando las tendencias de declive de la fanerógama o cambios en la composición de las comunidades que alberga. Además, nuestros resultados apuntan a un impacto negativo más agudo del actual cambio climático en aquellas praderas donde la disponibilidad de luz se ve comprometida debido a causas locales. La variabilidad espacial general de las dinámicas a largo plazo de las praderas marinas destaca la necesidad de una gestión local específica a cada pradera, con información previa contextual, información que se puede obtener a partir de estudios paleoecológicos.
Stoner, Elizabeth W. "Human-driven Benthic Jellyfish Blooms: Causes and Consequences for Coastal Marine Ecosystems." FIU Digital Commons, 2014. http://digitalcommons.fiu.edu/etd/1516.
Full textHedberg, Nils. "Sea cages, seaweeds and seascapes : Causes and consequences of spatial links between aquaculture and ecosystems." Doctoral thesis, Stockholms universitet, Institutionen för ekologi, miljö och botanik, 2017. http://urn.kb.se/resolve?urn=urn:nbn:se:su:diva-141009.
Full textAt the time of the doctoral defense, the following papers were unpublished and had a status as follows: Paper 2: Manuscript. Paper 3: Manuscript. Paper 4: Manuscript.
Salinas, Zapata Cristian C. "Seagrass soils as paleoenvironmental tools and biogeochemical sinks for management." Thesis, Edith Cowan University, Research Online, Perth, Western Australia, 2022. https://ro.ecu.edu.au/theses/2542.
Full textForselius, Ellen. "The Good, The Bad and The Seascape : Possible Effects of Climate Change in Tropical People and Ecosystems in the Western Indian Ocean Using a Gender Perspective." Thesis, Stockholms universitet, Institutionen för naturgeografi och kvartärgeologi (INK), 2013. http://urn.kb.se/resolve?urn=urn:nbn:se:su:diva-96064.
Full textShields, Ryan J. "Using Geospatial Tools to Assess Changes to Marine Ecosystems in Small Island Developing States Following Hurricane Disturbances: A Case Study of Dominica After Hurricane Maria." BYU ScholarsArchive, 2021. https://scholarsarchive.byu.edu/etd/8922.
Full textGeorge, Hugo. "Diving into Blue Carbon : A Review on Carbon Sequestration by Mangrove Forests, Seagrass Meadows and Salt Marshes, and Their Capacity to Act as Global Carbon Sinks." Thesis, Uppsala universitet, Institutionen för geovetenskaper, 2019. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-384028.
Full textUnder det senaste decenniet har intresset kring naturliga kolsänkors potential och roll i att mildra klimatförändringar ökat. Idag är det många forskare som arbetar med att beräkna mängden kol som olika ekosystem runt om världen kan lagra i sin biomassa och i jorden under dess rötter. Som en nykomling på den vetenskapliga arenan, har termen ’blue carbon’ blivit väl mottaget av forskare inom området. ’Blue carbon’ syftar på det kol som fixeras och lagras av de produktiva ekosystemen längs världens kuster. Termen refererar till kustbelägna våtmarker – så som mangroveskogar, saltträsk och sjögräsbäddar – och introducerades efter att den vetenskapliga världen erkänt deras imponerande potential som kolsänkor. Ny forskning tyder på att deras avancerade och vertikala rotsystem kan lagra mer koldioxid i marken än vad vanliga terrestra skogar kan. Genom att studera detta ämne försöker forskare att förstå hur dessa ekosystem kan hjälpa oss att avlägsna överskottet av koldioxid från atmosfären. Målet med denna uppsats är att utföra en litteraturstudie och analysera, samt sammanställa den nya forskningen om ’blue carbon’ som publicerats de senaste 10 åren. Uppsatsen kommer undersöka hur stor skillnad det är mellan de olika ekosystemen och vilka hot de står inför i framtiden. Dessutom kommer den undersöka ifall forskare kommit närmre i att enas kring förutsägelser om framtiden för ’blue carbon’, och hur dess roll i att mildra klimatförändringarna kommer se ut.
Mishra, Amrit Kumar. "Global change effects on seagrass ecosystem." Thesis, University of Plymouth, 2018. http://hdl.handle.net/10026.1/11296.
Full textBourque, Amanda. "Ecosystem structure in disturbed and restored subtropical seagrass meadows." FIU Digital Commons, 2012. http://digitalcommons.fiu.edu/etd/792.
Full textBurkholder, Derek A. "Top Down Control in a Relatively Pristine Seagrass Ecosystem." FIU Digital Commons, 2012. http://digitalcommons.fiu.edu/etd/799.
Full textSamiaji, Joko. "The ecology of a Zostera noltii bed ecosystem in the Solent." Thesis, University of Southampton, 2001. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.368150.
Full textDewsbury, Bryan. "The Ecology and Economics of Seagrass Community Structure." FIU Digital Commons, 2014. http://digitalcommons.fiu.edu/etd/1237.
Full textBessey, Cindy. "The Role of Teleost Grazers in a Relatively Pristine Seagrass Ecosystem." FIU Digital Commons, 2013. http://digitalcommons.fiu.edu/etd/911.
Full textNowicki, Robert J. "Effects of Catastrophic Seagrass Loss and Predation Risk on the Ecological Structure and Resilience of a Model Seagrass Ecosystem." FIU Digital Commons, 2016. http://digitalcommons.fiu.edu/etd/2994.
Full textSpivak, Amanda C. "Bottom-up and top-down controls on sedimentary ecosystem functioning in a seagrass habitat." W&M ScholarWorks, 2008. https://scholarworks.wm.edu/etd/1539616861.
Full textBuck, Eric L. "Ecosystem Restoration and Subtropical Seagrass Fishes: Insights into Salinity Effects from Habitat Selection and Preference Tests." Scholarly Repository, 2011. http://scholarlyrepository.miami.edu/oa_theses/239.
Full textWallner-Hahn, Sieglind. "Fishing for sustainability : Towards transformation of seagrass-associated small-scale fisheries." Doctoral thesis, Stockholms universitet, Institutionen för ekologi, miljö och botanik, 2017. http://urn.kb.se/resolve?urn=urn:nbn:se:su:diva-141052.
Full textAt the time of the doctoral defense, the following papers were unpublished and had a status as follows: Paper 1: Manuscript. Paper 4: Manuscript.
Heithaus, Michael R. "Habitat use decisions by bottlenose dolphins (Tursiops aduncus) and tiger sharks (Galeocerdo cuvier) in a subtropical seagrass ecosystem." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 2001. http://www.collectionscanada.ca/obj/s4/f2/dsk3/ftp04/NQ61648.pdf.
Full textWabnitz, Colette Catherine Chantal. "Sea turtle conservation and ecosystem-based management with a focus on green turtles (Chelonia mydas) and seagrass beds." Thesis, University of British Columbia, 2010. http://hdl.handle.net/2429/24239.
Full textMeyers, Alison Cheryl. "Depositional Dynamics in Seagrass Systems of Tampa Bay, FL: Influence of Hydrodynamic Regime and Vegetation Density on Ecosystem Function." Scholar Commons, 2010. https://scholarcommons.usf.edu/etd/1714.
Full textPotouroglou, Maria. "Assessing the role of intertidal seagrasses as coastal carbon sinks in Scotland." Thesis, Edinburgh Napier University, 2017. http://researchrepository.napier.ac.uk/Output/975386.
Full textBergmann, Nina [Verfasser]. "Do seagrasses feel the heat? : assessing the potential for microevolutionary change in a marine ecosystem engineering plant in response to global warming / Nina Bergmann." Kiel : Universitätsbibliothek Kiel, 2012. http://d-nb.info/1051824656/34.
Full textRoche, David C. "Trophic Ecology of Green Turtles (Chelonia mydas) From Dry Tortugas National Park, Florida." NSUWorks, 2016. http://nsuworks.nova.edu/occ_stuetd/430.
Full textDixon, Henry David John. "Effect of black swan foraging on seagrass and benthic invertebrates in western Golden Bay : a thesis presented in partial fulfilment of the requirements for the degree of Master of Science in Ecology, Massey University, Palmerston North, New Zealand." Massey University, 2009. http://hdl.handle.net/10179/1214.
Full textDarnell, Kelly Marie. "Understanding factors that control seagrass reproductive success in sub-tropical ecosystems." Thesis, 2014. http://hdl.handle.net/2152/26832.
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Liu, Ting-Chih, and 劉亭之. "Carbonate chemistry in seagrass and coral reef ecosystems of the Dongsha Atoll." Thesis, 2014. http://ndltd.ncl.edu.tw/handle/80233089059603007512.
Full text國立臺灣海洋大學
海洋環境化學與生態研究所
102
In this study, the carbonate parameters around the Dongsha Atoll (DA), including dissolved inorganic carbon (DIC), total alkalinity (TA), pH, partial pressure of CO2 (pCO2) and saturation state of aragonite (a), were thoroughly investigated in June (summer) and December (winter) 2013. The results show that the seagrass-dominant areas, including the small lagoon of the Dongsha Island (DI), and the north and west coasts of the DI, were sinks of atmospheric CO2 in both summer and winter. On the contrary, the coral reef-dominant area, i.e. the DA lagoon, was a source of atmospheric CO2.This difference can be attributed to that photosynthesis is the controlling process in the seagrass-dominant area, which can consume CO2 and thereby make the DI lagoon a sink of atmospheric CO2; meanwhile calcification is the predominant biogeochemical process in the coral reef-dominant area, which can release CO2 and thereby make the DA lagoon a source of atmospheric CO2. The spatial variations of the carbonate parameters around the DI lagoon and the DA lagoon were largely controlled by the coverage of seagrass and coral-reef, respectively. For the DI lagoon, when the seagrass coverage is higher, pCO2 and DIC are lower and pH and a are higher, and vice versa. For the DA lagoon, when coral reef coverage is higher, TA, pH and a are lower, and vice versa. Furthermore, the annual air-sea CO2 exchange flux in the seagrass-dominant areas was estimated to be -8.01±4.18 mmolC m-2 d-1. If the estimated annual CO2 flux is extrapolated to the entire DA seagrass bed, it could take up 288 ton C yr-1 from the atmosphere. This result is lower than the previous estimate of 788 ton C yr-1 based on seagrass productivity measurement. We suggest that this discrepancy may arise from the fact that a fraction of carbon produced by the seagrass were released back into the water column when detritus was decomposed, and thus cause an overestimate for atmospheric CO2 uptake. Finally, we suggest that if high a water in the seagrass-dominant area can flow into the coral reef-dominant area, it may be beneficial for the DA to cope with ocean acidification.
Ang, Shin-Jing, and 洪靜. "The effects of seagrass presence on coral reef ecosystems under ocean acidification and warming." Thesis, 2018. http://ndltd.ncl.edu.tw/handle/6mf262.
Full text國立中興大學
生命科學系所
106
Since the Industrial Revolution, the concentration of carbon dioxide (CO2) in the atmosphere has risen rapidly, resulting in ocean acidification (OA) and warming, which has threatened coastal ecosystems. Highly productive seagrasses usually live adjacent to or among coral reefs and can absorb CO2 in seawater, regulate the pH and the aragonite saturation state (ΩAr). The purpose of this study was to use coral reefs mesocosms to examine the effects of seagrasses on coral reef ecosystems under OA and warming. The net ecosystem production (NEP) was used to determine the functioning of the mesocosms. Three mesocosms without seagrass and three mesocosms with seagrass were designed to conduct four stages of OA and warming experiments. A non-acidified CO2 partial pressure of 400 ppm was used as control and 800 ppm was used as the OA scenario. The first stage was unacidified and 25˚C; the second stage was OA and 25˚C; the third stage was OA and warmed up to 28˚C; the fourth stage was OA and the temperature was raised to 31˚C. The results showed that under the OA scenario, the coral calcification rates with seagrasses were higher in OA (25˚C) and OA (28˚C) than without seagrasses. In addition, the OA scenario proliferated the macroalgae, and the growth rate of macroalgae without seagrasses was higher than that with seagrasses. Therefore, OA (25˚C) significantly increased the NEP of the mesocosms without seagrasses, but OA had no effect on the NEP of the mesocosms with seagrasses. Ecosystem respiration (ER) increased gradually with increasing temperature under the scenario of OA, but gross primary production (GPP) in OA (28˚C) reached the maximum, then dropped in OA (31˚C). Due to the high temperature environment of 31 ̊C, the growth rate of macroalgae reduced and the mortality increased. The mesocosms without seagrasses dropped sharply at OA (31˚C) by 0.93±0.22 g O2 m-2 d-1, while the mesocosms with seagrasses decreased moderately by 0.68±0.13 g O2 m-2 d-1. Under the condition of OA and warming in the future, seagrasses can maintain the calcification rate of corals. Seagrasses can inhibit the growth of macroalgae, caused the magnitude of NEP declined less and maintain the stability of coral reef ecosystems at a high temperature of 31˚C.
Rappe, Rohani Ambo. "Environmental impacts of habitat fragmentation and heavy metal contamination on estuarine seagrass communities." Thesis, 2007. http://hdl.handle.net/1959.13/1312589.
Full textSeagrasses are generally known for their significant role in marine and estuarine ecosystems. The growth in human population along the coastal regions, where the seagrass live, makes them very vulnerable to the human-induced disturbances. Large-scale seagrass decline has been reported worldwide due to this problem. There is an evident need to monitor seagrass population to predict future changes and to protect coastal ecosystems from further degradation. The decline of seagrass beds results in their fragmentation and appearance of smaller patches of seagrass isolated from each other, The first goal of this thesis is to study how fragmentation of seagrass beds influence their role in the ecosystem. This study focused on how fragment size and its distance from the main bed influence abundance of mobile epifauna associated with seagrass. Artificial seagrass units were constructed to mimic the seagrass fragmentation at a small scale. The result from this experiment suggested neither fragment size nor on-patch location (edge vs middle) adequately account for variation in the abundance of seagrass-associated epifauna. The distance from large beds of seagrass was important, however. Fragments placed far away from the natural seagrass were colonized to a grater degree than the fragments placed near seagrass beds. Large fragments were also colonized more than the small ones at the furthest distance from natural beds. Thus, fragmentation does not necessary lead to decease in epifaunal abundances. The small isolated patches may serve as refuge sites of the marine organisms. The second part of the thesis specifically deals with the effect of heavy metal contamination on seagrass and associated fauna. Despite the well-publicised issue of metal contamination of highly urbanised estuaries and its effect on seagrasses, this is the first study that assessed the contamination effect on the seagrass community using a range of bioindicators and biomarkers in order to obtain an integral picture of the contamination effect. It was found the seagrass, Zostera capricorni accumulated high concentration of heavy metals and provide a good correlation between the concentration in their tissues and in the sediment. Moreover, there was no evidence of impact on the seagrass biomass, shoot and leaf density. Thus, this seagrass can be used as a good bioindicator because of the above reasons, and also they are sedentary and abundant in the polluted site, which makes them easily available for sampling. The abundance of epifaunal organisms associated with the seagrass was used as a bioindicator at the community level. Only gastropods decreased in abundance in the contaminated site in spring (when the number of seagrass fauna generally higher), and this might potentially be a good bioindicator in this system. Shell dimension and fluctuating asymmetry were used as biomarkers for this purpose. It was found that a bivalve associated with seedgrass, the ark cockle Anadara trapezia, in the polluted location (Cockle Baby) showed distinct morphological characters compared to the ones in unpolluted locations. The cockles were bigger, heavier and had bigger shell-height/shell-length ratios, but appeared much less abundant, which is contradicted with historically high abundance of this species in this location (Cockle Bay). Moreover, the cockles exhibited higher shell asymmetry compared to the ones in unpolluted locations. Leaf dimensions and leaf asymetry of seagrasses,
Chu, Hui-Chuan, and 朱慧娟. "Comparison of carbon chemistry between summer and winter in two seagrass ecosystems at Dongsha Island." Thesis, 2018. http://ndltd.ncl.edu.tw/handle/mu5xc5.
Full text國立臺灣海洋大學
海洋環境與生態研究所
106
Seagrass meadow ecosystems occupy only ~0.2% of the ocean, however they play a disproportional role in the ocean carbon cycles. Seagrass meadows may contribute ~10% of the burial of organic carbon in the ocean. Meanwhile, the high primary productivity is beneficial for increasing pH and carbonate saturation(ΩAr). Hence seagrass ecosystem is recognized as being helpful against ocean acidification(OA) and increase of atmospheric carbon dioxide. To clarify these abilities whether exist in seagrass meadow at Dongsha Isaland, this study conducted a thorough diurnal investigation on the carbon chemistry in January(winter) and August(summer) 2016 at two seagrass meadows around the Dongsha Island: one is in the inner lagoon seagrass ecosystem and the other is on the north shore seagrass ecosystem. In the inner lagoon, the results demonstrated that DIC was lower in winter than summer (1741±94 < 2137±203 μmol/kg); TA was higher in winter than summer (2567±50 > 2517±169 μmol/kg); pH was higher in winter than summer (8.63±0.09 > 8.22±0.16); pCO2 was lower in winter than summer (64±19 < 379±149 μatm) and ΩAr was higher in winter than summer (8.8±0.8 > 4.8±1.1). On the north shore, DIC was lower in winter than summer (1962±218 < 2003±96 μmol/kg); TA was higher in winter than summer (2365±63 > 2271±74 μmol/kg); pH was higher in winter than summer (8.18±0.28 > 8.04±0.19); pCO2 was lower in winter than summer (378±355 < 627±313 μatm) and ΩAr was higher in winter than summer (4.5±1.8 < 3.2±1.1). These results indicated that inner lagoon seagrass bed in winter had the strongest ability against OA, because of the highest value of pH and ΩAr. Besides, the extremely low seawater pCO2 render the inner lagooon to be a strong sink of atmospheric carbon dioxide. According to the stoichiometric analysis of DIC and TA plot, these abilities were derived from the restricted hydrodynamic environments and different dominant biogeochemical process. Due to the restricted hydrodynamic environments, the effect of biogeochemical process was more evident in the inner lagoon than the north shore. In the winter, the dominant biogeochemical process was photosynthesis, that resulted in decreasing DIC and increasing TA, which leading to the increasing pH and ΩAr and the decreasing pCO2. In the summer, the dominant biogeochemical process was sulfate reduction, that resulted in elevated DIC and TA, which led to the less increasing pH and ΩAr.
Mishra, Amrit Kumar. "Global change effects on seagrass ecosystem." Doctoral thesis, 2017. http://hdl.handle.net/10400.1/10808.
Full textForam investigados efeitos a curto e longo prazo do CO2 no metabolismo do carbono das ervas marinhas. As pradarias de Cymodocea nodosa, expostas durante um longo período a CO2 elevado, no vento vulcânico de CO2 ao largo da Grécia e da Itália, foram investigadas utilizando técnicas de reconstrução populacional. O Crescimento, a morfometria, a densidade, a biomassa e a estrutura etária foram afetados pelo alto teor de CO2. A razão entre a biomassa da parte aérea e parte subterrânea de C. nodosa foi superior nos ventos de CO2. A população de C. nodosa cresceu mais rapidamente, mas a longevidade das plantas foi menor nos ventos de CO2. O recrutamento atual (ano amostrado) da erva marinha foi maior perto das infiltrações. As taxas de carbono - azoto (% PS) nas folhas e a produção foliar anual de C. nodosa foram maiores nos ventos de CO2. Os elementos (Fe e Cd, Cu, Co, Hg, Pb, Mn, Ni e Zn) foram analisados a partir de sedimentos e das várias partes de P. oceanica e C. nodosa dos ventos de CO2 ao largo da Grécia e da Itália. O Índice de Poluição do Quociente das Diretivas de Qualidade do Sedimento indicou que o nível de elemento é mais alto nos sítios de CO2 do que nos de referência com possibilidade de impactos biológicos moderados a adversos. A concentração de elementos nos sedimentos e nas várias partes das plantas foi maior nos sítios de CO2. Foi observada uma maior acumulação de elementos nas das ervas marinhas. A produção liquida da comunidade (NCP) e a respiração da comunidade (CR) das populações intertidais de Z. noltei e de zonas não sedimentadas foram medidas sob condições expostas ao ar e enriquecidas com CO2, sazonalmente. O NCP de Z. noltei e dos sedimentos comunidade foi mais elevado em concentrações elevadas de CO2 do que as condições naturais, para um intervalo de luz semelhante. O NCP de Z. noltei foi maior do que no sedimento da comunidade nas estações de verão e inverno, em condições enriquecidas com CO2. A CR de ambas as comunidades foi menos afetada em condições enriquecidas com CO2. O ponto de compensação para a luz de Z. noltii foi menor do que o dos sedimentos das comunidades na estação do verão com elevados níveis de CO2. A produção comunitária sazonal de Z. noltii foi maior do que no sedimento das comunidades. O efeito significativo da luz no NCP foi observado a partir do modelo de regressão linear.
Aragones, Lemnuel V. "Dugongs and green turtles: grazers in the tropical seagrass ecosystem." Thesis, 1996. https://researchonline.jcu.edu.au/44323/1/44323-aragones-1996-thesis-volume-1.pdf.
Full textScott, Abigail Lucy. "The role of herbivores as ecosystem engineers in Great Barrier Reef seagrass meadows." Thesis, 2020. https://researchonline.jcu.edu.au/69096/1/JCU_69096_Scott_thesis_2020.pdf.
Full textChen, Ying-Hsuan, and 陳穎萱. "Effects of seagrass and ocean acidification on net ecosystem calcification in coral reefs:a mesocosm approach." Thesis, 2018. http://ndltd.ncl.edu.tw/handle/tgva4n.
Full text國立臺灣海洋大學
海洋環境與生態研究所
106
Since the beginning of industrial revolution, more than one quarter of anthropogenic CO2 emissions have been absorbed into the oceans, driving down ocean pH and aragonite saturation state (ΩAragonite), a process known as ocean acidification (OA). The coral reef is a sensitive ecosystem to OA, and previous studies show that OA has a negative impact on the calcification rate for most of coral species. These earlier studies have mainly focused on individual species and/or community-level responses to OA. However, to better predict OA impact on ecosystem level, it needs to consider the interactions among the biological communities. Moreover, recent studies also suggest that seagrass meadows could have potential in serving as chemical “refugia” for the associated coral reefs facing future OA. This potential derives from their ability to modify seawater carbon chemistry through high levels of primary productivity. Therefore, the purpose of this study is to examine if seagrass could be beneficail for coral reef calcification at present and future OA scenarios using mesocosm approach. In this study, we monitored the variations of carbon chemistry parameters (DIC, TA, and pH) in 6 tanks of mesocosm under present (stage 1) and OA (stage 2) conditions, in which 3 tanks with seagrasses (experimental group), and the other three without seagrass (controlled group). Results show that net ecosystem production (NEP) under the present condition in the controlled and experimental groups is 4.76 and 5.26 μmolC kg-1 day-1, respectively, and there is no statistically significant difference between the two groups, suggesting that NEP from algae would increase in the controlled group due to the lack of competition from seagrass. The average net ecosystem calcification (NEC) in the first and second stages is 5.23 and -1.12 μmolC kg-1 day-1, respectively, the fomer is statistically significant higher than the latter. This suggests that OA has a negative impact on the NEC of the coral reef ecosystem no matter with segrass or not. Fianlly, by compiling NEC and ΩAragonite data of the present and previous studies, we suggest that the threshold value of ΩAragonite is approximately 1.82, at which NEC will switch from positive to negative. Assuming this threshold value of ΩAragonite, the simulated result shows that coral reef in tropical will begin to decline at a atmopsheric pCO2 level of approximatively 882 μatm.
Medina, Israel. "Characterization of a Karst Coastal Ecosystem in the Mexican Caribbean: Assessing the Influence of Coastal Hydrodynamics and Submerged Groundwater Discharges on Seagrass." Thesis, 2011. http://hdl.handle.net/1969.1/ETD-TAMU-2011-05-9060.
Full textSchmidt, Allison Louise. "The role of marine macrophytes in providing essential ecosystem services: Their relative contribution and how services are impacted by eutrophication." 2012. http://hdl.handle.net/10222/15840.
Full textGrech, Alana. "Spatial models and risk assessments to inform marine planning at ecosystem-scales: seagrasses and dugongs as a case study." Thesis, 2009. https://researchonline.jcu.edu.au/8195/1/01front.pdf.
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