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Spatial, temporal and behavioral patterns of marine protists

Other TitlesPatrons espaials, temporals i de comportament dels protistes marins
AuthorsRodríguez Giner, Caterina
Issue DateSep-2017
PublisherUniversidad Politécnica de Cataluña
Abstract[EN] The oceans are microbial-dominated ecosystems, where protists (single-celled eukaryotes) play fundamental roles performing multiple functions as primary producers, consumers, decomposers as well as trophic linkers in aquatic food webs. Due to their ecological relevance, it is important to characterize protist communities along temporal and spatial gradients to understand their biogeography and dynamics. This will allow us to infer the processes that drive the assembly of protist communities. In this dissertation, we focused in the study of natural protists communities aiming to understand their distributions and responses within different dimensions. We first focused in the temporal dimension, analyzing the dynamics of pico- and nanoeukaryotic communities, aiming to characterize the diverse strategies of their members and to determine seasonality. We identified an annual seasonal pattern in the protist community as well as in several composing taxa. Then, we addressed the spatial dimension, analyzing the changes in community composition along the water column in 13 stations distributed in the global ocean, exploring also the vertical variation in the relative metabolic activity of different taxa. Our results showed a clear vertical stratification of the community and indicated that the mesopelagic layer is the region where most taxonomic groups were more metabolically active. Another aim of this thesis was to explore the response of natural protists to chemical signals. The ocean is a complex ecosystem with nutrients heterogeneously distributed along several patches, so there may be a lot of chemical gradients promoting diverse responses on marine microbes. For that purpose, we performed chemotactic experiments to identify individual responses towards different attractants within a natural protist community. The experimental results showed a preferential response towards some of the tested chemical cues, mainly bacterial exudates. Finally, since studies on microbial diversity generally use the relative abundances of phylotypes in a given sample, we explored the relationship between the latter relative abundances to cell abundances in several chosen taxa. In sum, this dissertation determines temporal and spatial patterns in protists communities as well as chemotactic preferences in different taxa, contributing to broaden our understanding of the structuring processes operating across temporal, spatial and behavioral dimensions in the protist world
[ES] Los océanos son ecosistemas dominados por microorganismos. Entre estos, los protistas (organismos eucariotas unicelulares) tienen un papel fundamental en diversas funciones imprescindibles para el ecosistema, principalmente como productores primarios y depredadores, pero también tienen un papel clave en la red trófica microbiana. [...]
[CAT] Els oceans són ecosistemes dominats per microorganismes. Entre ells, els protistes (organismes eucariotes unicel·lulars) tenen un paper fonamental en diverses funcions imprescindibles per al sistema marí, principalment com a productors primaris i depredadors, i per tant juguen un paper clau en les xarxes tròfiques marines. [...]
DescriptionMemoria de tesis doctoral presentada por Caterina Rodríguez Giner para optar al grado de Doctora en Ciencias del Mar por la Universitat Politècnica de Catalunya (UPC), realizada bajo la dirección del Dr. Ramon Massana y el Dr. Ramiro Logares del Institut de Ciències del Mar (ICM-CSIC).-- 223 pages
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