Doctorado en Ciencias del Mar
URI permanente para esta colecciónhttps://repositorio.unal.edu.co/handle/unal/82551
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Ítem Modelo de valoración sistémica desde la evaluación integral del manglar urbanizado del caño Juan Angola, Cartagena de Indias(Universidad Nacional de Colombia, 2019) Sánchez Rubio, Luis Fernando; Saldarriaga Isaza, Carlos AdriánEste estudio muestra la falta de valoración de la naturaleza durante tres momentos de la historia de Cartagena de Indias, durante la construcción de la ciudad con material de origen de arrecifes coralinos; la apertura del canal del Dique hacia la bahía, destruyendo el ecosistema de coral; y durante el crecimiento actual de la zona urbana sobre los humedales de la ciudad, destruyendo el manglar, aspecto medido con el análisis espaciotemporal comparando aerofotografías del área de estudio, representativa de la ciudad: el caño Juan Angola. El estudio profundiza sobre la posible relación de la no valoración de la naturaleza con la problemática socio ambiental de la ciudad actual, encontrando que la desigualdad social, está relacionada con un desarrollo urbano desmedido exacerbado por la corrupción al momento de gobernar, que responde a intereses de las élites, no al bien común, concluyendo que Cartagena es una ciudad fragmentada y dual en crisis ambiental y de gobernabilidad. Ante estos hechos, se midieron indicadores de calidad ambiental y se caracterizó un grupo de líderes del área de estudio, como línea base, construyendo y aplicando con ellos el Modelo Tríada de gobernanza, con resultados medibles por indicadores de impacto, concluyendo que la valoración del sistema manglar tiene el potencial para soportar el Desarrollo Sostenible (DS) para la ciudad basado en ecosistemas, como lo explica el diagrama de ingeniería de la gobernanza que presenta la posibilidad de escalar la experiencia a otras áreas del mismo sistema o exportarlo con los ajustes requeridos a otras regiones. (Tomado de la fuente)Ítem Seasonal patterns of biogeochemical conditions of the water column and sediment - water interface near the submarine outfall in the Santa Marta Bay, Colombian Caribbean.(Universidad Nacional de Colombia, 2020-06) Arroyave Gómez, Diana Marcela; Toro Botero, Francisco MauricioThe biogeochemical conditions at the sediment-water interface and along the water column near the discharge of the Santa Marta sewage outfall (SMSO) were studied during the non upwelling (NUPW) and upwelling (UPW) seasons by sedimentary properties and benthic metabolism measurements, as well as, by the implementation of a coupled 3D hydrodynamic-ecological model (AEM3D). Sediment properties (organic matter quantity, C, N and P pools and δ13C, δ15N and redox potential) and benthic metabolism (aerobic respiration, denitrification, nitrate ammonification and nutrient recycling) were analyzed in four stations located in the proximity and 100, 750 and 1800 m far from the untreated wastewater effluent discharge in both seasons in the Santa Marta Coastal Area (SMCA). From each site, sediment cores were collected between 20 and 30 m depth. Then, the nutrient fluxes were measured in the laboratory via dark incubations; sequentially to fluxes denitrification and dissimilative nitrate reduction to ammonium were measured via the r-IPT (Isotope Pairing Tecnnique). The results indicate that the sediments trace the impact of the outfall (at 750 m and 1800 m with a contribution of terrestrial organic carbon of ~ 40 and ~ 20%, respectively). The results suggest significantly higher sediment oxygen demands (SOD) in the outfall vicinity, as well as a suppression of denitrification and increments in the ammonia nitrogen release through disassimilatory reduction of nitrate to ammonium (DNRA), which was increased during the UPW season. On the other hand, AEM3D model was applied to analyze the seasonal variations of water physico-chemical and biological parameters in SMAC under two different nutrient and organic matter loads from wastewater outfall (flow-rate of 1.0 m3 s-1 and 2.5 m3 s-1) and along the NUPW and UPW season. The model was set up, calibrated and validated based on benthic metabolic measurements carried out within the simulation period, satellite–derived chlorophyll-a (Chl-a) and sea surface temperature (SST) maps, HYCOM database and field and literature water quality data. The model was able to reproduce the magnitude and timing of complex dynamics and fast transitions of temperature, nutrients, and phytoplankton, including the time and duration of stratification and mixing periods during the NUPW and UPW seasons. The model was also able to capture the effect of fertilization from upwelling and from the outfall plume. The wind field was the main driver of nearshore hydrodynamics and the outfall plume dispersion. The shortest average residence times of the outfall plume (3.7 ± 0.4 days) corresponded to the period of highest upwelling intensity. Temperature, light intensity and nutrients were the factors that limited phytoplankton growth. The plume concentrations of TOC, TP and PO43- increased slightly under two scenarios of different wastewater loading. The phytoplankton growth was limited in both NUPW and UPW seasons due to large changes in temperature and advection and mixing in the coastal area, resulting in large dilution of nutrient loads. Wide and fast changes in the temperatures and the highly energetic environment uncoupled phytoplankton growth and nutrient supply in the benthic and pelagic compartments. The model proved to be a reasonably reliable research and management tool to predict nutrient and phytoplankton dynamics, and to analyze the individual role of different inputs during NUPW and UPW seasons. The main model outputs suggest limited impact of the nutrients from the outfall and from upwelling to the chemical and biological quality of the water in the SMCA. However, sediment analyses revealed the occurrence of a pronounced organic impact, altering sediment biogeochemical dynamics and suggest maintaining this system continuously monitored and studied, via combination of experimental activities, satellite-based monitoring and modeling approaches. This seems particularly important due to increasing anthropogenic pressures on the coastal area and on watersheds and to ongoing global changes affecting climate, wind intensity, water temperature and mixing rates.Ítem Analysis of the Kelvin-Helmholtz instability in seagrass-oscillatory flow interaction(2019) Cáceres Euse, Alejandro; Orfila foster, Alejandro (Thesis advisor)The aquatic vegetation is ubiquitous worldwide, from low temperature areas to tropical shallow coastal zones (Van Der Heide et al., 2007). These ecosystems provide a productive life cyle being the habitat for many marine animal species (Marion et al., 2014). At the coastal region, the aquatic vegetation (seagrass) attenuates the currents, dissipates the wave height and stabilises the coastlines (Maxwell et al., 2017; Pinsky et al., 2013) being considered as a soft system to reduce the risk of ooding and erosion under sea level rise and extreme wave events (Ondiviela et al., 2014). Based on the above described services, estimations of economical annual values provided by the aquatic vegetations is over $10 trillion (Nepf, 2013). Control _eld studies such as those by Schanz et al. (2002); Schanz and Asmus (2003) demonstrate the interdependence between the hydrodynamic and biological processes, since there is a cascading e_ect in which for a speci_c ow conditions, di_erent species can live and proliferate within the seagrass meadows or be washed away, depending on the energetic wave conditions and seagrass density. Regarding the interaction between the submerged seagrass and the surrounding ow, it is well known that the presence of the seagrass canopies attenuate the momentum by the work done on the ow by the stems (Finnigan, 2000). The e_ects in the velocity _eld can be di_erentiated and thus studied in terms of scales; 1) processes with spatial scales of the order of the stem diameter or spacing between stems; and 2) processes with scales of the order of the drag length scale. The turbulent structures at the scale of the stems are called wake scales and are produced by the shadow zone downstream the stems (Nepf, 2012; Zhang et al., 2018). Turbulent processes at the drag length scale are governed by the density of the canopy and the ow dynamics (Nepf, 2012). These processes modulate the water renewal between the water inside and above the canopy and the amount of suspended sediments along the water column (Luhar and Nepf, 2013). The turbulent processes at the drag length scale can be analysed as a plane mixing layer by two co-owing streams that present a shear layer at the top of the canopy (Raupach et al., 1996). This shear-layer-ow is characterized by an inexion point in the velocity pro_le (two water bodies moving at di_erent velocities), responsable for the vertical mass exchange at the top of the canopy (Ghisalberti and Nepf, 2009). The shear layer facilitates the generation of Kelvin-Helmholtz instability type vortex (Ghisalberti and Nepf, 2002). The Kelvin-Helmholtz type vortex has been widely studied in steady ows (Raupach et al., 1996; Finnigan, 2000; Ghisalberti and Nepf, 2002; Nepf, 2012; Mandel et al., 2017), characterizing its e_ect on the seagrass movement, the Reynolds stresses, the sediment distribution, the vertical mixing and the free surface. However, the formation and e_ect of Kelvin-Helmholtz type vortices in the wave oscillatory ow is still far to be completly understood. Indeed, it is still not clear which are the dominant terms in the Navier-Stokes equations for the oscillatory-seagrass-ow interaction. Ghisalberti and Schlosser (2013) reported some \`necessary" conditions in the ow in order to produce Kelvin-Helmholtz instabilities; Abdolahpour et al. (2017) analysed a steady current released by the presence of the shear layer and its relation with the shear layer magnitude and Abdolahpour et al. (2018) used the seagrass-steady-ow interaction formulation of Ghisalberti and Nepf (2002) to estimate the Kelvin-Helmholtz frequency range in oscillatory ows. The evolution of vortices downstream submerged structures in oscillatory dominant ows is assumed to be dissipated by the viscosity and the e_ects on the wave breaking process have not been yet analysed. Indeed, a theoretical model to solve the Kelvin- Helmholtz instability modes as a function of the free surface and a general characterization of the turbulent spectra is an open question that will provide new insights in order to improve models and simulations of relevant hydrodynamic processes at coastal scale. The aim of this Thesis is to understand the relation between the free surface frequency and the Kelvin-Helmtholtz instability modes in seagrass-oscillatory-ow interaction. For this, I will _rst analyze the e_ects of a vortex by an isolated submerged stem interacting with a surface wave. Then, I develop an analytical model to determine the dominant terms in the momentum equation in seagrass-oscillatory-ow interaction. Finally I close the scienti_c question by solving the Kelvin-Helmholtz instability modes in seagrass-oscillatory ow interaction as a function of the free surface wave applying the Piecewise method to a simpli_ed velocity pro_le. This thesis is structured as follows. Chapter 2 analyses the e_ects of backwards wave breaking process induced by a strong transport of mass in a vortex produced by an isolated submerged stem. In chapter 3, a simpli_ed seagrass-oscillatory-ow model is developed by dimensional analysis of the Navier-Stokes equation. Here, some reference variables are de_ned according to the free surface wave parameters . The vali dation of the simpli_ed model is performed against experimental data from a ap type wavemaker system and a random seagrass distribution. Finally, chapter 4 presents a theoretical model for the Kelvin-Helmholtz instability modes as a function of the incoming free surface wave. The model applies the piecewise linear method to the Rayleigh's equation in an ideliazed vertical velocity pro_le. It is important to remark that this thesis is composed by three papers: Chapter 2 has been published in the Ocean Engineering Journal, Chapter 3 is in _nal revisión for the Experiments in Fluids Journal and Chapter 4 is under review for the Journal of Fluid Mechanics.Ítem Evaluación de praderas de pastos marinos como reservorios de carbono: un caso de estudio en el Caribe colombiano(2018-01-25) Guerra Vargas, Luis Alberto; Zimmer, Martín (Thesis advisor)Las praderas de pastos marinos son ecosistemas costeros, y son muy eficientes en la captura y almacenamiento de carbono orgánico (Corg) en su biomasa viva, y en la materia orgánica debajo de su sustrato donde permanece reservado por décadas o inclusive siglos. Si bien existe evidencia que sustenta la función de almacenamiento en diferentes tipos de praderas, esta ha sido poco estudiada al interior de una laguna arrecifal y mucho menos en aguas oceánicas y oligotróficas del mar Caribe. En la isla de San Andrés, en el caribe suroccidental, se encuentra una laguna arrecifal con 314 ha de praderas de pastos marinos dominados en un 79% por la biomasa de Thalassia testudinum Banks y Sol. ex K.D.Koenig. Con el fin de evaluar los contenidos de Corg en las praderas, se emplearon métodos que consideran las variaciones observadas entre Sitios al interior de la laguna y su grado de exposición al oleaje. Los Sitios más expuestos presentaron menor biomasa viva, menor densidad de vástagos y menor biomasa de raíces con respecto a rizomas, y menor contenido de lodos y de materia orgánica en el sustrato. Sin embargo, el contenido de Corg fue similar entre las biomasas de los Sitios. El inventario de carbono debió hacerse por compartimientos, y en el compartimento de la biomasa viva sobre el sustrato (314 ha) se estimó 47.1 ± 9.4 Mg de Corg (CI 95%) y en la de debajo 530.7 ± 103.6 Mg de Corg, durante el tiempo de lluvias del 2016 (n= 36). El inventario fue significativamente mayor en tiempo seco (p-valor 0.05). El carbono orgánico depositado en el primer metro de sedimentos fue 37 veces mayor al de la biomasa viva. Y a su vez, el carbono inorgánico de los sedimentos es 16 veces mayor que el orgánico. Finalmente, se recomiendan nuevos estudios que evalúen el crecimiento de la biomasa de raíces y rizomas, la disponibilidad de nutrientes en las aguas en el sustrato y los rasgos funcionales de T. testudinum como respuesta a cambios en los factores del entorno que modulan su producción.Ítem Salinity gradient energy harnessing at river mouths. From theoretical to extractable resources(2015-02-17) Alvarez Silva, Oscar AndrésAbstract: salinity gradient energy (SGE) is the clean and renewable energy that can be obtained from controlled mixing of two water masses with different salt concentration. River mouths, where fresh water mixes with saline seawater, are manifest locations for harnessing SGE, since provide the sought salinity gradients and abundant water resources worldwide. Most of the research in SGE has been focused on improving the performance of the energy generation techniques; however, as these techniques reach higher stages of development, more attention must be paid to the challenges that harnessing SGE from natural systems will bring. This thesis addresses persistent gaps on the research of suitability, available potentials and extractable resources of SGE at river mouths. These topics are approached at global and local scales from three strategies: hydrodynamic modelling of temporal and spatial variability of the salinity structure of river mouths; analysis of databases of variables and resources related with SGE at river mouths; and parameterization of the physical relations among environmental forcings, stratification and SGE potentials. The results of this research show that only river mouths with mean tidal range lower than 1.2 m are suitable locations to generate SGE; 20% of the mean discharge of rivers may be extracted for SGE generation; harnessing SGE at river mouths is very reliable with average capacity factor of 84%; and 625 TWh/y of SGE are extractable from river mouths worldwide considering site-suitability and environmental constraints. But beyond these numbers, most important contributions of this thesis are: development of the concept of site-specific potential for more precise assessment of the SGE resources at river mouths; description of the relation between stratification and SGE potential; classification of river mouths according to the suitability for harnessing SGE; mapping of the global distribution of available SGE resources; proposing a methodology to assess extractable SGE resources from particular systems; and overall discussion of physical and environmental constraints for SGE generation at river mouths. Together, these findings constitute a significant progress in the study of opportunities of harnessing SGE at river mouths in the upcoming futureÍtem Dynamics of the continental slope demersal fish community in the Colombian Caribbean – Deep-sea research in the Caribbean(2015-04-13) Polanco Fernández, AndreaAbstract: Nowadays, the limited knowledge of marine biodiversity in the deep-sea faces increasing human exploration interest of this environment in the Colombian Caribbean (e.g. recent hydrocarbon exploration activities), wich makes it a national problem. This scenario requires a better understanding of the biodiversity, ecology, and biogeography of species that live in the territorial and adjacent waters of Colombia towards an adequate management of resources. The deep-sea demersal fish community is one of the main faunal groups that can be used to track aggregations of biodiversity in deep-sea ecosystems. The deep-sea waters of the Colombian Caribbean have been investigated by some foreign and national expeditions during the last five decades. Since then, the information obtained has been stored in a wide array of cruise reports and “gray” literature. With the main goal of identifying aggregations of biodiversity in terms of deep-sea fish species numbers and the physical and biological factors that may cause certain spatial distribution patterns. The current thesis summarizes the available information to produce a comprehensive inventory of demersal deep-sea fishes present in the Colombian Caribbean. Their structural patterns are analyzed in terms of composition and distribution through a multivariate regression tree (MRT) analysis to identify different environmental factors that may be influencing fish distributions. Hypotheses of correlation between the distributional patterns and the bathymetric (200 to 980 m), geographic (east-west), and topographic (bottom landscape) ranges are tested. A spatial analysis of the number of species per station under the light of the available environmental information and recent findings of deep-sea ecosystems in Colombia was made as well. As a result of this, 343 species of deep-sea demersal fishes included in 26 orders and 92 families are identified for the Colombian Caribbean. Six fish assemblages were found in the continental slope mainly characterized by depth and geographical location. Based on the outcomes of the spatial analyses, three areas of aggregations of biodiversity of fish fauna were identified between 300 and 500 m depth in the Colombian Caribbean continental waters and one on insular waters. The continental offshore areas identified are located close to the sites where deep-sea reef ecosystems were reported before.The results support the idea of the Caribbean territorial waters of Colombia as an area with high values of deep-sea fish species compared to other regions in the western Atlantic coast. The structural data suggest a northeastern region that shows the highest concentration of species richness and abundances between the lower part of the upper slope and the upper part of the middle slope (275 – 602 m). Finally, the aggregations of fishes found add support to the previous stated evidence of the presence of deep-sea reefs ecosystems in the Colombian Caribbean located between the continental shelf break and the middle slope.