<p>The timing of the spring phytoplankton bloom in the subpolar North Atlantic Ocean has important consequences for the marine carbon cycle and ecosystems. There are currently several proposed mechanisms to explain the timing of this bloom. The conventional theory holds that the bloom begins when the ocean warms and the seasonal mixed layer shoals in the spring, decreasing the depth to which phytoplankton are mixed and increasing the light available to the population. Recent work has attributed the beginning of the bloom to decreases in turbulence within the upper ocean, driven by the onset of positive heat fluxes or decreases in the strength of local winds. Other studies have focused on the increase in the seasonal mixed layer in the winter as a driver of changes in ecosystem interactions and a control on the spring bloom. Finally, submesoscale eddies, occurring as a result of lateral density gradients, have been proposed as a stratification mechanism that can create phytoplankton blooms prior to the onset of ocean surface warming.</p><p>This dissertation critically examines and compares the proposed theories for the initiation of the spring bloom and draws on these theories to propose a new framework: that blooms begin when the active mixing depth shoals, a process generally driven by a weakening of surface heat fluxes and consequent shift from convective mixing to wind-driven mixing. Using surface forcing data, we develop a parameterization for the active mixing depth from estimates of the largest energy-containing eddies in the upper ocean. </p><p>Using in situ records of turbulent mixing and biomass, we find that the spring phytoplankton bloom occurs after mixing shifts from being driven by convection to being driven by wind, and that biomass increases as the active mixing depth shoals. Using remote sensing data, we examine patterns of bloom initiation in the North Atlantic at the basin scale, compare current theories of bloom initiation, and find that the shoaling of the active mixing depth better predicts the onset of the bloom across the North Atlantic subpolar basin and over multiple years than do other current theories. Additionally, using a process study model, we evaluate the importance of submesoscale eddy-driven stratification as a control on the initiation of the spring bloom, determining that this mechanism has a relatively minor effect on alleviation of phytoplankton light limitation. Finally, we describe potential techniques and tools to examine whether interannual variability in the active mixing depth acts as a control on variability in the timing of the spring bloom.</p> / Dissertation

Marine ecosystem-based management requires end to end models, which are models capable of representing the entire ecosystem including physical, chemical and biological processes, anthropogenic activities, and multiple species with different sizes, life histories and from different trophic levels. To adequately represent ecosystem dynamics in shallow coastal regions, end-to-end models may need to include macrobiota species (wild and aquacultured) and may have to allow feedbacks (i.e. two-way coupling) between macrobiota and planktonic ecosystem dynamics. This is because the biomass of macrobiota can locally exceed the biomass of plankton, thus influencing the distribution of planktonic ecosystem tracers and altering the overall food web structure. Here, I describe a hybrid (Eulerian/Individual-Based) ecosystem framework, implemented in the Regional Ocean Modeling System (ROMS), a state-of-the-art 3-D ocean circulation model. The framework was applied to a model of a synthetic embayment containing seagrass, rockweed and kelp beds, a wild oyster reef, a mussel ranch and a fish farm. I found that two-way coupling is essential to reproduce expected spatial patterns of all variables and to conserve mass in the system. I also developed a shellfish ecophysiology model (SHELL E) and compared its results against water samples collected over 5 years in Ship Harbour, a fjord with mussel aquaculture in Nova Scotia, Eastern Canada. Also, from a high-resolution bio-optical survey of the fjord, I found that mussels decrease phytoplankton biomass inside the farm, but also cause a bloom of phytoplankton outside the farm. Using ROMS/SHELL-E, I determined that the increase of phytoplankton around the farm is caused by the waste products of the farmed bivalves, which have a fertilization effect, enhancing phytoplankton production outside the farm during nutrient-limited and light-replete conditions (i.e. late spring to late fall in Ship Harbour). The main conclusion of this thesis is that—in shallow coastal regions—ecosystem models must represent bilateral interactions between macrobiota and physical-planktonic dynamics, in a spatially-explicit setting, to adequately represent mass flows and ecosystem dynamics. The hybrid end-to-end modelling system provides a computationally efficient framework for describing these interactions and, through careful comparisons against observations, can be a powerful tool to test hypotheses and generate insights into coastal ecosystems.

<p> The interaction of biological and physical processes has resulted in distinct morphological and biological zonation across the Subarctic macrotidal tidal flats at the head of Frobisher Bay. The tidal flats have been divided into six morphological zones which are closely related to the three biological communities found there. </p> <p> Faunal species of the Upper Flat inhabit the beach and fines flat morphological zones where ice action during breakup and freezeup has the greatest influence. Species inhabiting these zones are hardy, and freshwater tolerant. Many are highly motile and recolonize the area after ice breakup. </p> <p> The Middle Flat extends from 5.0 m ALLT to 2.2 m ALLT. It is inhabited by motile polychaetes at its upper end (bouldery flat >4.5 m ALLT). with more sedentary species appearing towards its lower end (very bouldery flat). Below 2.2 m ALLT, on the Lower graded flat, sedentary infauna such as Cyrtodaria kurriana, Mya truncata and sabellid polychaetes, dominate the substrate. </p> <p> The three major processes acting on the tidal flats are, in order of importance, tidal, ice and wave action. Exposure indices, generated from tidal data, reveal 2 critical tidal heights at around 4 m and 7.5 m ALLT, in Frobisher Bay. The boundary between motile and less motile fauna, and bouldery and very bouldery morphological zones, occurs around 4.0 m ALLT. Of the flora and fauna only Fucus evanescens is found beyond the 7.5 m ALLT limit. </p> / Thesis / Master of Science (MSc)

Made available in DSpace on 2016-07-27T14:19:52Z (GMT). No. of bitstreams: 1 MONICA MARIA BARROS DE SOUZA.pdf: 293950 bytes, checksum: a75939d1b83b5fdf65f00dbc6427c536 (MD5) Previous issue date: 2005-06-20 / It is increasing nowadays the number of marital relationship failures in all social levels. The majority of these failures are followed in most cases by breakup. Is is been noticed among married women a change of their value criteria of their male partner. Considering this perspective, the purpose of this research is to reveal the underlying meanings of this female evaluation experienced in the physicalbiological, socio-cultural and psychological areas. The method chose for this research was the qualitative phenomenological approach, which suplies a deeper exploration of the experienced meanings. The results analysis shows a change related to the bibliography provided. It is observed that the married woman finds less worthy her male partner economical power due to her own economical emancipation. On the other hand, they give an accredited relative value of the physical and correlated aspects and they turn to be more demanding concerning the psycho-affective ones. / No mundo atual, em todas as camadas sociais, aumenta o número de fracasso nos relacionamentos conjugais, seguida na maioria das vezes da dissolução dos mesmos. Por outro lado, observa-se por parte da mulher casada, uma mudança nos critérios valorativos do seu parceiro. Nesta perspectiva, o presente trabalho tem como objetivo desvelar os significados subjacentes a essa avaliação feminina, vivenciados nessas três áreas: física, sócio-econômica e psicológica. O método escolhido para tal pesquisa é o qualitativo de base fenomenológica, pois, facilita uma exploração mais aprofundada dos significados experienciados. A análise de resultados aponta uma mudança em relação a bibliografia comentada. A esse respeito, observa-se que a mulher casada graças a sua emancipação econômica, dá menos importância ao poder econômico do parceiro. Por outro lado, confere um valor relativo aos aspectos físicos e correlatos e se torna mais exigente no que diz respeito aos aspectos psico-afetivos.

Scopo del progetto era valutare lo stato di salute e la qualità dei suoli agricoli lombardi e di alcune sue aree caratterizzate da specifiche criticità ambientali, attraverso un monitoraggio multidisciplinare. L’uso di indicatori biologici accoppiato alle classiche tecniche analitiche ha consentito di implementare le informazioni ottenute dal punto di vista chimico-fisico. Contrariamente al passato infatti, la componente vivente del suolo è diventata fondamentale alla comprensione delle sue condizioni, in quanto esso è stato riconosciuto come sistema strettamente connesso agli altri comparti ambientali, influenzato e caratterizzato da tutti gli organismi che lo compongono. Sulla base di ciò sono state indagate la struttura e le caratteristiche delle comunità microbiche, dei lombrichi e dei protozoi ciliati, le attività enzimatiche del suolo, e la genotossicità delle sostanze inquinanti utilizzando il trifoglio come pianta indicatrice. Abbiamo inoltre avuto modo di applicare alcune tecniche che esulano dal classico monitoraggio, ma che forniscono informazioni preziose circa il comportamento di una sostanza o di un elemento. Si tratta dell’applicazione della diluizione isotopica per determinare la presenza del cromo esavalente in suoli potenzialmente contaminati, e di biosaggi con batteri bioluminescenti per valutare la biodisponibilità di arsenico e mercurio in un Sito di Interesse Nazionale. / The aim of the project was to assess health status and quality of agricultural soils of the Lombardia region, and some areas with critical environmental situations, through a multidisciplinary monitoring. The use of biological indicators coupled to classic analytical techniques, has allowed the implementation of the information obtained from the chemical-physical point of view. Contrary to the past, the living component of the soil has become crucial to better understand its condition, as it has been recognized as a system closely related to other environmental media, influenced and characterized by all organisms that compose it. Basing on this it was investigated the structure and characteristics of microbial communities, earthworms and ciliated protozoa, the enzymatic activities of the soil, and the genotoxicity of pollutants using clover plants as indicator. We also had the opportunity to apply some of the techniques that are outside the classic monitoring, but that can provide valuable information about the behavior of a substance or an element. These techniques are: the application of isotope dilution to determine the presence of hexavalent chromium in potentially contaminated soils, and bioassays with bioluminescent bacteria to assess the bioavailability of arsenic and mercury in a Site of National Interest.