Wong Chun Kwan. / "June, 2003." / Thesis (Ph.D.)--Chinese University of Hong Kong, 2003. / Includes bibliographical references (p. 211-231). / Electronic reproduction. Hong Kong : Chinese University of Hong Kong, [2012] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Electronic reproduction. Ann Arbor, MI : ProQuest Information and Learning Company, [200-] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Mode of access: World Wide Web. / Abstracts in English and Chinese.

[Truncated abstract] This work was the first large-scale biological oceanographic study to be undertaken in the coastal eastern Indian Ocean adjacent to Western Australia, and covered both northwest (Exmouth Peninsula to the Abrolhos Islands) and southwest (Cape Naturaliste to Cape Leeuwin) regions. The study area was dominated by the Leeuwin Current (LC), an anomalous eastern boundary current that transports tropical water poleward and prevents deep nutrients from reaching the surface by creating large-scale downwelling. Indeed, LC and offshore waters were consistently associated with low nitrate concentrations and low phytoplankton biomass and production (< 200 mg C m-2 d-1). However, the physical forcing of the LC was offset, during the summer months, by upwelling associated with wind-driven inshore countercurrents (Ningaloo and Capes Currents), which provided a mechanism to access high nutrient concentrations normally confined to the base of the LC. ... Limited seasonal investigations off the Capes region of southwestern Australia showed that the winter production scenario can be very different than summer conditions, with strong Leeuwin Current flow that meanders onto the continental shelf and entrains seasonally nutrient-enriched shelf waters. However, production in the LC was still low (≤450 mg C m-2 d-1) due to light limitation resulting from both increased light attenuation and reduced surface irradiance characteristic of the winter months. This investigation provides fundamental knowledge on physical-biological coupling off Western Australia, with implications for fisheries management in view of seasonal and inter-annual variability in the strength of both the Leeuwin Current and inshore countercurrents.

The influence of mesoscale ocean eddies on near-surface ocean temperature, surface stress and phytoplankton communities is investigated by collocating numerous satellite measurements along with vertical profiles of oceanic temperature and salinity to the interiors of eddies identified and tracked in altimetric sea surface height maps. The surface currents associated with mesoscale ocean eddies impart a curl of the surface stress from the relative motion between surface air and water. This stress curl has a polarity opposite that of the vorticity of the eddy, thus attenuating the eddies by generating Ekman upwelling in the cores of anticyclones and downwelling in the cores of cyclones. Ekman pumping also arises from eddy-induced spatial variability of the sea surface temperature (SST) field that generates a wind stress curl in regions of crosswind SST gradients through a response of surface winds to SST-induced surface heating variations. SST-induced Ekman pumping is shown to be secondary to surface current-induced pumping in most regions of the World Ocean. Eddy-induced Ekman pumping resulting from the combination of surface current effects and air-sea interaction represents an order 1 perturbation of the background, basin-scale Ekman pumping velocities from the large-scale wind fields. In western boundary currents and equatorward-flowing eastern boundary currents, cyclonic eddies preferentially entrain water from the coastal side of the boundary current, which primes the interiors of cyclones to have phytoplankton concentrations that are elevated relative to the background. In contrast, anticyclones formed in these regions contain locally depressed phytoplankton concentrations from the offshore waters. While eddy pumping from vertical displacements of isopycnals during eddy formation can affect the biology in the interiors of cyclones during the transient stage of their development, this ecosystem response cannot be sustained because of the persistent eddy-induced Ekman downwelling throughout the rest of the eddy lifetimes. Likewise, the persistent eddy-induced Ekman upwelling in anticyclones is of little benefit because of their low phytoplankton content at the time of formation. A definitive response to eddy pumping is therefore difficult to detect from satellite observations alone. Eddies formed in regions where anticyclones preferentially entrain water with elevated phytoplankton concentrations, such as the South Indian Ocean, or in some mid-ocean gyre regions where small-amplitude eddies form (e.g., the oligotrophic South Pacific), an ecosystem response to eddy-induced Ekman pumping is observed. Conversely, cyclones in these regions entrain water that is low in chlorophyll, resulting in negative chlorophyll anomalies that are sustained by Ekman downwelling throughout the eddy lifetimes. The phytoplankton response to eddy-induced Ekman upwelling in anticyclones is seasonal, occurring only during the winter. It is proposed that the mechanism for the lack of ecosystem response to eddy-induced Ekman upwelling during the summer is the decoupling of the mixed layer from the nutricline. The observations presented in this dissertation provide a baseline from which coupled ocean circulation and biogeochemical models can be assessed. If coupled models are able to reproduce correctly the observed influence of mesoscale eddies on photoautotrophic communities, further insight into the mechanisms for this variability could be gained from the model output using the methodologies developed in this dissertation together with investigation of subsurface variability in the models below the depth to which chlorophyll can be inferred from the satellite observations. / Graduation date: 2013

Thesis (Ph. D.)--University of Washington, 2003. / Vita. Includes bibliographical references (leaves 125-140).

Storm-induced open-ocean convective mixing is one of the primary processes controlling the supply of nitrate to the sunlit layer of the oligotrophic North Atlantic Subtropical Gyre (NASG). Yet, the magnitude and timing of nitrate fluxes during winter convection is poorly understood due to an absence of targeted process studies. In the northwest NASG, multiple quasi-Lagrangian studies were conducted during the boreal winters of 2004 and 2005 in an effort to sample strong winter convection. During each of the time-series studies, inventories of vertically fluxed nitrate were quantified approximately every twelve hours using the distribution of helium isotopes ([delta]�He) and nitrate in the water column. This method is known as the Helium Flux Gauge Technique (HFGT). Large variability in surface forcing and density structure of the upper ocean was observed between the two years; however, only winter 2005 experienced convective mixing to depths greater than 150 m. In winter 2004, mild atmospheric conditions coincided with a positive phase in the winter North Atlantic Oscillation (NAO), consistent with the dominant regime experienced during the previous decade. On average 36 � 9 mmol m[-2] of fluxed nitrate was inferred by excess �He in the mixed layer of the ocean during the winter 2004 study period. This inventory of physically transported nitrate is attributed to the sampling of waters laterally advected from nearby eddy features. The sampling of multiple water masses is likely due to the inability of the drogue to persistently follow water masses efficiently. Although physical evidence indicates spatial variability within the time-series data, the length scales of convective mixing appear to be greater than those associated with spatial aliasing as a result of drogue performance. This observation provides us with increased confidence that the objectives for the present study are not compromised by spatial variability in the data. In contrast, winter 2005 experienced a negative NAO, strong physical forcing and convective mixing to depths > 250 m. Two convectively modified water masses, most likely resulting from a single storm event, were sampled at different stages of development. These two water masses exhibit large variability in the magnitude of nitrate entrained in the convective layer from the thermocline. An average inventory of 247 � 56 mmol NO₃[-]m[-2] was entrained in the rapidly expanding convective layer of the first water mass in the first few days following the storm approach. In contrast, ongoing entrainment of nitrate was absent from the second water mass, sampled two weeks later when the depth of the surface mixed layer was consistently ~ 300 m. These results indicate that surrounding fluid is entrained into the convective layer when it is actively expanding in the vertical. On the other hand, significant fluid entrainment does not occur at the base of the plume once sinking waters have reached a level of neutral buoyancy. The persistence of elevated nitrate stocks (~ 100 mmol m[-2]) in the convective layer two to three weeks after the inferred injection event, suggests sub-optimal nitrate uptake by resident phytoplankton. Phytoplankton growth was most likely resource limited by light or a micronutrient such as iron. Despite the implied biolimitation, changes in chlorophyll-a, a proxy for phytoplankton biomass, indicate net production within the convective layer. On average, the convective layer was observed to support an inventory of 62 � 6mg chlorophyll-a m[-2], increasing at an average rate of 3.4mg m[-2] d[-1]. This inventory indicates a slow build-up of phytoplankton biomass to near bloom levels, ahead of the main spring bloom that typically follows formation of the seasonal thermocline near Bermuda. Net production in the convective layer was likely due to transient periods of increased (weak) surface stability that were observed to support high phytoplankton biomass, following the cessation of thermocline fluid entrainment. When nitrate and excess �He in samples collected from the thermocline were regressed for the purpose of quantifying nitrate fluxes, the results showed that between 1.6 - 2.0 [mu]mol kg[-1] of dissolved nitrate was present during formation of the water mass. This suggests the source of this excess (above Redfield ratios) nitrate in the thermocline of the NASG is not local, and has ramifications for local nitrogen fixation budgets determined using geochemical approaches. Thesis supervisors: William J. Jenkins, Senior Scientist, WHOI (United States of America); Philip W. Boyd, Senior Scientist, NIWA (New Zealand); Michael W. Lomas, Senior Scientist, BIOS (Bermuda)

Storm-induced open-ocean convective mixing is one of the primary processes controlling the supply of nitrate to the sunlit layer of the oligotrophic North Atlantic Subtropical Gyre (NASG). Yet, the magnitude and timing of nitrate fluxes during winter convection is poorly understood due to an absence of targeted process studies. In the northwest NASG, multiple quasi-Lagrangian studies were conducted during the boreal winters of 2004 and 2005 in an effort to sample strong winter convection. During each of the time-series studies, inventories of vertically fluxed nitrate were quantified approximately every twelve hours using the distribution of helium isotopes ([delta]�He) and nitrate in the water column. This method is known as the Helium Flux Gauge Technique (HFGT). Large variability in surface forcing and density structure of the upper ocean was observed between the two years; however, only winter 2005 experienced convective mixing to depths greater than 150 m. In winter 2004, mild atmospheric conditions coincided with a positive phase in the winter North Atlantic Oscillation (NAO), consistent with the dominant regime experienced during the previous decade. On average 36 � 9 mmol m[-2] of fluxed nitrate was inferred by excess �He in the mixed layer of the ocean during the winter 2004 study period. This inventory of physically transported nitrate is attributed to the sampling of waters laterally advected from nearby eddy features. The sampling of multiple water masses is likely due to the inability of the drogue to persistently follow water masses efficiently. Although physical evidence indicates spatial variability within the time-series data, the length scales of convective mixing appear to be greater than those associated with spatial aliasing as a result of drogue performance. This observation provides us with increased confidence that the objectives for the present study are not compromised by spatial variability in the data. In contrast, winter 2005 experienced a negative NAO, strong physical forcing and convective mixing to depths > 250 m. Two convectively modified water masses, most likely resulting from a single storm event, were sampled at different stages of development. These two water masses exhibit large variability in the magnitude of nitrate entrained in the convective layer from the thermocline. An average inventory of 247 � 56 mmol NO₃[-]m[-2] was entrained in the rapidly expanding convective layer of the first water mass in the first few days following the storm approach. In contrast, ongoing entrainment of nitrate was absent from the second water mass, sampled two weeks later when the depth of the surface mixed layer was consistently ~ 300 m. These results indicate that surrounding fluid is entrained into the convective layer when it is actively expanding in the vertical. On the other hand, significant fluid entrainment does not occur at the base of the plume once sinking waters have reached a level of neutral buoyancy. The persistence of elevated nitrate stocks (~ 100 mmol m[-2]) in the convective layer two to three weeks after the inferred injection event, suggests sub-optimal nitrate uptake by resident phytoplankton. Phytoplankton growth was most likely resource limited by light or a micronutrient such as iron. Despite the implied biolimitation, changes in chlorophyll-a, a proxy for phytoplankton biomass, indicate net production within the convective layer. On average, the convective layer was observed to support an inventory of 62 � 6mg chlorophyll-a m[-2], increasing at an average rate of 3.4mg m[-2] d[-1]. This inventory indicates a slow build-up of phytoplankton biomass to near bloom levels, ahead of the main spring bloom that typically follows formation of the seasonal thermocline near Bermuda. Net production in the convective layer was likely due to transient periods of increased (weak) surface stability that were observed to support high phytoplankton biomass, following the cessation of thermocline fluid entrainment. When nitrate and excess �He in samples collected from the thermocline were regressed for the purpose of quantifying nitrate fluxes, the results showed that between 1.6 - 2.0 [mu]mol kg[-1] of dissolved nitrate was present during formation of the water mass. This suggests the source of this excess (above Redfield ratios) nitrate in the thermocline of the NASG is not local, and has ramifications for local nitrogen fixation budgets determined using geochemical approaches. Thesis supervisors: William J. Jenkins, Senior Scientist, WHOI (United States of America); Philip W. Boyd, Senior Scientist, NIWA (New Zealand); Michael W. Lomas, Senior Scientist, BIOS (Bermuda)

Thesis (Ph.D.)--University of Western Australia, 2006.

Thesis (M.S.)--Naval Postgraduate School, 1981. / Cover title. "September 1981." Includes bibliographical references (leaves 108-120).

A Baía da Ilha Guaíba é um sistema costeiro tropical com influência de águas oceânicas, principalmente da Corrente do Brasil e das Águas Costeiras que são predominantes em toda a costa da região sudeste. O objetivo geral foi identificar os indicadores biológicos das possíveis alterações ambientais e ou antrópicas e como objetivos específicos, apresentar a distribuição qualitativa e quantitativa do fitoplâncton em função da espacialidade e da sazonalidade em duas situações de maré bem como demonstrar a estrutura da comunidade fitoplanctônica dentro de um Programa de Monitoramento desenvolvido pela empresa Minerações Brasileiras Reunidas através do Centro de Tecnologia Ambiental da FIRJAN (CTA). Foram estabelecidos 9 pontos amostrais na área sob influência do Terminal Marítimo da Ilha levando em consideração as características de cada um. Para o estudo qualitativo e quantitativo do fitoplâncton, 200 ml de água foram coletados em dois pontos de amostragem 7 e 9 em baixa-mar e preamar, através de garrafa de Van Dorn e nos 9 pontos foi realizado arrasto com rede de 50&#956;m, ambos em quatro épocas sazonais distintas. Ao todo foram encontradas 176 unidades taxonômicas demonstrando uma importante oferta de nichos. A espécie que mais se destacou foi Coscinodiscus cf. centralis em todas as amostras de rede. A sazonalidade foi vista através de uma análise de Cluster tanto para as amostras de rede quanto para as de garrafa. Não houve registro de espécies que indicassem alterações antrópicas não revelando condição de eutrofização. Foram encontradas espécies indicadoras de diferentes massas de água como também outras potencialmente nocivas. Os resultados bióticos e abióticos demonstraram que a área sob influência do empreendimento está dentro dos padrões estabelecidos pela legislação vigente e que para o estabelecimento de um desenvolvimento sustentável torna-se imprescindível a adoção de métodos padronizados e multiinterdisciplinares para que seja possível comparar e acompanhar os processos e seus efeitos viabilizando assim a manutenção da biodiversidade. / The surrounding region of Guaíba Island is a tropical coastal system which receives oceanic waters. Such waters come mainly from the Brazil Current and from coastal waters which are predominantly found throughout the coast of the south-east region of Brazil. The present academic work pointed the possibility of finding species indicating natural or antropic or antropogenic impacts in the region. The general objective of this work was to identify biological indicators of possible antropic and or environmental alterations. The specific objectives of this work is to present the qualitative and quantitative phytoplanktonic relation between spatial and seasonal variation in two tidal situations as well as to demonstrate the phytoplanktonic structure of a monitoring program conducted by the called: Centro de Tecnologia Ambiental da FIRJAN (CTA) (FIRJAN Environmental Technology Center) on behalf of Minerações Brasileiras Reunidas (United Brazilian Mining). Moreover, nine sample-collection spots, which were established as being under influence of the local island maritime terminal, they had their characteristics individually taken into consideration. In order to study the phytoplankton samples qualitatively and quantitatively, 200 ml of sea water was collected from collection spots 7 and 9 at low and high tides by using a Van Dorn bottle. Furthermore, 50&#956;m net castings and pullings were conducted at the nine collection spots in four particular seasonal periods. As a result, 176 taxonomic units demonstrating enormous niches offer were found. In addition, the most outstanding species found among all net samples was: Coscinodiscus cf. centralis. The seasonality was observed by using a cluster analysis both in the net samples and in the bottle samples. No species records indicated antropic alterations and did not reveal any eutrophication conditions. Moreover, different water-mass indicator species were found as well as other potentially harmful ones. The biotic and abiotic results demonstrated that the area under influence of the local water transportation terminal was legally correct according to current and valid environmental laws. Furthermore, in order to achieve the establishment of sustainable development, it is of the utmost importance that standardized and multi-interdisciplinary methods are adopted to enable researchers to compare and follow processes and effects of biodiversity maintenance.

A Baía da Ilha Guaíba é um sistema costeiro tropical com influência de águas oceânicas, principalmente da Corrente do Brasil e das Águas Costeiras que são predominantes em toda a costa da região sudeste. O objetivo geral foi identificar os indicadores biológicos das possíveis alterações ambientais e ou antrópicas e como objetivos específicos, apresentar a distribuição qualitativa e quantitativa do fitoplâncton em função da espacialidade e da sazonalidade em duas situações de maré bem como demonstrar a estrutura da comunidade fitoplanctônica dentro de um Programa de Monitoramento desenvolvido pela empresa Minerações Brasileiras Reunidas através do Centro de Tecnologia Ambiental da FIRJAN (CTA). Foram estabelecidos 9 pontos amostrais na área sob influência do Terminal Marítimo da Ilha levando em consideração as características de cada um. Para o estudo qualitativo e quantitativo do fitoplâncton, 200 ml de água foram coletados em dois pontos de amostragem 7 e 9 em baixa-mar e preamar, através de garrafa de Van Dorn e nos 9 pontos foi realizado arrasto com rede de 50&#956;m, ambos em quatro épocas sazonais distintas. Ao todo foram encontradas 176 unidades taxonômicas demonstrando uma importante oferta de nichos. A espécie que mais se destacou foi Coscinodiscus cf. centralis em todas as amostras de rede. A sazonalidade foi vista através de uma análise de Cluster tanto para as amostras de rede quanto para as de garrafa. Não houve registro de espécies que indicassem alterações antrópicas não revelando condição de eutrofização. Foram encontradas espécies indicadoras de diferentes massas de água como também outras potencialmente nocivas. Os resultados bióticos e abióticos demonstraram que a área sob influência do empreendimento está dentro dos padrões estabelecidos pela legislação vigente e que para o estabelecimento de um desenvolvimento sustentável torna-se imprescindível a adoção de métodos padronizados e multiinterdisciplinares para que seja possível comparar e acompanhar os processos e seus efeitos viabilizando assim a manutenção da biodiversidade. / The surrounding region of Guaíba Island is a tropical coastal system which receives oceanic waters. Such waters come mainly from the Brazil Current and from coastal waters which are predominantly found throughout the coast of the south-east region of Brazil. The present academic work pointed the possibility of finding species indicating natural or antropic or antropogenic impacts in the region. The general objective of this work was to identify biological indicators of possible antropic and or environmental alterations. The specific objectives of this work is to present the qualitative and quantitative phytoplanktonic relation between spatial and seasonal variation in two tidal situations as well as to demonstrate the phytoplanktonic structure of a monitoring program conducted by the called: Centro de Tecnologia Ambiental da FIRJAN (CTA) (FIRJAN Environmental Technology Center) on behalf of Minerações Brasileiras Reunidas (United Brazilian Mining). Moreover, nine sample-collection spots, which were established as being under influence of the local island maritime terminal, they had their characteristics individually taken into consideration. In order to study the phytoplankton samples qualitatively and quantitatively, 200 ml of sea water was collected from collection spots 7 and 9 at low and high tides by using a Van Dorn bottle. Furthermore, 50&#956;m net castings and pullings were conducted at the nine collection spots in four particular seasonal periods. As a result, 176 taxonomic units demonstrating enormous niches offer were found. In addition, the most outstanding species found among all net samples was: Coscinodiscus cf. centralis. The seasonality was observed by using a cluster analysis both in the net samples and in the bottle samples. No species records indicated antropic alterations and did not reveal any eutrophication conditions. Moreover, different water-mass indicator species were found as well as other potentially harmful ones. The biotic and abiotic results demonstrated that the area under influence of the local water transportation terminal was legally correct according to current and valid environmental laws. Furthermore, in order to achieve the establishment of sustainable development, it is of the utmost importance that standardized and multi-interdisciplinary methods are adopted to enable researchers to compare and follow processes and effects of biodiversity maintenance.