O presente trabalho tem como objetivo geral o estudo da composição e estrutura da macrofauna bêntica em escala espacial e sazonal, da região de Cabo Frio (RJ). O aspecto temporal nessa área é especialmente importante devido a ocorrência do fenômeno sazonal da ressurgência costeira. Esse ocorre devido alguns fatores físicos característicos da área, tais como mudanças na topografia e na direção da costa, e principalmente, em decorrência das condições meteorológicas atuantes no local. A interação desses fatores favorece, principalmente no verão, o ressurgimento próximo à costa da Água Central do Atlântico Sul (ACAS), uma massa de água fria e rica em nutrientes. Essa massa de água disponibiliza grande quantidade de nutrientes para o fitoplâncton das camadas superficiais, ocasionando uma elevada produção primária nova. Parte dessa produção é exportada para o fundo incrementando a biomassa bêntica. Assim, a comunidade bêntica assume um papel vital no ecossistema, sendo tanto receptora como fornecedora de energia. Os descritores de comunidade (densidade, biomassa, riqueza, diversidade e equitatividade) e a identificação dos grupos tróficos de Polychaeta foram analisados entre 40 e 1000m de profundidade e em três épocas do ano, inverno de 2001 e verão e primavera de 2002. A integração dos dados biológicos com os ambientais mostrou que as variações espaciais na estrutura e composição dos organismos foi relacionada à profundidade e ao tipo de sedimento verificado nas estações. A estrutura da comunidade também apresentou variações temporais, especialmente nas estações situadas na plataforma continental, respondendo à entrada de matéria orgânica decorrente do evento de ressurgência. / The main objective of the present study was to evaluate the composition and spatial and seasonal structure of the macrobenthic fauna off Cabo Frio (RJ). The temporal scale was investigated in the light of the seasonal coastal upwelling. This phenomenon occurs due to changes in bottom topography and in the coastline direction, and specially, because of the prevailing seasonal NE winds in the area. The interaction of these factors enables the South Atlantic Central Water (SACW) to rise up and reaches the surface, intensively during the summer months. Large amounts of nutrients are then brought to the euphotic zone, enhancing primary productivity. This high productivity increases food supply for benthic communities by sinking of particulate organic carbon. In this way, the benthic communities are an important link in the ecosystem. The density of organisms, biomass, species richness and evenness and also the trophic group of Polychaeta were analyzed in a depth gradient from 40 to 1000m during the 2001 winter and 2002 summer and spring. Faunal distributional patterns and species composition correlated with environmental variables, especially depth and sediment types. The faunal structure also showed temporal changes along the sample period, especially in the stations located in the continental shelf due to the input of organic matter to the sea floor.

O presente trabalho tem como objetivo geral o estudo da composição e estrutura da macrofauna bêntica em escala espacial e sazonal, da região de Cabo Frio (RJ). O aspecto temporal nessa área é especialmente importante devido a ocorrência do fenômeno sazonal da ressurgência costeira. Esse ocorre devido alguns fatores físicos característicos da área, tais como mudanças na topografia e na direção da costa, e principalmente, em decorrência das condições meteorológicas atuantes no local. A interação desses fatores favorece, principalmente no verão, o ressurgimento próximo à costa da Água Central do Atlântico Sul (ACAS), uma massa de água fria e rica em nutrientes. Essa massa de água disponibiliza grande quantidade de nutrientes para o fitoplâncton das camadas superficiais, ocasionando uma elevada produção primária nova. Parte dessa produção é exportada para o fundo incrementando a biomassa bêntica. Assim, a comunidade bêntica assume um papel vital no ecossistema, sendo tanto receptora como fornecedora de energia. Os descritores de comunidade (densidade, biomassa, riqueza, diversidade e equitatividade) e a identificação dos grupos tróficos de Polychaeta foram analisados entre 40 e 1000m de profundidade e em três épocas do ano, inverno de 2001 e verão e primavera de 2002. A integração dos dados biológicos com os ambientais mostrou que as variações espaciais na estrutura e composição dos organismos foi relacionada à profundidade e ao tipo de sedimento verificado nas estações. A estrutura da comunidade também apresentou variações temporais, especialmente nas estações situadas na plataforma continental, respondendo à entrada de matéria orgânica decorrente do evento de ressurgência. / The main objective of the present study was to evaluate the composition and spatial and seasonal structure of the macrobenthic fauna off Cabo Frio (RJ). The temporal scale was investigated in the light of the seasonal coastal upwelling. This phenomenon occurs due to changes in bottom topography and in the coastline direction, and specially, because of the prevailing seasonal NE winds in the area. The interaction of these factors enables the South Atlantic Central Water (SACW) to rise up and reaches the surface, intensively during the summer months. Large amounts of nutrients are then brought to the euphotic zone, enhancing primary productivity. This high productivity increases food supply for benthic communities by sinking of particulate organic carbon. In this way, the benthic communities are an important link in the ecosystem. The density of organisms, biomass, species richness and evenness and also the trophic group of Polychaeta were analyzed in a depth gradient from 40 to 1000m during the 2001 winter and 2002 summer and spring. Faunal distributional patterns and species composition correlated with environmental variables, especially depth and sediment types. The faunal structure also showed temporal changes along the sample period, especially in the stations located in the continental shelf due to the input of organic matter to the sea floor.

The Great Australian Bight (GAB) was for many years thought to be an area of limited biological productivity due to a perceived lack of nutrient enrichment processes. These conclusions, however, were based on data from few studies in the western GAB which were assumed to reflect conditions throughout the entire GAB. More recent studies have reported the occurrence of coastal upwelling in the eastern GAB (EGAB) during summer/autumn (November-April), characterized by low sea surface temperatures and elevated concentrations of chlorophyll α, which suggests that certain areas of the GAB may be highly productive during certain times of the year. The eastern Great Australian Bight (EGAB) forms part of the Southern and Indian Oceans and is an area of high ecological and economic importance. Although it supports the largest fishery in Australia (the South Australian Sardine fishery, annual catches since 2004 ~ 25,000 to 42,500 t), quantitative estimates of the primary productivity underlying this industry are open to debate. Estimates range from < 100 mg C m⁻² day⁻¹ to > 500 mg C m⁻² day⁻¹. Part of this variation may be due to the unique upwelling circulation of shelf waters in summer/autumn (November-April), which shares some similarities with highly productive eastern boundary current upwelling systems, but differs due to the influence of a northern boundary current, the Flinders current, and a wide continental shelf. Shelf waters encompass an area of ~115,000 km², and the diverse coastal topography forms part of one of the longest stretches of southward facing coastline in the world. In summer-autumn, winds are upwelling favourable, and the Flinders current running along the continental slope causes the upwelling of the deep permanent thermocline from around 600 m depth (dynamic uplift), allowing nutrient rich cold water to entrain onto the shelf. In winterspring, the EGAB is dominated by westerly downwelling-favourable winds, and upwelling via the Flinders current is suppressed. Thus, the area is highly dynamic, with significant spatial and temporal variations in meteorology and oceanography which may drive variations in nutrient enrichment and productivity. This study represents the first intensive investigation of the primary and secondary productivity of the EGAB, and was designed to evaluate the general hypothesis that spatial and temporal variations in meteorology and oceanography in the EGAB will drive spatial and temporal variations in phytoplankton size structure, and primary and secondary productivity. It examines variations in primary and secondary productivity in the EGAB during the upwelling and downwelling seasons of 2004, and the upwelling seasons of 2005 and 2006. Daily integral productivity calculated using the vertically generalised production model (VGPM) showed a high degree of spatial variation. Productivity was low (<800 mg C m⁻² day⁻¹) in offshore central and western regions of the EGAB. High productivities (1600-3900 mg C m⁻² day⁻¹) were restricted to hotspots in the east that were influenced by the upwelled water mass. There was a strong correlation between the depth of the euphotic zone and the depth of the mixed layer that suggested that ~50% of the euphotic zone lay below the mixed layer depth. As a result, high rates of primary productivity did not require upwelled water to reach the surface. A significant proportion of total productivity in the euphotic zone (57% in 2005 and 65% in 2006) occurred in the upwelled water mass below the surface mixed layer. This result has implications for daily integral productivities modelled with the VGPM, which uses surface measures of phytoplankton biomass to calculate productivity. Macro nutrient concentrations could not be used to explain the difference in the low and high productivities (silica >1 μmol L⁻¹, nitrate/nitrite >0.4 μmol L⁻¹, phosphate >0.1 μmol L⁻¹). Mixing patterns or micro-nutrient concentrations are possible explanations for spatial variations in primary productivity in the EGAB. On a global scale, daily rates of primary productivity of the EGAB lie between the highly productive eastern boundary current upwelling systems, and less productive coastal regions of western and south eastern Australia, and the oligotrophic ocean. However, daily productivity rates in the upwelling hotspots of the EGAB rival productivities in Benguela and Humbolt currents. Temporal variation in mixing and primary productivity was examined in upwelling influenced nearshore waters off south western Eyre Peninsula (SWEP) in the EGAB. Mixing/stratification in the region was highly temporally variable due to the unique upwelling circulation in summer/autumn, and downwelling through winter/spring. Highest productivity was associated with pwelled/stratified water (up to 2958 mg C m⁻² d⁻¹), with low productivity during periods of downwelling and mixing (~300-550 mg C m⁻² d⁻¹), yet no major variations in macro-nutrient concentrations were detected between upwelling and downwelling events (silica >1 μmol L⁻¹, nitrate/nitrite >0.4 μmol L⁻¹, phosphate >0.1 μmol L⁻¹). We hypothesise that upwelling enriches the region with micro-nutrients. High productivity off SWEP appears to be driven by a shallowing of mixed layer depth due to the injection of upwelled waters above Z[subscript]cr. Low productivity follows the suppression of enrichment during downwelling/mixing events, and is exacerbated in winter/spring by low irradiances and short daylengths. Phytoplankton abundance and community composition was also examined in the shelf waters of the EGAB. Phytoplankton abundances were generally higher in near shore waters compared with offshore waters, and during the summer/autumn upwelling season compared with the winter/spring downwelling season. Three distinctly different phytoplankton communities were present in the region during the upwelling and downwelling seasons of 2004, and the upwelling season of 2005, with distinctions manifest in variations in the abundance of dominant types of phytoplankton, and differences in average cell sizes. In summer/autumn, waters influenced by upwelling were characterised by high phytoplankton abundances (particularly diatoms) and larger average cell sizes, while the warmer high-nutrientlow- chlorophyll (HNLC) waters in the region had lower phytoplankton abundances and smaller average cell sizes. The winter/spring community was made up of low abundances of relatively large cells. Diatoms always dominated, but evidence of Si limitation of further diatom growth suggests there may be an upper limit to diatom productivity in the region. The maximum observed diatom concentration of ~164,000 cells L⁻¹ occurred in February/March 2004, in an area influenced by the upwelled water mass. Variations in phytoplankton biodiversity in the shelf waters of southern Australia appear to be related to variations in the influence of upwelling in the region. Meso-zooplankton abundance and community composition was examined in the coastal upwelling system of the EGAB. Spatial and temporal variations were influenced by variations in primary productivity and phytoplankton abundance and community composition, which were driven by variations in the influence of upwelling in the region. Peak meso-zooplankton abundances and biomass occurred in the highly productive upwelling influenced nearshore waters of the EGAB. However, abundances were highly variable between regions and years, reflecting the high spatial and temporal variations in primary productivity and phytoplankton abundance that characterise the shelf waters of the region. Spatial and temporal variations in community composition were driven by changes in the abundance of classes of meso zooplankton common to all regions in both years of this study. Meroplanktonic larvae and opportunistic colonizers dominated the community through the upwelling season, in response to increased primary productivity and phytoplankton blooms. Differences in community composition between upwelling influenced waters and the more HNLC regions appear to be reflected in the relative abundances of cladocera and appendicularia, with cladocera more abundant in productive upwelling influenced areas, and appendicularia thriving in the more HNLC regions of the EGAB. Highest potential grazing rates in the EGAB occurred in nearshore regions with highest mesozooplankton biomass, most likely in response to the high phytoplankton biomass that occurs in the same regions. Peak meso-zooplankton grazing rates in the EGAB were ~80% less than those measured in south west Spencer Gulf in March 2007, and ~35% greater than grazing rates in the Huon Estuary in February 2005. Productivity in the EGAB shows significant spatial and temporal variation, with changes reflecting regional and seasonal variation in meteorology and oceanography, and the water masses present in the region. The overall productivity of a summer/autumn upwelling season was highly dependent on within-season variations in wind strength and direction, which dictate the number, intensity, and duration of upwelling events. Rates of primary productivity measured in the EGAB at a given time depended on the meteorological and oceanographic conditions in the region in the lead up to, and during, the sampling event. We hypothesise that during upwelling events, high productivity in the EGAB is driven by the enrichment of waters above Z[subscript]cr, but below the surface mixed layer, with micro-nutrients. Low productivity within summer/autumn upwelling seasons follows the suppression of this enrichment during downwelling/mixing events, and the overall productivity of the upwelling season will depend on the number, duration and intensity of these downwelling/mixing events. Low productivity during winter/spring is driven by the absence of upwelling, low irradiances and short daylengths. / Thesis (Ph.D.) - University of Adelaide, School of Earth and Environmental Sciences, 2009

The Great Australian Bight (GAB) was for many years thought to be an area of limited biological productivity due to a perceived lack of nutrient enrichment processes. These conclusions, however, were based on data from few studies in the western GAB which were assumed to reflect conditions throughout the entire GAB. More recent studies have reported the occurrence of coastal upwelling in the eastern GAB (EGAB) during summer/autumn (November-April), characterized by low sea surface temperatures and elevated concentrations of chlorophyll α, which suggests that certain areas of the GAB may be highly productive during certain times of the year. The eastern Great Australian Bight (EGAB) forms part of the Southern and Indian Oceans and is an area of high ecological and economic importance. Although it supports the largest fishery in Australia (the South Australian Sardine fishery, annual catches since 2004 ~ 25,000 to 42,500 t), quantitative estimates of the primary productivity underlying this industry are open to debate. Estimates range from < 100 mg C m⁻² day⁻¹ to > 500 mg C m⁻² day⁻¹. Part of this variation may be due to the unique upwelling circulation of shelf waters in summer/autumn (November-April), which shares some similarities with highly productive eastern boundary current upwelling systems, but differs due to the influence of a northern boundary current, the Flinders current, and a wide continental shelf. Shelf waters encompass an area of ~115,000 km², and the diverse coastal topography forms part of one of the longest stretches of southward facing coastline in the world. In summer-autumn, winds are upwelling favourable, and the Flinders current running along the continental slope causes the upwelling of the deep permanent thermocline from around 600 m depth (dynamic uplift), allowing nutrient rich cold water to entrain onto the shelf. In winterspring, the EGAB is dominated by westerly downwelling-favourable winds, and upwelling via the Flinders current is suppressed. Thus, the area is highly dynamic, with significant spatial and temporal variations in meteorology and oceanography which may drive variations in nutrient enrichment and productivity. This study represents the first intensive investigation of the primary and secondary productivity of the EGAB, and was designed to evaluate the general hypothesis that spatial and temporal variations in meteorology and oceanography in the EGAB will drive spatial and temporal variations in phytoplankton size structure, and primary and secondary productivity. It examines variations in primary and secondary productivity in the EGAB during the upwelling and downwelling seasons of 2004, and the upwelling seasons of 2005 and 2006. Daily integral productivity calculated using the vertically generalised production model (VGPM) showed a high degree of spatial variation. Productivity was low (<800 mg C m⁻² day⁻¹) in offshore central and western regions of the EGAB. High productivities (1600-3900 mg C m⁻² day⁻¹) were restricted to hotspots in the east that were influenced by the upwelled water mass. There was a strong correlation between the depth of the euphotic zone and the depth of the mixed layer that suggested that ~50% of the euphotic zone lay below the mixed layer depth. As a result, high rates of primary productivity did not require upwelled water to reach the surface. A significant proportion of total productivity in the euphotic zone (57% in 2005 and 65% in 2006) occurred in the upwelled water mass below the surface mixed layer. This result has implications for daily integral productivities modelled with the VGPM, which uses surface measures of phytoplankton biomass to calculate productivity. Macro nutrient concentrations could not be used to explain the difference in the low and high productivities (silica >1 μmol L⁻¹, nitrate/nitrite >0.4 μmol L⁻¹, phosphate >0.1 μmol L⁻¹). Mixing patterns or micro-nutrient concentrations are possible explanations for spatial variations in primary productivity in the EGAB. On a global scale, daily rates of primary productivity of the EGAB lie between the highly productive eastern boundary current upwelling systems, and less productive coastal regions of western and south eastern Australia, and the oligotrophic ocean. However, daily productivity rates in the upwelling hotspots of the EGAB rival productivities in Benguela and Humbolt currents. Temporal variation in mixing and primary productivity was examined in upwelling influenced nearshore waters off south western Eyre Peninsula (SWEP) in the EGAB. Mixing/stratification in the region was highly temporally variable due to the unique upwelling circulation in summer/autumn, and downwelling through winter/spring. Highest productivity was associated with pwelled/stratified water (up to 2958 mg C m⁻² d⁻¹), with low productivity during periods of downwelling and mixing (~300-550 mg C m⁻² d⁻¹), yet no major variations in macro-nutrient concentrations were detected between upwelling and downwelling events (silica >1 μmol L⁻¹, nitrate/nitrite >0.4 μmol L⁻¹, phosphate >0.1 μmol L⁻¹). We hypothesise that upwelling enriches the region with micro-nutrients. High productivity off SWEP appears to be driven by a shallowing of mixed layer depth due to the injection of upwelled waters above Z[subscript]cr. Low productivity follows the suppression of enrichment during downwelling/mixing events, and is exacerbated in winter/spring by low irradiances and short daylengths. Phytoplankton abundance and community composition was also examined in the shelf waters of the EGAB. Phytoplankton abundances were generally higher in near shore waters compared with offshore waters, and during the summer/autumn upwelling season compared with the winter/spring downwelling season. Three distinctly different phytoplankton communities were present in the region during the upwelling and downwelling seasons of 2004, and the upwelling season of 2005, with distinctions manifest in variations in the abundance of dominant types of phytoplankton, and differences in average cell sizes. In summer/autumn, waters influenced by upwelling were characterised by high phytoplankton abundances (particularly diatoms) and larger average cell sizes, while the warmer high-nutrientlow- chlorophyll (HNLC) waters in the region had lower phytoplankton abundances and smaller average cell sizes. The winter/spring community was made up of low abundances of relatively large cells. Diatoms always dominated, but evidence of Si limitation of further diatom growth suggests there may be an upper limit to diatom productivity in the region. The maximum observed diatom concentration of ~164,000 cells L⁻¹ occurred in February/March 2004, in an area influenced by the upwelled water mass. Variations in phytoplankton biodiversity in the shelf waters of southern Australia appear to be related to variations in the influence of upwelling in the region. Meso-zooplankton abundance and community composition was examined in the coastal upwelling system of the EGAB. Spatial and temporal variations were influenced by variations in primary productivity and phytoplankton abundance and community composition, which were driven by variations in the influence of upwelling in the region. Peak meso-zooplankton abundances and biomass occurred in the highly productive upwelling influenced nearshore waters of the EGAB. However, abundances were highly variable between regions and years, reflecting the high spatial and temporal variations in primary productivity and phytoplankton abundance that characterise the shelf waters of the region. Spatial and temporal variations in community composition were driven by changes in the abundance of classes of meso zooplankton common to all regions in both years of this study. Meroplanktonic larvae and opportunistic colonizers dominated the community through the upwelling season, in response to increased primary productivity and phytoplankton blooms. Differences in community composition between upwelling influenced waters and the more HNLC regions appear to be reflected in the relative abundances of cladocera and appendicularia, with cladocera more abundant in productive upwelling influenced areas, and appendicularia thriving in the more HNLC regions of the EGAB. Highest potential grazing rates in the EGAB occurred in nearshore regions with highest mesozooplankton biomass, most likely in response to the high phytoplankton biomass that occurs in the same regions. Peak meso-zooplankton grazing rates in the EGAB were ~80% less than those measured in south west Spencer Gulf in March 2007, and ~35% greater than grazing rates in the Huon Estuary in February 2005. Productivity in the EGAB shows significant spatial and temporal variation, with changes reflecting regional and seasonal variation in meteorology and oceanography, and the water masses present in the region. The overall productivity of a summer/autumn upwelling season was highly dependent on within-season variations in wind strength and direction, which dictate the number, intensity, and duration of upwelling events. Rates of primary productivity measured in the EGAB at a given time depended on the meteorological and oceanographic conditions in the region in the lead up to, and during, the sampling event. We hypothesise that during upwelling events, high productivity in the EGAB is driven by the enrichment of waters above Z[subscript]cr, but below the surface mixed layer, with micro-nutrients. Low productivity within summer/autumn upwelling seasons follows the suppression of this enrichment during downwelling/mixing events, and the overall productivity of the upwelling season will depend on the number, duration and intensity of these downwelling/mixing events. Low productivity during winter/spring is driven by the absence of upwelling, low irradiances and short daylengths. / Thesis (Ph.D.) - University of Adelaide, School of Earth and Environmental Sciences, 2009

The Great Australian Bight (GAB) was for many years thought to be an area of limited biological productivity due to a perceived lack of nutrient enrichment processes. These conclusions, however, were based on data from few studies in the western GAB which were assumed to reflect conditions throughout the entire GAB. More recent studies have reported the occurrence of coastal upwelling in the eastern GAB (EGAB) during summer/autumn (November-April), characterized by low sea surface temperatures and elevated concentrations of chlorophyll α, which suggests that certain areas of the GAB may be highly productive during certain times of the year. The eastern Great Australian Bight (EGAB) forms part of the Southern and Indian Oceans and is an area of high ecological and economic importance. Although it supports the largest fishery in Australia (the South Australian Sardine fishery, annual catches since 2004 ~ 25,000 to 42,500 t), quantitative estimates of the primary productivity underlying this industry are open to debate. Estimates range from < 100 mg C m⁻² day⁻¹ to > 500 mg C m⁻² day⁻¹. Part of this variation may be due to the unique upwelling circulation of shelf waters in summer/autumn (November-April), which shares some similarities with highly productive eastern boundary current upwelling systems, but differs due to the influence of a northern boundary current, the Flinders current, and a wide continental shelf. Shelf waters encompass an area of ~115,000 km², and the diverse coastal topography forms part of one of the longest stretches of southward facing coastline in the world. In summer-autumn, winds are upwelling favourable, and the Flinders current running along the continental slope causes the upwelling of the deep permanent thermocline from around 600 m depth (dynamic uplift), allowing nutrient rich cold water to entrain onto the shelf. In winterspring, the EGAB is dominated by westerly downwelling-favourable winds, and upwelling via the Flinders current is suppressed. Thus, the area is highly dynamic, with significant spatial and temporal variations in meteorology and oceanography which may drive variations in nutrient enrichment and productivity. This study represents the first intensive investigation of the primary and secondary productivity of the EGAB, and was designed to evaluate the general hypothesis that spatial and temporal variations in meteorology and oceanography in the EGAB will drive spatial and temporal variations in phytoplankton size structure, and primary and secondary productivity. It examines variations in primary and secondary productivity in the EGAB during the upwelling and downwelling seasons of 2004, and the upwelling seasons of 2005 and 2006. Daily integral productivity calculated using the vertically generalised production model (VGPM) showed a high degree of spatial variation. Productivity was low (<800 mg C m⁻² day⁻¹) in offshore central and western regions of the EGAB. High productivities (1600-3900 mg C m⁻² day⁻¹) were restricted to hotspots in the east that were influenced by the upwelled water mass. There was a strong correlation between the depth of the euphotic zone and the depth of the mixed layer that suggested that ~50% of the euphotic zone lay below the mixed layer depth. As a result, high rates of primary productivity did not require upwelled water to reach the surface. A significant proportion of total productivity in the euphotic zone (57% in 2005 and 65% in 2006) occurred in the upwelled water mass below the surface mixed layer. This result has implications for daily integral productivities modelled with the VGPM, which uses surface measures of phytoplankton biomass to calculate productivity. Macro nutrient concentrations could not be used to explain the difference in the low and high productivities (silica >1 μmol L⁻¹, nitrate/nitrite >0.4 μmol L⁻¹, phosphate >0.1 μmol L⁻¹). Mixing patterns or micro-nutrient concentrations are possible explanations for spatial variations in primary productivity in the EGAB. On a global scale, daily rates of primary productivity of the EGAB lie between the highly productive eastern boundary current upwelling systems, and less productive coastal regions of western and south eastern Australia, and the oligotrophic ocean. However, daily productivity rates in the upwelling hotspots of the EGAB rival productivities in Benguela and Humbolt currents. Temporal variation in mixing and primary productivity was examined in upwelling influenced nearshore waters off south western Eyre Peninsula (SWEP) in the EGAB. Mixing/stratification in the region was highly temporally variable due to the unique upwelling circulation in summer/autumn, and downwelling through winter/spring. Highest productivity was associated with pwelled/stratified water (up to 2958 mg C m⁻² d⁻¹), with low productivity during periods of downwelling and mixing (~300-550 mg C m⁻² d⁻¹), yet no major variations in macro-nutrient concentrations were detected between upwelling and downwelling events (silica >1 μmol L⁻¹, nitrate/nitrite >0.4 μmol L⁻¹, phosphate >0.1 μmol L⁻¹). We hypothesise that upwelling enriches the region with micro-nutrients. High productivity off SWEP appears to be driven by a shallowing of mixed layer depth due to the injection of upwelled waters above Z[subscript]cr. Low productivity follows the suppression of enrichment during downwelling/mixing events, and is exacerbated in winter/spring by low irradiances and short daylengths. Phytoplankton abundance and community composition was also examined in the shelf waters of the EGAB. Phytoplankton abundances were generally higher in near shore waters compared with offshore waters, and during the summer/autumn upwelling season compared with the winter/spring downwelling season. Three distinctly different phytoplankton communities were present in the region during the upwelling and downwelling seasons of 2004, and the upwelling season of 2005, with distinctions manifest in variations in the abundance of dominant types of phytoplankton, and differences in average cell sizes. In summer/autumn, waters influenced by upwelling were characterised by high phytoplankton abundances (particularly diatoms) and larger average cell sizes, while the warmer high-nutrientlow- chlorophyll (HNLC) waters in the region had lower phytoplankton abundances and smaller average cell sizes. The winter/spring community was made up of low abundances of relatively large cells. Diatoms always dominated, but evidence of Si limitation of further diatom growth suggests there may be an upper limit to diatom productivity in the region. The maximum observed diatom concentration of ~164,000 cells L⁻¹ occurred in February/March 2004, in an area influenced by the upwelled water mass. Variations in phytoplankton biodiversity in the shelf waters of southern Australia appear to be related to variations in the influence of upwelling in the region. Meso-zooplankton abundance and community composition was examined in the coastal upwelling system of the EGAB. Spatial and temporal variations were influenced by variations in primary productivity and phytoplankton abundance and community composition, which were driven by variations in the influence of upwelling in the region. Peak meso-zooplankton abundances and biomass occurred in the highly productive upwelling influenced nearshore waters of the EGAB. However, abundances were highly variable between regions and years, reflecting the high spatial and temporal variations in primary productivity and phytoplankton abundance that characterise the shelf waters of the region. Spatial and temporal variations in community composition were driven by changes in the abundance of classes of meso zooplankton common to all regions in both years of this study. Meroplanktonic larvae and opportunistic colonizers dominated the community through the upwelling season, in response to increased primary productivity and phytoplankton blooms. Differences in community composition between upwelling influenced waters and the more HNLC regions appear to be reflected in the relative abundances of cladocera and appendicularia, with cladocera more abundant in productive upwelling influenced areas, and appendicularia thriving in the more HNLC regions of the EGAB. Highest potential grazing rates in the EGAB occurred in nearshore regions with highest mesozooplankton biomass, most likely in response to the high phytoplankton biomass that occurs in the same regions. Peak meso-zooplankton grazing rates in the EGAB were ~80% less than those measured in south west Spencer Gulf in March 2007, and ~35% greater than grazing rates in the Huon Estuary in February 2005. Productivity in the EGAB shows significant spatial and temporal variation, with changes reflecting regional and seasonal variation in meteorology and oceanography, and the water masses present in the region. The overall productivity of a summer/autumn upwelling season was highly dependent on within-season variations in wind strength and direction, which dictate the number, intensity, and duration of upwelling events. Rates of primary productivity measured in the EGAB at a given time depended on the meteorological and oceanographic conditions in the region in the lead up to, and during, the sampling event. We hypothesise that during upwelling events, high productivity in the EGAB is driven by the enrichment of waters above Z[subscript]cr, but below the surface mixed layer, with micro-nutrients. Low productivity within summer/autumn upwelling seasons follows the suppression of this enrichment during downwelling/mixing events, and the overall productivity of the upwelling season will depend on the number, duration and intensity of these downwelling/mixing events. Low productivity during winter/spring is driven by the absence of upwelling, low irradiances and short daylengths. / Thesis (Ph.D.) - University of Adelaide, School of Earth and Environmental Sciences, 2009

[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.

Submitted by Biblioteca de Pós-Graduação em Geoquímica BGQ (bgq@ndc.uff.br) on 2016-09-19T17:07:03Z No. of bitstreams: 1 Tese UFF-UPMC Douglas Lessa.pdf: 6010651 bytes, checksum: 86b3d1d49b00abc23751b8883b42dfe0 (MD5) / Made available in DSpace on 2016-09-19T17:07:03Z (GMT). No. of bitstreams: 1 Tese UFF-UPMC Douglas Lessa.pdf: 6010651 bytes, checksum: 86b3d1d49b00abc23751b8883b42dfe0 (MD5) / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / Universidade Federal Fluminense. Instituto de Química. Programa de Pós-Graduação em Geociências - Geoquímica. Niterói, RJ / A presente tese teve o objetivo de reconstruir a paleoceanografia do Sistema de Ressurgência de Cabo Frio (SRCF) nos últimos 12.000 anos através da utilização de proxies ecológicos (comparação entre as assembleias do SRCF com as assembleias das áreas adjacentes com diferentes feições oceanográficas) e geoquímicos de foraminíferos planctônicos, além de obter maior conhecimento sobre a distribuição das espécies sob diferentes configurações oceanográficas, e avaliar e aplicar a recente metodologia de ablação a laser + ICP-MS para análises elementares em carbonatos de foraminíferos. Para isso, 34 topos de box-cores englobando o SRCF e as áreas adjacentes nas bacias de Santos e Campos e dois testemunhos a gravidade foram usados. O agrupamento das assembleias na Margem Continental do Rio de Janeiro (MCRJ) indicou a ocorrência de quatro principais biofáciess espacialmente bem-separadas: biofácies A - talude da bacia de Campos (contribuição de espécies tropicais e subtropicais caracterizando a frente da Corrente do Brasil, CB), biofácies B - bacia de Santos (maiores contribuições de espécies relacionadas à produtividade, caracterizando sinal de mistura de massas de água costeiras produtivas e oceânicas oligotróficas), biofácies C – setor norte do SRCF (contribuições de G. ruber e Globigerina bulloides, caracterizando ambiente de ressurgência com frequentes atenuações por águas quentes) e a biofácies D – setor sul do SRCF (contribuição de espécies indicadoras de águas frias e produtivas, caracterizando uma configuração influenciada pela ressurgência Ekman). Além disso, a distribuição espacial de Globoturborotalita rubescens revelou preferencia desta espécie por águas de plataforma continental e Globigerinella calida sendo associada a pós-ressurgência. Os testemunhos CF10-01B (mais distante da costa) e CF10-09A (mais próximo da costa) cobrem os últimos 11,5 e 7,1 ka cal, respectivamente sendo o primeiro mais influenciado pela Corrente do Brasil, expressando um sinal mais fraco da ressurgência que o segundo. No testemunho CF10-01B, o 18O de G. ruber foi mais variável que o 18O de G. bulloides apresentando dois períodos de diminuição após 9,0 ka cal AP e após 4,0 ka cal AP, enquanto o 18O de G. bulloides diminui após 9,0 ka cal AP e permanece constante até o topo. No testemunho CF10-09A, o 18O das duas espécies variaram de forma antagônica com uma mudança entre 5,0 e 4,5 ka cal AP onde o 18O de G. ruber diminui de -0,4 para -1,0 ‰ e o 18O de G. bulloides aumenta de -0,8 para 0,0 ‰. Os resultados da razão Mg/Ca obtidos pelo método de ablação a laser indicaram uma heterogeneidade intra-câmara que resultou em uma incerteza de 1,49°C para reconstruções com G. ruber e 0,6°C para G. bulloides, assim como amplitudes individuais de 3,0 a 4,0 mmol/mol para G. ruber e de 3,0 a 5,0 mmol/mol para G. bulloides e diferenças significativas entre a última câmara (f) e as anteriores (f-1 e f-2) para as duas espécies. Tais efeitos foram associados ao efeito vital de simbiontes, a grande amplitude de temperatura existente sazonalmente no SRCF e a migração das espécies para águas mais profundas durante a reprodução. As razões Mg/Ca obtidas pelo método clássico foram geralmente mais altas que as razões obtidas pelo método de ablação a laser (LA-ICP-MS) mas se aproximaram e apresentaram variação temporal semelhante aos valores médios obtidos nas câmaras f-1 e f-2. Dessa forma podemos usar a razão Mg/Ca média das câmaras f-1 e f-2 para reconstruções de paleotemperatura de superfície, habilitando também a utilização da diferença entre as razões Mg/Ca das câmaras anteriores e final de G. ruber para reconstruir a estratificação da água. Entretanto, a diferente variabilidade entre a razão Mg/Ca da câmara f de G. ruber e a razão média de G. bulloides indicou possíveis sucessões sazonais, o que nos fez associar as temperaturas reconstruída por G. bulloides como temperaturas da camada de máximo de clorofila, podendo ser associada a intensidade da ressurgência. O período de variação do nível do mar (11,5 – 6,0 ka cal AP) foi marcado pela presença de águas frias, produtivas e homogêneas associadas possivelmente à ressurgência costeira cuja contribuição diminuiu à medida que a transgressão seguia e a frente da CB se aproximava, alcançando um primeiro máximo entre 7,0 e 6,0 ka cal AP no ponto 1 e entre 6,0 e 5,5 ka cal AP no ponto 9, marcado por águas quentes na superfície e frias na subsuperfície. Entre 5,5 e 3,5 ka cal AP, a ressurgência gradualmente se intensifica com maiores efeitos próximo a costa e mais restrita a subsuperfície na porção distal. A influência costeira apresenta um aumento em 5,0 ka cal AP na porção proximal e 4,0 ka cal AP na região distal. Entre 3,5 e 2,5 ka cal AP um forte sinal de águas quentes pouco estratificadas foi observado com maior influência de águas oligotróficas no ponto 9 e mistura de águas costeiras e oceânicas no ponto 1. Após 2,5 ka cal AP, o SRCF adquire suas configurações atuais marcadas por eventos intensos de ressurgência na porção proximal da plataforma e mais restritos a subsuperfície na porção distal. Isso pode ser associado ao fortalecimento da ZCAS ligado a intensificação da monsão Sulamericana no Holoceno Superior devido ao aumento da insolação de verão. / This thesis aimed to rebuild the palaeoceanography of Cabo Frio Upwelling System (CFUS) in the last 12,000 years through the use of ecological (comparison between the CFUS assemblages and adjacent areas assemblages with different oceanographic features) and geochemical proxies of planktonic foraminifera, and obtain more knowledge about the distribution of species under different oceanographic settings, and evaluating and implementing the recent LA-ICP-MS methodology for elemental analysis in foraminifera carbonates. For this, 34 box-cores tops encompassing the CFUS and adjacent areas in the Santos and Campos basins and two gravity cores were used. The group analysis of the assemblages in the Rio de Janeiro Continental Margin (RJCM) indicated the presence of four major biofacies spatially well separated: biofacies A - Campos Basin continental slope (contribution of tropical and subtropical species characterizing the Brazil Current front, BC), biofacies B - Santos basin (largest contributions of productivity related species, characterizing a signal of mixing of coastal productive and oceanic oligotrophic waters), biofacies C - northern sector of CFUS (G. ruber and contributions of Globigerina bulloides, featuring environment with frequent attenuated upwelling by warm water intrusions) and biofacies D - southern sector of CFUS (contribution of cold and productive waters species, featuring the Ekman upwelling setting). In addition, the spatial distribution of Globoturborotalita rubescens revealed preference of this species for continental shelf waters and Globigerinella calida being associated with post-upwelling conditions. The cores CF10-01B (offshore) and CF10-09A (inshore) covered the last 11.5 and 7.1 ka cal, respectively being the first most influenced by the Brazil Current and expressing a weaker upwelling signal than the second. In the core CF10-01B, the G. ruber 18O was more variable than the G. bulloides 18O with two decreases after 9.0 ka cal AP and after 4.0 ka cal BP, while the 18O of G. bulloides decreased only after 9.0 ka cal AP and remains constant up to the top. In the core CF10-09A, the 18O of the two species varied opposite with a change between 5.0 and 4.5 cal ka AP where the 18O G. ruber decreases from -0.4 to -1.0 ‰ and 18O of G. bulloides increases from -0.8 to 0.0 ‰. Mg/Ca ratio results by laser ablation method indicated heterogeneity intra-chamber which resulted in uncertainties for reconstructions up to 1.49°C for G. ruber and up to 0.6°C for G. bulloides as well as individual amplitudes from 3.0 to 4.0 mmol/mol to G. ruber and 3.0 to 5.0 mmol/mol to G. bulloides and significant differences between the last chamber (f) and previous (f-1 and f-2) for both species. These effects were associated with the symbiont vital effect, the wide seasonal temperature range in the SRCF and species migration to deeper waters during reproduction. The Mg/Ca ratio generated by the traditional method were generally higher than the ratios Mg/Ca reconstructed through LA-ICP-MS, although, when compared to the average of f-1 and f-2 chambers only, the values show similar mean and variability indicating both methods agree in reconstruction for surface paleotemperatures. It also allows the use of difference between the ratios of final and previous chamber of G. ruber for paleostratification reconstructions. However, the distinct variability between G. ruber f chamber Mg/Ca ratios and average G. bulloides Mg/Ca ratio indicated possible seasonal succession, which made us associate the temperatures reconstructed by G. bulloides to chlorophyll layer temperatures which may be associated with upwelling intensity. The sea level rise (from 11.5 to 6.0 ka cal BP) was marked by the presence of cold productive and homogeneous waters, possibly associated with coastal upwelling whose contribution gradually decreased during the course of the transgression, followed by the penetration of BC front on the shelf, reaching a first maximum between 7.0 and 6.0 ka cal BP offshore and between 6.0 and 5.5 ka cal BP inshore, marked by warm surface waters and cold subsurface waters. Between 5.5 and 3.5 ka cal BP, the upwelling gradually intensifies mainly inshore and restricted to subsurface offshore. An increased coastal influence is also detected with peaks at 5.0 ka cal BP inshore and 4.0 cal ka BP offshore. Between 3.5 and 2.5 ka cal BP a strong signal of warm water was observed with greater influence of oligotrophic waters inshore and mixture of coastal and oceanic waters offshore. After 2.5 ka cal BP, the SRCF acquires its current settings marked by intense upwelling events, better expressed inshore and restricted to subsurface offshore. This change may correspond to an intensification of the SACZ linked to the strengthening of the South American Monsoon during the late Holocene due to the increase in summer insolation.

Ao largo da costa oeste da Am´erica do Sul o sistema de ressurg^encia costeira apresenta uma excepcional produtividade, um resultado da alta efici^encia do ecossistema biol´ogico em converter a produ¸c~ao prim´aria em biomassa. Esses processos qu´?micobiol ´ogicos s~ao fortemente modulados pelo ambiente f´?sico da regi~ao. Por exemplo, durante eventos do El-Ni~no a produtividade pesqueira ´e fortemente prejudicada em resposta a uma inibi¸c~ao da ressurg^encia costeira. Apesar disso ser um fato j´a bastante conhecido desde ´epocas pr´e-colombianas, muita d´uvida ainda persiste sobre o mecanismo pelo qual o sistema costeiro ´e afetado por esses fen^omenos de grande escala. O presente trabalho foi realizado com o objetivo de se contribuir com esse conhecimento, estudando como ocorreram as mudan¸cas do sistema durante recentes eventos El Ni~no, principalmente na escala intrasazonal. Nessa investiga¸c~ao foram utilizadas diferentes metodologias de an´alise de dados para identificar a natureza dos for¸cantes de oscila¸c~oes significativas observadas durante o El Ni~no 1997-1998. Tamb´em foi investigado se essas oscila¸c~oes foram for¸cadas remotamente e se propagaram como ondas aprisionadas na costa; quais foram suas propriedades espaciais e sua propaga¸c~ao longo da costa. A primeira parte do trabalho consiste na an´alise da variabilidade temporal e a caracteriza¸c~ao das flutua¸c~oes de baixa freq¨u^encia ocorridas durante eventos El Ni~no. Essa an´alise faz uso do espectro de ondeleta aplicado a s´eries temporais longas de dados do n´?vel do mar de esta¸c~oes costeiras distribu´?das ao longo da costa sul do Equador, costa do Peru e costa norte do Chile. O espectro de ondeleta cruzada e o espectro da coer^encia foram usados para avaliar a import^ancia relativa das for¸cantes remota e local das varia¸c~oes do n´?vel do mar associadas com os efeitos do El Ni~no 1997-1998. Na segunda parte, as flutua¸c~oes for¸cadas remotamente foram comparadas com modelos lineares simples e o modelo de Brink e Chapman (1987) para se obter as propriedades das ondas aprisionadas na costa durante o El Ni~no Extraordin ´ario (1997-1998). Uma importante conclus~ao dessas an´alises foi a constata¸c~ao de que variabilidades intrasazonais ao largo da costa do Peru durante esse El Ni~no foi, em parte significativa, o resultado da atua¸c~ao de for¸cantes remotas e locais, associadas com ondas equatoriais incidindo na Costa Oeste da Am´erica do Sul e com o efeito do vento, respectivamente. / Off the western coast of South America, the coastal upwelling system presents an exceptional productivity, a result of the high efficiency of the biological ecosystem in converting the primary production into biomass. These chemical and biological processes are strongly modulated by the physical environment. For instance, during El Ni~no events the fishery productivity is strongly impaired in response to an inhibition of the coastal upwelling. In spite of this fact be widely known since pre-Colombian times, much doubts still persist about the mechanism by means of which the coastal system is affected by the large scale phenomena. The present work was idealized with the intention of contributing for this knowledge, studying how occurred the changes in the system during recent El Ni~no events, with emphasis on the intraseasonal scale. In this investigation, different methodologies of data analysis were used to identify the nature of the forcing which produced significant oscillations observed during the El Ni~no 1997-1998. Also, it was investigated if these oscillations were remotely forced and propagated along the coast as coastal trapped waves; what were their spatial and propagation properties. The first part of the work consists of an analysis of the temporal variability and the characterization of the low-frequency fluctuations occurred during the El Ni~no events. This analysis uses the wavelet spectrum applied to time series of sea level data collected off southern Equador, Peru and northern Chile. The cross wavelet spectrum and coherence spectrum were used to evaluate the relative importance of local and remote forcing of the sea level, associated with effects of the 1997-1998 El Ni~no. In the second part, the fluctuations remotely forced wer compared with results of simple linear models and with the model of Brink and Chapman (1987), in order to obtain the coastal trapped waves properties during that extraordinary El Ni~no event. One important conclusion of these analyses was the confirmation that the intraseasonal variability observed offo Peru during the 1997-1998 El Ni~no was, in part, the result of remote and local forcing, associated with equatorial waves and the wind effect, respectively.

O presente trabalho teve como finalidade estudar os efeitos das variações do vento resultantes de ocorrências do fenômeno El Niño-Southern Oscillation (ENSO) nos padrões da circulação superficial ao longo da costa peruana, através da análise de dados observados e de modelagem numérica. É enfocado o período 1991-2000, quando ocorreram fortes eventos La Niña (1996-97, 1998-2000) e El Niño (1997- 98). Esses eventos tiveram fortes impactos em escala global mas muito pouco se sabe sobre os impactos locais na estrutura da termoclina e no ciclo da dinâmica de Ekman ao longo da costa peruana. Os dados analisados no presente estudo foram dados coletados em duas radiais ao longo das latitudes 5 S e 15 S. O modelo oceânico utilizado foi o Modelo da Universidade de Princeton (Princeton Ocean Model-POM). As simulações numéricas foram forçadas com produtos de vento relativos ao período 1991-2000. Essas simulações reproduziram satisfatoriamente os padrões médios da circulação na região de estudo, confirmando que nas áreas próximas da costa o vento é o principal mecanismo gerador de ressurgência ou subsidência. Os resultados mostraram que durante a ocorrência do forte evento El Niño 1997-1998, nas radiais de 5 S e 15 S, houve uma drástica alteração do sistema de ressurgência costeira em resposta às variações do vento. / The objective of the present work was to study the effects of variability in the wind due to the El Niño-Southern Oscillation events in the surface circulation patterns of the Peruvian coast, by means of data analysis and numerical modeling. It is focused the period 1991-2000, when it was observed strong La Niña (1996-1997, 1998-2000) and El Niño events (1997-98). These events had strong effects worlwide but very little is known on the local impacts on the circulation, thermocline structure and the Ekman dynamics of the Peruvian coast. The data analysed in the present study were collected on transects along 5 S and 15 S. The model used was an implementation of the Princeton Ocean Model (POM). The numerical simulations were forced with wind products relative to the period of interest (1991-2000). The simulations reproduced satisfactorily the mean circulation patterns in the study area, confirming that the in the nearshore region the wind is the main driving mechanism for coastal upwelling/downwelling. The results show that during the strong 1997-1998 El Niño, a drastic alteration of the coastal upwelling system ocurred in response to the changes in the wind.

O presente trabalho teve como finalidade estudar os efeitos das variações do vento resultantes de ocorrências do fenômeno El Niño-Southern Oscillation (ENSO) nos padrões da circulação superficial ao longo da costa peruana, através da análise de dados observados e de modelagem numérica. É enfocado o período 1991-2000, quando ocorreram fortes eventos La Niña (1996-97, 1998-2000) e El Niño (1997- 98). Esses eventos tiveram fortes impactos em escala global mas muito pouco se sabe sobre os impactos locais na estrutura da termoclina e no ciclo da dinâmica de Ekman ao longo da costa peruana. Os dados analisados no presente estudo foram dados coletados em duas radiais ao longo das latitudes 5 S e 15 S. O modelo oceânico utilizado foi o Modelo da Universidade de Princeton (Princeton Ocean Model-POM). As simulações numéricas foram forçadas com produtos de vento relativos ao período 1991-2000. Essas simulações reproduziram satisfatoriamente os padrões médios da circulação na região de estudo, confirmando que nas áreas próximas da costa o vento é o principal mecanismo gerador de ressurgência ou subsidência. Os resultados mostraram que durante a ocorrência do forte evento El Niño 1997-1998, nas radiais de 5 S e 15 S, houve uma drástica alteração do sistema de ressurgência costeira em resposta às variações do vento. / The objective of the present work was to study the effects of variability in the wind due to the El Niño-Southern Oscillation events in the surface circulation patterns of the Peruvian coast, by means of data analysis and numerical modeling. It is focused the period 1991-2000, when it was observed strong La Niña (1996-1997, 1998-2000) and El Niño events (1997-98). These events had strong effects worlwide but very little is known on the local impacts on the circulation, thermocline structure and the Ekman dynamics of the Peruvian coast. The data analysed in the present study were collected on transects along 5 S and 15 S. The model used was an implementation of the Princeton Ocean Model (POM). The numerical simulations were forced with wind products relative to the period of interest (1991-2000). The simulations reproduced satisfactorily the mean circulation patterns in the study area, confirming that the in the nearshore region the wind is the main driving mechanism for coastal upwelling/downwelling. The results show that during the strong 1997-1998 El Niño, a drastic alteration of the coastal upwelling system ocurred in response to the changes in the wind.