Thesis advisor: Tara Pisani Gareau / Salt marshes provide important ecosystem services, including carbon sequestration. Permanently inundated ponds are prominent features in the marsh landscape, encompassing up to 60% of the total marsh area, but they are rarely considered in biogeochemical assessments. I investigated two ponds in Plum Island Estuary, MA to measure and analyze their metabolism. The ponds varied in size and vegetation cover. Oxygen concentrations and pH values were recorded in 15-minute intervals during the entire study period. The ponds regularly become hypoxic or anoxic during night. This is a problem for the estimation of respiration rates which are based on nighttime measurements. To investigate this potential underestimation, several approaches to estimate respiration were used. First, additional measurements of surface water concentrations of dissolved inorganic carbon were made. A comparison of respiration estimates based on oxygen and DIC changes during tidal isolation revealed a reasonable agreement for the most time but not during periods of high productivity during the day or late at night. At this point, oxygen concentrations are so depleted that a change in concentration – the indicator of respiration – is barely detectable. However, DIC based respiration rates indicate that respiration is occurring under these hypoxic/anoxic conditions. This saturation changes during periods of tidal inundation, when a nighttime peak in oxygen concentrations indicates that the flood water is relatively enriched in oxygen compared to the pond water. On three days, it was tested whether under these conditions the oxygen-based respiration rate was higher than under hypoxic conditions (i.e., during tidal isolation). The rates were indeed higher than those under tidal isolation but still not in the range of DIC-based rates. Overall, metabolic rates differed between the two ponds in magnitude, which is likely caused by different vegetation cover, but may be influenced by size, sampling period, and duration as well. / Thesis (BS) — Boston College, 2018. / Submitted to: Boston College. College of Arts and Sciences. / Discipline: Departmental Honors. / Discipline: Earth and Environmental Sciences.

Thesis advisor: Douglas Edmonds / Due to their low-lying position near the shoreline, river deltas are vulnerable to fluctuations in relative sea-level (RSL). Moreover, relatively little is known about fluvio-deltaic dynamics during RSL fall because the resulting deposits have low preservation potential. In this paper, I present a field-based study of the Goose River delta, coupled with numerical model simulations, that investigates the fluvio-deltaic response to RSL fall. The Goose River delta is a sandy fjord delta at the mouth of the Goose River located at the western end of Lake Melville, an inlet of the Labrador Sea, Canada and has experienced a RSL fall of 3 to 6 mm/yr in the past 5000 years due to post-glacial isostatic rebound. Aerial images show three abandoned delta lobes and one active lobe, suggesting that avulsions and lobe-switching occurred during RSL fall. Elevation analysis using Shuttle Radar Topography Mission (SRTM) digital elevation model (DEM) data and optically-stimulated luminescence (OSL) dating suggest that a series of downstepping terraced delta lobes formed at the mouth of the Goose River during a period of RSL fall. Similarly, Delft3D model runs show continued avulsions and formation of multiple terraced delta lobes deposited at progressively lower elevations. I show computationally that by decreasing delta lobe widths, deltas may remain aggradational during RSL fall, creating conditions favorable for lobe-switching during RSL fall. Observations from the field and model runs provide a critical link in understanding the geomorphic processes occurring during RSL fall, and in particular show that 1) incision and sediment bypass is not a necessary response to RSL fall and 2) lateral migration of a delta via avulsion can continue to occur with falling sea-level. / Thesis (MS) — Boston College, 2013. / Submitted to: Boston College. Graduate School of Arts and Sciences. / Discipline: Geology and Geophysics.

The timing of glacial-interglacial cycles shows a clear dependence on the periodic variations in the Earth’s orbital parameters. However, the Earth’s climate is an extremely complex, non-linear system, with many internal feedback mechanisms and there are still features of the climate record for which a definitive explanation remains elusive. Understanding reef history is important due to significant predicted feedbacks between changes in global climate and carbonate production via the carbon cycle; phases of rapid reef growth in shallow water areas being associated with increased release of carbon dioxide to the atmosphere. Previous work on Pleistocene reef history, investigated via reef boreholes, shows a large global expansion of reefs between 800-400ka; approximately concurrent with one of the major unexplained alterations in the climate system, the Mid-Pleistocene Transition (MPT). Quaternary reef history is usually investigated via reef boreholes, which provide limited spatial information and are subject to dating uncertainties of the order of ±100kyrs. This means that any inferences made about the relationship between reef expansion and specific changes in the climate system are not well constrained. This thesis instead, presents a novel approach to reconstructing reef growth history, using a trial site near the island of New Caledonia, in the south west Pacific. The initiation of carbonate production on shallow shelves is known to produce a signal in the surrounding deeper basins, via sediment shedding. Therefore, this research set out to independently verify the proposed expansion of the New Caledonia Barrier Reef at ~ 400ka (Marine Isotope Stage [MIS] 11) by examining the composition of turbidites deposited in the New Caledonia Trough. Deep sea sediment core MD06-3019, was collected south west of the New Caledonia Barrier Reef (22oS, 165oE; 3,500m water depth). It is predominantly composed of pelagic carbonate ooze, into which 79 sandy turbidite layers have been deposited. These layers interrupt, but do not disturb, the background sedimentation and source material from the shallow shelf, which is carried to the deep sea via submarine canyons. A core age model based principally on orbital tuning, yields a core bottom age of 1,260ka, ~MIS38. This chronology has allowed the timing of deposition of the turbidite layers within the core to be assigned to within ±10kyr. Turbidite layers vary in width (1-35cm), grain size (φ=4 to -2) and composition, containing among other shelf derived material, well preserved coral fragments from 1.26Ma through to the present day. Patterns in turbidite timing and frequency, grain size and composition (investigated via point counting, carbonate coulometry and aragonite content) have been analysed, to assess whether there are any temporal changes which may reflect variation in shallow shelf reef extent. This included the development of XRF scanning measurements for [Sr], as a new proxy for the aragonite content of samples. A calibration line with the equation: Aragonite %=0.0011* Sr count +2.64 (R2 =0.6105, p-value < 0.001) was obtained for turbidite samples from sediment core MD06-3019. The method shows significant promise as a new proxy for quickly establishing the aragonite content of sediment samples. Corroborating the work of previous investigators, turbidites deposited since MIS11 show an increase in average bulk carbonate and aragonite content, a greater dominance of shallow water bioclasts and a higher occurrence of coral fragments. Additionally, both coarse and fine grained turbidites are present, whereas directly before this period only fine grained turbidites occur. However, there is another significant shift in depositional style further back in the record. Prior to MIS23 both coarse and fine grained turbidites are present, the average carbonate content of turbidite layers is higher and there is a greater dominance of shallow water biota. Coral abundance for turbidites at the base of the core can equal values for turbidites at the top of the core. These results challenge the assumption that the only significant evolution on the western New Caledonia margin over the last 1.2Myrs was the expansion of the barrier reef at MIS11. This suggests that the history of the western New Caledonia margin may be more complicated than initially anticipated. These temporal variations in turbidite deposition are interpreted as reflecting changes in the level of carbonate production on the shallow shelf over the course of the 1.26Myr record. Shallow water carbonate production having decreased substantially during the period MIS23-MIS11. There are many possible controls on the shallow water carbonate production; such as: sea surface temperature and salinity, sea-level and nutrient availability. However, it is hypothesised that the principal control is glacial-interglacial sea-level change. It is proposed that prior to MIS23 sea-level was high enough during certain interglacial periods for significant carbonate production to occur on the shelf. However, from MIS23 onwards the climate proceeded into a period of ‘lukewarm’ interglacials which were both cooler and had lower sea-levels. It is hypothesised that during this period sea-level did not rise enough during highstands to flood the shelf sufficiently to allow for significant shallow water carbonate production. The high sea-levels of the long, warm MIS11then allowed for the expansion of the barrier reef (perhaps on substrates provided by former siliciclastic coast lines, deposited between MIS23-11) and its continuation during subsequent interglacial periods until the current day. This pattern of shallow shelf carbonate production is similar to those proposed for the Belize margin and the Gulf of Papua over the last 1.2Myrs. This thesis provides one of the first detailed investigations of gravity deposits in the New Caledonia Trough, providing information on their composition and timing over an unprecedented 1.26Myr time period. This study demonstrates that deep sea turbidites, sourced from shallow shelf areas, can be used to help reconstruct tropical reef growth histories. The results corroborate the work of previous researchers in the area and provide new insights into the history of reefs along the western New Caledonian margin. The main advantage of this method, compared to traditional borehole techniques, is the 10-fold reduction in the age uncertainty of events, to ±10 kyr. In addition, because turbidite material is sourced from a wide area along the coast, the method is able to provide information on reef history over a larger spatial area than single reef boreholes. This method can now be extended globally to help improve knowledge of the timing and history of tropical reef growth during the Quaternary. This will enable a better understanding of how reefs have impacted on, and been affected by, changes in climate, linked by feedbacks mechanisms via the global carbon cycle.

O presente estudo foi desenvolvido em uma turfeira localizada no baixo curso do rio Ribeira de Iguape, Litoral Sul de São Paulo com o objetivo de reconstituir os paleoambientes e as possíveis variações ambientais ocorridas na área por meio da análise de palinomorfos e das características dos sedimentos do testemunho de sondagem de 520 cm de profundidade. A análise de bio e geoindicadores permitiu reconstituir parte da história de evolução sedimentar holocênica da área. Para isso a análise foi fundamentada sob o ponto de vista da biogeografia, envolvendo a interpretação e correlação entre as variáveis: sedimentológicas, espongológica, foraminíferos, palinológicas e isótopos de 13C. Antes de 7.300 anos cal AP as características sedimentológicas evidenciam o início da sedimentação da planície de inundação onde foi depositado espículas de esponjas continentais de O. navicella, é provável que o aporte de água doce na área de estudo tenha causado o desaparecimento de espécies de foraminíferos, tecamebas e ostracodes pela dissolução das carapaças em águas com pH ácidos, o mesmo aporte que pode ter lixiviado o material polínico, pois os sedimentos são arenosos. Os elementos isotópicos com valores de -27,6 evidenciam que a matéria orgânica é de origem fluvial. Por volta de 7.300 anos AP (fácies 430 cm) o NRM cruzou o zero pela primeira vez no Holoceno. Essa interpretação é corroborada pela chegada de espículas de origem marinha nos sedimentos. Além disso, no nível de 430 cm observa-se redução da concentração de esponjas de água doce. Os valores de 13C - 25,9 indicam que a origem da matéria orgânica é mista. Entre 7.200 e 6.430 anos cal AP ocorreu novamente uma rápida regressão do NRM verificado pela presença frequente de esponjas continentais e raríssima presença de espículas marinhas. A área era colonizada por plantas típicas de ambientes sob influência marinha e fluvial como Asteraceae, Poaceae, Araceae, Begoniaceae, Ulmaceae, Arecaceae Bactris sp. (encontrada em áreas alagadas e/ou FPa). Antes de 6.430 anos cal AP ocorre o início da segunda e mais duradoura fase de transgressão marinha caracterizada pela espongofácies marinha e pela queda nas porcentagens de todos os táxons polínicos. O pico da transgressão ocorre antes de 5.124 anos cal AP nesse momento foi depositado material espicular marinho e continental evidenciando o ambiente estuarino, onde plantas herbáceas adaptadas a esse ambiente ainda colonizavam essa área com concentrações como Amaranthaceae. Posteriormente, o NRM decai lentamente chegando ao nível zero atual, aqui as porcentagens de espículas marinhas decaem paulatinamente até a profundidade de 225 cm. Por volta de 3.200 anos cal AP (médias das idades de 145 cm) o ambiente já se comportava como um pântano, há aumento na concentração de Bignoneaceae (Tabebuia), Cluseaceae (Clusia) e novamente Amaranthaceae sugerem a colonização de FPa. Plantas do gênero Tabebuia sp. destacam-se por se agruparem em áreas alagadas. Posteriormente, o aumento significativo nas concentrações polínicas de todos os táxons, principalmente dos indicadores de FPaT, indicam o desenvolvimento dessa formação vegetal. Devido à complexidade desse ambiente por causa de sua morfodinâmica há necessidade de cuidados na interpretação dos resultados, pois os registros de mega-eventos podem ser confundidos, mascarar ou levar as interpretações paleoambientais inadequadas. Por isso, o uso de multiindicadores e o conhecimento dos processos mostraram-se fundamentais e foi possível obter uma excelente resposta. / This study was developed in a peat bog located on the lower course of Ribeira river, South Coast of Sao Paulo, in order to reconstruct the paleoenvironments and possible environmental changes occurred in the area through analysis of palynomorphs and the characteristics of the sediments drill core depth of 520 cm. The analysis of bio and geoindicators allowed to reconstruct a part of the history of the Holocene sedimentary evolution of the area. The analysis was based on the point of view of Biogeography, involving the interpretation and correlation between variables: sedimentological, belong sponge, foraminifera, pollen and 13C isotopes. Before 7300 cal years BP the sediment characteristics show the beginning of sedimentation of the floodplain where it was deposited spicules of sponges continental O. navicella, it is likely that the freshwater inflow in the study area has caused the disappearance of species of foraminifera, ostracods and thecamoebian by dissolving the shells in waters with acidic pH, the same approach that may have leached the pollen material, because the sediments are sandy. The isotopic elements with values of -27.6 show that the organic matter is of fluvial origin. Around 7300 years BP (430 cm depth) NRM crossed zero for the first time in the Holocene. This interpretation is corroborated by the presence of spicules in the sediments of marine origin. Furthermore, at the level of 430 cm was observed a reduction of the concentration of freshwater sponges. 13C values of -25.9 indicate that the source of the organic matter is mixed. From 7200 until 6430 years cal AP occurred a rapid regression of NRM verified by the frequent presence of continental sponges and extremely rare presence of marine spicules. The area was colonized by plants typical of marine and fluvial environments under influence like Asteraceae, Poaceae, Araceae, Begoniaceae, Ulmaceae, Arecaceae Bactris sp. (found in flooded and / or FPa areas). Before 6430 years cal AP occurred the beginning of the second and more lasting phase of marine transgression characterized by marine espongofácies and for the decreased in percentages of all pollen taxa. The peak transgression occurs before 5124 years cal AP, when was deposited marine and continental espicular materials evidencing the estuarine environment, where herbaceous plants adapted to this environment yet colonized this area with concentrations as Amaranthaceae. Subsequently, the NRM decays slowly coming to the current zero level. Here the percentages of marine spicules decay gradually to a depth of 225 cm. Around 3200 cal years BP (mean ages of 145 cm) the environment has behaved like a swamp, there is an increase in the concentration of Bignoneaceae (Tabebuia), Cluseaceae (Clusia) and again Amaranthaceae suggest colonization of FPa. The genus Tabebuia sp. stands out for getting together in wetlands. Later, the significant increase in the pollen concentrations of all taxa, especially indicators of WPF, indicates the development of this plant formation. Due to the complexity of this environment because of their morphodynamics, caution is necessary in interpreting of the results because the records of megaevents can be confused, to mask or take inadequate paleoenvironmental interpretations. Therefore, the use of multi-indicators and the knowledge of the process were essentials and it was possible to obtain excellent response.

Coastal saltmarshes are vital ecosystems because (a) they physically buffer the land against storms and flooding from the sea and (b) ecologically they are high-productivity systems in estuaries and marine coastlines that shelter and support fish and bird populations. Saltmarshes are highly sensitive to sea level change. Any saltmarshes are now threatened by rising sea level, but how they will respond and at what rate is unclear. Managing saltmarshes is therefore necessary, but requires a good understanding of their development in order to predict how they might respond to sea level change. Current management practice in the UK is mainly managed realignment landward and future scenarios are predicted with computer models. Both use the hypothesis of facilitation succession, whereby saltmarsh progrades seawards. An alternative hypothesis is saltmarsh development by transgression landward due to rising sea level. This thesis critically examines how saltmarshes have developed under different sea-level change regimes in order to gain an insight into how they are likely to be affected by future sea level rise. Using established micropalaeontological techniques, Foraminifera tests and Ostracoda shells were extracted from sediment cores taken from saltmarshes representing a range of sea level change histories during the Holocene. Sampling of modern environments allowed saltmarsh vegetation zones to be characterised by foraminiferal and ostracod assemblages which were then used to reconstruct the development of saltmarshes over time as preserved in the cores. Sediment layers in the cores were dated using three techniques: Optically Stimulated Luminescence (OSL), radio carbon (14C) and 137Cs / 210Pb. The latter hypothesis is supported in southern England where marine transgression caused saltmarshes to migrate landwards, in contradiction to the facilitation succession hypothesis. In Scotland saltmarshes advanced seawards but due to a marine regression. Future studies should explore the applicability of these findings to saltmarshes outside the British Isles.

Floodplain fens represent an important component of the global carbon cycle through their role in carbon sequestration. Peat development depends upon rate of production exceeding rate of decomposition, yet there is little understanding of the effects of sea-level rise on these processes in lowland environments. This thesis investigates the impacts of projected sea-level rise from climate change on carbon storage in floodplain fens, using a combination of field, laboratory and simulation modelling techniques. A gradient of saline influence was determined for the Broads, UK, based on analysis of water chemistry and published water level data, allowing for the application of a space-for-time substitution technique. Increased water level had a positive effect on above-ground production of Phragmites australis (cav.) Trin. Ex Steud. (1841) - perhaps because water stress limits important photosynthetic processes. An increase in salinity had a negative effect on the growth of P. australis, probably due in part to osmotic stress. Previous management practice significantly impacted on production - as uncut vegetation became less productive with time. There was evidence to suggest that sea-level rise may lead to faster decay rates, but this will be partially offset by litter quality. Saline influenced sites had lower carbon accumulation potentials. Radiometric dating confirmed that these sites have lower carbon sequestration rates - probably as a result of increased mineral deposition in floodwaters. Carbon stock ranged between 33 and 144 kt C but depended greatly on peat depth and bulk density. Results from both field data and the model indicated that peat accretion in the Broads would not offset projected sea-level rise. Floodplain fen development under the influence of sea-level rise will be dependent on the majority of assimilate being allocated to above-ground vegetation.

A variação do Nível Médio do Mar (NMM) é um assunto de grande importância para a sociedade, pois a sua elevação, que é verificada em diversas estações de monitoramento no mundo, pode trazer diversos prejuízos para o homem. Aponta-se como razão principal deste fenômeno a elevação da temperatura média do planeta causada pelo aumento da concentração dos Gases de Efeito Estufa (GEE). Em Cananéia, litoral sul do estado de São Paulo, o nível do mar vem sendo monitorado há mais de 50 anos através de um marégrafo. A estação também conta, desde o ano de 2002, com um receptor do Global Positioning System (GPS) cuja antena está instalada em um pilar adequado, engastado na rocha. Além disso, um gravímetro geodinâmico foi instalado junto à estação para, associado ao marégrafo e ao receptor GPS, contribuir para a determinação da variação absoluta do NMM, que representa a diferença entre os movimentos do nível do mar e da crosta. Com os dados maregráficos durante o período de 1954 a 2004 foi possível determinar um aumento relativo do NMM de 4,2 mm/ano, com a determinação de um modelo global de marés oceânicas que melhor se adaptou à região. A análise das observações gravimétricas permitiram a determinação de um modelo de maré terrestre para a estação, porém a deriva instrumental impediu a detecção de alguma tendência para a crosta. Já os resultados obtidos através do processamento das observações GPS entre os anos de 2004 e 2006 através do método Precise Point Positioning (PPP) determinaram um rebaixamento da crosta de 1,59 mm/ano. No entanto, este curto período de observações processadas impede que se conclua algo de definitivo sobre o movimento da crosta. / The Mean Sea Level (MSL) variation is very important for the society because its elevation, verified in many monitoring stations around the world, causes several damages for the humanity. It\'s pointed how principal reason of this phenomena the elevation of the world mean temperature due to greenhouse gases concentration increasing. At Cananéia, south coast of São Paulo, the sea level has been monitored for more than 50 years by a tide gauge. The station has since 2002 a GPS receiver whose antenna is installed in a stable pillar fixed in the bed rock. Moreover a geodynamic gravitymeter installed at the site of the station, out of the tide gauge and the GPS receiver, contributes for the determination of absolute variation of the MSL that represents the difference between the movement of the sea level and the crust. With tide gauge observations from 1954 to 2004 it was possible to find a relative increasing of MSL of 4.2 mm/year with the determination of the ocean tide model that best fit in the region. The analysis of gravimetric observations allowed the determination of an earth tide model but the instrumental drift hindered the detection of some crust tendency. However the results obtained by processing GPS observations between 2004 and 2006 by Precise Point Positioning showed a decrease of the crust of 1.59 mm/year. However, any definite conclusion on the crust movement need a longe period of observations with GPS.

The ability to detect buried mines on the seafloor remains one of the most important tasks in mine countermeasures. As such, there is a vested interest in the development of predictive models of mine burial. This research was conducted in support of the Office of Naval Research Program in Mine Burial Prediction. Repeat high-resolution multibeam bathymetry data were collected over the Indian Rocks Beach (IRB) mine burial experiment site during January through March of 2003, in order to observe in situ scour and burial of instrumented inert mines and mine-like cylinders. These data were also used to test the validity of the VIMS 2D mine burial model. A set of six high-resolution multibeam surveys were collected over the IRB experiment site. Three study sites within the IRB site were chosen: two fine sand sites, a shallow one located in ~ 13 meters of water depth and a deep site located in ~ 14 meters of water depth; and a coarse sand site in ~ 13 meters. Results from these surveys indicate that mines deployed in fine sand are upwards of 74.5% buried within two months of deployment. Mines deployed in the coarse sand showed a lesser amount of scour, burying until they presented roughly the same hydrodynamic roughness of the surrounding rippled bedforms. In general, scour around the mines formed pits ~ 0.30 meters deep, with the most pronounced scour occurring at the ends of the mine. The multibeam data were also used to test the VIMS 2D mine burial model, which estimates percent burial of cylindrical mines based on predictions of wave-induced scour. The model proved valid for use in areas of fine sand, sufficiently predicting burial over the course of the experiment. In the area of coarse sand, the model greatly overpredicted the amount of burial. This is believed to be due to the presence of ripples around the mines, which affect local bottom morphodynamics and are not accounted for in the model. This issue is currently being addressed by modelers.

The aim of paleoenvironmental studies is to reconstruct characteristics of the past environment from fossil assemblages preserved in sedimentary strata. Thus, studies of modern surface assemblages, quantitatively correlated to the environmental parameters, are required before reliable interpretations can be made. For this dissertation, two different techniques were applied in two case studies: a reconstruction making use of a benthic foraminiferal transfer function from the intertidal marshes in the eastern Mississippi Sound, Alabama/Mississippi, and a qualitative reconstruction of ocean current activity on the Western Australian shelf. Modern salt-marsh foraminifera were collected from Grand Bay, Pascagoula, Fowl River, and Dauphin Island across several elevation transects and different salinity regimes. Cluster analysis yielded nine dead biofacies and five live assemblages from Open Estuarine to Upland Transition. Canonical correspondence analysis indicated a strong relationship between distributions of dead biofacies and elevation. Both dissolution of calcareous species in the organic marsh sediment and the long-term accumulative nature of the dead assemblage favored the use of non-estuarine dead assemblages. A Weighted Average-Partial Least Squared transfer function was applied to the surface data and yielded a Root Mean Squared Error of Prediction (RMSEP) of 0.14 m, which represents 33% Mean Range of Tide at Grand Bay and 39% at Dauphin Island. The transfer function was applied to two sedimentary cores from Grand Bay and two from Dauphin Island, which revealed disparate developments between the regions during the last 1,900 years. While both Dauphin Island cores indicated relative sea-level trends aligned with other Gulf of Mexico studies, Grand Bay was likely impacted by a river avulsion event disconnecting Grand Bay from fluvial sediment influx, and by the erosion of a protective headland, Grand Batture Island. Sediments spanning the last ~100 years contained increased abundances of low marsh foraminifera likely associated with coastline erosion, which was most prominently displayed by a lithology shift towards grey silt in the Dauphin Island cores. Surface carbonate sediments from Western Australia’s Northwestern Shelf and Carnarvon Ramp were collected from 127–264 m water depth. Foraminiferal assemblages changed between 127 m and 145–264 m due to rapidly decreasing water temperature in the thermocline, and loss of sufficient light for support of “larger” benthic foraminifera. Latitudinal differences were likely caused by three factors: (1) limited influence of the warm Leeuwin Current to support tropical taxa at the sampled depths, (2) reduced habitat diversity on the narrow Carnarvon Ramp compared to surrounding shelves, and (3) differing water-mass characteristics. The gathered information was used to interpret the assemblages from a Carnarvon Ramp core (total depth 300 m), providing insight into the activity of the warm, surficial Leeuwin Current for the last 3.54 My (Pliocene). Abundant infaunal taxa were inferred to indicate low oxygenation, increased supply of organic matter, and high sea-surface productivity during the absence of the Leeuwin Current above the coring site. Dominance of epifaunal species signified higher oxygenation at the sediment-water interface when upwelling of nutrient-rich waters was effectively suppressed by the Leeuwin Current. Around 1.14 Ma, waning of hypoxic conditions was initiated until a more substantial change was marked at 0.91 Ma. Suspension-feeding sponges became common sediment constituents during a Leeuwin Current flow optimum at ~0.6 Ma. The epifaunal taxa dominance persisted on the modern shelf, yet short episodes of infaunal peaks were likely caused by lateral shifts and fluctuating influence of the Leeuwin Current during more intense glacial cycles.

Tongatapu coastal zone vulnerability assessment study was conducted to examine the degree of current and future risks of projected climate change and sea level rise on the coastal zone of the main island of the Kingdom of Tonga-Tongatapu. Inundation, and flooding hazards generated by tropical cyclone storm surges are the common threats to Tongatapu coastal towns and villages because of their low-lying settings. Flooding problems are exacerbated by the social trends of population growth and migration from the outer islands of the Kingdom, to Tongatapu the main island where the capital town of the Kingdom, Nuku'alofa is located. Other threats include beach erosion, saltwater intrusion, and seawater spraying of coastal vegetations and properties. A survey of the local people of Tongatapu, mapping of vulnerable areas with GIS, and using my local knowledge of the island coastal zone were the three methods were used to conduct this study. The main objective of this research was to assess the vulnerability of the coastal zone of Tongatapu to local impacts of inundation and flooding hazards associated with climate and sea-level rise related risks. The results of the survey indicated that more than 95% of the respondents agreed that the coastal zone of Tongatapu is vulnerable to inundation and flooding risks generated by tropical cyclones that visit Tongatapu coastal water every year, based on their recollection, knowledge, and experienced of the past storm events that hit Tongatapu. GIS work showed that those coastal towns and villages of Tongatapu that are located in areas less than 5 meter above sea level are vulnerable to the local impacts of inundation and flooding hazards. It is concluded that the yearly visited tropical cyclones to Tonga that are actually hit Tongatapu coastal zone had increasing the vulnerability of the coastal towns and villages of Tongatapu that are located in areas below 5 meters above sea level to inundation and flooding hazards associated with climate change and sea level rise related risks. Other possible cause might be the gradual uplifted of the south coast of Tongatapu due to ongoing earthquake activities in Tonga since the last 200 years. But in facts more research it has to be done to confirm this argument. The response to the local impacts of inundation and flooding hazards in the coastal zone of Tongatapu should be focused on adaptation, risk and hazard management.