Dissertations / Theses on the topic 'Coastal ponds'

Targeting marine diamondiferous deposits along the south-western Namibian coastline has involved the construction of seawall berms to advance the coastline and permit mining in previously subtidal areas. Large areas are mined out to bedrock level by the removal of overburden (sand and gravel), and after mining is complete, areas behind the seawalls fill with seawater, creating a series of coastal marine ponds that have the potential to function as saline wetlands corresponding to closed estuaries. The study site lies north of the Orange River mouth, within the Tsau//Khaeb (Sperrgebiet) National Park, to which the public has restricted access due to diamond mining in the area. Consequently, there is a focus on biodiversity conservation and the overall objective of this thesis was to determine the ecological value of the mining ponds by investigating whether they harbour sufficient biodiversity to qualify as a viable alternative ecological habitat, rather than restoring them to their original state as backfilled, revegetated dune areas. The study area, approximately 75 kilometres in length, was divided into north, middle and south sections, according to the age and status of mining activities, and I first assessed whether ponds in these three areas differed in their physical properties (Chapter 1). To determine whether the ponds serve as a useful ecological role worth preserving, I then investigated the diversity and amount of saltmarsh vegetation (Chapter 2), bird species (Chapter 3) and fish (Chapter 4) currently benefiting from these mining ponds. Ponds in the north are older and hypersaline whereas the south and middle ponds are younger and closely approach physical conditions in the sea. Diurnal fluctuations in oxygen concentration took place, but oxygen levels never dropped below 80% and were thus not limiting. After about 15 years, ponds developed salinities in excess of 80‰, which is likely to set limits on their ecological viability. Most ponds supported saltmarshes, but only a single species, Salicornia natalensis, grew around them. Its abundance was greatest around old ponds, but its health decreased with salinity. Wind emerged as a likely means of dispersal among ponds. The ponds supported a rich avifauna, averaging 11028 birds per count for all ponds combined; 36 species were recorded, ten being endemics, and five being listed in Namibia's Red Data Book. Numbers were highest for ponds that were being ‘dewatered' to remove water prior to mining, as this exposed a rich benthic epifaunal source of food. Blacknecked Grebe, Cape Cormorant, Greater and Lesser Flamingos, Kelp Gull and Common Tern were the most abundant birds. Salinity did not limit bird numbers or diversity, so the northern high-salinity ponds may continue to serve as bird habitat for periods of time much greater than the 15 years after which they become hypersaline. In comparison with nine other wetlands in the region, the ponds had great numbers, diversity, densities, and numbers of threatened species than about half of these wetlands, many of which are considered Important Bird Areas (IBAs). In many cases, they also supported more species that had numbers in excess of 1% of the southern African population than these IBAs. Only two species of fish commonly occurred in the ponds, the west coast steenbras Lithognathus auratus and the southern mullet Chelon richardsonii, although small numbers of two other marine species were recorded. The diversity of marine fish was thus low, even by the impoverished standards of west-coast estuaries. Unexpectedly, there were no significant differences between the ichthyofauna of ponds in the north, middle and south, nor was there any relationship between total fish numbers and salinity. Body condition of steenbras was lowest in the hypersaline north ponds, and their stomach contents contained a low diversity of food items there. The presence of recruits and the range of gonadal states suggested that both species bred in the ponds. Steenbras proved to be protandrous, with females dominating larger size classes. Growth rates of both species were faster in the ponds than in the adjacent sea, and mullet achieved substantially greater sizes in ponds. Thus, the ponds do serve as viable ecosystems, albeit with a limited range of saltmarsh and fish species, and support an impressively diverse avifauna. Their long-term viability will, however, become limited by rising salinity as their age increases.

A multi-proxy approach is utilized on mm- to cm-scale laminated sediment records in coastal salt ponds on St. John, U.S. Virgin Islands to characterize the sediments, identify their sources and depositional processes/events (heavy rainfall, tropical cyclones, tsunamis). Historical records are combined with high-resolution geochronology (short-lived radioisotopes, 210Pb, 137Cs, 7Be) and scanning elemental techniques (XRF and LA-ICP-MS) to link depositional events to how they are manifested in the sedimentary record. Volcanic rocks are the terrigenous sediment source and the sedimentary signature of terrigenous sediment in the geologic record consists of higher amounts of Al, Fe, Ti, Co, and Si, and is associated with terrigenous runoff due to rainfall events. A minimum threshold value of >2.0 mm per day (minimum to erode and transport terrigenous sediment downslope) of rainfall has been determined for the study area. The frequency of heavy rainfall events that exceed the threshold of >2.0 mm per day is significantly correlated to the amount of terrigenous sediment accumulation of the terrigenous indictor element Al measured by scanning LA-ICP-MS. There is a robust sedimentary record of terrigenous sediment runoff that is a function of the frequency of heavy rainfall events (exceed threshold). Variability in the sedimentary record reflects changes between periods of "wet" increased frequency of heavy rainfall events and "dry" decreased frequency of heavy rainfall events. Tropical cyclones and tsunamis can cause marine overwash into salt ponds leading to deposition of marine sediments. Elemental scans for Ca and Sr and overwash indicator elements are complicated by grain size effects of LA-ICP-MS techniques, as well the difficulty in differentiating between tropical cyclone overwash deposits and tsunami deposits. By defining the sedimentary signature for depositional events , geologic records can be interpreted to provide insight into the natural variability of these processes throughout geologic time for comparisons to the more recent anthropogenic time period. This study provides a framework that can be applied to other coastal environments on high-relief tropical islands, to compare local records, and provide information on regional processes controlling rainfall variability in tropical latitudes.

Floating treatment wetlands (FTWs) are an innovative best management practice that can enhance the performance of traditional retention ponds by increasing removal of the nutrients nitrogen (N) and phosphorous (P). FTWs consist of floating rafts on which wetland plants are planted, allowing the roots to be submerged below the water surface while the shoots remain above. A growing body of research has documented FTW performance with regard to urban runoff treatment, however evaluation of FTW effectiveness for treatment of agricultural runoff has received less attention. Due to high fertilization and irrigation rates, commercial nursery runoff contains much higher concentrations of N and P than runoff from urban areas. We conducted this study over two growing seasons (2015 and 2016) to assess the effectiveness of FTWs for use in commercial nursery retention ponds. In the first study we used two different nutrient concentrations, one to simulate nursery runoff (17.1 mg∙L-1 TN and 2.61 mg∙L-1 TP) and one to simulate concentrations that fall between urban and nursery runoff (5.22 mg∙L-1 TN and 0.52 mg∙L-1 TP). Four treatments were used: 1) Pontederia cordata planted in cups supported by a Beemat, 2) Juncus effusus planted in cups supported by a Beemat, 3) a Beemat with no plants, and 4) no treatment (open-water). Performance was evaluated based on a 7-day hydraulic retention time (HRT). Pontederia cordata removed between 90.3% and 92.4% of total phosphorus (TP) and 84.3% and 88.9% total nitrogen (TN), depending on initial loads. These reductions were significantly more than other treatments at both high and low nutrient loading rates. Juncus effusus performed better than the control treatments for TP removal at low nutrient concentrations, but did not perform any better than the control at higher nutrient loads. In the second study, conducted in 2016, we evaluated different plant species over two 8-week trials using simulated nursery runoff. We used five monoculture FTWs with the following species: Agrostis alba, Canna ×generalis, Carex stricta, Iris ensata, and Panicum virgatum. Additionally, two treatments were created from mixed species plantings and the final treatment consisted of an open water control mesocosm. Nutrient removal performance was evaluated over a 7-day HRT. P removal (phosphate-P) by FTW treatments ranged from 26.1% to 64.7% for trial 1 and 26.8% to 63.2% for trial 2. Trial 1 N removal (sum of ammonium-N, nitrate-N, and nitrite-N) efficiencies ranged from 38.9% to 82.4%, and trial 2 ranged from 12.9% to 59.6%. Panicum virgatum removed significantly more N and P than the control and any other FTW treatment in the second study. Both studies indicated, depending upon plant species, that FTWs can effectively remove nitrogen and phosphorous from urban and commercial nursery retention ponds.
Master of Science

Les stromatolites sont des structures organo-sédimentaires laminées, formées grâce à l’activité microbienne. Présents depuis plus de 3,5 milliards d’années, ils comptent parmi les plus anciennes traces de vie connues sur Terre et ils fournissent des informations précieuses sur la paléobiodiversité et les paléoenvironnements. De nombreuses études ont permis de développer une connaissance approfondie sur les stromatolites actuels, marins et lacustres, pouvant servir de référence pour l’interprétation des stromatolites anciens. Cependant, peu de travaux concernent des stromatolites d'environnements côtiers et lagunaires, qui, pourtant, enregistrent des caractéristiques chimiques, biologiques et minéralogiques significatives. Or, certains stromatolites anciens, comme ceux du Messinien (~6 Ma), abondamment présents dans l'ensemble du bassin méditerranéen, se sont possiblement formés dans un environnement côtier et/ou lagunaire soumis à des variations de salinité. L’objectif central de cette thèse est de comprendre comment l’environnement de formation (comprenant les paramètres abiotiques et biotiques) est enregistré dans des stromatolites actuels de Sardaigne, formés dans des étangs côtiers soumis à de fortes variations de salinité. Ces stromatolites sont principalement composés de calcite magnésienne. Une approche corrélative multi-échelles a révélé une diversité de phases minéralogiques comprenant divers carbonates, des phases argileuses authigènes, des phases sulfatées et un peu de détritisme. Nous avons observé des variations et une distribution spécifique des rapports Mg/Ca et Mn/Fe dans les calcites. Les calcites les plus enrichies en Mg et avec le rapport Mn/Fe le plus grand étaient systématiquement distribuées autour des restes microbiens. Nous avons supposé que l’activité microbienne exerçait un contrôle majeur sur la substitution du Mg dans la calcite, avec peut-être, une dynamique des populations microbiennes, influencée par les variations de salinité. De même, les variations du rapport Mn/Fe ont été interprétées comme étant des indicateurs des variations des conditions oxiques/anoxiques pouvant survenir localement dans le biofilm. En revanche, en lien avec le suivi géochimique des eaux des lagunes, il a semblé qu’à grande échelle, la distribution minéralogique était liée aux variations de salinité induites par l’évaporation dans les lagunes. En parallèle, l’évaluation de la distribution spatiale des signaux de fluorescence dans le visible a montré une préservation exceptionnelle de pigments photosynthétiques chlorophylle/phycocyanine dans des échantillons sardes ainsi qu'une une possible conservation de pigments photosynthétiques dégradés en lien avec l’activité microbienne dans les échantillons sardes et du Messinien
Stromatolites are laminated organo-sedimentary structures formed by microbial activity. Documented for more than 3.5 billion years, they are among the oldest known traces of life on Earth and they provide precious information on paleobiodiversity and paleoenvironments. Modern marine and lacustrine stromatolites are well-studied and they often use as references for the interpretation of ancient stromatolites. However, little is known about coastal and lagoonal stromatolites whereas they can record significant chemical, biological and mineralogical features. Yet, some ancient stromatolites, such as the Messinian ones (~6 Ma), abundantly present throughout the Mediterranean basin, are considered to have been formed in a coastal and/or lagoon environment subject to salinity variations. The main objective of this thesis is to understand how the formation environment (including abiotic and biotic factors) is recorded in modern sardinian stromatolites, formed in coastal ponds subjected to strong salinity variations. These stromatolites are mainly composed of magnesian calcite. A multi-scale correlative approach revealed a diversity of mineralogical phases including various carbonates, authigenic clays, sulfate phases, and some detritism. We observed variations and specific distribution of Mg/Ca and Mn/Fe ratios in the calcites. Calcites with the highest Mg enrichment and Mn/Fe ratio were systematically distributed around the microbial remains. We assumed that microbial activity had a major control on Mg substitution in calcite and that the dynamic of microbial populations, was influenced by the salinity variations. Similarly, Mn/Fe variations in calcite were interpreted as indicators of local oxic/anoxic variations in the biofilms. Thanks to the geochemical monitoring of lagoon waters, we proposed that, on a large scale, the mineralogical distribution was related to salinity variations induced by evaporation in lagoons. Meanwhile, the evaluation of the spatial distribution of visible fluorescence signals showed the exceptional preservation of chlorophyll/phycocyanin pigments in Sardinian samples. It also revealed the potential preservation of degraded photosynthetic pigments related to microbial activity in Sardinian and Messinian samples

Thesis (M.S.)--Joint Program in Oceanography (Massachusetts Institute of Technology, Dept. of Earth, Atmospheric, and Planetary Sciences; and the Woods Hole Oceanographic Institution), February 2001.
Includes bibliographical references (leaves 144-149).
A bi-weekly seasonal study was conducted in Ashumet Pond (Cape Cod, Massachusetts). The Redfield Ratio (106C:16N:1P) and alkaline phosphatase activity (APA) were utilized in tandem as nutrient deficiency indicators (NDIs) for phytoplankton. The study objective was to evaluate the limiting nutrient status of the pond throughout the growing season. The development of a high throughput method for fluorometrically measuring APA allowed for a large quantity of pond-water samples to be analyzed. The new method utilized a cytofluor, a fluorescence multi-well plate reader, which increased sample throughput by 75% compared to a standard filter fluorometer method. The detection limit, capability to measure APA at different time intervals, and performance at sea were tested. APA measurements made using the cytofluor were comparable to those made using a standard filter fluorometer, thus indicating that the cytofluor is a suitable and preferred replacement to the fluorometer for APA measurements. The presence of alkaline phosphatase, an inducible phospho-hydrolytic enzyme, is commonly used as an NDI diagnostic for phosphate limitation. A nutrient enrichment incubation re-affirmed the use of APA as a robust indicator of phosphate limitation in phytoplankton. APA data indicate that the system experienced episodic periods of phosphate-deficiency, implying that the limiting nutrient regime was not static, but was changeable throughout the growing season. Seasonal trends in dissolved N:P and particulate C:P ratios often contradict the APA results, however, suggesting that the Redfield Ratio is an unreliable indicator of the overall nutrient limitation regime of the pond. The observed discrepancies between C:N:P and APA can be reconciled by taking into account seasonal changes in species composition, which played an important role in driving seasonal APA trends.
by Christie Lynn Haupert.
M.S.

Urban and agricultural runoff is the principal contributor to non-point source (NPS) pollution and subsequent impairments of streams, rivers, lakes, and estuaries. Urban and agricultural runoff is a major source of sediment, nitrogen (N) and phosphorus (P) loading to receiving waters. Coastal waters in the southeastern U.S. are vulnerable to human impacts due to the proximity to urban an agricultural land uses, and hydrologic connection of the Coastal Plain to receiving waters. To mitigate the impacts of urban and agricultural runoff, a variety of stormwater control measures (SCMs) are implemented. Despite the importance of the Coastal Plain on water quality and quantity, few studies are available that focus on prediction of nutrient and sediment runoff loads from Coastal Plain watersheds. The overall goals of my dissertation are to assess the effect of urban and agricultural watershed on coastal waters through monitoring and modeling, and to characterize treatment performance of SCMs. These goals are addressed in four independent studies. First, we developed the Storm Water Management Model (SWMM) and the Hydrologic Simulation Program-Fortran (HSPF) models for an urbanized watershed to compared the ability of these two models at simulating streamflow, peak flow, and baseflow. Three separate monitoring and modeling programs were conducted on: 1) six urban land uses (i.e. commercial, industrial, low density residential, high density residential, transportation, and open space); 2) container nursey; and 3) a Coastal Plain retention pond. This study provides methods for estimating watershed pollutant loads. This is a key missing link in implementing watershed improvement strategies and selecting the most appropriate urban BMPs at the local scale. Results of these projects will help urban planners, urban decision makers and ecological experts for long-term sustainable management of urbanized and agricultural watersheds.
Doctor of Philosophy
Urban and agricultural runoff is a major source of sediment, nitrogen (N) and phosphorus (P) loading to receiving waters. When in excess, these pollutants degrade water quality and threaten aquatic ecosystems. Coastal waters in the southeastern U.S. are vulnerable to human impacts due to the proximity to urban an agricultural landuse. To mitigate the impacts of urban and agricultural runoff, a variety of stormwater control measures (SCMs) are implemented. The overall goals of my dissertation are to assess the effect of urban and agricultural watershed on coastal waters through monitoring and modeling, and to characterize treatment performance of SCMs. These goals are addressed in four independent studies. First, we developed two watershed models the Storm Water Management Model (SWMM) and the Hydrologic Simulation Program-Fortran (HSPF) to simulate streamflow, peak flow, and baseflow within an urbanized watershed. Three separate monitoring programs were conducted on: (1) urban land uses (i.e. commercial, industrial, low density residential, high density residential, transportation, and open space); (2) container nursey; and (3) a Coastal Plain retention pond. These studies provided methods for estimating watershed pollutant loads. Results of these projects will help urban planners and ecological experts for long-term sustainable management of urbanized and agricultural watersheds.

Entre le début du XVIIIe siècle et la fin du Second Empire, la côte continentale du Pertuis Breton connaît une évolution significative. Elle est constituée de trois paysages géomorphologiques singuliers, dynamiques et corrélés : un territoire marécageux, une zone dunaire et une côte à falaises. Ces milieux subissent des transformations naturelles lentes à l’origine de la constitution des flèches sableuses d’Arcay et de l’Aiguillon qui forment un grand cordon dunaire. Celui-ci est alimenté par un transport considérable des sables de l’ouest vers l’est par dérive littorale. Ces mouvements de sédiments sont soumis à l’influence d’agents hydrodynamiques. La remontée des eaux de l’océan entraîne le colmatage progressif du golfe des Pictons par des apports de sédiments d’origine fluvio-marine. Ce processus est à l’origine de la formation de l’anse de l’Aiguillon et du Marais poitevin. Ces milieux subissent également des transformations naturelles brutales dues à des phénomènes climatiques extrêmes. Cette étude met aussi en lumière la part de l’influence humaine dans l’évolution et la modification de leur trait de côte. Les aménagements sont particulièrement visibles dans le Marais poitevin. Entre le Moyen Âge et le XIXe siècle, ce territoire est l’enjeu d’une grande transformation qui modifie largement son écosystème. Cette zone humide est drainée par l’instauration de canaux, de digues et d’écluses. Grâce aux dessèchements réalisés par les sociétés des marais, l’agriculture et l’élevage connaissent un essor considérable et remplacent progressivement ces terres inondables réputées insalubres. Les marais connaissent alors un afflux de population. L'Etat est présent sur ce littoral par l’intermédiaire des Amirautés sous l’Ancien Régime ou de l’administration des Ponts et Chaussées au XIXe siècle
Between the beginning of the 18th century and the end of the Second Empire, the continental coast of the Pertuis Breton experienced a significant evolution. It is composed of three singular, dynamic and correlated geomorphological landscapes: a marshy area, a dune zone and a cliff coast. These environments underwent slow natural transformations which led to the creation of the sandy spits of Arcay and Aiguillon which form a large dune belt. The latter is fed by a considerable transport of sand from west to east by littoral drift. These sediment movements are subject to the influence of hydrodynamic agents. The rise in oceanic waters leads to the progressive clogging of the Gulf of the Pictons with sediment of fluvio marine origin. This process is at the origin of the formation of the Aiguillon Cove and the Poitevin Marsh. These environments also go through brutal natural transformations due to extreme climatic phenomena. This study also highlights the role of human influence in the evolution and modification of their coastline. Developments are particularly visible in the Marais Poitevin. Between the Middle Ages and the 19th century, this territory was the focus of a major transformation that greatly modified its ecosystem. This wetland was drained by the creation of canals, dykes and locks. Thanks to the draining carried out by the marsh companies, agriculture and livestock farming flourished and gradually replaced the flooded lands, which were considered unsanitary. The marshes then experienced an influx of people. The State is present on this coastline through the Admiralty under the Ancien Régime or the administration of the Ponts et Chaussées in the 19th century

Coastal plain ponds are an understudied and threatened wetland ecosystem with many unique environmental attributes. Research in these ponds can investigate species-environment relationships, while simultaneously providing ecosystem-specific information crucial to their continued conservation and management. This dissertation explores patterns in coastal plain pond vegetation composition and species-environment relationships across space, through time, and in the seed bank and standing vegetation.

In a two-year field study at 18 coastal plain ponds across the island of Martha's Vineyard, Massachusetts, I investigated species-environment relationships within and among ponds. I identified vegetation species presences and abundances within 1 m2 quadrats, which ran continuously along transects established perpendicular to the water's edge. Species data were analyzed against local and landscape-scale environmental data. I also conducted a one-year seed bank study in which sediments from four coastal plain ponds were incubated in growth chambers and composition was compared to the standing vegetation. One hundred and thirty-four plant species were identified during vegetation sampling and 38 species were identified from incubated sediments.

I found significant compositional change across space in response to environmental gradients, with patterns in species composition occurring at both local and landscape scales. Elevation was the only local factor strongly correlated with species composition. Significant landscape-scale environmental factors included surficial geology and pond water salinity. Species composition was significantly correlated with hydrologic regime in 2005 but not in 2006. Overall patterns in vegetation species composition and abundance were more closely related to landscape-scale environmental variables than to local environmental variables.

I also found that coastal plain ponds undergo significant compositional change from one year to the next. Interannual variability disproportionately affected certain ponds and quadrats more than others, highlighting patterns in the relationships between compositional change and environmental attributes. Specifically, ephemeral ponds, ponds located on the moraine, ponds with high specific conductance values, and quadrats located closer to the waterline exhibited greater compositional change from 2005 to 2006 than permanent ponds, ponds located on the outwash plain, ponds with low specific conductance values, and quadrats located further from the waterline.

Finally, I found that coastal plain ponds exhibit a low degree of similarity between composition in sediments and standing vegetation. More species were identified in the standing vegetation than in the seed bank, and in most cases average species richness per quadrat was higher in the standing vegetation than in the seed bank. Seed bank and standing vegetation samples from ponds with different surficial geology were compositionally distinct. Seed bank samples from permanent and ephemeral ponds were compositionally distinct whereas standing vegetation samples were not.

Dissertation

碩士
南華大學
環境管理研究所
97
The risk associated with intake of arsenic（As）, zinc（Zn）and copper（Cu）of cultured milkfish（Chanos chanos）using groundwater from southwest coast in Taiwan were studied, based on the questionnaire and the risk assessment models. The resulting values of As（63.9 ± 2.51 mg L-1）and Cu（77.1 ± 3.69 mg L-1）in pond water show that the concentrations of these two pollutants are higher than the standards in Taiwan（As: 50 mg L-1 and Cu: 30 mg L-1, respectively）, while the Zn concentration（10.9 ± 4.72 mg L-1）is lower than the standard（500 mg L-1）. The bioconcentration factor（BCF）values of As, Zn and Cu in milkfish（12.51 ± 4.95, 4479.68 ± 1399.66 and 30.50 ± 12.76, respectively）show that the milkfish can accumulate these pollutants from the ambient water. The target cancer risk（TR）of consuming milkfish is 1.05×10-3 ± 9.91×10-4, which is higher than the acceptable risk 1×10-6. Among the three pollutants, only the value of the target hazard quotient（THQ）of As exceeds the safe value 1 for non-carcinogenic risk. The hazard index（HI）5.91 ± 5.38 is 5 times higher than the standard, mainly contributed by the THQ value 5.45 ± 5.14 of As. The acceptable consumption of the milkfish is 0.32 ± 0.17 g d-1, which is lower than the actual milkfish consumption 179.32 ± 233.51 g d-1. Therefore, the consumption of cultured milkfish using groundwater may cause carcinogenic and non-carcinogenic risks. The risk-based concentration（RBCf）of As in milkfish is 7.19×10-4 ± 2.62×10-4 mg g-1, which is lower than that in milkfish we measured in pond. Arsenic concentrations（63.9 ± 2.51 mg L-1）in pond water are higher than the risk-based concentration（RBCw）for As（0.08 ± 0.03 mg g-1）. Ingestion of these contaminated milkfish could result in exposure of As, Zn and Cu in inhabitants and lead to adverse health effects caused by As.

Dissertação de Mestrado, Geologia do Ambiente e Sociedade, 15 de Fevereiro de 2016, Universidade dos Açores.
Fajãs detríticas costeiras com sistemas lagunares – como as Fajãs da Caldeira de Santo Cristo e dos Cubres na Ilha de São Jorge – constituem locais de elevada riqueza geológica, biológica e paisagística, tendo mesmo se tornado um ícone paisagístico do Arquipélago dos Açores. Muito embora seja do conhecimento geral que a génese de fajãs detríticas costeiras está intrinsecamente ligada à evolução das altas arribas litorais típicas de ilhas vulcânicas, e aos processos de movimentos de massa associados a esta evolução, pouco se conhece acerca dos processos que concorrem para a génese de fajãs detríticas costeiras que exibem sistemas lagunares. Em particular, dúvidas ainda subsistem acerca da possibilidade dessas fajãs serem um resultado directo e fortuito do deslizamento que lhes deu origem, ou, por oposição, serem resultado de um retrabalhamento marinho (por ondas e correntes) após a sua implantação. Um acontecimento recente, no entanto, promete revolucionar o nosso conhecimento sobre o assunto: um deslizamento ocorrido na Ilha do Corvo durante o temporal de 30 de Outubro de 2012, e o seu desenvolvimento posterior, constitui um análogo exemplar para a génese destas morfologias. O objectivo central desta tese de mestrado é precisamente documentar a evolução desta fajã, com o intuito de avançar o nosso conhecimento sobre as origens das fajãs detríticas costeiras com sistemas lagunares, e sobre os processos que concorrem para a sua formação. [...].
ABSTRACT: Coastal talus-platforms (fajãs) with pond systems - like Fajã da Caldeira de Santo Cristo and Fajã dos Cubres in São Jorge Island – constitute features of high geological, biological, and landscape value, even becoming one of the most iconic landscapes of the Azores Islands. Whilst the origin of fajãs is firmly established as being the product of landslides that develop along the high coastal cliffs that rim reefless volcanic islands, little is still known about the processes that interplay to shape the fajãs that exhibit a pond system. In particular, doubts still remain on whether fajãs featuring a pond system are a direct fortuitous product of mass wasting, or conversely result from marine reworking (by waves and currents) after emplacement. An exciting recent event, however, promises to revolutionize our knowledge of the subject: a landslide occurred on the Island of Corvo, during the storm of October 30th 2012, and its posterior evolution constitutes a perfect analogue for the generation of these iconic landscapes. The central aim of this MSc thesis is precisely to document the evolution of this fajã, in order to gain a better understanding on the origins of coastal talus platforms featuring a pond system and on the processes that concur to their formation. [...].

碩士
東海大學
環境科學與工程學系
97
Abstract The extensive tidal flats of Han-pao and Wangkung are the main feeding sites for shorebirds at low tide. But they are flooded at spring high-tide, thus the shorebirds must search for inland roosting sites. The most common roosting sites they choose at Han-pao and Wang-Kung are the bunds of fish pond. In order to understand what kinds of environmental factors affect the choice of these roosting shorebirds, I recorded the differences in micro-habitat factors of the bunds of fish ponds used by the wintering Kentish Plovers and Dunlins which were the most common species in winter during December 2007 to February 2009. I also observed the disturbance factors. My result showed that the environmental factors of bund affect shorebird roosting including bund length, bund width and vegetation coverage. Shorebirds preferred the longer bund length, narrower bund width and lower vegetation coverage. About disturbance, I found that when the wind speed was high, shorebirds used leeward side of bunds to avoid the wind. My result showed that the presence of raptors and dogs caused shorebirds to fly, but human and vehicle disturbance were not significant. Key words: shorebird、fish pond、bund、roost、micro-habitat preference、disturbance

This work re-examines samples of modern microbialites collected in the 1980s from Lakes Clifton and Preston, two of the Yalgorup Lakes in southwest Western Australia. Lake Clifton contains the first convincing modern examples of thrombolites to have been recognized. It was known that aragonite mineralisation took place in these structures within near-surface biofilms. New research reveals that stevensite, a Mg-rich trioctahedral smectite, is the principal primary phase that establishes the initial structural rigidity of Lake Clifton thrombolites. Aragonite microcrystals then grow within the stevensite matrix. In adjacent Lake Preston, lithified, centimetre-scale, coniform structures occur that are similar to pinnacle-like microbial mats that grow intermittently in a small pond adjacent to the lake. Microstructures within the lithified cones confirm their microbial origin, but they have undergone four phases of mineralization; an amorphous Mg silicate phase (of smectite-like composition); some areas of Mg silicate were then partially transformed into authigenic serpentine (chrysotile and/or lizardite); aggregates of aragonite microcrystals then overprinted much of the fabric; and finally high-magnesium calcite grew as void fills and rims, as well as overprinting some of the remaining areas of the Mg silicate phase. It is concluded that syngenetic and early diagenetic carbonate mineralisation of microbialites may effectively obscure all traces of the original microbial communities, leaving only faint evidence for their organo-sedimentary origin. Secondary carbonate mineralisation of microbialites may thus eliminate the evidence of primary organomineralisation. Many published examples of apparently abiogenic but microbialite-like carbonates should be re-examined for traces of early silicate mineralisation. The discovery of microbial permineralisation of modern microbialites by Mg silicates in Lakes Clifton and Preston raises the possibility that phyllosilicates could have contributed to the early structural rigidity of some Proterozoic Stromatolites such as Conophyton. Reexamination of the literature on Conophyton tends supports this hypothesis. Finally, the significance of this research is considered in relation to ; clarifying the role of Mg silicates in microbialite organomineralisation; examining the evidence that apparently abiotic crystalline carbonate may be of secondary origin; understanding the nature of the supposed “microbialites” in Cretaceous pre-salt sequences of the proto-Atlantic rift; assessing the continuing relevance of the “microbialite” concept; and clarifying evidence for the recognition of the earliest signs of life on Earth.