Dissertations / Theses on the topic 'Estuarine wetland'

Floodgates were constructed in 1971 on the main creek draining Hexham Swamp, a large wetland on the floodplain of the lower Hunter River, New South Wales. Substantial changes in vegetation have occurred in Hexham Swamp subsequent to the construction of the floodgates. Previous areas of mangroves and saltmarsh have been reduced (180ha to 11ha, and 681ha to 58ha, respectively), and Phragmites australis has expanded (170ha to 1005ha). Much of the mangrove loss (ca. 130ha) was a result of clearing, and the remainder has gradually died off. The factors contributing to the dieback are likely to be a combination of drying of the soil, root competition and, at times, waterlogging. Field sampling as well as microcosm and reciprocal transplant experiments involving key species, Sarcocornia quinqueflora, Sporobolus virginicus, Paspalum vaginatum and Phragmites australis, suggest that a reduction in soil salinity has been an important factor in initiating successional change from saltmarsh to Phragmites reedswamp. The data also suggest that increased waterlogging has been an important factor in initiating vegetation change. This apparently paradoxical result (floodgates and associated drainage generally result in drying of wetlands) is likely to have resulted from occlusion of drainage lines (by sediment and reeds) and is, therefore, likely to be a condition that developed gradually. That is, the initial effect of the floodgates is expected to have been a drying of the swamp, followed over time by an increasing wetness. An examination of vegetation changes after removal of cattle from part of Hexham Swamp, suggests that grazing had little effect on species composition of vegetation or rate of expansion of Phragmites australis. However, grazing does affect vegetation structure (height and density), possibly favours some coloniser species (e.g. Sarcocornia quinqueflora) in particular environmental conditions, and possibly inhibits establishment of Phragmites australis.

Thesis (M.S. in environmental science)--Washington State University, December 2009.
Title from PDF title page (viewed on Feb. 18, 2010). "School of Earth and Environmental Science." Includes bibliographical references (p. 24-29).

As disturbance frequencies, intensities, and types have changed and continue to change in response to changing climate and land-use patterns, coastal communities undergo shifts in both species composition and dominant vegetation type. Over the past 100 years, fire suppression throughout the Northern Gulf of Mexico coast has resulted in shifts towards woody species dominance at the expense of marsh cover. Over the next 100 years, sea levels will rise and tropical storm activity is projected to increase; resultant changes in salinity could reduce cover of salt-intolerant fresh marsh species. Together, the effects of fire suppression upslope and rising salinities downslope could "squeeze" fresh marsh species, reducing cover and potentially threatening persistence. To mitigate the effects of fire suppression, the use of prescribed fire as a management tool to mimic historic conditions is becoming increasingly widespread and will likely gain further popularity during the 21st century. Ecological shifts that will result from changing disturbance regimes are unknown. It was hypothesized that two recent hurricanes, Ivan and Katrina in 2004 and 2005, respectively, and a prescribed fire, in 2010, differentially affected species along the estuarine gradient and drove overall shifts away from woody dominance. Overall community composition did not change significantly in the intermediate and fresh marsh zones. However, significant changes occurred in the salt and brackish marshes and in the woody-dominated fresh marsh-scrub ecotone zones. Relative to 2004, woody species abundance decreased significantly in all zones in 2006, following Hurricanes Ivan and Katrina, and 2012, following the hurricanes and fire, though woody species regeneration in the marsh-scrub ecotone had begun to occur by 2012. It is hypothesized that interacting changes in fire and tropical storm regimes could release upslope areas from coastal squeezing.

The purpose of this study was to identify and quantify estuarine and marine wetland and shore changes circa Galveston Bay Estuary (GBE) from 1995 to 2002 by using aerial photography and GIS mapping techniques. Aerial photographs in digital format were acquired from Texas Natural Resource Information System (TNRIS) and the Houston Galveston Area Council (HGAC); these photographs were selected because the images were taken at the time period desired, existed in digital formats at resolutions of 1 m or greater, and were in coordinate systems that were already in or could be properly aligned and georeferenced. Maps for each of thirty quadrangles that include estuarine and/or marine habitats around the GBE were created, depicting wetlands and shorelines for the years 1995 and 2002 as well as changes between the two time periods. Polygons representing different habitats in 1995 were drawn while working at a scale of 1:4,000 or greater. Maps of habitats in 2002 and maps showing changes from 1995 to 2002 were produced by modifying individual 1995 polygons to document boundary shifts or habitat changes from 1995 to 2002. All resulting maps were constructed at 1:24,000 scale in UTM NAD 83 coordinate system to match USGS quad maps. Areas of each habitat in 1995 and 2002 and changes between the two years were calculated in acres and comparisons were made. There were four objectives developed to be examined by the creation of the new set of maps for GBE. They were to determine habitat changes during the time period in question, effectiveness of mapping technique, where differences in change occurred, and what type (i.e. erosion, development, accretion, etc.) of change occurred. My analyses of these maps indicated that there were 117,670 acres of estuarine wetlands and 21,983 acres of unconsolidated estuarine and marine shores present in 1995. In 2002, these values changed to 116,534 acres of estuarine wetlands and 21,630 acres of estuarine and marine shores. The rate of wetland loss was estimated as 162 acres per year or 0.1% of all wetlands annually from 1995 to 2002. This rate has slowed from the previous rate of 405 acres per year or 0.4% in 1979 and remained the same as the 161 acres per year or 0.1% reported in 1993 for the GBE. Further, the results of my analyses indicated that losses from direct human influences (e.g. development, dredging, and filling) were less than losses associated with natural processes like erosion and subsidence.

Three separate but related aspects of sediment allocation in a river/estuarine system were examined. The main purpose was to compare sediment budgets for a series of eleven nested sub-watersheds as a function of watershed size, ranging from 65 to 6900 km2. The approach quantified six budget components: upland erosion; stream bank erosion; colluvial storage; wetland storage; stream channel erosion and storage; and sediment flux at the outlets. Three budgets were developed for each sub-watershed to examine the relative proportions of budget components, budget sensitivity (the influence of individual components on the overall budget), and the uncertainty of budget components. The study area was the rural, forested, low relief York River watershed in southeastern Virginia. The relative proportions of budget components do not change with sub-watershed size. Budgets are more influenced by the tributary system than by the sub-watershed size. The budget is sensitive to most components because they are large in size and are highly variable. The uncertainties of budget components are proportional to the magnitude of the best estimates. Management efforts should focus on locally-derived sediment to improve water quality because little sediment from the upper parts of the watershed reaches the estuary. Sediment loads were needed in the sediment budgets for three estuarine sampling stations. The loads were estimated by separating the gravitational circulation, tidal pumping, and river input components of long-term total suspended solids data. The load for the station closest to the river mouth was somewhat larger than literature values. The contribution to the estuary of the two tributary stations was previously unknown. Tidal pumping, rather than gravitational circulation, is the dominant process moving suspended sediment up the estuary. The potential supply and storage of sediment in wetlands at the watershed level was examined by quantifying the areal extent of wetland type and location in the watershed, and surrounding land use, slope, and soil type. Results showed that these landscape characteristics are unevenly distributed within the York River watershed and its subdivisions. The differences in landscape characteristics between subdivisions suggest that wetland performance and its impact on water quality may vary within a watershed. Separate management approaches may be needed to accommodate these differences.

In the restoration of tidal wetland ecosystems, potential drivers of plant community development range from biotic controls (e.g. plant competition, seed dispersal) to abiotic controls (e.g. tidal flooding, salinity levels). How these controls influence the success of tidal wetland restoration are only partly understood, but have important implications for wetland habitat recovery. Specifically, the extent to which the existing native and non-native seed banks in tidally reconnected wetlands interact with these controls is not clear, yet the potential success of passive restoration methods depends upon this understanding. For a 54-year chronosequence of eleven tidal wetland restoration sites in the Lower Columbia River of western Oregon, USA, it was hypothesized that native plant species and soil properties would show trends approaching reference levels within 3 to 20 years post-restoration and that lower elevation wetland areas within restored sites would exhibit a greater native species abundance and similarity to reference sites, compared with restored high elevation wetland areas. Results indicated that plant species richness, soil organic matter, bulk density, pH, and salinity conditions among the restoration sites reached reference wetland ranges within 3-6 years post-tidal reconnection. The mid-low marsh elevation zones (<2.5 m) recovered native plant cover within 3-6 years post-tidal reconnection, while high marsh elevation zones (>2.5 m) remained dominated by nonnative species Phalaris arundinacea and Juncus effusus subsp. effusus. To investigate the mechanisms driving these non-native plant invasions, it was ii hypothesized that native and non-native wetland plant community distributions would be reflective both of their abundance in the seed bank and of their germination tolerance to wetland tidal flooding and salinity conditions. Using a factorial study design of three tidal conditions by three salinity levels, these hypotheses were tested in the greenhouse. Overall, non-native seeds were found to significantly outnumber native seeds in both seed banks. In the greenhouse, P. arundinacea and J. effusus were found to germinate more readily out of the seed bank under freshwater high-marsh flooding (1 hour a day) treatments as compared to oligohaline (3 ppt) mid-low marsh flooding (3-6 hours twice a day) treatments and to brackish salinity (10 ppt) treatments. Dominant native wetland species, Carex lyngbyei and Schoenoplectus lacustris, germination were not found to vary significantly among the treatments (p > 0.10). These results indicate that the salinity and flooding gradients within these restored marshes suppress germination of the non-native species in the low-mid marsh but not in the high marsh, where they are likely able to outcompete the native species due to their dominance in the seed bank. The implications of these results for passive tidal wetland restoration efforts are that both seed bank composition and species-specific tolerances to restored tidal flooding and salinity gradients are key mechanisms driving native and nonnative plant community development and resilience.

The Northern Gulf of Mexico and coastal Louisiana are experiencing accelerated relative sea level rise rates; therefore, the region is ideal for modeling the global affects of sea level rise (SLR) on estuarine dynamics in a transgressive barrier island setting. The field methods and numerical modeling in this study show that as barrier islands are converted to inner shoals, tidal exchange increases between the estuary and coastal ocean. If marshes are unable to accrete at a pace comparable to SLR, wetlands will deteriorate and the tidal exchange and tidal prism will further increase. Secondary to hurricanes, winter storms are a primary driver in coastal morphology in this region, and this study shows that wind direction and magnitude, as well as atmospheric pressure change greatly affect estuarine exchange. Significant wetland loss and winter storm events produce changes in local and regional circulation patterns, thereby affecting the hydrodynamic exchange and resulting transport.

Hydrokinetic tidal power is a novel and emergent technology undergoing continuous advancement with much of the progress focused on large utility scale projects. This resource is potentially underutilized because much of the coastal United States, despite having substantial tidal currents, do not have the deep and wide environments required by most of the developing turbine technology. This dissertation includes a detailed characterization of the tidal hydrodynamics for Rose Dhu Island, Georgia used for a tidal energy resource assessment as well as a general feasibility study for tidal estuaries with extensive wetlands. For predictions and evaluation of the estuarine hydrodynamics, data from an existing numerical model of the estuary encompassing the island is utilized. Field measurements in close proximity to the island are used to calibrate the model as well as characterize local hydrodynamic features. After the model calibration, the simulation data is used to evaluate the hydrodynamics. Wetland dominated estuaries commonly have a high degree of non-linear distortion which govern the relative durations and strengths of the tidal stages and thus the overall hydrodynamics and incoming hydrokinetic energy. The Ogeechee Estuary is characterized as ebb dominant with peak ebb and flood volume fluxes near high tide as a result of the increased storage capacity of the wetlands. Lowering the average wetland elevation in the model decreased ebb dominance and quickened the transition from flood to ebb tide. Increased domain friction in the model removed energy from the system and reduced ebb dominance. Enhanced model marsh friction reduced lateral flooding of the wetlands as well as ebb dominance. Localized measurements surrounding the island are analyzed to determine a location near the southwest coast of the island as a hydrokinetic energy hotspot. A kinematic and dynamic analysis is performed using channel transect measurements to identify key physical processes behind the hotspot formation. The hotspot forms due to sub-critical flow acceleration over a singular bump in the topography. High streamwise momentum is further concentrated at the hotspot due to secondary circulation cells across the channel. Flood tide circulation is characterized by two co-rotating cells induced by channel curvature and delineated by the bump. Ebb circulation consists of two counter-rotating cells from flow confluence of two upstream channels. Once the hydrodynamics are understood, the theoretical and technical resource assessment of the island is completed. A sensitivity analysis of hydrokinetic energy and tidal distortion is performed on synthetic data. For a principle constituent and its first harmonic, distortion greatly changes as does the distribution of velocities and energy as the relative phase varies. While the theoretical energy remains consistent, the technical energy can greatly vary. This effect is reduced with the addition semi-lunar variation. Using a simplified analytical method, the maximum average channel power is estimated as 8.80 MW. For the hotspot it is estimated that there is 30.3 MWh available to capture yearly with an average power of 3.46 kW for a turbine with an area of 10 square meters. For the same turbine area with conservative efficiencies, the hotspot could provide a yearly technical energy of 10.9 MWh with an average power of 1.25kW for the island. Due to the complex localized hydrodynamics, both the theoretical and technical resource varies greatly across and along the channel. These considerations are more pertinent when performing a hydrokinetic energy resource assessment in a marsh estuary than for large scale bay-ocean exchange environments, the present industry focus.

This study investigated the response of the macrophytes in St Lucia Estuary, northern KwaZulu-Natal to drought. The present distribution of vegetation (2010 / 2011) was mapped and changes over time recorded from past aerial photographs. The changes in macrophyte cover in response to environmental factors (sediment and groundwater characteristics) was measured along four transects in 2010 and compared with results from previous years, in 2005 and 2006. In the current study, 1960 images were digitized to illustrate macrophyte distribution and cover of the Narrows, Makakatana and the Eastern Shores during a low rainfall period which started in 1958. The 2001 images were digitized to illustrate vegetation distribution and cover of the same area prior to the current drought which started in June/ July 2002. The 2008 images were digitized to illustrate vegetation distribution and cover of estuarine vegetation within the floodplain during the drought (after 6 years). The sites were visited in June 2011 for verification of the distribution and boundaries of each macrophyte habitat. The area covered by the water column varied over time. In 1960 during a low rainfall period the water was 32705 ha, 33320 ha in 2001 and reduced to 30443 ha in 2008. The area cover of inundated and dry reeds fluctuated with the water level. Under high water levels, low-lying areas such as Fanies Island and Selley‟s Lake were flooded and under low water levels, intertidal sand and mudflats were exposed and colonised by succulent salt marsh (Sarcocornia spp. and Salicornia meyeriana). Similar conditions were observed at Makakatana. Mangroves were observed from the mouth to the Forks. Avicennia marina was the dominant mangrove species and primary colonizer of dredge spoil. The area cover of mangroves in the vicinity of the mouth fluctuated as a result of fluctuating water levels, dredging operations, excavation of the Back Channel and Cyclone Gamede which killed intertidal vegetation. Between 2001 and 2008, mangrove expansion was faster in the Mfolozi Swamps area (± 1.4 ha yr -1) compared to the Narrows (± 0.4 ha yr -1). Long term monitoring transects were set up in 2005, at Makakatana, Charters Creek, Catalina Bay and at Listers Point to document changes in sediment conditions and vegetation cover. These were sampled in July 2005, October 2005, February 2006 and May 2010. Silt was the dominant particle size at Catalina Bay, Charters Creek and Makakatana. At Makakatana, average ground water salinity was 17.2 ± 6.6 ppt, 4.1± 4.9 ppt at Catalina Bay and 32.9 ± 19.3 ppt at Charters Creek. Drought resulted in the accumulation of salt on the surface sediment layer at Listers Point and Charters Creek due to low rainfall. Listers Point, the site with the lowest freshwater input and habitat diversity had the lowest macrophyte species richness with only three species. The dominant species at this site were Sporobolus virginicus and Chenopodium album L. which are highly salt tolerant species. Catalina Bay had the highest species richness (18 to 27); as a result of freshwater input via groundwater seepage from the sand dune aquifers on the Eastern Shores. Along the Eastern Shores, vegetation was dominated by species of Cyperaceae, Juncaceae and Juncaginaceae. Fluctuations in groundwater depth were observed at all sites, Listers Point groundwater depth in February 2006 was 80 cm and the ground water level was not reached during the May 2010 field trip. During the May 2010 field trip, the water column salinity of the St Lucia system was highly variable, Makakatana had the lowest water column salinity of 7.1 ppt, 42.1 ppt at Catalina Bay, 44 ppt at Charters Creek and Listers Point had the highest water column salinity of 95 ppt. An assessment of the changes in macrophyte cover along the transects showed that cover fluctuated in response to rainfall, water level and drought. At Listers Point, there was a continuous decline in the abundance of Sporobolus virginicus over time which was sparsely distributed in the first 40 m of the transect. Sarcocornia natalensis, a succulent and obligate halophyte, was recorded, in areas with high sediment conductivity. In May 2010, bare ground increased to an average percentage cover of 96.5% and was covered with dead organic matter and a salt crust at Listers Point. At Makakatana, there was a significant decrease in bare ground from July 2005 to May 2010 (H = 24.58, N = 197, p<0.001) as bare areas were colonized by salt marsh. Multivariate analysis showed that the abundance of Sporobolus virginicus was positively influenced by sediment moisture content and Paspalum vaginatum abundance was strongly influenced by the water column salinity. At Catalina Bay, low sediment conductivity at the groundwater seepage area resulted in terrestrial vegetation encroaching on estuarine vegetation. Sarcocornia natalensis became more abundant towards the water column. During the period of study, species richness at St Lucia ranged from 2 (Listers Point, May 2010) to 27 (Catalina Bay, February 2006). Salinity and water level fluctuation have a significant impact on the distribution of macrophytes at St Lucia during the drought. In saline areas salt marsh plants have colonized exposed shorelines and along the Eastern Shores groundwater seepage has increased macrophyte species richness. Low water levels have resulted in the exposure and desiccation of submerged macrophytes, which are replaced by macroalgae.

Intertidal wetland habitats in southeastern Australia have changed significantly during the past sixty years. Mangrove habitats have expanded both seawards and landwards, the latter being at the expense of saltmarsh habitats. This relatively common phenomenon is generally suggested to be an outcome of sea-level rise. Several factors potentially responsible for this change are examined, including changes in mean sealevel during the past 50 to 100 years, changes in climate, population growth, catchment landuse, and estuary type. A protocol for mapping estuarine habitats was developed and implemented, incorporating the application of geographic information systems. Spatial and temporal coastal wetland habitat changes at nine sites along the New South Wales coast are illustrated. These habitat dynamics were shown to not correlate between sites. The results demonstrate that sea-level rise in this region cannot solely account for the extent of change during the past sixty years. With the exception of one site (Careel Bay), there have been no correlations between contemporary mean sea-level rise and mangrove incursion of the saltmarsh habitats at the study sites, or with rainfall patterns, at the scale of observation in this study, which was largely decadal. The only correlations determined during this study have been between population growth and coastal wetland habitat dynamics in some sites. In spite of saltmarsh habitat loss being a regional phenomenon, local factors appear to have a profound bearing on the rates of change. Neither contemporary mean sea-level rise, rainfall patterns, estuary type, catchment landuse, catchment natural cover nor population pressure can account solely for the patterns in the spatial and temporal dynamics of the coastal wetlands of New South Wales. It seems apparent that regional factors create preconditions favourable for mangrove incursion, but that localised conditions have been responsible for the extent of these incursions from site to site. That is, despite higher sea-level and greater rainfall, the extent of change has been determined by the unique characteristics of each site. The results have important implications for current estuary management practices in the state of New South Wales. The lack of spatial and temporal trends in coastal wetland habitat dynamics point to the need for management to be conducted on a localised, rather than regional scale. Additionally, anthropogenic influences must be carefully managed, since the extent of mangrove habitat expansion into saltmarsh areas is unlikely to be a natural occurrence.

The National Wetlands Inventory (NWI) is the definitive source for wetland resources in the United States. The NWI production unit in Hadley, MA has begun to upgrade their digital map database, integrating descriptors for assessment of wetland functions. Updating is conducted manually and some automation is needed to increase production and efficiency. This study assigned landscape position descriptor codes to NWI wetland polygons and correlated polygon environmental properties with public domain terrain, soils, hydrology, and vegetation data within the Coastal Plain of Virginia. Environmental properties were applied to a non-metric multidimensional scaling technique to identify similarities within individual landscape positions based on wetland plant indicators, primary and secondary hydrology indicators, and field indicators of hydric soils. Individual NWI landscape position classes were linked to field-validated environmental properties. Measures provided by this analysis indicated that wetland plant occurrence and wetland plant status obtained a stress value of 0.136 (Kruskalâ s stress measure = poor), which is a poor indicator when determining correlation among wetland environmental properties. This is due principally to the highly-variable plant distribution and wetland plant status found among the field-validated sites. Primary and secondary hydrology indicators obtained a stress rating of 0.097 (Kruskalâ s stress measure = good) for correlation. The hydrology indicators measured in this analysis had a high level of correlation with all NWI landscape position classes due the common occurrence of at least one primary hydrology indicator in all field validated wetlands. The secondary indicators had an increased accuracy in landscape position discrimination over the primary indicators because they were less ubiquitous. Hydric soil characteristics listed in the 1987 Manual and NTCHS field indicators of hydric soils proved to be a relatively poor indicator, based on Kruskalâ s stress measure of 0.117, for contrasting landscape position classes because the same values occurred across all classes. The six NWI fieldâ validated landscape position classes used in this study were then further applied in a public domain digital data analysis. Mean pixel attribute values extracted from the 180 field-validated wetlands were analyzed using cluster analysis. The percent hydric soil component displayed the greatest variance when compared to elevation and slope curvature, streamflow and waterbody, Cowardin classification, and wetland vegetation type. Limitations of the soil survey data included: variable date of acquisition, small scale compared to wetland size, and variable quality. Flow had limitations related to its linear attributes, therefore is often found insignificant when evaluating pixel values that are mean of selected pixels across of wetland landscape position polygons. NLCD data limitations included poor quality resolution (large pixel size) and variable classification of cover types. The three sources of information that would improve wetland mapping and modeling the subtle changes in elevation and slope curvature that characterize wetland landscapes are: recent high resolution leaf-off aerial photography, high-quality soil survey data, and high-resolution elevation data. Due to the data limitations and the choice of variables used in this study, development of models and rules that clearly separate the six different landscape positions was not possible, and thus automation of coding could not be attempted.
Master of Science

Dissolved organic matter (DOM) is a complex mixture of organic compounds and represents the largest reservoirs of carbon (C) on earth. Particulate organic matter (POM) is another important carbon component in C cycling and controls a variety of biogeochemical processes. Estuaries, as important interfaces between land and ocean, play important roles in retaining and transforming such organic matter (OM) and serve as both sources and sinks of DOM and POM. There is a diverse array of both autochthonous and allochthonous OM sources in wetland/estuarine ecosystems. A comprehensive study on the sources, transformation and fate of OM in such ecosystems is essential in advancing our understanding of C cycling and better constraining the global C budget. In this work, DOM characteristics were investigated in different estuaries. Dissolved organic matter source strengths and dynamics were assessed in a seagrass-dominated subtropical estuarine lagoon. DOM dynamics controlled by hydrology and seagrass primary productivity were confirmed, and the primary source of DOM was quantified using the combination of excitation emission matrix fluorescence with parallel factor analysis (EEM-PARAFAC) and stable C isotope analysis. Seagrass can contribute up to 72% of the DOM in the study area. The spatial and temporal variation of DOM dynamics was also studied in a freshwated dominated estuary fringed with extensive salt marshes. The data showed that DOM was primarily derived from freshwater marshes and controlled by hydrology while salt marsh plants play a significant role in structuring the distribution patterns of DOM quality and quantity. The OM dynamics was also investigated in a mangrove-dominate estuary and a comparative study was conducted between the DOM and POM pools. The results revealed both similarity and dissimilarity in DOM and POM composition. The dynamics of both OM pools are largely uncoupled as a result of source differences. Fringe mangrove swamps are suggested to export similar amounts of DOM and POM and should be considered as an important source in coastal C budgets. Lastly, chemical characterizations were conducted on the featured fluorescence component in OM in an attempt to better understand the composition and origins of the specific PARAFAC component. The traditionally defined ‘protein-like’ fluorescence was found to contain both proteinaceous and phenolic compounds, suggesting that the application of this parameter as a proxy for amino acid content and bioavailability may be limited.

Very little protection has been afforded to wetlands1 and estuaries within the South African legislative framework.2 These ecosystems are extremely important and valuable to mankind, the flora and fauna.3 The continued destruction of wetlands and estuaries is the most heinous act of environmental vandalism on a worldwide scale today.4 Wetland and estuarine loss has been accelerated and extended by human activities such as mining,5 urbanisation,6 drainage, river diversion,7 groundwater abstraction as well as climate change.8 Time is running out for so many critically important sites and for the world at large.9 Without wetlands and estuaries the biosphere10 cannot continue to do its essential work.11 Despite, the importance of a range of resources and services12 which wetlands and estuaries provide, these have been taken for granted by humans.13 As a result hereof, the maintenance of wetlands and estuaries has received low priority in many countries.14 This is further precipitated by the lack of interest and ignorance which result in the conversion of wetlands and estuaries into man-made structures.15 Research has shown that the lack of information and the awareness of the importance of these ecosystems has the made the conservation legislation for these ecosystems a toothless dragon.16 People are becoming increasingly aware17 of the loss of wetlands and estuaries, once in abundance and now merely shadows of their former nature.18 To investigate this lack of protection, the starting point would be the global level.

博士
國立臺灣大學
土木工程學研究所
100
This study aimed at constructing an adaptive management model for wintering habitat of Common Teal (Anas crecca) in Hwajiang Wetland. A habitat suitability index (HSI) was developed to quantify the physical environments of the Teals’ preferred habitat. The Hwajiang wetland is an important wintering site for migratory Common Teal, whose population has dramatically declined in recent years, due most likely to the persistent degradation of habitats in this wetland. Due to river morphology, the changes of sediment deposition and vegetation expansion, have reduced the available habitat for the wintering Teal. Therefore, the rehabilitation of the Teals’ habitat is urgently needed for a sustainable management in this wetland. Point-count surveys of the Common Teal were conducted at a tidal pool, an inner channel and a tidal creek in Hwajiang Wetland and Teals’ positions were recorded from October 2008 to March 2009. Twenty-two sets of data and 3615 counted individuals were collected. Three habitat variables, including slope, elevation and the distance to the nearest vegetation, were displayed on 5 m × 5 m grid cells and analyzed with GIS software. Suitability index (SI) values of habitat variables were determined using the envelop curve of maximum abundance of common teals versus the habitat variables. The results showed that Common Teal preferred habitats with gentle slopes, median elevations and areas close to vegetation. The abundance of the Common Teal was highest in the grid cells with slopes ranging from 0.7 to 1.4%, bed elevation varying from 0.3 to 0.7 m above the mean sea level, and distance to the nearest vegetation shorter than 4 m. The HSI model was constructed by calculating the minimum value of the three SIs, and the suitability map of wintering common teals was generated to represent an integrated map of habitat quality in the area. A simple regression analysis indicated that the HSI model is a reliable indicator as the maximum numbers of the Common Teal in each grid cell increased significantly with the HSI values. Four types of habitat conditions, poor, fair, good and excellent, were determined based on the HSI values. The proportions of excellent habitat were 41.9%, 17.4% and 26.4% in the tidal pool, the inner channel and the tidal creek, respectively. A principle of rehabilitation was derived from the HSI model, with slopes smaller than 1.5%, elevations between 0.0m and 0.5m, and distance of less 25 m to the nearest vegetation. The rehabilitation area should be larger than 100 m in width and 250 m in length and adjacent to the existing Teal habitat. Three rehabilitation scenarios were simulated and characterized based on field survey and the HSI model. In addition, a horizontal two dimension numerical model, CCHE2D, was employed to simulate bank-full flow characteristics such as water surface elevation, flow velocity, shear stress and so on. The bathymetry and vegetation cover were assumed the same while the location was different. The shear stress evaluation indicated that the rehabilitation of the most upstream location is the best scenario because it has the lowest sediment deposition rate and represents a minimum maintenance effort needed in the future. This study provided a foundation for determining potential habitats and information on how to mitigate a degraded wetland for the Common Teal. It encompassed the aspects of monitoring, evaluation, and decision making that would benefit future management plans directed toward the Common Teal and other waterfowl species in Taiwan. It also provided an adaptive management model for application to similar projects of wetland rehabilitation and sustainable management.

碩士
國立中山大學
海洋環境及工程學系研究所
107
The wetlands ecosystem plays an important role on providing us with water and human health, supporting rich biodiversity and climate change, and storing more carbon than any other ecosystem. Because of this, the wetlands ecosystem has gradually been valued. Due to the increase of economic development, the area of wetland is lost faster and faster. Kaohsiung city promoted the concept of ecological corridors in 2003, and Yuanchungan wetland park was defined as one of the “West Kaohsiung Wetland Ecological Corridors” by Kaohsiung city government. The research site of this study is located in Yuanchungan wetland park. The wetland park is a compensatory wetland ecological habitat for restoration, and is the largest wetland in wetland ecological corridors of Kaohsiung, which is located on the south side of the Dian-Boa-Chi to the sea. In this study, the sampling dates were from August 2017 to March 2018 during four seasons for five sampling points. Based on the study, it could be comprehended that the variations of season, day and night, and differences in different habitats by water quality test and meteorological data collection. Through the water quality and stat is tidal analyses from SPSS, the correlation between the emission of greenhouse gases and water quality were analyzed. According to the analytical results, water temperature, pH, and dissolved oxygen were higher during the day than the night. Electrical conductivity and salinity were shown to be highly correlated with tides variation. Phosphate nutrients have the highest concentration is summer and autumn. The reason might be because orthophosphate was less absorbed by plants in the water in summer and autumn, while the effect of tidal current on the wetland sampling point making sediment disturbed to let orthophosphate in the sediment released into the water. For nitrite and nitrate in nitrogen-abundant nutrient salt, they have a similar concentration trend in summer and autumn, both of which presented high levels in the daytime and low levels in the nighttime because ammonia nitrogen in the salt was first oxidized to nitrite before it was further nitrified on nitrate. Ammonia nitrogen exhibited the highest concentration in spring. It might be because the condition because excessive as the most optimal environment for nitrifying bacteria in the wetland existing the reduced capability to remove ammonia nitrogen resulting in such accumulation. The correlation between greenhouse gas and water quality revealed that CO2 concentration was also highly correlated to the total organic carbon and chlorophyll a. It is speculated that this is probably due to the process of photosynthesis by plants in the wetland (including aquatic and self-supporting algae). CH4 also show a strong positive relationship with nitrate and total nitrogen, suggesting that microbes will instead to turn anaerobic hydrolysis under an anaerobic environment, as nitrification can still proceed at a low oxygenated condition of 0.3 mg/L in concentration. N2O is also displaying the same strong positive correlation with nitrate and total nitrogen because of the process of denitrification.

Because of the variety of ecological and economic functions they perform, estuaries and mangrove swamps are recognised as amongst the most valuable habitats on earth. However, estuaries and related mangrove swamps are threatened by human expansion and exploitation which leads to changes in land cover change within and surrounding these sensitive ecosystems. Such land cover changes can either have desirable or undesirable effects on natural ecosystems. Examples of undesirable impacts of land cover change include soil erosion and degradation, the removal of indigenous vegetation for human development, and the pollution of water. Without an effective means of identifying, monitoring and managing land cover changes over time, these sensitive ecosystems face a bleak and uncertain future. The researcher sought to determine whether wetland bird species could be used as an effective method of monitoring the environmental health of estuaries and mangrove swamps. In particular, the research sought to determine whether analysing fluctuations in the populations of wetland bird indicator species, as evident in the CWAC Bird Census data, could assist in monitoring and assessing undesirable and desirable land cover changes within the Mgeni Estuary and Beachwood Mangrove Swamps. An examination of the archival aerial imagery of the study area for the years 1991, 1997, 2003 and 2008 provided by the University and private companies, revealed significant changes in land cover over the last two decades. The land cover changes identified represent an actual decline or increase in the suitable foraging, roosting or reproductive habitats of wetland bird indicator species within the study area. The research focused on investigating whether fluctuations in wetland bird populations can be correlated with the recorded changes in land cover over the last two decades. The research discovered a direct and comprehensive link between fluctuations in specific populations of wetland bird indicator species and the land cover changes identified within the study area over a 20 year period.
Thesis (M.A.)-University of KwaZulu-Natal, Durban, 2010.

Thesis (Ph. D.)--Australian Catholic University, 2002.
A thesis submitted in total fulfillment of the requirements for the degree of Doctor of Philosophy. Includes bibliographical references (305-329). Also available in an electronic version via the internet.

博士
國立中山大學
環境工程研究所
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In the context of global warming and climate change, greenhouse gas (GHG) emission has received a considerable attention for the past decades. Of many natural GHG sources, wetland plays an important role in modulating the concentrations of GHGs in the atmosphere. This study aims to continuously monitor the emission of greenhouse gases (CO2, CH4, and N2O) from a constructed wetland. A self-designed dynamic floating chamber was applied to collect GHGs through a Teflon tube connected to the top of the chamber, and in-situ monitored the concentrations of GHGs with a non-dispersive infrared (NDIR) monitor to continuously measure GHG emissions, estimated its CO2 equivalent (CO2-e), and investigated the seasonal variation of GHGs. This study further correlated GHGs and water quality, and combined GHG data and net primary production data to understand GHG emission from a natural estuarine wetland and a wastewater treatment plant. The temporal variation of greenhouse gas (GHG) emission from petrochemical and integrated industry wastewater treatment plants (WWTP) was then investigated. Two approaches including an in-situ continuous monitoring and a typical grab sampling methods were further compared. The in-situ continuous monitoring method provided more detailed information regarding the temporal variation of GHG concentration. A sufficient sampling frequency (e.g., once every 6 hours) for the grab sampling method is required to effectively resolve the diurnal variation of GHG emission. This study highlights significant diurnal variation of GHG concentration in different wastewater treatment units. Only with proper and reliable sampling and analytical methods, it becomes possible to correctly identify the characteristics of GHG emissions and to develop strategies to curtail the GHG emissions from such an important source in response to regulatory measures and international treaties. This study revealed that N2O was the dominant species responsible for GHG emissions from the WWTPs and the emission factors of CH4, and N2O were higher in the equalization tank and final sedimentation tank compared to other units. We also compared the GHG emission factors of this study with other literatures, showing that the GHG emission factors were much lower than those measured in Netherlands, Australia, and IPCC, but similar to those measured in Japan. Wetland play a crucial role in modulating atmospheric concentrations of greenhouse gases (GHGs). Key factors controlling GHG emission from subtropical estuarine wetlands were investigated in this study, which continuously monitored the uptake/emission of GHGs by/from a subtropical estuarine wetland located in the Minjiang and Zhangjiang estuaries in the coastal region of southeastern China. A self-designed floating chamber was used to collect air samples on-site at three environmental habitats (P. australis, mangrove, mudflats, and river water). Based on its potential to increase global warming, N2O was the main contributor to the total GHG emission, with that emitted from the river water being the most considerable. Tidal water carried onto the marsh had its own GHG content and thus may act as a source or sink of GHGs. However, water quality had a large effect on GHG emissions from the riverwater whereas the tidal water height did not. Both high salinity and large amounts of sulfates in the wetlands explicitly inhibited the activity of CH4-producing bacteria, particularly at nighttime. This study also investigated the seasonal variation of GHG emissions and estimated their overall CO2 equivalent (CO2-e). The GHG emissions were further correlated with water quality to identify which water quality parameters dominated GHG emissions in an estuarine mangrove ecosystem. A positive correlation was found between CO2 emission and water temperature, dissolved oxygen (DO), and total phosphorus (TP) in the riverwater. CH4 emission was positively correlated with TP, DO, and NH4+-N, while N2O emission was significantly positively correlated with DO, TP, and total nitrogen (TN) in the riverwater.