Persistent Organic Pollutants (POPs), such as Polychlorinated Biphenyls (PCBs) or Hexachlorobenzene (HCB), released into water system. They will adsorb to particles, and incorporate into sediments. Thus the concentrations of PCBs and HCB in surface sediments provide information on recent contaminations. Besides, organisms in marine environment are influenced by the concentration in sediments, and so as the food chain. This study investigated the concentrations and characteristics of PCBs and HCB in surficial sediments of Kao-Ping Chi Estuary and nearby areas. The concentrations of PCBs and HCB in sediments were ranged from 1.432 to 6.681 (ng/g dry wt), and from 0.151 to 8.109 (ng/g dry wt¡^¡Awith an average of 3.219 and 1.978, respectively. Both of PCBs and HCB did not exceed the concentrations suggested by several sediment quality guidelines (SQGs). Compared with studies in other countries, the sediments in Kao-Ping coastal areas were more polluted by HCB. Neither PCBs nor HCB could correlate well with mean particle size or total organic carbon (TOC). The Toxic equivalents (TEQ) of dioxin-like PCBs and HCB were ranged from 0.014 to 0.061 pg-TEQ/g, and from 0.015 to 0.811 pg-TEQ/g, respectively. Using Principal Component Analysis, four possible principal components were found. These four principal components could account for 89.29% of the total variance. The first principal component was composed of highly chlorinated PCBs. The second principal component was composed of particle mean size and TOC. And the third and the fourth principal component were composed of di-, tri- PCBs and HCB. According to the factor score plot, the sample stations in this study could be divided into four groups. The first group was the stations that near the shore. The second group which contained stations were 4Km offshore. The third group contained stations with highly chlorinated PCBs. And the fourth group only contained one stations, D16. It was possible that there were other sources influenced station D16. In conclusion, the pollution in the surficial sediments was influenced by the distances from the pollutant sources and the particle size affected by tidal effect.

A 3D numerical model ¡V COHERENS has been applied to construct a coupled hydrodynamic and ecological model for studying Tapeng Bay, which is a coastal lagoon situated in southwest of Taiwan. The simulations have been carried out to study the influences and their interacting mechanisms among the tidal currents, nutrients and micro planktons in the Lagoon. Model results have been compiled for calculating the nutrient fluxes and the primary productions in the Tapeng Bay. Tapeng Bay is a semi-enclosed coastal lagoon, which has only one tidal inlet for exchanging lagoon water with the coastal currents along the Kaoping coast on the narrow shelf in southwest of Taiwan. The study area is situated in the tropical climate zone where has sunshine through out the year except the rainy days concentrated in the summer season, which is influenced by the southwest monsoon. There are several drainage channels that collect the untreated domestic sewerage and wastewater discharged from the fish farms surround the lagoon. The discharges in these channels are usually low during the dry season. The solid contained in the water are mostly settled on the channel beds. During the raining season, high discharges due to the storm rainfalls re-suspend the sediments and carry into the lagoon. These sediments, which contain high concentrations of suspended solids and nutrients, cause the Bay water highly eutrophied. Therefore, the Bay is fully influenced by the seasonal variations. There are a lot of aquaculture, i.e. oyster farming and fish cage, in the Bay area since the water is calm and rich. But the balance between the nature and the anthropogenic disturbance is breaking. Besides the water level variation generated from the tidal inlet, the fresh water inflow from 3 major channels are included in the model to simulate their influences to the hydrodynamics and the density driven circulation due to changing salinities and temperatures from these inlets. Plankton, detritus, dissolved nutrients and dissolved oxygen is taking into account as the model variables for this marine eco-system. The plankton growth is mainly generated due to temperature, light intensity and nutrient level. Only the nitrogen cycle has been considered in the model by assuming there are enough supply of phosphate and silicate. Model runs have been carried out according to different seasonal situations of the boundary conditions. Furthermore, climates (heats, lights, winds, etc) are also included in the model to distinct seasonal characteristics. It is shown, from the model results, that the currents mainly dominate the distribution of nutrients in the Tapeng Bay. The nutrient level controls plankton growth. The nutrient sources are mainly coming from the coastal currents (through tidal inlet) in the wintertime, whereas the summer source was from the drainage channels due to the wash out by the high discharge rates. Beside these, dissolved oxygen concentrations in the Bay water are strongly influenced by the plankton growth rate, faster the photosynthesis higher the DO concentrations. The eutrophication levels of the Tapeng Bay water have been compiled using the plankton carbon level modeled at various situations. According to the Nixon standard (1995), Tapeng Bay has eutrophication through out the year. Mesotrophic condition can be observed during the wintertime, whereas the hypereutrophic level can be concluded during the raining season.

Several flatfish species including southern flounder (Paralichthys lethostigma) recruit to estuaries during early life. Therefore, the evaluation of estuarine sites and habitats that serve as nurseries is critical to conservation and management efforts. I used biochemical condition and growth measurements in conjunction with catch-density data to evaluate settlement sites used by southern flounder in the Galveston Bay Estuary (GBE). In 2005, beam-trawl collections were made in three major sections of the GBE (East Bay, West Bay, Galveston Bay), and three sites were sampled in each bay. Within each sampling site, replicate collections were taken from 1) the marsh edge, 2) an intermediate zone, and 3) the open bay. The average size of southern flounder collected was between 12 and 19 mm standard length, and peak densities occurred in January and February. Catch data indicated that numeric densities of southern flounder were significantly greater in East Bay (2.75 per 100 m2) than in West Bay (0.45 per 100 m2) or in Galveston Bay (0.91 per 100 m2). Habitat-specific variation in density was not found. Otolith-based estimates of age indicated that the majority of southern flounder collected were 35-45 days old and derived from early December to early January hatch-dates. Growth rate differences were negligible across bays and habitats, with the average growth rate being 0.40 mm/day (range 0.21-0.76 mm/day). RNA:DNA ratios indicated that newly settled southern flounder in the GBE were in relatively high condition. Habitat-specific differences in RNA:DNA ratios were not observed; however, ratios were significantly lower in West Bay (average 8.0) than in East Bay (average 9.5) or in Galveston Bay (average 9.8), suggesting the condition of new recruits may vary across the GBE. Findings from this study indicate that southern flounder use a variety of habitats within the GBE during early life, and survival and recruitment success appear favorable regardless of settlement site. As a result, recruitment success of southern flounder may be less a function of the quality of nursery sites/habitats within the GBE than of other factors (e.g., larval supply to the estuary).

Knowledge of surface sediment distribution in Galveston Bay is important because it allows us to better understand how the bay works and how human activities impact the bay and its ecosystems. In this project, six areas of bay bottom were surveyed using acoustic techniques to make maps of bay bottom types and to investigate the types and extent of anthropogenic impacts. A total of 31 km2 was surveyed in six areas, one in Bolivar Roads (6.1 km2), one near Redfish Bar (3.1 km2), two in East Bay (12 km2), one southeast of the Clear Lake entrance (5.3 km2), and one in Trinity Bay (4.3 km2). Sidescan sonars (100 kHz and 600 kHz) were used to image the bay bottom, and a chirp sonar (2-12 kHz) was used to image subsurface sediment layers and bottom topography. In the side-scan records, objects as small as a few meters in extent were visible, whereas the chirp sonar records show a vertical resolution of a few tens of centimeters. The sidescan images display strong backscatter in some areas due to coarse sediments in addition to weak backscatter in areas of fine sediment. The bay bottom was classified using three levels of sonar backscatter ranging from high to low. Areas of differing sonar backscatter intensity were sampled with cores and grab-samples. High backscatter corresponded to coarse shell debris and oyster reefs, medium backscatter corresponded to a sand-silt-shell mixture, and low backscatter corresponded to silty loam. Chirp sonar records were classified as one of nine different bottom reflection types based on changes in amplitude and stratigraphy. Parallel, layered sediments are seen filling the bay valley and resting atop a sharp contact at which the acoustic signal fades out. Along the flanks of the valley fill the acoustic response revealed an absent or weakly laminated stratigraphy, whereas areas of high oyster productivity produced mounds, strong surface returns, and strong, shallow subsurface reflectors surrounding current oyster reefs. Anthropogenic features imaged with the sonar included sediment disruptions, such as the ship channels, dredge holes, gouges, and trawl marks, as well as debris, such as submerged boats, pipes, and unidentified objects.

Thesis (M.S.)--East Carolina University, 2009. / Presented to the faculty of the Department of Geological Sciences. Advisor: D. Reide Corbett. Title from PDF t.p. (viewed May 3, 2010). Includes bibliographical references.

This research provides insight into changes in volumetric flushing of the Tampa Bay estuary caused by synoptic scale wind events. The two main studies of this dissertation involve 1) using wavelet analysis to investigate the link between the El Niño-Southern Oscillation (ENSO) and the frequency and strength of volumetric flushing driven by synoptic variability and 2) using a multi-decadal model simulation to examine how extratropical/winter storms and hurricanes affect the overall flushing rates for Tampa Bay, FL. In the first study, two analyses are performed on 55 years of observational data to investigate the effect of multiple small wind events on estuarine flushing. First I use subtidal observed water level as a proxy for mean tidal height to estimate the rate of volumetric bay outflow. Second, I use wavelet analysis on sea level and wind data to isolate the synoptic sea level and surface wind variance. For both analyses the long-term monthly climatology is removed to focus on the volumetric and wavelet variance anomalies. The overall correlation between the Oceanic Niño index and volumetric anomalies is small (r2=0.097) due to the seasonal dependence on the ENSO response. The mean monthly climatology between the synoptic wavelet variance of elevation and axial winds have similar seasonal behavior. During the winter, El Niño (La Niña) increases (decreases) the synoptic variability, but decreases (increases) it during the summer. The difference in winter El Niño/La Niña wavelet variances is about 20% of the climatological value. ENSO can swing the synoptic flushing of the bay by 0.22 bay volumes per month. These changes in circulation associated with synoptic variability have the potential to impact mixing and transport within the bay. In the second study, volumetric changes from large scale weather events are investigated using a numerical circulation model simulation (1975-2006) to find the cumulative impact of flushing on the bay by extreme events. The strong wind speeds, duration of high winds and wind direction during these events all affect the amount of water flushed in and out of the estuary. Normalized volume anomalies are largest when wind components blow up/down the estuary in the NE/SW direction. Wind induced normalized flushing rates for all 10 extratropical/winter storms range from 12% to 40% and from 14% to 40% for all 10 hurricanes. All storms discussed in this study caused winds greater than 15 m s-1 (~30 knots). The direction of the winds had an impact on the flushing rates during these extreme events. Storm9 (February 1998) and Hurricane Gabrielle (September 2001) experienced the smallest total volume changes (14% and 13%). Both storms experienced weak axial and co-axial winds causing volume changes to be small. The Storm of the Century (March 1993) and Hurricane Frances (September 2004) saw the largest total volume changes of 40%. They both had strong winds blowing in the NE direction. Hurricane Frances had two wind peaks and lingered in the area for approximately 48 hours, so both strength and duration of winds played a large role in the total volume change. Total inflow and outflow rates per year show that there is year to year variability of flushing in Tampa Bay.

A vessel-mounted ADCP study focusing on channel-scale flow patterns in Galveston Bay near the Houston Shipping Channel and Mid-Bay Island is described. Winds of 5-7 m/s at 215-230◦ from N were present during data collection. For both peak ebb and flood conditions, the tidal circulation forced flow in a direction opposing the wind, perhaps due to a large-scale flow divergence forced by Mid-Bay Island. The strongest such currents were measured closest the island. During peak flood flow, the shape of the along-channel velocity profile for the open water upwind of the channel at Mid-Bay Island indicated uniform flow, and the salinity profile indicated a well-mixed water column. The near-island along- channel velocity profile showed a near-linear trend, and the salinity profile indicated a stratified water column. This suggested that the stratification had some effect the velocity profile shape, but further research is needed to better quantify this effect. During peak ebb flow, the near-island along-channel velocities were highly variable with respect to the mean velocity, indicating an area of active turbulence. Salinity profiles collected in the open water and near-island both showed stratification, something that was not seen during flood conditions. Differences in observations between flood and ebb flows can possibly be attributed to the survey location with respect to the chain of dredge spoil islands. During flood flows Mid-Bay Island is the first of the islands, and the flows surrounding the island may part of a developing horizontal boundary layer. During ebb flows the island is last in the chain relative to the direction of flow, and therefore the surrounding flows are well back from the leading edge of a horizontal boundary layer. / text

Contaminated sediments are periodically subjected to resuspension processes during either storm events or due to dredging. In sediments, metals are often contained in insoluble low bioavailability forms. Upon resuspension, however, biogeochemical processes associated with the exposure to more oxic conditions may lead to transformation and release of the metals, giving rise to exposure and risk in the water column. Batch experiments suggested that oxidation of reduced species and corresponding pH decrease were the most importance processes controlling metals release upon sediment resuspension. A mathematical model was implemented to better understand the complex underlying biogeochemical reactions that affect metals release. The model described the metals dynamics and other inter-related important biogeochemical factors well and was successful at predicting the metals release from different sediment reported in the literature. Tidal and other cyclic variations in oxygen, pH and other relevant parameters in the overlying water may also lead to cyclic transformations and release of metals from surficial sediments. In simulated estuarine microcosm experiments, cyclic variations in pH and salinity due to freshwater/saltwater exchange were shown to lead to cyclic variations in metal release. Both pH and salinity were important factors controlling interstitial dissolved metals concentrations, however, in terms of freely dissolved metals concentrations, which have been considered to be more related with toxicity and bioavailability, pH was the single most important parameter. The mathematical model was extended to the conditions of the cyclic behavior in an estuary and successfully described metals release under such conditions. It is believed that the model can be used to predict the metals behavior in other sediments and conditions by model calibration with a similar experimental approach to that used in this study. / text

Campanian M1 Sandstone is one of the major prospective sandstone units in the Tarapoa field in Oriente Basin, Ecuador. The M1 Sandstone is always markedly sharp based, averages 25 m in thickness, shows upward increasing marine bioturbation and generally fines upward from coarse to very fine grained sandstone. In cores, the sandstones at base are amalgamated coarse to fine grained with prominent cross stratification (dm thick), sometimes clearly bi-directional and contains mud drapes. These suggest strong tidal or fluvial-tidal currents in estuary channels or delta distributary channels. The finer grained intervals in the middle are brackish-water intensely bioturbated and dominated by mud drapes, wavy and flaser bedding suggestive of intertidal flats. Associated overlying coals and coaly shales suggest supratidal conditions. The sandstones at top are cross stratified and contain mud drapes. These again suggest strong tidal or fluvial-tidal currents in estuary channels or delta distributary channels. The stacking pattern of facies in M1 Sandstone reveals the evolution of the M1 depositional system, as well as the sequence stratigraphy of M1 sandstone. The evolution includes four stages of deposition which indicates an initial sea level rise, a subsequent sea level fall, and another sea level rise. Lateral sand-mud heterogeneity exists in the study area, forming “shale barriers”, i.e. elongate shale-rich zones that are lateral barriers to hydrocarbon migration. They are interpreted to be abandoned tidal channels filled with muddy tidal flat deposits during the sea level fall. An alternative hypothesis was established to explain the stacking pattern of facies in M1 Sandstone. A tide-dominated delta with poor fluvial input experienced intense tidal erosion and produced a sharp base at the base of M1 Sandstone. Then subtidal sand bars, intertidal flats, and supratidal sediments were deposited in sequence during a continuous regression. The core and well logs in an extension of the study area in the northwest is interpreted as more distal open shelf deposits, beyond the mouth of the Tarapoa estuary system, where transgressive tidal shelf ridges were coeval with the Tarapoa estuary system. This interpretation allows us to predict the environment between the two areas as a transition zone between tide-dominated estuary and open shelf. / text

The Dona and Roberts Bay watershed comprises one of the five major watersheds in Sarasota County, Florida. It is connected to the Gulf of Mexico via Venice Inlet. Like many estuaries in the Florida, significant modifications have been made to the drainage basins, principally to the main tributaries. The system has undergone several anthropogenic modifications to enhance water management efforts. Creeks that comprise fresh water input into the system have been dammed in order to inhibit the upstream flow of salt water during the dry season. They are also deepened or lengthened to allow for better drainage. In addition, biogenic activity has also had morphological effects on the system. There are numerous oyster bars, and mangrove forests that impose obstruction to the tidal and river flows. This has resulted in a highly complicated estuary system in terms of flow velocities and sedimentation patterns. The objectives of this study are to quantify the sediment characteristics and deposition-erosion trends and their relationship to flow patterns and other natural and anthropogenic factors within the system. A detailed sedimentary analysis was conducted based on 149 surface sediment samples and 29 drill cores. Spatial distribution of the sediment properties is quite complex, controlled by several interactive factors including; local sediment supply, intensity of the hydrodynamic processes, distribution of oyster bars and mangrove islands, and artificial structures. Sedimentation and erosion is significantly influenced by flood events. In some locations, such as the mouth of the fluvial channels, or the confluence of two creeks, the core data suggest that rapid sedimentation, driven by flood events, is responsible for the development of some of the large shoals. A 2-D depth-averaged circulation model was established for the study area. Many of the natural structures and artificial modifications to the watershed system are incorporated into the model. A close relationship between the flow intensity and sediment characteristics, and therefore, sedimentation-erosion tendency is identified. Remotely sensed data is also incorporated into the study in order to gain an understanding of the development of the estuary system over a ten-year period. Data suggests that the maturation of biogenic organisms that inhabit the system coincides with the development of complex sedimentation patterns.