I investigated how land use and human activities affect the sources and cycling of carbon (C) in subtropical rivers. Annually rivers receive a large amount of terrestrial C, process a portion of this C and return it to the atmosphere as CO2. The rest is transported to the ocean. Land use and human activities can affect the sources and fate of terrestrial C in rivers. However, studies on these effects are limited, especially in the humid subtropics. I combined measurements of the partial pressure of dissolved CO2 (pCO2), C isotopes (13C and 14C) and solid-state 13C nuclear magnetic resonance (NMR) to study C cycling in three subtropical rivers in Texas, two small rivers (Buffalo Bayou and Spring Creek) and a midsized river (the Brazos). My pCO2 data show that small humid subtropical rivers are likely a large source of atmospheric CO2 in the global C cycle. My measurements on pCO2, C isotopic and chemical composition of dissolved inorganic C (DIC) and particulate organic C (POC) revealed four types of effects of land use and human activities on river C cycling. First, oyster shells and crushed carbonate minerals used in road construction are being dissolved and slowly drained into Buffalo Bayou and the lower Brazos and may be a source of river CO2 released to the atmosphere. Second, river damming and nutrient input from urban treated wastewater stimulate algal growth and reduce CO2 evasion of the middle Brazos. Third, urban treated wastewater discharge is adding old POC to the middle Brazos and decomposition of the old POC adds to the old riverine DIC pool. Fourth, agricultural activities coupled with high precipitation enhance loss of old organic C (OC) from deep soils to the lower Brazos, and decomposition of the old soil OC contributes to the old CO2 evaded. I document for the first time the river C cycling effects of the use of carbonate minerals in construction and the riverine discharge of urban wastewater. Results presented here indicate the need to study disturbed river systems to better constrain the global C budget.

Water quality and wetlands represent two vital elements of a healthy coastal ecosystem. Both experienced substantial declines in the U.S. during the 20th century. Overall coastal wetland cover decreased over 50% in the 20th century due to coastal development and water pollution. Management and legislative efforts have successfully addressed some of the problems and threats, but recent research indicates that the diffuse impacts of climate change and non-point source pollution may be the primary drivers of current and future water-quality and wetland stress. In order to respond to these pervasive threats, traditional management approaches need to adopt modern technological tools for more synoptic, frequent and fine-scale monitoring and assessment. In this dissertation, I explored some of the applications possible with new, commercial satellite imagery to better assess the status of coastal ecosystems. Large-scale land-cover change influences the quality of adjacent coastal water. Satellite imagery has been used to derive land-cover maps since the 1960’s. It provides multiple data points with which to evaluate the effects of land-cover change on water quality. The objective of the first chapter of this research was to determine how 40 years of land-cover change in the Tampa Bay watershed (6,500 km2) may have affected turbidity and chlorophyll concentration – two proxies for coastal water quality. Land cover classes were evaluated along with precipitation and wind stress as explanatory variables. Results varied between analyses for the entire estuary and those of segments within the bay. Changes in developed land percent cover best explained the turbidity and chlorophyll-concentration time series for the entire bay (R2 > 0.75, p < 0.02). The paucity of official land-cover maps (i.e. five maps) restricted the temporal resolution of the assessments. Furthermore, most estuaries along the Gulf of Mexico do not have forty years of water-quality time series with which to perform evaluations against land-cover change. Ocean-color satellite imagery was used to derive proxies for coastal water with near-daily satellite observations since 2000. The goal of chapter two was to identify drivers of turbidity variability for 11 National Estuary Program water bodies along the Gulf of Mexico. Land cover assessments could not be used as an explanatory variable because of the low temporal resolution (i.e. approximately one map per five-year period). Ocean color metrics were evaluated against atmospheric, meteorological, and oceanographic variables including precipitation, wind speed, U and V wind vectors, river discharge, and water level over weekly, monthly, seasonal and annual time steps. Climate indices like the North Atlantic Oscillation and El Niño Southern Oscillation index were also examined as possible drivers of long-term changes. Extreme turbidity events were defined by the 90th and 95th percentile observations over each time step. Wind speed, river discharge and El Niño best explained variability in turbidity time-series and extreme events (R2 > 0.2, p < 0.05), but this varied substantially between time steps and estuaries. The background land cover analyses conducted for coastal water quality studies showed that there are substantial discrepancies between the wetland extent estimates mapped by local, state and federal agencies. The third chapter of my research sought to examine these differences and evaluate the accuracy and precision of wetland maps using high spatial-resolution (i.e. two-meter) WorldView-2 satellite imagery. Ground validation data showed that wetlands mapped at two study sites in Tampa Bay were more accurately identified by WorldView-2 than by Landsat imagery (30-meter resolution). When compared to maps produced separately by the National Oceanic and Atmospheric Administration, Southwest Florida Water Management District, and National Wetland Inventory, we found that these historical land cover products overestimated by 2-10 times the actual extent of wetlands as identified in the WorldView-2 maps. We could find no study that had utilized more than six of these commercial images for a given project. Part of the problem is cost of the images, but there is also the cost of processing the images, which is typically done one at a time and with substantial human interaction. Chapter four explains an approach to automate the preprocessing and classification of imagery to detect wetlands within the Tampa Bay watershed (6,500 km2). Software scripts in Python, Matlab and Linux were used to ingest 130 WorldView-2 images and to generate maps that included wetlands, uplands, water, and bare and developed land. These maps proved to be more accurate at identifying forested wetland (78%) than those by NOAA, SWFWMD, and NWI (45-65%) based on ground validation data. Typical processing methods would have required 4-5 months to complete this work, but this protocol completed the 130 images in under 24 hours. Chapter five of the dissertation reviews coastal management case studies that have used satellite technologies. The objective was to illustrate the utility of this technology. The management sectors reviewed included coral reefs, wetlands, water quality, public health, and fisheries and aquaculture.

Coastal zones receive massive terrestrial inputs of nutrients and organic matter, and play an important role in biogeochemical cycles. The interactions of river inputs, ocean currents, atmospheric exchanges, anthropogenic influences, and biologically active ecosystems make CO2 system studies in coastal waters highly challenging. This work focuses on improving our understanding of the CO2 system in coastal waters through (1) development of a new methodology for measurements of CO2 system parameters in the field; (2) observations of large spatial and temporal CO2 system variations in coastal waters; and (3) characterization of the influence of organics on CO2 system behavior in coastal waters. A novel portable light-emitting-diode (LED) photometer was developed to provide low-cost seawater pH measurements in the field. With meta cresol purple (mCP) as the indicator, the photometer produces pHT measurements within ± 0.01 units of state-of-the-art spectrophotometric measurements (7.6 ≤ pH ≤ 8.2, 30 ≤ S ≤ 36.2, and 15 oC ≤ t ≤ 30 oC). With a simple “do-it-yourself” (DIY) construction design, a hundredfold reduction in cost relative to benchtop spectrophotometric systems, and routine calibration-free operation in the field, the DIY photometer is an ideal replacement for pH test strips or consumer-level potentiometric probes. Applications of special interest include education, citizen science, coastal zone monitoring, and aquaculture and aquarium management. Subannual variability of total alkalinity (TA) distributions in the northeastern Gulf of Mexico (GOM) was examined through the use of TA data from ship-based water sampling, historical records of riverine TA, and contemporaneous model output of surface currents and salinity. Variability of TA observed in the upper 150 m of the GOM water column was primarily controlled by subannual variations in the extent of mixing between seawater and river water. A transition in TA distribution patterns between the river-dominated northern margin (near the Mississippi–Atchafalaya River System) and the ocean current-dominated eastern margin (West Florida Shelf) was observed. A riverine alkalinity input index was developed to highlight riverine TA contributions. Contributions of organic alkalinity (Org-Alk) to TA were investigated in coastal waters from three different environments (estuary, urban, mangrove) and offshore sites in the Gulf of Mexico. The difference in alkalinity (∆TA) between TA measured by direct titration (TAmeas) and calculated (TAcal) from observations of DIC and pH was used as an estimate of Org-Alk. Average values of ∆TA were 0.1 ± 5.0 µmol kg-1 at coastal sample sites outside the Mississippi-Atchafalaya River Estuary (n = 17), 1.9 ± 5.2 µmol kg-1 in offshore waters (n = 14) in the northern Gulf of Mexico, 33.6 ± 18.0 µmol kg-1 in the Suwannee River Estuary (n = 17), and 16.0 ± 25.4 µmol kg-1 in sites that included Tampa Bay, the Caloosahatchee River, and the Ten Thousand Islands area (n = 55). In addition to Org-Alk assessments based on measurements of ∆TA, a novel two-step spectophotometric titration method was developed for the characterization of Org-Alk. Direct titrations showed substantial Org-Alk in coastal samples (n = 5), and the Org-Alk values obtained from the two-step titrations showed good agreement with results from ∆TA calculations. The spectrophotometric titration data were used in model fits to evaluate the dissociation constants (pKi) of the natural organic acids. The pKi of the organic acids were within the previously reported range for riverine fulvic acids.

The objective of this thesis was to determine if there were any correlations in the distribution of cetaceans, especially sperm whales (Physeter macrocephalus), pantropical dolphins (Stenella attenuata), bottlenose dolphins (Tursiops truncatus), and Risso’s dolphins (Grampus griseus) in the northern Gulf of Mexico because of the influence of oil and gas production and exploration. This research is important because of the lack of knowledge about the impact of anthropogenic sounds from oil and gas exploration and production (E&P) on cetacean distribution in the Gulf of Mexico. I analyzed cetacean visual line-transect survey results from the Gulf of Mexico for period of 1992 – 2001. I divided this time span into an early period (1992 – 1997) and a late period (1998 – 2001). I overlayed the locations of cetacean sightings and the locations of oil and gas E&P platforms to demonstrate their close association in space, and tested a hypothesis that distribution would shift south correlated with changes in distribution of E&P. I compared the distributions of cetacean sightings in the entire Gulf of Mexico, and separated the Gulf of Mexico into east and west, between the early period and the late period. The east Gulf of Mexico represents an area without oil and gas E&P platforms and the west Gulf of Mexico is the area where oil and gas E&P platforms are located. The null hypothesis for these tests was that there was no difference in cetacean distribution between the early period and the late period. I also compared the distribution of sperm whales, pantropical dolphins, bottlenose dolphins, and Risso’s dolphins in the entire Gulf of Mexico, both east and west, between the early and late periods. I expect if distribution changes were correlated with changes in E&P distribution, then there will be a shift south in the western Gulf. Changes in distribution in the eastern Gulf would not be correlated with E&P. I found that the sightings per unit effort (SPUE) of all cetacean sightings in the entire Gulf of Mexico shifted to the south in the late period, as compared to the early period .The distribution of all cetacean sightings for the late period (1998-2001) was significantly different compared to the distributions of all cetacean sightings in the early period (1992-1997). The SPUE of sperm whale and bottlenose dolphin distributions were shifted to the north in the late period (1998-2001) compared to the early period (1992-1997). While pantropical dolphin distributions were significantly shifted to the south between the two time periods. I observed that the SPUE of all cetaceans sightings in the east Gulf of Mexico for the early period (1992-1997) were shifted to the south compared to the west, which were not different. The SPUE for sperm whales in the east for the early period were marginally shifted to the north in comparison to the west, which were also shifted further north. The SPUE for Risso’s dolphins in the east were shifted further north while in the west SPUE were shifted to the south. The SPUE for pantropical dolphin sightings were shifted to the north in both the east and west regions. While the SPUE for bottlenose dolphin sightings were shifted to the north in both the east and west Gulf of Mexico. My SPUE results suggest that pantropical dolphins, like the total cetaceans examined here, have shifted their distributions in the entire northern Gulf of Mexico to the south. However, in areas of high oil and gas E&P platforms the distributions of sperm whales and bottlenose dolphins did not shift their distributions from the early period to the late period to the south even though these E&P activities have shifted to the south over the past two decades as they expanded into the deeper waters of the northern Gulf of Mexico. Therefore, there is little evidence that large scale changes in the latitudinal distribution of marine mammals in the Northern Gulf have occurred as a result of greater offshore E&P activity.

This work examines several volume attributes extracted from 3D seismic data with the goal of seismic facies classification and lithology prediction in intraslope minibasins. The study area is in the Keathley Canyon protraction (KC), within the middle slope of the Northern Gulf of Mexico (GOM). It lays within the tabular salt and minibasins province downdip of the main Pliocene and Pleistocene deltaic depocenters. Interaction between sedimentation and mobile salt substrate lead to the emergence of many stratigraphic patterns in the intraslope minibasins. Interest in subsalt formations left above salt formations poorly logged. Facies classification using Artificial Neural Network (ANN) was applied in those poorly logged areas. The resultant facies classes were calibrated and used to predict the lithology of the recognized facies patterns in an intraslope minibasin, away from well control. Three types of facies classes were identified: Convergent thinning, convergent baselaping and bypassing. The convergent baselaping are found to be the most sand rich among all other facies.

The deep-sea is the largest habitat on earth, containing over 90 percent of the world’s oceans and home to over 20,000 species. Deep-sea ecosystems are increasingly impacted by human activities including fishing and oil extraction. To understand potential impacts on deep-sea food webs, it is crucial to gather baseline data in these systems. I quantified the trophic interactions of three groups of deep-water animals across a range of trophic levels living in the northern and eastern Gulf of Mexico using stable isotope analysis. First, I propose methods for correcting δ15N values for the presence of nitrogenous metabolic waste products (e.g., urea) in muscle tissue using chemical extractions and/or species-specific mathematical normalizations. Significant differences in δ15N, %N, and C:N values as a result of extractions were observed in eight of ten shark and all three hagfish species. The δ15N values increased, but shifts in %N and C:N values were not unidirectional. Mathematical normalizations for δ15N values were successfully created for four shark and two hagfish species. I then describe the trophic interactions of three consumer assemblages. Carbon isotopic values indicate a heavy reliance on allochthonous nutrient inputs from surface waters. Nitrogen isotopic values reveal somewhat atypical taxa as top predators in the deep sea. Shark, teleost, and invertebrate species across a wide range of body sizes are feeding at a similar trophic level. This apparent lack of size structuring could be the result of a high degree of opportunistic scavenging or perhaps feeding at many trophic levels simultaneously in an oligotrophic system. There was a high degree of isotopic niche overlap among species within each consumer assemblage, perhaps the result of limited nutrient resources in the deep-sea. In general, individuals from the northern sampling stations displayed higher δ13C and δ15N values than those from the eastern sites. With the exception of a few species, there were no strong relationships between body size and isotopic values. The present study is among the first characterizations of the trophic structure of deep-sea organisms in the Gulf of Mexico and establishes system baselines for future studies describing deep-water systems and investigating anthropogenic impacts.

Artificial reefs have been deployed throughout the world’s oceans to act as habitat and fishing enhancement tools. To expand current research on the role of artificial reefs in the marine community, ordination and multivariate regression methods were used here to analyze survey data of natural and artificial reefs. The reefs, located in the Northern Gulf of Mexico (NGOM) and on the West Florida Shelf (WFS), had been previously surveyed from 2004 to 2015 using remote operated vehicle and stationary video techniques. This study tested the hypothesis that similar functional roles are accounted for at both natural and artificial reef sites even if species composition varies. Secondly, it examines the role of environment and fisheries in determining the assemblages. Artificial reefs tended to host communities that were as biodiverse as natural reefs, although not necessarily composed of the same species. Results of an ordination confirmed that as the classification was broadened from the level of species, to family, to functional group, the assemblages on each reef type (natural vs. artificial and NGOM vs WFS) appeared more similar. Dominant groups were present at all levels of classification and included the families Lutjanidae and Carangidae, as well as functional groups Red Snapper and Small Reef Fish. Both natural and artificial reefs tended to be dominated by one of the following: Lutjanidae, Carangidae, or Small Reef Fish, although a continuous gradient was found across the extremes of natural versus artificial reefs. Generalized Additive Models were developed to examine the influence of reef type, location, environment and fishing intensity covariates. Results indicated that for both natural and artificial reefs, the abundance of families and functional groups can be influenced by environmental factors. In both cases, there is strong spatial autocorrelation suggesting connectivity with neighboring reefs.

Several studies have found separation of biogeographic provinces on the West Florida Shelf (WFS), but the location of this separation differs depending on different organisms with faunal boundaries proposed at Apalachicola, Cedar Key, Anclote Key. Tampa Bay, Charlotte Harbor, Cape Romano, or Cape Sable. Biogeographic boundaries can be gradual over a given space and are often species-specific. Analyses of marine benthic mapping and community characterization of Florida’s West-central coast shallow water (depth) hardbottom habitats indicate a major shift in the benthos across Tampa Bay. Quantitative benthic surveys of 29 sites yielded a total of 4,079 individuals of nine stony coral species and 1,918 soft coral colonies. Populations were dominated by four species of corals: Siderastrea radians, Oculina robusta, Solenastrea hyades, and Cladacora arbuscula. Most corals were less than 10 cm in diameter. Cluster analyses of coral density and major functional group percent cover showed distinct differences in hard and soft coral densities and species demographics from south to north with clear spatial patterns between regions. These benthic hardbottom coral communities change over a relatively small spatial scale (10’s of km), indicating a biogeographical province or ecosystem region boundary in marine benthic communities at, or very near, the mouth of Tampa Bay. Broader studies are needed to identify the shifts in benthic community biogeography along the West Florida Shelf.

No description available.

No description available.