Coastal ecology

As sea level rises, saltwater migration can threaten coastal ecosystems and beach-dune environments, which negatively impacts coastal flora. This study uses ground penetrating radar (GPR) to evaluate the spatiotemporal variability of saltwater migration in the near shore at high lateral resolution (i.e. cm) by using daily micro tidal cycles as analogs to infer saltwater migration. Time-lapse GPR profiles were collected at low and high tide capturing phase lags of the tidal flux through different substrates. GPR measurements were collected at two sites in Miami with contrasting lithologies: a) Crandon Park, composed of unconsolidated sand; and b) the Barnacle Historic State Park, composed of the Miami Limestone Formation. Laboratory-scale GPR measurements were collected over samples mimicking field conditions. The results may be helpful to identify regions vulnerable to saltwater migration in the near shore based on lithological variability, and to mitigate negative impacts for flora in beach-dune habitats during sea level rise.

As sea levels continue to rise, the projected damage that will ensue presents a great challenge for conservation and management of coastal ecosystems in Florida. Since Juncus roemerianus is a common marsh plant throughout Florida with unique growing characteristics that make it a popular restoration plant, this study implemented a 20 week greenhouse split plot experiment to examine the effects of sea level rise on J. roemerianus and ultimately determine its tolerance ranges to salinity and inundation in a high nutrient environment. Overall, salinity level and the interaction effect of salinity level and water level had the greatest effects on measured growth parameters including average mature height, maximum height, density, basal area, root length, and biomass. An inverse relationship between increasing salinity and the measured growth variables was observed with the greatest growth and survivability in 0 ppt water, survivability and reduced growth in 20 ppt water, survivability and little growth in 30 ppt water, and nearly complete senesce in 40 ppt water. This was the first laboratory study to determine the effect of 40 ppt water on J. roemerianus. Elevated water levels resulted in higher growth variables in the 20 ppt, 30 ppt, and 40 ppt treatments while inundated water levels produced higher growth variables in the 0 ppt treatment despite previous research finding inundation to have completely adverse effects on J. roemerianus. It is likely that the high nutrient environment provided for this study is the cause for this anomaly. The results of this study have major implications for the future of coastal ecosystems that are dominated by stands of J. roemerianus in South Florida and can be used in conjunction with studies on bordering marsh plants to predict shifts in the ecosystems of Florida that are responding to sea level rise scenarios.

Plant interactions (e.g., competition, facilitation) are critical drivers in
community development and structure. The Stress Gradient Hypothesis (SGH)
provides a predictive framework for how plant species interactions vary inversely
across an environmental stress gradient, predicting that facilitation is stronger with
increasing levels of stress. The SGH has been supported in numerous ecosystems
and across a variety of stress gradients, but recent research has demonstrated
contradictory results. These discrepancies have led to SGH revisions that expand its
conceptual framework by incorporating additional factors, such as other stressor
types and variations in species life history strategies. In this dissertation, I examine
a further modification of the SGH by proposing and testing a Multiple Stress
Gradient Hypothesis (MSGH) that considers how plant interactions vary along a continuous gradient of two co-occurring stressors using mangrove and salt marsh
communities as a case study. In Chapter 1, I outline the predictive framework of a
MSGH, by creating a series of predictions of species interactions. The components
of the MSGH predict that stressors of similar types (e.g., resource and nonresource)
will have similar effects and be additive. On the other hand, varying
species life history strategies and life stages will lead to extremes of plant
interactions. In Chapter 2, I performed a series of experiments to test the various
components of the MSGH. In Chapter 3, I performed a large-scale observational
study to test whether multiple co-occurring stressors altered the cumulative effects
on plant interactions, and if these stressors should be grouped (e.g., resource and
non-resource, abiotic and biotic, etc.) to enhance predictability. From a series of
studies conducted herein, I concluded that co-occurring stressors are important
factors that control complex species interactions as shown in my MSGH modeling
approach. Further, future theories need to incorporate species-specific and stressor specific
grouping when modeling how species interactions shape communities.

A novel, 'near-real' time technique; peptide nucleic acid chemilumiscent in situ hybridization (PNA CISH), was developed and validated for detecting, enumerating and identifying potential indicators (Staphyloccus aureus and Pseudomonas aeruginosa) of beach quality. To understand the dynamics of bacterial indicators a plethora of physical, chemical and biological parameters were tested under field and lab conditions. Escherichia coli tagged with green fluorescence protein (GFP) was used to assess the impact of wave energy and rainfall on seawater counts. PNA CISH and plate counts correlated strongly (r = 0.94 to r = 0.86). Temperature, salinity, nutrient availability and predation significantly influenced the survival of indicators. Rainfall and wave energy affected the re-suspension of bacteria from sand onto overlying water. Overall PNA CISH provides a reliable rapid method for beach monitoring. The implications of beach topography and sampling time on the numbers of Clostridium perfringens and other potential indicators are discussed. Data suggest a revision of policy for tropical sandy beaches.

Cone snails are predatory marine animals that rely on their venom components to immobilize and capture their prey. According to the type of prey preference, cone snails can be divided into three groups: vermivorous, molluscivorous and piscivorous. Conus ermineus had been identified as the only piscivorous snail of the Atlantic Ocean. Cone snail venom is a complex and rich sources of natural toxins. The majority of the components of the venom are peptidic in nature, and they act over different ionic channels and membrane receptors. Initial studies using mixture of venom collected from dissected venom ducts concluded that the venom from the same species do not exhibit unusual peptide polymorphism [Olivera, Hillyard, et al., 1995] and that the only major difference between individuals of the same species are different concentrations of the venom components [Vianna, et al., 2005]. For this study, peptides in the injected venom were collected from individual snails and characterized usin g analytical RP-HPLC for a maximum of three years. The different fractions collected were processed through capillary HPLC coupled with Q-TOF ESI-MS, and compared with analytical RP-HPLC fractions processed with MALDI-TOF MS. This study demonstrates that there is an animal-to-animal variation in the peptide components of the injected venom. The injected venom remains relatively constant over time for specific specimens in captivity. Finally, there are some peptides that had been found in all specimens both by MALDI-TOF MS and by ESI-MS. In this study, these peptides are called "molecular fingerprint" peptides. Based on matches of their derived masses to those predicted by published cDNA sequences, nine novel peptides were putatively identified. This study establishes that variations due to enzymatic posttranslational modification are omitted when we consider only information extrapolated from cDNA.