Department of Geosciences

Encrusters have a proven history as indicators of environmental conditions in nearshore habitats and are useful in both ecological and paleoenvironmental research within benthic ecosystems. Off the coast of Pompano Beach, Florida, a Holocene storm deposit contains large accumulations of subfossil Acropora palmata fragments with these same encrusting organisms attached to their surfaces. The objective of this research was to create an inventory of encrusters found within the storm deposit and document their successional outgrowth to determine the post-depositional history of sampled coral fragments. Foraminifera and coralline algae were the most common species found, and various sequences of successional outgrowth were observed that indicated fragments were either deposited gradually, immediately buried, or reworked after initial burial. This information is vital for understanding modern biodiversity on the Pompano coast, and the development of nearshore benthic marine ecosystems during the mid-late Holocene.

Reefs off the coast of Florida face threats from stressors associated with climate change which leads to phase shifts. Under rapid climate change, a clear understanding of how reefs and their benthic organisms respond is still lacking and needs to be investigated. Using in situ imagery, a sponge cell model, and long-term benthic biota surveys, the effects of climate change on reef dynamics were explored in this dissertation project. Results from the in situ imagery found that differences in spectral signatures are found between functional groups (i.e., corals, sponges, and algae) and different species from substrate. Results based on a sponge cell model and transcriptomics data have found a resilience of these sponges to the predicted thermal extremes. Results from benthic biota surveys suggested that depth and light attenuation have the largest influence on the predicted distribution of corals, sponges, and algae at Pulley Ridge. Climate change has been impacting reef benthic biota starting at the organismal scale up to the reef scale. This research demonstrates the importance of monitoring reefs at a finer scale and determining the thresholds and limits of benthic biota to projected thermal extremes to better inform resource managers to preserve these irreplaceable ecosystems.

Plastic pollution in the marine environment is a global occurrence. Microplastics have been documented in numerous marine systems and organisms. Coastal estuaries and beach systems are at high risk for microplastic pollution. The distribution, abundance, and hazards microplastics present in these marine environments is not fully understood but are widely recognized as needed to support efforts aiming to protect and enhance these extremely valuable marine systems. This project aimed to quantify the abundance and variation of microplastics in estuarine mangrove and open coast beach sediments on Southeast Florida barrier islands, which are vulnerable and important coastal ecosystems. Barrier islands serve as a buffer between Florida’s wetland environments, reefs, and other marine habitats and may serve as a conduit or temporary sink for microplastics entering the ocean. The microplastic pollution present in estuarine mangrove and open coast beach systems may also elucidate patterns of microplastic pollution in the surrounding or similar coastal environments. There have been no extensive studies or monitoring efforts evaluating microplastics in Southeast Florida barrier islands sediments, nor comparing geomorphic properties of an area on microplastic accumulation. Study sites included back barrier estuarine mangroves and open coast beaches at three regionally similar but geomorphically distinct study sites throughout Palm Beach County, Florida. The sites were sampled seasonally in 2022 (i.e., summer and winter) to quantify the spatiotemporal distribution of microplastics.

With the escalating challenges posed by global warming, sea-level rise, and natural disasters like hurricanes and tropical storms, coastal erosion has become a critical issue along the US coasts. The economic significance of U.S. coastlines, multitude of services offered by these coastal areas, underscores the critical importance of addressing the threats posed by both natural and human-induced factors that lead to erosion and coastal loss. To enhance future planning and to promote resilience of these invaluable coastal resources, it is essential to gain a comprehensive understanding of the strategies employed to mitigate coastal erosion in response to the diverse array of driving forces. A widely embraced solution to this erosion, caused by both natural forces and human activities, is beach nourishment.
Historical assessments of beach nourishment at the regional level have been conducted, however, there remains a gap in national-level analysis examining the overarching trends and the diverse factors that impact these trends. This study aims to provide a comprehensive perspective on beach nourishment practices encompassing 16 coastal states, including the top ten highly nourished states, and an additional six states selected from various coastal regions. It delves into the multifaceted factors that shape these practices, offering a holistic understanding of the beach nourishment landscape at a national level. An extensive analysis of beach nourishment trends and the influence of factors such as sea level rise, storms, hurricanes, hurricane categories, and coastal management approval years on beach nourishment activities was conducted.

Eutrophication of urbanized estuaries is a global issue that continues to worsen as coastal development increases. The Indian River Lagoon (IRL) on Florida’s east-central coast is a eutrophic estuary that is experiencing harmful algal blooms of macroalgae and phytoplankton, as well as widespread seagrass losses. This is concerning as seagrasses provide many ecosystem services, including the provision of essential habitat. These alterations in benthic cover can have ecosystem level effects and require further investigation. Thus, drivers and effects of primary producer alterations in the IRL were investigated through analysis of long-term monitoring data, field surveys of faunal densities inhabiting macroalgae and bare bottom habitats, and stable nitrogen isotope (δ15N) analyses of primary producers, primary consumers, and secondary consumers. Long-term monitoring data from the northern IRL (NIRL) and Banana River Lagoon (BR) demonstrated there have been major seagrass losses coupled with increases in occurrence of the rhizophytic green macroalgae Caulerpa prolifera, which is now the dominant benthic cover in many locations. Multivariate analyses of long-term monitoring data spanning 2011-2020 suggested that the carbon to phosphorus ratio (C:P) of macroalgae is an important factor related to annual changes in benthic cover in the NIRL and BR; increased P-availability is correlated with these primary producer shifts. In situ collections of macroinvertebrates and resident fishes showed the current function and importance of macroalgae as habitat in the NIRL and BR, particularly in the relative absence of seagrass.

Much of Interior Alaska contains permafrost, which is a permanently frozen layer found within or at the surface of the Earth. Historically, this permafrost has experienced relative stability, with limited thaw during warmer summer months and fire events. However, largely due to the impact of a warming climate, among other factors, permafrost that would typically experience limited thawing during the summer season has recently been thawing at an unprecedented rate. Trapped by this layer of permafrost is a large quantity of carbon (C), which could be released into the atmosphere as greenhouse gases such as carbon dioxide (CO2) and methane (CH4). Due to the remoteness of the Arctic, there is a lack of yearly recorded permafrost thaw depth and snow depth values across much of the region. As such, the focus of this research was to establish a framework to identify how permafrost thaw depth and snow depth can be predicted across both a 1 km2 local scale and a 100 km2 regional scale in Interior Alaska by a combination of 1 m2 field data, airborne and spaceborne remote sensing products, and object-based machine learning techniques from 2014 – 2022. Machine learning techniques Random Forest, Support Vector Machine, k-Nearest Neighbor, Multiple Linear Regression, and Ensemble Analysis were applied to predict the permafrost thaw depth and snow depth. Results indicated that this methodology was able to successfully upscale both the 1 m2 field permafrost thaw depth and snow depth data to a 1 km2 local scale before successfully further upscaling the estimated results to a 100 km2 regional scale, while also linking the estimated values with ecotypes. The best results were produced by Ensemble Analysis, which tended to have the highest Pearson’s Correlation Coefficient, alongside the lowest Mean Absolute Error and Root Mean Square Error. Both Random Forest and k-Nearest Neighbor also provided encouraging results. The presence or absence of a thick canopy cover was strongly connected with thaw depth and snow depth estimates. Image resolution was an important factor when upscaling field data to the local scale, however it was overall less critical for further upscaling to the regional scale.

The term "collapse" has become a widely used term that oversimplifies the intricate histories of human-environment interactions. It has contributed to the belief that civilizations in the Americas and the tropics could not endure over time. However, the Manteño civilization of the Ecuadorian coast challenges this notion. Flourishing for a thousand years (ca. 650–1700 CE), the Manteños inhabited the neotropics at the gates of one of the world's most influential climatic forces, the El Niño-Southern Oscillation (ENSO). To thrive, the Manteños needed to navigate the extremes of ENSO during the Medieval Climate Anomaly (MCA, ca. 950–1250 CE) and the Little Ice Age (LIA, ca. 1400–1700 CE) while capitalizing on ENSO's milder phases. This research uses change detection analysis of Normalized Difference Vegetation Index (NDVI) on Landsat satellite imagery under various ENSO conditions from 1986 to 2020 in southern Manabí, where the 16th-century Manteño territory of Salangome was situated. The findings indicate that the cloud forests found in the highest elevations of the Chongón-Colonche Mountains provide the most resilient environment in the region to adapt to a changing climate. Further investigations of the cloud forest of the Bola de Oro Mountain using Uncrewed Aerial Vehicles (UAV) equipped with LiDAR, ground-truthing, and excavation uncovered a landscape shaped by the Manteños.

Previously published in Geographies 2023, 3(1), 161-177 (DOI: https://doi.org/10.3390/geographies3010010)
Inundation dynamics coupled with seasonal information is critical to study the wetland environment. Analyses based on remotely sensed data are the most effective means to monitor and investigate wetland inundation dynamics. For the first time, this study deployed an automated thresholding method to quantify and compare the annual inundation characteristics in dry and wet seasons in the Everglades, using Landsat imagery in Google Earth Engine (GEE). This research presents the long-term time series maps from 2002 to 2021, with a comprehensive spatiotemporal depiction of inundation.
In this paper, we bridged the research gap of space-time analysis for multi-season inundation dynamics, which is urgently needed for the Everglades wetland. Within a GIS-based framework, we integrated statistical models, such as Mann–Kendall and Sen’s Slope tests, to track the evolutionary trend of seasonal inundation dynamics. The spatiotemporal analyses highlight the significant differences in wet and dry seasons through time and space. The stationary or permanent inundation is more likely to be distributed along the coastal regions (Gulf of Mexico and Florida Bay) of the Everglades, presenting a warning regarding their vulnerability to sea level rise.

Coral reefs around the globe have undergone widespread degradation due to a myriad of natural and anthropogenic stressors. Climate warming, in particular, has emerged as an especially pressing threat, reshaping not only the biodiversity of coral-reef ecosystems worldwide, but also undermining the vital ecosystem services they provide. Yet amidst this decline, there is growing evidence that many coral species are expanding their ranges poleward into historically cooler subtropical and temperate marine environments thereby establishing critical refugia in response to climate warming. However, understanding the long-term viability and potential of these emerging refugia under ongoing climate change remains an area of active research, constrained by the temporal limitations of modern ecological studies. In addressing these challenges, this dissertation explores insights from a newly discovered late Holocene record of coral community development off southeast Florida, shedding light on historical coral range expansions, and providing critical context for assessing the future response of reef-building coral communities to continued climate warming. Using a combination of high-precision uranium-thorium dating and detailed paleoecological analysis of well-preserved subfossil coral skeletons, we provide new evidence that diverse coral communities dominated by Acropora spp. expanded to the nearshore hardbottom habitats off northern Broward County during a period of warming in the subtropical western Atlantic between 3500 and 1800 years before present. However, despite this historical precedent of range expansion in response to regional warming, modern comparisons reveal a significant shift towards low diversity coral assemblages dominated by stress-tolerant coral taxa, suggesting that ongoing range expansions may be constrained by new challenges that were absent during the late Holocene. These findings underscore the need for comprehensive conservation strategies informed by historical baselines to navigate the complex dynamics of coral reefs in the face of climate change.

This study examined the environmental and anthropogenic factors that may influence loggerhead sea turtle nest site selection and how these factors vary between successful nesting attempts and false crawls on a high-density sea turtle nesting beach in Boca Raton, Florida. Beach morphology, sand texture, and nests’ proximity to artificial structures were measured using a combination of drone-based photogrammetry, traditional surveys with Real Time Kinematic Global Positioning System (RTK GPS), and sediment granulometry. Proximity to dune crossover stairs was significantly different between nests and false crawls, and the probability of a false crawl occurring decreased as proximity to dune crossover stairs increased. The results of this study will provide researchers with a new tool for nest monitoring and a better understanding of the microhabitat cues that may influence loggerhead sea turtle nest site selection and aid in guiding beach and sea turtle management decisions.