University of Puerto Rico at Mayagüez Institutional Repository
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Publication A preliminary assessment of the biodiversity of inner-coastal zooplankton of southwestern Puerto Rico emphasizing the use of a DNA metabarcoding approach(2025-05-13)Zooplankton communities are fundamental to marine food webs and ecosystem functioning, yet their biodiversity in tropical regions like Puerto Rico remains understudied. It is crucial to understand the zooplankton biodiversity given the current risks posed by climate change and anthropogenic pressures. This study provides the first metabarcoding assessment of zooplankton diversity in La Parguera, southwestern Puerto Rico, combining cytochrome c oxidase subunit 1 (CO1) metabarcoding with traditional microscopy to offer a comprehensive overview. Zooplankton samples were collected during autumn and winter (2019–2020), across diel cycles and using three mesh sizes (63 µm, 202 µm, 500 µm). Microscopy results suggested higher abundance of calanoid copepods (e.g. Paracalanus sp. and Acartia spp.), compared to other organisms, consistent with previous studies. In contrast, metabarcoding revealed a more diverse community than the microscopy methods, with high relative abundance of meroplanktonic molluscs (e.g., Caenogastropoda) and arthropod larvae (e.g., Mithrax hispidus), likely due to primer biases and enhanced detection of larval stages. The CO1 dataset enabled the detection of cryptic taxa (e.g., Aglaophenia latecarinata) using a customized bioinformatic pipeline. Statistical analyses, including t-tests and ANOVAs, revealed no significant differences in total zooplankton DNA abundance across diel, seasonal, or mesh-size gradients, suggesting short-term stability. A significant effect of season was observed in a two-way ANOVA model, but this result was likely driven by unbalanced sampling effort rather than ecological differences. This work establishes a critical baseline for zooplankton research in Puerto Rico after two decades of limited study, highlighting the value of integrative approaches to monitor biodiversity shifts in vulnerable tropical ecosystems.Publication Incidencia de mosca blanca (complejo de 𝘉𝘦𝘮𝘪𝘴𝘪𝘢 𝘵𝘢𝘣𝘢𝘤𝘪: Hemiptera; Aleyrodidae) y otros vectores de virus en el cultivo de la sandía, 𝘊𝘪𝘵𝘳𝘶𝘭𝘭𝘶𝘴 𝘭𝘢𝘯𝘢𝘵𝘶𝘴 (Thunb) Matsum & Nakai, en el sur de Puerto Rico(2025-05-13)The whitefly, Bemisia tabaci G. (Hemiptera: Aleyrodidae), the melon thrips, Thrips palmi (Thysanoptera: Thripidae), and the cotton aphid, Aphis gossypii (Hemiptera: Aphididae), are three of the main insect virus vectors in watermelon crops. The objectives of this research were: (1) to determine the incidence of B. tabaci, T. palmi, and A. gossypii in: “Crimson Sweet” watermelon fields from two commercial farms Farm 1 (latitude 18ᵒ00’09’’ N longitude 66ᵒ24’56’’ W) and Farm 2 (latitude 17ᵒ57’45’’ N longitude 66ᵒ22’54’’ W), two watermelon greenhouses, fields with cucurbits near to watermelons crops, and in weeds near to watermelon crops, and (2) To evaluate management strategies for B. tabaci, T. palmi, and A. gossypii in two different seasons, and evaluate their preference of six watermelon cultivars. Farms 1 and 2 showed good management of B. tabaci, as for T. palmi, both farms had good control. The highest incidence of B. tabaci in the greehouse of Farm 1 was in the first week, while for T. palmi, it was in the fifth week. In the greenhouse of Farm 2, the highest incidence of B. tabaci was in the fifth week, and the most effective treatment in reducing B. tabaci and T. palmi was in the fourth week. As for other cucurbits, the Spring squash had the highest incidences of B. tabaci and T. palmi. The weeds with the highest incidence of B. tabaci were M. micrantha, M. charantia, and Malvastrum sp. The treatments that best controlled B. tabaci when populations were low were: (T3) Azibenzolar-S Methyl + Thiamethoxam, (T4) Thiamethoxam, and (T5) the rotation of Abamectin, B. thuringiensis, Imidacloprid and Spinetoram. For T. palmi, the most effective treatment was (T4). When B. tabaci populations were high, the treatment (T5), the rotation of Abamectin, B. thuringiensis, Imidacloprid, Bifenthrin, and Spinetoram, was the most effective. The cultivars that showed the lowest incidence of B. tabaci and A. gossypii were: Crimson Sweet, Estrella, and River Side.Publication Seismic assessment of Informal reinforced concrete houses in Puerto Rico(2025-05-13)The 2020 Puerto Rico earthquake sequence revealed the seismic vulnerability of informal two-story reinforced concrete (RC) houses on the island. This research aims to evaluate the seismic performance of these structures and the effectiveness of strengthening measures by adding of RC shear walls on the first floor. A series of non-linear static and dynamic analyses were performed using fiber-based distributed plasticity to model the RC frame. The masonry walls, typically found only on the second floor, were modeled with non-linear macro elements to capture the added stiffness on this level. The seismic input for the nonlinear bi-directional analyses consisted of spectrally matched records that preserve the characteristics of near-fault pulse-like motions. The results show that, in the as-built condition, the stiffness mismatch between the two floors, combined with the significant strength and stiffness differences between the main axes of the structure, led to an undesirable concentration of plastic deformations on the first floor. This caused a displacement-driven failure mechanism along the weak axis, in line with field observations from the 2020 earthquake sequence. Incorporating shear walls on the first floor (with a wall index of 2.5% for the models with three axes per direction and 2.2% for the models with four axes per direction) greatly enhanced structural performance, doubling lateral load capacity and increasing overall stiffness. However, the retrofitted structures still demonstrated an undesirable concentration of inelastic action, although it shifted to the second floor, suggesting room for further improvement. Future research could explore the use of shear walls that extend through the second floor to achieve a more uniform distribution of inelastic deformations.Publication Vertical, spatial, and temporal variability in seawater chemistry across the coral reefs of Puerto Rico(2025-05-09)Global coral reef declines, driven by climate change and local human impacts, make it critical to assess environmental variability to improve projections for future declines. Here, we sampled surface and bottom seawater chemistry across 42 coral reef sites (5-30 meters) around Puerto Rico quarterly in 2024 to quantify spatial and temporal trends in vertical chemistry differences. Mean vertical differences were minimal for all parameters: temperature = 0.33 ºC, salinity = 0.23 g kg-1, density = 0.28 kg m-3, biological oxygen demand = 0.44 mg L-1, dissolved oxygen = 0.37 mg L-1, pH = 0.02, total alkalinity = 13.3 µmol kg-1, dissolved inorganic carbon = 10.2 µmol kg-1, and saturation state with respect to aragonite (Ωarg) = 0.15. However, there was considerable variability with much larger vertical differences observed at some sites for selected sampling events. While vertical differences in physical parameters significantly correlated with depth for temperature (0.008 ± 0.002 °C per m, p < 0.001), salinity (-0.005 ± 0.002 g kg-1 per m, p = 0.002), and density (-0.011 ± 0.001 kg m-³ per m, p < 0.001), vertical differences in biogeochemical parameters lacked consistent trends with depth (p > 0.05) primarily due to offsetting positive and negative metabolic effects. The relationship between normalized total alkalinity and dissolved inorganic carbon revealed a balance between organic and inorganic carbon cycling and suggested net calcification relative to offshore data. This three-dimensional assessment highlights the complex biogeochemical dynamics of shallow coral reefs and underscores the importance of integrated monitoring strategies to better predict site-specific responses to environmental change.Publication A DoE approach to wearable biosensor design and machine learning for sweat sample analysis and monitoring(2025-05-12)This thesis addresses the need for improved tools to monitor L-Histidine. This amino acid plays a key role in histamine production, a biomarker in allergic reactions. The present work focuses on the technological development of a wearable label-free biosensor enhanced by machine learning for data analysis. In this work, laser-scribed graphene (LSG) electrodes were manufactured and characterized using Design of Experiments (DoE). The LSG electrode manufacturing process was optimized, and the electrodes were integrated into a microfluidic flow cell. The LSG electrodes, which served as sensors, were activated through cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). Following this, experimental data related to different L-Histidine concentrations were acquired using CV, providing the input for the machine learning platform. The platform's ability to detect L-Histidine was improved using Machine learning algorithms, including Multi-Layer Perceptron Neural Network (MLP-NN), Support Vector Machines (SVM), and Random Forests (RF). These algorithms were used to analyze the electrochemical data. The results demonstrated the successful development of an LSG-based electrochemical platform for label-free L-Histidine detection. The platform exhibited promising analytical capabilities, with machine learning models achieving high classification accuracy. This research contributes to developing wearable sensing technologies for potential applications in allergy-related studies.
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