Search

Seagrass populations from two sites within Jobos Bay (Aguirre, Puerto Rico) have been monitored bi-annually (winter and summer) most years from 2019 - 2023. These monitoring sites were selected because of an initial dominance of the native seagrass, Thalassia testudinum (turtle grass). Each site has 20 quadrats each, with one site located adjacent to a basin mangrove forest and the other on the leeward side of a fringe mangrove forest. The invasive seagrass Halophila stipulaceae was initially at 23% cover at the basin site when first measured in 2019, but not at the fringe site. It first appeared at the fringe site in January 2021 and has continued to increase at both sites. Additionally, the shallower quadrats at the fringe site have experienced a noticeable decrease in T. testudinum cover since July of 2021. This decrease in T. testudinum could be a result of recent seasonal accumulation of floating brown algae, Sargassum spp., in the shallow areas of this site. The accumulation of this algae and the increased growth of the invasive seagrass are likely negatively impacting native seagrass and macroalgae populations throughout the Caribbean. The goal of this research is to estimate the role each biotic factor has in the fluctuation of native macrophytes in the region. [ABSTRACT FROM AUTHOR]

American alligators (Alligator mississppiensis) are apex predators who forage opportunistically for their prey. Within this diverse set of prey, they capture both mobile and immobile prey to survive. Little is known about how alligators modulate their prey capture as it relates to the mobility of their prey. This study investigated the modulation in feeding behavior of alligators when feeding on mobile versus immobile prey. Using six juvenile captive-reared individuals, feeding events were recorded for individuals feeding on both mobile and immobile fish prey using a high-speed video camera in a laboratory-controlled setting. Feeding performance was summarized by analyzing 4 kinematic feeding variables (maximum gape, duration of feeding event, approach velocity, and maximum gape velocity) for each feeding event. Results showed that none of the kinematic variables were significantly different between treatment groups, and that alligators fed equally well on mobile and immobile prey. This indicated that American alligators do not modulate their feeding behavior based on the mobility of the prey. Here, American alligators seem to utilize a static or constant form of prey capture behavior regarding the prey's mobility underwater. [ABSTRACT FROM AUTHOR]

Seagrass is a flowering plant found in tropical and sub-tropical marine systems and is common along the coasts of Florida, including Lake Worth Lagoon (LWL -- Palm Beach County, FL). Over the past 10 years, seagrass beds have been decreasing rapidly and as an indicator species its decline has brought to light other issues in the ecosystems, such as harmful algal blooms and declines in estuarine health. The goal of this study is to model potential patterns of environmental parameters and community structure that may correlate with the decline of seagrass populations in LWL over a 12-year period from 2007 to 2019. Nine transects throughout the LWL were visited annually (May -- August) and environmental parameters (e.g., temperature, dissolved oxygen, and salinity), seagrass Braun-Blanquet (BB) scores (a record of coverage), and macroalgal BB scores were recorded. A preliminary multivariate analysis of variance indicated significant differences in annual variability of environmental parameters within the LWL watershed over the 12-year period. Major drivers of the variability included changes in dissolved oxygen content, total nitrogen, total phosphate, salinity, and pH. An analysis of variance (ANOVA) investigating the annual variability in mean seagrass BB score showed an abrupt decline in 2013, with seagrass cover remaining very low throughout the rest of the dataset. A separate ANOVA conducted on the annual macroalgal BB scores displayed a similar pattern, with macroalgal coverage declining abruptly in 2013 and remaining low. Interestingly, initial analysis of this dataset suggests that abiotic, rather than biotic, factors may dictate the stability of seagrass communities in Lake Worth Lagoon. Continuing analyses include the development of models utilizing combinations of environmental parameters, community structure, temporal variables, and spatial variables that predict specific seagrass species' presence/absence and BB scores in this watershed, with those models being evaluated by Akaike Information Criterion. [ABSTRACT FROM AUTHOR]

The seagrass Thalassia testudinum is ecologically valuable serving as habitat and food for many organisms. There has been a documented decline in seagrass communities over the past decades and aspects of climate change are predicted to negatively impact seagrass growth. This study sought to understand how environmental variables influence T. testudinum communities in Jobos Bay, Puerto Rico. Forty 1 m² quadrats within transects in Jobos Bay were sampled. For each quadrat, percent cover (Braun-Blanquet (BB) score), density, and blade length of T, testudinum were recorded along with environmental parameters (depth, temperature, pH, DO, turbidity, and salinity). Additionally, growth rates of T. testudinum plants were measured within 12 (25 cm²) quadrats placed at different locations (less turbid and more turbid) and depths (1m and 2m). A Principle Component Analysis (PCA) characterized variation in environmental parameters and community structure for each quadrat. The PCA scores, along with site location and season were used to develop models to predict T. testudinum, BB score, blade length and density. The best explanatory models for predicting BB scores included depth, community structure, and location. As depth increased there was a marked decrease in BB score. The best performing models for blade length included the interaction between location and seagrass community structure, with length increasing as the prominence of the invasive seagrass, Halophila stipulaceae, increased. The global model (all variables included) was best at modeling density. For the growth study an ANOVA indicated significant differences in growth rate for depth and a significant interaction between location and depth. At the clearer location growth rates were greatest at 2 m but for the turbid location greater at 1 m. This research depicts the importance of understanding location variability on assessing the health and vitality of T. testudinum beds when considering estuary conservation strategies and seagrass loss mitigation. [ABSTRACT FROM AUTHOR]