A dual-station high frequency Wellen Radar (WERA), transmitting at 16.045 MHz, has been deployed along the Eastern Florida Shelf (EFS). From September 2004 to June 2005, a moored acoustic Doppler current profiler (ADCP) acquired subsurface current measurements within the radar footprint along the shelf break at 86-m depth. The shallowest ADCP bin located at 14-m depth is used as a comparison for the WERA surface measurements. The RMS differences range from 0.1 to 0.3 m s super -1 between the surface and 14-m depth, with good agreement over most of the period. Regression analyses indicate slopes near unity in the north-south (v-) component and approximately 0.5 for the east-west (u-) component velocities. Following validation of the HF radar surface current measurements, an assessment of the variability and character of eddies in the region is conducted for 2006. Optimal interpolation is utilized to create a uniform 45 km by 45 km grid of surface current data consisting of 1980 points in the inshore portion of the WERA domain. The Okubo-Weiss parameter is used to identify eddies as closed regions with values greater than a threshold of 2*10 super -8 s super -1. This method reveals a total of twenty-two eddy-like features over the year 2006. Given the asymmetric shape of the eddy regions, equivalent radii are computed as an estimate of eddy size with an annual average of 2.6 km. Eddy intensity is measured by maximum relative vorticity in the eddy region with an annual average of approximately 5f, where f is the local Coriolis parameter. Translational velocities are computed from the displacement of peak Okubo-Weiss parameter. This method tends to overestimate eddy speed given the shape-changing nature of the eddy regions. Nonetheless, the average translational velocity is 0.9 m s super -1 with a standard deviation of 0.4 m s super -1. Eddy tracks indicate a unique pattern in which eddies propagate inshore during the period of July to September and offshore during October to December related to position of the FC axis. The periodicity and spatial distribution of eddy events suggest that submesoscale eddy features are "wave-like" and centered along the strong topographical gradients between 200 to 600 m. By applying this methodology to other years of HF radar data, this statement can be tested with statistical confidence. In general, this study has shown the effectiveness of the Okubo-Weiss parameter in identifying eddy regions from a background field with large, ambient vorticity.

The observation of turbulence in the Florida Current is presented with the use of velocity measurements collected with an Acoustic Doppler Current Profiler (ADCP). The research is conducted through application of the theories of Taylor and Kolmogorov and related derivations, and processing tools of MATLAB software to this Eulerian observation of flow [1]. The velocity profile of the Florida Current is deduced in terms of its turbulent character with shear, acceleration, gradient, Reynolds Number, Reynolds Stress, Welch power spectrum density of current velocity, wavenumbers of Taylor’s hypothesis and Kolmogorov, wavenumber spectrum, eddy diameters, diapycnal diffusivity, and the Richardson Number. Processing methods are validated with results of other research conducted in the Florida Current with the use of a Multi-Scale Profiler, and an Advanced Microstructure Profiler for determination of shear, dissipation, diffusivity, and estimates of turbulent eddy diameters based on Taylor’s Hypothesis [1][4]. A spectral analysis is developed and is compared with Kolmogorov’s -5/3-Law. The process and the results of the analysis are described. / Includes bibliography. / Thesis (M.S.)--Florida Atlantic University, 2018. / FAU Electronic Theses and Dissertations Collection

Biological and physical sampling of a 10km long, east-west transect was performed during 2007, off the coast of southeast Florida. Temperature and salinity measurements were recorded using a conductivity-temperature-depth (CTD) sensor, and current direction and magnitude measurements were recorded using an acoustic Doppler current profiler (ADCP). Zooplankton samples were collected, during the daytime, using a Tucker multiple net mid-water trawl, with 760μm mesh, at intended depths of ~25m and ~200m, at three stations along the transect. Laboratory analysis indicated that several currents and water masses influenced the density distribution of calanoid copepods and chaetognaths. During April and September 2007, a Subsurface Counter Current existed in conjunction with an offshore meander of the Florida Current. Physical data confirmed the presence of Continental Edge Water and Yucatan Water occupying different spatial and temporal scales, and the boundary between these two water masses existed as the western boundary of the Florida Current. Temperature and salinity profiles confirmed that the Subsurface Counter Current was composed of Continental Edge Water and not Yucatan Water. Therefore, the Subsurface Counter Current observed during the transect was not a cross section of a passing eddy caused by the meandering front of the Florida Current. Densities of both taxa were highest in the Subsurface Counter Current and the Intermediate water, while the lowest densities are found in the Florida Current. Calanoid copepod and chaetognath densities exhibited typical zooplankton trends for tropical and subtropical coastal waters. Densities were highly influenced by the physical parameters of each month. Highest densities were observed in April and the lowest in July/September, typically the nutrient limited season. Analysis by location showed that the calanoid copepod and chaetognath densities were highest inshore and decreased offshore. The Florida Current exhibited the lowest densities for both taxa, while the Subsurface Counter Current and Intermediate water had higher densities. Previously documented southward flow had been associated with an offshore meander of the Florida Current, but during May and July there was a Subsurface Counter Current and an onshore meander of the Florida Current. Densities of both taxa were still lowest in the Florida Current. The stable isotope values of the zooplankton were skewed because of the preservation media and it was not possible to determine if the currents and water masses were isotopically different, and thus creation of a correction factor for the preservation effect was not possible. The δ13C values were variable in magnitude and direction from the control for each taxon. The δ15N values were less variable, but increased from the control, rather than decrease, as was expected for each taxon.

Zooplankton samples and water mass measurements were conducted along a 10 km long, east-west transect off the coast of southeast Florida during 2007. Temperature and salinity measurements were recorded using a conductivity-temperature-depth (CTD) sensor, and current direction and magnitude measurements were recorded using an acoustic Doppler current profiler (ADCP). Daylight zooplankton samples were collected using a 335 μm mesh bongo net at surface 0-25 m and 0-150 m (nearshore) and 0-200 m (offshore), at three stations, for 5 nonconsecutive months along the transect. Chaetognatha were separated from bulk zooplankton samples and identified to species; fifteen different species were found. Flaccisagitta enflata had the highest densities over the entire sampling period, followed by Serratosagitta serratodentata, and Krohnitta pacifica. ADCP data revealed the existence of a Subsurface Counter Current in conjunction with an offshore meander of the Florida Current during May, July, and September 2007. Abiotic data confirmed the presence of Continental Edge Water and Yucatan Water occupying different spatial and temporal scales, and the boundary between these two water masses existed as the western boundary of the Florida Current. The densities of each species were compared to the collection site’s temperature and salinity data. Densities of several species (Flaccisagitta enflata, Ferosagitta hispida, M. minima, and Sagitta bipuctata) demonstrated a correlation to temperature and S. bipunctata and Ferosagitta hispida showed a correlation to salinity. These species were associated with the front and peripheries of the Florida Current.

Copepods, minute crustaceans, are vital constituents of marine food web dynamics in tropical ecosystems. Ecologically, copepods provide the link between primary production and tertiary consumers. Changes in population structure and densities may impact ecosystem stability and production on small to large spatial scales. The present study examined the influence of the Florida Current on copepod population densities off the coast of Fort Lauderdale, Florida due to limited data in the area. Samples were collected during February and July 2007 at two locations, Stations A and B. Station A, dependent on current dynamics, fluctuated between the most western boundary and the inshore waters adjacent to the coast. Station B was typically located within the Florida Current showing great influence from the current’s physical factors. The current, acted as a physical barrier, entrapping species at near shore stations, increasing population densities by increased nutrient loads through upwelling and land runoff. The movement of the current inshore showed a greater resurgence of oceanic species at each station. However, the western edge of the current, acting as a barrier, yielded the lowest population densities overall and among all copepod orders. The decrease can influence food web dynamics and the prey availability to higher tertiary consumers. Population dynamics were ascertained by relative copepod densities identified to the lowest possible taxa and enumerated. Calanoid copepods were dominant in zooplankton samples, showing high instances of Calanus and Undinula, followed by Poecilostomatoida, highly represented by Corycaeus and Oncaea, and Cyclopoida. Poecilostomatoid densities were numerically important, where in some samples Corycaeus contributed to 42 % of overall copepod densities. Previous studies have led to their underestimation, due to gear selectivity and extrusion directly related to their prosome length. Diversity levels revealed an overall diverse habitat, typical of tropical environments. However, there was greater diversity in coastal waters as compared to the Florida Current which was only found oceanic species present.

A spiny (Palinuridae), slipper (Scyllaridae) and coral (Synaxidae) lobster larval composition and distribution study on the western edge of the Florida Current is presented. From the samples collected during 2007, phyllosoma larvae of Justitia longimanus, Panulirus argus, Parribacus spp., S. americanus, S. depressus and P. gundlachi were positively identified. Relative density catches of the phyllosoma larvae indicate that P. argus (Florida spiny lobster) is the most abundant species in the Straits of Florida. Data gathered during the study shows that P. argus larvae at different developmental stages occur throughout the year which supports the theory of multiple spawning and/or multiple sources. Larvae of genus Panulirus are difficult to distinguish from plankton samples and hence were identified as of P. argus since it is the most common species in the area. Family Palinuridae and Scyllaridae larval density spikes in July and May, coincide with their spawning peak periods of late March – early May and late January to late March respectively. Members of family Palinuridae showed higher densities at night, whereas those of family Scyllaridae showed higher densities during day catches. Larvae of all species showed close association between total length and developmental stage at earlier age. Variability in size and morphology within stage increases with older stages due to multiple molts and/or smaller sample size.