Ecology

In examining the intentional relationship between the conservationist and the shark in South Florida, this thesis considers the latter as both a scarce natural resource - caught up in what Clifford Geertz citing Weber referred to as "webs of significance" (Geertz 1973:5) - and as a reflection of dynamic human conceptions of nature : a meta shark. This complex relationship is described by interpretations of conservation discourse recorded through ethnographic interviews that demonstrate how these perceptions have been influenced by factors such as personal experiences, film and text, and broad changes in the relationship between humans and nature since the early days of the environmental movement. By linking these perceptual changes with changes in American shark conservation policy, this work not only explains a relationship between culture, perception, and policy, but also celebrates the emergence of a multispecies marine community.

Fire occurrences in the Everglades have increased since hydrologic alterations began, yet the vulnerability of Everglades peat to combustion during wildfires has yet to be determined. Natural fire regimes help maintain ecosystem functions and services and disruptions of natural disturbance regimes can have detrimental impacts, jeopardizing ecosystem health. Severe peat combustion can destroy native vegetation, alter microtopography, and release large amounts of stored carbon into the atmosphere. To create a better understanding of the mechanistic controls on Everglades ground fires, the soil's physical properties within several sites of Water Conservation Area 3 and how changes in water table affect these physical characteristics were determined. Areas disturbed by hydrologic alterations contain higher mineral content and therefore require lower water content to combust when compared to preserved regions. Changes in water tables have a significant effect on soil moisture and lower water tables drastically increase the vulnerability of a region.

Pelagic Sargassum was used to determine the effects of habitat architecture for one species of shrimp (Leander tenuicornis) and two species of fish (Stephanolepis hispidus and Histrio histrio). Inter-thallus spacing (low, medium, and high) and depth (shallow versus deep) were manipulated independently to test whether the spatial components of habitat architecture. Two differing habitats (Sargassum versus seagrass species) were tested for the structural component of habitat architecture. There were no significant results for inter-thallus spacing experiments for L. tenuicornis and S. hispidus. H histrio selected habitats with medium inter-thallus spacing in two treatments. Large individual H. histrio contributed mostly to the significant effects. All three species selected habitats with a greater depth aspect. Finally, L. tenuicornis and H. histrio selected habitats with greater structural complexity (i.e., Sargassum). These results demonstrate clearly that habitat architecture of Sargassum influences habitat selection by these shrimp and fishes.

The Sargassum community consists of a unique and idverse assemblage of fauna critical to pelagic food chains. Associated organisms presumably have adaptations to assist in finding Sargassum. This study investigated cues used for habitat location and selection by the Sargassum crab, Portunus sayi. Chemical detection trials were conducted with a two-chamber choice apparatus with Sargassum spp. and Thalassia testudinum as source odors. Visual detection trials (devoid of chemical cues) and habitat selection trials were conducted in which crabs were given a choice of habitats. Results showed that P. sayi respoded to chemical odors from Sargassum spp. Crabs visually located habitats but did not visually distinguish between different habitats. In habitat selection trials, crabs selected Sargassum spp. over artificial Sargassum and T. testudinum. These results suggest that crabs isolated from Sargassum likely use chemoreception from longer distances ; within visual proximity of a potential patch, crabs use both chemical and visual information.

Fish predation can have structuring effects in aquatic communities, but the most important fish predators are not always immediately obvious. Generalist fish predators often occupy similar habitats and consume similar prey making determination of their consumptive impacts difficult. Understanding these consumptive impacts is important for understanding complex wetland food webs. I collected warmouth (Lepomis gulosus), bluespotted sunfish (Enneacanthus gloriosus), and dollar sunfish (Lepomis marginatus) in two seasons from sloughs for both diet and bioenergetics analysis. Macroinvertebrates dominated diets of the three species, and nonparametric analyses revealed evidence of diet ontogeny in warmouth and potential competition for prey items among gape-matched individuals. Bioenergetics modeling revealed high levels of macroinvertebrate comsumption by these species relative to macroinvertebrate reproductive output suggesting that when combined with other sources of mortality, consumptive pressures placed by sunfish on benthic macroinvertebrates may be quite large.

Current research in natural products has heavily focused on the identification of potent biologically active compounds, specifically for drug development. The project detailed in this thesis focuses on the extraction of compounds from marine invertebrates as well as defining the absolute configuration for a compound. Utilizing marine invertebrates, the sonications method developed in this thesis provides an alternative approach to rapidly extract compounds for primary screening. This method is viable compared to a traditional overnight extraction method, without suffering compound degredation... Previously, clathric acid was isolated from an unknown Clathria sp. This compound is a bibyblic C-21 terpenoid shown to have mild antimicrobial activity against gram positive bacteria. With only its relative configuration established, additional amounts of clathric acid were required to define the overall absolute configuration. Identifying the Clathria sp. to be Clathria compressa, through spicule analysis, additional sponge tissues were then collected off the coast of Boca Raton, Florida to isolate additional quatities of clathric acid. The absolulte configuration was determined through circular dichroism and the octant rule to establish a final configuration for clathric acid's four carbon stereocenters to be: (3S, 7S, 8R, and 12S).

The largemouth bass (Micropterus salmoides) fishery was at an all time low on Lake Okeechobee when experimental supplemental stockings were done to try and enhance local bass populations. Largemouth bass had never been stocked on a large lake like Lake Okeechobee. The objectives were to develop a methodology, study dispersal, and compare stocked versus wild bass habitat choices. The methodology underwent considerable changes between studies. Bass dispersed to the edges by the second sampling period, so a larger sampling area may be needed. Water depth and pH were found to be significantly different between wild and stocked bass. Hatchery bass are naèive about predators, which may have resulted in stocked bass not moving to shallower areas like wild bass. The pH was weakly correlated with depth, so differences may be partially due to the fact that as depth increases, pH may also increase.

Two sympatric dolphin species, Stenella frontalis and Tursiops truncatus, resident to Little Bahama Bank, Bahamas were found to mostly forage independent of one another, but occasionally foraged in mixed groups. Analysis of over 20 years of data revealed the degree of overlap to be minimal with spatially distinct regions identified for both species, environmental segregation based on depth, bottom type, temperature, and time of day. Results based on observational data indicated significant differences in group size and selected prey. For S. frontalis, lactating females had the most distinct diet, which differed from that of non-reproductively active (NRA) females. Pregnant females had ambiguous prey use results, but diet differences were revealed through nutritional analysis. Lactating females had a higher intake of all nutrients (% moisture, % lipid, % protein, and calories) than pregnant females but lower than NRA females. Mother and calf pairs selected prey for caloric and moisture values. The influence of calves on foraging groups was reflected through discrete differences in all nutrients. Males and females appeared to select the same major prey, but female prey use was much more diverse.

Although most batoids (skates and rays) are benthic, only the skates (Rajidae) have been described as performing benthic locomotion, termed 'punting'. While keeping the rest of the body motionless, the skate's specialized pelvic fins are planted into the substrate and then retracted caudally, which thrusts the body forward. This may be advantageous for locating and feeding on prey, avoiding predators, and reducing energetic costs. By integrating kinematic, musculoskeletal, material properties, and compositional analyses across a range of morphologically and phylogenetically diverse batoids, this dissertation (i) demonstrates that punting is not confined to the skates, and (ii) provides reliable anatomical and mechanical predictors of punting ability. Batoids in this study performed true punting (employing only pelvic fins), or augmented punting (employing pectoral and pelvic fins). Despite the additional thrust from the pectoral fins, augmented punters failed to exceed the punting c apabilities of the true punters. True punters' pelvic fins had greater surface area and more specialized and robust musculature compared to the augmented punters' fins. The flexural stiffness of the main skeletal element used in punting, the propterygium, correlated with punting ability (3.37 x 10-5 - 1.80 x 10-4 Nm2). Variation was due to differences in mineral content (24.4-48-9% dry mass), and thus, material stiffness (140-2533 MPa), and second moment of area. The propterygium's radius-to-thickness ratio (mean = 5.52 +-0.441 SE) indicated that the propterygium would support true and augmented punters, but not non-punters, in an aquatic environment. All propterygia would fail on land. Geometric and linear morphometric analyses of 61 batoid pelvic girdles demonstrated that pelvic girdle shape can predict punting and swimming ability and taxonomic attribution to Order.

Trade-offs in traits conferring success in permanent and ephemeral habitats are often at odds with few species being able to persist in both types of environments. I examined the effect of sunfish predators on two species of south Florida crayfish to establish the mechanism that limits one species, Procambarus alleni, to short-hydroperiod environments. The crayfish assemblage response to a gradient of sunfish predators and the effect of predation on P. fallax alone was examined. I also examined the effects of sunfish on crayfish growth and quantified activity levels and risky behaviors of both crayfish species. P. alleni dominated at low sunfish densities but dominance shifted with increasing sunfish density. P. alleni was more active and likely to initiate risky behaviors, suggesting that sunfish predators remove the more active P. alleni, reducing their numbers disproportionally to those of P. fallax and allowing P. fallax to dominate crayfish assemblages in long-hydroperiod wetlands.