Marine Science Senior Theses 2011
Neurological and Developmental Affects of Triclosan and Chlorpyrifos Exposure on Zebrafish (Danio rerio) and Caenorhabditis elegans
Student: Thomas W. K. Battey
Thesis Committee: Denise Flaherty (chair), Jonathan Cohen, Greg Gerdeman
Triclosan is a pervasive anti-microbial agent in modern personal care and cleaning products. The Environmental Protection Agency (EPA) describes the environmental fate of triclosan as “uncertain,” estimating that approximately 90% of all surfaces have come into contact with triclosan. Triclosan has been shown to affect embryonic viability, pigmentation, and otolith development, as well as survivability, in zebrafish. Chlorpyrifos, prevalent in agriculture, has been shown to inhibit acetylcholinesterase and affect the development of swimming behavior in zebrafish. As ubiquitous as triclosan, the EPA estimates that chlorpyrifos is “one of the most widely used organophosphate insecticides,” and enters natural waterways via runoff. Thus, it is important to understand the impact of compounds like triclosan and chlorpyrifos on the environment. Here, the developmental effects of triclosan were assessed using the zebrafish (Danio rerio), and the developmental and physiological effects of triclosan and chlorpyrifos alone and in mixture were assessed using the nematode Caenorhabditis elegans as a model organism. Zebrafish developmental effects were quantified using a deformity score from zero to five for overall development, and zero to three for otolith malformations. Triclosan exposure results in delayed overall development, pericardial edema, spine malformations, otolith deformities, and complete mortality after 36 hours in concentrations as low as 0.5 ppt. Overall and otolith deformity increased significantly in a dose-dependent manner. Zebrafish embryos exposed to triclosan also exhibited a decrease in heart rate at 0.3 and 0.5 ppt. Developmental and physiological effects of triclosan and chlorpyrifos exposure in C. elegans were quantified using a beats-per-minute (BPM) assay to assess cholinergic function, a tap-withdrawal test to assess glutamatergic and GABA-ergic function, and progeny analyses to assess reproductive function. Animals exposed to triclosan exhibited significantly decreased mean BPM across all treatment groups, but did not show a significant change in fecundity. Chlorpyrifos exposure resulted in significantly increased mean BPM at lower concentrations, a significant decrease at higher concentration, and no significant change in fecundity. Animals exposed to triclosan and chlorpyrifos in mixture did not develop to adulthood in higher concentrations, exhibited a significant decrease in mean BPM, and showed a decrease in fecundity in the mixture with highest triclosan and chlorpyrifos concentration. Using data from two well-described model organisms, this study will provide insight into the role that these persistent anthropogenic chemicals play in the environment at large.
Reverse Engineering and Modification of a Gamma Scan System: A Unique, High Precision, Non-Destructive Technique to Obtain mm-Scale Resolution for Radiometric Dating of Sediments
Student: Trevor Browning
Thesis Committee: Gregg Brooks (chair), David Duncan, Charles Holmes
Initially developed by the NOAA Great Lakes Laboratory in 1988, the “Gamma Scan System” (GSS) was a collection of instruments that could scan samples for radioactivity. From 1988 until 1995, the instrument was perfected and given full automatic locomotion so that it could non-destructively scan samples and operate completely on its own. The instrument was gifted to Eckerd College in 2006: however, it has not been in working condition since 1995. This study was conducted to rebuild and modify the GSS for geologic use. This had to be accomplished through “reverse engineering,” due to the lack of written instructions. The GSS consists of a platform, or carriage, that moves vertically as well as horizontally. When fully operational there will be either a sodium iodide detector or a germanium detector on the platform scanning for gamma emissions. The signal from the detector is run through a series of pulse analyzing instruments, before reaching a computer, which generates a spectrum of energies for a variety of radioisotopes. The beauty of this instrument is that it can scan multiple samples with high resolution and excellent precision, without any human interaction. Designed by a physicist and only the second of its kind in the world, it was originally used for bioturbation studies on worms. I have modified the instrument for use as a non-destructive technique for sub millimeter-scale sampling of sediment cores. Presently the device has full locomotion capabilities, but it is still a work in progress to get the radioactive scanning online.
An evaluation of eye adaptations in relation to aerial predatory behaviors of the puffer Sphoeroides rosenblatti and the killifish Oxyzygonectes dovii
Student: Rachel Harbeitner
Thesis Committee: Bill Szelistowski and Jon Cohen (co-chairs), Greg Gerdeman
Teleosts possess morphological adaptations that reflect their behaviors and environments they utilize. Predation at and above the air-water interface requires fish to utilize the aerial environment, and ocular morphology has evolved to support this predatory behavior in species that feed primarily above water. To determine if two subsurface feeders, Pacific puffer Sphoeroides rosenblatti and white-eyed killifish Oxyzygonectes dovii, that peripherally use the aerial environment to feed, also have ocular adaptations that adapt them to changes in light and brightness above the water surface. Their predatory behaviors were observed and the ocular features were measured, including lens radius of curvature, corneal epithelium thickness, corneal stroma thickness, lens thickness, cornea to lens distance and lens to retina distance. Values for these fish were compared to those for spotted puffer Guentheridia formosa and striped killifish Fundulus majalis, as these are related species that are known subsurface inhabitants. The predatory jumping behavior was described in detail for S. rosenblatti, but feeding was not observed in O. dovii. There were no significant adaptations to terrestrialization found in the eyes of either species, though results suggest similarities to those for other species that use aerial predation to supplement a primarily aquatic diet.
The Analysis of Wetland Sediment in an Artificial Environment Using Pb-210 and Th-234 Techniques; Terra Ceia, FL
Student: Jamie Lowry
Thesis Committee: Gregg Brooks (chair), David Duncan, Paul Hindsley
Terra Ceia Preserve State Park, FL is filled with uplands, islands, lakes, karst terrain, and wetlands. It is located on the west coast of central Florida near Tampa Bay. This study is on an artificial wetland area that began construction in 2007 and was completed nearly 2 years ago. The site was previously a farming area that grew fallow and covered with invasive species. This reading compares this artificial depositional environment to a natural wetland including; stratigraphy, sediment analysis, and development through comparing depositional rates. It was found that groundwater and dilution may be a factor in determining the correct ages of the sediments, but stratigraphy shows patterns related to natural wetland environments. This artificial wetland creates a unique record that does not exactly show the events during its construction.
Home Range Modeling of Resident Bottlenose Dolphins (Tursiops truncatus) in Boca Ciega and Tampa Bays, Florida
Student: Kimberly McCallister
Thesis Committee: Shannon Gowans (chair), Elizabeth Forys, Randall S. Wells
Home ranges of three resident common bottlenose dolphins (Tursiops truncatus) were studied in Boca Ciega and Tampa Bays, southwest Florida. Boat-based photo identification surveys were conducted with the Eckerd College Dolphin project from June 1993 to July 2010 in approximately 406 km2 of inshore and coastal waters. From a total of 722 catalogued individuals, three females were selected for home range analysis. Only individuals with 100 or more sightings were selected for home range analysis, as earlier studies on bottlenose dolphins indicated that using fewer sightings tended to underestimate home range size. Each of these females had more than 100 sightings over the 18 year study; no males met these requirements. The three females were CUPD (106 sightings between 1997 and 2010), DMBK (105 sightings between 1988 and 2010), and HAMR (134 sightings between 1993 and 2010). Sighting data for these individuals prior to 1993 was obtained from the Sarasota Dolphin Research Project catalogue.
Sightings were plotted and analyzed with Geographic Information System software (ArcGIS), using the ‘Home Range Tools’ extension to perform 100% minimum convex polygon (MCP) and 95% fixed kernel density (FKD) estimations of home range area. MCP estimates ranged from 57.1- 107 km2 with large, polygon models likely influenced by outliers, while FKD estimates ranged from 21.5-42.2 km2, with smaller more amoeboid shaped models biased toward boat channels and core areas concentrated within 20-25% of total individual home range as determined by the FKD method. Area-observation curves supports FKD as the more confident method of home range analysis, with large samples size, and suggest a minimum of 50-60 sightings are necessary for accurate home range size definition in Boca Ciega and Tampa Bay areas. However, MCP remains a valuable tool for assessing short term field studies or small subsets of long term data which are limited to small sample sizes. Total home range area for each female was compared to her range during years with a documented young of the year, and overlap suggests there are multiple areas that may function as nursery areas in our local waters, with future increased sample sizes necessary to determine these relationships.
Vision in the fast lane: examining the pupillary response and spectral responsivity in the Atlantic brief squid, Lolliguncula brevis
Student: Lillian McCormick
Thesis Committee: Jonathan Cohen (chair), Joel Thompson, William Szelistowski
Cephalopods (Mollusca), especially the members of Coleoidea, show advanced visual systems, presumably developed as an adaptation for the increased speed and activity after the loss of the characteristic Molluscan protective shell. The highly visual nature of Coleoid predation requires an advanced eye capable of accuracy and focus in rapid environmental changes, possibly from adaptations such as a sensitive pupil, a consensual response between eyes, and specific visual pigments. One aspect of the visual system in which there are no behavioral studies is the pupillary response of Teuthids, such as the Atlantic brief squid, Lolliguncula brevis, which lives in estuarine or coastal environments. The response was analyzed by exposing an individual to alternating treatments of varying light intensities and periods of dark recovery, while simultaneously recording the eye under direct stimulation (facing the light) and the eye under indirect stimulation (opposite the light stimulus), in part to determine whether the response was consensual between eyes. The spectral responsivity of L. brevis was analyzed by measuring the magnitude of the pupillary response of an eye directly stimulated by light at equal quantal intensities at wavelengths through the visible spectrum and compared with environmental light data.
A light-induced pupillary response was measured in the majority of the eye parameters analyzed, with an asymmetrical constriction observed under increasing irradiance levels that was largely consensual between eyes. The spectral responsivity of the rhodopsin showed a behavioral maximum measured at 500 nm, which was fit with a rhodopsin absorbance template having a λmax of 511 nm. These results show the sensory adaptation of L. brevis to a coastal environment, with a visual system designed for acuity during dusk, when there are rapid changes in irradiance and a peak absorbance of blue-green light (~500 nm). Additional methods of maintaining the visual capability in its given environment may be inferred, such as the presence of a screening pigment and/or behavioral adaptations such as vertical migration in the water column.
Photographic Identification of West Florida Shelf Bottlenose Dolphins Tursiops truncatus
Student: Grace Olson
Thesis Committee: Shannon Gowans (chair), Randall Wells, Peter Simard
The method of photographic identification for marine mammals has been an effective way to identify individuals and monitor movement and distribution. Little information is known about bottlenose dolphins that are found in the offshore "gulf" region of the West Florida Shelf. From 2008 through 2010 the Dolphin Ecology Vocalization and Oceanography Project at the University of South Florida conducted 23 days of field research over the West Florida Shelf in the Gulf of Mexico. Photographic identification data was collected of bottlenose dolphins, Tursiops truncatus, resulting in 6920 photographs. For each field day, the photographs were graded for photograph quality (5=excellent quality, 1=not identifiable) and dorsal fin distinctiveness (1=very distinct markings, 3=subtle marks). The photographs of sufficient quality (>4) and distinctive features (1 or 2) were examined by eye to identify individuals, which were assigned a temporary identification. A total of 126 individual were observed and identified. Of these 126 dolphins, 63 were found to be easily identifiable and were imported into the software program DARWIN (Digital Analysis and Recognition of Whale Images on a Network) to create a new West Florida Shelf bottlenose dolphin catalog. This program was designed at Eckerd College to assist in the analysis and matching of dolphin dorsal fins. Each identified photo was added individually to the program and compared to the existing dolphins in the catalog to verify any re-sights of individuals. One dolphin re-sight was recorded, where an individual was sighted on July 21, 2008 and approximately 95 kilometers away on July 23, 2008. A freeze branded individual from the Sarasota Dolphin Research Program was also identified just outside of Sarasota Bay. Future work will compare the catalog of the dolphins identified in this study that were found in "gulf" region of the West Florida Shelf to pre-existing catalogs such as the Eckerd College Dolphin Project (ECDP) catalog and the Sarasota Dolphin Research Program catalog.
Thesis Committee: Jonathan Cohen (chair), William Szelistowski, David Hastings
Pagurus maclaughlinae is a small hermit crab species living in seagrass beds ranging from Georgia to coastal Mexico. The species feeds on seagrass epiphytes and may be an important contributor to seagrass bed ecology. Little is known about this hermit crab, particularly its sensory biology. The purpose of this study was to determine whether P. maclaughlinae exhibits chemically mediated rheotaxis in the presence of chemical odors from ecologically relevant sources. Responses of individual P. maclaughlinae exposed to prepared odor treatments from Syringodium filiforme, Callinectes sapidus, Nassarius vibex, and a neutral/basic tripeptide were recorded in a laboratory flow tube. Water flow rates and odor concentrations were varied for each treatment, and the presence or lack of a shell was also investigated in a subset of odor/flow treatments. The data suggest that shelled P. maclaughlinae exhibit chemically mediated rheotaxis in the presence of a predator odor (C. sapidus), and did not respond significantly to any other odor used in this study. Shell-less individuals may exhibit reduced locomotion in the presence of a predator odor, though these results were not significant. Individuals tested in the high flow rates responded significantly when exposed to C. sapidus odor, but flow rate did not otherwise effect results. Flow rate was a significant factor for P. maclaughlinae exposed to C. sapidus odor, but did not significantly effect other results.
Population genetics of Gulf Pipefish, Syngnathus scovelli, along the southeast coast of Florida
Student: Nathan W. Van Bibber
Thesis Committee: Bill Szelistowski (chair), Steve Denison, David Duncan
Previous study has shown that two populations of the Gulf pipefish, Syngnathus scovelli are strongly divided by a barrier to gene flow along the southeast coast of Florida. This study aimed to characterize, on a finer regional scale, the genetic changes within the mitochondrial control region of Gulf pipefish along the stretch where the barrier is located. A total of 155 new fish were collected from 6 new locations along the southeast coast (Islamorada, Barnes Sound, Biscayne Bay, Miami, Lake Worth, and Jupiter Inlet) and sequenced for the mtDNA control region. These were aligned with 221 fish from eight locations (Pensacola, Apalachicola Bay, Tampa Bay, Charlotte Harbor, Long Key, Fort Pierce, Merritt Island, and St. John's River) previously sampled by Storer et al. (in prep.). Analysis of the 376 total sequences revealed 79 haplotypes differing among 39 polymorphic loci. Haplotype diversity (h = 0.9033±0.014) and nucleotide diversity (% π = 0.724±0.028) were high for all locations, but varied within each location with the southeast locations having much greater haplotype and nucleotide diversities than the other locations. Most locations were genetically differentiated though molecular variances, and PCA revealed some genetic separation among three groups: Gulf (Pensacola, Apalachicola Bay, Tampa Bay, and Charlotte Harbor), southeast (Islamorada, Barnes Sound, Biscayne Bay, and Miami), and Atlantic (Lake Worth, and Jupiter Inlet, Fort Pierce, Merritt Island, and St. John's River). Isolation by distance reveals a single generation dispersal distance of 3 km, which helps to explain the high genetic differentiation even between adjacent locations. Sexual selection and oceanographic patterns coupled with the Gulf pipefish's low dispersal ability best explain this lack of demographic mixing.