Current Search:  Electronic Theses & Dissertations (x) » Gambierdiscus (x)

View All Items

  • CSV Spreadsheet
(1 - 4 of 4)
ABIOTIC INFLUENCES ON AND COMMUNITY DYNAMICS OF BENTHIC DINOFLAGELLATE SPECIES IN THE FLORIDA KEYS
Title
ABIOTIC INFLUENCES ON AND COMMUNITY DYNAMICS OF BENTHIC DINOFLAGELLATE SPECIES IN THE FLORIDA KEYS.
Creator
Schroeder, Jessica Elizabeth
Abstract / Description
Gambierdiscus is an epibenthic dinoflagellate genus containing some species that produce a toxin (ciguatoxin), which causes Ciguatera Fish Poisoning (CFP). These dinoflagellates live on macrophytes that are consumed by herbivorous fish and invertebrates, thereby introducing ciguatoxin into the reef food web through bioaccumulation and biomagnification processes. Such grazers are later predated on by larger fish, which when consumed by people, can lead to CFP. Other dinoflagellates coexist...
Show moreGambierdiscus is an epibenthic dinoflagellate genus containing some species that produce a toxin (ciguatoxin), which causes Ciguatera Fish Poisoning (CFP). These dinoflagellates live on macrophytes that are consumed by herbivorous fish and invertebrates, thereby introducing ciguatoxin into the reef food web through bioaccumulation and biomagnification processes. Such grazers are later predated on by larger fish, which when consumed by people, can lead to CFP. Other dinoflagellates coexist with Gambierdiscus spp., including potentially toxigenic Prorocentrum and Ostreopsis spp. The research presented here focuses on the community ecology of Gambierdiscus spp. and these other dinoflagellates, and the abiotic factors that affect their distribution, abundance, and compositions. New findings in this project have provided information about community dynamics and the influence of abiotic factors. The data suggest that physical and chemical parameters influence dinoflagellate densities and the differences in site community composition. These epibenthic dinoflagellates thrive in high temperatures but may compete in other environmental conditions. The three dinoflagellates were more abundant in the Florida Bay than Atlantic Ocean sites. The three dinoflagellates coexist, but there were no differences in abundances seasonally and between sites, suggesting subtle niche partitioning may be taking place.
Show less
Date Issued
2020-05-27
Identifier
fgcu_ETD_0337
Format
Document (PDF)
CIGUATERA IN FLORIDA KEYS PATCH REEFS: BIOGEOGRAPHIC INDICATORS OF GAMBIERDISCUS DENSITY AND TEMPORAL ABUNDANCE (CFP:BIG DATA)
Title
CIGUATERA IN FLORIDA KEYS PATCH REEFS: BIOGEOGRAPHIC INDICATORS OF GAMBIERDISCUS DENSITY AND TEMPORAL ABUNDANCE (CFP:BIG DATA).
Creator
Hian, Meghan
Abstract / Description
Ciguatera fish poisoning (CFP) is a global public health concern that is associated with Gambierdiscus, a genus of harmful algae found in coral reef environments that includes species known to produce toxins (ciguatoxins). Outbreaks of CFP have often been linked to elevated abundance of Gambierdiscus cells and disturbance-related degradation of coral reefs. However, the influence of human activities on CFP risk, both directly and indirectly within the broader context of reef health, has yet...
Show moreCiguatera fish poisoning (CFP) is a global public health concern that is associated with Gambierdiscus, a genus of harmful algae found in coral reef environments that includes species known to produce toxins (ciguatoxins). Outbreaks of CFP have often been linked to elevated abundance of Gambierdiscus cells and disturbance-related degradation of coral reefs. However, the influence of human activities on CFP risk, both directly and indirectly within the broader context of reef health, has yet to be defined for highly exploited patch reefs in the Florida Keys. The objectives of this study were to define spatial and temporal patterns in reef health and Gambierdiscus abundance across the three regions (Upper, Middle, Lower), to determine whether the drivers of those patterns were natural or anthropogenic, and to identify biogeographic indicators of risk. To address these objectives, this study combined field sampling with a “big data” approach to spatial analysis. Six patch reefs (two per each of three regions) were selected as study sites from existing research stations. Datasets from long-term monitoring of benthic cover, fish species abundance, land use, and water quality were compiled and analyzed in ArcGIS to characterize the ecological context of each site. Analysis of samples of host macroalgae collected from all study sites biannually revealed that Gambierdiscus cell densities were consistently highest in the Upper Keys and lowest in the Middle Keys, regardless of season. Conversely, reef health was lowest in the Upper Keys and improved along a gradient to the Lower Keys. Multivariate analysis of site similarity indicated that this regional pattern was driven more strongly by grazing than substrate availability. Additionally, there is evidence that human activities have an indirect influence on CFP risk through reef health, as well as through overfishing, and the destruction of inshore habitats like seagrass and mangroves. Due to a strong positive correlation with cell densities, this study suggests that mangrove cover could be useful as a biogeographic indicator of potential CFP risk. Whereas surgeonfish, with a strong negative correlation with cell densities, could indicate the actual flow of toxins into higher trophic levels. The concordance of high regional risk and high population density necessitates continued monitoring of fish in those areas and the development of more comprehensive predictor of potential CFP outbreaks.
Show less
Date Issued
2018-08-22
Identifier
fgcu_ETD_0258
Format
Document (PDF)
Effects of macroalgal hosts on the growth and epiphytic behavior of five Gambierdiscus species from the greater Caribbean region
Title
Effects of macroalgal hosts on the growth and epiphytic behavior of five Gambierdiscus species from the greater Caribbean region.
Creator
Rains, Lacey Kay
Abstract / Description
Ciguatera fish poisoning is caused by toxins produced by dinoflagellates of the genus Gambierdiscus. This genus has recently been revised and new research on the physiology and ecology of the revised species is needed. While it has been demonstrated that Gambierdiscus spp. are predominately epiphytic, there is also evidence that they are conditional, not obligate, epiphytes and that not all algae hosts are preferred equally by Gambierdiscus populations. This experiment exposed five Caribbean...
Show moreCiguatera fish poisoning is caused by toxins produced by dinoflagellates of the genus Gambierdiscus. This genus has recently been revised and new research on the physiology and ecology of the revised species is needed. While it has been demonstrated that Gambierdiscus spp. are predominately epiphytic, there is also evidence that they are conditional, not obligate, epiphytes and that not all algae hosts are preferred equally by Gambierdiscus populations. This experiment exposed five Caribbean species of Gambierdiscus to living conditions among 8 different species of macroalgal hosts, and their epiphytic behavior (attachment vs. non-attachment) and growth were monitored over 29 days. Additionally, the experiment was carried out under two separate nutrient conditions, ambient versus enriched Florida Keys seawater. Results demonstrate variable responses in epiphytic behavior within the Gambierdiscus genus to different macroalgal hosts, and stimulation and/or inhibition of Gambierdiscus growth by different macroalgal hosts. Attachment data indicate that Gambierdiscus populations prefer attachment to hosts that have a filamentous structure, but those species did not always support high cell abundances. Certain algal host species appear to stimulate growth of some Gambierdiscus species while others seem to inhibit the growth of other species. Control treatments (no host) reveal that some Gambierdiscus reached higher cell abundances without the presence of any host algae, suggesting inhibition by the hosts. No overall attachment preference was observed among Rhodophytes, Chlorophytes, and Phaeophytes, and no phyla stimulated growth or cell abundance more than the others. There was also no difference in attachment to hosts that were nutrient-enriched versus those that were not. The variability of growth responses and attachment behavior to different hosts by the various Gambierdiscus species in this experiment add complexity to our understanding of the epiphytic nature of Gambierdiscus and the dynamics of blooms.
Show less
Date Issued
2015
Identifier
Rains_fgcu_1743_10144
Format
Document (PDF)
Nutritional and Photophysiological Approaches to Identifying the Niche of Gambierdiscus: Insight into the Ecology of Ciguatera Fish Poisoning
Title
Nutritional and Photophysiological Approaches to Identifying the Niche of Gambierdiscus: Insight into the Ecology of Ciguatera Fish Poisoning.
Creator
Leynse, Alexander Kenneth
Abstract / Description
seafood consumption in the world. CFP is a global issue with an estimated tens of thousands of fish poisonings per year along with an estimated annual economic impact of $21.19 million in the United States alone. The toxins that cause CFP are produced by tropical benthic dinoflagellates belonging to the genus Gambierdiscus. Understanding the species-specific ecophysiology of these dinoflagellates is crucial to the understanding and potential forecasting of CFP outbreaks. Currently, there are...
Show moreseafood consumption in the world. CFP is a global issue with an estimated tens of thousands of fish poisonings per year along with an estimated annual economic impact of $21.19 million in the United States alone. The toxins that cause CFP are produced by tropical benthic dinoflagellates belonging to the genus Gambierdiscus. Understanding the species-specific ecophysiology of these dinoflagellates is crucial to the understanding and potential forecasting of CFP outbreaks. Currently, there are knowledge gaps in understanding the role that the nutritional and photo-physiology of Gambierdiscus play in the ecology of CFP. This research focused on the nutrient uptake kinetics as well as the photoacclimation and photoprotection of two distantly related species of Gambierdiscus. The results revealed that both species utilize a unique nutritional strategy that allows them to be competitive for nutrients among the benthos of tropical oligotrophic environments. In regards to cellular and photochemical responses, the two observed species appear to cope with varying light intensities in very different ways. However, both species appear to be adapted for typical light intensities found in tropical benthic environments and exhibit both cellular and photochemical strategies for coping with exposure to irradiances above those which are desired. Together, these results reveal a new life history strategy previously unreported for single-celled algae. The unique adaptations discovered allow these dinoflagellates to be competitive in tropical benthic environments despite a nutrient-deplete water column and exposure to a wide range of light intensities.
Show less
Date Issued
2016
Identifier
Leynse_fgcu_1743_10187
Format
Document (PDF)