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An Examination of Grazing Preferences Exhibited by Herbivorous Invertebrates on the Common Macroalgal Hosts of Gambierdiscus
Title
An Examination of Grazing Preferences Exhibited by Herbivorous Invertebrates on the Common Macroalgal Hosts of Gambierdiscus.
Creator
James, Andrea Lynn
Abstract / Description
Understanding the basis of the marine food web is essential in determining the uptake and possible control of the toxins that cause ciguatera fish poisoning (CFP), predominantly ciguatoxins. Ciguatoxins are produced by the marine, epiphytic dinoflagellate Gambierdiscus, and when transferred through the food web via herbivory, have serious environmental and health implications. Ciguatera outbreaks are common in coral reef environments where macroalgae are present. As ocean conditions change...
Show moreUnderstanding the basis of the marine food web is essential in determining the uptake and possible control of the toxins that cause ciguatera fish poisoning (CFP), predominantly ciguatoxins. Ciguatoxins are produced by the marine, epiphytic dinoflagellate Gambierdiscus, and when transferred through the food web via herbivory, have serious environmental and health implications. Ciguatera outbreaks are common in coral reef environments where macroalgae are present. As ocean conditions change and more coral reef ecosystems shift to macroalgal domination, the risk of ciguatera outbreaks may increase. Since the first discovery of causal agents for CFP, the general consensus has been that the ciguatoxin pathway goes through herbivorous fish; however, some previous studies have suggested that herbivorous invertebrates may be another vector. Because hogfish have been found to be one of the high-risk fish species for CFP, and they are also known to consume invertebrates, more studies are necessary in order to accurately evaluate the invertebrate role as a vector. Therefore, the purpose of this study was to determine the grazing preferences of various herbivorous invertebrates on the common macroalgal hosts of Gambierdiscus, in order to examine the uptake of ciguatoxin into the food web. Four marine macroalgae were tested (Laurencia gemmifera, Halimeda incrassata, Dictyota menstrualis, and turf algae) against three different taxa ((Cerithium (Thericium) eburneum algicola (var.) (middle-spined cerith gastropods), Clibanarius tricolor (three-colored hermit crabs), and Lytechinus variegatus (variegated sea urchins)) of herbivorous invertebrates. Consumption rates were determined from changes in algal biomass. Direct G. silvae consumption rates were also determined for one species of invertebrate in a supplemental study. The experimental results indicated that there was a significant food preference for turf algae among all three species tested. There was also a significant food preference for Dictyota menstrualis for two of the species tested and Laurencia gemmifera for the other species tested (sea urchin). These results of this study have expanded our knowledge on herbivore feeding preferences and toxin uptake, which may lead to a better understanding of this crucial step in the introduction of ciguatoxin into the reef food web.
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Date Issued
2020-06-04
Identifier
fgcu_ETD_0341
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.
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Date Issued
2018-08-22
Identifier
fgcu_ETD_0258
Format
Document (PDF)
Determination of the Presence and Biomagnification of Caribbean ciguatoxins and benthic algal toxins in fishes from the Florida Keys National Marine Sanctuary
Title
Determination of the Presence and Biomagnification of Caribbean ciguatoxins and benthic algal toxins in fishes from the Florida Keys National Marine Sanctuary.
Creator
Catasus, Adam Benjamin
Abstract / Description
Ciguatera fish poisoning (CFP) is a common syndrome affecting coastal communities in the Atlantic and Indo-Pacific regions, including the Greater Caribbean. This severe illness is caused by the ingestion of reef fish contaminated with ciguatoxins (CTXs). The source of CTXs has been associated with epiphytic dinoflagellates of the genus Gambierdiscus (among others) which reside on macroalgae that are grazed by herbivores. The entry of algal CTX precursors (often referred to as gambiertoxins)...
Show moreCiguatera fish poisoning (CFP) is a common syndrome affecting coastal communities in the Atlantic and Indo-Pacific regions, including the Greater Caribbean. This severe illness is caused by the ingestion of reef fish contaminated with ciguatoxins (CTXs). The source of CTXs has been associated with epiphytic dinoflagellates of the genus Gambierdiscus (among others) which reside on macroalgae that are grazed by herbivores. The entry of algal CTX precursors (often referred to as gambiertoxins) into the food web initiates a cascade of trophic transfer events and biotransformations that have not yet been fully elucidated in the Greater Caribbean region. A critical knowledge gap addressed in the present study was to gain better predictive capability of CTX presence in fishes across trophic levels in a sub-tropical hotspot for CFP (i.e. the Florida Keys). A variety of fish including herbivores (e.g., representatives of Acanthuridae and Pomacathidae) up to apex predators (e.g., Sphyrena barracuda and Mycteroperca bonaci) were collected from a long-term monitoring site in the Florida Keys. Extracts of fish were assessed for neurotoxicity and CTX activity using the sensitive in vitro neuroblastoma (N2a) assay. Twenty five of the 66 fish (38%) examined in this study expressed sodium channel-dependent toxicity in both sensitized and non-sensitized cell treatments, highlighting the likely presence of multiple toxin classes in these reef fish. Monospecific sodium channel activity was observed in 3% of fish represented by one species: S. barracuda. Stable isotope analysis was used to determine fish trophic level and in the calculation of a food web magnification factor (FWMF) of 1.114 for CTX and CTX-like compounds, indicative of the biomagnification of these toxins. The presence of toxic fish indicates a need for risk assessment and management consideration in the Florida Keys.
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Date Issued
2019-06-06
Identifier
fgcu_ETD_0299
Format
Document (PDF)
Grazing dynamics of the pinfish (Lagodon rhomboides) on Thalassia testudinum and Halimeda incrassata across a temperature gradient in the Florida Keys and implications for Ciguatera Fish Poisoning
Title
Grazing dynamics of the pinfish (Lagodon rhomboides) on Thalassia testudinum and Halimeda incrassata across a temperature gradient in the Florida Keys and implications for Ciguatera Fish Poisoning.
Creator
Ribble, Kathryn Alissa
Abstract / Description
Seagrass beds are an important component of coastal environments and serve as important nursery grounds for juvenile and commercially important fish species. Seagrass beds are often monospecific, composed of just one species of seagrass. However, macroalgal species such as Halimeda, Laurencia, and Dictyota (among others) can also be found in seagrass beds in quantities that vary depending on many factors including grazing pressures. This study focuses on the grazing dynamics of Lagodon...
Show moreSeagrass beds are an important component of coastal environments and serve as important nursery grounds for juvenile and commercially important fish species. Seagrass beds are often monospecific, composed of just one species of seagrass. However, macroalgal species such as Halimeda, Laurencia, and Dictyota (among others) can also be found in seagrass beds in quantities that vary depending on many factors including grazing pressures. This study focuses on the grazing dynamics of Lagodon rhomboides (commonly referred to as pinfish) between two different macrophytes (Thalassia testudinum and Halimeda incrassata) over a temperature gradient in a laboratory setting representative of a seagrass bed from the middle Florida Keys (Heine Grass Bed; HGB). HGB, where samples were collected for this study, is a long-term study site for Ciguatera Fish Poisoning (CFP) research as well. CFP is a form of food poisoning in humans who consume tropical reef fish that have accumulated high levels of ciguatoxins. Ciguatoxins are naturally produced lipid-soluble toxins produced by the benthic dinoflagellate, Gambierdiscus, which enter reef food webs through the consumption of these epiphytic cells by herbivorous fishes. Thalassia testudinum and Halimeda incrassata are known to harbor high quantities of toxic Gambierdiscus species within their associated epiphytic community in areas such as HGB. The overall objective of this study is to examine the grazing dynamics of pinfish on Thalassia testudinum and Halimeda incrassata under varying temperatures within a seagrass bed environment (HGB) in the middle Florida Keys. This study will also aid in determining how ciguatoxins are being introduced into the marine food web through grazing processes occurring within seagrass beds in the middle Florida Keys and assist modeling efforts for CFP outbreaks. Additionally, it will identify if specific temperatures influence the grazing behaviors of pinfish which will lend insight into how grazing pressures change seasonally and how they may change as the climate warms. This study found that pinfish did not consume one macrophyte agar (Thalassia testudinum or Halimeda incrassata) at a significantly higher amount than the other at ambient temperature. In addition, the results also suggest that pinfish are not significantly increasing their grazing intensity on Thalassia testudinum agar across a temperature gradient (22°C – 30°C). However, the grazing intensity of pinfish on Halimeda incrassata agar did significantly increase with increasing temperature but the strength of this linear correlation is fairly weak (R2 = 0.2154). Finally, pinfish ate a marginally significantly larger amount of the Halimeda incrassata agar cubes than the Thalassia testudinum agar cubes over the temperature gradient tested (22°C – 30°C; p = 0.052).
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Date Issued
2020-01-15
Identifier
fgcu_ETD_0324
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.
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Date Issued
2016
Identifier
Leynse_fgcu_1743_10187
Format
Document (PDF)