ECOHAB 2011: Project Summaries

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Title:  CIGUAHAB: Ciguatera Investigations in the Greater Caribbean Region: Ecophysiology, Population Connectivity, Forecasting, and Toxigenesis

Institutions: Florida Gulf Coast University (lead), Woods Hole Oceanographic Institution, University of Texas at Austin, Dauphin Island Sea Lab, Universidad Veracruzana (Veracruz, México), U. S. Federal Drug Administration, University of the Virgin Islands

Investigators: Michael L. Parsons (lead), Donald M. Anderson, Deana L. Erdner, Ronald Kiene, Yuri B. Okolodkov, Mindy L. Richlen, Alison Robertson, Tyler Smith

Ciguatera fish poisoning (CFP) is the most common form of phycotoxin-borne seafood illness across the globe, including the Greater Caribbean Region (i.e., the Caribbean, Yucatan, Gulf of Mexico, Florida Keys, and Bahamas), hereafter Greater Caribbean Region (GCR). At a global level, Fleming et al. (1998) estimate that there are 50,000 - 500,000 poisonings per year. The average annual economic impact of ciguatera in the United States has been estimated to be $21 million, far surpassing public health impacts from other illnesses associated with toxic algae. CFP is caused by the consumption of seafood (primarily reef fish) contaminated with ciguatoxins. Gambiertoxins, the precursors of ciguatoxins produced by the (sub)tropical benthic dinoflagellate genus, Gambierdiscus, enter coral reef food webs when herbivores and detritivores consume Gambierdiscus during grazing on substrate macroalgae. These precursors are transferred to higher trophic levels by bioaccumulation, bioconversion and biomagnification until they reach predatory finfish species that are targeted in many fisheries. People are exposed to the toxins when they consume the fish, thereby experiencing CFP.

Objectives:

  • Characterize Gambierdiscus population diversity and connectivity on regional and local scales;
  • Determine effects of environmental factors on the growth and toxicity of representative strains of Gambierdiscus;
  • Investigate Gambierdiscus population dynamics and the environmental conditons that contribute to blooms in several representative locations for the study region;
  • Investigate the fate of ciguatera precursors, toxins and metabolites in the reef food web;
  • Model the population dynamics and toxin production of Gambierdiscus under different environmental forcings, including those associated with natural and human-induced perturbations such as pollution, reef destruction, and climate change;
  • Communicate project results and discuss applications to resource management with stakeholders in the GCR, including medical personnel, natural resources officials, fishermen, and others, and develop a website to serve as an information clearinghouse for information on CFP.
Approach:

The GCR is a region with a large and expanding problem of CFP. Consistent with the underlying philosophy of the ECOHAB program, this project will increase understanding of the ecology and oceanography of Gambierdiscus populations, leading to a predictive capability for CFP in the region. The GCR study area covers a range of environments and habitats, some pristine and others with clear anthropogenic impacts. A suite of new genetic tools and ecological methods are now available to examine Gambierdiscus populations and their environments in detail, and this information can be used to parameterize a population dynamics model of Gambierdiscus in the GCR that will have predictive value.

Expected results:

CIGUAHAB will result in a comprehensive understanding of the diversity, physiology and ecology of Gambierdiscus in the GCR, will increase our knowledge and educate managers and the public about the risks of CFP, and will develop a model of bloom dynamics and toxin production which will provide information of clear management value and lead towards a predictive capability and an opportunity to estimate effects of global warming and other climactic or environmental perturbations on this important public health issue.



Title:
Brevetoxin Metabolism and Physiology - A Freshwater Model of Morbidity in Endangered Sea Turtles


Institutions:
 Florida Atlantic University (lead), Georgia Aquarium and Harbor Branch Oceanographic Institute, Mote Marine Laboratory, Florida Fish and Wildlife Conservation Commission/Fish and Wildlife Research Institute

Investigators: Sarah L. Milton (lead), Gregory Bossart, Deborah Fauquier, Catherine J. Walsh, Leanne Flewelling

Karenia brevis, the “Florida red tide” organism that frequently blooms in some areas of the Gulf of Mexcio, produces a suite of brevetoxins that cause human respiratory illness along beaches, accumulate in shellfish, which, when consumed, cause Neurotoxic Shellfish Poisoning, and cause mass mortality of fish and a number of protected and endangered species. Among the species impacted are a variety of threatened and endangered marine turtles.  For example, in the severe Florida red tides of 2005 and 2006 at least 179 loggerhead turtles died, but other species may be impacted as well, including leatherback, green, hawksbill, and Kemp’s ridley. Exposure to red tide outbreaks is thus a major threat to sea turtles off the coast of Florida, with reported effects on the pulmonary, neuromuscular, and immune systems, though neither acute nor sublethal effects of brevetoxins on sea turtle health have been well-characterized. During red tide outbreaks, however, it cannot be determined how large or longstanding toxin exposure is prior to rescue and thus exposure levels cannot be correlated with morbidity and mortality outcomes.

Understanding the risk of brevetoxin exposure to sea turtle health is critical as such impacts may affect survival of these endangered population. Due to the nature of study on endangered sea turtles, however, these questions cannot be addressed directly, as they require experimental investigation with controlled toxin doses. This makes it difficult to establish appropriate treatment methods, and none can be devised in advance.

Objectives:

The purpose of these studies is to use a non-endangered turtle model to delineate the pathways of toxin metabolism, determine the impacts of toxins on individual organisms, and develop new methods of treating brevetoxicosis in turtles.

Approach:

In this project non-endangered turtle models will be used to determine toxin effects on critical organ systems.   As exposure in sea turtles may occur through ingestion and/or inhalation, with potentially different distributions, effects, and rates of metabolism, brevetoxins will be administered by both mechanisms to anesthetized turtles. After exposure, tissue toxin levels will be measured over time in order to investigate the uptake and excretion.  Tissues will also be sampled over time for histology to determine the impacts on specific organ systems.  Additional studies will characterize the impact of brevetoxin on immune function.  Turtle neuronal cultures will be utilized to determine the concentrations and mechanisms of neurotoxicity in turtles.  Finally, the information will be used to develop methods of treating and rehabilitating endangered turtles suffering from brevitoxicosis.

Expected results:

Developing an animal model leading to an understanding of how brevetoxins cause illness and death in turtles will provide a sound scientific basis for treatment at the numerous rescue facilities that rehabilitate sea turtles in the Gulf Coast states.


Title: A Regional Comparison of Upwelling and Coastal Land Use Patterns on the Development of HAB Hotspots Along the California Coast

Institutions: University of California at Santa Cruz (lead), University of Southern California, Monterey Bay Aquarium Research Institute, California State University/Moss Landing Marine Laboratories, University of California at Los Angeles, Southern California Coastal Water Research Project, NOAA National Ocean Service/National Centers for Coastal Ocean Science

Investigators: Raphael Kudela (lead), Clarissa Anderson, Dave Caron, Burt Jones, Gaurav Sukhatme, Chris Scholin, John Ryan, Jim Birch, Kanna Rajan, Heather Kerkering, G. Jason Smith, Yi Chao, Meredith Howard, Greg Doucette

Blooms of harmful and toxic algae have increased in frequency and severity along the 1000 mile long California coast during the past few decades, causing diverse impacts on the economy through commercial fisheries and tourism, as well as via direct impacts on marine birds and mammals.  Many of these occur at hot spots scattered along the west coast.  Pseudo-nitzschia produces a potent neurotoxin, domoic acid, which can accumulate in shellfish, other invertebrates, and, sometime fish, leading to illness and death in a variety of birds and marine mammals and necessitating shellfish harvesting closures to protect human health.  Regional ECOHAB or MERHAB projects are examining hot spots in Washington and Oregon; these regions are thought to be primarily influenced by natural processes.  While MERHAB projects in southern and central California have, among other activities, provided information from shore-based sampling about HAB hot spots in California, there have been no oceanographic studies on the west coast aimed at predictive understanding of coastal processes where human activities as well as upwelling may be stimulating HABs.  This project will compare HAB initiation and development at two California hot spots where the relative importance of upwelling and human activities (land use and runoff) differ.  Although the project will focus on Pseudo-nitzschia, the occurrence of other HABs, especially Alexandrium, which produces toxins that can cause Paralytic Shell Fish Poisoning, will also be investigated if they occur during the study.

Objective:
  1. To develop a better understanding of HAB initiation and bloom dynamics in California in response to physical and environmental forcing factors by simultaneously comparing two “hot spots”, Monterey Bay and San Pedro, California, leading to predictive models; and
  2. To establish a cutting-edge HAB alert detection system and demonstrate the utility of an integrated observing system for HABs as part of the Regional Coastal Ocean Observing System.

Approach:

The project will rely on a cutting-edge, high tech, tiered sampling methodology in collaboration with the Central and Northern California Ocean Observing System (CeNCOOS) and the Southern California Coastal Ocean Observing System (SCCOOS): existing shore-based monitoring efforts, deployment of 2 Slocum gliders with chlorophyll sensors and 2 Environmental Sample Processors (ESPs) with sensors for HAB cell/toxin detection (1 in each region), satellite imagery, statistical models, and data assimilation into ROMS model to identify when and where bloom events begin.  When a possible bloom is identified by these methods, or if a bloom is identified by another means (e.g., sudden increase in reported marine bird or mammal strandings; increase in toxicity or cell density from the shore-based network), intensive adaptive sampling will be conducted.  The sampling will include ship-based field experiments to assess species assemblage, growth conditions, response to fundamental parameters such as temperature, light, nutrients, and will be adjusted as the bloom evolves.  The enhanced understanding of conditions before and during blooms will be used to improve models for predicting future blooms.

Expected results:

By identifying blooms while they are still offshore before they impact near shore areas, this study will immediately improve the management response to HABs.  It will also lead to development of a HAB alert detection system and bloom forecasts that will provide early warning that will further improve shellfish, wildlife, and public health management.  If human activities are found to cause HABs it will lead to the development of new strategies for HAB prevention.



Title:  Species and Strain Differences in the Toxicity of Caribbean Gambierdiscus Species: Implications for Ciguatera Fish Poisoning in the Caribbean

Institutions: NOAA National Ocean Service/National Centers for Coastal Ocean Science (lead), North Carolina State University at Raleigh

Investigators: R. Wayne Litaker, Patricia Tester, Damian Shea

Ciguatera fish poisoning (CFP) is caused by the bioaccumulation of toxins, produced by tropical dinoflagellates in the genus Gambierdiscus, into herbivorous and carnivorous fish. Globally, CFP causes more human illness than all other harmful algal bloom species combined. Despite this fact, relatively little is known about the variety of ciguatoxin congeners produced by different Gambierdiscusspecies and the overall differences in toxicity among and between species. Possessing this knowledge is crucial for understanding CFP and how it may differ between the Atlantic and Pacific basins. For example, ciguatoxins (CTXs) isolated from Atlantic and Pacific fishes are structurally different. It has been proposed that these differences are due to the production of different toxin precursors by the resident species. Supporting evidence for this hypothesis comes from a recent study that confirmed distributional differences in Gambierdiscus species found in each basin. These differences may also account for why CFP symptoms tend to vary between the two regions. The project hypothesis is that relatively few Gambierdiscus species are highly toxic and that they disproportionately contribute to the flux of toxins that enter the food chain. This appears to be the case with Pacific Gambierdiscus species where G. polynesiensis is generally far more toxic on a per cell basis than other co-occurring species. If this hypothesis is correct for the Caribbean, then it may be possible to assess CFP potential by monitoring these key species. Interestingly, total toxicity per cell also appears to be inversely proportional to the latitude from which a Gambierdiscus clone was isolated. If true, this could also influence the severity and frequency of CFP occurrences in an area.

Objectives:

  1. Establish the relative per cell toxicity of the five known CaribbeanGambierdiscus species and one Gambierdiscus ribotype using genetically characterized clones currently in culture;
  2. Provide detailed analysis of the CTX congeners produced by the most toxic species;
  3. Characterize and compare the toxins produced by Caribbean isolates of G. caribaeus, a globally distributed species, to toxins isolated from other Pacific species;
  4. Assess the extent to which CTX toxicity varies within a species and whether per cell toxicity varies systematically with latitude or region.

Approach:

This project will draw on the large Gambierdiscus culture collection established by members of the Tester/Litaker laboratory over the past 8 years as well as many years experience isolating and culturing Gambierdiscus cells. The approach involves the following steps: 1) Screen Caribbean species using receptor binding bioassay to determine if Gambierdiscus ribotype 2 is the most toxic; 2) ScreenGambierdiscus caribaeus cultures from the Caribbean and Pacific to characterize the toxin suite being produced; 3) Grow large scale cultures of Gambierdiscusribotype 2 and other toxic Caribbean Gambierdiscus species for detailed toxin analysis; and 4) Simultaneously characterize within species differences in toxicity and test the hypothesis that per cell toxicity increases with latitudinal gradients in the Caribbean.

Expected results:

The results of these studies will provide valuable information about ciguatoxins entering the food chain, and for the first time, will systematically address whether the amounts and types of ciguatoxins being produced in the Caribbean are different from those in the Pacific, and whether isolates from lower latitudes are more toxic. These data will also help determine the likelihood of success for a cell-based monitoring system for predicting CFP risk.



Last updated: May 16, 2013