Article

Brevetoxicosis: red tides and marine mammal mortalities.

Florida Fish and Wildlife Conservation Commission, Fish and Wildlife Research Institute, St Petersburg, Florida 33701, USA.
Nature (Impact Factor: 42.35). 07/2005; 435(7043):755-6. DOI: 10.1038/nature435755a
Source: PubMed

ABSTRACT Potent marine neurotoxins known as brevetoxins are produced by the 'red tide' dinoflagellate Karenia brevis. They kill large numbers of fish and cause illness in humans who ingest toxic filter-feeding shellfish or inhale toxic aerosols. The toxins are also suspected of having been involved in events in which many manatees and dolphins died, but this has usually not been verified owing to limited confirmation of toxin exposure, unexplained intoxication mechanisms and complicating pathologies. Here we show that fish and seagrass can accumulate high concentrations of brevetoxins and that these have acted as toxin vectors during recent deaths of dolphins and manatees, respectively. Our results challenge claims that the deleterious effects of a brevetoxin on fish (ichthyotoxicity) preclude its accumulation in live fish, and they reveal a new vector mechanism for brevetoxin spread through food webs that poses a threat to upper trophic levels.

1 Follower
 · 
190 Views
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Bottlenose dolphins (Tursiops truncatus) inhabit coastal and estuarine habitats across the globe. Well-studied dolphin communities thrive in some peninsular Florida bays, but less is known about dolphins in the Florida panhandle where coastal development, storms, algal blooms, fishery interactions, and catastrophic pollution have severely impacted their populations. Dolphins can react to disturbance and environmental stressors by modifying their movements and habitat use, which may put them in jeopardy of conflict with humans. Fishery interaction (FI) plays an increasing role in contributing to dolphin mortalities. I investigated dolphin movements, habitat use, residency patterns, and frequency of FI with sport fishing. Dolphins were tracked using radio tags and archival data loggers to determine fine-scale swimming, daily travels, and foraging activity. Dolphin abundance, site fidelity, ranging, stranding mortality, and community structure was characterized at Choctawhatchee and Pensacola Bays in the Florida Panhandle via small boat surveying and photo-identification. Reported increases in dolphin interactions with sport anglers were assessed at deep sea reefs and coastal fishing piers near Destin, FL and Orange Beach, AL. Results from these studies yield insights into the ranging and foraging patterns of bottlenose dolphins, and increase our knowledge of them in the northern Gulf of Mexico. Dolphins were tagged with short-term Trac Pac tags (N=23) and bolt on radio-tags (N=5) during 1995-2007. Swim speeds averaged 1.6 m/s (±0.43 SD), which agreed with the predicted mean cost of transport. On average, 48% of their day was spent transiting between habitats. Swimming and activity rates did not vary significantly with time of day/night. Foraging and social interactions constituted 39% of their day. Increased foraging was detected by stomach temperature changes that revealed dolphins fed during daylight, but also at night with a peak starting just after sunset. Tagged dolphins exhibited behaviors suggesting ‘sleep’ during slow speed swimming, which represented 15% of their day on average. Dolphins made daily movements beyond their expected core area, heading up river tributaries, and to the open sea. Surveys in Choctawhatchee Bay began in 2006 and later expanded to include Pensacola Bay in 2010 following concern of dolphin mortalities in concert with the Deepwater Horizon spill and two extremely cold winters. Photo-identification revealed dolphins moved frequently between the bays. Of 655 individuals identified in 2010-11, 22% were seen during all seasons, with highest abundance in the fall. Resident dolphins showed site fidelity to specific areas (42%) or traveled between parts of the bays (58%). Three communities of dolphins were identified from stable isotope analysis and photo-id: 1) tidal inlet associated, 2) estuarine specific, and 3) river delta associated. Dolphins traveled over 70 km via the near-shore Gulf between the inlets, and through the inshore waterways. The findings suggest dolphin communities in these bays overlap and many dolphins had a high probability of oil exposure in 2010. I observed sport fishing trips to assess frequency and nature of FI over 28 months. FI was seen at 18% of fishing reef spots. Scavenging of discarded fish was seen most often, while depredation of catch occurred in 40% of FI observations. Of 103 dolphins identified on offshore reefs, 13% were encountered repeatedly. At coastal fishing piers, dolphins came within 100 m on 42% of visits, while FI was seen on 17% of visits. Most dolphins at the fishing piers were known inlet and estuarine residents, while offshore reef dolphins were never seen near the beach. This indicates that discrete communities are involved. Harmful interactions with dolphins on reefs and at fishing piers negatively affect these resident communities. Mitigation of FI is suggested by use of avoidance strategies, gear modifications, and improved fish release practices.
    03/2014; University of Central Florida.
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: An unusual mortality event (UME) was declared for cetaceans in the northern Gulf of Mexico (GoM) for Franklin County, Florida, west through Louisiana, USA, beginning in February 2010 and was ongoing as of September 2014. The 'Deepwater Horizon' (DWH) oil spill began on 20 April 2010 in the GoM, raising questions regarding the potential role of the oil spill in the UME. The present study reviews cetacean mortality events that occurred in the GoM prior to 2010 (n = 11), including causes, durations, and some specific test results, to provide a historical context for the current event. The average duration of GoM cetacean UMEs prior to 2010 was 6 mo, and the longest was 17 mo (2005-2006). The highest number of cetacean mortalities recorded during a previous GoM event was 344 (in 1990). In most previous events, dolphin morbillivirus or brevetoxicosis was confirmed or suspected as a causal factor. In contrast, the current northern GoM UME has lasted more than 48 mo and has had more than 1000 reported mortalities within the currently defined spatial and temporal boundaries of the event. Initial results from the current UME do not support either morbillivirus or brevetoxin as primary causes of this event. This review is the first summary of cetacean UMEs in the GoM and provides evidence that the most common causes of previous UMEs are unlikely to be associated with the current UME.
    Diseases of Aquatic Organisms 11/2014; 112(2). DOI:10.3354/dao02807 · 1.59 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: The use of chemical compounds to suppress the growth of competitors is a competitive strategy known as allelopathy that can be readily observed with many phytoplankton species in laboratory studies. However, it is unclear how these allelopathic interactions are altered when the complexity of the system is increased to more closely mimic natural conditions. In the present study, we conducted laboratory experiments to decipher how the identity, abundance, and growth stage of competitors affect the outcome of allelopathic interactions with the red tide dinoflagellate Karenia brevis. Multiple chemical compounds produced by K. brevis were found to inhibit the growth of 4 phytoplankton competitors, although these competitors were susceptible to different combinations of compounds. We found that physiological state and cell concentration of competitors were important determinants of allelopathy, with early-stage (lag phase) cells more vulnerable to allelopathic effects than later growth stages for the diatom Skeletonema grethae. Despite being allelopathic to multiple competitors in the laboratory, in a microcosm experiment using plankton field assemblages, extracellular extracts of 2 strains of K. brevis had no effects on some taxa although they stimulated the growth of some diatoms. This suggests that in a species-rich ecological community under oligotrophic conditions, the relative importance of K. brevis allelopathy may not be as high as most laboratory studies predict.
    Marine Ecology Progress Series 10/2010; 416:69-78. DOI:10.3354/meps08788 · 2.64 Impact Factor

Full-text (2 Sources)

Download
83 Downloads
Available from
May 27, 2014