Comparative analysis of three brevetoxin-associated bottlenose dolphin (Tursiops truncatus) mortality events in the Florida Panhandle region (USA).
In the Florida Panhandle region, bottlenose dolphins (Tursiops truncatus) have been highly susceptible to large-scale unusual mortality events (UMEs) that may have been the result of exposure to blooms of the dinoflagellate Karenia brevis and its neurotoxin, brevetoxin (PbTx). Between 1999 and 2006, three bottlenose dolphin UMEs occurred in the Florida Panhandle region. The primary objective of this study was to determine if these mortality events were due to brevetoxicosis. Analysis of over 850 samples from 105 bottlenose dolphins and associated prey items were analyzed for algal toxins and have provided details on tissue distribution, pathways of trophic transfer, and spatial-temporal trends for each mortality event. In 1999/2000, 152 dolphins died following extensive K. brevis blooms and brevetoxin was detected in 52% of animals tested at concentrations up to 500 ng/g. In 2004, 105 bottlenose dolphins died in the absence of an identifiable K. brevis bloom; however, 100% of the tested animals were positive for brevetoxin at concentrations up to 29,126 ng/mL. Dolphin stomach contents frequently consisted of brevetoxin-contaminated menhaden. In addition, another potentially toxigenic algal species, Pseudo-nitzschia, was present and low levels of the neurotoxin domoic acid (DA) were detected in nearly all tested animals (89%). In 2005/2006, 90 bottlenose dolphins died that were initially coincident with high densities of K. brevis. Most (93%) of the tested animals were positive for brevetoxin at concentrations up to 2,724 ng/mL. No DA was detected in these animals despite the presence of an intense DA-producing Pseudo-nitzschia bloom. In contrast to the absence or very low levels of brevetoxins measured in live dolphins, and those stranding in the absence of a K. brevis bloom, these data, taken together with the absence of any other obvious pathology, provide strong evidence that brevetoxin was the causative agent involved in these bottlenose dolphin mortality events.
Marine Biotoxins Program, National Oceanic and Atmospheric Administration/National Ocean Service, Charleston, South Carolina, USA. mtwiner@umd.umich.edu
Michael J
MJ
Twiner
Leanne J
LJ
Flewelling
Spencer E
SE
Fire
Sabrina R
SR
Bowen-Stevens
Joseph K
JK
Gaydos
Christine K
CK
Johnson
Jan H
JH
Landsberg
Tod A
TA
Leighfield
Blair
B
Mase-Guthrie
Lori
L
Schwacke
Frances M
FM
Van Dolah
Zhihong
Z
Wang
Teresa K
TK
Rowles
D000818:Animals; D050681:Bottle-Nosed Dolphin / Q000378:metabolism*; D004781:Environmental Exposure / Q000009:adverse effects; D004784:Environmental Monitoring; D005260:Female; D005431:Florida; D007608:Kainic Acid / Q000031:analogs & derivatives / Q000378:metabolism / Q000633:toxicity; D007668:Kidney / Q000378:metabolism; D008099:Liver / Q000378:metabolism; D008297:Male; D008387:Marine Toxins / Q000378:metabolism* / Q000633:toxicity*; D035964:Oxocins / Q000378:metabolism* / Q000633:toxicity*; D000095702:Polyether Toxins
D007608:Kainic Acid; D008387:Marine Toxins; D035964:Oxocins; C053342:brevetoxin; D000095702:Polyether Toxins; C012301:domoic acid