BREVETOXIN IN BLOOD, BIOLOGICAL FLUIDS, AND TISSUES OF SEA TURTLES NATURALLY EXPOSED TOKARENIA BREVISBLOOMS IN CENTRAL WEST FLORIDA

Abstract

In 2005 and 2006, the central west Florida coast experienced two intense Karenia brevis red tide events lasting from February 2005 through December 2005 and August 2006 through December 2006. Strandings of sea turtles were increased in the study area with 318 turtles (n = 174, 2005; n = 144, 2006) stranding between 1 January 2005 and 31 December 2006 compared to the 12-yr average of 43 +/- 23 turtles. Live turtles (n = 61) admitted for rehabilitation showed clinical signs including unresponsiveness, paresis, and circling. Testing of biological fluids and tissues for the presence of brevetoxin activity by enzyme-linked immunosorbent assay found toxin present in 93% (52 of 56) of live stranded sea turtles, and 98% (42 of 43) of dead stranded sea turtles tested. Serial plasma samples were taken from several live sea turtles during rehabilitation and toxin was cleared from the blood within 5-80 days postadmit depending upon the species tested. Among dead animals the highest brevetoxin levels were found in feces, stomach contents, and liver. The lack of significant pathological findings in the majority of animals necropsied supports toxin-related mortality.

Brevetoxin exposure in sea turtles in south Texas (USA) during Karenia brevis red tide

“…Three of the green sea turtles were found alive during the 2015 red tide event and exhibited signs similar to those seen in other sea turtles exposed to PbTx from red tide exposure (e.g. neurologic signs, lethargy, muscle weakness; Fauquier et al 2013). All were lethargic when located and died within 2 d. Two Kemp's ridley turtles found alive during the 2016 event exhibited signs of PbTx exposure.…”

“…It is also important to note that these PbTx concentrations are from single points in time and provide no information on accumulation and depuration of PbTx from tissues. In a recent study by Cocilova et al (2017), PbTx-3 was cleared within days from the tissues of freshwater turtles experimentally exposed to sublethal doses, while longer elimination times (several weeks) have been observed in naturally exposed sea turtles (Fauquier et al 2013). …”

“…Due to good body condition in these turtles and the lack of apparent alternative causes of death, the cause of death was attributed to brevetoxicosis (Fauquier et al 2013). Results were inconclusive regarding the probable cause of death for 1 Kemp's ridley, due to fishing line entanglement, and 3 green turtles, due to scavenging, signs of water inhalation, and 1 which had excessive epibiota present, a possible indication of long-term illness, and an embedded hook in its left front flipper with signs of infection.…”

“…This increased effort will better inform our understanding of red tides and their contribution to sea turtles mortality in the region. Moreover, timely intervention by stranding responders, and diagnosis and treatment of live individuals with brevetoxicosis is critical for successful recovery and release (Fauquier et al 2013). Additionally, improvements in the current red tide monitoring system in Texas, including more sampling locations and standardized frequent sampling, would improve wildlife management responses as well as protect public health and recreation concerns associated with harmful algal blooms.…”

“…K. brevis blooms have been associated with increases in sea turtle strandings in Florida (Fauquier et al 2013, A. Foley pers. comm (Fauquier et al 2013).…”