Harmful Algae 37 (2014) 194–202
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Brevetoxin exposure, superoxide dismutase activity and plasma protein electrophoretic profiles in wild-caught Kemp’s ridley sea turtles (Lepidochelys kempii) in southwest Florida Justin R. Perrault a,*, Jeffrey R. Schmid b, Catherine J. Walsh a, Jennifer E. Yordy a, Anton D. Tucker a,1 a b
Mote Marine Laboratory, 1600 Ken Thompson Parkway, Sarasota, FL 34236, USA Conservancy of Southwest Florida, 1495 Smith Preserve Way, Naples, FL 34102, USA
A R T I C L E I N F O
A B S T R A C T
Article history: Received 4 March 2014 Received in revised form 10 June 2014 Accepted 10 June 2014 Available online
Because of their vulnerable population status, assessing exposure levels and impacts of toxins on the health status of Gulf of Mexico marine turtle populations is critical. From 2011 to 2013, two large blooms of the red tide dinoflagellate, Karenia brevis, occurred along the west coast of Florida USA (from October 2011 to January 2012 and October 2012 to April 2013). Other than recovery of stranded individuals, it is unknown how harmful algal blooms affected the Kemp’s ridley sea turtles (Lepidochelys kempii) inhabiting the affected coastal waters. It is essential to gather information regarding brevetoxin exposure in these turtles to determine if it poses a threat to marine turtle health and survival. From April 2012 to May 2013, we collected blood from 13 immature Kemp’s ridley turtles captured in the Pine Island Sound region of the Charlotte Harbor estuary. Nine turtles were sampled immediately after or during the red tide events (bloom group) while four turtles were sampled between the events (nonbloom group). Plasma was analyzed for total brevetoxins (reported as ng PbTx-3 eq/mL), superoxide dismutase (SOD) activity, total protein concentration and protein electrophoretic profiles (albumin, alpha-, beta- and gamma-globulins). Brevetoxin concentrations ranged from 7.0 to 33.8 ng PbTx-3 eq/ mL. Plasma brevetoxin concentrations in the nine turtles sampled during or immediately after the red tide events were significantly higher (by 59%, P = 0.04) than turtles sampled between events. No significant correlations were observed between plasma brevetoxin concentrations and plasma proteins or SOD activity, most likely due to the small sample size; however alpha-globulins tended to increase with increasing brevetoxin concentrations in the bloom group. Smaller (carapace length and mass) bloom turtles had higher plasma brevetoxin concentrations than larger bloom turtles, possibly due to a growth dilution effect with increasing size. The research presented here improves the current understanding of potential impacts of environmental brevetoxin exposure on marine turtle health and survival. ß 2014 Elsevier B.V. All rights reserved.
Keywords: Brevetoxin Karenia brevis Kemp’s ridley sea turtle Plasma protein electrophoresis Red tide Superoxide dismutase
1. Introduction From the 1940s to 1980s, Kemp’s ridley sea turtles (Lepidochelys kempii) experienced a substantial population decrease resulting from egg harvest and fisheries bycatch (Marquez, 1994; Lewison et al., 2003); however, the primary nesting population of Rancho
* Corresponding author. Tel.: +1 941 388 4441x213; fax: +1 9413884312. E-mail addresses:
[email protected] (J.R. Perrault),
[email protected] (J.R. Schmid),
[email protected] (C.J. Walsh),
[email protected] (J.E. Yordy),
[email protected] (A.D. Tucker). 1 Present address: Western Australian Department of Parks and Wildlife, 17 Dick Perry Avenue, Kensington, Western Australia 6151, Australia. http://dx.doi.org/10.1016/j.hal.2014.06.007 1568-9883/ß 2014 Elsevier B.V. All rights reserved.
Nuevo, Mexico has been increasing in the last 20 years due to protection of eggs and the implementation of turtle excluder devices in shrimp trawls (NMFS, USFWS and SEMARNAT, 2011). While a number of threats to the Kemp’s ridley turtle population have been reduced, one major, persistent threat in the Gulf of Mexico is the frequent occurrence of blooms of the toxic dinoflagellate Karenia brevis, also known as ‘‘red tide’’. These harmful algae produce a suite of lipid soluble cyclic polyether neurotoxins collectively termed brevetoxins that result in massive fish kills, large numbers of marine turtle and marine mammal mortalities, shellfish contamination and severe respiratory effects in humans (Landsberg, 2002; Flewelling et al., 2005; Fauquier et al., 2013b; Walsh et al., 2010). Harmful algal blooms, including those
J.R. Perrault et al. / Harmful Algae 37 (2014) 194–202
that cause red tides, appear to be increasing in their frequency and range (Hallegraeff, 2010; NMFS, USFWS and SEMARNAT, 2011). More than 300 marine turtle mortalities were attributed to red tide toxins during the intense blooms of 2005 and 2006 (Fauquier et al., 2013b). The risks that these toxins pose to marine turtles is high, yet understanding of the risks is hindered by lack of data for these imperiled organisms, even though environmental toxins are regarded as a top research priority for marine turtles (Hamann et al., 2010; NMFS, USFWS and SEMARNAT, 2011). Marine turtles are exposed to brevetoxins through two routes: inhalation of aerosolized toxins and ingestion of prey items that contain accumulated toxin (Flewelling et al., 2005). In rats, inhaled and ingested brevetoxins are detected in the blood 0.05). 3.2. Plasma brevetoxin concentrations and superoxide dismutase activity Brevetoxin concentrations (range = 7.0–33.8 ng PbTx-3 eq/mL) are reported in Table 1. Table 2 summarizes brevetoxin concentrations in marine turtle tissues from the literature. Brevetoxin concentrations were significantly higher in bloom Kemp’s ridley
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Table 1 Length (SCLmin in cm), mass (kg), brevetoxin concentrations (ng PbTx-3 eq/mL), superoxide dismutase (SOD) activity (U/ml) and plasma protein electrophoresis (g/dl) results of Kemp’s ridley sea turtles captured in Charlotte Harbor National Estuary. Results of Pearson correlations comparing SCLmin (in cm) and mass (in kg) to brevetoxin concentrations, SOD activity and total protein and protein fractions are also presented. Significant correlations are bolded. ID Lk Lk Lk Lk Lk Lk Lk Lk Lk Lk Lk Lk Lk
71 81 82 83 84 91 93 95 96 97 98 99 100
Mean SD Median Min Max r (SCLmin) P r (mass) P a b
Bloom status
Capture date
SCLmin
Mass
Brevetoxins
SOD
TP
Albumin
a2
Total a
b
g
Globulin
Bloom Non-bloom Non-bloom Non-bloom Non-bloom Bloom Bloom Bloom Bloom Bloom Bloom Bloom Bloom
11 19 19 19 19 22 14 13 13 14 14 14 16
33.8 45.8 47.7a 40.7 29.6 30.0 39.8 36.4 48.4* 33.2 52.8 45.2 39.2
3.0 10.0 19.0 8.0 1.0 2.0 6.0 5.0 13.2a 3.0 19.0 10.0 6.0
22.8 17.3 16.9 7.0 15.6 33.8 22.2 25.4 22.2 29.7 16.0 13.0 18.1
50.2 36.5 47.4 44.7 51.3 36.3 66.8 59.1 60.6 52.1 31.1 45.9 41.6
3.6 3.4 5.5 3.9 2.9 3.8 3.7 3.4 4.0 3.6 4.1 3.3 3.3
1.14 0.81 1.12 1.04 1.05 1.01 0.93 0.98 1.10 0.98 1.02 0.94 0.76
0.17 0.35 0.30 0.28 0.27 0.49 0.28 0.09 0.14 0.15 0.16 0.15 0.01
0.27 0.21 0.47 0.22 0.10 0.27 0.35 0.43 0.29 0.29 0.36 0.24 0.37
0.44 0.55 0.77 0.51 0.37 0.76 0.63 0.52 0.42 0.44 0.52 0.40 0.38
0.63 0.65 0.96 0.83 0.61 0.69 0.64 0.58 0.98 0.64 0.71 0.65 0.54
1.39 1.38 2.65 1.52 0.88 1.34 1.49 1.32 1.50 1.54 1.86 1.32 1.63
2.46 2.59 4.38 2.86 1.85 2.79 2.77 2.42 2.90 2.62 3.08 2.37 2.54
– – – – – – – – –
– – – – – – – – –
40.2 7.4 39.8 29.6 52.8 – – – –
8.1 6.0 6.0 1.0 19.0 – – – –
20.0 7.1 18.1 7.0 33.8 0.27 0.38 –0.43 0.15
48.0 10.3 47.4 31.1 66.8 0.21 0.49 0.49 0.09
3.7 0.6 3.6 2.9 5.5 0.50a 0.08 0.71a 0.01
0.99 0.11 1.01 0.76 1.14 0.04 0.90 0.15 0.62
0.22 0.13 0.17 0.01 0.49 0.20 0.52 0.08 0.79
0.30 0.10 0.29 0.10 0.47 0.36 0.22 0.47 0.11
0.52 0.13 0.51 0.37 0.77 0.08 0.79 0.26 0.38
0.70 0.14 0.65 0.54 0.98 0.52a 0.07 0.64a 0.02
1.52 0.40 1.49 0.88 2.65 0.61a 0.03 0.75a 0.003
2.74 0.58 2.62 1.85 4.38 0.56b 0.045 0.74b 0.004
April, 2012 September, 2012 September, 2012 September, 2012 September, 2012 March, 2013 April, 2013 May, 2013 May, 2013 May, 2013 May, 2013 May, 2013 May, 2013
a1
A:G 0.46 0.31 0.25 0.36 0.57 0.36 0.34 0.41 0.38 0.37 0.33 0.40 0.30 0.37 0.08 0.36 0.26 0.57 0.59 0.03 0.60 0.03
Protein data were log transformed. Protein data were square-root transformed.
turtles (mean SD = 22.6 6.5 ng PbTx-3 eq/mL) compared to nonbloom (mean SD = 14.2 4.9 ng PbTx-3 eq/mL) turtles (U0.05 (2), 4, 9 = 36, P = 0.04; Fig. 2). Additionally, in bloom turtles, brevetoxin concentrations decreased logarithmically with increasing SCLmin (r = –0.81; P = 0.01; Fig. 3a) and mass (r = –0.79; P = 0.01; Fig. 3b). SOD activity (range = 31.1–66.8 U/mL) is presented in Table 1. SOD activity did not correlate with SCLmin or mass and did not differ in the non-bloom and bloom groups (P > 0.05); however, SOD activity was slightly higher in the bloom group (Fig. 2). SOD activity and brevetoxin concentrations were not significantly correlated (P > 0.05). 3.3. Total protein and protein fractions Results of TP analysis and protein electrophoresis are presented in Table 1. TP and several protein fractions (b, g, globulin) and the A:G ratio significantly correlated with SCLmin and mass (P < 0.05; see Table 1 for statistical results). In bloom turtles, total a-globulin proteins tended to increase with increasing brevetoxin concentrations (y = 0.01x + 0.24; r = 0.60, P = 0.09). 4. Discussion 4.1. Brevetoxins To our knowledge, no other published studies have reported brevetoxin concentrations for free-ranging Kemp’s ridley turtles, only stranded and rehabilitated turtles showing obvious signs of brevetoxicosis. All Kemp’s ridleys sampled during our study tested positive for brevetoxin exposure. The sampling of blood plasma was chosen because it is (1) in equilibrium with a number of tissues and (2) represents an important non-invasive and non-lethal biomonitoring technique (Fairey et al., 2001; Woofter et al., 2005a). We found that plasma brevetoxin concentrations were significantly lower in non-bloom turtles sampled prior to the bloom that began in September 2012 (previous bloom ended in January of 2012) in comparison to bloom turtles sampled immediately after or during red tide blooms. Yet, the concentrations were of the same order of
magnitude (Table 2) and only differed by 8.4 ng PbTx-3 eq/mL. These results indicate that brevetoxins are extremely persistent in the environment (and in turtle tissues; Fauquier et al., 2013b) and that marine turtles are still exposed through prey species for several months after a bloom has dissipated (Landsberg et al., 2009). This finding is similar to bottlenose dolphins (Tursiops truncatus) from Sarasota Bay, FL, USA who tested positive for brevetoxin exposure (in urine, feces, and gastric fluid) when Karenia brevis was not present for over four months (Twiner et al., 2011). The Kemp’s ridley turtles from our study were free-swimming, actively foraging and showed no physical signs of brevetoxin exposure (i.e., clinical neurologic signs, lethargy, muscle weakness; Walsh et al., 2010; Fauquier et al., 2013a). However, some plasma brevetoxin concentrations in the free-ranging turtles from our study were similar to the lower range of concentrations of stranded and rehabilitated Kemp’s ridley turtles during 2011–2012 and 2012–2013 blooms (D. Fauquier, personal communication). Additionally, the Kemp’s ridley turtles from our study had higher plasma brevetoxin concentrations than free-ranging red-tide exposed bottlenose dolphins from Sarasota Bay (all plasma samples were
