Comparing Blood Mercury Concentrations in Captive and Wild Bottlenose Dolphins (Tursiops truncatus)
The National Institute of Standard and Technology (NIST) has a history of involvement in wild population bottlenose dolphin (Tursiops truncatus) health assessments since 2002 sponsored by NOAA National Marine Fishery Service, Sarasota Dolphin Research Program, and Dolphin Quest including support for the banking of tissues in the National Marine Mammal Tissue Bank (NMMTB), designing sample collection protocols, providing technical assistance in the field, and analyzing samples for trace elements and organic pollutants. NIST began collaborating with Dolphin Quest Oahu and Hawaii facilities in 2010 to establish a captive dolphin program for tissue archival and chemical analysis. Captive dolphin research is valuable to address health concerns that effect animals in captivity and also extremely important to aid in answering questions about wild dolphins that captive controlled settings can provide for research studies. This study focuses on measuring total mercury in captive bottlenose dolphins and comparing their blood concentrations to the wild bottlenose dolphin population in Sarasota Bay, Florida. Mercury is a non-essential toxic trace element that is known to bioaccumulate and biomagnify up food chains. The few published studies examining mercury in captive bottlenose dolphin blood are statistically limited by small data sets of 4 to 7 animals.1,2 The current study includes blood collected from 16 captive bottlenose dolphins at Dolphin Quest that encompass both genders and all age classes (calf, sub-adult, adult). Blood collections were executed under a detailed and standardized protocol developed by NIST. Total mercury was measured in whole blood using direct combustion atomic absorption spectrometry (AAS). Mercury in Dolphin Quest adult male captive dolphin (n = 6) blood was 52 ± 2 ng/g, wet mass fraction. This is approximately 10 times lower than the blood mercury concentrations (475 ± 58 ng/g, wet mass fraction) measured in Sarasota adult male dolphins (n = 10).3 The differences in blood mercury concentrations between captive and wild bottlenose dolphins may be due to differences in dietary food sources and mercury concentrations in the fish species Dolphin Quest animals consume are being measured. Captive dolphin blood mercury data will be integrated in to animal life history and dietary information that is additionally being collected. Dolphin Quest samples are also being analyzed for other trace elements, stable isotopes, and metabolomics.
The authors wish to thank Jay Sweeney, Julie Rocho, Katie Rice, and the Dolphin Quest Staff at the Oahu and Hawaii locations; Mote Marine Laboratory and the Sarasota Live Capture Team; NIST Specimen Bank Team.
* Presenting author
1. Nigro M, Campana A, Lanzillotta E, Ferrara R. Mercury exposure and elimination rates in captive bottlenose dolphins. Mar Pollut Bul. 2002;44:1071–1075.
2. Yong SH, Hunter S, Clayton LA, Rifkin E, Bouwer EJ. Assessment of mercury and selenium concentrations in captive bottlenose dolphin's (Tursiops Truncatus) diet fish, blood, and tissue. Sci Total Environ. 2012;414:220–226.
3. Bryan CE, Christopher SJ, Balmer BC, Wells RS. Establishing baseline levels of trace elements in blood and skin of bottlenose dolphins in Sarasota Bay, Florida: implications for non-invasive monitoring. Sci Total Environ. 2007;388:325–342.