From dolphin health and physiology studies to dolphin rescues due to line entanglements; from Florida to Louisiana to Colombia; the 2014 Nicks n Notches annual report of the Sarasota Dolphin Research Program provides an interesting glimpse of the activities of the SDRP team. You can download a copy (4 MB pdf) for your reading pleasure.
Researchers are still learning about how marine mammals can return from a long deep dive without suffering the “bends.”
Nitrogen, which is a gas at the surface, will dissolve in the blood with increasing pressure. So, as a dolphin or whale makes a deep dive, more and more nitrogen will dissolve in the blood as it passes through the lungs.
A rapid ascent from a prolonged deep dive should bring on what is called the bends, as the nitrogen returns to a gas, forming bubbles in the blood which can cause massive damage to tissues and small blood vessels.
But on a regular basis, some dolphins dive to 1,000 ft or more for many minutes, and other marine mammals dive much deeper and longer. And neither dolphins nor other deep divers seem to get the bends. How come?
Scientists have been struggling to answer this question for decades, and a new study may shed more light on the subject.
A recently published paper (see below) compared bubbles in dolphins who died after stranding, with dolphins who survived after stranding and were subsequently released, and with wild Sarasota Bay dolphins captured and released for a health assessment.
While somewhat complex, the paper offers a nice review of theories of the physiological mechanisms that allow marine mammals to make repeated long dives without physiological consequences.
Authors on the study include SDRP Director Randy Wells.
Dennison, S., M. J. Moore, A. Fahlman, K. Moore, S. Sharp, C. T. Harry, J. Hoppe, M. Niemeyer, B. Lentell, and R. S. Wells. 2011. Bubbles in live-stranded dolphins. Proc. R. Soc. B published online before print October 12, 2011, doi:10.1098/rspb.2011.1754
Bubbles in live-stranded dolphins
S. Dennison, M. J. Moore, A. Fahlman, K. Moore, S. Sharp, C. T. Harry, J. Hoppe, M. Niemeyer, B. Lentell and R. S. Wells
Bubbles in supersaturated tissues and blood occur in beaked whales stranded near sonar exercises, and post-mortem in dolphins bycaught at depth and then hauled to the surface. To evaluate live dolphins for bubbles, liver, kidneys, eyes and blubber–muscle interface of live-stranded and capture-release dolphins were scanned with B-mode ultrasound. Gas was identified in kidneys of 21 of 22 live-stranded dolphins and in the hepatic portal vasculature of 2 of 22. Nine then died or were euthanized and bubble presence corroborated by computer tomography and necropsy, 13 were released of which all but two did not re-strand. Bubbles were not detected in 20 live wild dolphins examined during health assessments in shallow water. Off-gassing of supersaturated blood and tissues was the most probable origin for the gas bubbles. In contrast to marine mammals repeatedly diving in the wild, stranded animals are unable to recompress by diving, and thus may retain bubbles. Since the majority of beached dolphins released did not re-strand it also suggests that minor bubble formation is tolerated and will not lead to clinically significant decompression sickness.
Keywords: stranding; decompression sickness; gas bubbles; diving physiology; marine mammals.
A total of 11 oral or poster presentations on SDRP research are scheduled at the Society for Marine Mammalogy’s upcoming Conference in Tampa, FL, from November 27th to December 2nd, 2011.
The topics include conservation efforts to reduce dolphin entanglement and public interactions, prey density and foraging, tagging and tracking, and physiology.
SDRP staff Brian Balmer, Kim Bassos-Hull, Elizabeth Berens McCabe, and Katie McHugh are presenters, and former grad student Michelle Barbieri is giving an invited presentation in association with the F.G. Wood Memorial Scholarship Award.
SDRP Director Randy Wells is a co-author on eight of the presentations (and President of the Society for Marine Mammalogy).
DBRI Vice President Michael Scott has been responsible for organizing the many hundreds of posters that will be presented at the conference.
A full list of presentations is included below.
Presentations at the 19th Biennial Conference
The Biology of Marine Mammals.
Nov 27 – Dec 2, 2011. Tampa, FL.
Balmer, B. C., L. H. Schwacke, R. S. Wells, J. D. Adams, R. C. George, S. M. Lane, W. A. McLellan, P. E. Rosel, K. Sparks, T. Speakman, and D. A. Pabst. 2011. Bottlenose dolphin (/Tursiops truncatus)/ stock structure within the estuaries of southern Georgia. (poster presentation)
Barbieri, M. 2011. Understanding thermoregulatory physiology in a community of wild bottlenose dolphins and its implications for marine mammal population and ocean health. (invited plenary talk, F. G. Wood Memorial Scholarship Award)
Bassos-Hull, K., N. Adimey, C. Hudak, J. Powell, K. Minch and V. Socha. 2011. Entanglement hotspots along the Florida coastline: a need for outreach and action. (poster presentation)
Berens McCabe, E. J., A. Westgate and R. S. Wells. 2011. Prey energy density and bottlenose dolphin (/Tursiops truncatus/) foraging implications. (poster presentation)
Cammen, K., P. Rosel, R. Wells and A. Read. 2011. The influence of variation in voltage-gated sodium channel genes on susceptibility of bottlenose dolphins to harmful algal blooms. (oral presentation)
Hart, L.B., D.S. Rotstein, R.S. Wells, J. Allen, A. Barleycorn, B.C. Balmer, S.M. Lane, T. Speakman, E.S. Zolman, M. Stolen, W. McFee, T. Goldstein, T.K. Rowles and L.H. Schwacke. 2011. Skin lesion prevalence and type in common bottlenose dolphins (/Tursiops truncatus/) from waters near Sarasota, FL, Brunswick and Sapelo Island, GA, and Charleston, SC, USA. (oral presentation)
Macfarlane, N., L. Sayigh, V.M. Janik, T. Hurst, M. Johnson, R. Wells, P. Tyack. 2011. Tagging wild bottlenose dolphins (/Tursiops truncatus/) with digital acoustic recording tags (DTAGs). (poster presentation)
McHugh, K., L. Engleby, S. Horstman, J. Powell, R. Chesler, R. Hawkins, M. Salazar, B. Miller and R. Wells. 2011. To beg or not to beg? Testing the effectiveness of enforcement and education activities aimed at reducing human interactions at a hotspot near Sarasota Bay, Florida. (oral presentation)
Rossman, S.L., N.B. Barros, H. Gandhi, C.A. Stricker, P.H. Ostrom and R.S. Wells. 2011. Foraging ecology of bottlenose dolphins: a stable isotopic reconstruction over six decades. (oral presentation)
Schwacke, J., B. Balmer, B. Danielson, T. Rowles, K. Sparks, and L. Schwacke. 2011. Taskable wireless sensor network for VHF tracking of coastal and marine mammals. (oral – speed presentation)
Shippee, S.F., R.S. Wells, J.F. Luebke and T.K. Kirby. 2011. Evaluation of harmful interactions between bottlenose dolphins and sport fishing in Northwest Florida and Alabama. (poster presentation)