Physiological Effects of Low Salinity Exposure on Bottlenose Dolphins (Tursiops truncatus)

Bottlenose dolphins (Tursiops truncatus) have a worldwide distribution in temperate and tropical waters and often inhabit estuarine environments, indicating their ability to maintain homeostasis in low salinity for limited periods of time. Epidermal and biochemical changes associated with low salinity exposure have been documented in stranded bottlenose dolphins; however, these animals are often found severely debilitated or deceased and in poor condition. Dolphins in the U.S. Navy Marine Mammal Program travel globally, navigating varied environments comparable to those in which free-ranging dolphins are observed. A retrospective analysis was performed of medical records from 46 Navy dolphins and blood samples from 43 Navy dolphins exposed to a variety of salinity levels for different durations over 43 years (from 1967–2010). Blood values from samples collected during low salinity environmental exposure (salinity ranging from 0–30 parts per thousand (ppt) were compared to samples collected while those same animals were in a seawater environment (31–35 ppt). Epidermal changes associated with low salinity exposure were also assessed. Significant decreases in serum sodium, chloride, and calculated serum osmolality and significant increases in blood urea nitrogen and aldosterone were observed in blood samples collected during low salinity exposure. Epidermal changes were observed in 35% of the animals that spent time in low salinity waters. The prevalence of epidermal changes was inversely proportional to the level of salinity to which the animals were exposed. Future work is necessary to fully comprehend the impacts of low salinity exposure in bottlenose dolphins, but the physiological changes observed in this study will help improve our understanding of the upper limit of duration and the lower limit of salinity in which a bottlenose dolphin can maintain homeostasis.

[1]  Vanessa J. Mintzer,et al.  Short-term Effects of Hurricane Harvey on Bottlenose Dolphins (Tursiops truncatus) in Upper Galveston Bay, TX , 2020, Estuaries and Coasts.

[2]  R. Wells,et al.  Health Impacts and Recovery From Prolonged Freshwater Exposure in a Common Bottlenose Dolphin (Tursiops truncatus) , 2020, Frontiers in Veterinary Science.

[3]  H. Lillywhite,et al.  Drinking behaviors and water balance in marine vertebrates , 2019, Marine Biology.

[4]  D. Crocker,et al.  Comprehensive endocrine response to acute stress in the bottlenose dolphin from serum, blubber, and feces. , 2018, General and comparative endocrinology.

[5]  Per B. Brockhoff,et al.  lmerTest Package: Tests in Linear Mixed Effects Models , 2017 .

[6]  C. Manire,et al.  Evaluation of Serum for Pathophysiological Effects of Prolonged Low Salinity Water Exposure in Displaced Bottlenose Dolphins (Tursiops truncatus) , 2017, Front. Vet. Sci..

[7]  John R. White,et al.  Optimizing Sediment Diversion Operations: Working Group Recommendations for Integrating Complex Ecological and Social Landscape Interactions , 2017 .

[8]  Len Thomas,et al.  Survival, density, and abundance of common bottlenose dolphins in Barataria Bay (USA) following the Deepwater Horizon oil spill , 2017 .

[9]  Todd R. Speakman,et al.  Using salinity to identify common bottlenose dolphin habitat in Barataria Bay, Louisiana, USA , 2017 .

[10]  Hsin-yun Chang,et al.  Acid-Base , Electrolyte and Fluid Alterations : Review , 2016 .

[11]  C. Firth The Use of Photography to Monitor Dermal Disease in Wild Bottlenose Dolphins (Tursiops truncatus). , 2016 .

[12]  Mandy C. Tumlin,et al.  Adrenal Gland and Lung Lesions in Gulf of Mexico Common Bottlenose Dolphins (Tursiops truncatus) Found Dead following the Deepwater Horizon Oil Spill , 2015, PloS one.

[13]  Dorian Houser,et al.  Stress physiology in marine mammals: how well do they fit the terrestrial model? , 2015, Journal of Comparative Physiology B.

[14]  R. Sahay,et al.  Hyponatremia: A practical approach , 2014, Indian journal of endocrinology and metabolism.

[15]  D. Bates,et al.  Fitting Linear Mixed-Effects Models Using lme4 , 2014, 1406.5823.

[16]  Mandy C. Tumlin,et al.  Health of common bottlenose dolphins ( Tursiops truncatus ) in Barataria Bay, Louisiana, following the deepwater horizon oil spill. , 2014, Environmental science & technology.

[17]  Dorian S Houser,et al.  Cold Stress Induces an Adrenocortical Response in Bottlenose Dolphins (Tursiops truncatus) , 2011, Journal of zoo and wildlife medicine : official publication of the American Association of Zoo Veterinarians.

[18]  S. Ridgway,et al.  Effects of fresh and seawater ingestion on osmoregulation in Atlantic bottlenose dolphins (Tursiops truncatus) , 2009, Journal of Comparative Physiology B.

[19]  Stephanie Venn-Watson,et al.  Effects of age and sex on clinicopathologic reference ranges in a healthy managed Atlantic bottlenose dolphin population. , 2007, Journal of the American Veterinary Medical Association.

[20]  K. Schneider,et al.  Epidermal diseases in bottlenose dolphins: impacts of natural and anthropogenic factors , 1999, Proceedings of the Royal Society of London. Series B: Biological Sciences.

[21]  R. Ortiz,et al.  Osmoregulation in Wild and Captive West Indian Manatees (Trichechus manatus) , 1998, Physiological Zoology.

[22]  R. Kliegman,et al.  Hyponatremic seizures secondary to oral water intoxication in infancy: association with commercial bottled drinking water. , 1997, Pediatrics.

[23]  M. Guérin,et al.  For Calculating Osmolality, the Simplest Formula is the Best , 1987, Anaesthesia and intensive care.

[24]  S. Ridgway,et al.  Renin and Aldosterone Levels in Dolphins and Sea Lions 1 , 1978, Proceedings of the Society for Experimental Biology and Medicine. Society for Experimental Biology and Medicine.

[25]  S. Ridgway,et al.  Hematologic findings in certain small cetaceans. , 1970, Journal of the American Veterinary Medical Association.

[26]  L. Cornell,et al.  Do dolphins drink water? , 1970, Journal of the American Veterinary Medical Association.

[27]  S. Ridgway CHAPTER 10 – The Bottlenosed Dolphin in Biomedical Research , 1968 .