Plasma Vitamin Concentrations (α- and γ-Tocopherols, Retinol, Retinyl Palmitate, and Ascorbic Acid) in Two Free-Ranging Dolphin (Tursiops truncatus) Populations

Vitamins are essential for normal growth and development, metabolism, and immune health, yet there is limited knowledge on baseline values in marine mammals. Plasma samples were collected during 2003-2004 from two free-ranging dolphin populations (Charleston [CHS], South Carolina, n = 72; Indian River Lagoon [IRL], Florida, n = 79). Circulating levels of the following vitamins were analyzed: alpha- and gamma-tocopherols, retinol, retinyl palmitate, and ascorbic acid. Site-specific differences were observed for alpha-tocopherol, retinyl palmitate, and ascorbic acid, with higher levels occurring in CHS dolphins. Reference intervals (50th, 75th, and 90th percentiles) were calculated for each dolphin population. Higher levels of alpha-tocopherol were observed in CHS female dolphins compared to males (p = 0.05), with a similar trend observed in IRL. This study provides reference intervals for estuarine bottlenose dolphin (Tursiops truncatus) populations at two southeastern U.S. sites. Such data on baseline vitamin concentrations in wild populations are necessary prerequisites for understanding the impacts of contaminants or other disruptions of vitamin homeostasis on overall animal health.