Hematology of Southern Beaufort Sea Polar Bears (2005–2007): Biomarker for an Arctic Ecosystem Health Sentinel

Abstract

Declines in sea-ice habitats have resulted in declining stature, productivity, and survival of polar bears in some regions. With continuing sea-ice declines, negative population effects are projected to expand throughout the polar bear's range. Precise causes of diminished polar bear life history performance are unknown, however, climate and sea-ice condition change are expected to adversely impact polar bear (Ursus maritimus) health and population dynamics. As apex predators in the Arctic, polar bears integrate the status of lower trophic levels and are therefore sentinels of ecosystem health. Arctic residents feed at the apex of the ecosystem, thus polar bears can serve as indicators of human health in the Arctic. Despite their value as indicators of ecosystem welfare, population-level health data for U.S. polar bears are lacking. We present hematological reference ranges for southern Beaufort Sea polar bears. Hematological parameters in southern Beaufort Sea polar bears varied by age, geographic location, and reproductive status. Total leukocytes, lymphocytes, monocytes, eosinophils, and serum immunoglobulin G were significantly greater in males than females. These measures were greater in nonlactating females ages ≥5, than lactating adult females ages ≥5, suggesting that females encumbered by young may be less resilient to new immune system challenges that may accompany ongoing climate change. Hematological values established here provide a necessary baseline for anticipated changes in health as arctic temperatures warm and sea-ice declines accelerate. Data suggest that females with dependent young may be most vulnerable to these changes and should therefore be a targeted cohort for monitoring in this sentinel.

Morbillivirus and Toxoplasma Exposure and Association with Hematological Parameters for Southern Beaufort Sea Polar Bears: Potential Response to Infectious Agents in a Sentinel Species

“…Methods for capture including location, blood sample processing, hematology, and cohort designations are described in Kirk et al, (2010). Blood was collected from the femoral vein or artery (Vacutainer; BD Biosciences, Franklin Lanes, NJ) into evacuated blood collection tubes for whole blood and serum, and PAXgene Blood RNA tubes (Qiagen, Valencia, CA) for RNA isolation.…”

“…For parameter pairs where correlations were significant (e.g., CDV titer and total leukocyte count), the difference between the mean of a given parameter for all CDV-positive animals and CDV-negative animals was determined. The resulting number was divided by the mean for that parameter for all CDV-negative animals and this number was converted to a percentage yielding ''percentage mean difference'' (Kirk et al, 2010). We compared mean CDV titers for seropositive bears in each age class using ANOVA and the post-hoc TukeyKramer test.…”

“…As described in Kirk et al, (2010), due to intimate ties with sea-ice and adaptation to a relatively ''disease free'' environment, polar bears are likely to confront a variety of new challenges related to climate change. These challenges may enhance their susceptibility to new and increasing numbers of pathogens.…”

Blood-based biomarkers of selenium and thyroid status indicate possible adverse biological effects of mercury and polychlorinated biphenyls in Southern Beaufort Sea polar bears

“…A total of 58 free-ranging SBS polar bears (31 males, 27 females) were captured by immobilization with Telazol (Warner–Lambert)-filled projectile darts fired from a helicopter during spring (March – May) 2007 in collaboration with the U.S. Geological Survey Ursid Research program as described previously (Bentzen et al 2008; Cardona-Marek et al 2009; Kirk et al 2010). Ten females were accompanied by cubs (cubs of the year to 2 year olds).…”

Characterization of blood lipoproteins and validation of cholesterol and triacylglycerol assays for free-ranging polar bears (Ursus maritimus)

“…5 However, it is also important to validate assays if logistics prevent immediate analysis and samples must be stored. Validations were performed with samples collected during ongoing studies of polar bears in the Southern Beaufort and Chukchi seas, Alaska, USA (details on capture and sample collection described elsewhere 10 ). Blood was collected from the femoral vein or artery in ethylenediamine tetra-acetic acid (EDTA) and no-additive containers, e centrifuged at 2,000 RCF for 10 min, then plasma or serum was siphoned into cryovials and stored at -20°C or -40°C until analysis.…”