Metabolic Concentration of Lipid Soluble Organochlorine Burdens in the Blubber of Southern Hemisphere Humpback Whales Through Migration and Fasting

Abstract

Southern hemisphere humpback whales undertake the longest migrations and associated periods of fasting of any mammal. Fluctuations in lipid energy stores are known to profoundly affect the toxicokinetics of lipophilic organochlorine compound (OC) burdens. Results from blubber biopsy sampling of adult, male humpback whales at two time points of the annual migration journey revealed dramatic concentration effects for the majority of OC compounds. The observed concentration effect was, however, not linear with measured average blubber lipid loss indicating significant redistribution of OCs and hence the importance of alternate lipid depots for meeting the energetic demands of the migration journey. Applying lipophilic OC burdens as novel tracers of whole-body lipid dynamics, the observed average concentration index suggests an average individual weight loss of 13% over 4 months of the migration journey. This value is based upon lipid derived energy and is in good agreement with previous weight prediction formulas. Notably, however, these estimates may greatly underestimate individual weight loss if significant protein catabolism occurs. Biomagnification factors between migrating southern hemisphere humpback whales and their principal prey item, Antarctic krill, closely resembled those of baleen whales feeding on herbivorous zooplankton in the Arctic. This study emphasizes the importance of considering prolonged periods of food deprivation when assessing chemical risks posed to wildlife. This is of particular importance for Polar biota adapted to extremes in ecosystem productivity.

The blubber adipocyte index: A nondestructive biomarker of adiposity in humpback whales (Megaptera novaeangliae)

“…If blubber lipid volume reduction is a reliable approximation of the corresponding reduction in blubber mass, this equates a 6.7% reduction in whale body mass between the two migration cohorts, as calculated using the empirical tissue weights applied in Bengtson Nash, Waugh, and Schlabach (2013b). …”

“…It is therefore not expected that a linear relationship between lipid loss from the outer blubber layer and whole‐of‐body adiposity exists, as indicated by the findings of Bengtson Nash et al. (2013b). This places an inherent limitation on the power of both blubber lipid‐percent and adipocyte metrics.…”

“…Late migration sampling events took place in September/October when the animals were returning to their feeding grounds after several months of fasting, and hence are assumed to have lower relative lipid reserves. The validity of this assumption has previously been demonstrated (Bengtson Nash et al., 2013a). All biopsies were obtained from 6‐m aluminium boat, using hollow‐tipped darts fired from a modified air rifle (Paxarms NZ).…”

Establishment of the first humpback whale fibroblast cell lines and their application in chemical risk assessment

“…Average population levels of individual POPs in SH humpback whale blubber have been observed to increase by up to 50 times between early and late migration (Bengtson Nash et al, 2013). Recently characterized POP profiles of SH humpback blubber revealed appreciable levels of chemical residues including para,para'-dichlorodiphenyldichloroethylene (p,p'-DDE) (Bengtson Nash et al, 2013), the main metabolite of the well-known insecticide, dichlorodiphenyltrichloroethane (DDT).…”

“…To date, only a few studies have addressed chemical burdens in southern hemisphere humpback whales (Bengtson Nash et al, 2013) or biomarkers of chemical effects in the species as a whole (Bengtson Nash et al, 2014, Jauniaux et al, 2011, Waugh et al, 2011. In other cetacean species, a number of cell lines have been developed in order to assess viral impact (Cecil and Nigrelli, 1970, Nielsen et al, 1989, Kadoi et al, 1992 and the effects of contaminants (Wang and Pfeiffer, 2001, Fossi et al, 2006, Li Chen et al, 2009, Carvan et al, 1995, Spinsanti et al, 2008, Wise et al, 2010, Gauthier et al, 1999, Pine et al, 2007.…”