Could beaked whales get the bends?

Abstract

A mathematical model, based on current knowledge of gas exchange and physiology of marine mammals, was used to predict blood and tissue tension N 2 (P N 2 ) using field data from three beaked whale species: northern bottlenose whales, Cuvier's beaked whales, and Blainville's beaked whales. The objective was to determine if physiology (body mass, diving lung volume, dive response) or dive behaviour (dive depth and duration, changes in ascent rate, diel behaviour) would lead to differences in P N 2 levels and thereby decompression sickness (DCS) risk between species. Diving lung volume and extent of the dive response had a large effect on end-dive P N 2 .The dive profile had a larger influence on end-dive P N 2 than body mass differences between species. Despite diel changes in dive behaviour, P N 2 levels showed no consistent trend. Model output suggested that all three species live with tissue P N 2 levels that would cause a significant proportion of DCS cases in terrestrial mammals. Cuvier's beaked whale diving behaviour appears to put them at higher risk than the other species, which may explain their prevalence in strandings after the use of mid-frequency sonar.3

Body density and diving gas volume of the northern bottlenose whale (Hyperoodon ampullatus)

“…A small mass-specific diving lung volume of H. ampullatus , compared with that of delphinids (Piscitelli et al, 2013), may be selected as a smaller diving lung volume is predicted to increase the level of pulmonary shunt and thereby reduce nitrogen uptake during dives of beaked whales (Hooker et al, 2009). The cost of such a small diving lung volume in terms of oxygen store is minor as most of their oxygen is carried in blood hemoglobin and muscle myoglobin stores (Ponganis, 2011).…”

Respiratory Function in Voluntary Participating Patagonia Sea Lions (Otaria flavescens) in Sternal Recumbency

“…Thus, by not completely restoring the O 2 the animals minimize time spent at the surface and maximize time at depth (Kramer, 1988; Thompson and Fedak, 2001). However, this diving strategy is likely to cause gradual accumulation of CO 2 and/or N 2 with each subsequent dive, eventually forcing a prolonged surface interval or a period of very short and shallow dives (Scholander, 1940; Fahlman et al, 2009; Hooker et al, 2009). As a result, the management of O 2 may govern the duration of each dive and surface interval, while accumulation of CO 2 and/or N 2 may determine the duration of a bout.…”

“…Breath-by-breath analysis of gas exchange is a powerful tool to further understand how marine mammals manage gases during diving and has provided interesting results that provide information about what physiological variables that may limit diving (Reed et al, 1994, 2000; Boutilier et al, 2001). Studies using such methods would be useful to assess how changes in dive behavior and physiology may cause animals to exceed physiological limits that may cause gas bubble disease (Bostrom et al, 2008; Fahlman et al, 2009, 2014b; Fitz-Clarke, 2009; Hooker et al, 2009). …”

“…Modeling efforts may help increase the understanding how marine mammals respond to environmental change, but model results are affected by the quality of the data and the accuracy of the model assumptions. For example, a number of studies have attempted to model how the interaction between behavior, physiology, and environmental pressure affect the risk of decompression sickness during breath-hold diving (Houser et al, 2001; Zimmer and Tyack, 2007; Fahlman et al, 2009, 2014b; Fitz-Clarke, 2009; Hooker et al, 2009). The theoretical work performed on marine mammals used parameter estimates from terrestrial species or from marine mammals species that may be distantly related, i.e., Weddell seal vs. beaked whale.…”

Lung collapse in the diving sea lion: hold the nitrogen and save the oxygen

“…Recent modelling suggests that depth of lung collapse in seals and dolphins may be much deeper than estimated in earlier field studies [9,10]. Evidence for lung collapse (cessation of gas exchange) and estimation of its depth in free-diving animals are thus critical in the modelling of blood nitrogen uptake and distribution, and in the evaluation of the potential for decompression sickness in marine mammals [9,11,12], especially considering the reports of decompression sickness in deep-diving ziphiid whales stranded after exposure to naval sonar [11,13].…”