Diving Physiology of Toothed Whales
Overview of Diving Physiology
Marine mammals are supremely adapted for their aquatic lives. Even though they are mammals like we are, some whales can perform dives to 3000 m (~2 miles) for almost 4 hours (Quick et al. 2020)!
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To accomplish this, whales deal with many physiological trade-offs. For example, atmospheric air is comprised of 78% nitrogen and 21% oxygen. Diving marine mammals want to maximize their oxygen storage, while minimizing nitrogen uptake; the former increases their dive time, while the latter can cause decompression injuries, similar to those observed in SCUBA divers with "the bends". ​
A common dolphin (Delphinus delphis) leaps from the water in the Pacific Ocean
Some species of whales have washed ashore with pathologies that actually resemble the bends. These instances often coincide in space and time with naval sonar activities. It is hypothesized that the acoustic disturbance alters diving behavior in a way that increases the risk of decompression injuries from nitrogen uptake.
My Master's Research
While the links between sonar and whale strandings are still under investigation, my Master's research at the University of North Carolina Wilmington looked specifically at the nitrogen solubility of whale fats. In other words, could whale fats that absorb a lot of nitrogen during a dive cause whales to experience decompression injuries when they alter their dive behavior in response to sonar?
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Toothed whales have unique fat depots in their heads, called "acoustic fats", that they rely on for echolocation. Different species of toothed whales have different types of lipids in these fats.
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Lonati et al. (2015) demonstrated that some toothed whale acoustic fats can absorb more nitrogen than others, based on species differences in lipid composition. Specifically, acoustic fats from pilot whales (Globicephala spp.) and beaked whales (Mesoplodon spp.) had higher nitrogen solubility, meaning that these species could have higher risks of developing decompression injuries.​
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This work was a small piece of the physiological puzzle of what is happening in a live, diving whale that is exposed to a disturbing stimulus. Since my 2015 publication, other work has shown that beaked whales may have fewer blood vessels in their acoustic fats to mitigate the uptake of nitrogen during their especially long, protracted dives (Gabler et al. 2018).
Graduating from UNC Wilmington in 2014 with an MSc in Marine Biology
