The Physiological Consequences of Breath-Hold Diving in Marine Mammals, The Scholander Legacy
Authors: Andreas Fahlman (Topic Editor)
DOI / Source: https://doi.org/10.3389/fphys.2012.00473
Date: March 2013
Reading level: Intermediate
Why This Matters for Freedivers
Marine mammals are the “original deep divers,” and their physiology is basically a library of solutions to the same problems humans face: limited oxygen, pressure, and the need to stay functional under hypoxia. This collection also challenges a comforting myth—“lung collapse solves decompression issues”—and shows why gas and bubble risk can still matter, especially with repeated dives and certain behaviors.
Synopsis
This is a curated research collection (an edited “topic” ebook) focused on what lets marine mammals stay underwater for so long and dive so deep—and what modern science still doesn’t fully agree on, even after decades of study.
It starts from the classic Scholander legacy: the idea that breath-hold divers rely on a package of traits including a strong diving response (heart rate drop, blood flow redistribution), very large oxygen stores (blood, muscle, and lungs), smart movement strategies (like stroke-and-glide), and sometimes diving-induced reductions in metabolic cost. A key concept repeated throughout is the aerobic dive limit (ADL): how long an animal can dive before it must rely heavily on anaerobic metabolism. The collection discusses both “measured ADL” and “calculated ADL” (cADL), and highlights a real debate: do some species routinely exceed their calculated limits, or are our calculations missing usable oxygen stores or mis-estimating true metabolic costs during real foraging?
The diving response gets special attention—not just as a “slow heart rate” trick, but as a control system that may help ration oxygen between tissues. Several contributions explore how the brainstem controls these reflexes, how repeatable the response is, and what features may be heritable.
One of the most interesting themes is gas management and decompression. Scholander proposed that lung collapse at depth limits nitrogen uptake, reducing decompression sickness (DCS) risk. For years, that idea was often treated like a complete explanation. This collection pushes back: evidence from stranded whales and imaging studies suggests bubbles can occur, and under certain circumstances marine mammals may show DCS-like patterns. That opens new questions: are some species sometimes operating close to a “gas limit,” does repeated diving create nitrogen accumulation, and how do anatomy and behavior change risk?
The ebook also broadens beyond “just oxygen.” It includes work on spleen effects (blood storage and release), endocrine influences on dive metabolism, dietary fuel use (fatty acids and energetic efficiency), and how human divers compare to marine mammals in some of these traits.
Overall, this is less a single argument and more a guided tour of a living research field: what we’re confident about, what’s still debated, and what marine mammals can teach us about safe and efficient breath-hold diving.
Abstract
This edited research collection synthesizes current knowledge on the physiological responses that enable breath-hold diving in marine mammals, building on the foundational ideas of Scholander. Topics include the mammalian diving response and its control, oxygen-store management and the aerobic dive limit, behavioral strategies that reduce metabolic cost, and the role of lung collapse in limiting nitrogen uptake. The collection also highlights emerging evidence that inert gas bubbles can occur under certain circumstances, raising questions about decompression risk and gas-management limits in some species. Contributions span reviews and original research and include comparative perspectives relevant to human breath-hold divers.