Diving Physiology and Behavior

Diving Physiology and Behavior

Fundamental Constraint on Foraging Behavior Return to Surface to Breathe

Studies of Dive Behavior Dive depths from entanglements Observations Electronic developments instruments to measure diving

0 Sea otter Walrus Marine Mammal Diving Depths Otariids Phocids Odontocetes Mysticetes Dive depth (m) -500-1000 -1500-2000 -2500 Average Depth Max Depth

Diving Physiology I. Pressure effects II. Pressure diseases III. Breath hold diving

Pressure Effects Hydrostatic pressure pressure at depth due to weight of water column

Hydrostatic Pressure Depth (m) Pressure (Atms) Surface 1 10 2 20 3 30 4 40 5 50 6 100 11 500 51 1000 101 3000 301 Harbor seals, CA sea lions Elephant seals Sperm whales, beaked whales

Pressure Effects Hydrostatic pressure pressure at depth due to weight of water column Boyle's Law How pressure changes as function of depth Lung Collapse

Boyle s Law V 1 = P 2 V 2 P 1 P V V 1 P 1 = V 2 P 2

Change in Volume with Pressure 1/2 1/3 1/4

Lung Collapse Graded process 25 100m in all marine mammals

How Do Marine Mammals Deal With Lung Collapse? 1) Reinforced terminal airways & trachea - cartilage and muscle reinforcement

Lung collapse begins at alveoli and works up

Phocid Otariid Odobenid

How Do Marine Mammals Deal With Lung Collapse? 1) Reinforced terminal airways & trachea - cartilage and muscle reinforcement 2) Lung surfactants - reduces surface tension - produced in alveoli

Diving Physiology I. Pressure effects II. Pressure diseases III. Breath hold diving

Pressure Diseases Henry s law: pressure = solubility of gas in blood & tissues 1) N 2 narcosis Narcotic affect on CNS Humans: onset ~30m, loss of consciousness ~ 100m 2) O 2 toxicity - Toxic at high pressures - Causes: nausea, convulsion, death

Nitrogen Absorption

Field Measurement of Lung Collapse Weddell Seals

Dolphins trained to do repetitive dives Sampled blood Build up of N 2 occurred

Pressure Diseases 3) Decompression sickness Increase solubility at depth Gases saturated in tissues Form bubbles in tissue/joints on ascent

Pressure Diseases 3) Decompression sickness Increase solubility at depth Gasses saturated in tissues Form bubbles in tissue/joints on ascent 4) High pressure nervous syndrome (HPNS) Pressure causes changes in nerve function Cause tremors, seizures, and death

Direct Effects of Pressure 1) May change protein structure and function 2) Change enzyme kinetics 3) May influence viscosity of cell membranes

Adaptations to Pressure Deep Divers Dive on exhalation(?) Lung collapse Avoid O 2 toxicity N 2 narcosis? HPNS?? N 2 retention Pressure Squeeze Eliminate air spaces Shallow Divers Dive on inhalation Dive repetitively Decompression sickness Possible, Avoidance? Pressure Squeeze Eliminate air space

Diving Physiology I. Pressure effects II. Pressure diseases III. Breath hold diving

Marine Mammal Dive Duration 100 Average Maximum Dive duration (minutes) 10 1 Sea otter Sirenia Walrus Otariids Phocids Odontocetes Mysticetes

Breath Hold Diving Storing oxygen on board Lungs Muscle Blood Reduce oxygen usage Aerobic vs. Anaerobic metabolism

Early Studies Forced breath-hold experiments

Dive Response Extreme bradycardia Few beats per min Cardiac Output by up 90% Dramatic peripheral vasoconstriction Flow to heart lung and brain Muscles, GI tract, and other organs reduced Hypometabolism End of dive spike of lactic acid

Physiological Changes from Forced Dive

Breath Hold Diving Storing oxygen on board Lungs Muscle Blood Reduce oxygen usage Aerobic vs. Anaerobic metabolism

Increased O 2 Stores Lung O 2 stores Reduced in deep divers Important in shallow divers

Increased O 2 Stores Lung O 2 stores Reduced in deep divers Important in shallow divers Higher muscle O 2 Myoglobin: oxygen binding protein in muscle, similar to hemoglobin

Myoglobin in relation to dive times

Myoglobin in relation to dive duration

Increased O 2 Stores Lung O 2 stores Reduced in deep divers Important in shallow divers Higher muscle O 2 Myoglobin Higher Blood O 2 Larger blood volume Higher hematocrit Higher blood hemoglobin

Changes in the Distribution of Blood During Diving

Spleen contraction Increases circulating red blood cells (hematocrit)

Breath Hold Diving Storing oxygen on board Lungs Muscle Blood Reduce oxygen usage Aerobic vs. Anaerobic metabolism

Decrease Metabolism 1) body size

Larger animals use less energy per unit mass 1000 1:1 ratio 700 Oxygen stores 600 scale to 1.0 Metabolic rate (Watts) 100 10 Metabolic rate kg 0.75 Oxygen stores kg 1.0 500 400 300 200 100 Oxygen stores (Liters) 0 1 1 10 100 1000 10000 100000 Mass (kg)

Decrease Metabolism 1) body size 2) Swim efficiently, streamlining

Decrease Metabolism 1) body size 2) Swim efficiently, streamlining 3) Hypometabolism Vasoconstriction & redistribution of blood 50% of resting metabolism costs due to organs

Redistribution of Blood Flow

Decrease Metabolism 1) body size 2) Swim efficiently, streamlining 3) Hypometabolism Vasoconstriction & redistribution of blood 50% of resting metabolism costs due to organs Increased tolerance to hypoxia Bradycardia

Comparison of diving bradycardia in several species

Is The Dive Response Real? Forced dives No control over duration Maximum response (Fear) Natural dives Animals control duration, effort, oxygen use Graded response

Bradycardia

Field Studies

Breath Hold Diving Storing oxygen on board Lungs Muscle Blood Reduce oxygen usage Aerobic vs. Anaerobic metabolism

Biochemical Pathway of Metabolism Aerobic - Oxygen present - Produces 36-38 ATP Anaerobic - No oxygen - Produces only 2 ATP - Lactic acid produced

Aerobic Dive Limit (ADL): Amount of time an animal can hold its breath without an increase in lactic acid cadl (min) = O 2 stores (ml O 2 kg -1 ) Metabolic Rate (ml O 2 kg -1 min -1 )

Aerobic Dive Limit Phylogenetic differences: O 2 stores Diving Metabolic Rate Dive depths & durations

Aerobic Dive Limit Phylogenetic Differences Phocids Superb O 2 stores (60 ml O 2 kg -1 ) Low diving metabolic rate (1-2 x BMR) Otariids & Dolphins Good O 2 stores (40 ml O 2 kg -1 ) High diving metabolic rate (4-7 x BMR)

25 Role of Body Mass on Dive Time Phocids 1.4 x BMR Aerobic dive limit (minutes) 20 15 10 5 Phocids 2 x BMR Otariids 5 x BMR Dolphins 5 x BMR 0 0 200 400 600 800 1000 Body mass (kg)

Is The Dive Response Real? Forced dives No control over duration Maximum response (Fear) Natural dives Animals control duration, effort, oxygen use Graded response

Leptonychotes weddelli- Weddell seal

Weddell Seals on Fast Ice

Repeated blood, heart-rate, & metabolism measurements

McMurdo Sound 1977

Catching a Weddell seal

Dives less than 20 minutes No increase blood lactic acid Dives exceeding 20 min Postdive increase in blood lactate Increased with dive duration Dives less than 20 minutes Aerobic metabolism Within aerobic dive limit (ADL)

Comparison of postdive blood lactate concentration after forced submersions and natural dives Long natural dive Forced submersion Natural dives

Time-depth recorders (TDRs) were also deployed on freeranging seals in McMurdo Sound to determine the normal dive duration and depth. Kooyman-Billups TDR

Free-ranging Weddell seal TDR record

Dives from isolated hole Free-ranging dives

ADL 90-95% of all dives < 20 min

Ice Hole Experiments Dive response is graded Estimates of O 2 stores & cadl matched lactate measurements Most animals dive within estimated ADL More efficient diving strategy

Decrease in Lactic Acid with Time at Surface

20 min aerobic dive with 2 minute surface interval 2 4 6 8 10 12 14 20 40 60 80 100 120 140 160

20 min aerobic dive with 2 minute surface interval 2 4 6 8 10 12 14 20 40 60 80 100 120 140 160 100 60 60 min anaerobic dive with 100 minute surface interval

Why Dive Anaerobically? Can reach deeper depths Untapped resources Larger prey More continuous time at depth More time for pursuit Handling time

Understanding Diving Patterns in Nature 1983 1998

60 Relationship between O2 stores and dive times CSL 55 O 2 stores (ml O 2 kg -1 ) 50 45 CSL NZSL ASL AuFS R 2 = 0.69 40 AnFS 35 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5 Dive duration (minutes)

75 70 GaSL Total oxygen stores (ml O 2 kg -1 ) 65 60 55 50 45 40 R 2 =0.463 Ant FS CaSL AusSL CaSL Mex-winter NZ SL CaSLMex_Summer 35 0 1 2 3 4 5 Dive duration (minutes)

Most animals dive within their cadl 1.5 Antarctic fur seal Ratio of mean dive duration to cadl 1.0 0.5 r 2 = 0.54 0.0 10 15 20 25 30 35 Mean dive depth (meters)

Australian Sea Lion

Time (hours) 0 8 12 16 20 24 20 Dive depth (meters) 40 60 80 Australian Sea Lion A day in the life

7 Australian sea lions continuously exceed cadl 6 5 Dive duration (min) 4 3 2 1.2 x cadl 1 0 Mean cadl (2.3 min) 0 20 40 60 80 100 120 Dive depth (m)

Winter 1988 Time (hours:min) 12:00 12:06 12:12 12:18 12:24 12:30 0 0.8 1.0 1.0 1.3 2.2 1.2 2.7 3.7 3.2 3.0 3.0 3.0 3.3 20 Dive depth (meters) 40 60 1.5 2.5 2.0 2.0 1.8 2.0 2.3 80

Ratio of mean dive duration to cadl 2.5 2.0 1.5 1.0 0.5 Diving & Physiology differs between behaviors Australian sea lion Hookers sea lion Antarctic fur seal Australian fur seal CA sea lion mesoplealgic CA sea lion epipelagic cadl 0.0 0 20 40 60 80 100 120 140 160 180 200 Dive depth (meters)

Northern Elephant Seal

Tagging Beaked Whales

Dive Patterns Long Deep Foraging Dives Zc Ziphius cavirostris Shallow Recovery Dives Surface Time Md Mesoplodon densirostris

Mean Dive Duration (min) Allometry of Diving Dives >100m 20 Penguins, Pinnipeds, Odontocetes 15 Rorqual Whales 10 Humpback 5 Fin Blu e 0 0 1 2 3 4 5 6 Body mass (log kg)

Number of dives N = 7 whales Blue Whale - Dive Duration 30 N = 7 whales 20 10 Aerobic Dive Limit Minimum COT Standard MR 0 0 10 20 30 40 50 Dive time (min)

Physiology Is Not Always Limiting Prey distribution Depth Abundance Energy content Habitat limitations Bathymetry Seasonal productivity