Photic zone = sunlit region; depth ranges from 40 ft in murky waters to near 600 in tropics
Algae (produces 70% O2 on Earth), coral
First underwater habitats/contraptions → very dangerous, risk of “the bends”: actually because of pressurized environment of built structure, not of being so deep
Aquarius = one of last remaining oceanic research institutes not reliant on robots for exploration (at 60 feet)
Bring at high pressure for extended times → mild delirium from increased nitrogen in blood
-300
Something odd about being underwater that allows humans to withstand the pressures that should be impossible by Boyle’s Law— our lungs somehow don’t collapse
Similar in other animals: ducks, seals— “the biological functions of Weddell seals reverse in deep water; the seals… actually seemed to gain oxygen the longer and deeper they dove.”
Via decreased HR, lower vagus nerve stimulation, and peripheral vasoconstriction → shunting of blood to heart, brain, lungs (preventing collapse) = mammalian dive reflex, Master Switch of Life, triggered just by splashing cold water on your face, and more so the deeper you dive
At -40 feet freediving, effect of gravity seems to cancel out, buoyant force no longer pushing you up, pulling you down instead
Three stages of responses to lack of O2: 1) convulsions 2) release of oxygenated blood from the spleen 3) blacking out
Freedivers get familiar with feelings of these to know when to expect 1) and 2), avoid 3)
-300 ft = halfway to photic zone
Even for scuba divers, requires special gases to reach; long ascent time (not relevant for freedivers, bc normal air doesn’t have enough nitrogen to bubble into blood)
Still around the point where“Nitrogen narcosis affects more than just your brain; it affects your entire body. You lose motor control. Everything around you appears to slow down.”
Dark enough that most creatures rely on senses other than sight: bioluminescence, magnetoreception
-650
Disproportionate amount of shark attacks on island Réunion, near Madagascar
Mesopelagic (twilight) zone = 650-3300 ft below deep → only about 1% light at surface, not enough to support photosynthesis
Surprisingly, full of life: sea lily (“flower-shaped animal with a long stalk of a body and a crown of petal-like pinnules”)
“But here, when the searchlight was off, yellow and orange and red were unthinkable. The blue which filled all space admitted no thought of other colors.” (Beepe, early researcher of the mesopelagic)
1940s on, began tagging sharks with plastic or transmittable tags → spend much time there, precise migration paths
How do sharks navigate the dark waters?
Magnetoreception (also found in birds, insects , etc., and even humans); mechanism has something to do with deposits of magnetite found in beads/noses
In humans, strongest evidence = navigational capability of many indigenous people, ancient tribes; magnetite deposits in skull; more of an unconscious sense
Electroreception: ~1500 small bumps on their heads (ampullae) filled with electrically-conductive gel; cilia pick up changes in electric fields; by far the most sensitive sense known
-800
“No-limits” freediving → can reach depth by any means; most dangerous sport in the world
Weddell seals avoid decompression sickness by reflexively collapsing alveoli → limit uptake of air, including N2, in blood
Does this happen in humans too?
Ancient freediving cultures date from 2500 BCE
Ama: ancient culture of Japanese diving women, from around 500 BC
-1000
Humans have echolocation abilities too! (Sighted as well as blind people)
-2500
Bathypelagic zone = realm of pure and permanent blackness from 3,300 to 13,000 ft down; frigid & no sunlight
No diver—neither scuba nor freediver—has ever been down past 1,044 feet → explore bathtpelagic by ROV, submarine
Phytoplankton = microscopic algae, make up > 1/2 of biomass in the ocean, absorb up to 1/2 of world’s CO2 and produce more than 50 percent of Earth’s O2
Warming oceans → big loss of species diversity of phytoplankton → eventually will make it harder for us all to breathe
-10,000
Static tables = timed breath-hold exercises freedivers use to condition their bodies to tolerate high levels of CO2
Interval training: “breathe two minutes, take four huge breaths, hold breath for two minutes; breathe one and a half minutes, take four huge breaths, hold for two and a half minutes, and so on.”
Nice side effect = high of endorphins
Walking apnea: “You start by holding your breath while standing still for about thirty seconds until you feel your heart rate decrease, then you walk slowly in a straight line, turn around when you feel you’ve reached your halfway point, and walk back to your starting place. The distance you travel is about how far you’d be able to hold your breath during a deep dive.”
Sperm whales!
Can dive up to 10k ft deep; however, we can only study while (and other whales, dolphins, sharks) at surface
Freediving = only way to get close without interactions worse in the morning
Sperm whales have elaborate social structure, culture, “dialects,” very physically powerful (can feel their clicks)
“Human language is analogue; sperm whale language may“be digital.”
Whales and dolphins accumulate such high levels of PCBs and other pollutants that they can he considered “mobile SuperFund sites”
-35,850
Hadal zone: 20,000 to 35,859 ft → deepest zone, where even only 1% of floating particles end up reaching
Logistically extremely hard to research
Hadal zone trenches distributed like mountain ranges; not all contiguous
Surprisingly abundant and diverse forms of life, many though to be unique to their specific trench (diverged long ago)
James Corliss = one of the founders of deep sea research, discovered first hydrothermal vents
Vents spew water hot enough to melt lead, but doesn’t turn to gas bc pressure so high
Surrounded by chemosynthetic life forms — don’t use sun for energy, but chemicals from vents.. again, extremely diverse set of species
Crazy fact: “the deep pelagic realm, those waters from about 13,000 to 35,000 feet, housed the largest animal communities, the greatest number of individuals, and the broadest animal biodiversity of not only the ocean but any place on Earth.”
Hydrothermal vents = likely where life must have originated; perfect conditions to form organic molecules