Diving-tour operator Boone Hodgin in a moon jelly bloom. Courtesy D. Boone Hodgin

The divemaster and shark wrangler Daniel Boone Hodgin on tours near Prince William Sound’s Port Hidalgo unveils worlds seldom seen. Guests of Ravencroft Lodge, managed by his biologist-diver wife, Gina, snorkel with salmon, inspect iceberg bottoms, and gravitate through galaxies pulsing slower than human hearts: moon jelly blooms.

These jellies—infinitely more complex than the sandwich spreads—are invertebrates, specifically Medusae, jiggly umbrellas trailing tentacles like the snake tresses of the mythical Greek creature whose name they bear. “Medusa” is also their fast-growing, mobile phase, the occasional dolphin football derived from polyps coating dock undersides and seafloor rocks. Ethereal shapeshifters, moon jellies broadcast sperm nebulas females ingest. Fertilized eggs become furry Tic Tac larvae and later polyps, which morph into “strobila” stacks that jointly release blizzards of thousands of future medusae disc by delicate disc. 

Ocean currents corral blooms inside bays and inlets in depths unburdened by silt and glacier runoff where they suggest sunken islands. Hodgin first noticed those when bound for shark-diving sites. Now, locating such “smacks” through drones and by studying weather patterns, he guarantees sightings at Port Hidalgo. Frisbee flows up to half a mile wide, peaking in summer, remind him of auroras. The adult jellies’ hues range from milky-white to purple, depending on diet. They migrate to the surface each night, seining zooplankton, cloaked in transparency, feeding by touch. Spotlighted, caps with fiber-optics fringes and four mouth extensions or “oral arms” glow like blown glass against black, velvety space. Their guts and cloverleaf gonads pop as if X-ray vision were boosting the divers’ two superpowers, underwater breathing and flight. Each Chihuly bauble contracts its bell—the umbrella-shaped part—and, sucking in water, creates low-pressure zones filled by whirlpools that help propel it. Insights from this energy-efficient pumping improve vehicles and cardiac implants. 

Other Jellyfish Species

Yellow and orange jellyfish with many long tenticles
Lion’s mane or hairy jelly, the largest known species. Courtesy W. Carter, Wikimedia Commons

Hodgin’s divers watch burlier orange UFOs (Unbelievable Floating Objects) hover at bloom edges: lion’s mane jellyfish, with lobed bells up to six feet in diameter. Orbiting the column, they eclipse weak, lagging moons. Unlike their mildly venomous, saucer-size prey, the giants pack a punch. Hodgin, comparing their tentacles’ zap to bee stings, recommends approaching from the bell side. Immune, metallic fingerling fish in the limp rice-noodle snarl hitch rides around the ocean. The often hard-to-spot streamers of this subarctic species reach blue-whale lengths—100 feet—and launch mini-harpoons from capsules pressurized 75 times higher than car tires that inject toxin stunning susceptible fishes, crustaceans, and smaller jellies. These zingers, striking at 37 mph, are nature’s fastest cells. 

Long ignored, jellies mark frontiers of biotechnical and ecological research, holding keys to soft robots, especially unmanned subs. Comb jellies, when attacked, flash blue-green, running lights; beautifully named “luciferin” from ingested shrimps bonding with oxygen is responsible. Pliny the Elder, rubbing “jelly-glow” on his walking stick, repurposed it into a torch. Scientists highlight genes with the fluorescent protein for visual tracking and design firefly mice and Franken-fish pets. (You thought farmed salmon was bad?) Jellies sport this planet’s earliest eyes. A parasitic kind inhabits fish eggs. One, navigating by shore features, swims horizontally to offset currents. Another, when irritated, turns inside out. Females of a fourth emit chemicals that make males ejaculate simultaneously. 

Hodgin’s clients feel thrilled or at peace immersed in the submarine, slowed-down ballet. In one of his coolest and spookiest encounters, a salmon shark materialized out of a bloom. 

Concentrations of this most common Medusa bring trouble. They gum up fishing gear, ruin hauls, overrun aquafarms, and clog desalination plants and power station cooling systems, causing citywide blackouts. A trawler capsized when its crew pulled in nets with jellyfish outweighing gorillas. One moon jelly female carried over 400,000 larvae, and populations fluctuate wildly, annually, or as in the Bering Sea, about every decade. Sea nettles and fellow Medusae were 40 times more abundant there in 2000 than in 1982—fishermen learned to avoid a region called “Slime Bank.” Making matters worse, jellies gobble fish eggs and larvae together with zooplankton, which impacts commercial stocks. Blobby Gulf of Alaska drifters outcompete and prey on pollock, a cod relative. Jelly gluts deplete plankton banks, depriving fishes, whales, and crustaceans. Lastly, blooms luring drysuited divers elsewhere injure swimmers and litter beaches with Art Nouveau gunk leading to closures. Countermeasures include blockade nets, imported medusivores, “Jellycam” warning-systems, and automatic robot swarms shredding jellies then dispersed in the water. Fisheries for some species, however, supply Asian food markets and stores.

The Future of Jellies in Alaska

Two translucent jellyfish lit up in dark water
Moon jellyfish, the world’s most widespread species, are easily kept in aquaria. Courtesy Luc Viatour, Wikimedia Commons

Increases of alien and native jellies forecast for Alaska are among the highest, in sync with Antarctica’s. Incursions point to ecosystems already disturbed: Overfishing eliminates jellyfish predators. Rising temperatures from greenhouse gases perhaps contribute; unlike fish and other marine fauna, the prolific hemispheres thrive in warmer, low-oxygen “dead zones.”

They’ll stick around for a while too. Made of 95 percent water, largely unchanged for 500 million years, they’ve weathered five major extinctions, the biggest of which ended 90 percent of all life.

Moon jellies have an additional trick up their four sleeves. They normally live for six months but sometimes reverse their cycle miraculously and rejuvenate. Polyps can sprout from tissue fragments of banged-up, decaying, immature medusae or even from sexually mature, living individuals instead of from larvae. Take note, engineers of invasive-jelly meat-grinders. Your efforts might be Sisyphean.

Love or hate the elegant blebs—they serve one overt purpose: They ask us to heed the seas’ health. From Kenai to Ketchikan, their surging fleets evoke Earth’s fragile body.


Michael Engelhard is the author of Ice Bear: The Cultural History of an Arctic Icon. An inveterate cabin dweller, he lives in Fairbanks and works as a wilderness guide. Read more of his work at michaelengelhard.com and read Ice Bear here.

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