Facts About Life Below Water Global Goal

Facts About Life Below Water Global Goal

The ocean covers over 70% of our planet, yet much of this vast underwater realm remains unexplored and poorly understood. Life below water faces increasing pressures but also holds tremendous biodiversity we have yet to even discover. As citizens of Earth, we must expand our knowledge of the global seas that sustain us and act as stewards to protect marine ecosystems. This World Oceans Day, let us reflect on how little we know about the ocean depths and commit to conserving life in our shared waters.

50 Amazing Facts About Life in Our Oceans – The Rich Biodiversity Below Water and Why We Must Protect It

Here are 50 fascinating facts about the astounding diversity of life below water and why it matters:

  1. Coral reefs contain over 25% of all marine species but cover only 0.1% of the ocean floor.
  2. The longest animal in the world is the lion’s mane jellyfish, with tentacles reaching over 120 feet.
  3. Lanternfish account for an estimated 65% of all deep-sea fish biomass. Their name comes from the rows of photophores they use to illuminate the darkness.
  4. The loudest animal in the world is the pistol shrimp, whose snap can reach over 200 decibels. The resulting shockwave can stun or even kill small prey.
  5. Seahorses are the only animal where males get pregnant and give birth to the young. Females deposit eggs in a male’s brood pouch where they gestate until birth.
  6. Greenland sharks have the longest known lifespan of any vertebrate on Earth at over 400 years.
  7. Octopuses have three hearts, blue blood, and arms that can regrow if lost. Their brains are highly complex, on par with many mammals.
  8. The largest migration in the world is the vertical community migration that occurs in oceans daily. Trillions of organisms ascend and descend through the water column.
  9. Bioluminescence has evolved in over 700 genera of marine organisms using various biochemical pathways to produce light.
  10. Whale sharks are the largest fish in the world and can reach lengths over 40 feet, yet their diet consists only of plankton.
  11. The Mariana Trench in the Pacific Ocean includes the deepest point on Earth’s surface, Challenger Deep, at nearly 36,000 feet down.
  12. Giant tube worms discovered at hydrothermal vents survive without sunlight, instead getting energy from symbiotic bacteria.
  13. Gray whales make the longest migration of any mammal, swimming over 10,000 miles round trip between feeding and breeding grounds each year.
  14. Orca vocalizations are sophisticated enough to be considered a distinct language with family-specific dialects.
  15. The coconut crab is the largest land invertebrate in the world based on weight, reaching over 9 pounds. But it still requires the ocean to breed.
  16. Coral polyps that build reefs are tiny, often no larger than a pinhead, but can live centuries and create massive structures over generations.
  17. Krill are shrimp-like planktonic creatures that swarm in huge numbers. They likely make up the largest total biomass of any multi-cellular animal species.
  18. The mutable rainbow wrasse can change sex from female to male as it grows older. Sex changes help balance population dynamics.
  19. Sea otters hold hands while sleeping to keep from drifting apart. They float together in “rafts” of up to 100 otters.
  20. The leafy sea dragon uses camouflage and mimicry to disappear against seaweed. They are related to seahorses and pipefish.
  21. Albatrosses can glide hundreds of miles each day without flapping their wings using a technique called dynamic soaring.
  22. No sharks have true bones. Their skeletons are made of cartilage, the same flexible tissue found in human noses and ears.
  23. Antarctica’s waters harbor more species than the tropical Caribbean, including over 235 unique fish adapted to the cold.
  24. The venom of a single cone snail can kill dozens of adults within hours, making them one of the ocean’s deadliest creatures.
  25. Sunfish hold the record as the heaviest bony fish, reaching weights of over 5,000 pounds.
  26. The ocean has absorbed over 90% of the excess heat trapped by increased atmospheric greenhouse gases.
  27. Pacific bluefin tuna can swim over 50 miles per hour, making them one of the fastest fish. They’re also severely overfished.
  28. Some sharks like the Greenland shark have parasites in their eyes that feed on corneal tissue. The sharks tolerate this because parasites also emit bioluminescence.
  29. Sea cucumbers breathe and feed by drawing seawater in through their rear end and out through tentacles around their mouth.
  30. Fish like groupers and moray eels cooperate with each other while hunting, showing surprising interspecies communication.
  31. Corals themselves are translucent animals that appear colorful due to microscopic algae called zooxanthellae living symbiotically within their tissues.
  32. Polar bears rely on sea ice to hunt seals at the water’s edge. Declining ice from climate change threatens their Arctic habitat.
  33. Fish that live at great depths like the fangtooth fish have evolved huge mouths and teeth to grab any prey they encounter in constant darkness.
  34. Penguins preen themselves to waterproof and maintain their feathers using an oil secretion from a gland near their tails.
  35. Whales, dolphins and porpoises are collectively called cetaceans. Toothed whales actively echolocate while baleen whales filter feed.
  36. Marine plankton like copepods and krill form the basis of most ocean food webs. Their photosynthesis provides over half the world’s oxygen.
  37. The ocean has lost about 40% of phytoplankton since 1950, in part due to warming waters from climate change.
  38. Fish like clownfish form symbiotic relationships with sea anemones, gaining protection while providing the anemones with nutrients from their waste.
  39. Estuaries where rivers meet the sea contain brackish water and unique ecological gradients supporting high levels of biodiversity.
  40. Sperm whales can dive over 3,000 feet deep and stay submerged for over an hour hunting giant squid in lightless waters.
  41. Horseshoe crabs have existed essentially unchanged for over 450 million years and donate their copper-rich blood for medical testing.
  42. North Atlantic right whales are critically endangered with only about 340 individuals left alive today. Ship strikes and fishing gear entanglements threaten them.
  43. Sea slugs like nudibranchs display some of the most vibrant colors and patterns in the ocean, warning predators of their toxic or unpalatable flesh.
  44. Over 8 million tons of plastic enter the ocean each year. It breaks down into microplastics eaten by marine life, accumulating up the food chain.
  45. Deep sea anglerfish females are several times larger than males. The tiny males permanently fuse to a female after finding her.
  46. The longest recorded animal was a 150 foot siphonophore discovered in the Ningaloo Canyon off Australia in 2020.
  47. Stony corals and soft corals evolved from relatives over 500 million years ago and now have very different anatomies.
  48. Oceans absorb about 22 million tons of carbon dioxide per day from the atmosphere, helping regulate climate and pH balance.
  49. The percentage of marine species likely to be threatened by mid-century could range from nearly 10% for seaweeds to over 70% for shallow corals if climate change continues unabated.
  50. Less than 15% of the world’s oceans currently fall within marine protected areas. Reaching the global target of 30% protection by 2030 will help safeguard biodiversity.

The incredible diversity of life below water remains mostly unexplored, with new species constantly being discovered even in familiar groups like fish, corals, and squid. This biological wealth expands our understanding of life’s creativity.

Yet human actions now threaten marine realms that have endured for millennia. With increased knowledge, care, and effort worldwide, we can protect the waters that give our planet vitality. Our lives depend on cultivating resilience across the interconnected ocean.

What percentage of the planet’s surface is covered by the ocean?

Approximately 70% of the Earth’s surface is covered by ocean, which contains about 97% of all water on the planet. The five major oceans are the Pacific, Atlantic, Indian, Southern, and Arctic. Together they comprise one continuous global ocean system that dominates the planet.

The vast scale of the oceans profoundly influences planetary systems like climate, weather patterns, and carbon cycling. Given its central importance, understanding and protecting the marine environment is critical for all life on Earth.

2. How many species live in coral reefs compared to the entire ocean floor area?

Coral reefs cover less than 0.1% of the ocean floor, yet they contain over 25% of all marine species. The incredibly biodiverse coral reefs support up to 2 million species despite their small area. In contrast, the remaining 99.9% of the seafloor habitats likely contain only about 2.2 million species.

This means coral reefs support a hugely disproportionate amount of biodiversity and genetic variety on the planet in a very compact area. Protecting these highly productive but fragile ecosystems is key to preserving marine life.

3. What is the longest animal that lives in the ocean?

The longest ocean animal is the lion’s mane jellyfish, with tentacles that can extend over 120 feet (36 meters) long. That’s longer than a blue whale! The lion’s mane lives in cold water habitats like the Arctic, northern Atlantic and northern Pacific.

It uses its many long tentacles to capture prey like fish and plankton. While not inherently dangerous, their stings can cause reactions in humans. But their long, trailing tentacles showcase one amazing adaptation marine life has evolved.

4. What small planktonic creature accounts for the majority of deep sea fish biomass?

In the deep scattering layer around 984-3,281 feet (300-1,000 m) down, a tiny planktonic crustacean called copepods dominates the fish biomass. Though individual copepods are under 2 mm long, they exist in astronomical numbers and represent the majority of fish diet in the deep sea, forming vital food chains.

Species like lanternfish and bristlemouths migrate vertically to feed on copepod swarms. Copepods thus enable the huge fish biomass supported in the otherwise food-limited open ocean.

5. Which ocean creature has the loudest snap or vocalization?

The pistol shrimp generates an incredibly loud snap of its enlarged claw, reaching over 200 decibels. This is among the loudest sounds in nature. The snap comes from a specialized claw that can shoot a jet of water so fast that bubbles implode, creating a cavitation shockwave that stuns prey.

Fish and invertebrates up to 6 feet away can be stunned or even killed by the pistol shrimp’s shockwave “shot”. No other ocean creature matches this intense shock-bubble snap.

6. Which ocean species exhibits male pregnancy and birth?

Seahorses exhibit an unusual reversal where the male gets pregnant and gives birth to the young. The female seahorse deposits her eggs into the male’s brood pouch. Here the eggs are fertilized and embed in tissue lining the pouch.

The embryos develop until the male seahorse undergoes labor and “births” tiny seahorses into the water through muscle contractions and relaxing the pouch. Seahorse fathers provide all prenatal care, protecting the eggs and providing nutrients and oxygen until birth.

7. What is the longest living vertebrate species on Earth?

The Greenland shark has the longest known lifespan of all vertebrates, with radiocarbon dating estimating ages over 400 years old. These slow-growing deepwater sharks inhabit Arctic and North Atlantic oceans. They grow about 1 cm per year and don’t reach sexual maturity until about age 150.

Their longevity and delayed reproduction are adaptations to frigid, food-scarce habitats. But it makes them very vulnerable to human pressures like fishing. Losing such long-lived marine species represents an incalculable loss.

8. How many hearts does an octopus have?

Unlike us, octopuses have three hearts. Two pump blood to the gills, while a larger central heart circulates oxygenated blood to the body. Octopus blood uses the copper-rich protein hemocyanin rather than iron-based hemoglobin to transport oxygen.

And the blood itself is blue rather than red. The three hearts and blue blood are just some of the bizarre traits that make octopuses such alien yet fascinating creatures of the sea.

9. What is the largest daily migration in terms of numbers of organisms?

The largest migration occurs vertically in the ocean daily as organisms move up and down through different depths. Trillions of marine animals, primarily zooplankton, migrate from deeper, darker waters during the day to feed in shallow surface waters at night, then retreat back down before dawn.

Species involved range from copepods to krill to jellyfish. This huge community migration happens across the global oceans, cycling organic material and nutrients through the water column each day.

10. How many genera of ocean species are estimated to be bioluminescent?

Bioluminescence has evolved in an estimated 700 genera of ocean organisms, with the capability arising from different molecular pathways. Bioluminescence involves creatures generating their own light through chemical reactions.

Fireflies demonstrate this ability on land. But marine bioluminescence occurs on a vast scale, transforming the sea into a sparkling watery light show. Jellyfish, fish, shrimp, squid, algae and bacteria all commonly exhibit bioluminescence in the ocean’s dark depths.

11. What is the largest fish species in the world by length?

The whale shark is the largest fish, reaching lengths of over 40 feet (12 meters) and weighing up to 20 tons. This gigantic shark inhabits warm tropical waters around the world. It is a docile filter feeder, consuming only tiny plankton during its slow roams.

The spotted patterns on each whale shark are unique, helping researchers identify and track individuals through photo identification. Protecting these gentle ocean giants from fishing activity and ship strikes is an important conservation goal.

12. Where on Earth is the deepest point, the Challenger Deep, located?

The deepest point on Earth lies in the Mariana Trench in the western Pacific Ocean. This lowest point, called the Challenger Deep, reaches a maximum depth of approximately 36,200 feet (11,000 meters) below sea level. For comparison, Mount Everest is about 29,000 feet tall.

Only a few humans have ever visited this extreme depth. At such crushing pressures and cold, perpetual darkness, the conditions at Challenger Deep push marine life to the limits of adaptability.

13. What bizarre deep sea creatures survive using symbiotic bacteria instead of sunlight?

At hydrothermal vents on the seafloor, unique organisms thrive in total darkness through chemosynthesis with symbiotic bacteria instead of photosynthesis. These include giant tube worms, clams, and pale crabs with bacteria living inside them.

The bacteria oxidize chemicals like hydrogen sulfide and provide food for their animal hosts, enabling ecosystems without sunlight. Scientists didn’t know such “alien” life forms existed until vents were first discovered in 1977. They expand our concepts of where and how life can survive.

14. Which mammal makes the longest migratory journey every year?

The gray whale migrates over 10,000 miles (16,000 km) round trip each year, the longest migration of any mammal on Earth. Gray whales feed in northern seas then migrate south to breed in warm lagoons of Baja California and the Gulf of California from late fall through early spring.

Mothers make the trip while pregnant, then return north with their new calves. Human activity all along their coastal migration routes threatens the survival of these hardy travelers and their newborn calves.

15. What evidence suggests orca vocalizations may qualify as a language?

Orcas produce sophisticated vocalizations indicating complex communication and even distinct cultural heritages. Different groups use unique calls comprising dialects that juveniles learn from elders. Calls are structured with syntax and vary contextually.

Family pods also make group-specific calls, with nouns referring to individuals. And orcas can imitate novel sounds, indicating creativity. This complexity suggests orca communication qualifies on key criteria for language – a level of abstraction rare in the animal kingdom.

16. Which large land invertebrate requires the ocean to breed?

The coconut crab is the largest terrestrial arthropod, reaching over 9 pounds in weight. But despite living mostly on land, coconut crabs require the ocean to breed. Females migrate to the sea to release their eggs into the water.

Larval coconut crabs then develop offshore before returning to land. Adults subsist far inland eating fruits and nuts. Their ocean-reliant reproduction and landward adult life showcase the interconnectedness of marine and terrestrial ecosystems.

17. How big are coral polyps that construct reefs?

Coral polyps are tiny, often measuring only 3 to 4 mm across (0.1 inches), no larger than a pencil eraser. But these tiny invertebrates secrete calcium carbonate exoskeletons. Over generations, the accumulated skeletons of coral colonies form the enormous limestone structures we know as coral reefs.

The Great Barrier Reef contains over 600 types of coral polyps building on previous generations’ efforts. Tiny polyps working together create the largest living structure on Earth.

18. What shrimp-like zooplankton likely makes up the largest ocean animal biomass?

Krill, small shrimp-like crustaceans, likely comprise the largest total biomass of any individual multi-cellular animal species on Earth. Though only about 6 cm long as adults, krill occur in huge swarms across the oceans.

Their total numbers may weigh over 500 million metric tons in mass. Krill congregate in dense schools and serve as a vital food source for fish, penguins, whales and other ocean life. Protecting productive krill populations is important for supporting ocean food webs.

19. Which colorful reef fish can change sex as it ages?

Many wrasses exhibit sequential hermaphroditism, meaning they can change sex from female to male as they age. This ability benefits mating dynamics in fish species where males dominate harems.

The California sheephead wrasse offers an example. Larger, older males maintain territories and mate with females. When a male dies, the largest female transforms into a fertile male to take its place. Sex changes thus ensure breeding males are present to fertilize the females they allow into their harems.

20. How do sea otters keep from drifting apart while sleeping?

Sea otters frequently wrap themselves in giant kelp fronds while sleeping at the water’s surface. But they also hold hands in large groups called rafts to keep from floating apart while resting. Sea otter moms hold pups on their bellies too.

Otters may link together in a huge ring of dozens to hundreds of individuals. Their hand holding behavior is extremely rare among marine mammals. It showcases both their tight social bonds and adaptation to an aquatic environment.

21. How does the leafy sea dragon camouflage itself?

The leafy sea dragon uses extensive camouflage to disappear against seaweed in its habitat along southern Australia. Its entire body is covered in leaf-like protrusions that sway and provide camouflage within seaweed beds where it hides.

The leafy sea dragon’s shape and coloring precisely mimic surrounding algae and seaweed. This masterful disguise helps protect it from visual predators like larger fish. Its unique adaptations showcase evolution’s creativity in matching marine creatures to their environment.

22. What technique helps the albatross glide long distances without flapping?

Albatrosses use a strategy called dynamic soaring to travel immense distances while barely flapping their wings. This involves angling their wings to harness differences in wind speed near the ocean surface.

The albatross gains momentum from faster winds then swoops upward into slower air, creating lift. Angling into the wind gradient allows “free” momentum gain. Mastering this skill lets albatrosses glide hundreds of miles per day searching for patchy prey like squid.

23. What material comprises shark skeletons instead of true bone?

Sharks’ skeletons are made of cartilage rather than true bone. Shark cartilage is flexible and less dense than bone, reducing the sharks’ weight for more efficient swimming. Their jaws are not fused for even greater bite strength.

The large liver also provides necessary buoyancy. Sharks continually shed teeth, replacing them from conveyor belt-like rows of new teeth. Cartilage skeletons make sharks lighter, nimbler marine predators, though fossilize poorly compared to bony fish.

24. Which polar region harbors more fish species than the tropics?

Surprisingly, the waters around Antarctica support more fish species than the tropical Caribbean, with an estimated 235 unique species just among bony fish around Antarctica. Contrary to expectations about biodiversity decreasing toward the poles, Antarctica’s long isolation and varying conditions have led to high speciation.

Many Antarctic fish have evolved specialized adaptations like antifreeze proteins that allow them to thrive in frigid, ice-laden waters. The richness of Antarctic marine life remains underestimated and vulnerable to climate change.

25. What makes cone snails one of the ocean’s deadliest creatures?

Cone snails seem innocuous but in fact are highly venomous, with toxins so potent they can kill a human within hours. These small marine snails fire harpoon-like teeth loaded with venom to paralyze and subdue prey like fish.

A single drop can contain enough neurotoxin to kill 10 people. Of over 800 cone snail species, the geography cone is the most toxic. But stings from any species should receive urgent medical care. Cone snails showcase the surprising risks that may lurk in the ocean’s beauty.

26. Which fish species holds the record as the heaviest bony fish?

The ocean sunfish holds the record as the world’s heaviest bony fish, with the largest individuals reaching weights over 5,000 pounds (2,268 kg). Yet sunfish feed primarily on jellyfish and can’t survive in captivity.

Their hefty size comes from a compressed, shortened body and extraordinarily slow growth. Sunfish move by flapping large dorsal and anal fins, exposing their massive bulk above water. Despite their weight, they are docile, posing little danger to humans who encounter them.

27. What percentage of excess atmospheric heat has the ocean absorbed?

Over 90% of the excess heat from greenhouse gas forcing has been absorbed by the ocean, rather than air or land. Sea surface temperatures have warmed on average over 0.9°C since pre-industrial times as a result.

This ocean heat uptake slows the rate of atmospheric warming but alters marine conditions, fueling sea level rise through thermal expansion and melting ice sheets and glaciers. A warmer, more acidic and less oxygenated ocean threatens many organisms and ecosystems, especially coral reefs.

28. How fast can the fastest ocean fish like the tuna swim?

Some of the fastest ocean fish are sailfish and marlins, but Pacific bluefin tuna may reach peak swimming speeds over 50 miles per hour (80 km/hr), among the highest for fish. Their torpedo-shaped, rigid bodies and lunate tails optimize hydrodynamic movement.

These lightning-fast hunters pursue prey like squid, mackerel, salmon and sardines. But their swift speed and late reproductive maturity make bluefin extremely susceptible to overfishing. Their global numbers have plunged over 96% in recent decades as demand for luxury sushi has boomed.

29. Why do some sharks tolerate parasites feeding on their eyes?

Greenland sharks tolerate parasitic copepods (ommatokoita elongata) that attach and feed on their corneas. These small parasites eat the sharks’ corneal tissues and leave a large opaque scar.

But the sharks do little to remove the blinding parasites because they also emit light. The bioluminescence attracts more prey toward the sharks in deep, dark Arctic waters where they hunt. The sharks seem to accept the cost of blindness to gain a hunting advantage. This bizarre symbiosis reveals ocean adaptations we are still discovering.

30. How do sea cucumbers breathe and feed?

Sea cucumbers are echinoderms that breathe and feed by drawing water into their bodies through a siphon near their rear, then expelling it from a ring of tentacles around their mouths.

As water passes over these rings of tentacles, they capture plankton and organic particles, while absorbing oxygen from the flowing water internally. Sea cucumbers can rapidly contract their bodies if threatened. They help recycle nutrients and keep seafloor sediments clean and oxygenated through their feeding.

31. What makes corals appear brightly colored?

Corals themselves are clear or translucent animals. Their striking colors come from microscopic algae called zooxanthellae that live symbiotically within their tissues. The algae undergo photosynthesis to produce energy, and in return provide the coral with organic carbon compounds.

Zooxanthellae also impart the vibrant colors we associate with coral reefs. Unfortunately, stressed corals expel these algae, causing them to turn pale white in a process called coral bleaching as their health declines.

32. What crucial Arctic habitat is threatened for polar bears by climate change?

Polar bears depend on sea ice as a platform to reach their prey of seals. But declining Arctic sea ice from climate change threatens their ability to hunt. As sea ice retreats further from coasts and melts earlier in summer, polar bears are forced ashore for longer periods, fasting until freeze-up lets them roam the ice again.

The lack of sea ice habitat puts pressure on all aspects of polar bear survival. Preserving the icy ecosystems they rely on is crucial for polar bear conservation.

33. How have some deep sea fish species evolved to survive in constant darkness?

Many deep sea fish have evolved huge mouths, distensible stomachs, and hinged jaws to help them swallow any prey they encounter in constant darkness. Many also have bioluminescent lures to attract prey.

Their large gaps allow them to consume prey nearly their own size. With so little food in the abyssal depths, it helps to grab anything edible. Outsize proportions and bioluminescent adaptations help deep sea fish survive in pitch-black conditions where food is perpetually scarce.

34. How do penguins waterproof and maintain their feathers?

Penguins’ multilayered, scale-like feathers trap air for insulation and repel water. To maintain waterproofing, penguins preen frequently, spreading waterproofing oils from a gland near their tails over feathers. Preen oil also helps keep feathers flexible in frigid conditions.

What are the two major groups of marine mammals?

Marine mammals include members of the cetacean and pinniped families. Cetaceans include whales, dolphins, and porpoises. These are divided into baleen whales that filter feed, and toothed whales that actively hunt prey.

Pinnipeds include seals, sea lions, and walruses. These fin-footed semi-aquatic mammals rely on blubber for insulation in cold waters. Protecting marine mammals is crucial but challenging due to their vast migrations and recurrent need to surface for air.

36. What tiny planktonic organisms produce over half the oxygen we breathe?

Phytoplankton are microscopic, single-celled algae and cyanobacteria that inhabit sunlit ocean waters. Through photosynthesis, these marine plants produce over half the world’s oxygen, far more than land plants.

The most common phytoplankton are diatoms and dinoflagellates. Blooms of these plankton support the entire ocean food web. But warmer, more acidic, and lower-oxygen conditions threaten phytoplankton. Since we depend on them for every second breath, protecting phytoplankton is self-preservation.

37. What percentage decline in phytoplankton has occurred since 1950?

Studies suggest the global abundance of marine phytoplankton has declined around 40% on average since 1950. Local seasonal drops of over 60% have been observed in some areas. Rising ocean temperatures, acidification, nutrient runoff, and large-scale cycles all exert pressure.

This disturbing drop in tiny ocean plants threatens marine food webs and atmospheric oxygen. Urgent action is needed to halt contributing factors and better monitor plankton levels worldwide.

38. What kind of symbiotic relationship do clownfish have with sea anemones?

Clownfish form a mutualistic relationship with certain sea anemones like the carpet anemone. The anemone’s stinging tentacles protect clownfish from predators. In return, clownfish defend the anemones from fish like butterflyfish that eat tentacles, and their waste provides nutrients.

A mucus coating on clownfish likely offers some immunity to the anemone’s stings. This interdependency showcases the cooperative relationships that have evolved between reef species.

39. What unique habitats are formed where rivers meet the sea?

The mixing zone where freshwater rivers and streams meet the ocean forms a unique brackish water ecosystem called an estuary. Estuaries contain gradients of salinity, nutrients, and sediments that support highly diverse plant and animal communities.

These sheltered, productive habitats are nursery grounds for many fish, migratory birds and invertebrates. But estuaries are also impacted by human settlement and vulnerable to pollution. Protecting these fragile interfaces between land and sea preserves irreplaceable biodiversity.

40. How deep can sperm whales dive and for how long can they hold their breath?

Sperm whales are the deepest diving mammals, capable of plunging over 3,000 feet (1,000 m) and remaining submerged for over an hour stalking giant squid in lightless conditions. Their large oil-filled spermaceti organ acts as an acoustic lens while echolocating.

It also adjusts their buoyancy. Sperm whales have the largest brains of any animal but their deep-diving physiology and behavior remain barely studied. We have only scratched the surface of understanding these ocean leviathans.

41. Why is horseshoe crab blood especially valuable for medical testing?

Horseshoe crab blood contains amebocytes that coagulate around pathogens, making it exceptionally sensitive for detecting bacterial endotoxins. This unique property has made harvesting their copper-rich blood integral to medical testing for contamination.

Over 250,000 crabs per year are captured and 30% of their blood drained before being released alive. Conservation focuses on reducing mortality from this process. No synthesized substitute has yet matched the crab blood’s reliability for detecting threats down to parts per trillion.

42. What key threats face the highly endangered North Atlantic right whales?

North Atlantic right whales number only about 340 individuals still alive. Their two main threats are ship strikes and entanglement in fishing gear. Their coastal migrations bring them into contact with heavy maritime traffic and lobster pot lines.

Over 85% of right whales have scars from entanglements, which can drown them or impair feeding and reproduction. Conservation efforts aim to reroute shipping lanes and transition to ropeless fishing gear in critical habitats. More drastic protections may be needed to save these highly imperiled whales.

43. Why are some sea slugs like nudibranchs so vibrantly colored?

Sea slugs like nudibranchs display some of the most brilliant colors in the ocean, vividly striped, spotted and frilled. Their bright patterns advertise toxicity to warn predators. Nudibranchs incorporate stinging cells from prey like jellyfish into their own tissues for protection.

Vibrant contrasts also help nudibranchs camouflage against similarly colorful coral reefs and sea slug egg ribbons. Finally, they may help nudibranchs find mates. Their vivid hues are both aesthetic and entirely functional for survival in the ocean’s fierce competition.

44. How many tons of plastic enter the ocean each year?

Current estimates suggest over 8 million metric tons of plastic waste enters the world’s oceans every year globally. Microplastics less than 5 mm in size are of greatest concern, as marine organisms easily ingest these tiny fragments.

Plastics accumulate up the food chain, impacting marine megafauna like whales and tuna. About 269,000 tons float on the ocean’s surface, while an estimated 4 billion plastic microfibers per square kilometer litter the deep sea globally based on sediment samples.

45. How do deep sea anglerfish males find and mate with much larger females?

In deep ocean anglerfish, tiny males seek out and permanently fuse to much larger females. This extreme sexual dimorphism makes finding mates very difficult in the abyssal darkness. To solve this, males use highly developed scent organs to track down females.

Once a male finds a female, he latches on with his teeth into her skin, eventually fusing his circulation with hers. This parasitic mating provides the male consistent access to fertilize the female’s eggs, allowing anglerfish reproduction despite challenging conditions.

46. What extraordinarily long siphonophore was discovered recently?

In 2020, scientists discovered a giant siphonophore measuring over 150 feet (47 meters) long in waters off Western Australia. This rare specimen of the species Apolemia was stranded on the seafloor but filmed in the Ningaloo Canyons. Siphonophores are colonial organisms composed of many specialized zooids that work together.

Previously the longest known siphonophore measured 130 feet (40 m). The discovery highlights how much remains unknown about marine life, even gigantic invertebrates over three times the size of a blue whale!

47. How do stony and soft corals differ anatomically?

Stony corals secrete hard external skeletons of calcium carbonate that create reef frameworks. Soft corals lack these rigid skeletons and are flexible organisms composed of soft tissues. Stony corals include the familiar shallow-water reef-builders that harbor symbiotic algae for nutrition.

Soft corals often inhabit deeper, darker waters and capture more zooplankton. Though they evolved from similar ancestors, these two coral types developed markedly different structural strategies to thrive in various marine environments.

48. How much carbon dioxide do oceans absorb daily from the air?

The oceans currently soak up about 22 million metric tons of carbon dioxide from the atmosphere per day. This absorption helps slow the accumulation of heat-trapping CO2 in air and subsequent climate change.

But dissolving CO2 alters ocean chemistry, increasing acidity and reducing the availability of carbonate ions that many marine organisms need to build shells. The rate of carbon uptake is expected to decline as CO2 emissions continue rising. Oceans cannot absorb our greenhouse gas pollution indefinitely without severe consequences.

49. What percentage of shallow coral species could be threatened with extinction by mid-century?

Modeling suggests over 70% of shallow water (less than 30 m deep) tropical coral species could face extinction by mid-century if climate change continues unabated. Even under moderate emissions scenarios, 10–30% of corals globally could still reach dangerously threatened levels in decades.

The risk comes primarily from mass coral bleaching driven by warming ocean temperatures that disrupt the corals’ symbiotic algae. Protecting corals requires urgent, ambitious cuts in greenhouse gas emissions.

50. What is the global target for percentage of ocean area designated as marine protected areas?

Currently less than 15% of the world’s oceans are designated as marine protected areas. But the global target adopted by many nations is to conserve 30% of the ocean in MPAs by 2030. When effectively managed and located in key biodiversity hotspots, MPAs help safeguard ecosystems and allow recovery of exploited populations.

Facts About Life Below Water Global Goal

Networks of MPAs provide migratory corridors and climate refugia for marine life. Ambitious expansion of MPAs coupled with emissions reductions can help secure a vibrant ocean future. Consider reading >>>> Fun facts about life below water to learn more.