remiconnesson/oceanservice-noaa-facts huggingface dataset:
# What is a bight?

![The Southern California Bight - the curved coastline between Point Conception and San Diego that encompasses the Channel Islands and NOAA's Channel Islands National Marine Sanctuary.](/facts/bight.jpg)

_Can you spot the bight? This image shows the Southern California Bight — the curved coastline between Point Conception and San Diego that encompasses the Channel Islands (and NOAA's [Channel Islands National Marine Sanctuary](http://channelislands.noaa.gov/))._

A bight is a long, gradual bend or recess in the shoreline that forms a large, open bay. Bights are shallow and may pose hazards to navigation, so their depths, in addition to any submerged features like sand bars and rock formations, are clearly marked on [nautical charts](https://oceanservice.noaa.gov/facts/nautical_chart.html).

A number of bights can be found on both the U.S. West and East Coasts. The [Southern California Bight](https://deepseacoraldata.noaa.gov/regions/West_Coast), for example, is the curved coastline between Point Conception and San Diego, and encompasses the Channel Islands.

The [New York Bight](http://woodshole.er.usgs.gov/project-pages/newyork/) refers to the coastal area between Long Island and the New Jersey coast. It is part of a larger geographical area called the [Middle Atlantic (or Mid-Atlantic) Bight](http://woodshole.er.usgs.gov/project-pages/mobility/mid_atl_bight.html), which extends from Cape Hatteras, North Carolina, north to Cape Cod, Massachusetts.

One of the world's largest bights is the [Great Australian Bight](http://earthobservatory.nasa.gov/NaturalHazards/view.php?id=9214) on the continent's southern coast.
# What is a whale fall?

During a 2019 expedition, researchers discovered a whale fall at [10,623 feet](#) below the surface near Davidson Seamount in NOAA's [Monterey Bay National Marine Sanctuary](https://montereybay.noaa.gov/new/2019/191013nautilus.html).

The ocean's depths are supplied by nutrients falling down from the surface waters. When whales die and sink, the whale carcasses, or whale falls, provide a sudden, concentrated food source and a bonanza for organisms in the deep sea.

Different stages in the decomposition of a whale carcass support a succession of marine biological communities. Scavengers consume the soft tissue in a matter of months. Organic fragments, or detritus, enrich the sediments nearby for over a year.

The whale skeleton can support rich communities for years to decades, both as a hard substrate (or surface) for invertebrate colonization and as a source of sulfides from the decay of organic compounds of whale bones. Microbes live off of the energy released from these chemical reactions and form the basis of ecosystems for as long as the food source lasts.

At deep sea levels this forms a new food web and provides energy to support single- and multi-cell organisms and sponges, thus adding to the ocean's food chain.
# Are horseshoe crabs really crabs?

![Horsehoe crab mating season, Lewes, Delaware](/facts/horseshoe-crab.jpg "Horsehoe crab mating season, Lewes, Delaware")

_Horsehoe crab mating season, Lewes, Delaware. Image credit: Jacqueline Bedell_

##### **Did you know?**

_New Jersey and South Carolina currently forbid any harvesting of horseshoe crabs, and Delaware restricts harvesting to males only._

Despite their common name, horseshoe crabs are not really crabs (crustaceans), but are more closely related to spiders and scorpions. Atlantic horseshoe crabs (_Limulus polyphemus_), which swarm U.S. coastlines each summer from Maine to Mexico, have been called “living fossils” because they predate the dinosaurs by more than 200 million years. Their smooth, hard shell (exoskeleton) is shaped like a horseshoe (thus the name). They use their long tails as rudders in the water and to flip themselves if they get overturned on the beach. They are tremendous reworkers of sediments and feed on a variety of marine worms and invertebrates, including some commercially important fish.

Few people realize how important horseshoe crabs are to modern medicine. Because their blue, copper-based blood quickly clots in the presence of bacterial toxins, medical researchers use it to test intravenous drugs, vaccines, and medical devices, ensuring that they are free of bacterial contamination. Every year, many thousands of horseshoe crabs are harvested from their habitats, “bled” of about one-third of their blood, then returned to the beach relatively unharmed.

Horseshoe crabs also are important ecologically. More than 20 species of migratory birds, loggerhead sea turtles, and a myriad of commercial and recreation fish and crab species rely on the crabs’ eggs as an annual boon to their diets.

While Atlantic horseshoe crab numbers were declining in the 1990s, populations are recovering due to the regional management efforts of the states through the Atlantic States Marine Fisheries Commission. Delaware Bay has the largest population of horseshoe crabs in the world, and scientists from NOAA’s [National](/ecosystems/nerrs/) Estuarine Research Reserves System help conduct annual horseshoe crab spawning surveys, which is a Delaware Bay-wide effort. However, habitat loss and high demand as commercial bait are still concerns for horseshoe crabs and migratory shorebirds.

Did you know? - *New Jersey and South Carolina currently forbid any harvesting of horseshoe crabs, and Delaware restricts harvesting to males only.*
# Do fish sleep?

## While most fish **rest** by reducing their activity and metabolism, fish "sleep" is different from that of land mammals

![Image of a Pacific sand lance](/facts/pacific-sand-lance.jpg)

_A Pacific sand lance, shown here, employs a unique strategy of burrowing into sand to rest and conserve energy, and to avoid predation._

The nature of fish "sleep" is an area of active research. While fish do not sleep in the same way that land mammals sleep, most fish do rest.

Research shows that fish may reduce their activity and metabolism while remaining alert to danger. Some fish float in place, some wedge themselves into a secure spot in the mud or coral, and some even locate a suitable nest. These periods of "suspended animation" may perform the same restorative functions as sleep does in people.
# What are pelagic fish?

![tuna swimming](/facts/pelagic.jpg "Tuna swimming in the open ocean.")

_Oceanic pelagic fish, such as the tuna pictured above, have agile bodies made for long distance migration. Many oceanic pelagic fish travel in schools while some are solitary that drift with ocean currents._

Pelagic fish can be categorized as coastal and oceanic fish, based on the depth of the water they inhabit. Coastal pelagic fish inhabit sunlit waters up to about [655 feet](#) deep, typically above the continental shelf. Examples of species include forage fish such as anchovies, [sardines](https://www.fisheries.noaa.gov/species-directory/sustainable-seafood?oq=sardine), shad, and menhaden and the predatory fish that feed on them. Oceanic pelagic fish typically inhabit waters below the continental shelf. Examples include larger fish such as [swordfish](https://www.fisheries.noaa.gov/species-directory/sustainable-seafood?oq=swordfish), [tuna](https://www.fisheries.noaa.gov/species-directory/sustainable-seafood?oq=tuna), [mackerel](https://www.fisheries.noaa.gov/species-directory/sustainable-seafood?oq=mackerel), and even [sharks](https://www.fisheries.noaa.gov/species-directory/sustainable-seafood?oq=shark).

There is no distinct boundary from coastal to ocean waters so some oceanic fish become partial residents of coastal waters, often during different stages of their lifecycle. However, true oceanic species spend their entire life in the open ocean.

Pelagic fish get their name from the area that they inhabit called the pelagic zone. The pelagic zone is the largest habitat on earth with a volume of [330 million cubic miles](#). Different species of pelagic fish are found throughout this zone. Numbers and distributions vary regionally and vertically, depending on availability of light, nutrients, dissolved oxygen, temperature, salinity, and pressure.
# What is PORTS?

![The city of Miami stands in the distance as a shipping vessel carrying multi-colored shipping containers, stacked eleven to fourteen wide and three to four high, is guided into the crystal blue waters of PortMiami by a tug boat.](/news/apr18/shipping.jpg "Shipping")

_A container ship enters the shipping channel at PortMiami, where vessel pilots now have access to real-time current information to help guide them safely into port. This NOAA system, called PORTS® (short for Physical Oceanographic Real-Time System), is deployed in many busy waterways throughout the U.S. to provide key environmental parameters — including water levels, currents, waves, salinity, bridge clearance (air gap), winds, air and water temperature, and visibility. Sensors are tailored to meet specific needs at each seaport._

##### **Did you know?**

_The first PORTS® was established in Tampa, Florida, in 1991. Today, there are PORTS® operating across the nation._

NOAA PORTS® is an information system that measures and disseminates the oceanographic and meteorological data that mariners need to navigate safely.

Marine navigation safety is a serious issue of national concern. By volume, more than 95 percent of U.S. international trade moves through the nation's ports and harbors, with about 50 percent of those goods being hazardous materials. The potential risks to maritime commerce and the coastal environment are apparent.

PORTS® mitigates those risks by integrating real-time environmental data (water levels, tides, currents, waves, [salinity](/facts/whysalty.html), [bridge air gap](/facts/air-gap.html)) and meteorological parameters (winds, atmospheric pressure, air and water temperatures) with forecasts and other geospatial information, and tailoring the output to the needs of local communities.

Through PORTS®, NOAA is responding to one of the nation's most significant challenges – to improve the economic efficiency and competitiveness of U.S. maritime commerce while reducing risks to life, property, and the coastal environment.

Did you know? - 

- *The first PORTS® was established in Tampa, Florida, in 1991. Today, there are PORTS® operating across the nation.*

-
# What does a geodesist do?

##### **Did you know?**

_[Geodesy](https://oceanservice.noaa.gov/facts/geodesy.html) is the science of accurately measuring and understanding three fundamental properties of the Earth: its geometric shape, its orientation in space, and its gravity field as well as the changes of these properties with time._

Did you know? - *[Geodesy](https://oceanservice.noaa.gov/facts/geodesy.html) is the science of accurately measuring and understanding three fundamental properties of the Earth: its geometric shape, its orientation in space, and its gravity field as well as the changes of these properties with time.*
# What is the longest-lived marine mammal?

![Bowhead whale and calf in the Arctic (Marine Mammal Permit 782-1719)](/facts/bowhead.jpg)

 Whales are the largest animals on Earth and live longer than all other mammals in the contemporary animal kingdom.

While many ocean lovers can easily identify the iconic sperm whale, the charismatic humpback and the wily orca, not all are familiar with the bowhead. According to scientists, this colossal year-round Arctic dweller may live _200-plus years._ The bowhead’s lifespan may be the second-longest of all animals, topped only by the 500-year span of a North Atlantic clam called the ocean quahog.

The bowhead whale’s first claim to (scientific) fame was its humongous head, which houses the _largest mouth_ of any animal — its highly arched shape gives the species its name — and may comprise nearly 7.62 meters (25 feet) of a mature male’s 19.81-meter (65-foot) length. The overall length of the bowhead is long enough to stretch across a four-lane highway with plenty of room on either side.

Any bio of the bowhead would not be complete without mentioning its weight, which ranges from 68-90.7 metric tons (75-100 tons), and its .488-meter-wide (1.6-foot) layer of insulating blubber, which makes it very “well suited” to its icy environment.

The bowhead also sports, at up to 3.96 meters (13 feet) long, the longest baleen (filter-feeding organ) of its dozen baleen-whale “cousins.” Bowheads also boast _two_ blowholes, as do all baleen whales.

NOAA’s National Marine Fisheries Service has federal responsibility for protecting marine mammals and threatened and endangered marine life. With an estimated population of approximately 10,000, the bowhead whale is listed as [endangered](https://www.fisheries.noaa.gov/topic/laws-policies#endangered-species-act) under the Endangered Species Act and [depleted](https://www.fisheries.noaa.gov/topic/marine-mammal-protection) under the Marine Mammal Protection Act.

Did you know? - Corals may be the oldest living animals of all. Many corals appear to be a single organism, but they are actually colonies of genetically identical coral polyps that are constantly regenerating. Living deep-sea corals have been dated to be more than 4,000 years old!

- [National Marine Fisheries Service Species Directory](https://www.fisheries.noaa.gov/species/bowhead-whale)

-
# What are the trade winds?

![The Charles W. Morgan is the last of an American whaling fleet that numbered more than 2,700 vessels. Ships like the Morgan used routes defined by the trade winds to navigate the ocean](/facts/tradewinds.jpg)

_The _Charles W. Morgan_ is the last of an American whaling fleet that once numbered more than 2,700 vessels. Ships like the _Morgan_ often used routes defined by the trade winds to navigate the ocean._

Known to sailors around the world, the trade winds and associated ocean currents helped early sailing ships from European and African ports make their journeys to the Americas. Likewise, the trade winds also drive sailing vessels from the Americas toward Asia. Even now, commercial ships use "the trades" and the currents the winds produce to hasten their oceanic voyages. 

How do these commerce-friendly winds form? Between about 30 degrees north and 30 degrees south of the equator, in a region called the [horse latitudes](/facts/horse-latitudes.html), the Earth's rotation causes air to slant toward the equator in a southwesterly direction in the northern hemisphere and in a northwesterly direction in the southern hemisphere. This is called the [Coriolis Effect](/education/tutorial_currents/04currents1.html).

The Coriolis Effect, in combination with an area of high pressure, causes the prevailing winds—the trade winds—to move from east to west on both sides of the equator across this 60-degree "belt."

As the wind blows to about five degrees north and south of the equator, both air and ocean currents come to a halt in a band of hot, dry air. This 10-degree belt around Earth's midsection is called the [Inter-Tropical Convergence Zone](https://www.weather.gov/jetstream/itcz), more commonly known as the [doldrums.](/facts/doldrums.html)

Intense solar heat in the doldrums warms and moistens the trade winds, thrusting air upwards into the atmosphere like a hot air balloon.  As the air rises, it cools, causing persistent bands of showers and storms in the tropics and rainforests. The rising air masses move toward the poles, then sink back toward Earth's surface near the horse latitudes. The sinking air triggers the calm trade winds and little precipitation, completing the cycle.
# How far does sound travel in the ocean?

## The distance that sound travels in the ocean varies greatly, depending primarily upon water temperature and pressure.

  

![illustration of whale and sound channel](/facts/sound.jpg "short caption")

Water temperature and pressure determine how far sound travels in the ocean.

While sound moves at a much faster speed in the water than in air, the distance that sound waves travel is primarily dependent upon ocean temperature and pressure. While pressure continues to increase as ocean depth increases, the temperature of the ocean only decreases up to a certain point, after which it remains relatively stable. These factors have a curious effect on how (and how far) sound waves travel.

Imagine a whale is swimming through the ocean and calls out to its pod. The whale produces sound waves that move like ripples in the water. As the whale’s sound waves travel through the water, their speed decreases with increasing depth (as the temperature drops), causing the **sound waves to refract downward**. Once the sound waves reach the bottom of what is known as the _thermocline_ layer, the speed of sound reaches its minimum. The thermocline is a region characterized by rapid change in temperature and pressure which occurs at different depths around the world. Below the thermocline "layer," the temperature remains constant, but pressure continues to increase. This causes the speed of sound to increase and makes the **sound waves refract upward**.  

The area in the ocean where sound waves refract up and down is known as the "sound channel." The **channeling of sound waves** allows sound to travel thousands of miles without the signal losing considerable energy.  In fact, hydrophones, or underwater microphones, if placed at the proper depth, can pick up whale songs and manmade noises from many kilometers away.
# What are Mesophotic Coral Ecosystems?

## Mesophotic coral ecosystems exist in low light—"meso" means middle and "photic" refers to light.

 [](/facts/mesophotic.mp4) 

### NOAA Ocean Today: The Mesophotic Zone

_You’re entering another dimension. A dimension of water, of darkness, of mystery. Next stop, The Mesophotic Zone!_ Did you enjoy this video? Head to [Ocean Today](http://oceantoday.noaa.gov/) for over a hundred videos that explore all aspects of the ocean realm—exploration and discoveries, marine life and science.

Mesophotic coral ecosystems are found in tropical and subtropical regions at depths ranging from almost 100 feet to over 490 feet below the ocean’s surface. The dominant communities providing structural habitat in the mesophotic zone are corals, sponges, and algae.

Little is known or understood about these ecosystems because until recently, studies were hampered by lack of technology. The upper limit of mesophotic coral ecosystems coincides with the diving limit for conventional scuba diving (130 feet), but is too shallow and costly for most deep-diving technologies, such as remotely operated vehicles and submersibles, to operate in. However, advances in undersea technologies in the past decade now make it possible to investigate these ecosystems.

In an era of significant changes occurring on shallow coral reefs, it is important for scientists to understand the role of mesophotic coral ecosystems in tropical and subtropical regions. These ecosystems are regarded as extensions of shallow coral ecosystems and share common species. As a result, scientists hypothesize that mesophotic corals may serve as potential sources to reseed or replenish degraded shallow-water reef species.

Mesophotic coral ecosystems also serve as essential fish habitat for some economically and ecologically important fish species, which use these areas for spawning, breeding, feeding, and growth to maturity. Similar to shallower coral ecosystems, mesophotic coral ecosystems contain organisms with specialized defenses to ward off predators and microbial infections. These specialized defenses often yield compounds that can be used to develop natural products that benefit human health.

Did you know? - 

- Scientists have found that, in some cases, [mesophotic reefs act as potential sources to reseed or renew shallower coral reefs as well as important habitats of many fish species](https://coastalscience.noaa.gov/news/climate/can-mesophotic-coral-ecosystems-serve-lifeboats-shallow-reefs/). Bringing to light the existence of healthy mesophotic coral ecosystems provides insights on the devastating declines and opportunities for management and restoration of both shallow-water corals and the newly recognized mesophotic ecosystems.
# Why does the ocean have waves?

## Waves are created by energy passing through water, causing it to move in a circular motion.

 [](/facts/waves-of.mp4) 

VIDEO: What are waves? Here's what you need to know in less than a minute. [Transcript](#transcript)

The ocean is never still. Whether observing from the beach or a boat, we expect to see waves on the horizon. Waves are created by energy passing through water, causing it to move in a circular motion. However, water does not actually travel in waves. Waves transmit energy, not water, across the ocean and if not obstructed by anything, they have the potential to travel across an entire ocean basin.

Waves are most commonly caused by wind. **Wind-driven waves**, or **surface waves**, are created by the friction between wind and surface water. As wind blows across the surface of the ocean or a lake, the continual disturbance creates a wave crest. These types of waves are found globally across the open ocean and along the coast. 

More potentially hazardous waves can be caused by severe weather, like a hurricane. The strong winds and pressure from this type of severe storm causes [storm surge](/facts/stormsurge-stormtide.html), a series of long waves that are created far from shore in deeper water and intensify as they move closer to land. Other hazardous waves can be caused by underwater disturbances that displace large amounts of water quickly such as earthquakes, landslides, or volcanic eruptions. These very long waves are called [tsunamis](/facts/tsunami.html). Storm surge and tsunamis are not the types of waves you imagine crashing down on the shore. These waves roll upon the shore like a massive sea level rise and can reach far distances inland.

The gravitational pull of the sun and moon on the earth also causes waves. These waves are [tides](/facts/tides.html) or, in other words, **tidal waves**. It is a common misconception that a tidal wave is also a tsunami. The cause of tsunamis are not related to tide information at all but can occur in any tidal state.

## Video Transcript

Waves transmit energy, not water, and are commonly caused by the wind as it blows across the ocean, lakes, and rivers. Waves caused by the gravitational pull of the moon and the sun are called tides. The ebb and flow of waves and tides are the life force of our world ocean.

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Tsunami waves may travel as fast as jet planes over deep waters, only slowing down when reaching shallow waters. Find out more in our [Ocean Fact](/facts/tsunami.html).

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**Last updated:** 06/16/24  
**Author:** NOAA  
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Did you know? - 

- Tsunami waves may travel as fast as jet planes over deep waters, only slowing down when reaching shallow waters. Find out more in our [Ocean Fact](https://oceanservice.noaa.gov/facts/tsunami.html).
# What is the international date line?

## The international date line serves as the "line of demarcation" between two consecutive calendar dates.

![Google Earth view of globe showing international date line](/facts/idl.jpg "A view of the international date Line")

The international date line, shown here as a yellow line, defines the boundary between calendar dates.

The international date line, established in 1884, passes through the mid-Pacific Ocean and roughly follows a 180 degrees longitude north-south line on the Earth. It is located halfway around the world from the prime meridian — the 0 degrees longitude line in Greenwich, England.

The international date line functions as a “line of demarcation” separating two consecutive calendar dates. When you cross the date line, you become a time traveler of sorts! Cross to the west and it’s one day later; cross back and you’ve “gone back in time."

Despite its name, the international date line has no legal international status and countries are free to choose the dates that they observe. While the date line generally runs north to south from pole to pole, it zigzags around political borders such as eastern Russia and Alaska’s Aleutian Islands.