The Sargasso Sea, located entirely within the Atlantic Ocean, is the only sea without a land boundary

The Sargasso Sea is a vast patch of ocean is named for a genus of free-floating seaweed called Sargassum. While there are many different
types of algae found floating in the ocean all around world, the Sargasso Sea is unique in that it harbors species of sargassum that are 'holopelagic' — this means that the algae not only freely floats
around the ocean, but it reproduces vegetatively on the high seas. Other seaweeds reproduce and begin life on the floor of the ocean.

Sargassum provides a home to an amazing variety of marine species. Turtles use sargassum mats as nurseries where hatchlings have food and shelter. Sargassum also provides essential habitat for marine species,such as shrimp, crab, and fish, that have adapted specifically to this floating algae. The Sargasso Sea is a spawning site for threatened and endangered eels, as well as white marlin, porbeagle shark, and dolphinfish. Humpback whales annually migrate through the Sargasso Sea. Commercial fish, such as tuna, and birds also migrate through the Sargasso Sea and depend on it for food.

While all other seas in the world are defined at least in part by land boundaries, the Sargasso Sea is defined only by ocean currents. It lies within the Northern Atlantic Subtropical Gyre. The Gulf Stream establishes the Sargasso Sea's western boundary, while the Sea is further defined to the north by the North Atlantic Current, to the east by the Canary Current, and to the south by the North Atlantic Equatorial Current. Since this area is defined by boundary currents, it's borders are dynamic, correlating roughly with the Azores High Pressure Center for any particular season.

For more information:
What's the difference between an ocean and a sea? (Ocean Fact)

Sargassum: A Complex 'Island' Community at Sea (NOAA's Ocean Explorer)

Sampling the Sargassum Community: Dip Nets and Green-Light Lures (NOAA's Ocean Explorer)

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You won't find Spirobranchus giganteus, also known as the Christmas tree worm, eating your fir tree this year. The common name for these worms is derived from their appearance, not their habitat or diet.

Each worm has two brightly colored crowns that protrude from its tube-like body. These Christmas tree-like crowns are composed of radioles, or hair-like appendages radiating from the worm's central spine. These appendages are used for respiration and to catch dinner, which typically consists of microscopic plants, or phytoplankton, floating in the water.

These worms are sedentary, meaning that once they find a place they like, they don’t move much. In fact, while the colorful crowns of these worms are visible, most of their bodies are anchored in burrows that they bore into live coral. When startled, Christmas tree worms rapidly retract into their burrows, hiding from would-be predators.

Christmas tree worms come in a variety of bright colors. They aren’t very big, averaging about 1.5 inches in length. However, because of their distinctive shape, beauty, and color, these worms are easily spotted. They are some of the most widely recognized polycheates, or marine burrowing, segmented worms out there.

For more information:
Florida Keys National Marine Sanctuary: Christmas Tree Worms

Flower Garden Banks National Marine Sanctuary: Christmas Tree Worms

Encyclopedia of the Sanctuaries: Christmas Tree Worms

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Corals have long been popular as souvenirs, for home decor, and in jewelry, but many consumers are unaware that these beautiful structures are made by living creatures. Fewer still realize that corals are dying off at alarming rates around the world.
Coral reefs are some of the most biologically rich and economically valuable ecosystems on Earth, but they are increasingly threatened by pollution, invasive species, fishing, disease, bleaching, and global climate change.

Strong consumer demand for coral, heightened over the holiday season, is another factor that is contributing to the decline of coral reefs.

Corals are popular as souvenirs, for home decor and in costume jewelry, yet corals are living animals that eat, grow and reproduce. It takes corals decades or longer to create reef structures, so leave corals and other marine life on the reef.

For more information:
NOAA Coral Reef Watch

NOAA Coral Reef Conservation Program

NOAA Coral Reef Information System

10 Things You Need to Know About Marine Debris

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'Turkeyfish' is another name for lionfish.

Viewed from the right angle, the ornate fins of the lionfish resemble turkey plumage. That's why 'turkeyfish' is one of the many imaginative names people use when referring to the lionfish.

Lionfish are native to the Indo-Pacific, but are now established along the southeast coast of the U.S., the Caribbean, and in parts of the Gulf of Mexico.

Since lionfish are not native to Atlantic waters, they have very few predators. They are carnivores that feed on small crustaceans and fish, including the young of important commercial fish species such as snapper and grouper.

How lionfish will affect native fish populations and commercial fishing industries has yet to be determined. What is known is that non-native species can dramatically affect native ecosystems and local fishing economies. Experts are carefully studying these invaders to better understand their role in, and threat to, Atlantic Ocean ecosystems.

For more information:
Learn more about invasive lionfish from NOAA's Center for Coastal Fisheries and Habitat Research

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The name of the green sea turtle is derived from the reptile's greenish-colored fat Adult green turtles are herbivores, which means they eat only plants such as seagrasses and algae. This diet is thought to give them their greenish-colored fat, hence the name, the green turtle.

Green turtles primarily use three types of habitat - beaches for nesting, open ocean convergence zones as juveniles, and coastal areas for benthic feeding as adults. In the U.S. Atlantic and Gulf of Mexico waters, green turtles are found in inshore and nearshore waters from Texas to Massachusetts, the U.S. Virgin Islands, and Puerto Rico. In the eastern North Pacific, green turtles have been sighted from Baja California to southern Alaska, but most commonly are seen south of San Diego. Also, in the central Pacific, green turtles are found around most tropical islands, including the Hawaiian Islands.

Green turtles face a host of threats in the marine environment. Incidental capture in fishing gear is an ongoing threat to green turtles, which also affects many other marine species. Green turtles also suffer from a disease known as fibropapillomatosis in some areas of the world. The main cause of the historical, worldwide decline of the green turtle was the long-term harvest of eggs, juveniles, and adults from their nesting beaches and feeding grounds. These harvests still continue in some areas of the world, compromising efforts to recover this species.


For more information:
NOAA Fisheries: Green Turtle Fact Sheet

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Sea cucumbers are animals, not vegetables. Found only in salt water, more than a thousand species of sea cucumbers exist around the world. These squishy invertebrates are echinoderms, making them distant relatives to starfish and urchins. Unlike starfish or sea urchins, the bodies of sea cucumbers are covered with soft, leathery skin instead of hard spines.

If you ever encounter a sea cuke and he feels threatened, you could be in for a surprise. Some sea cucumbers shoot sticky threads at their enemies, entangling and confusing predators. Others can violently contract their muscles and shoot some of their internal organs out of their rear ends. The missing body parts are quickly regenerated.

Most sea cucumbers are scavengers, moving along the seafloor and feeding on tiny particles of algae or microscopic marine animals collected with tube feet that surround their mouths. The particles they grind down to smaller pieces are further broken down by bacteria and become part of the ocean’s nutrient cycle. This is a similar role to that which earthworms perform on land.

Sea cucumbers are enjoyed as meals for other critters such as fish and crabs. In some places, especially Asia, sea cucumbers are considered a delicacy and are enjoyed by humans.

Sea cukes are certainly a little odd, and definitely not something you’d ever find in your garden.


For more information:
Weird Fins: Sea cucumbers, NOAA’s National Marine Fisheries Service

Weird Animals: Sea Cucumbers, Ocean Today



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Sea stars, commonly called, "starfish," are not fish

Sea stars live underwater, but that is where their resemblance to fish ends. They do not have gills, scales, or fins. Sea stars live only in saltwater. Sea water, instead of blood, is actually used to pump nutrients through their bodies via a 'water vascular system.'

Also, sea stars move by using tiny tube feet located on the underside of their bodies. Adult sunflower sea stars can move at the astonishing speed of one meter per minute using 15,000 tube feet. Tube feet also help sea stars hold their prey.

Sea stars are related to sand dollars, sea urchins, and sea cucumbers, all of which are echnioderms, meaning that they have five-point radial symmetry. However, this does not mean that all sea stars have five arms and species with 10, 20, or even 40 arms exist! If one of these arms is lost, a sea star has the amazingly ability to regenerate it.

For more information:
Sunflower sea star, National Marine Fisheries Service
Six-rayed sea star, National Marine Fisheries Service

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Only about five percent of the body of a jellyfish is solid matter; the rest is water

Fascinating, elegant, and mysterious to watch in the water, take a jellyfish out of the water, and it becomes a much less fascinating blob. This is because jellyfish are about 95 percent water.

Lacking brains, blood, or even hearts, jellyfish are pretty simple critters. They are composed of three layers: an outer layer, called the epidermis; a middle layer made of a thick, elastic, jelly-like substance called mesoglea; and an inner layer, called the gastrodermis. An elementary nervous system, or nerve net, allows jellyfish to smell, detect light, and respond to other stimuli. The simple digestive cavity of a jellyfish acts as both its stomach and intestine, with one opening for both the mouth and the anus.

These simple invertebrates are members of the phylum Cnidaria, which includes creatures such as sea anemones, sea whips, and corals. Like all members of the phylum, the body parts of a jellyfish radiate from a central axis. This “radial symmetry” allows jellyfish to detect and respond to food or danger from any direction.


Jellyfish have the ability to sting with their tentacles. While the severity of stings varies, in humans, most jellyfish stings result only in minor discomfort.

For more information:
Jellyfish Gone Wild, National Science Foundation
Mapping Sea Nettles in the Chesapeake Bay

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The health of submerged aquatic vegetation is an important environmental indicator of overall ocean and estuary health.

Seagrasses in bays and lagoons, for instance, are vital to the success of small invertebrates and fish. These small creatures are a food source for commercial and recreational fish.

Seagrasses also stabilize sediments, generate organic material needed by small invertebrates, and add oxygen to the surrounding water.

Underwater vegetation in shallow coastal waters also supports a wide diversity of marine creatures by providing spawning, nursery, refuge, and foraging grounds for many species.

For more information:
Benthic Habitat Mapping, NOAA Coastal Services Center (CSC)
Benthic Habitat Data, CSC

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Some seaweeds are microscopic, such as the phytoplankton that live suspended in the water column and provide the base for most marine food chains. Some are enormous, like the giant kelp that grow in abundant “forests” and tower like underwater redwoods from their roots at the bottom of the sea. Most are medium-sized, come in colors of red, green, brown, and black, and randomly wash up on beaches and shorelines just about everywhere.


The vernacular “seaweed” is a bona-fide misnomer, because a weed is a plant that spreads so profusely it can harm the habitat where it takes hold. (Consider kudzu, the infamous “mile-a-minute vine” that chokes waterways throughout the U.S. Southeast). Not only are the fixed and free-floating “weeds” of the sea utterly essential to innumerable marine creatures, both as food and as habitat, they also provide many benefits to land-dwellers, notably those of the human variety.

Seaweed is chock-full of vitamins, minerals, and fiber, and can be tasty. For at least 1,500 years, the Japanese have enrobed a mixture of raw fish, sticky rice, and other ingredients in a seaweed called nori. The delectable result is a sushi roll. Many seaweeds contain anti-inflammatory and anti-microbial agents. Their known medicinal effects have been legion for thousands of years; the ancient Romans used them to treat wounds, burns, and rashes. Anecdotal evidence also suggests that the ancient Egyptians may have used them as a treatment for breast cancer. Certain seaweeds do, in fact, possess powerful cancer-fighting agents that researchers hope will eventually prove effective in the treatment of malignant tumors and leukemia in people. While dietary soy was long credited for the low rate of cancer in Japan, this indicator of robust health is now attributed to dietary seaweed. These versatile marine plants and algae have also contributed to economic growth. Among their many uses in manufacturing, they are effective binding agents (emulsifiers) in such commercial goods as toothpaste and fruit jelly, and popular softeners (emollients) in organic cosmetics and skin-care products. All across our ocean wafts a wonderful “weed,” indeed.

For more information:
Seaweeds, Olympic Coast National Marine Sanctuary |Kelp Forests, Office of National Marine Sanctuaries

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