Shorelines of oceans, seas, and large bodies of water around the world are habitats for plants and animals that thrive in challenging conditions. Tides occur twice each day when water levels rise over a six hour period to cover large areas before receding to leave those same areas open to the air until the next tide starts to move inland again.
Nearshore habitat zones by King County, WA;Littoral Zones by US Government
Shoreline habitat has been classified into zones often known by many different names. The intertidal zone is the area affected by changing temperature and salinity conditions as water moves in and out with each tide. The subtidal zone is the lowest and is exposed to air only during extreme spring tides or storms. The backshore zone is the highest and is exposed to water only during extreme spring tides or storms.
Starfish & anemone in tidal pool by Jonathan Levy
Sea urchin in tidal pool, Bahia de Banderas by Jim Hoffman, Mar 2017
Many species of animals live in each zone and are adapted to living completely submerged as well as completely uncovered by water for several hours each day. They handle the change in temperature and salinity with exposure to air or water. Tidal pools may keep some animals submerged for far longer periods. Temperature, dissolved oxygen, and salinity change far less for these organisms.
Bryozoans by John Turnbull, Sep 2021; Sea anemone by Barb Ignatius; Squat lobster, Glathea rostrata, by FWC Fish & Wildlife Research Institute, Aug 2013
Some species can be found in every zone in the ecosystem, but many are anchored to rocks or dug into the bottom. Species may prefer one zone, but get washed into another zone by wave action. Many organisms have tough outer surfaces to put up with battering waves and exposure to sun and wind. All of the occupants are subject to a wide range of predators from those that move on dry land to underwater hunters. Let’s take a look at a few of the creatures able to live in these ever-changing conditions.
The sea anemone clings to rocks and protects itself by drawing in its tentacles to become a jelly-like blob. The squat lobster can be found under stones along the shoreline. Its tail is fan-shaped and facilitates quick escapes when the animal is threatened by pulling the lobster through the water with powerful strokes. Bryozoans are small filter feeding organisms protected by a hard exoskeleton that the animal can withdraw into for protection.
Dog whelk, Nassarius livescens, by Budak, Dec 2016
Starfish & anemone in tidal pool by Jonathan Levy
A mollusk called a dog whelk is a stealth predator often found on rocky surfaces. It uses its tongue to drill through the shells of other mollusks, where it squirts a digestive juice into the prey’s shell which kills and partially digests the prey. The dog whelk then uses its tongue to suck up the soupy meal. The starfish is another fierce predator. It wraps its arms around a shellfish and pulls it apart. Upon opening the shell, the starfish pushes its stomach out of itself and into the prey’s open shell where it empties its digestive juices inside, and similar to the dog whelk, creates a tasty, soupy, meal.
Fan worm by Marta Terry L.
Sea urchin in tidal pool, Bahia de Banderas by Jim Hoffman, Mar 2017
Sea urchins can be found clinging to hard surfaces where they feed on algae and other small, encrusted animals. Fan worms look like a leathery tube among underwater rocky crags. Several feathery tentacles fan out into the water to filter out microorganisms flowing by.
Shorelines create a habitat that is constantly changing with tides moving in and out, inconsistent weather conditions, and a large variety of flora and fauna coming and going. Learn more about this fascinating habitat at the Jurica-Suchy Nature Museum or a natural history museum near you.
Botanical beach at Port Renfrew by James Wheeler; Feather Boa kelp in the surf by Kqedquest, May 2007; Rocky intertidal zone in Oregon by Minustide, May 2015
Sea turtles live in every ocean environment around the world, nesting on tropical and subtropical beaches, and migrating long distances. They spend their entire lives at sea except when females come ashore to lay their eggs. They have been on earth for over 100 million years, surviving the period when most dinosaurs and other reptiles died out 65 million years ago.
Coral reef & hawksbill sea turtle by jakubgojda, Indian Ocean, Maldives
Sea turtles are large, air-breathing reptiles with upper (carapace) and lower (plastron) shells. Six of the seven species are covered by hard scales called scutes. Although none have teeth, jaws are suited to each species specific diet. Sea turtles do not have ears, but there are eardrum openings covered by a flap of skin. Their sense of smell is excellent as is their underwater vision, although they are nearsighted when out of the water. Along with a streamlined body, they possess powerful legs and claws for swimming, diving, and catching food.
Green turtle eating seagrass by LauraDin, Getty Images
Green sea turtles, Chelonia mydas, on coral reef by Artush, Alam, Egypt
Sea turtles, along with manatees, are excellent caretakers of seagrass beds and coral reefs, habitats that are vital to the reproduction of fish, shellfish, and crustaceans. Seagrass, one of their favorite foods, grows faster and stronger with daily trimming from turtle munching. Coral beds, vulnerable to collapse and suffocation under mass quantities of sponges and small crustaceans, benefit from sea turtles that eat several hundred of these animals each day.
Olive ridley digging egg chamber by JHVEPhoto, Getty Images, Costa Rica
Green sea turtle hatchlings by Penny Britt, Getty Images
After reaching sexual maturity, which takes from 15 to 50 years, depending on the species, female sea turtles return every two to five years to the beach where they were born to lay their eggs. On average, they dig three to seven nests and place about 100 eggs in each. Baby sea turtles break out of their egg and instinctively flee for the lighter colored horizon where the ocean meets the beach. They spend several years in the open ocean feeding and growing before venturing into shallower waters to eat, mate, and reproduce. Only about one in a thousand babies will grow to be an adult. Most are prey for birds, crabs and fish, but many are killed by humans for food, medicines, and religious ceremonies. Nesting site habitat destruction and turtles caught as part of the fishing industry also play a part in population decline.
Jellyfish & jacks by melissaf84, Getty Images, Coral Sea; Whelks by Pack-Shot, Getty Images; Reef crab by JohnAndersonPhoto, Getty Images, Lembeh Strait, Indonesia; Posidonia seagrass meadow by Arnaud Abadie, Getty Images Signature, Mediterranean Sea
Females lay all of their eggs on land, but nesting sites and the best feeding sites may be thousands of miles apart. Sea turtles are found throughout the world’s oceans following concentrations of jellyfish, sponges, and crustaceans found in coral reefs and seagrass beds. Leatherback females have been tracked making migrations of over 12,000 miles between nest sites and the best annual feeding grounds during non-breeding seasons.
Read facts on each species in the sidebar, shown below. Come to the Jurica-Suchy Nature Museum where we have loggerhead, hawksbill, and green sea turtles on display to learn more about these creatures and their hidden realms.
Pics 1&2: Green sea turtle, Chelonia mydas, by DonArnold, JSNM 2023; Pics 3-6: Hawksbill sea turtle, Eretmochelys imbricata, by DonArnold, JSNM 2023; Pic 7: Loggerhead sea turtle, Caretta caretta, by DonArnold, JSNM 2023
Sea turtle species…
There are seven species of sea turtles in the world. All are experiencing dwindling populations from various threats. Two are critically endangered: the hawksbill sea turtle and the Kemp’s ridley sea turtle. Two are endangered: the green sea turtle and the flatback sea turtle. Three are listed as threatened: the leatherback sea turtle, the olive ridley sea turtle, and the loggerhead sea turtle.
Hawksbill sea turtles, Eretmochelys imbricata, have a narrow head allowing access to tight spaces in coral reefs, the usual spot to find sponges. They consume 1,000 pounds of sponges annually, keeping coral reefs free from suffocation by the sponges. These turtles are medium size at 2′-3′ and 100-200 pounds. Females nest on beaches among rocky areas 3-4 times in a season and lay 140-200 eggs in each nest.
Hawksbill portrait, Eretmochelys imbricata, by Sheraca, Dec 2014; Hawksbill sea turtle, Eretmochelys imbricata, by Goug Finney, Sep 2019
Kemp’s ridley sea turtles, Lepidochelys kempii, are the smallest species at 2′ in diameter and 75-100 pounds. Kemp’s ridley turtles have made a huge recovery from the 1960s, when there were about 200 individuals left, to almost 9,000 today. This is due to changes in Mexico’s laws, where 95% of their nesting takes place, to protect nest sites from disturbance.
Kemp’s ridley sea turtle, Lepidochelys kempii, by USFWS, Sep 2010
Green sea turtles, Chelonia mydas, grow to 4′ and 500 pounds. They are herbivores with a finely serrated beak for biting seagrass and scraping algae from hard surfaces. This is the only species known to come onshore to bask in the sun. They are named for the color of their fat, not their shell.
Green sea turtle, Chelonia mydas, by Florida Fish&Wildlife
Flatback sea turtles, Natator depressus, have a flattened carapace, unlike other turtles. They are medium sized at 3′ and 200 pounds. Found only in Australia, they do not migrate. Females lay only about 50 eggs in a nest, but nests are well spread out, helping to better protect their eggs. Their biggest threat is being preyed upon by saltwater crocodiles.
Leatherback sea turtles, Dermochelys coriacea, are the largest species at 4′-8′ and 500-2,000 pounds. They consume mostly jellyfish, daily eating their own weight in food. They have no scutes, but are covered by a flexible, leathery skin that allows them to dive up to 4,000 feet deep searching for prey. These turtles have thermoregulatory adaptations that allow them to hunt in very cold waters from Alaska to Chile, and they regularly make the longest migration of any vertebrate animal, traveling over 12,000 miles annually.
Leatherback sea turtle, Dermochelys coriacea, by Claudia Lombard, USFWS, Jun 2011
Olive ridley sea turtles, Lepidochelys olivacea, are small at 2′ and 75-100 pounds. They are the most abundant of all species. On certain beach sites, nesting females form an arribada, a grouping of all the females offshore who all come ashore at the same time to nest and lay eggs. Females on other sites may nest alone. Arribadas are particularly vulnerable to mass mortality events, but these are rare and population numbers remain consistent.
Olive ridley sea turtle, Lepidochelys olivacea, by Charles Peterson, Head Start Programs, Oct 2002
Loggerhead sea turtles, Caretta caretta, grow to 4′ and 200-400 pounds. Their very large heads and jaws can easily crush hard shells, allowing them to eat crabs, conches, and whelks. They have the largest concentration of nests annually, including 30,000 at a single Mediterranean location. Their shells provide space for 50 to 100 epibionts: plants and invertebrates that live permanently attached to their shells.
Loggerhead sea turtle, Caretta caretta, & epibionts by actor212, Aug 2017
Puffins are part of the Alcidae family of seabirds along with murres, guillemots, auklets, murrelets, and 25 recently extinct species. All members of the family can fly and are excellent divers and swimmers. Three species are found in the North Pacific Ocean including the tufted puffin, Fratercula cirrhata, horned puffin, Fratercula corniculata, and rhinoceros auklet, cerorhinca monocerata. The Atlantic puffin, Fratercula arctica, is the only species found in the North Atlantic Ocean.
Images clockwise: Atlantic puffin, Fratercula arctica, portrait by stockomotion, Getty Images Signature; Horned puffin, Fratercula corniculata, showing horns over eye by webguzs, Getty Images; Tufted puffin, Fratercula cirrhata, on the water by Bruce Block, Getty Images Signature; Rhinoceros auklet, Cerorhinca monocerata, by nikkigensert, Getty Images
The rhinoceros auklet was thought to have been misidentified when it was first discovered and named. However, DNA testing has shown that all four puffin species have a common auklet ancestor. Puffin species have short, stocky wings and tails, with darker gray-to-black plumage on top of their heads and backs and lighter whitish-to-brown plumage on their faces and underparts. Their bills change color during breeding seasons to display several stripes of red, orange, yellow, and black.
Short wings require the birds to beat them quite fast to fly, about 400 beats a minute, but they achieve speeds of 45 to 55 mph in flight. Short wings are used as powerful flippers underwater along with feet used as rudders. Puffins can dive to 200 feet or more catching a dozen or more small fish and invertebrates as they swim through the water. A uniquely designed hinge on their bill allows the top and bottom bill to meet at several different angles so the bird can add more fish without losing its grip on any that are already caught.
Images clockwise: Horned puffin, Fratercula corniculata, with fish catch in Alaska by Gerald Corsi, Getty Images; Atlantic puffin, Fratercula arctica, with catch by Daniel Jara, Getty Images; Rhinoceros auklet, Cerorhinca monocerata, with seven fish Andrew Reding, Jul 2010
Puffins spend winters at sea, far from land, floating on the surface or pursuing prey. Breeding season occurs in late spring, and most adult birds come together, forming large colonies containing breeding and non-breeding individuals. Non-breeding birds spend hours each day exhibiting a behavior called wheeling flight – flying figure eights over the cliffs where the colony is located. After finding a mate, puffins form long-term pair bonds. After breeding, pairs may split up when out at sea, but often return the next breeding season to find the same mate and nesting site. Puffins breed in large colonies on coastal cliffs of offshore islands. Only one egg is laid and both parents incubate the egg and feed the chick. Chicks fledge at night, and juveniles spend the first five years out at sea before returning to the breeding colonies.
Horned puffin, Fratercula corniculata, nesting on Latrabjarg Cape, Vestfirdir, Iceland by Nikolay Tsuguliev, Getty Images
Atlantic puffin roost by Shankar S., May 2016
Puffins are not considered endangered, but are starting to encounter trends affecting the continuity of their successful breeding. Warming waters in the oceans are reducing populations of fish that breed and live in cold water areas, that are the favorite prey of the auk family. Threats on the mainland of Iceland, historically one of the largest breeding colonies, include being hunted by mink introduced in the 1930s, so most colonies are now located on offshore islands. Hunting for feathers, eggs, and meat has been sustainable on island ranges for hundreds of years. However, hunting on the American mainland during the late 1800s and early 1900s eradicated the population at one point. In the last 50 years, about 50,000 birds have returned to protected areas in Maine. Their biggest natural predator is the great black-backed gull which dive-bombs and picks off birds near shore during breeding periods.
Tufted puffin, Fratercula cirrhata, spreading its wings by TiannaChantal, Getty Images
Puffins have an average lifespan of over thirty years, spending most of their lives out at sea. Reproduction rates are low with only one chick born each year to a pair of puffins, but a breeding pair may produce twenty chicks in their lifetimes and threats from natural predators are small. Puffins are favorite species in many zoos and some aquariums. Learn more by visiting a local institution or take a virtual tour from a live webcam at: https://explore.org/livecams/puffins/puffin-loafing-ledge-cam.
Seventy percent of the Earth’s surface is under the ocean, and only a small portion is in shallow water along continental shelf areas. The ocean is divided into five zones; the sunlight zone, above 650 feet; the twilight zone, extending to 3300 feet; the midnight zone, down to 13,000 feet; the abyssal zone, down to 21,300 feet; and the hadal zone, extending to the bottom of the ocean. Below 3,000 feet, no light penetrates from the surface; the water temperatures are freezing; and oxygen levels are very low. The pressure exerted on any surface at sea level is 14.7 pounds per square inch (psi), and humans can withstand three to four times this amount, or 45 psi to 60 psi. At 3,000 feet deep, the pressure is 1,345 psi.
Ocean zone chart by DonArnold, 2023
Delta submersible by Robert Schwemmer, CINMS, NOAA, Oct 2010
Pressure keeps sea water from becoming solid ice, even when it is at freezing temperatures. It also makes exploring the ocean difficult, requiring special submersible vehicles. Everything moves more slowly under pressure, and a submersible can take an explorer deep into the ocean given enough time and oxygen. Deep sea creatures can survive because the structure of their bodies is lean and contain no air spaces. Let’s take a look at a few of the wondrous creatures that live in these habitats.
Humpback anglerfish by August Brauer in Public Domain
In the darkness of deep areas, many species find food and mates by touch. Others may use bioluminescent communication – the ability to create light from a chemical reaction between luciferin and oxygen within an organism’s body. Lights show up as spots of various colors on different parts of the body and may be used for attracting a mate, confusing a predator, or attracting prey. Lanternfish have several spots located on their heads, undersides, and tails. Female anglerfish and dragonfish have a shaft that protrudes from their head out in front of their mouths with a glowing tip attracting prey within striking distance. Gulper eel use the lighted tip of their tail as a lure to attract a meal.
Tripod fish by NOAA Okeanos Explorer Program, Public domain, 2010
Fangtooth fish by Sandra Raredon-Smithsonian Institution, Public domain
Tripod fish have two pelvic fins and a tail fin that are elongated and can be filled with fluid to stiffen them, allowing the fish to stand on the ocean bottom while conserving energy. Two long, wavy pectoral fins act as arms to detect prey floating or swimming by and push the prey toward their mouths. Fangtooth fish is another species that can detect vibration and nearby movement. This species is only six inches in length, but have the largest teeth in proportion to their body size of any fish in the ocean. The long lower fangs fit into pouches in the roof of their mouths so their teeth do not pierce their brain cavity.
Dragonfish teeth array by UC San Diego Jacobs School of Engineering, May 2019
The dragonfish, another small fish about six inches long, has a frightening array of teeth located on its jaws and tongue. Their teeth are transparent and their bodies are black, making them impossible to see even in depths where there may be some light. The jaws are loosely hinged, allowing the fish to open its mouth wider than normally hinged jaws would allow. Prey swimming nearby may not notice the wide opening, nor be able to detect the transparent teeth, making the dragonfish a top predator of invertebrates, squid, and shrimp. In addition, when biting, they inject a highly toxic poison to paralyze and kill their prey. This toxin can be dangerous to humans getting bitten or attempting to eat this species.
Giant spider crab by Michael Coghlan, Jan 2014; Gulper eel by Claf Hong, Mar 2005; Lanternfish, Myctophum punctatum1 by Emma Kissling
Some fish practice diel vertical migration, a pattern of movement where a species feeds near the surface at night and moves back into deeper waters to rest during the day. Lanternfish come up to feed on zooplankton and fangtooth fish feed on squid in shallow waters. Some species, including anglerfish and gulper eels, have elastic-like skin for their mouths and stomachs. Mouths can be opened extremely wide to swallow prey larger then themselves. The food is contained in a similarly elastic stomach which shrinks slowly as digestion progresses. Several different species of spider crabs roam the ocean depths scavenging for meat or plant material that falls to the bottom.
Deep-sea animals are seldom seen, but are not immune from climate change and human impacts. Scientists continue to study changes in deep-sea food webs caused by overfishing, ocean acidification, and expanding low-oxygen zones. Learn more about the habitat and species of these areas at the Jurica-Suchy Nature Museum at Benedictine University or your local nature museum or aquarium.
The sei (SAY) whale, Balaenoptera borealis, is the third largest rorqual, a group of large baleen whales that feed by straining food from the water. They live 50 to 70 years and grow up to 60 feet in length, weighing 100,000 pounds. They have bluish-gray backs, creamy bellies, a tall, hooked dorsal fin, and a large mouth with 200-400 baleen plates made of keratin. Their skin is often marked with a series of curvy healed scars made by “cookie-cutter” sharks which attach themselves to large species with suction-cup lips hiding sharp teeth that cut out a section of flesh about two inches in diameter to eat.
Cetaceans of the Channel Islands National Marine Sanctuary, Sei Whale, Internet Archives-NOAA, 1987
There are two types of whales, toothed whales and baleen whales which are considerably larger, but have no teeth. Toothed whales and other cetaceans including dolphins and porpoises, have one blowhole leading to the left nasal passage. Baleen whales have both nasal passages open as two blowholes to accommodate their huge size, allowing a much greater air exchange when surfacing. In all cetaceans, muscles are contracted to open a nasal plug in the blowhole allowing them to breathe. When underwater, the muscles are relaxed, blocking the blowhole and preventing the animal from breathing in water. Air sacs immediately below the blowholes allow for creation of long, loud, low-frequency calls within the hearing range of humans. Most calls last less than one second and sound levels are equivalent to standing next to a jack hammer, carrying long distances underwater.
Sei whales are found in temperate oceans around the world, but not in polar or tropical waters. The southern sub-species population is slightly larger than the northern one, and there is no evidence of interbreeding. Current population estimates place a total of 80,000 individuals world-wide, but sei whales prefer deep ocean waters and rarely come near land making placement of tracking devices and accurate estimates difficult. Tagging has been moderately successful, with many lost signals. It is known that they migrate annually, following the available prey and using prevailing currents to move quickly, but exact migration routes and breeding areas are not yet known.
Sei whale feeding by Allison Henry, NOAA
Calanoid Copepod by Proyecto Agua
Sei whales generally travel alone or in small groups of up to six individuals. They are one of the fastest swimmers of all ocean species, attaining speeds up to 35mph for short distances. When feeding, they swim on their sides near the surface with one side of their huge mouths open taking in large amounts of water and straining out prey. Their favorite food is copepods, a tiny planktonic crustacean, but they will also consume krill, squid, and small schooling fish such as anchovies, sardines, and mackerel. They may make shallow dives to pursue schools of fish, quietly sinking below the surface; they can stay underwater for five to twenty minutes. Each whale consumes about 1,000 pounds of food daily.
Sei whale mother & calf, by Christin Khan, NOAA, Jun 2014
Sei whales reach sexual maturity between six and twelve years old, and a young adult is about 45 feet in length. Females are slightly larger than males. Gestation is 11 to 13 months, and each female mates once every two to three years. One calf is born in winter. A newborn is about fifteen feet in length and weighs 1500 pounds at birth. Calves remain with their mother for six to nine months before being weaned off its mother’s milk. Males are polygynous where one male has mating rights with several females.
Sei whales were overhunted in the mid-1960s for meat and oil after blue whale and fin whale populations were decimated in earlier years. They were added to the IUCN Red List as endangered in 1970. Their only natural predator is a pack of orcas. Massive die-offs have been recorded in the last fifty years, and evidence suggests the cause is red tides, a harmful algal bloom that severely depletes oxygen levels in large areas and may last for several weeks or months.
Red tide from NOAA, Jun 2009
Other threats include entanglement in fishing gear, leading to whales dragging the gear for long distances, ultimately tiring them to a point where feeding and breeding are impossible. Climate change affecting ocean water temperatures and currents is altering prey distribution and availability resulting in less successful foraging. Opening more shipping lanes in polar regions along the edges of sei whale territory, another result of climate change, contributes to more vessel strikes. Shipping also increases ocean noise, making long-range communications for all species more difficult; however, the impacts from this on the sei whale population is not well understood.
The sei whale remains a species with more mystery than knowledge. You can learn more about cetaceans in general from your local natural history museum or come to the Jurica-Suchy Nature Museum at Benedictine University to see a full skeleton of a sei whale on display.
