Seagrasses are integral to coastal ecosystems. They can be found in relatively small meadows between reefs and beaches or occupy huge savanna-like undersea prairies that, according to Smithsonian magazine, that “shapes life on Earth, from the food we eat to the air we breathe. And the more scientists learn, the more they say it’s in trouble.” There are 300,000 species of aquatic plants but only 70 species that have terrestrial ancestors. All of these are seagrasses.
“Seagrasses are the forgotten ecosystem,” Ronald Jumeau, a United Nations representative from the Republic of Seychelles, writes in a 2020 U.N. report. “Swaying gently beneath the surface of the ocean, seagrasses are too often out of sight and out of mind, overshadowed by colorful coral reefs and mighty mangroves.” But, he says, they “are among the most productive natural habitats on land or sea.” Emmett Duffy, director of the Smithsonian’s Tennenbaum Marine Observatories Network, shares that view of seagrasses as underappreciated but essential: “They’re like the Serengeti grasslands of Africa — but hardly anybody knows about them.”
Katherine Harmon Courage wrote in Smithsonian magazine, The seagrass “ecosystem, once you do see it, has a primal if uncanny draw, at once alien and familiar, a remembered dream of a submerged meadow. This may be because, unlike seaweeds (which are algae, not plants) and corals, seagrasses are terrestrial immigrants. When the largest dinosaurs were in their heyday, these grasses drifted from dry land into the sea.[Source: Katherine Harmon Courage, Smithsonian magazine, December 2020]
There are around 70 species of seagrasses. They have been around for millions of years and can be found in coastal shallows along every continent except Antarctica.. They cover around 300,400 square kilometers (116,000 square miles) — an area about the size of Italy — of the world’s ocean floors, typically in depths of less than three meters (ten feet). Most seagrasses reach a height of less than half a meter.
Species including the ribbonlike Zostera caulescens, which grows off the coast of Japan and can reach 11 meters (35 feet in length).Posidonia oceanica, commonly known as Neptune grass, is regarded by some as the most efficient natural carbon sink. It forms underwater meadows that flow in the water like grass fields in the wind. Eelgrass is a kind of seagrass that grows densely in some places in shallow local waters. The plant grows on ocean floors and keeps seawater and sand clean by providing oxygen. Like seaweed, eelgrass also serves as a life spawning site and nursery grounds for marine life, its colonies sometimes dubbed "ocean cradles." The eelgrass beds also hide marine creatures from their natural enemies. [Source: Tetsuya Akiyama and Masamine Kawaguchi, Yomiuri Shimbun, November 2010]
Websites and Resources: Animal Diversity Web (ADW) animaldiversity.org; National Oceanic and Atmospheric Administration (NOAA) noaa.gov; “Introduction to Physical Oceanography” by Robert Stewart , Texas A&M University, 2008 uv.es/hegigui/Kasper ; Fishbase fishbase.se ; Encyclopedia of Life eol.org ; Smithsonian Oceans Portal ocean.si.edu/ocean-life-ecosystems ; Woods Hole Oceanographic Institute whoi.edu ; Cousteau Society cousteau.org ; Monterey Bay Aquarium montereybayaquarium.org ; MarineBio marinebio.org/oceans/creatures
Seagrasses are marine plants that utilize photosynthesis to produce chemical energy, yielding oxygen. But like land grasses they flower but their leaves aren’t held up by rigid stems like terrestrial grasses. Instead they float. According to Smithsonian magazine: Like land grasses, they grow leaves, roots, rhizomes and veins. Their modest adaptations to the marine environment include aquatic pollination, neutrally buoyant seeds that can drift with the current before settling, and leaves that manage saltwater. [Source: Katherine Harmon Courage, Smithsonian magazine, December 2020]
“Seagrasses have survived, not just as species, but often as individual clones, for thousands of years. Scientists studying Posidonia oceanica meadows in the Mediterranean Sea estimate that the largest clone, which stretches more than nine miles, has been around, sending out slow-growing rhizomes, for tens of thousands of years, and possibly as many as 200,000 years. It could be the oldest-known organism on Earth.
For plants, they can be quite noisy. Carlos Duarte, a leading international seagrass expert at King Abdullah University of Science and Technology, on the banks of the Red Sea, in Saudi Arabia, describes a “scintillating sound when you lie in seagrass meadows,” which comes from the bursting of oxygen bubbles seagrasses produce and which sound, he says, “like little bells.” These faint peals may serve as clarion calls to some creatures that rely on seagrass meadows. For example, fish whose larvae, floating through the water column in search of a suitable place to land and mature, may depend on the sound for guidance.
World's Oldest Plants — Seagrass?
One of the oldest living organisms on Earth is a colony of Neptune grass (Posidonia oceanica) off of Spain in the Mediterranean Sea that is estimated to be between 80,000 and 200,000 years old. The Conversation reported: An ancient seagrass — Posidonia oceanica, which occurs only in the Mediterranean and Australian waters— that spans up to 15 kilometres and weighs more than 6,000 metric tonnes may be more than 100,000 years old — making it the oldest living organism, Australian researchers have found. The seagrass reproduces by asexually generating clones of itself, so meadows spanning vast areas of the seabed are genetically identical and counted as one organism. [Source: Justin Norrie, The Conversation, February 7, 2012]
Researchers from the University of Western Australia’s Ocean’s Institute analysed the DNA of the seagrass at 40 sites across 3,500 kilometres of the Mediterranean Sea, from Spain to Cyprus.
By calculating the plant’s annual growth rate, the team determined that the meadows are between 80,000 and 200,000 years old. Their findings are reported in the journal PLoS One. Previously, the oldest known living organism was a Tasmanian seagrass, Lomatia tasmanica, believed to be 43,600 years old. “Clonal organisms have an extraordinary capacity to transmit only ‘highly competent’ genomes, through generations, with potentially no end,” the Director of the Ocean’s Institute, Winthrop Professor Carlos Duarte, said.
But despite flourishing for so long, tests show they have waned across the world over the past 20 years. Posidonia oceanica meadows are now declining at an estimated rate of 5 percent annually. “The concern is that while Posidonia oceanica meadows have thrived for millennia, their current decline suggests they may no longer be able to adapt to the unprecedented rate of global climate change,” Professor Duarte said. Ocean acidification “and recent anthropogenic pressure on coastal areas resulting in changes in water quality, eutrophication, and nutrient load” were threatening the future of seagrasses, the team wrote in their paper.
World's Largest Plant — Seagrass?
The largest known plant on Earth — a seagrass roughly three times the size of Manhattan — was been discovered off the coast of Australia in the early 2020s. The BBC reported: Using genetic testing, scientists have determined a large underwater meadow in Western Australia is in fact one plant. It is believed to have spread from a single seed over at least 4,500 years. The seagrass covers about 200 square kilometers (77 sq miles), researchers from the University of Western Australia said. [Source: Tiffanie Turnbull — BBC News, June 1, 2022]
“The team stumbled upon the discovery by accident at Shark Bay, about 800 kilometers north of Perth. They had set out to understand the genetic diversity of the species — also known as ribbon weed — which is commonly found along parts of Australia's coast. Researchers collected shoots from across the bay and examined 18,000 genetic markers to create a "fingerprint" from each sample. They had aimed to discover how many plants made up the meadow. "The answer blew us away — there was just one!" said Jane Edgeloe, the study's lead author. "That's it, just one plant has expanded over 180 kilometers in Shark Bay, making it the largest known plant on Earth."
“The plant is also remarkable for its hardiness, having grown in locations across the bay with wildly variable conditions. "It appears to be really resilient, experiencing a wide range of temperatures and salinities plus extreme high light conditions, which together would typically be highly stressful for most plants," said Dr Elizabeth Sinclair, one of the researchers. The species generally grows like a lawn at a rate of up to 35 centimeters a year. This is how researchers estimated it has taken 4,500 years to sprawl to its current size. The research has been published in the journal Proceedings of the Royal Society B.
Benefits of Seagrass
Seagrass meadows are an important nearshore coastal habitats and ecosystems that provide nursery habitat for a variety of sea creatures, improve water quality and store carbon dioxide. Seagrass meadows alone account for 10 percent of the ocean’s total carbon storage despite only covering 0.2 percent of the seafloor.
Eel grass supports the life cycle of many fish and shellfish. 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. [Source: NOAA]
According to the Max Planck Institute for Marine Microbiology Seagrass meadows are amongst the top carbon-capturing ecosystems — just one square kilometer of seagrass stores nearly twice as much carbon as forests on land at a rate 35 times faster, according to the Institute An average forest stores about 100,000 tons of per square mile, An equivalent area of seagrass can hold nearly three times that amount. See Posidonia oceanica Above [Source: National Geographic]
Katherine Harmon Courage wrote in Smithsonian magazine, Throughout these millennia seagrasses have not only greened undersea landscapes but have also actively shaped them — “ecological engineers,” as researchers say. Roots hold seafloor sediment in place. Leaves help to trap floating sediment, improving water clarity. [Source: Katherine Harmon Courage, Smithsonian magazine, December 2020]
Seagrasses slow currents and help protect shorelines from storms. And they efficiently filter out polluting chemicals even as they cycle nutrients, oxygenate the water and pull carbon dioxide into the seafloor. The new U.N. report estimates that seagrasses may perform up to 18 percent of the ocean’s carbon sequestration, even though they cover only about 0.1 percent of the ocean floor.
Seagrass Meadows Produce Mountains of Sugar While Capturing CO2
Mountains of sugar have been found in the ocean under seagrass meadows according to researchers from the Max Planck Institute for Marine Microbiology. Isabella O'Malley from the Weather Network wrote: “Scientists conducted a study off the Italian island of Elba where they took samples of seagrass meadows and their surrounding sediments. Their data revealed that sugar concentrations underneath the seagrass were at least 80 times higher than those found in other marine ecosystems.“To put this into perspective: we estimate that worldwide there are between 0.6 and 1.3 million tons of sugar, mainly in the form of sucrose,” stated Manuel Liebeke, a scientist at the Institute, in a press release. “That is roughly comparable to the amount of sugar in 32 billion cans of Coke!” .[Source: Isabella O'Malley, Weather Network, May 23, 2022]
Seagrass consume significant levels of carbon dioxide because of their symbiotic relationship with bacteria in which both species benefit from each other. Sunlight allows the plant to capture carbon dioxide from the water and convert it into sugar molecules, which are made up of carbon, hydrogen, and oxygen. During periods of peak sunlight, such as the early afternoon or summer season, the plants produce more sugar than they need, so they store the extra sucrose around their roots in the seafloor.
Bacteria living around the plants’ roots consume this sugar, which gives the bacteria energy to produce more nutrients, such as nitrogen, that fertilize the seagrass meadows. This symbiotic relationship was documented for the first time by the research team and was published in Nature Ecology & Evolution.
The study reported that the giant piles of excess sugar were not being consumed by the bacteria due to phenolic compounds released by the seagrass, which cannot be digested by many microorganisms. This was a key finding for the researchers, as it confirms that the carbon in the sugar stays in these underwater ecosystems and out of the atmosphere. The research stated that if microorganisms consumed the sucrose stored by the roots of the seagrass, at least 1.54 million tons of carbon dioxide would be released into the atmosphere, which is equivalent to the carbon emissions from by 330,000 cars in one year.
Seagrass and Ocean Life
Seagrasses provide habitat for fish, sea horses, crustaceans and others; food for sea turtles, waterfowl and marine mammals; and nurseries for an astounding 20 percent of the largest fisheries on the planet. A blade of seagrass serves as refuge, habitat or nourishment for other organisms, from microalgae to crustaceans and worms.
Prawns and lobsters and a variety of fish depend on seagrass. Sea horses are often seen attaching themselves to blades of eelgrass as if seeking protection. Turtles and oysters are important in seagrass areas. Turtles trim the grass and keep it healthy. Oysters filter microbes in the water. Hunting turtles and dredging oysters allows the grasses to grow unchecked. When the growth is too explosive the grass roots it soaks up oxygen and release nutrients that algae and jellyfish fancy.
Seagrass meadows often serve as nurseries for young fish and shellfish like shrimps and crabs. The grass provides good hiding places for young fish and the water tends to be warmer than elsewhere and nutrients are in reasonably good supply. Nutrients are most plentiful in estuaries and near river mouths.
Harmon Courage wrote in Smithsonian magazine, Bright sunlight filters down through the clear Mediterranean waters off the coast of Spain, illuminating a lush meadow just below the surface. Blades of strikingly green grass undulate in the currents. Painted comber fish dart among clumps of leaves, and technicolor nudibranchs crawl over mounds. Porcelain crabs scuttle by tiny starfish clinging to the blades. A four-foot-tall fan mussel has planted itself on a rock outcropping. A sea turtle glides by. [Source: Katherine Harmon Courage, Smithsonian magazine, December 2020]
“A tiny fish called a bilobed ghost goby, notable for translucent skin, lives — and hides — amid seagrass. Indonesia: A tiny fish called a bilobed ghost goby, notable for translucent skin, lives — and hides — amid seagrass. Found in shallow waters from India to Indonesia’s Maluku Islands and north to Japan, the gobies grow to just over an inch long and feed on small crustaceans; despite their camouflage, the gobies, in turn, are prey to larger wrasses and juvenile groupers. (Shane Gross)
Seagrass, Turtles, Sharks and Dugongs
Seagrass beds, coral and mangrove islands are home to diverse species including reef sharks, Goliath groupers, rainbow parrotfish, long-spine sea urchins and hawksbill sea turtles. According to Smithsonian magazine, In the complex web of life sustained by seagrasses, a reticulate whipray, also known as a honeycomb stingray, feeds on invertebrates and fish. In the Red Sea green sea turtles feed on Halophila stipulacea, a tropical seagrass that is also native to the Indian Ocean and Persian Gulf. When young, the turtles eat a variety of plants and animals, but they become strict herbivores in adulthood. American crocodile live in the seagrass in the Jardines de la Reina, a marine park in Cuba protected since 1996 and regarded as a pristine Caribbean ecosystem. [Source: Katherine Harmon Courage, Smithsonian magazine, December 2020]
Bonnethead sharks, a species of hammerhead, live in shallow waters off both American coasts. In addition to a typical diet of crabs, clams, fish, squid and octopus, bonnetheads eat huge amounts of seagrass, and apparently not just by accident while gobbling prey. In fact, they digest about half of the green stuff — the only omnivorous shark species known to science. Dugongs are well-known residents of seagrass beds. Known as sea cows for their avid grazing as well as their bulk, these cousins of the manatee can grow to more than 450 kilograms (1,000 pounds) while feeding almost exclusively on seagrass — up to 40 kilograms (88 pounds) a day. In part because of this dependence, global dugong populations are in rapid decline.
The amount of seagrass world wide is being dramatically reduced by development and urban, agricultural and industrial pollution and stresses caused by climate. Change According to researchers at the Max Plank Institute up to 33 per cent of global seagrass may have already been lost, which the Institute stated is “comparable to the loss of coral reefs and tropical rainforests.”
In the coastal areas of Tokyo Bay eelgrass beds have died off due to industrial wastewater and reclamation projects. This drop-off, says local fishermen, has had a detrimental effect on local fish hauls. Katherine Harmon Courage wrote in Smithsonian magazine, Approximately 7 percent of global seagrass coverage disappears each year, similar to the loss of coral reefs and tropical rainforests. This decline also threatens species that depend on seagrasses for food and habitat, including endangered manatees, green sea turtles, chinook salmons, and dugongs, and it serves as a warning of greater devastation to come. [Source: Katherine Harmon Courage, Smithsonian magazine, December 2020].
“The assault on seagrasses comes in many forms. Fertilizer runoff fuels algae blooms, blocking the light needed for seagrasses to grow, as does excess topsoil runoff from coastal construction and development. Boat anchors and dredging uproot grasses and scar and fragment seagrass habitats. Overfishing large predators disrupts food chains, allowing mid-level predators to wipe out the worms and other small herbivores that usually clean algae off seagrasses. Rising sea temperatures threaten to outpace grasses’ ability to adapt or move, and exacerbate increasingly strong storms that can uproot entire meadows.
Sea urchins, which feed using a unique jawlike structure called Aristotle’s lantern, have been known to overgraze seagrasses. In parts of Australia, restrictions on harvesting sea urchins have been lifted specifically to protect seagrass. “Scars” causes by boat propellers and other man-made intrusions divide and isolate seagrass beds, increases erosion and makes coastal communities more vulnerable to storms. Researchers studying such gashes in Chesapeake Bay found that the beds can take 18 years to fully recover; sometimes, the scars never heal.
Seagrasses once thrived up and down the Eastern Seaboard of the United States. In some areas, such as the coastal waters off Virginia, meadows of Zostera marina, or eelgrass, were so abundant that, as recently as 100 years ago, local residents used clumps of the stuff that had washed ashore to insulate their homes. But in the 1930s seagrass meadows from North Carolina to Canada were practically eradicated, likely the result of a plague of slime mold disease combined with a devastating 1933 hurricane. Large swaths of coastal meadows had recovered by the 1960s, but important pockets remained barren.
Professor Eric Wolanski, from the Australian Center for Tropical Freshwater Research at James Cook University, who has spent several years studying seagrass off the coast of the Philippines, told The Conversation the meadows there had been reduced to just 5 percent of their original size. “That’s entirely due to human impact,” he said. “All over the world, seagrass has been very severely hit.” Seagrass meadows in the Great Barrier Reef that were wiped out by Cyclone Yasi in 2011 were reappearing much slower than hoped, Professor Wolanski said. “The water quality is making it much harder for them.” [Source: Justin Norrie, The Conversation, February 7, 2012]
The Centre for Ocean Research and Education, based on Eleuthera Island in the Bahamas, is evaluating the health of seagrasses in local waters, where sharks hold grazing turtles in check, and in a Caribbean site where shark populations have been nearly wiped out. Researchers have outfitted green sea turtles with radio-signal tags in order to track the animals to nesting and foraging grounds — and thus map thriving seagrass beds. [Source: Katherine Harmon Courage, Smithsonian magazine, December 2020]
Katherine Harmon Courage wrote in Smithsonian magazine,: “New international efforts are also underway to create an up-to-date map of seagrass colonies all over the world — a baseline for assessing what we stand to lose. “Getting an accurate global map of seagrass distribution is really important for understanding the fisheries that depend on them as well as their contributions to carbon storage,” says Duffy, of the Smithsonian.
Duffy and his colleagues are using drone imagery to study seagrasses along the North American Pacific Coast, where new outbreaks of slime mold disease, possibly fueled by warming ocean temperatures, threaten large seagrass meadows. Citizen scientists are pitching in, reporting seagrass locations with the smartphone app SeagrassSpotter. Duarte and others are even enlisting the help of radio signal-tagged creatures. “We are finding seagrass meadows by collaborating with sea turtles and tiger sharks,” Duarte says.
The abstract of a study published in Global Change Biology in 2021 read: To determine the status of seagrass meadows over time, we reconstructed time series of meadow area from 175 studies that surveyed 547 sites around the world. We found an overall trajectory of decline in all seven bioregions with a global net loss of 5602 kilometers2 (19.1 percent of surveyed meadow area) occurring since 1880. Declines have typically been non-linear, with rapid and historical losses observed in several bioregions. The greatest net losses of area occurred in four bioregions (Tropical Atlantic, Temperate North Atlantic East, Temperate Southern Oceans and Tropical Indo-Pacific), with declining trends being the slowest and most consistent in the latter two bioregions. In some bioregions, trends have recently stabilised or reversed. Losses, however, still outweigh gains. Despite consistent global declines, meadows show high variability in trajectories, within and across bioregions, highlighting the importance of local context. Studies identified 12 different drivers of meadow area change, with coastal development and water quality as the most commonly cited. Overall, however, attributions were primarily descriptive and only 10 percent of studies used inferential attributions. Although ours is the most comprehensive dataset to date, it still represents only one-tenth of known global seagrass extent, with conspicuous historical and geographic biases in sampling. It therefore remains unclear whether the bioregional patterns of change documented here reflect changes in the world's unmonitored seagrass meadows. The variability in seagrass meadow trajectories, and the attribution of change to numerous drivers, suggest we urgently need to improve understanding of the causes of seagrass meadow loss if we are to improve local-scale management. [Source: Jillian C. Dunic, Christopher J. Brown, Rod M.Connolly ,Mischa P. Turschwell,Isabelle M. Côté,Global Change Biology, May 15, 2021 ]
Replanting seagrass has rarely been successful because it goes not easily take hold. But Sites in Florida as well as Europe and Australia have succeeded in reviving seagrass populations, even with passive restoration efforts such as reducing fertilizer and soil runoff. Katherine Harmon Courage wrote in Smithsonian magazine:
“A group of scientists, including Robert Orth, a marine ecologist at the Virginia Institute of Marine Science, noted that there was no reason the region’s waters couldn’t sustain seagrass meadows once again. So the researchers had a wild idea: Why not reseed the historic eelgrass beds? Beginning in 1999, Orth and others dispersed 74.5 million eelgrass seeds into 536 restoration plots covering an area of close to a square mile. Now in its 21st year, it is one of the largest and most successful seagrass restoration efforts on the planet. [Source: Katherine Harmon Courage, Smithsonian magazine, December 2020]
Soon new eelgrass meadows spread rapidly on their own; today, new growth covers nearly 13 square miles. Within a few years, new plots were hosting a diverse range of returning fish and marine invertebrates and were sequestering more and more carbon over time. “It’s a good-news story,” says Orth, who has been studying seagrasses for half a century. “If the plants aren’t challenged by water quality, they can spread naturally very quickly.”
“Researchers are increasingly convinced of the value in working to expand seagrass beds, not just for the grasses’ own sake or for the marine creatures that depend on them, but for our own well-being. “If we invest in seagrasses, they can help us in lowering the global concentration of carbon dioxide,” says Jonathan Lefcheck, a research scientist at the Smithsonian’s Environmental Research Center. He notes that we are quick to recognize the importance of forests in keeping carbon out of the atmosphere. But a seagrass meadow can be just as effective as a temperate forest in sequestering carbon, sinking it into the sediment for decades or even centuries. “I’m pitching seagrasses as an ally in climate change,” he says. “They are an incredible ecosystem that continue to provide a wealth of benefits to humanity.
Eelgrass Restoration in Japan
Reporting from Hayamamachi, Kanagawa Prefecture in Japan, Tetsuya Akiyama and Masamine Kawaguchi wrote in Yomiuri Shimbun, “Standing on the shore, veteran fisherman Shiro Yajima looked wistfully at the ocean. "We used to be able to catch flounder and turbot right over there," he pointed. Yajima, 74, has spent many years catching fish and harvesting seaweed in Hayamamachi. "The fish came to eat bugs living on the eelgrass," he reminisced. [Source: Tetsuya Akiyama and Masamine Kawaguchi, Yomiuri Shimbun, November 2010]
Kajima Corp.'s Hayama Marine Science Laboratory also is investigating the role eelgrass plays in maintaining aquatic health. In 2005, the laboratory established the technology to effectively grow seedlings from eelgrass seeds. It then launched a project to revive eelgrass colonies in the area. The laboratory conducted seedling planting experiments in conjunction with the Kanagawa prefectural government and Hayamamachi Fishery Association.Lab researcher Katsunori Yamaki learned about eelgrass growth sites from the local fishermen. They had visited these sites to collect eelgrass samples in bloom.
In 2007, the laboratory established an association called the Hayama Amamo Kyogikai to support its research. Other members include a nonprofit organization and a local primary school that teaches students how to pick eelgrass seeds and grow seedlings.
Despite occasional typhoons, about 20 eelgrass beds have since taken root in an about 2,000-square-meter area near the beach. "The eelgrass colonies have had a positive effect on local marine life. Bigfin reef squid lay eggs on their stalks. Blue swimmer crabs have begun to populate the area," said a beaming Yamaki. Yet in Yokohama's Kanazawa Bay, the seafloor has become barren. Most of the local eelgrass beds died off due to this summer's heat wave.
The Amamo Revival Collaboration in Kanazawa-Hakkei, Tokyo Bay Area, along with some nonprofit organizations and the prefectural government, had been working to revive the area's eelgrass beds since 2001. To the distress of those involved, research conducted Nov. 20 revealed the animal population had dropped to 1 percent of that recorded in an August survey. "I was shocked to see [the local ecospecies] disappear over such a short period," said Takahiro Kudo, a chief researcher at the Kanagawa Prefectural Fisheries Technology Center in Miura. The results nonetheless highlight the synergetic relationship between eelgrass growth and healthy fish populations.
Image Sources: Wikimedia Commons; YouTube, Animal Diversity Web, NOAA
Text Sources: Animal Diversity Web (ADW) animaldiversity.org; National Oceanic and Atmospheric Administration (NOAA) noaa.gov; “Introduction to Physical Oceanography” by Robert Stewart , Texas A&M University, 2008 uv.es/hegigui/Kasper ; Wikipedia, National Geographic, Live Science, BBC, Smithsonian, New York Times, Washington Post, Los Angeles Times, The New Yorker, Reuters, Associated Press, Lonely Planet Guides and various books and other publications.
Last Updated March 2023