Ocean: quotes, facts and reflections - Page 2

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StillnessOcean

Marine snow is a continuous fall of organic particles, including plankton remains, mucus, faecal pellets and other debris, from upper waters into the deep sea.

Much of this material is eaten or broken down by bacteria on the way, and only a small fraction settles on the seabed, yet it is the main food supply for many deep-sea animals, far below where sunlight lets algae grow. Flakes grow as particles clump together and can sink tens to hundreds of metres a day. The name is often traced to the naturalist William Beebe, who saw particles drifting in his lights during bathysphere dives off Bermuda in the 1930s. Scientists measure the fall with sediment traps and underwater cameras, because it is a key part of the ocean's biological carbon pump: carbon taken up by plankton at the surface sinks, and what reaches the seabed can stay there for centuries or longer.

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WonderOcean

The barreleye Macropinna microstoma has tubular eyes beneath a transparent, fluid-filled shield, and can rotate them from looking upward to looking forward.

The barreleye lives about 600 to 800 metres down in the northern Pacific and grows to around 15 centimetres. It was described in 1939, but for decades it was known only from specimens hauled up in nets, which destroyed the soft shield, and its eyes were thought to be fixed, pointing straight up. Bruce Robison and Kim Reisenbichler of the Monterey Bay Aquarium Research Institute filmed living barreleyes off California with a remotely operated submersible and, in a 2008 paper, showed the green eyes turning inside the intact dome. The two dark spots above the mouth that look like eyes are in fact its organs of smell. Robison has suggested that the fish may steal food from siphonophores, stinging relatives of jellyfish, with the shield protecting its eyes.

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WonderOcean

A siphonophore, a relative of jellyfish, grows from a single fertilised egg into a colony of connected parts. Each part, called a zooid, takes on one job: swimming, feeding, defence or reproduction.

Siphonophores are cnidarians, the group that includes jellyfish and corals. The fertilised egg becomes a single founding zooid, which buds off all the others, so every part is genetically identical. Each zooid corresponds to a whole polyp or small jellyfish in related animals, but here it is specialised and cannot live alone, so the colony works like one body with organs. The best-known siphonophore is the Portuguese man o' war, whose painful sting comes from its feeding and defensive zooids. Many others are fragile, glassy animals of the deep sea. In April 2020 researchers filming in the Ningaloo Canyons off Western Australia found a giant Apolemia colony coiled in a spiral whose outer ring was estimated at about 47 metres, among the longest animals ever recorded.

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WonderOcean

When attacked, hagfish release mucus and microscopic protein threads that expand through seawater into extraordinary volumes of defensive slime.

Hagfish are eel-shaped, jawless fish that live on the seafloor. More than 70 species are known, and fossils about 300 million years old already look much like them. They often feed by burrowing into the carcasses of dead fish and whales. Their slime comes from glands along the body, which release mucus and tightly coiled protein threads. In seawater the threads unravel in a fraction of a second, and a small amount of secretion can turn litres of water into slime, enough to clog the gills of an attacking fish; underwater cameras have filmed sharks letting go and swimming off. Each thread is far thinner than a human hair yet strong and stretchy, so researchers study it as a model for new fibres. Afterwards the hagfish ties itself in a knot and slides the knot along its body to wipe the slime off.

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WonderOcean

Coccolithophores are tiny single-celled algae that cover themselves in intricate plates of chalk (calcium carbonate). Drifting in sunlit seawater in vast numbers, they link microscopic life to ocean chemistry and the global carbon cycle.

Each plate, called a coccolith, is a few thousandths of a millimetre across; it is built inside the cell and then pushed out to its surface. When coccolithophores die, their plates sink, and over millions of years thick layers of them have hardened into chalk: the White Cliffs of Dover are made largely of coccoliths laid down in the Cretaceous period, roughly 100 to 66 million years ago. The commonest species today, Emiliania huxleyi, forms blooms that turn the sea milky turquoise and can be seen from space. Coccolithophores take up carbon through photosynthesis, and their sinking plates carry carbon to the seabed, where scientists read their fossil remains to reconstruct past climates.

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WonderOcean

The Antarctic Circumpolar Current flows uninterrupted around Antarctica, connecting the Atlantic, Pacific and Indian oceans while transporting heat, nutrients and carbon.

The current flows eastwards, pushed by strong westerly winds, and is the strongest current system in the world's oceans. Estimates of its flow range from about 135 to 175 sverdrups (one sverdrup is a million cubic metres of water per second), well over a hundred times the flow of all the world's rivers combined. It could form only after South America and Australia pulled away from Antarctica, opening the Drake Passage and the Tasmanian Seaway; many scientists date its start to about 34 million years ago, though the timing is debated. By keeping warmer water away from the continent, the current helped Antarctica's great ice sheets grow, and today it carries heat and carbon between the Atlantic, Pacific and Indian oceans.

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WonderOcean

In polar seas, strong winds or warmer water welling up from below can keep patches of sea open where thick ice would normally form. These areas of open water or thin ice are called polynyas.

The name comes from a Russian word for a patch of open water in ice. Polynyas matter to wildlife: seals, walruses, whales and seabirds use them to breathe and feed. As new ice keeps forming at their edges, it leaves its salt behind in very dense water, which sinks and helps drive deep ocean currents. The North Water, between Greenland and Canada's Ellesmere Island, is one of the Arctic's richest wildlife areas; the Inuit call it Pikialasorsuaq, 'the great upwelling'. Other polynyas are rare: the Weddell Sea polynya in Antarctica, seen by satellite in the mid-1970s, opened again briefly in 2016 and 2017, and scientists are still working out what triggers it.

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WonderOcean

Male humpback whales in a population share an evolving song, and novel song types can spread between populations through social learning rather than genes.

Only male humpbacks sing, mostly in the breeding season: a long, repeated sequence of moans, cries and pulses, built from phrases and themes. All the males in one area sing nearly the same song, and it keeps changing as singers add small variations that the others copy. Sometimes the change is sudden. In 1996, researchers off eastern Australia recorded two males singing a song that belonged to the population off western Australia; within two years every singer they recorded had switched to it. Their report in Nature in 2000 called it a cultural revolution, because such a rapid, complete change can only spread by learning. Later studies traced new songs moving eastward, population by population, across the South Pacific.

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WonderOcean

Along some coasts, winds push surface water out to sea and cold, nutrient-rich water rises from the depths to take its place. This upwelling feeds plankton and, through them, some of the richest fishing grounds on Earth.

Five coastal upwelling zones stand out: the Humboldt Current off Peru and Chile, the California Current, the Canary Current off north-west Africa, the Benguela Current off south-western Africa and the Somali Current off Somalia and Oman. Together they cover only about 5 per cent of the ocean, yet they yield roughly a quarter of the world's marine fish catch, much of it small fish such as anchovies and sardines. Off Peru, the anchoveta supports one of the largest single-species fisheries in the world. That richness is fragile. During an El Niño, warm water spreads along the South American coast and weakens the upwelling, so fewer nutrients reach the surface and anchovy numbers crash, along with the seabirds and sea lions that feed on them. The El Niño of 1972 to 1973, on top of heavy fishing, helped bring Peru's anchovy fishery to collapse.

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DriveClimate

A marine heatwave is a spell of unusually warm sea water lasting from days to months. It can kill kelp forests and corals, drive fish and other animals into new waters and upset fisheries.

Under a definition widely used since 2016, an event counts as a marine heatwave when the water stays warmer than 90 per cent of past readings for that place and time of year for at least five days. The term itself was coined after an unprecedented event off Western Australia in the summer of 2011, when warm water killed kelp forests, underwater forests of large brown seaweed, along hundreds of kilometres of coast. In many places the kelp did not come back: low, turf-like seaweeds and fish more typical of warmer waters took over, and the reef became a different kind of ecosystem. Another well-known case was the Blob, a mass of warm water that sat in the north-east Pacific from 2014 to 2016 and disrupted marine life and fisheries along the west coast of North America.

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WonderArchaeology

The Dover Bronze Age Boat, found under a road in Dover in 1992, was built about 3,500 years ago from oak planks sewn together with yew and made watertight with moss and animal fat.

Workers building the A20 road between Folkestone and Dover uncovered the boat on 28 September 1992, six metres below the surface. Waterlogged, airless ground had kept the oak from rotting. Archaeologists worked for nearly a month to lift a 9.5-metre section; the rest ran under nearby buildings and had to be left in place. The planks are held together by twisted yew stems and by wooden wedges driven through cleats, raised blocks carved out of the planks themselves. It is dated to about 1575 to 1520 BCE, which makes it one of the oldest seagoing boats known. Whether it ever crossed the Channel is still debated. It is on display in Dover Museum.

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WonderArchaeology

Nan Madol, off the island of Pohnpei in Micronesia, is a ruined city of basalt walls, tombs and ceremonial buildings on roughly a hundred artificial islets divided by tidal channels.

Islet-building began by the 8th or 9th century, and the great basalt walls went up from about 1180–1200. The site became the ceremonial and political seat of the Saudeleur dynasty, which ruled a united Pohnpei until about 1628; rival chiefs were made to live there, where they could be watched. The builders used long, naturally many-sided columns of basalt, quarried elsewhere on Pohnpei and brought to the site, stacking them in alternating crosswise and lengthwise courses around platforms filled with coral rubble. How they moved and raised such heavy stone is not recorded. The mortuary sector, Madol Powe, includes the walled royal tomb islet of Nandauwas. UNESCO listed Nan Madol in 2016 and placed it at once on its List of World Heritage in Danger, as silt and mangroves were choking the channels.

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WonderEngineering

A Fresnel lens replaces the thick curved glass of an ordinary lens with thin concentric rings, each shaped to bend light at the right angle. Invented for lighthouses in the 1820s, it focuses light just as strongly with far less glass and weight.

In 1819 the French physicist Augustin-Jean Fresnel, working for France's lighthouse commission, proposed a stepped lens to replace the metal reflectors then in use, which returned only about half of a lamp's light. A full-size lens was tested in Paris in 1822, and on 25 July 1823 the first lighthouse Fresnel lens was lit at Cordouan, at the mouth of the Gironde; its light could be seen more than 32 kilometres out to sea. A solid lens of the same power would have been impossibly thick and heavy. Later improved with glass prisms that also sent stray light towards the horizon, the design spread to lighthouses around the world, and it has been called the invention that saved a million ships.

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WonderEngineering

The Plimsoll line, a circle with a line through it painted on a ship's hull, marks how deep a loaded ship may safely sit in the water. Extra lines beside it allow for fresh water, tropical water and winter seas, where the safe limit is different.

The mark is named after Samuel Plimsoll, a British member of parliament who campaigned in the 1870s against “coffin ships”: vessels sent to sea overloaded and often over-insured, so that owners could profit even if the ship sank and its crew drowned. His 1873 book Our Seamen stirred public anger, and the Merchant Shipping Act of 1876 made the load-line mark compulsory on British ships. International conventions in 1930 and 1966 extended load lines to ships worldwide. The letters beside the mark stand for tropical fresh water (TF), fresh water (F), tropical (T), summer (S), winter (W) and winter North Atlantic (WNA). Canvas plimsoll shoes are said to take their name from the band where the upper meets the sole, which recalls the line.

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WonderTrade

In the Kula ring of Papua New Guinea's Massim islands, partners sail between islands to exchange shell valuables: red necklaces travel clockwise around the ring and white armbands anticlockwise. No one keeps them for good; each is passed on and carries the story of those who held it.

The necklaces are called soulava and the armbands mwali. A participant receives one from a partner on one island and, after a time, passes it on to a partner on another, so the same objects keep circling for generations; famous pieces have their own names and histories. The Polish-born anthropologist Bronisław Malinowski lived in the Trobriand Islands during the First World War and described the Kula in Argonauts of the Western Pacific (1922), one of the founding books of modern fieldwork. He showed that it was not barter: prestige came from taking part, from generosity and from being trusted with valued pieces, while ordinary trade in goods went on alongside the ceremonial exchange. The Kula still continues today.

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WonderHistory

Navigators of the Marshall Islands made stick charts that show how ocean swells bend around islands. Curved sticks stand for the swell patterns, and shells or the points where sticks cross mark the islands.

The charts were made from the midribs of coconut palm leaves tied with coconut fibre. Marshallese navigators used three main kinds: a mattang taught the general principle of how swells bend and meet around an island; a meddo showed a few real islands and their swell patterns; a rebbelib covered a whole chain of islands. The knowledge was guarded and passed on within families of navigators. Charts were studied and memorised on land, not carried at sea. Out on the ocean a navigator felt the crossing swells through the motion of the canoe, sometimes lying down in the hull to sense them better, and so could tell where an island lay long before it came into view. Western visitors first described the charts in the second half of the nineteenth century.

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WonderScience

Marie Tharp, an American geologist, drew the first detailed maps of the Atlantic seafloor from ships' depth readings. In the early 1950s she found a deep valley running along the middle of the undersea Mid-Atlantic Ridge, strong evidence that the seafloor is spreading apart.

Tharp joined Columbia University's Lamont Geological Observatory in New York in 1948. Women were not allowed to work on its research ships, so for nearly two decades her colleague Bruce Heezen collected echo-sounder depth readings at sea while she turned them into profiles and maps ashore. In 1952 she spotted a V-shaped valley along the crest of the Mid-Atlantic Ridge, an undersea mountain chain longer than any range on land, and read it as a rift where the seafloor is pulling apart. Heezen at first dismissed it as 'girl talk', because it supported continental drift, then a controversial idea. He changed his mind when a separate map of undersea earthquakes lined up with her valley. With the Austrian painter Heinrich Berann, they published The World Ocean Floor map in 1977.

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WonderBiography

American biologist Ernest Everett Just showed that an egg cell's surface changes rapidly at fertilisation and helps stop extra sperm from getting in. Working with sea urchins and other marine animals, he insisted that cells be studied in conditions as close to natural as possible.

Just taught at Howard University in Washington from 1907 until his death and spent some twenty summers at the Marine Biological Laboratory in Woods Hole, Massachusetts, where his careful handling of marine eggs made him a sought-after expert. He described what is now called the fast block to polyspermy, the rapid change that keeps a second sperm out of the egg. In 1915 he became the first person to receive the Spingarn Medal from the US civil rights organisation NAACP. Racism kept him out of posts at major American research universities, so from 1929 he worked more and more in Europe: at the Stazione Zoologica in Naples, the Kaiser Wilhelm Institute in Berlin and later Roscoff in France. His 1939 book The Biology of the Cell Surface argued that the cell's outer layer, not only the nucleus, drives development. He died in 1941.

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WonderOcean

Argo is a fleet of nearly 4,000 robotic floats that drift through the world's oceans, sinking to about 2,000 metres and rising again to measure the water's temperature and saltiness. At the surface each float sends its data by satellite, free for anyone to use.

A typical float drifts for most of its cycle at about 1,000 metres, then sinks to about 2,000 metres and measures the water as it rises to the surface, completing each cycle in roughly ten days. The programme began around 2000, and in November 2007 it reached its goal of 3,000 floats spread across the open ocean. Its name comes from the Argo, the ship of Jason in Greek myth, because the floats work alongside the Jason satellites that measure sea level. Newer Biogeochemical-Argo floats also carry sensors for oxygen, acidity, nutrients and chlorophyll, the green pigment of microscopic ocean plants. Before Argo, most deep-ocean measurements came from ships on a few busy routes; now scientists can follow how the whole ocean is warming.

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DriveHistory

Ernest Shackleton's ship Endurance was crushed by sea ice and sank in Antarctica's Weddell Sea in 1915. After months camped on drifting ice and an 800-mile open-boat voyage to fetch help, all 28 men survived. The wreck was found in 2022, almost intact.

After Endurance was trapped and crushed by the Weddell Sea ice, the crew camped on drifting floes before taking three lifeboats to Elephant Island, a bare island off the Antarctic Peninsula. Shackleton and five companions then sailed the lifeboat James Caird about 1,300 kilometres (800 miles) to South Georgia. With two of them, Frank Worsley and Tom Crean, he crossed the island's mountains on foot to reach a whaling station, then organised the rescue of the men left behind. The 22 men on Elephant Island were picked up on 30 August 1916. In March 2022 the Endurance22 expedition found the wreck 3,008 metres down on the floor of the Weddell Sea, remarkably well preserved.

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