OUR OCEAN PLANET

1. OUR OCEAN PLANET OUR OCEAN PLANET SECTION 9 – DEEP OCEAN

2. REVISION HISTORY

3. 9. DEEP OCEAN 9. DEEP OCEAN

4. 9. DEEP OCEAN The ocean is deep and can be vertically divided into several zones based on depth and light penetration: Photic Zone The Photic or Euphotic (eu–good; photic–light) Zone is the top 200 m (660 ft) of the ocean and is defined by the limit of sunlight’s ability to penetrate any deeper. The deep ocean starts at the end of the Photic Zone in the Twilight Zone. Twilight Zone The Twilight or Dysphotic (dys–bad; photic–light) Zone is a region of dim light and semi-darkness where there is no longer enough sunlight for photosynthesis. As a result, there is very little phytoplankton (e.g. algae and plant life) in this zone and below. However, animal life can be found here. For example, zooplankton (e.g. copepods) hides here during the day before coming to the surface at night to feed. Dark Zone The Dark or Aphotic (a–without; photic–light) Zone lies below the Twilight Zone and starts at about 1,000 m (3,300 ft) and extends to the greatest depths of the ocean. This zone is completely dark. The pressure is over 100 times that of the surface and the water temperature is just above freezing.

5. 9. DEEP OCEAN Abyss The Abyss is within the Dark Zone and lies at about 4,000 m (13,200 ft). Around that depth, the sea bed is mostly flat and almost level with just a small gradient (1:1000 or less). The abyssal plain covers over half the ocean area and is the largest single environment on Earth. The abyssal plain, however, is not always completely flat and uniform. In some places, the seabed drops suddenly to the deep trenches. In other places, volcanoes rise up from the sea floor. Where these volcanoes reach above the ocean surface they form islands (e.g. the Hawaiian islands). If they remain below the surface, they are called seamounts. The abyssal plain is broken up by huge mountain chains known as mid-ocean ridges. Here, molten rock rises from deep within the Earth and spreads out to form new sea floor. Sea water percolates through fissures in the rock and is super-heated by the rocks of the oceanic crust. It then rushes back to the surface where it gushes out at a hydrothermal vent. Trenches At the very bottom of the ocean lie the deep sea trenches, such as the Marianas and Cayman Trenches. The Marianas Trench is 11,022 m (36,161 ft) below sea level and is the deepest part of the ocean.

6. 9. DEEP OCEAN DEEP OCEAN CHARACTERISTICS Some of the characteristic features of the deep ocean are: (a) Dark The deep ocean starts in the Twilight Zone at about 200 m (660 ft) and below. The Twilight Zone is where there is no longer enough sunlight for photosynthesis and thus, there are very few plants in this zone and below. However, animal life can be found. Many animals hide here during the day before coming to the surface at night to feed. (b) Cold At the surface, the water temperature varies depending on whether you are in tropical, temperate or polar regions. In the tropics, for example, the surface water temperatures may be 25°C (77°F) or higher. However, below 1,000 m (3,280 ft) in depth, temperatures are remarkably similar throughout the ocean and range from 4°C (39°F) to -1°C (30°F).

7. 9. DEEP OCEAN (c) Enormous Pressure The change in pressure between the surface and the deep ocean is tremendous. At the surface, the pressure is just 1 atmosphere (14.7 lbs per sq. inch or 101,325 pascals). Pressure increases by 1 atmosphere for each ten metres of depth. At 1,000 m (3,280 ft), the pressure will have increased 100 times. By 10,000 m (32,808 ft), the pressure will be 1,000 times that at the surface – just over 1 tonne per sq cm. (d) Alternative Energy Sources To Sunlight For many years, it was thought that life would not and could not survive in the depths without sunlight. However, more recently, alternative sources of energy to sunlight have been discovered. This energy comes from the planet itself and takes the form of hydrothermal energy.

8. 9. DEEP OCEAN (e) Relatively Unexplored & Almost Completely Unknown The deep sea is the largest habitat for life. By volume, it makes up almost 80% of the available space and yet it remains the least-known part of our world. The main reason for this is the logistical and technical difficulties of reaching depths where water pressures can crush even the most robust submersibles. We have only just begun to explore the deep ocean and have literally just dipped our toes into the water. (f) Challenge For Next Generation The ocean is the last and largest unexplored place on Earth – less than 5% of it has been explored. This is the great frontier for the next generation’s explorers and researchers, where they will find great opportunities for inquiry and investigation.

9. 9.1 LIFE IN THE DEEP 9.1 LIFE IN THE DEEP

10. 9.1 LIFE IN THE DEEP 9.1 LIFE IN THE DEEP 9.1.1 The Deep Life exists in the deep but, because of the dark, cold, and pressure, it needs special adaptations that allow it to survive. Without plants, animals must be highly-efficient predators or scavengers feeding off dead materials. Many must also be opportunistic and take whatever is offered. TWILIGHT ZONE LIFE In the twilight zone, many animals are transparent or silvery so that they can hide from predators in the semi-darkness. For example, the deep sea squid Vitronella has an almost completely transparent body which makes it very hard to spot in the gloom. Some animals here can generate their own light through a process called bioluminescence. Here, special cells called photophores on an organism’s body generate light which serves a range of functions including illuminating prey, luring prey and confusing predators. Animals in the twilight zone tend to have large eyes that use the miniscule amount of light that still exists to hunt prey. They also have long, sharp teeth and gaping jaws to help them seize prey. These teeth make many deep sea creatures look nightmarish and ferocious. For example, Winteria have very large eyes to help them see prey while hatchetfish have long sharp teeth to catch prey.

11. 9.1 LIFE IN THE DEEP Animals may also have tentacles, stinging cells (nematocysts) and potent poisons to help catch and kill prey quickly. For example, true jellyfish, siphonophores, and comb jellies are transparent animals with stinging cells that capture fish, shrimps and other jellyfish. One of the largest siphonophores can reach 40 m (131 ft) in length making it one of the longest animals on Earth. Sperm whales are among the deepest diving mammals and can dive to about 1,000 m (3,281 ft) or the end of the Twilight Zone in search of food such as giant squid. Some examples of animals that live in the Twilight Zone are: • Cnidarians – True jellyfish, siphonophores • Comb jellies • Molluscs - giant and other squid (e.g. Vitronella), Nautilus • Fish – Winteria, hatchetfish • Mammals - sperm whale

12. 9.1 LIFE IN THE DEEP DARK ZONE, ABYSS & TRENCH LIFE In the Dark Zone and below, it is perpetually dark because no light from the sun penetrates to these depths. Here, there is no benefit to being transparent or counter-shaded. As a result, creatures in the Dark Zone are usually black or deep red (without visible light, red cannot be seen so red creatures also appear black). For example, dark-zone shrimp are deep red in colour. Animals in the Dark Zone are also frequently grotesque in appearance and have poor vision. Most produce their own light (bioluminescence) to attract prey, to alarm or confuse predators, as a headlight to see, or as a means of communication with other animals of their own species. For example, Anglerfish use bioluminescent symbiotic bacteria at the ends of modified dorsal fins that glow and attract prey. Only about 5% of the food from the Photic Zone floats down into the Dark Zone and food is very scarce. Animals also cannot migrate up the water column to the Photic Zone – it is too far and the changes in pressure are too great. Animals must, therefore, either wait for food to come to them or lure food to them.

13. 9.1 LIFE IN THE DEEP The cold dark conditions and lack of food mean that many animals are sedentary and sluggish with weak muscles and skeletons. Fish also do not have functional swim bladders and generally move as little as possible to conserve energy. They also have poor vision but are highly sensitive to vibrations (and potential prey) in the water. Many are opportunists and must eat whatever is available. As a result, they have a variety of adaptations, such as bioluminescent lures, long sharp teeth, big mouths, jaws that can open widely and expandable stomachs, to deal with varied and unexpected prey. For example, gulper eels have massive mouths and highly expandable stomachs, and are able to swallow prey much larger than themselves. Some examples of animals that live here include: • Cnidarians – true jellyfish (e.g. Periphylla, Atolla) • Crustaceans – red deep sea shrimp • Molluscs – squid (e.g. Vampyroteuthis infernalis) • Fish – anglerfish, gulper eel, dragonfish

14. 9.1 LIFE IN THE DEEP DEEP SEA FLOOR LIFE Most of the deep-sea bed is flat and somewhat featureless. Animals here face the same challenges as those throughout the deep sea. It is dark and cold and there is very little food. Most animals found here are either permanently attached to the bottom or stay close to it Most of the animals in the mud are just a few millimeters long. The most numerous are the foraminiferans. These single-celled animals feed off bacteria and other organic matter and construct their homes from mud and pieces of animal shell. The most numerous multi-cellular animals are the nematodes or roundworms. They range in length from a few tenths of a millimeter to more than a centimeter. They vary from bacterial grazers to predators. Other common deep-sea animals are isopods, predatory polychaete worms and numerous small bivalve molluscs. Sea cucumbers are probably the dominant life form on the deep sea floor representing as much as 95% of the total biomass. Many are cylindrical and look like sausages or dung. Other echinoderms include brittle stars and sea urchins. Brittle stars are found worldwide as deep as 7,000 m (22,966 ft).

15. 9.1 LIFE IN THE DEEP • Rattail fishes are found from about 250 m (820 ft) down to the bottom of the deepest trenches. These scavengers are the most abundant fish of the deep-sea floor. Tripod fish are also found on the deep-sea floor propping themselves up on their long pelvic and caudal fins to catch prey. Deep sea sharks, such as sleeper sharks are found at depths of 2,200 m (7,218 ft) while six-gill sharks are found in waters as deep as 2,500 m (8,202 ft). • Some examples of animals that live here include: • Foraminiferans • Tubeworms • Sponges – deep sea sponges • Cnidarians – deep sea corals, sea anemones, sea pens • Nematodes (round worms) • Isopods • Polychaete worms • Cnidarians – deep sea anemones • Echinoderms – sea cucumbers, brittle stars, sea urchins • Fish – rattail, tripod fish, sleeper sharks, six-gill sharks REFERENCES & FURTHER READING Byatt, Andrew, Fothergill, Alastair and Holmes, Martha, The Blue Planet: Seas of Life, Chapter 7, DK Publishing Inc., (2001), ISBN 0-7894-8265-7

16. 9.1 LIFE IN THE DEEP 9.1.2 Deep Ocean Life

17. 9.1 LIFE IN THE DEEP SPERM WHALE Sperm whales (Physeter macrocephalus) are easily recognized by their massive heads and prominent rounded foreheads. They are about 18 m (59 ft) in length and weigh 40.8 metric tons (45 tons). They have the largest brain of any creature known to have lived on Earth. Their heads also hold large quantities of a substance called spermaceti. Whalers once believed that the oily fluid was sperm. While that is not true, scientists still do not understand spermaceti’s function. One theory is that the fluid (which hardens to wax when cold) helps the whale alter its buoyancy so it can dive deep and rise again. Sperm whales are known to dive as deep as 1,000 m (3,280 ft) in search of squid to eat. These giant mammals must hold their breath for up to 90 minutes on such dives. Sperm whales eat about 907 kg (1 ton) of fish and squid a day. Sperm whales are vocal and emit a series of "clangs" that may be used for communication or echolocation. They are often seen in pods of 15-20 animals. Pods include females and young whales while males may roam alone or move from group to group. Females and calves remain in tropical or subtropical waters all year long. Males migrate alone or in groups to higher latitudes but head back towards the equator to breed. Driven by their tail fluke which can be 5 m (16 ft) from tip to tip, they can cruise the oceans at around 37 kph (23 mph).

18. 9.1 LIFE IN THE DEEP GIANT SQUID The giant squid (Architeuthis dux) remains largely a mystery to scientists despite being the biggest invertebrate on Earth. The largest giant squid ever found measured 18 m (59 ft) in length and weighed nearly 900 kg (1,984 lb). Like other squid, they have eight arms and two longer feeding tentacles that bring food to their beak-like mouths. Their diet likely consists of fish, shrimp, and other squid and some suggest they might even attack and eat small whales. They maneuver their massive bodies with fins that seem diminutive for their size. They use their funnel as a propulsion system, drawing water into the mantle, or main part of the body, and forcing it out the back. Giant squid (and colossal squid) have the largest eyes in the animal kingdom, measuring some 25 cm (10 in) in diameter. These massive organs allow them to detect objects in the lightless depths where most other animals would see nothing. The deep-sea habitat has made them difficult to study and almost everything known about them is from carcasses that have washed up on beaches or been hauled in by fishermen. Even their range is not completely clear but giant squid carcasses have been found in many of the world's oceans.

19. 9.1 LIFE IN THE DEEP NAUTILUS The chambered nautilus (Nautilus pompilius) is about 25 cm (10 in) in length. During prehistoric times there were about 10,000 different species of nautilus but only two are known to survive today. It is a mollusc and a member of the cephalopod family. Like most cephalopods, it can use jet propulsion to move. A small tube called a siphon, near the animal's tentacles, expels water under pressure. This propels the nautilus in the opposite direction at high speeds. The nautilus shell is comprised of many individual chambers. Each chamber is individually sealed and contains an amount of gas which gives the animal buoyancy. The nautilus can regulate its density by injecting or removing fluid into these chambers through a system of tubes. This strong shell also provides protection for the soft body of the nautilus. When a young nautilus first hatches from an egg, it is about 2.5 cm (1 in) in diameter and has a shell with seven chambers. The young will drift and feed on plankton as it grows. As the nautilus gets larger, it will add new chambers to its shell. Each new chamber will be a little larger that the last, allowing the opening of the shell to continually grow larger. A unique feature of the nautilus is that its eye contains no lens – it contains only a tiny hole and operates like a pinhole camera. Nautiluses are found throughout the Pacific and Indian oceans where they spend their daylight hours at depths of about 550 m (1,800 ft). At night they rise and travel to the coral reefs to feed.

20. 9.1 LIFE IN THE DEEP ANGLERFISH There are more than 200 species of anglerfish, most of which live in the murky depths of the Atlantic and Antarctic oceans up to a mile (1,609 m) below the surface although some live in shallow tropical environments. Generally dark gray to dark brown in colour, they have huge heads and enormous crescent-shaped mouths filled with sharp, translucent teeth. Some anglerfish can be quite large, reaching 1 m (3.3 ft) in length and weighing up to 50 kg (110 lbs). Most however are significantly smaller and are often less than 0.3 m (1 ft) in length. Their most distinctive feature is a piece of dorsal spine that protrudes above a female’s mouth like a fishing pole (hence their name). Tipped with a lure of luminous flesh, this fishing rod lures prey close enough to be snatched. The anglerfish's lighted lure glows with the help of millions of bioluminescent bacteria. Their mouths are so big and their bodies so pliable, they can actually swallow prey up to twice their own size. The male, which is significantly smaller than the female, does not have this adaptation. Instead of continually seeking the abyss for a female, it has evolved into a permanent parasitic mate. When a young, free-swimming male angler encounters a female, he latches onto her with his teeth. Over time, the male physically fuses with the female, connecting to her skin and bloodstream and losing his eyes and all his internal organs except the testes. A female will carry six or more males on her.

21. 9.1 LIFE IN THE DEEP GULPER EEL The umbrellamouth gulper eel’s (Eurypharynx pelecanoides) most notable attribute is the large mouth. The eel's jaws are loosely hinged, and can be opened wide enough to swallow an animal much larger than itself. It primarily feeds on crustaceans but it also feeds on fishes, cephalopods and other invertebrates. The prey is deposited into a pouch-like lower jaw (somewhat like that of a pelican). The gulper's stomach can also stretch to accommodate its large meals. The eel also has a very long, whip-like tail. Specimens that have been brought to the surface in fishing nets have been known to have their long tails tied into several knots. The gulper eel grows to a length of about 2 m (6.5 ft) and is found in all of the world's oceans at depths ranging from 915-1,830 m (3,000-6,000 ft). SIX-GILL SHARK The six-gill shark (Hexanchus griseus) has, as its name implies, six gill slits and a spiracle. It also has a long caudal (tail) fin and is coffee-coloured to brown or grayish on its back and paler below. The six-gill shark mainly lives in deep water. It is a large shark that can reach 4.9 m (16 ft) and weigh 590 kg (1,300 lbs).

22. 9.1 LIFE IN THE DEEP SEA CUCUMBER The sea cucumber is an echinoderm with an elongated body and leathery skin which is found on the sea floor worldwide. It is so named because of its cucumber-like shape. Sea cucumbers are generally scavengers feeding on debris in the benthic zone of the ocean. Most sea cucumbers eat plankton and decaying organic matter found in the sea. Some sea cucumbers position themselves in currents and catch food that flows by with their open tentacles. They may also sift through bottom sediments using their tentacles. Sea cucumbers live in tropical reefs. Some species can defend themselves by expelling their insides to entangle potential predators in a process known as “evisceration”. SEA ANEMONE Sea anemones are simple animals (cnidarians) that are often attached to the sea bottom. Sea anemones have cylindrical bodies that are surrounded by upward-facing tentacles. The tentacles have stinging cells on them which kill prey and move the food into a sea anemone’s mouth. The mouth leads into the body cavity which digests the food. A continuous current of water through the mouth circulates through the body cavity and removes waste. Sea anemones are found in cold and warm waters. Many are colourful, and large species can be 1 m (3 ft) in diameter.

23. 9.1 LIFE IN THE DEEP TRIPOD FISH The tripod fish (Bathypterois grallator) is an unusual bathypelagic (deep sea) fish and is named for the long extensions of its pelvic and lower caudal fins on which it stands on the sea floor. Tripod fish are relatively small – the largest measuring only 37 cm (14.5 in). However the three elongated fins of the tripod fish may extend to 1 m (39 in) in length. The fish is slender, deeper than it is wide and has very small eyes. Tripod fish are sensitive to the vibrations of other animals in the water. In addition to its tripods, it also has unusually large pectoral fins. The tripod fish is relatively sedentary and spends much of its adult life standing on its fins on the ocean bottom. It stands facing the prevailing current and hunts by extending its unusually long pectoral fins into the current and waiting for small crustaceans to bump into its fins. The fish grasps its prey with its pectoral fins and directs it toward its mouth. The extensions of the pelvic and caudal fins are stiff enough for the fish to stand on them for extended periods of time. However, the tripods are flexible enough for swimming. Tripod fish are found at depths of 900-3,500m (2,950-11,500 ft) and are distributed in all oceans in equatorial regions.

24. 9.1 REFERENCES & ADDITIONAL READING REFERENCES & ADDITIONAL READING http://animals.nationalgeographic.com/animals/fish/anglerfish.html - Anglerfish http://animals.nationalgeographic.com/animals/invertebrates/giant-squid.html - Giant squid http://animals.nationalgeographic.com/animals/mammals/sperm-whale.html - Sperm whale http://en.wikipedia.org/wiki/Tripod_fish - Tripod fish http://www.dickrussell.org/articles/deepblues.htm - Tripod fish http://www.seasky.org/monsters/sea7a1j.html - Umbrellamouth Gulper Eel http://www.seasky.org/monsters/sea7a1k.html - Chambered Nautilus http://thecolouringspot.com/index.html - Colouring Book Byatt, Andrew, Fothergill, Alastair and Holmes, Martha, The Blue Planet: Seas of Life, Chapter 7, DK Publishing Inc., (2001), ISBN 0-7894-8265-7

25. 9.2 OCEAN LIFE 9.2 OCEAN LIFE

26. 9.2 OCEAN LIFE 9.2 OCEAN LIFE 9.2.1 Light In The Sea In the deep ocean, there is little or no light. However, many deep sea organisms are able to generate their own through bioluminescence. The terms bioluminescence, chemiluminescence, fluorescence and phosphorescence are often used loosely to describe the emitting of light. However, the light is produced in different ways, and the terms are not synonymous. CHEMILUMINESCENCE Chemiluminescence is a general term for production of light when the excitation energy has come from a chemical reaction. BIOLUMINESCENCE Bioluminescence is a subset of chemiluminescence, where the light-producing chemical reaction occurs inside an organism. In order to have chemiluminescence or bioluminescence, at least two chemicals are required. The one which produces the light is generically called a “luciferin” and the one that drives or catalyzes the reaction is called a “luciferase”.

27. 9.2 OCEAN LIFE The luciferase catalyzes the oxidation of luciferin, which results in the generation of an inactive "oxyluciferin" compound along with the emission of light. In most cases, fresh luciferin must be brought into the system either through the diet or by internal synthesis. Sometimes the luciferin and catalyzing protein (the equivalent of a luciferase), as well as a co-factor such as oxygen, are bound together to form a single unit called a “photoprotein”. This molecule can be triggered to produce light when a particular type of ion (e.g. calcium) is added to the system. Animals are able to decide exactly when to produce light by controlling when the luciferin and luciferase are mixed together in light-producing cells called “photophores”. In many fish, crustaceans and squid, these light-producing cells are also associated with reflectors, light guides or filters which can concentrate and direct the light. Almost all luciferins produces blue light, which penetrates water well, but some animals can produce yellow, green and, in a few exceptional cases, red light. Most animals in the deep sea can produce their own luciferins but some obtain it from bacteria growing in their light organs (e.g. anglerfish).

28. 9.2 OCEAN LIFE FLUORESCENCE In fluorescence, energy from a source of light is absorbed and re-emitted as another photon. This is in contrast to chemiluminescence or bioluminescence where the excitation energy is supplied by a chemical reaction. The diagram illustrates the fluorescence process: 1. An electron "orbits" a nucleus 2. A source of light of an appropriate wavelength strikes 3. This drives the electron into a higher-energy orbit 4. However, the electron is only stable here for a short time 5. The electron returns to the lower energy level 6. It emits the energy as a longer wavelength photon 7. The electron continues on its way As a result of energy loss in the excited state, the photon emitted will always have a longer wavelength (lower energy) than the exciting photon. Thus, in fluorescence, the energy from an external source of light is absorbed and almost immediately re-emitted. Because energy must be conserved, the wavelength that comes out is longer (redder) and has less energy than what went in.

29. 9.2 OCEAN LIFE PHOSPHORESCENCE Phosphorescence is similar to fluorescence except that the excited product is more stable so that the time until the energy is released is much longer, resulting in a glow after the light has been removed. This is how glow-in-the-dark stickers work. LUMINESCENT LIFE Marine bioluminescence is produced by a wide range of organisms, from bacteria and single-celled protists to fish and squid. However, there are no luminous flowering plants, birds, reptiles, amphibians or mammals. The following are some bioluminescent organisms: • Bacteria • Fungi • Dinoflagellates (single-celled algae) • Radiolarians (single-celled marine organisms) • Cnidarians (corals, siphonophores, jellyfish) • Ctenophores (comb jellies) • Molluscs (nudibranchs, clams, squid, octopus, limpets) • Annelid worms • Pycnogonids (sea spiders) • Crustaceans (copepods, ostracods, amphipods, decapod shrimp, Euphausiids (krill)) • Echinoderms (sea stars, brittle stars, sea cucumbers) • Chordates (some sharks and fish)

30. 9.2 OCEAN LIFE Some examples of bioluminescence are: • “Milky seas” where huge populations of bioluminescent bacteria give the ocean a milky glow. • A siphonophore which uses red light to lure fish to its tentacles. • Crustaceans which send out coded messages to their own species when it is time to mate. REFERENCES & FURTHER READING http://www.lifesci.ucsb.edu/~biolum/ - Bioluminescence

31. 9.2 OCEAN LIFE 9.2.2 Food From Above In the deep ocean, there is very little food. Therefore, as far as the inhabitants are concerned, all food comes from above. MARINE SNOW Nearly all animals on the sea floor rely on “marine snow” for food. Most marine snow is organic material made up of particles of dead plants, dead animals and faecal matter that drops from the surface of the ocean. Much of the marine snow is eaten by mid-water animals which get to it first. However, seabed creatures can wait for it to land on the sea floor as it will go no further. Sea cucumbers are one of the main beneficiaries of marine snow. WHALE FALL Once in a while, a whale or a large animal dies and its body falls to the bottom of the ocean. The carcasses of these dead animals are a boon to the inhabitants of the seabed. In 1998, scientists observed the decomposition of a grey whale carcass. Amphipods (crustaceans) just a few centimeters long were the first to arrive. These animals have sharp jaws for cutting into flesh and they began breaking down the whale’s body.

32. 9.2 OCEAN LIFE These were followed by deep-sea fish, many of which were specialist scavengers. Among them were hagfish. Hagfishes are jawless fish that scavenge on dead or dying fishes and other animals by rasping their way into the body and eating the flesh. They are very flexible and will twist themselves into a knot to gain extra torsion when ripping off pieces of flesh. Hagfishes produce great quantities of slime and have vestigial eyes that are covered by skin and they are usually found in deep cold water. Next to arrive were sleeper sharks, which took massive bites of flesh out of the carcass. Once the first wave had fed, other groups of slower moving scavengers arrived. These included brittle stars, polychaete worms and crabs, which slowly stripped the whale down to its bare bones. The final group to arrive were worms, clams, mussels and, most importantly, chemosynthetic bacteria capable of breaking down the sulphide-rich bones. Some of these are the same species that are found near the hydrothermal vents suggesting such windfalls might serve as a stepping stone for organisms moving from one vent to another. REFERENCES & FURTHER READING Byatt, Andrew, Fothergill, Alastair and Holmes, Martha, The Blue Planet: Seas of Life, Chapter 7, DK Publishing Inc., (2001), ISBN 0-7894-8265-7

33. 9.2 OCEAN LIFE 9.2.3 Hydrothermal Vents About 2,000-3,000 m (6,562-9,842 ft) below the surface of the ocean lie the crests of the mid-ocean ridges. These ridges extend 45,000 km (27,963 miles) along the middle of the world’s oceans. The ridges are 80 km (50 miles) wide in places and can rise up to 3 km (2 miles) off the sea floor. HYDROTHERMAL VENTS The ridges are the site for the production of new sea floor which rises as molten rock from deep within the Earth. Sea water percolates down through cracks and fissures left in the new sea floor as it solidifies. At a depth of just over 1 km (0.6 miles) below the sea floor, the water meets the hot rocks of the oceanic crust and is super-heated before rushing back to the surface and gushing out as a hydrothermal vent. At some vents, the water is as hot as molten lead - 350°C-400°C (662°F-752°F). Normally, water at that temperature would be steam but, under the pressures of the deep ocean, it remains in liquid form.

34. 9.2 OCEAN LIFE The water comes up loaded with minerals from the deep rocks and the colored plumes of water are consequently known as “black smokers” or “white smokers”. The minerals often crystallize as the meet the cold sea water and gradually deposit themselves as chimneys around the vent. These chimneys can grow to enormous heights in one case becoming as tall as a 16 storey building. Entering a field of hydrothermal vents must be similar to visiting industrial hell. Tall black chimneys roar with the sound of escaping super-heated water and the water column is full of highly toxic gases such as methane and hydrogen sulphide. For most animals and plants, it literally is hell and yet, there is life in abundance. NEW LIFE AT DEPTH In 1977, geologists exploring the mid-ocean ridge off the Galapagos Islands in the Pacific Ocean were looking for volcanic activity about 2,000m (6,562 ft) below the surface of the ocean. They found hydrothermal vents but, even more interestingly, they found a rich diversity of life associated with these vents. Since then, hydrothermal vents and life has been found on mid-ocean ridges all over the world.

35. 9.2 OCEAN LIFE • ENERGY & LIFE • Packed around the hydrothermal vents and chimneys are huge tubeworms up to 2 m (6.6 ft) in length and about 6 in (15 cm) in diameter. These are surrounded by a thick carpet of molluscs (e.g. mussels and clams), as well as crustaceans (e.g. crabs), and fish. Life that lives here includes: • Worms – tubeworms, Pompeii worms and other worms • Molluscs – mussels and giant white clams • Crustaceans – shrimps, white crabs • Amphipods • Cnidarians – sea anemones • Fish – about 20 species The tubeworms (Riftia spp.) contain chemosynthetic bacteria which are able to use the energy in hydrogen sulphide to make organic matter in an analogous manner to plants using sunlight. Over half of a tubeworm’s weight is made up of these bacteria, which provide the tubeworm with organic material in exchange for chemicals produced by the tubeworm. The worms have red gills that contain special haemoglobin which fixes sulphides, carbon dioxide and oxygen, and carries them down the length of their bodies to the bacteria.

36. 9.2 OCEAN LIFE Vent mussels and clams were found to have the same chemosynthetic bacteria as the tubeworms. In some areas of the eastern Pacific Ocean, so many molluscs can be found that scientists have given the areas names, such as “Clambake” and “Mussel Bed”. The giant white clams can grow to a length of 30 cm (12 in) and three-quarters of their gill tissue is made up of chemosynthetic bacteria. Although the mussels get much of their energy from these sulphide-fixing bacteria in their gills, they still retain a fully functional mouth and gut to feed off other bacteria that covers the vents. Enormous numbers of non-symbiotic bacteria can also be found around the vents fixing sulphides and providing food for the other animals in the community. Pompeii worms live in white tubes on the edge of the vents close to where the water is emerging. They can survive in temperatures that average 65°C (149°F) with spikes well above 80°C (176°F). Very few other creatures on Earth can survive these conditions without literally being “cooked”.

37. 9.2 OCEAN LIFE ATLANTIC OCEAN HYDROTHERMAL VENTS Hydrothermal vents in the Atlantic Ocean are similar in their formation but support different animal life. Although the communities are just as rich with sulphide fixing bacteria at the bottom of the food chain, they contain no giant tubeworms, mussels and clams. Instead, there are thousands of white shrimps about 5 cm (2 in) in length and belonging to several different species, which completely cover the vent chimneys. These shrimps feed off bacteria growing around the vents. Interestingly, they have a pair of rudimentary eyes on their backs which might seem useless in the pitch darkness. However, further investigation determined that these eyes may actually help the shrimp see the very faintly glowing vents and allow them to find new vents in the darkness. Studying life around the hydrothermal vents may lend insight into how early life on Earth may have begun. Some scientists have suggested that these conditions may be precisely those that existed on Earth when life began. REFERENCES & FURTHER READING Byatt, Andrew, Fothergill, Alastair and Holmes, Martha, The Blue Planet: Seas of Life, Chapter 7, DK Publishing Inc., (2001), ISBN 0-7894-8265-7

38. 9.2 OCEAN LIFE 9.2.4 Cold Seeps In 1984, deep sea biologists were investigating the bottom of the Gulf of Mexico. The rocks at the bottom of the Gulf of Mexico are rich in hydrocarbons (oil and natural gas) such as methane, ethane and propane. At certain places on the sea floor, hydrocarbon gases seep through the sediment and bubble up into the water column. These have come to be called “cold seeps”. One of these cold seeps called the “Brine Pool” looks bizarrely like a calm glassy lake at the bottom of the ocean that laps gently against a golden sandy shore. In fact, the calm glassy water is actually sea water that is saltier and denser than the surrounding sea water and the golden sand is thousands of brown-shelled mussels. Cold seeps such as the Brine Pool are host to a rich community of different animals that are not unlike those found by a hydrothermal vent. The question, however, was how these animals were able to survive in this deep, cold, dark, and toxic environment. ENERGY & LIFE Biologists found that chemosynthetic bacteria living inside mussels were able to fix methane gas (CH4) which is seeping out of the rocks into the water. In turn, these bacteria provide energy at the bottom of a food chain that includes:

39. 9.2 OCEAN LIFE • Molluscs – mussels • Worms – tubeworms and other worms • Crustaceans – crabs • Isopods • Fish • The high pressure and low temperature of the Brine Pool means that the methane gas is actually frozen in some areas into solid “ice”. In these ice blocks, biologists discovered dense aggregations of a new species of polychaete worm that they called “ice worms”. • Scientists have also discovered a large field of a new species of tubeworm near the Brine Pool that stretch for hundreds of meters in some areas. Like their hot-vent counterparts, these animals have no mouth, gut or anus but are full of chemosynthetic bacteria fixing hydrogen sulphide (H2S). Along with methane, hydrogen sulphide gas was seeping through the rocks and the tubeworms seemed able to obtain it. • Cold vent and hydrothermal vent tubeworms are related but the cold vent tubeworms are much thinner and even taller than their hot-vent counterparts. At the top of their tubes, their gills emerge in the shape of rosebuds rather than large red plumes. Like most deep sea inhabitants, cold vent tubeworms grow very slowly and may take 200 years to reach their full size. In contrast, hot vent tubeworms grow much more rapidly reaching full size in just a couple of years and seem to be an exception to the slow growth rule of deep sea animals. • REFERENCES & FURTHER READING • Byatt, Andrew, Fothergill, Alastair and Holmes, Martha, The Blue Planet: Seas of Life, Chapter 7, DK Publishing Inc., (2001), ISBN 0-7894-8265-7

40. 9.3 ACTIVITIES 9.3 ACTIVITIES

41. 9.3 ACTIVITIES 9.3 ACTIVITIES 9.3.1 Journey to the Bottom of the Ocean CORE ACTIVITY (a) Imagine you are traveling between the surface of the ocean and the bottom of the ocean. Draw a poster with the following zones, animals and plants Photic Zone • Phytoplankton • Zooplankton - copepods • Crustaceans – crabs, shrimps and lobsters • Molluscs – mussels and clams • Fish – reef fish, sharks and rays • Mammals – sea otters, pinnipeds Twilight Zone • Zooplankton - copepods • Cnidarians – true jellyfish, siphonophores • Comb jellies • Sea mammals - sperm whale • Molluscs - giant and other squid (e.g. Vitronella), Nautilus

42. 9.3 ACTIVITIES Dark Zone • Cnidarians – true jellyfish (e.g. Periphylla, Atolla) • Crustaceans – red deep sea shrimp • Molluscs – squid (e.g. Vampyroteuthis infernalis) • Fish – anglerfish, gulper eel, dragonfish Abyss Zone & Trenches (Deep Sea Floor) • Foraminiferans • Tubeworms • Sponges – deep sea sponges • Cnidarians – deep sea corals, sea anemones, sea pens • Nematodes (round worms) • Isopods • Polychaete worms • Cnidarians – deep sea anemones • Echinoderms – sea cucumbers, brittle stars, sea urchins • Fish – tripod fish, rattail, sleeper sharks, six-gill sharks

43. 9.3 ACTIVITIES 9.3.2 Deep Ocean Life CORE ACTIVITY (a) What life is found in the Twilight Zone? (b) What are some of the adaptations animals in Twilight Zone possess? (c) What life lives in the Dark Zone? (d) What are some of the adaptations animals in Dark Zone possess? (e) What life lives on the Deep Sea Floor? (Extended Activity)

44. 9.3 ACTIVITIES ANSWERS (a) What life is found in the Twilight Zone? • Cnidarians – e.g. true jellyfish and siphonophores • Comb jellies • Sea mammals – e.g. sperm whale • Molluscs – e.g. giant and other squid, nautilus (b) What are some of the adaptations animals in Twilight Zone possess? • Transparent • Reflective • Excellent eyesight • Tools for killing prey quickly (c) What life lives in the Dark Zone? • Cnidarians – true jellyfish (e.g. Periphylla, Atolla) • Crustaceans – red deep sea shrimp • Molluscs – squid (e.g. Vampyroteuthis infernalis) • Fish – anglerfish, gulper eel, dragonfish

45. 9.3 ACTIVITIES (d) What are some of the adaptations animals in Dark Zone possess? • Black or dark red colour • Poor vision • Sensitive to vibrations • Bioluminescent (e) What life lives on the Deep Sea Floor? (Extended Activity) • Foraminiferans • Tubeworms • Sponges – deep sea sponges • Cnidarians – deep sea corals, sea anemones, sea pens • Nematodes (round worms) • Isopods • Polychaete worms • Cnidarians – deep sea anemones • Echinoderms – sea cucumbers, brittle stars, sea urchins • Fish – tripod fish, rattail, sleeper sharks, six-gill sharks

46. 9.3 ACTIVITIES 9.3.3 Light in the Sea CORE ACTIVITY (a) What is bioluminescence? (b) Name some types of bioluminescent organisms

47. 9.3 ACTIVITIES ANSWERS (a) What is bioluminescence? Chemiluminescence is a general term for production of light when the excitation energy has come from a chemical reaction. Bioluminescence is a subset of chemiluminescence, where the light-producing chemical reaction occurs inside an organism.

48. 9.3 ACTIVITIES (b) Name some types of bioluminescent organisms The following are some bioluminescent organisms: • Bacteria • Fungi • Dinoflagellates (single-celled algae) • Radiolarians (single-celled marine organisms) • Cnidarians (corals, siphonophores, jellyfish) • Ctenophores (comb jellies) • Molluscs (nudibranchs, clams, squid, octopus, limpets) • Annelid worms • Pycnogonids (sea spiders) • Crustaceans (copepods, ostracods, amphipods, decapod shrimp, Euphausiids (krill)) • Echinoderms (sea stars, brittle stars, sea cucumbers) • Chordates (some sharks and fish) Some examples of bioluminescence are: • “Milky seas” where huge populations of bioluminescent bacteria give the ocean a milky glow. • A siphonophore which uses red light to lure fish to its tentacles. • Crustaceans which send out coded messages to their own species when it is time to mate.