The Deep

1. The Deep Chapters 3, 18, 19

2. World Ocean • Primitive earth and formation of the ocean • early earth thought to be composed of silicon compounds, iron, magnesium oxide, and other elements • gradually, the earth heated, causing melting and separation of elements • water vapor locked within minerals released to the surface, where it cooled, condensed, and formed the ocean

3. World Ocean • Ocean and the origin of life • atmosphere formed by gases escaping from the planet • no accumulation of oxygen until evolution of photosynthesis—free oxygen forms oxides • Stanley Miller’s apparatus

4. World Ocean • The ocean today • 4 major ocean basins: Pacific, Atlantic, Indian and Arctic • seas and gulfs

5. Continental Drift • Layers of the earth • solid inner core—iron- and nickel-rich • liquid outer core (same composition) • mantle—thickest layer with greatest mass, mainly magnesium-iron silicates • crust—thinnest and coolest, outermost

6. Continental Drift • Moving continents • Alfred Wegener • Pangaea, Laurasia and Gondwanaland

7. Continental Drift • Forces that drive continental movement • magma convection currents • midocean ridges form along cracks where magma breaks through the crust • at subduction zones, old crust sinks into the mantle where it is recycled • seafloor spreading causes continental drift

8. Continental Drift • Evidence for continental drift • fit of continental boundaries • earthquakes • seafloor temperatures highest near ridges • age of crust, as determined by samples drilled from the ocean bottom, increases with distance from a ridge

9. Continental Drift • Theory of plate tectonics • lithosphere is viewed as a series of rigid plates separated by earthquake belts • divergent plate boundaries—midocean ridges where plates move apart • convergent plate boundaries—trenches where plates move toward each other • faults—regions where plates move past each other (e.g. transform faults) • rift zones—where lithosphere splits

10. Continental Drift • Rift communities • depend on specialized environments found at divergence zones of the ocean floor • first was discovered by Robert Ballard and J.F. Grassle in 1977, in the Galápagos Rift • primary producers are chemosynthetic bacteria

11. Ocean Bottom • Continental margins • continental shelf, continental slope, and shelf break • submarine canyons and turbidity currents • continental rises • shaping the continental shelves • glaciers • sediments

12. Ocean Bottom • Ocean basin • abyssal plains and hills • seamounts • ridges and rises • trenches and island arcs • Life on the ocean floor • continental shelves are highly productive • life on the abyssal plains is not abundant owing to the absence of sunlight

13. Composition of the Seafloor • Sediment—loose particles of inorganic and organic material

14. Composition of the Seafloor • Hydrogenous sediments • formed from seawater through a variety of chemical processes • e.g. carbonates, phosphorites • Biogenous sediments • formed from living organisms • mostly particles of corals, mollusc shells, shells of planktonic organisms

15. Composition of the Seafloor • Terrigenous sediments • produced from continental rocks by the actions of wind, water, freezing, thawing • e.g. mud (clay + silt) • Cosmogenous sediments • formed from iron-rich particles from outer space which land in the ocean and sink to the bottom

16. Salt and Water • 30% of the salt supply comes from the sea; 70% from deposits left when ancient seas evaporated • Extraction of salt from seawater • seawater is directed into shallow ponds where it is concentrated, then evaporated • in cold regions, ice (which is nearly pure water) is removed, leaving concentrated seawater which is heated to evaporate the remaining pure water

17. Salt and Water • Desalination—process of removing salts from seawater (so it is potable) • process is energetically/financially expensive • usually more expensive than obtaining water from groundwater or surface sources • used in Israel, Saudi Arabia, Morocco, Malta, Kuwait, Caribbean islands, parts of Texas and California

18. Mineral Resources • Sulfides • formed when mineral-rich solutions from fractures in rift valleys come into contact with colder seawater, and precipitate • no technology exists for sampling/mining • Manganese • used as a component of several alloys • nodules are found on the ocean floor • attempts to develop mining technology were largely suspended in the 1980s

19. Sand and Gravel • Most widespread seafloor mining operations extract sand and gravel for use in cement, concrete and artificial beaches • Calcium carbonate deposits • lime, cement, calcium oxide for removing magnesium from seawater, gravel • Tin is extracted from sand in coastal regions of Southeast Asia

20. Sand and Gravel • Uranium extracted from bottom sediments of the Black Sea • Platinum extracted from coastal sands in the U.S., Australia, South Africa • Mining sands/gravel can cause pollution and habitat destruction in the marine environment

21. Energy Sources: Coal, Oil, Natural Gas, and Methane Hydrate • Coal • formed from prehistoric swamp plants • coal is mined from under the sea in Japan • Oil and natural gas • represent 90% of the mineral value taken from the sea • formed from remains of diatoms and other microorganisms • oil is mined in the Persian Gulf, North Sea, Gulf of Mexico, northern coast of Australia, southern coast of California, and around the Arctic ocean

22. Energy Sources: Coal, Oil, Natural Gas, and Methane Hydrate • Methane hydrate • methane hydrate—ice crystals that trap methane, and can be burned • world’s largest known fuel reserve • methane gas rapidly escapes from the crystals when they are brought to the surface • experiments indicate it may be possible to exploit this resource, but geologists and biologists have concerns

23. Finding Your Way around the Sea • Maps and charts • Mercator projections • bathymetric charts • physiographic charts

24. Finding Your Way around the Sea • Reference lines • latitude • longitude • divisions of latitude and longitude

25. Finding Your Way around the Sea • Navigating the ocean • principles of navigation • a sextant was used to determine latitude based on the angle of the North Star with reference to the horizon • longitude determined using chronometer

26. Finding Your Way around the Sea • Navigating the ocean • global positioning system (GPS) • utilizes a system of satellites to determine position • GPS measures the time needed to receive a signal from 3 satellites, and calculates position

27. Survival in the Deep Sea • The deep sea is an inhospitable place • frigid temperatures throughout the year • tremendous pressure • total darkness • Conditions have remained stable over many years • Some creatures have evolved to survive in this harsh environment

28. Survival in the Deep Sea • Adaptations to pressure • fluid pressure within the animal’s tissues matches the pressure of the seawater • Adaptations to cold • nearly all have body temperatures close to that of the surrounding water • slow metabolism – slow movement, growth; less reproduction, longer life • high density of cold water matches that of animal’s bodies – they don’t sink

29. 0 Environmental Factors Affect Organism Distribution • pressure • 760 mm Hg or 1 atmosphere at sea level • increases 1 atmosphere for every 10 meters below sea level

30. Life in the Dark • Color in deep-sea organisms • countershading employed in the disphotic zone—region of dim light (twilight) • photophores (light-producing organs) may be used to make the ventral surface lighter • many species are bright red or orange • appear black or gray in dim light • many are bioluminescent

31. Life in the Dark • Roles of bioluminescence • how bioluminescence works • a protein called luciferin is combined with oxygen in the presence of an enzyme called luciferase and adenosine triphosphate (ATP) • chemical energy of ATP converted to light • camouflage • bioluminescence matches the intensity of sunlight, and thus contributes to countershading, in the twilight zone

32. Life in the Dark • Roles of bioluminescence (continued) • mating and species recognition • identifies the sex of an individual • allows for identification of species • attracting prey • anglerfish and stomiatoids attract prey with bioluminescent lures • light may be used to locate prey in the dark • defense • deepwater squid and shrimp release clouds of bioluminescent materials to confuse predators

33. Life in the Dark • Seeing in the dark • many deep-sea fishes have tubular eyes containing 2 retinas instead of 1 • 1 retina views distant objects, while the other views closer objects

34. Life in the Dark • Seeing in the dark • deep-sea squid have barrel-shaped, stalked or unequally-sized eyes • some animals have slightly-functional eyes or are totally blind, relying on chemical stimuli instead

35. Life in the Dark • Finding mates in the dark • male becomes a parasite on the female in some species of anglerfish • Finding food in the dark • benthic organisms and scavengers eat detritus which drifts down from above • many small fishes and invertebrates migrate upward at night to feed • adaptations include large mouths and expandable stomachs

36. Life in the Dark • Finding food in the dark (continued) • some can eat prey larger than themselves • stomiatoids have barbels (fleshy projections) that may be used as lures, probes or for species recognition • anglerfishes have a spine used as a fishing pole, tipped with a luminous lure

37. Giants of the Deep • Giant squids • New species of deepwater squid • large, unnamed species discovered 1988 • have longer arms than other squid, bent downward at sharp angles • exhibit different behaviors • hide in their ink clouds instead of fleeing • pairs have been observed attached, towing each other through the water

38. Relicts from the Deep • Spirula • small molluscs resembling squid and octopuses with spiral-shaped internal shells • similar to belemnites common in the sea 100-50 million years ago • Vampire squid • dark-colored, webbing between its arms • thought to be descendents of an intermediate organism between squids and octopuses

39. Relicts from the Deep • Coelacanth • fish with large, thick scales and fleshy bundles between its body and fins • thought to be extinct for 70 million years until 1 was caught alive in 1938 • Neopilina • limpet-like mollusc • thought to be extinct for 350 million years until 1 was found in 1952

40. Life on the Sea Bottom • Benthic communities • sources of food for benthic organisms • organic matter rains down from surface waters and accumulates on the ocean floor • a large carcass will occasionally drift down • food chains • bacteria are consumed by meiofauna (e.g. foraminiferans and nematodes) • infauna (e.g. worms, bivalves) eat meiofauna • deposit feeders and suspension feeders • predators include fishes, squids, sea stars

41. Life on the Sea Bottom • Benthic communities (communities) • diversity of benthic organisms of the deep • low numbers, but high diversity • ineffective dispersion of young may lead to isolation, which contributes to speciation • stable conditions may prevent extinction of species, so species proliferate

42. Life on the Sea Bottom • Vent communities • self-contained communities that are some of the most productive in the sea • formation of vents • vents form at spreading centers • seawater seeps down to where it contacts magma • water is superheated, and loses some minerals while it picks up others, such as sulfur, iron, copper and zinc

43. Life on the Sea Bottom • Vent communities (continued) • types of vents • white smokers—produce a stream of milky fluid rich in zinc sulfide; water temperature is normally less than 300o C • black smokers—narrow chimneys that emit a clear water with temperatures of 300o to 450o C that is rich in copper sulfides (which precipitate with contact with cold seawater, to produce the black color)

44. Life on the Sea Bottom • Vent communities (continued) • vent communities • residents include large clams, mussels, anemones, barnacles, limpets, crabs, worms and fishes • primary producers are chemosynthetic bacteria • primary consumers filter-feed or graze bacteria from the water • clams (Calyptogena), mussels (Bathymodiolus) and vestimentiferan worms (Riftia) host symbiotic chemosynthetic bacteria

45. Life on the Sea Bottom • Vent communities (continued) • rise and fall of vent communities • vents are colonized by organisms shortly after they are formed • when geological changes inactivate the vent (an estimated 20 years later), these organisms all die • vent inhabitants are thought to produce large numbers of larvae which drift to other vent sites