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  1. The marine environment Major marine ecosystems Human uses of marine resources Human impacts on the marine environment The state of ocean fisheries Marine protected areas and reserves This lecture will help you understand:

  2. Central Case: collapse of the cod fisheries • No fish has more impact on human civilization than the Atlantic cod • Eastern Canadians and U.S. fishermen have fished for cod for centuries • Large ships and technology have destroyed the cod fishery • Even protected stocks are not recovering • Prey may now be competing with, and eating, young cod

  3. Cod are groundfish • They live or feed along the bottom • Halibut, pollock, flounder • Cod eat small fish and invertebrates • They grow to 60-70 cm long and can live 20 years • Inhabit cool waters on both sides of the Atlantic • There are 24 stocks (populations) of cod

  4. Oceans cover most of the Earth’s surface • The oceans influence global climate, team with biodiversity, facilitate transportation and commerce, and provide resources for us • They cover 71% of Earth’s surface and contain 97% of Earth’s surface water • Oceans influence the atmosphere, lithosphere, and biosphere

  5. The oceans contain more than water • Ocean water is 96.5% water • Plus, ions of dissolved salts • Evaporation removes pure water and leaves a higher concentration of salt • Nutrients (nitrogen and phosphorus) • Dissolved gas • Oxygen is added by plants, bacteria, and atmospheric diffusion

  6. Ocean water is vertically structured • Temperature declines with depth • Heavier (colder saltier) water sinks • Light (warmer and less salty) water remains near the surface • Temperatures are more stable than land temperatures • Water’s high heat capacity • It takes much more heat to warm water than air • Oceans regulate the earth’s climate • They absorb and release heat • Ocean’s surface circulation

  7. The ocean has several layers • Surface zone • Warmed by sunlight and stirred by wind • Consistent water density • Pycnocline = below the surface zone • Density increases rapidly with depth • Deep Zone = below the pycnocline • Dense, sluggish water • Unaffected by winds, storms, sunlight, and temperature

  8. Ocean water flows horizontally in currents • Currents = the ocean is composed of vast riverlike flows • Driven by density differences, heating and cooling, gravity, and wind • Influence global climate and El Niño and La Niña • Transport heat, nutrients, pollution, and the larvae of many marine species • Some currents such as the Gulf Stream are rapid and powerful • The warm water moderates Europe’s climate

  9. The upper waters of the oceans flow in currents

  10. Surface winds and heating create vertical currents • Upwelling = the vertical flow of cold, deep water towards the surface • High primary productivity and lucrative fisheries • Also occurs where strong winds blow away from, or parallel to, coastlines • Downwellings = oxygen-rich water sinks where surface currents come together

  11. Seafloor topography can be rugged and complex • The seafloor consists of… • Underwater volcanoes • Steep canyons • Mountain range • The planet’s longest range is under water • Mounds of debris • Trenches • Some flat areas

  12. Understanding underwater geography • Maps show… • Bathymetry = themeasurement of ocean depths • Topography = the physical geography or the shape and arrangement of landforms • Continental shelves = gently sloping areas that underlie the shallow waters bordering continents • Shelf-slope break = sudden drop off of the continental shelf • Continental slope = connects the continental shelf to the ocean floor

  13. A stylized bathymetric profile of the ocean

  14. Regions of ocean differ greatly • Some zones support more life than others • Photic zone = well-lighted top layer that supports high primary productivity • Pelagic = habitats and ecosystems occurring between the ocean’s surface and floor • Benthic = habitats and ecosystems occurring on the ocean floor

  15. Open ocean systems vary in biodiversity • Microscopic phytoplankton constitute the base of the marine food chain in the pelagic zone • Algae, protists, and cyanobacteria • These organisms feed zooplankton • Which then feeds fish, jellyfish, whales, etc. • Predators at higher trophic levels include larger fish, sea turtles, sharks, and fish-eating birds

  16. Animals of the deep ocean • Animals adapt to extreme water pressure and the absence of light • Scavenge carcasses or organic detritus • Some are predators, while others have mutualistic relationships with bacteria • Some species carry bacteria that produce light chemically by bioluminescence • Hydrothermal vents support tubeworms, shrimp, and other chemosynthetic species

  17. Kelp forests harbor many organisms • Kelp = large, dense, brown algae growing from the floor of continental shelves • Dense strands form kelp forests along temperate coasts • Shelter and food for organisms • Absorbs wave energy and protects shorelines from erosion • Eaten by people • Alginates serve as thickeners in cosmetics, paints, paper, and soaps

  18. Coral reefs are treasure troves of biodiversity • Located in shallow subtropical and tropical waters • Corals = tiny colonial marine organisms • Related to sea anemones and jellyfish • Remain attached to rock or existing reef and capture passing food with stinging tentacles • Derive nourishment from symbiotic algae, zooxanthallae

  19. Coral reefs consist of millions of corals • Coral reef = a mass of calcium carbonate composed of the skeletons of corals • Consists of millions of densely packed individuals • Protect shorelines by absorbing waves • Innumerable invertebrates and fish species find food and shelter in reef nooks and crannies

  20. Coral reefs are in worldwide decline • Coral bleaching = occurs when zooxanthellae leave the coral • Coral lose their color and die, leaving white patches • From climate change, pollution, or unknown natural causes • Nutrient pollution causes algal growth, which covers coral • Divers damage reefs by using cyanide to capture fish • Acidification of oceans deprives corals of necessary carbonate ions for their structural parts

  21. Deepwater coral reefs exist • They thrive in waters outside the tropics • On ocean floor at depths of 200-500 m (650-1650 ft) • Occur in cold-water areas • Little is known about these reefs • Already, many have been badly damaged by trawling • Some reefs are now being protected

  22. Intertidal zones undergo constant change • Intertidal (littoral) ecosystems = where the ocean meets the land • between the uppermost reach of the high tide and the lowest limit of the low tide • Tides = periodic rising and falling of the ocean’s height due to the gravitational pull of the sun and moon • Intertidal organisms spend part of their time submerged in water and part of their time exposed to sun and wind

  23. A typical intertidal zone

  24. Intertidal zones are a tough place to live • But they have remarkable diversity • Rocky shorelines, crevices, pools of water (tide pools) • Anemones, mussels, barnacles, urchins, sea slugs, starfish, and crabs • Temperature, salinity, and moisture change dramatically from high to low tide • Sandy intertidal zones have slightly less biodiversity

  25. Salt marshes occur widely • Salt marsh = occur along coasts at temperate latitude • Tides wash over gently sloping, sandy, silty substrates • High primary productivity • Critical habitat for birds and commercial fish and shellfish species • Filter pollution • Stabilize shorelines against storm surges

  26. People have changed and destroyed salt marshes • People have altered or destroyed salt marshes for development • We lose key ecosystem service • Flooding worsens

  27. Mangrove forests line coasts • In tropical and subtropical latitudes • Replace salt marshes along sandy coasts • Mangroves = trees with unique roots • Curve upwards for oxygen • Curve downwards for support • Nurseries for commercial fish and shellfish • Nesting areas for birds • Food, medicine, tools, construction materials

  28. Mangrove forests have been destroyed • Development for residential, commercial, and recreational uses • Shrimp farming • Half the world’s mangrove forests are gone • Once destroyed, coastal areas no longer • Slow runoff • Filter pollutants • Retain soil • Protect communities against storm surges • We are protecting only 1% of remaining mangroves

  29. Estuaries: where fresh and salt water meet • Estuaries = water bodies where rivers flow into the ocean • Wide fluctuations in salinity • Critical habitat for shorebirds and shellfish • Transitional zone for anadromous (spawn in freshwater, mature in salt water) fishes • Affected by development, pollution, habitat alteration, and overfishing

  30. Oceans provide transportation routes • Humans have interacted with oceans for thousands of years • Moving people and products over vast distances • Accelerated global reach of cultures • Has substantial impact on the environment • Moves resources around the world • Ballast water transplants organisms, which may become invasive

  31. We extract energy from oceans • Crude oil and natural gas • Oil spills damage fisheries • Methane hydrate = a potential energy source • Ice-like solid methane embedded in water crystals • A vast supply, but research needs to be done • Renewable energy sources, such as waves, tides, heat

  32. We extract minerals from oceans • Minerals such as sand, gravel, sulfur, calcium carbonate, and silica • Rich deposits of copper, zinc, silver, and gold • Manganese nodules are scattered along the ocean’s floor • But, they are too hard to currently mine

  33. Marine pollution threatens resources • Even into the mid-20th century, coastal U.S. cities dumped trash and untreated sewage along their shores • Oil, plastic, chemicals, excess nutrients make their way from land into oceans • Raw sewage and trash from cruise ships • Abandoned fishing gear from fishing boats In 2006, 359,000 Ocean Conservancy volunteers from 66 nations picked up 3.2 million kg (7 million lbs.) of trash

  34. Nets and plastic debris endangers marine life • Plastic items dumped into the sea harm or kill wildlife • Plastic is non-biodegradable • Drifts for decades • Washes up on beaches • Wildlife eat it or get entangled and die • Marine debris affects people • Equipment damage • The 2006 Marine Debris Research, Prevention and Reduction Act

  35. Oil pollution comes from spills of all sizes • Major oils spills (i.e., the Exxon Valdez) make headlines and cause serious environmental problems • Most pollution comes from small sources • Boat leakage and runoff from land • Naturally occurring leaks from the seabed • Oil spills coat and poison wildlife

  36. Oil pollution has decreased • Governments have implemented more stringent regulations • The U.S. Oil Pollution Act of 1990 • Creates a $1 billion prevention and cleanup fund • Requires all ships have double hulls by 2015 • Recently, oil spills have decreased • The oil industry resists such safeguards

  37. Toxic pollutants contaminate seafood • Mercury contamination • From coal combustion and other sources • Bioaccumulates and biomagnifies • Dangerous to young children and pregnant or nursing mothers • Avoid eating swordfish, shark, and albacore tuna • Eat seafood low in mercury (catfish, salmon, canned light tuna) • Avoid seafood from areas where health advisories have been issued

  38. Excess nutrients cause algal blooms • Harmful algal blooms = nutrients increase populations of algae that produce powerful toxins • Red tide = algal species produce reddish pigments that discolor water • Illness and death to wildlife and humans • Economic losses to fishing industries and beach tourism • Reduce runoff and prevent consumption of affected organisms

  39. Emptying the oceans • We are placing unprecedented pressure on marine resources • Half the world’s marine fish populations are fully exploited • 25% of fish population are overexploited and heading to extinction • Total fisheries catch leveled off after 1998, despite increased fishing effort • It is predicted that populations of all ocean species we fish for today will collapse by the year 2048

  40. The total global fisheries catch has increased

  41. We have long overfished • People began depleting sea life centuries ago • Some species hunted to extinction: Steller’s sea cow, Atlantic gray whale, Caribbean monk seal • Overharvesting of Chesapeake Bay oyster beds led to the collapse of its fishery, eutrophication, and hypoxia • Decreased sea turtle populations causes overgrowth of sea grass and can cause sea grass wasting disease • People never imagined that groundfish could be depleted • New approaches or technologies increased catch rates

  42. Fishing has industrialized • Factory fishing = highly industrialized, huge vessels use powerful technologies to capture fish in huge volumes • Even process and freeze their catches while at sea • Driftnets for schools of herring, sardines, mackerel, sharks • Longline fishing for tuna and swordfish • Trawling for pelagic fish and groundfish

  43. Fishing practices kill nontarget animals • By-catch = the accidental capture of animals • Driftnetting drowns dolphins, turtles, and seals • Fish die from air exposure on deck • Banned or restricted by many nations • Longline fishing kills turtles, sharks, and albatrosses • 300,000 seabirds die each year • Bottom-trawling destroys communities • Likened to clear-cutting and strip mining

  44. Modern fishing fleets deplete marine life rapidly • Grand Banks cod have been fished for centuries • Catches more than doubled with immense industrial trawlers • Record-high catches lasted only 10 years

  45. Industrialized fishing depletes populations • Catch rates drop precipitously with industrialized fishing • 90% of large-bodied fish and sharks are eliminated within 10 years • Populations stabilize at 10% of their former levels • Marine communities may have been very different before industrial fishing • Removing animals at higher trophic levels allows prey to proliferate and change communities

  46. Oceans today contain only one-tenth of the large-bodied animals they once did

  47. Several factors mask declines • Industrialized fishing has depleted stocks, global catch has remained stable for the past 20 years • Fishing fleets travel longer distances to reach less-fished portions of the ocean • Fleets spend more time fishing and have been setting out more nets and lines, increasing effort to catch the same number of fish • Improved technologies: faster ships, sonar mapping, satellite navigation, thermal sensing, aerial spotting • Data supplied to international monitoring agencies may be false

  48. We are “fishing down the food chain” • Figures on total global catch do not relate the species, age, and size of fish harvested • As fishing increases, the size and age of fish caught decline • 10-year-old cod, once common, are now rare • As species become too rare to fish, fleets target other species • Shifting from large, desirable species to smaller, less desirable ones • Entails catching species at lower trophic levels

  49. Consumer choices influence fishing practices • Buy ecolabeled seafood • Dolphin-safe tuna • Consumers don’t know how their seafood was caught • Nonprofit organizations have devised guides for consumers • Best choices: farmed catfish and caviar, sardines, Canadian snow crab • Avoid: Atlantic cod, wild-caught caviar, sharks, farmed salmon