1. Environment: The Science behind the Stories
Lecture Outlines
Chapter 16
Environment: The Science behind the Stories
4th Edition
Withgott/Brennan

2. This lecture will help you understand:
The marine environment
Ocean-climate relationships
Marine ecosystems
Marine pollution
The state of ocean fisheries
Marine protected areas and reserves

3. Central Case: Collapse of the cod fisheries
No fish has had more impact on civilization than the Atlantic cod
Cod have been fished for centuries
Large ships and technology have destroyed the cod fishery
Even protected stocks are not recovering
Young cod are being preyed on
But other species are recovering in protected areas

4. Cod are groundfish Fish that live or feed along the bottom
Halibut, pollack, flounder
Cod eat small fish and invertebrates
They inhabit cool waters on both sides of the Atlantic
The 24 stocks (populations) of cod crashed
Overfishing and destroyed habitat
The U.S. and Canada have paid billions to retrain fishermen who lost their jobs

5. Oceans cover most of the Earth’s surface
Oceans influence climate, team with biodiversity, provide resources, and help transportation and commerce
Oceans cover 71% of Earth’s surface and contain 97.5% of its water
Oceans influence the atmosphere, lithosphere, and biosphere

6. Seafloor topography can be rugged
The seafloor consists of:
Underwater volcanoes
Steep canyons
Mountain ranges
Mounds of debris
Trenches
Some flat areas
Some island chains are formed by reefs or volcanoes
Topographically complex areas serve as habitat and productive fishing grounds

7. A stylized bathymetric profile of the ocean
A stylized map reflects the ocean’s bathymetry (depths) and topography (landforms)

8. Ocean water contains salt
Ocean water is 96.5% water
Plus, ions of dissolved salts
Evaporation removes pure water
Leaving salt behind
Low levels of nutrients (nitrogen and phosphorus)
Oxygen is added by plants, bacteria, and atmospheric diffusion

9. Ocean water is vertically structured
Temperature declines with depth
Heavier (colder, saltier) water sinks
Light (warmer, less salty) water stays near the surface
Temperatures are more stable than land temperatures
Water has high heat capacity (heat required to increase temperature by a given amount)
It takes more energy to warm water than air
Oceans regulate Earth’s climate
They absorb and release heat
The ocean’s surface circulation moves heat around

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

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

12. Currents form patterns across the globe

13. Vertical movement affects ecosystems
Upwelling = the upward flow of cold, deep water toward 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

14. Currents affect climate
Horizontal and vertical movement of oceans affects global and regional climates
Thermohaline circulation = a worldwide current system
Warmer, fresher water moves along the surface
Cooler, saltier, denser water moves beneath the surface
North Atlantic Deep Water (NADW) = one part of the thermohaline conveyor belt
Water in the Gulf Stream flows to Europe
Released heat keeps Europe warmer that it would be
Sinking cooler water creates a region of downwelling

15. The North Atlantic Deep Water
Interrupting the thermohaline circulation could trigger rapid climate change
Melting ice from Greenland will run into the North Atlantic
Making surface waters even less dense
Stopping NADW formation and shutting down the northward flow of warm water
Europe would rapidly cool
This circulation is already slowing
But Greenland may not have enough runoff to stop it

16. El Niño–Southern Oscillation (ENSO)
ENSO = a systematic shift in atmospheric pressure, sea surface temperature, and ocean circulation
In the tropical Pacific Ocean
Normal winds blow east to west, from high to low pressure
This forms a large convective loop in the atmosphere
Winds push water west, causing it to “pile up”
Nutrient-rich, cold water along Peru and Ecuador rises from the deep
Decreased pressure in the eastern Pacific triggers El Niño
Warm water flows eastward, suppressing upwellings

17. Effects of El Niño and La Niña
Coastal industries (e.g., Peru’s anchovy fisheries) are devastated
Worldwide, fishermen lost $8 billion in 1982–1983
Global weather patterns change
Rainstorms, floods, drought, fires
La Niña = the opposite of El Niño
Cold waters rise to the surface and extend westward
ENSO cycles are periodic but irregular (every 2–8 years)
Globally warming sea and air may be increasing the strength and frequency of these cycles

18. ENSO, El Niño, and La Niña
Normal conditions
El Niño conditions

19. Climate change is altering the oceans
Global climate change will affect ocean chemistry and biology
Burning fossil fuels and removing vegetation increase CO2, which warms the planet
Oceans absorb carbon dioxide (CO2) from the air
But oceans may not be able to absorb much more CO2
Increased CO2 in the ocean makes it more acidic
Ocean acidification makes chemicals less available for sea creatures (e.g., corals) to form shells
Fewer coral reefs decrease biodiversity and ecosystem services

20. Marine and coastal ecosystems
Regions of ocean water differ greatly
Some zones support more life than others
Photic zone = well-lighted top layer
Absorbs 80% of solar energy
Supports high primary productivity
Pelagic = habitats and ecosystems between the ocean’s surface and floor
Benthic = habitats and ecosystems on the ocean floor
Most ecosystems are powered by solar energy
But even the darkest depths host life

21. Open ocean systems vary in biodiversity
Microscopic phytoplankton are the base of the marine food chain
Algae, protists, cyanobacteria
They feed zooplankton
Which then feed fish, jellyfish, whales, etc.
Predators at higher trophic levels
Larger fish, sea turtles, sharks, and fish-eating birds

22. Animals of the deep ocean
Animals adapt to extreme water pressure and the dark
Scavenge carcasses or organic detritus
Predators
Others have mutualistic relationships with bacteria
Some carry bacteria that produce light chemically by bioluminescence
Hydrothermal vents support tubeworms, shrimp, and other chemosynthetic species

23. 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
They provide shelter and food for organisms
They absorb wave energy and protect shorelines from erosion
People use it in food, cosmetics, paints, paper, soap, etc.

24. Coral reefs are treasure troves of biodiversity
Coral reef = a mass of calcium carbonate composed of the skeletons of tiny marine animals (corals)
They may be an extension of a shoreline
Or exist along a barrier island, parallel to the shore
Or as an atoll (a ring around a submerged island)
Corals = tiny colonial invertebrate animals
Related to sea anemones and jellyfish
Attach to a rock or reef and capture passing food with stinging tentacles
Get food from symbiotic algae (zooxanthallae)

25. Most corals are colonial
Reefs consist of millions of densely packed animals
Reefs are located in shallow subtropical and tropical waters
Protect shorelines by absorbing waves
Innumerable invertebrates and fish species find food and shelter in reef nooks and crannies

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

27. Deepwater coral reefs exist
They thrive in waters outside the tropics
On ocean floor at depths of 200–500 m (650–1,650 ft)
Occur in cold-water areas off the coasts of Spain, the British Isles, and elsewhere
Little is known about these reefs
Already, many have been badly damaged by trawling
Some reefs are now being protected

28. 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

29. A typical intertidal zone

30. Intertidal zones are a tough place to live
But they have amazing 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

31. Salt marshes line temperate shorelines
Salt marshes = occur along coasts at temperate latitudes
Tides wash over gently sloping sandy, silty substrates
Tidal creeks = channels that rising and falling tides flow into and out of
Salt marshes have very high primary productivity
Critical habitat for birds, commercial fish, and shellfish
They filter pollution
They stabilize shorelines against storm surges a 31

32. People change and destroy salt marshes
People want to live or do business along coasts
We lose key ecosystem services
Flooding (e.g., from Hurricane Katrina) worsens

33. Mangrove forests line coasts
In tropical and subtropical latitudes
They replace salt marshes along sandy coasts
Mangroves = salt-tolerant trees
Their unique roots curve up for oxygen and down for support
Nesting areas for birds
Nurseries for fish and shellfish
Mangroves provide food, medicine, tools, and construction materials

34. Mangrove forests have been destroyed
Half the world’s mangrove forests are gone
Developed for residential, commercial, and recreational uses
Shrimp farming
Once destroyed, coastal areas no longer:
Slow runoff
Filter pollutants
Retain soil
Protect communities against storm surges

35. Fresh and salt water meet in estuaries
Estuaries = water bodies where rivers flow into the ocean, mixing fresh and salt water
They are biologically productive
Have fluctuations in salinity
Critical habitat for shorebirds and shellfish
Transitional zone for fish that spawn in streams and mature in salt water
They have been affected by development, pollution, habitat alteration, and overfishing

36. Marine pollution People use oceans as a sink for waste and pollutants
Even into the mid-20th century, coastal U.S. cities dumped trash and untreated sewage along their shores
Nonpoint source pollution comes from all over
Oil, plastic, chemicals, excess nutrients
In 2008, 391,000 Ocean Conservancy volunteers from 104 nations picked up 3.1 million kg (6.8 million lb) of trash from 27,000 km (17,000 miles) of shoreline

37. Nets and plastic debris endanger life
Plastic items dumped into the sea harm or kill wildlife
Wildlife mistake it for food
98% of dead northern fulmars had plastic in their stomachs
Plastic is nonbiodegradable
Drifts for decades
Breaks into tiny pieces
Trillions of tiny plastic pellets float in the oceans and are eaten

38. Plastic trash is accumulating in the oceans
Circulating currents bring and trap plastic trash to areas
The northern Pacific Gyre stretches from California to Hawaii to Japan
This “Great Pacific Garbage Patch” is the size of Texas and has 3.3 plastic bits/m2
The 2006 Marine Debris Research, Prevention, and Reduction Act is not enough
We must reduce, reuse, and recycle more plastic
Participate in efforts such as the International Coastal Cleanup

39. Oil pollution comes from spills of all sizes
30% of oil and 50% of natural gas come from seafloor deposits
North Sea, Gulf of Mexico
Drilling in other places is banned
Spills could harm valuable fisheries
The Deepwater Horizon exploded off Louisiana’s coast in April 2010
Spilling 140 gallons/min
Hitting coasts of four states

40. Oil spills have severe consequences
Major oil spills cause severe environmental and economic problems
Major spills make headlines
Foul beaches
Coat and kill animals
Devastate fisheries
Countless non-point sources produce most oil pollution
Small boat leaks, runoff

41. Oil spills have decreased
Due to emphasis on spill prevention and response
Stricter regulations are resisted by the oil industry
The U.S. Oil Pollution Act (1990)
Created a $1 billion prevention and cleanup fund
Requires that all ships have double hulls by 2015
Recently, oil spills have decreased

42. Toxic pollutants contaminate seafood
Toxic pollutants can make food unsafe to eat
Mercury contamination from coal combustion and other sources bioaccumulates and biomagnifies
Dangerous to children and pregnant or nursing women
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

43. Excess nutrients cause algal blooms
Harmful algal blooms = nutrients increase algae that produce powerful toxins
Red tide = algae that produce red pigments that discolor water
Illness and death to wildlife and humans
Economic loss to fishing industries and beach tourism
Reduce runoff
Do not eat affected organisms

44. Emptying the oceans Overharvesting is the worst marine problem
We are putting unprecedented pressure on marine resources
Half the world’s marine fish populations are fully exploited and can’t be fished more intensively
28% of fish population are overexploited and heading to extinction
Total fisheries catch leveled off after 1988
Despite increased fishing effort
The maximum wild fisheries potential has been reached

45. The global fisheries catch has increased
It is predicted that populations of all ocean species we fish for today will collapse by 2048

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

47. Fishing has industrialized
Factory fishing = huge vessels use powerful technologies to capture fish in huge volumes
Even processing and freezing their catches at sea
Driftnets for schools of herring, sardines, mackerel, sharks, shrimp
Longline fishing for tuna and swordfish
Trawling for pelagic fish and groundfish

48. Fishing practices kill nontarget animals
Bycatch = the accidental capture of animals
Drift netting drowns dolphins, turtles, and seals
Fish die on deck
Banned in international waters
But it is still used in national waters
Longline fishing kills turtles, sharks, and over 300,000 seabirds/year
Methods (e.g., flags) are being developed to limit bycatch

49. Dolphins and tuna
Dolphins are trapped in purse seine nets used to catch tuna
Hundreds of thousands of dolphins were killed
The 1972 Marine Mammal Protection Act forced fleets to try to free dolphins
Bycatch dropped dramatically
Other nations fished for tuna, and bycatch increased
The U.S. government required that nations exporting tuna to the U.S. minimize dolphin bycatch
Dolphin-safe tuna uses methods to avoid bycatch

50. Dolphin deaths have declined, but …
Rules and technology have decreased dolphin deaths
Other animals (e.g., sharks) are still caught
Dolphins have not recovered
Too few fish to eat

51. Bottom-trawling destroys ecosystems
Heavy nets crush organisms and damage sea bottoms
It is especially destructive to complex areas (e.g., reefs)
It equals clear-cutting and strip mining
Georges Bank has been trawled three times
Destroying young cod as bycatch
The reason the cod stock is not recovering

52. Modern fleets deplete marine life rapidly
Grand Banks cod have been fished for centuries
Catches more than doubled with industrial trawlers
Record-high catches lasted only 10 years
George Bank cod fishery also collapsed

53. Industrialized fishing is destroying fisheries
Oceans today contain only one-tenth of the large-bodied animals they once did
Worldwide, industrialized fishing is depleting marine populations with astonishing speed
90% of large-bodied fish and sharks are eliminated within 10 years after fishing begins
Populations stabilize at 10% of their former levels
Communities were very different before modern fishing
Removing animals at higher trophic levels allows prey to proliferate and change communities

54. Several factors mask declines
Industrialized fishing has depleted stocks
But global catch has remained stable for the past 20 years
How can stability mask population declines?
Fishing fleets travel farther to reach less-fished areas
Fleets fish in deeper waters (now at 250 m)
Fleets spend more time fishing and set more nets
Improved technologies: faster ships, sonar mapping, satellite navigation, thermal sensing, aerial spotting
Fleets expend more effort to catch the same number of fish

55. We are “fishing down the food chain”
Figures on total global catch do tell the whole story
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 more abundant species
Shifting from large, desirable species to smaller, less desirable ones
This entails catching species at lower trophic levels

56. Purchasing 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
Avoid: Atlantic cod, wild- caught caviar, sharks, farmed salmon
Best choices: farmed catfish, mussels, oysters, tilapia

57. Diversity loss erodes ecosystem services
Factors that deplete biodiversity threaten ecosystem services of the oceans
Systems with reduced species or genetic diversity show less primary and secondary production
They are less able to withstand disturbance
Biodiversity loss reduces habitat for nurseries for fish and shellfish
Less diversity leads to reduced filtering and detoxification
Resulting in algal blooms, dead zones, fish kills, beach closures

58. Fisheries management
Based on maximum sustained yield to maximize harvest
While keeping fish available for the future
Managers may limit the harvest or restrict gear used
Despite management, stocks have plummeted
It is time to rethink fisheries management
Ecosystem-based management shifts away from species and toward the larger ecosystem
Considers the impacts of fishing on habitat quality, species interactions, and long-term effects
Sets aside areas of oceans free from human interference

59. We can protect areas in the ocean
Marine protected areas (MPAs) = most are along the coastlines of developed countries
They still allow fishing or other extractive activities
Marine reserves = areas where fishing is prohibited
Leave ecosystems intact, without human interference
Improve fisheries, because young fish will disperse into surrounding areas
Many commercial, recreation fishers, and businesses do not support reserves
Be sensitive to concerns of local residents

60. Reserves work for both fish and fisheries
Marine reserves:
Increased densities of organisms by 91%
Increased biomass by 192%
Increased organism size by 31%
Increased species diversity by 23%
Benefits inside reserve boundaries include:
Rapid and long-term increases in abundance, diversity, and productivity of marine organisms
Decreased mortality and habitat destruction
Decreased likelihood of extirpation of species

61. Areas outside reserves also benefit
A “spillover effect” occurs when individuals of protected species spread outside reserves
Larvae of species protected within reserves “seed the seas” outside reserves
Improved fishing and ecotourism
Local residents who were opposed support reserves once they see their benefits
Once commercial trawling was stopped on Georges Bank:
Populations of organisms began to recover
Fishing in adjacent waters increased

62. How should reserves be designed?
20–50% of the ocean should be protected in no-take reserves
How large?
How many?
Where?
Involving fishers is crucial in coming up with answers

63. Conclusion
Oceans cover most of our planet and contain diverse topography and ecosystems
As we learn about oceans and coastal environments, we are intensifying our use of their resources and causing severe impacts
We need to address acidification, loss of coral reefs, pollution, and fisheries depletion
Setting aside protected areas can maintain and restore natural systems and enhance fisheries
Consumer choices can help us move toward sustainable fishing

64. QUESTION: Review A “downwelling” is defined as:
The vertical flow of cold, deep water towards the surface
The vertical flow of warm, deep water towards the surface
Oxygen-rich water sinks
Oxygen-poor water sinks
Answer: c 64

65. QUESTION: Review
The area of an ocean that contains habitats on the ocean floor is called the _______ zone.
Littoral
Photic
Pelagic
Benthic
Answer: d 65

66. QUESTION: Review
_____ is defined as “a mass of calcium carbonate composed of the skeletons of tiny animals”.
A Coral reef
Red tide
Bottomfish
Kelp
Answer: a 66

67. QUESTION: Review Which statement about coral bleaching is correct?
Corals reproduce most efficiently in colder waters.
Fish move into coral reefs and kill them.
c) Zooxanthellae leave the coral due to climate change or pollution.
Coral reefs expand their range after they have been bleached.
Answer: c 67

68. QUESTION: Review
An area that occurs along coasts at temperate latitudes is called a(n):
Estuary
Mangrove swamp
Salt marsh
Coral reef
Answer: c 68

69. QUESTION: Review
Which of the following does NOT mask the decline of fisheries?
Fishing fleets travel longer distances to reach less-fished areas.
Fishing fleets spend more time fishing.
Fishing fleets use sophisticated methods of fishing.
Fleets fish in shallower waters nearer coasts.
Answer: d 69

70. QUESTION: Review
Marine reserves have all the following benefits EXCEPT:
Fishing increases in areas surrounding the reserve.
The size of fish decreases
Larvae can “seed” areas outside the reserve.
Decreased mortality and habitat destruction occur.
Answer: b 70

71. QUESTION: Viewpoints
What would you think about letting another country fish 10 miles off the U.S. coast?
That’s fine, as long as the fleet paid the United States.
Let them fish, but make them follow the same rules as U.S. fishermen.
Let only U.S. fishermen fish in these waters.
Prevent most fishing – we need to protect the last fish stocks.
Answer: any 71

72. QUESTION: Interpreting Graphs and Data
What does this graph show about the future of global fisheries catch?
China will apply major fishing pressure.
China’s role in fishing pressure will decline.
The world will decrease its fishing pressure.
The United States is not included in this graph.
Answer: a 72

73. QUESTION: Interpreting Graphs and Data
Which conclusion can you draw from this graph about commercial catches of Atlantic cod?
Intensified fishing increased and the fishery crashed.
It is easier to find fish today.
There is little correlation between fishing and fish stocks.
Moratoria will bring the stocks back.
Answer: a 73