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Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings PowerPoint ® Lecture prepared by Jay Withgott Scott Brennan Jay Withgott 9 Freshwater.

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Presentation on theme: "Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings PowerPoint ® Lecture prepared by Jay Withgott Scott Brennan Jay Withgott 9 Freshwater."— Presentation transcript:

1 Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings PowerPoint ® Lecture prepared by Jay Withgott Scott Brennan Jay Withgott 9 Freshwater and marine resources

2 Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings This lecture will help you understand: The hydrologic cycle and human interactions with it Freshwater ecosystems, distribution, depletion, and pollution Ocean currents Marine ecosystems Human impacts on marine environments Marine reserves and protected areas

3 Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings Central Case: Plumbing the Colorado River The once-mighty Colorado River is now dammed. So much water is withdrawn that it barely reaches the sea. Western states apportion the water according to a pact, but California has long exceeded its share. In 2003 the U.S. government cut California’s flow. Months of wrangling followed until a deal was reached.

4 Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings Freshwater Water that is relatively pure, with very few dissolved salts Freshwater occurs in: Lakes, rivers, streams, groundwater, glaciers, rainwater, soil, water vapor in the atmosphere (In contrast, ocean water is salty because salts from land run into it and stay there as surface water evaporates.)

5 Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings Freshwater Figure 14.1 Only 2.5% of the planet’s water is freshwater, and only 1% of that exists on Earth’s surface. Only 1 part in 10,000 of water is easily accessible for drinking and irrigation.

6 Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings Hydrologic cycle: Colorado River Air rising over the Rocky Mountains. drops precipitation that feeds the Colorado River’s headwaters. The air depleted of moisture creates a dry rainshadow east of the mountains. Figure 14.2

7 Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings Colorado River The river flows through arid country, nourishing ecosystems along its banks. It dumps into the Sea of Cortez, where a large estuary once flourished. Today so much water is withdrawn for irrigation and drinking supplies that the river barely makes it to the sea.

8 Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings Groundwater Water beneath Earth’s surface that did not evaporate, flow into rivers, or get taken up by organisms Plays key role in hydrologic cycle, and in meeting human needs 20% of all freshwater Groundwater is contained in aquifers.

9 Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings Aquifers Aquifer = a porous spongelike layer of rock, sand, or gravel that holds groundwater Confined or artesian aquifer = water under pressure, trapped within impermeable layers (often clay) Unconfined aquifer = water under less pressure; no overlying impermeable layer Aquifer recharge zone = geographic area where water infiltrates soil and recharges aquifer.

10 Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings Groundwater and aquifers Figure 14.3

11 Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings Freshwater distribution Global freshwater distribution is very uneven. Rainfall varies from nearly zero up to 1,200 centimeters (470 inches)/year. Canada has 20 times as much water per citizen as does China.

12 Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings Available freshwater resources Nations vary by more than a factor of 100 inches of water per capita. Figure 14.5a

13 Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings Available freshwater resources Asia has lots of water but very little water per capita. Australia has lots of water per capita but little water overall. Figure 14.5b

14 Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings Freshwater ecosystems: Rivers and streams Bodies of water that flow downhill, joining one another, shape the landscape. The beds of rivers move over time, depositing sediments over large areas of floodplain Figure 14.6a

15 Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings Freshwater ecosystems: Lakes and ponds Stationary bodies of water we call lakes and ponds also change slowly over time, through aquatic succession. Depending on nutrient input and other factors, these can be very productive and diverse ecosystems. Figure 14.6b

16 Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings Freshwater ecosystems: Wetlands Wetlands include freshwater marshes, swamps, and bogs. Wet areas with lush vegetation, they are especially productive and valuable for wildlife. Yet they are often destroyed by human development, as they occur in flat areas that can be developed if drained. Figure 14.6d

17 Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings How we use water Consumptive use = water is removed from an aquifer or surface body, and not returned. (most agricultural, industrial, and residential use) Nonconsumptive use = removal of water is only temporary. (passing water through a hydroelectric dam)

18 Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings How we use water: Agriculture Agriculture = 87% of world’s consumptive use of water Global consumption has risen in tandem with irrigation. Figure 14.8

19 Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings How we use water: Groundwater extraction 1 in 3 humans relies on groundwater for drinking. 99% of the rural U.S. relies on groundwater for drinking. Extraction from aquifers is increasing, especially in developing nations whose agriculture intensified with green revolution.

20 Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings How we use water: Surface diversion Colorado River water is heavily diverted today from a series of dams, mostly for agriculture. Figure 14.10a

21 Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings How we use water: Flood control We build dikes and levees to prevent floods when river levels rise. Flood control has saved many towns and crops from ruin. But long term, flood control can be self-defeating: Forces floodwater to stay in channel, creating risk of catastrophic overflow or dike break downstream Deprives farmland of nutrients that floods bring; decreases soil productivity

22 Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings How we use water: Dams We build dams blocking the flow of rivers in order to: Prevent floods Generate electricity Provide drinking water Provide irrigation 45,000 dams over 15 meters(49 feet) high have been built in the world. Few major rivers today are not dammed.

23 Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings Benefits and costs of dams Figure 14.11

24 Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings Benefits and costs of dams BENEFITS: Electricity generation Fewer emissions from hydropower generation Crop irrigation Drinking water supply Flood control Shipping New recreational opportunities COSTS: Habitat alteration Native fisheries decline Population displacement Disruption of flood cycles Sediment capture Lost recreational opportunities Risk of catastrophic failure

25 Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings The biggest dam yet China’s Three Gorges Dam across the Yangtze River is the world’s largest. Completed in 2003. Over 1 million people were displaced to build it. Farmland, archaeology, and habitat were submerged. Critics worry about sedimentation and water quality. Figure 14.12

26 Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings Dam removal In the U.S., some smaller dams are now being removed. Removal proponents want many larger dams removed too, as their licenses come up for renewal. Dam removal helps: Restore riparian ecosystems Reestablish economically vital fisheries (e.g., salmon) Reintroduce recreation (rafting, fly-fishing…)

27 Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings Viewpoints: Dams Sara Nicholas Thomas Flint “Many dams are obsolete, providing no direct economic, safety, or social function. These should be considered for removal. All dams harm riparian environments. Once a dam has outlived its usefulness, it makes great sense to restore the river back to its original condition.” “Dams and reservoirs address the needs of a growing world by efficiently storing and regulating water for multiple uses. Our world relies on the benefits they bring—drinking water, flood control, power generation, irrigation, and recreation.” From Viewpoints

28 Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings Freshwater depletion: Aral Sea The Aral Sea, in central Asia, was the fourth largest freshwater body on Earth, but it could disappear completely! Overirrigation for cotton was responsible in 1960, 1999, and 2002 Figure 14.13c

29 Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings Freshwater depletion: Aral Sea Satellite photo: Deep water today Shallow water today Dry former lake bed Figure 14.13b

30 Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings Freshwater depletion: Aral Sea The Aral Sea’s depletion has been devastating to the local people and their economies. Hundreds of ships lie stranded in the sand, because water fell so fast. Figure 14.13a

31 Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings Groundwater depletion Bigger threat than surface water depletion because aquifers recharge very slowly Water mining = withdrawing groundwater faster than it can be replenished Water tables in some areas are falling by 1–3 meters (3–9 feet)/year. The Ogallala Aquifer has lost the equivalent of yearly flow of 18 Colorado Rivers!

32 Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings Impacts of water mining Figure 14.14 When water is mined, ground may suddenly collapse in sinkholes. Other impacts: Slow subsidence (Venice, Mexico City) Saltwater intrusion into drinking water Soil compaction Wetland destruction

33 Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings Irrigation Figure 14.15 Most irrigation practiced today is very inefficient. Only 45% ends up being used by crops.

34 Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings A future of water wars? “The wars of the 21st century will be fought over water.” — Ismail Serageldin, Chairman of the World Water Commission Already, scarcity has caused or exacerbated conflict in arid areas: Colorado River states in southwest U.S. Israel and Palestinian Territories

35 Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings Solutions for depletion: Desalination Desalination or desalinization = removal of salt from seawater to create freshwater Perfecting this technology would mean the oceans could provide us with unlimited freshwater. But so far, it is expensive! Most of the world’s 7,500 desalination plants are in wealthy oil states of the Middle East, where water is scarce enough to make desalination economically feasible.

36 Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings Solutions for depletion: Reducing demand In AGRICULTURE: Use high-efficiency irrigation techniques Line irrigation canals to prevent leaks Level fields to reduce runoff Choose crops appropriate to climate Eliminate government subsidies of inappropriate crops and methods New GM crops?

37 Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings Solutions for depletion: Reducing demand In the INDUSTRIAL and MUNICIPAL sectors: Shift to processes that save water (and thus money) Invest in repairing pipe leaks Recycle “gray” wastewater

38 Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings Solutions for depletion: Reducing demand In the RESIDENTIAL sector (what YOU can do): Install low-flow faucets and appliances Use automatic dishwashers Replace lawns with native vegetation If you keep lawns, water them at night Recycle “gray” wastewater

39 Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings Freshwater pollution Over half of the world’s major rivers are “seriously depleted and polluted, degrading and poisoning the surrounding ecosystems, threatening the health and livelihood of people who depend on them.” —World Commission on Water, 1999 Groundwater pollution is extensive but invisible, a “covert crisis.”

40 Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings Indicators of water quality Scientists use chemical properties to measure water quality: pH: water’s acidity or alkalinity Hardness: hard water has high concentrations of salts Dissolved oxygen content: indicates suitability for life. High D.O. generally good for organisms. Taste and odor: can show presence of certain chemical contaminants

41 Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings Indicators of water quality Scientists use physical properties to measure water quality: Turbidity: density of suspended particles. Water with sediments from erosion is turbid. Color: indicates tannins and other chemicals Temperature: aquatic organisms sensitive to temperature; warm water holds less dissolved oxygen

42 Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings Indicators of water quality Scientists use biological properties to measure water quality: Presence of pathogens: disease-causing organisms may be present, making water risky for drinking.

43 Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings Water pollution: point and non-point sources Figure 14.17

44 Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings Types of pollution: Pathogens Waterborne disease from viruses, bacteria, etc., contributes to 5 million deaths per year. Diarrhea: 4 billion cases/year, 2.2 million deaths Intestinal worms: 1 in 10 people in developing world Blindness from trachoma: 6 million people Schistosomiasis from blood flukes: 200 million people

45 Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings Types of pollution: Eutrophication Excess runoff of nutrients like nitrogen and phosphorus leads to blooms of algae or phytoplankton… … and then microbial decay that sucks oxygen from the water (e.g., the hypoxic zone in the Gulf of Mexico)

46 Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings Eutrophication Excess nutrients promote algal growth… and its decay depletes water of oxygen needed by fish. Figure 14.18a

47 Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings Eutrophication Figure 14.18b,c Oligotrophic water bodyEutrophic water body

48 Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings Types of pollution: Synthetic chemicals Many thousands of chemicals we manufacture find their way into our water, where some have toxic effects. Pesticides Petroleum products Arsenic, lead, mercury, other metals Acids from mining runoff and acid precipitation

49 Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings Types of pollution: Sediment Erosion of soil from mining, clear-cutting, real estate development, and farming puts sediment into waterways. There it alters conditions and can kill organisms.

50 Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings Types of pollution: Heat and cold Yes, even heat and cold can pollute! Organisms not adapted to the new temperature conditions can suffer or die. Warm water from power plants decreases dissolved oxygen. Clearing streamside vegetation also warms water. Cold water is released below dams, harming native fish.

51 Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings Groundwater pollution Worse than surface water pollution, because it is longer lasting (e.g., persistent toxicants get washed out of rivers, but remain in groundwater until they break down.)

52 Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings Groundwater pollution Sources are both natural and anthropogenic. NATURAL SOURCES: Arsenic Aluminum Fluoride Nitrates Sulfates HUMAN SOURCES: Leaky underground storage tanks (oil, gas, industrial chemicals, septic waste) Nitrates from fertilizers Pesticides Pathogens from wells and feedlots Contamination from underground hazardous waste disposal Industrial chemical waste Compounds from military sites

53 Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings Thousands of wells dug by international aid workers for the benefit of Bangladesh’s citizens turned out to be poisoned with natural sources of arsenic. From The Science behind the Stories Mapped arsenic concentrations; red is highest Groundwater pollution

54 Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings Solutions for freshwater pollution In AGRICULTURE: Reduce erosion to minimize sediment pollution Use fewer or less toxic pesticides Use fewer fertilizers Properly treat animal waste

55 Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings Solutions for freshwater pollution In the INDUSTRIAL and MUNICIPAL sectors: Shift to processes that produce less waste Shift to less-toxic chemicals and products Invest in reducing leaks Properly treat wastewater Restrict use of pollutants over aquifers Follow government regulations for health and safety

56 Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings Solutions for freshwater pollution In the RESIDENTIAL sector (what YOU can do): Buy phosphorus-free detergents and other “environmentally friendly” products Dispose of hazardous waste properly, not down a drain Get involved in monitoring your local watershed; join or start a grassroots “riverwatch” group Press politicians to support clean water

57 Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings Success stories Many water pollution problems have decreased since the 1960s and 1970s, due to legislation: Clean Water Act of 1977 in the U.S. Similar acts in other nations The Great Lakes: Canadian and U.S. governments decreased PCBs, DDE, fertilizers, etc., by 70–90%. Fish and bird populations are now recovering.

58 Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings Marine Systems Oceans cover 71% of Earth’s surface. Oceans contain 97.2% of the planet’s surface water.

59 Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings The one world ocean The world’s oceans are connected in one vast water body. Figure 13.2

60 Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings Ocean water composition The oceans consist of (by mass): 96.5% water 3.0% sodium and chlorine ions (table salt, Na + and Cl – ) 0.5% other salts Figure 13.3

61 Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings Ocean currents Currents = vast river- like flows in the surface waters of the ocean Driven by density differences, sunlight, wind Can be cool or warm Vary in size and speed Influence climate Figure 13.5b

62 Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings Major surface currents of the world’s oceans Figure 13.5a

63 Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings Vertical movement of ocean water Ocean water can move up or down due to wind, heating, or density differences. Upwelling = cold deep water comes to surface Occurs where currents diverge Brings nutrients to surface; promotes fisheries Downwelling = warm surface water moves downward Occurs where currents converge Brings dissolved oxygen to deep-water life

64 Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings Upwelling Water along the California coast moves away from shore, allowing upwelling that nourishes biodiversity in surface waters. Figure 13.6

65 Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings Bathymetry Underwater topography reveals several major features: Gently sloping continental shelves underlie shallow waters around continents. The topographys drops down along continental slopes and continental rises to abyssal plains. Volcanic activity may create a trench where one plate is subducted beneath another. Magma erupting from plate boundaries may create mountains that break the water’s surface to become islands.

66 Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings Bathymetry Figure 13.8 Pelagic zone = open water between surface and seafloor Benthic zone = ocean floor

67 Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings Marine ecosystems: Open ocean Surface waters of the pelagic zone are variable in their biology. Many areas are scarce in life, but areas like nutrient-rich upwellings teem with life. Plankton (photo) are the base of the food chain. Figure 13.10

68 Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings Marine ecosystems: Deep ocean Deep waters are devoid of sunlight, so ecosystems cannot rely on plant growth. Animals here (few and far between) scavenge detritus from above, or prey on each other, or have symbiotic microbes that produce food for them. Figure 13.11 The anglerfish is one of many bizarre-looking deep-sea creatures. The luminescent projection on its forehead attracts curious fish, which it eats.

69 Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings Marine ecosystems: Kelp forests Kelp (large brown algae or seaweed) grows up to 60 meters (200 feet) tall from the continental shelves. It creates “forests” that harbor and feed many other organisms. Figure 13.12

70 Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings Marine ecosystems: Coral reefs Corals (photo) = tiny invertebrate animals that occur in huge numbers together. As they die, skeletons build coral reefs out of calcium carbonate. Reefs provide habitat, protection, and food for many other animals. Coral reefs are a key ecosystem for biodiversity. Figure 13.13

71 Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings Marine ecosystems: Intertidal zones Intertidal or littoral ecosystems occur along rocky beaches. Tides cover organisms most of each day, and leave them exposed to air or bathed in tidepools part of the day. High biodiversity: Starfish, crabs, sea urchins, algae, etc. Must endure extreme fluctuating conditions Figure 13.15b

72 Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings Marine ecosystems: Salt marshes Grassy salt marshes cover intertidal areas with sandy or silty substrate in temperate regions. They have high primary productivity, but people often drain for coastal development. Figure 13.16

73 Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings Marine ecosystems: Mangrove forests In tropical and subtropical regions, sandy/silty beaches host forests of mangroves, bushy trees adapted to salt water. Many animals find homes among the root networks. These forests are often lost to human development. Figure 13.17

74 Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings Marine ecosystems: Estuaries Many salt marshes and mangrove forests occur near estuaries, areas where rivers flow into the ocean and mix fresh with salt water. Biologically very productive: fish, birds, invertebrates

75 Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings Human use of oceans Transportation routes—early exploration; modern shipping Commercial fishing Mining minerals Energy sources, e.g., offshore oil Recreation

76 Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings Ocean pollution: Debris Garbage that litters the ocean doesn’t merely look ugly on beaches. It can kill marine life. Turtles die from eating plastic bags that look like jellyfish. Discarded fishing nets tangle seals and drown them. Plastic 6-pack rings strangle birds.

77 Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings Ocean pollution: Oil We get much of our petroleum from seafloor deposits drilled from offshore platforms. Some pollution results, but natural seeps in such areas also spurt oil into the ocean. Oil spills from tankers transporting oil are what grab headlines. Though rare, these can cause great damage locally. Figure 13.18

78 Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings Ocean pollution: Oil Better prevention and response are beginning to reduce amounts of oil spilled into the oceans in major tanker spill events. BUT most oil entering the ocean is runoff coming from numerous minor sources on land. The oil leaking from your car finds its way to the sewer system, rivers, and, eventually, the ocean. Figure 13.19

79 Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings Ocean pollution: Algal blooms Excess nutrient runoff (as from fertilizers) can spur out-of- control growth of algae that kill fish and other organisms. These harmful algal blooms are also called red tides because some types color water red. Figure 13.20

80 Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings Pollution solutions All these problems can be addressed: Reduce plastic waste by reusing bags, buying less packaging, cutting 6-pack rings, etc. Strengthen regulations on oil tankers further to minimize major spills. Reduce oil runoff by disposing of hazardous waste safely. Reduce fertilizer use to lessen chance of red tides.

81 Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings Emptying the oceans As bad as some pollution problems may be, the oceans today suffer most from overfishing. Oceans are vulnerable to the “tragedy of the commons.” Depletion is not a new problem: For centuries people approached fishing as if “there’s always more fish in the sea.” Fishing had already taken a toll on marine ecosystems many decades before ecologists began studying them.

82 Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings Collapsing stocks Overfished stocks (orange) increased tenfold, 1950-1994. Collapsing stocks hurt fishing communities as well as fish. Figure 13.23

83 Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings Fishing practices Many marine fishing practices are not specifically targeted to the species fishermen want to catch. Instead, they catch lots of nontarget species. This is the by-catch. By-catch accounts for deaths of many thousands of sharks, seals, dolphins, turtles, and birds each year.

84 Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings Fishing practices Driftnetting catches and drowns many seals, dolphins, birds, turtles. Longlining kills albatrosses and other seabirds, as well as turtles and sharks. Bottom-trawling destroys whole ecosystems. Nets and bars dragged across the bottom flatten benthic structure, devastating habitat for marine organisms. Figure 13.24

85 Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings Traditional fisheries management Based on maximum sustainable yield (MSY): Allow maximal harvests of particular populations while keeping fish available for the future Managers regulate catch with limits, quotas, seasons, etc. Many marine conservation biologists today say MSY has failed. Instead of single-species MSY, we need to manage for entire ecosystems: Set aside no-fishing areas to protect whole systems.

86 Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings MPAs and marine reserves Many marine protected areas (MPAs) have been established—over 200 in U.S. waters alone. But these do not fully protect resources. Plenty of fishing and other activities can go on in MPAs. Marine reserves are no-fishing zones where absence of human impact allows fish to live and breed without interference. These “no-take” areas should preserve whole ecosystems and increase fish populations for fisheries.

87 Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings Fishermen have opposed marine reserves Understandably, many fishermen reject the idea of no-take zones where fishing is banned. Conservationists are trying to convince them that no-take marine reserves HELP fishing by restoring fish populations inside the reserve, allowing young fish to populate areas outside the reserve that CAN be fished. They say reserves are a win-win proposition.

88 Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings Do marine reserves work? A review of marine reserves showed that within 1–2 years they: Increased density of organisms 91% Increased biomass of organisms 192% Increased size of organisms 31% Increased species diversity 23%

89 Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings Small reserve: Fish wander out of reserve, are not protected. No gain for anyone. Medium reserve: Big enough to conserve fish. Small enough to let some out for fishermen to catch. Good balance of benefits for everyone. Large reserve: Good preservation, but too few fish leave reserve to be caught. Not acceptable to fishermen. Figure 13.25 How best to design reserves?

90 Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings Do marine reserves work? A study in the Caribbean showed biomass increasing more in areas that were made reserves, relative to those that weren’t. From The Science behind the Stories

91 Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings Conclusions: Challenges Coastal ecosystems like coral reefs, mangroves, salt marshes, and estuaries are hard hit by human impact. Several types of pollution affect the oceans. Fishing stocks are seriously depleted, and many are nearing collapse. Several fishing practices cause substantial by-catch. Marine reserves have met opposition from fishermen.

92 Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings Conclusions: Challenges The uneven distribution of water creates potential for scarcity and conflict as populations grow. Freshwater ecosystems have been greatly degraded by depletion and pollution of water. We are depleting surface and groundwater sources. Dams create many problems as well as benefits. Pollution of surface and groundwater sources is having health and ecological impacts.

93 Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings Conclusions: Solutions Coastal residents need to be made aware of the ecological and economic importance of saving local ecosystems. Marine pollution can be reduced through citizen action and consumer behavior as well as through laws and regulations. Unless traditional MSY is greatly strengthened, no-take reserves appear necessary to restore fisheries. Methods to reduce by-catch are being developed, such as colored flags on longlines that warn seabirds of the lines. Scientists are compiling more data showing that marine reserves help fisheries and are talking with fishermen.

94 Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings Conclusions: Solutions Although future “water wars” threaten, many nations have already entered into treaties to share water. Freshwater ecosystems (like the Great Lakes) can be restored if citizens push governments to take action. Many solutions exist for agriculture, industry, government, and consumers to conserve water. Dams with more costs than benefits can be removed. Many solutions exist for agriculture, industry, government, and consumers to reduce water pollution.

95 Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings QUESTION: Review In regions of upwelling… ? a.Warm water moves upward, displacing cold water. b.Cold water transports dissolved gases upward. c.Nutrients are brought upward by cold water. d.Warm water moves upward and then along the coast.

96 Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings QUESTION: Review Where might you find a kelp forest? a.In the Mississippi River Valley b.On the abyssal plain of the Atlantic Ocean c.On the continental shelf off the California coast d.Near a hydrothermal vent off British Columbia e.In the pelagic portion of the Indian Ocean

97 Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings QUESTION: Review Which statement about coral is NOT true? a.Their skeletons help build reefs. b.They feed by swimming in areas of upwelling. c.They feed by using stinging tentacles. d.Creatures living inside them provide nutrition via photosynthesis. e.They provide habitat for other creatures.

98 Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings QUESTION: Review What is meant by “fishing down the food chain”? a.Catching herbivorous fish species b.Catching species that are producers c.Using high-tech equipment to find large individuals d.Catching species on lower trophic levels, after depletion of other species e.Using producer species to catch consumer species

99 Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings QUESTION: Weighing the Issues Almost 4% of U.S. land area is designated wilderness, but far less than 1% of coastal waters are protected in reserves. Why has it taken so long for the preservation ethic to reach the oceans? a.The oceans need preservation less than terrestrial systems. b.Fewer environmentalists care about the oceans than about the land. c.Because people don’t generally look underwater, we were unaware until recently what bad shape the oceans were in.

100 Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings QUESTION: Interpreting Graphs and Data Figure 13.23 Which statement is correct? a.Undeveloped fisheries have increased over time. b.Senescent fisheries have increased over time. c.Fully developed fisheries have decreased over time. d.In 1967 there were more senescent fisheries than developing fisheries.

101 Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings QUESTION: Review Which of the following is NOT true about aquifers? a.They hold surface water. b. They can be “confined” or “unconfined.” c. They can become polluted by numerous toxic substances. d.They generally are very slow to recharge.

102 Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings QUESTION: Review Which water body would contain many nutrients and low oxygen levels? a.An oligotrophic lake b.A eutrophic lake c.A pristine fast-flowing mountain stream d.The deep ocean e.All of the above

103 Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings QUESTION: Review Which of the following is NOT true about dams and their associated reservoirs? a.They alter riparian habitat. b.They can capture sediment. c.They can provide irrigation, hydropower, flood control, and drinking water. d.They can never be removed once built. e.They promote some types of recreation and inhibit others.

104 Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings QUESTION: Review Which is a possible effect of groundwater depletion? a.Subsidence and sinkholes b.Sediment capture c.Saltwater intrusion into aquifers d. Both (a) and (b) e. Both (a) and (c)

105 Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings QUESTION: Weighing the Issues As cities of the arid U.S. southwest grow and water becomes scarce, what should these metropolises do? a.Pull as much water as they can from the Colorado River b.Build desalination plants c.Regulate industry and agriculture more heavily to restrict water waste d.Promote conservation measures through education and market incentives

106 Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings QUESTION: Viewpoints Should we remove dams? a.Yes; they have more costs than benefits. b. Sometimes; we should judge them on a case-by- case basis. c.No; they have more benefits than costs. No; money and resources are best spent on other things.


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