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Transcript
16 Marine and Coastal Systems: Resources, Impacts, and Conservation Chapter Objectives This chapter will help students: Identify physical, geographical, chemical, and biological aspects of the marine environment Describe major types of marine ecosystems Outline historic and current human uses of marine resources Assess human impacts on marine environments Review the current state of ocean fisheries and reasons for their decline Evaluate marine protected areas and reserves as innovative solutions Lecture Outline I. Central Case: Collapse of the Cod Fisheries A. No fish had more impact on human civilization than the Atlantic cod. B. This abundant groundfish (fish that feed on the bottom of the ocean) was a dietary staple in cultures on both sides of the Atlantic. C. Cod provided the economic engine for many communities along coastal New England and Canada. D. After decades of technologically advanced fishing techniques harvested many mature breeding adults, the cod populations in the Atlantic “crashed.” E. Government officials in Canada, followed by U.S. officials, closed fishing areas to all commercial fishing. In most of the areas, the cod have not rebounded. IG-230 1. It is believed that cod remain limited because the former prey of adult cod are now competing for food with and even eating young cod before they can mature. 2. A bright spot in the story is that areas of the Georges Bank are recovering due to elimination of destructive practices such as trawling. Some other species are recovering such as Ocean Scallops. There is evidence that young cod are beginning to appear as well. II. The Oceans 1. The study of the physics, chemistry, and geology of the oceans is called oceanography. 2. Oceans influence global climate, teem with biodiversity, facilitate transportation and commerce, and provide us resources. A. Oceans cover most of Earth’s surface. B. The oceans contain more than water. 1. Ocean water is salty because the ocean basins are the final repositories for water that runs off the land. 2. The salinity of ocean water generally ranges from 33 to 37 parts per thousand (ppt), varying from place to place because of differences in evaporation, precipitation, and freshwater runoff from land and glaciers. 3. Seawater also contains nutrients such as nitrogen and phosphorus that play essential roles in nutrient cycling. 4. Another aspect of ocean chemistry is dissolved gas content, particularly the dissolved oxygen upon which gill-breathing marine animals depend. C. Ocean water is vertically structured. 1. Water density increases as salinity rises and as temperature falls, giving rise to different layers of water. 2. The waters of the surface zone are heated by sunlight each day and are stirred by wind. 3. The pycnocline is the region below the surface zone in which density increases rapidly with depth. 4. The deep zone of the ocean lies beneath the pycnocline and is not affected by wind and sunlight. 5. Oceans help regulate Earth’s climate by absorbing and releasing heat to the atmosphere. D. Ocean water flows horizontally in currents. 1. The ocean surface is composed of currents—vast, riverlike flows driven by density differences, heating and cooling, gravity, and wind. 2. Currents transport heat, nutrients, pollution, and the larvae of many marine species. E. Vertical movement of water affects marine ecosystems. 1. Upwelling is the vertical flow of cold, deep water toward the surface, bringing nutrients from the bottom. 2. Downwelling transports warm water rich in dissolved gases downward, providing oxygen for deep-water life. IG-231 F. Seafloor topography can be rugged and complex. 1. Parts of the ocean floor are just as complex as the terrestrial portion of the lithosphere. 2. In the bathymetric profile, gently sloping continental shelves underlie the shallow waters bordering continents. 3. Most of the seafloor is flat, but there are volcanic peaks, reefs, and deep trenches. 4. Oceanic zones differ greatly, and some support more life than others. a. The well-lit top 10 meters, called the photic zone, contains nearly all of the oceans’ primary productivity. b. Between the ocean’s surface and the floor are the pelagic habitats. c. On the ocean floor is the benthic area. III. Marine Ecosystems A. Open-ocean ecosystems vary in their biological diversity. 1. Much of the ocean’s life is concentrated near the surface in areas of nutrient-rich upwelling. These areas include a variety of photosynthetic species and many free-swimming animals. 2. In the deep ocean, animals are adapted to deal with extreme water pressures and to live in the dark. 3. Some extremely deep ecosystems cluster around hydrothermal vents. B. Kelp forests harbor many organisms in temperate waters. 1. Kelp is a large, brown algae, with some types reaching 200 feet in length. C. Coral reefs are treasure troves of biodiversity. 1. A coral reef is a mass of calcium carbonate composed of the skeletons of tiny colonial marine organisms called corals. 2. Corals are tiny invertebrate animals related to sea anemones and jellyfish. 3. Coral animals capture food with stinging tentacles and also derive nourishment from symbiotic algae, known as zooxanthellae, which inhabit their bodies and produce food through photosynthesis. 4. Coral reefs host an incredible diversity of life, and they protect shores from damage by waves and storms. 5. Coral reefs are experiencing worldwide declines, probably due to increased sea surface temperatures and the influx of pollutants. D. Intertidal zones undergo constant change. 1. The intertidal or littoral zone lies along shorelines between low tide and high tide. 2. Tides are the periodic rising and falling of the ocean’s height at a given location, caused by the gravitational pull of the moon and sun. 3. The intertidal zone is a tough place to make a living, but is home to a remarkable diversity of organisms. IG-232 4. The rocky intertidal zone is so diverse because environmental conditions change dramatically from the low part of the intertidal zone to the high part. E. Salt marshes cover large areas of coastline in temperate areas where tides wash over gently sloping sandy or silty substrates. 1. Salt marshes filter pollution, buffer the coastal regions from storm surges and are prime sites for development worldwide. 2. Destruction of the salt marsh community near New Orleans, caused impact from Hurricane Katrina to be more severe. F. Mangrove forests line coastlines throughout the tropics and subtropics. 1. Mangroves are trees with unique types of roots that curve upward like snorkels to obtain oxygen. 2. Mangrove forests serve as nurseries for fish and shellfish, providing economic benefit to residents. 3. In south Florida and elsewhere, mangrove forests have been removed as people have converted coastal areas to residential, recreational, and commercial uses. G. Freshwater meets salt water in estuaries. 1. Estuaries are areas where rivers flow into the ocean, mixing freshwater with salt water. 2. Estuaries provide critical habitat for many organisms. 3. Estuaries around the world have been affected by urban and coastal development. IV. Human Use and Impact A. The oceans provide transportation routes. B. We extract energy and minerals. 1. By the 1980s, about 30% of our production of crude oil and nearly half of our natural gas came from exploitation of ocean deposits. 2. Methane hydrate is an icelike solid consisting of molecules of methane (CH4, the main component of natural gas) embedded in a crystal lattice of water molecules. a. The U.S. Geological Survey estimates that the world’s deposits of methane hydrates may hold twice as much carbon as all known deposits of oil, coal, and natural gas combined. b. Destabilizing a methane hydrate deposit could lead to a catastrophic release of gas, which could cause a massive landslide and tsunami. This event would also release huge amounts of methane, a potent greenhouse gas, into the atmosphere, exacerbating global climate change. 3. We extract minerals from the seafloor. C. Marine pollution threatens resources. D. Nets and plastic debris endanger marine life. 1. Because most plastic is not biodegradable, it can drift for decades before washing up on beaches, and may be mistaken for food by marine mammals, seabirds, fish, and sea turtles, which may die as a result of ingesting it. IG-233 2. Lost or discarded fishing nets frequently continue snaring animals for decades. 3. In December 2006, the U.S. Congress responded to these threats and sent the Marine Debris Research, Prevention, and Reduction Act to President George Bush for his signature. E. Oil pollution comes from spills of all sizes. 1. The majority of oil pollution comes not from large spills, but from the accumulation of innumerable widely spread small sources. 2. Minimizing the amount of oil we release is important because petroleum pollution is detrimental to the marine environment and the human economies that draw sustenance from that environment. 3. Over the past three decades, the amount of oil spilled in U.S. waters and worldwide has decreased, in part because of an increased emphasis on spill prevention and response. F. Toxic pollutants can contaminate seafood. 1. Mercury is a central nervous system toxin and can have severe neurological impact on a developing fetus. 2. Mercury is emitted from combustion of coal in power plants. G. Excess nutrients can cause algal blooms. 1. The release of excess nutrients into surface waters can spur unusually high growth rates of algae, called harmful algal blooms. Some algal species produce reddish pigments, and blooms of these species are nicknamed red tides. 2. Harmful algal blooms can cause illness and death among zooplankton, birds, fish, marine mammals, and humans as their toxins are passed up the food chain. V. Emptying the Oceans A. We have long overfished. 1. A recent synthesis of historical evidence revealed that ancient overfishing likely affected ecosystems in astounding ways that we only partially understand today. 2. Florida Bay is suffering today from the overhunting of green sea turtles in past centuries. 3. If current trends continue, a comprehensive 2006 study in the journal Science predicts that all fish species humans harvest from the oceans will collapse by 2048. B. Fishing has industrialized. 1. Modern commercial fishing fleets use fossil fuel, huge boats, and advanced technologies to harvest unimaginable amounts of ocean life. 2. Many vessels today are able to capture, process, and freeze their catch in a vertically integrated operation. This technique is called factory fishing. C. Fishing practices kill nontarget animals and damage ecosystems. 1. By-catch refers to the accidental capture of animals, and it accounts for the deaths of many thousands of fish, sharks, marine IG-234 mammals, and birds each year. Driftnetting, longlining, and bottom-trawling are all techniques that are responsible for huge fish catches but also for massive catches of nontarget animals. Modern fishing fleets deplete marine life rapidly. 1. The percentage of oceanic fish stocks that are overfished increased tenfold from 1950 to 1994. 2. A prime example of fishery collapse took place in the 1990s with groundfish fisheries in the North Atlantic off the Canadian and U.S. coasts. 3. Removing top trophic level feeders from marine ecoystems causes their prey species to proliferate. Many scientists conclude marine ecosystems were probably very different ecosystems prior to commercial fishing. Several factors mask declines. 1. Despite the fact that fish stocks have been depleted in region after region as industrialized fishing has intensified, the amount of overall global fish production has remained stable for 15 years. 2. Fishing fleets travel longer distances, fish in deeper waters, spend more time fishing, and set out more nets and lines. 3. Improved technology, including sonar mapping, satellite navigation, and thermal sensing systems, also helps to explain high catches. We are “fishing down the food chain.” 1. Fisheries data reveal that as fishing increases, the size and age of fish caught decline. 2. We are also shifting from large, desirable species that have become rare to smaller, less desirable ones. Some fishing practices kill nontarget animals and damage ecosystems. 1. Many fishing practices catch more than target species. By-catch refers to the capture of unintended animals including fish, sharks, marine mammals, and birds. a. Boats that drag driftnets through the water capture substantial numbers of large nontarget species. This method has been banned or restricted by many nations. b. Longline fishing involves dragging extremely long lines with baited hooks spaced along their lengths, resulting in a large by-catch. c. Bottom-trawling involves dragging weighted nets over the floor of the continental shelf to catch benthic organisms, resulting in damage to entire benthic ecosystems. Trawling crushes many organisms and leaves long swaths of damaged sea bottoms. Consumer choice can influence fishing practices. 1. Purchasing ecolabeled seafood products exercises consumer choice, and thus influences the fishing industry. 2. Several nonprofit organizations have devised guides to help consumers make ecologically sound choices Marine biodiversity loss erodes ecosystem services. 2. D. E. F. G. H. I. IG-235 VI. Marine Conservation A. Fisheries management has been based on maximum sustainable yield. 1. The goal of this strategy is to allow for maximal harvests of particular populations while keeping fish available for the future. 2. Despite such efforts, many fish stocks have plummeted. 3. A suggested key change is to shift the focus from individual fish species toward viewing the larger ecological system, considering the effects of fishing practices on habitat quality, and other factors. B. We can protect areas in the ocean. 1. Large numbers of marine protected areas (MPAs) have been established, mostly along coastlines of developed countries. Nearly all MPAs allow fishing and other extractive activities. 2. The United States is now inventorying areas for inclusion in a national network of MPAs. 3. Because of the lack of refuges from fishing pressure, many scientists have urged the establishment of areas where no fishing is allowed. These areas are called marine reserves and are designed to preserve entire ecosystems intact and to improve fisheries. C. Reserves can work for both fish and fishers. 1. Data indicate that marine reserves do work, boosting fish biomass and total catch while decreasing habitat destruction. D. How should reserves be designed? 1. How large do reserves need to be, how many should there be, and where should they be placed? 2. Involving fishers directly in the planning process is crucial. 3. Studies have estimated that from 10% to 65% of the ocean should be protected in no-take reserves. Most estimates range between 20% and 50%. 4. Other studies are modeling how to optimize the size and spacing of individual reserves so that ecosystems are protected, fisheries are sustained, and people are not overly excluded from marine areas. VII. Conclusion A. In the Florida Keys and hundreds of other areas around the country, scientists are gradually demonstrating that setting aside protected areas can serve to maintain natural systems and enhance fisheries. B. As historical studies reveal more information on how much biodiversity our oceans formerly contained and have lost, we may increasingly consider restoring the ecological systems that used to flourish. Key Terms benthic by-catch continental shelf coral reef IG-236 current downwelling estuary factory fishing groundfish harmful algal bloom intertidal kelp littoral mangrove marine protected areas (MPAs) marine reserve methane hydrate oceanography pelagic pycnocline red tide salt marsh tide upwelling Teaching Tips 1. Provide students with information about a marine sanctuary found in or near your region. There are a growing number of sanctuaries in the United States, and information about them can be found at www.sanctuaries.nos.noaa.gov. 2. This chapter introduces several ocean habitats, such as mangroves and seagrass beds, kelp forests and coral reefs, and tidepools and salt marshes. It is important to emphasize that these ecosystems serve as nurseries for many juvenile fish and invertebrates. Assign groups of students to study various ocean habitats (e.g., all of the above, plus barrier islands and barrier reefs, polar ice caps, pelagic and deep-water habitats, and ocean vents) and have each group create a poster or presentation on the locations around the world, the food webs, major threats to the area posed by humans, and the area’s importance to our way of life. 3. Use tide tables to teach the concept of tides. Tide tables that show predicted high and low tides at sites across the country can be accessed from NOAA at http://tidesandcurrents.noaa.gov. The site has both tables and graphs that can be displayed in a variety of ways. One suggestion is to create a tidal graph for the period from August 24 through September 10, 2005, for the East Bank 1, Norco—the measuring station at the southwestern edge of Lake Ponchartrain, Lousiana. This includes the time period before, during, and after Hurricane Katrina. For further information about Hurricane Katrina’s effects on the Gulf Coast, read the levee research at http://soundwaves.usgs.gov/2006/01/ and the offshore research at http://soundwaves.usgs.gov/2006/01/fieldwork3.html. IG-237 4. The text discusses overfishing and by-catch in the world’s oceans, as well as some of the issues with fish farms. Show students the Monterey Bay Aquarium’s Seafood Watch web page (www.mbayaq.org/cr/seafoodwatch.asp), which helps consumers make choices for healthy oceans. The website explains the aquarium’s seafood guides and lists fish and shellfish—domestic, foreign, domestic farmed, and foreign farmed—with recommendations for or against purchase, based on the sustainability of the methods used to catch or to raise the organisms. There is no information on mercury contamination, other than in a pocket guide that shows a red asterisk next to those species listed in a mercury advisory from the United States Food and Drug Administration and the Environmental Protection Agency. For more information about mercury in ocean-caught fish, see the USDA’s Food Safety Research Information Office fact sheet Mercury Levels in Commercial Fish and Shellfish (www.cfsan.fda.gov/~frf/seamehg.html). 5. Questions are an important tool for instructors, both in classroom interactions and in written materials such as labs, quizzes, and exams. Benjamin Bloom created a Taxonomy of Educational Objectives, which organizes questions into six basic categories based on the level of thinking involved. The first two categories, Knowledge and Comprehension, are very basic informational categories. When you ask for a definition or give a set of matching questions on an exam, you are having students recall knowledge, possibly verbatim. You have no way of gauging whether they understand the information; you only discover whether they have memorized it. The next two categories, Application and Analysis, involve asking students to apply information to solve a problem or use what they have learned to analyze a new situation. Application may still be at the level of rote memorization (when given a problem of type x, use method y to solve it). Analysis, however, is the beginning of what are considered to be the higher-order thinking skills that we would like to foster in our students. The final two categories, Synthesis and Evaluation, require students to use multiple resources to create new information, develop new ways of looking at current information, or generate appropriate criteria to assess a situation. In an entry-level course, many of the questions will necessarily be at the levels of Knowledge and Comprehension as students learn the terminology and basic concepts. However, it is very important to move beyond those levels, and to require students to analyze, synthesize, and evaluate both in class discussions and in written work. This is where the course truly begins to be relevant and applicable to the students’ lives, as they become capable of using the concepts to understand current events and the issues that affect their own communities and families. IG-238 Bloom’s Taxonomy is also useful as you plan a course. You will want to ensure that some of your course objectives are drawn from the higher levels of thinking. Some excellent websites that provide useful information, including sample lists of verbs that will help you write exams, are www.coun.uvic.ca/learn/program/hndouts/bloom.html and http://faculty.washington.edu/krumme/guides/bloom.html. Two sites that use a taxonomy wheel to illustrate the ways to use the various levels of thinking are www.stedwards.edu/cte/resources/bwheel.htm and www.in2edu.com/downloads/thinking/blooms_taxonomy_chart.pdf. Additional Resources Websites 1. CoRIS: Coral Reef Information System, National Oceanic and Atmospheric Administration, United States Department of Commerce (www.coris.noaa.gov) This website gives users access to coral reef data and maps as well as detailed information about coral reef biology. 2. National Marine Sanctuaries, National Oceanic and Atmospheric Administration, United States Department of Commerce (www.sanctuaries.nos.noaa.gov) This is the official home page for the National Marine Sanctuaries Program with information about the history and current management of our nation’s marine sanctuaries. 3. Oceans Alive, The Museum of Science (www.mos.org/oceans) This web resource has information about ocean formation, physical characteristics of oceans, water cycle, tides, currents, ocean life, and how marine scientists conduct their research. 4. Secrets of the Ocean Realm, PBS Online (www.pbs.org/oceanrealm) This website provides information and classroom activities about unique and fascinating creatures that inhabit the ocean’s depths. 5. Wetlands, Oceans and Watersheds, United States U.S. Environmental Protection Agency.(EPA) (www.epa.gov/OWOW) This website provides information and classroom activities abou unique and fascinating creatures that inhabit the ocean’s depths. 6. Ocean Conservancy promotes healthy and diverse ocean ecosystems and opposes practices that threaten ocean life and human life. Through research, education, and science-based advocacy, Ocean Conservancy informs, inspires, and empowers people to speak and act on behalf of the oceans. In all its work, Ocean Conservancy strives to be the world’s foremost advocate for the IG-239 oceans. Projects include: restoring sustainable North American fisheries, protecting wildlife from human impact, conserving special ocean places, and reforming government for better ocean stewardship. (www.oceanconservancy.org) Audiovisual Materials 1. Canary of the Ocean: America’s Troubled Reef, 1997, produced and distributed by Miranda Productions (www.mirandaproductions.com/canary) This video, narrated by Andie MacDowell, is a documentary of the past and present condition of the coral reefs of the Florida Keys. It also describes the Florida Everglades and its connection to Florida Bay and the Keys. 2. Ocean Fisheries Case Study Series, 1998, produced by David Conovor, Compass Light Documentary, Mainewatch Institute, and Island Institute, and distributed by The Video Project (www.videoproject.com) This three-video set examines Maine fisheries that illustrate worldwide resource management issues. The set includes Underwater Out of Sight: An Ecosystem Case Study; A Tale of Two Fisheries; and Managing for the Future: Tragedy of the Commons Revisited. 3. Coral Reef Adventure, 2003, video produced and distributed by MacGillivray Freeman Films (www.coralfilm.com) This IMAX film follows two divers as they explore reefs of the South Pacific, documenting problems with overfishing, sedimentation, and coral bleaching. 4. Secrets of the Ocean Realm, 1998, produced by PBS Video and available from Amazon.com (www.amazon.com) This five-tape set explores the behavior of deep-sea creatures and includes Cathedral in the Sea; Survival in the Sea; Venom; Creatures of the Darkness; The Great Whales; Sharks; City in the Sea; Star Gardens; Mountain in the Sea; and Filming Secrets. 5. Ocean Wilds, 2001, produced by Feodor Pitcairn and available from PBS (www.shoppbs.com) This five-tape set explores the behavior of sea creatures and includes Realm of the Killer Whales; Creatures of Coral; Sperm Whale Oasis; Gathering of Giants; and Oases in the Sea. Weighing the Issues: Facts to Consider Why Understand Ocean Currents? IG-240 Facts to consider: Knowing where ocean currents flow helps scientists and other planners determine optimal locations and boundaries for marine reserves. If reserve boundaries take advantage of currents, then it is more likely the reserves will receive significant numbers of larvae from diverse species, allowing the young of important species to settle and grow. A healthy reserve supports increasing population density and diversity both within the reserve and in surrounding areas, benefiting not only the ecosystems themselves but also the fishing industry in that region. Ocean currents carry larvae of marine organisms as well as food supplies for these creatures, from biologically based detritus to plankton and marine plants. Currents also may carry undesirable material, including spilled oil, toxins, invasive species, and debris such as plastics. Thus, understanding ocean currents can help people control, treat, and prevent marine damage from such sources. It can also help fishing fleets locate fish populations, and guide these fleets as well as other oceangoing vessels to travel most efficiently on the ocean by working with the natural routes of surface currents. Knowledge of currents also helps people investigate marine ecosystems, plan and protect coastline areas, and enjoy ocean-based recreation. The Coral Crisis Facts to consider: New technologies may enhance coral growth and reefinhabiting organisms. But the rate of coral destruction may be too fast for such methods to halt the decline of coral reefs overall, particularly because the damage is occurring now while these methods are in their early stages of development. Also, to the extent that coral reef problems have been exacerbated by the warming of the oceans through global climate change, new technologies may not be able to compensate adequately for the scope of the effect of the warming. Taking certain actions that are currently available would have a much greater impact at a much faster rate. Avoiding trawling in coral reef areas would prevent the reefs’ destruction at rates much greater than they can regrow, though such a restriction would face opposition from some fishing interests. Reducing the amount of artificial pollutants in ocean waters may reduce coral loss, but the connection between pollutants and damage to coral has not yet been definitively proven, with the sources of such pollutants being difficult to identify. Efforts that retard global climate change could help coral reefs, but such changes are large in scale, controversial, and slow to take effect. Forbidding the use of cyanide to catch fish would also help, though collectors, communities engaged in this method of fishing, and representatives from developing nations might argue against the economic burden imposed on those who currently use this method. Preservation on Land and at Sea Facts to consider: This question requires an individual response. As land animals, humans are more likely to notice changes in land ecosystems than in marine ecosystems because we can actually see the land systems, while it is IG-241 more challenging for us to observe the oceans, especially deep-water ecosystems. For most of human existence, people’s sense of marine ecosystem health has been gauged in terms of the abundance of food resources—as long as human beings have found new ways to harvest from the sea, the general sense has been that such resources are boundless. In addition, the oceans seem to absorb maltreatment without apparent harm, such as when untreated garbage and wastewater are dumped into offshore areas. Interestingly, our response to garbage and other waste being washed up on shorelines has been to dump the waste farther offshore, regardless of what may happen to deepwater ecosystems and of wherever the waste may travel when it encounters deep-water currents. The Science behind the Stories: Thinking Like a Scientist China’s Fisheries Data Observation: China’s marine fisheries catch increased dramatically in the 1990s while fisheries catch in many other countries declined. Given the overexploitation of its oceanic fisheries, China’s reported catch appeared suspiciously high. Hypothesis: China was systematically overreporting its total catch to the United Nations Food and Agricultural Organization, thus contributing to an overly optimistic view of the health of the world’s fisheries. Experiment: Reg Watson and Daniel Pauly, fisheries scientists at the University of British Columbia, developed a statistical model to predict catches based on oceanographic factors, species distributions, and fishing access. They then compared the predicted catch to each country’s reported catch. Results: For most regions, the reported catch was similar to the predicted catch. In China, however, the reported catch (10.1 million metric tons in 1999) was almost twice as large as the predicted catch (5.5 million metric tons). The finding suggests that the total global catch, rather than remaining stable through the 1990s, actually began to decline in the 1980s. Do Marine Reserves Work? Question: What effect do marine reserves have on fish populations in nearby areas? IG-242 Study: Callum Roberts and Julie Hawkins of York University conducted a 5year study of the Soufrière Marine Management Area (SMMA) and the surrounding areas on the island of St. Lucia. They conducted visual fish surveys and interviewed local fishermen. In addition, Roberts’s team, along with Darlene Johnson and James Bohnsack of NOAA, investigated fish migrations into and out of Merritt Island National Wildlife Refuge (MINWR) off Cape Canaveral, Florida, based on earlier findings from a fish population survey of the reserve by Johnson and Bohnsack. Fish migration was studied by analyzing trophy fish records from the International Game Fish Association. Results: In St. Lucia, Roberts’s team found that the biomass of five commercially important fish species had increased threefold inside the reserve and twofold outside the reserve within 3 years of establishment of the SMMA. The catch in fishers’ traps increased from 46% to 90%, depending on trap size. These data revealed that the reserve seemed to improve surrounding fisheries despite the expansion of the fishing grounds. Johnson and Bohnsack’s study of the MINWR obtained similar findings and included the supposition that the reserve’s fish appeared to be migrating to nearby commercial and recreational fishing areas. Analysis of trophy fish records showed that the number of trophy-sized fish caught in the Merritt Island area increased significantly after the establishment of the MINWR in 1962. Roberts’s team hypothesized that game fish grew to a larger size within the protection of the reserve and then migrated to nearby areas where they were caught by recreational fishers. While there is some criticism of the methods and conclusions of the study, Roberts, Hawkins, Johnson, Bohnsack, and their colleagues clearly showed that well-managed reserves are an effective tool in the establishment of sustainable fisheries. Causes and Consequences The following answers for the Causes and Consequences features are examples, and are not intended to represent a comprehensive list. In addition, the sequence of items is not meant to connote relative importance. Issue: Marine Pollution Causes: plastic debris, discarded nets, other trash oil spills runoff from land nutrient pollution Consequences: animals become entangled and die animals ingest plastic and die organisms become coated in oil and die red tides dead zones Solutions: IG-243 prevent dumping and littering; pick up trash from beaches properly dispose of oil and other pollutants to reduce runoff better farm practices and other measures to reduce nutrient runoff Unintended consequences: Picking up trash in itself has no effect on others' behavior. …and New solutions: Advertise cleanup efforts, exert peer pressure, create public campaigns InvestigateIt Case Studies and Videos Case Studies Plan Would Expand Ocean Fish Farming Tracking the Imperiled Bluefin From Ocean to Sushi Platter A Modern Peril: Living Near the Jaws of the Sea Scientists Warn Fewer Kinds of Fish Are Swimming the Oceans British Scientists Say Carbon Dioxide Is Turning the Oceans Acidic Lobster Boom And Bust In Europe, High-Tech Flood Control, With Nature's Help Saving a Reef for the Fish, And the People In Sri Lanka, Suffering and Hope 2 Recent Storms Show Forests Help Blunt Hurricanes' Force “Bringing the Ocean to the World,” in High-Def In Beach Enclave, Affluent Are Split Over Effluent Saving Coral Reefs Becomes a Tourism Priority Saving Coral Reefs Becomes a Tourism Priority Saving Coral Reefs Location Puerto Rico Topic Region Environmental Policy Global Commons Environmental Policy Bangladesh Land Use Global Commons Oceans Scotland Rhode Island Toxic Waste Oceans Netherlands Land Use Belize Conservation Sri Lanka Land Use Honduras Oceans Honduras Washington Oceans Washington Rincon Point, CA Oceans California Mesoamerican Reef Oceans Mexico Great Barrier Reef Coral Triangle Oceans Oceans Australia Indonesia IG-244 Becomes a Tourism Priority Videos Saving the Oceans: Pollution Hurting the Seas Obesity in America Location Pacific Ocean Topic Marine Resources Region Atlanta, GA Urbanization Georgia Answers to End-of-Chapter Questions Testing Your Comprehension 1. Approximately 71% of Earth’s surface is covered by ocean waters containing, on average, about 3.5% salt. Water temperature declines with depth, and density increases slightly at lower temperatures and higher salinities. Therefore, deep water tends to be colder, saltier, and denser than the surface water. 2. Ocean currents are driven by the prevailing wind currents at the surface, by gradients in water temperature, by gravity, and by the Coriolis effect. Surface currents move horizontally in large circulation patterns. Vertical currents (upwellings and downwellings) slowly mix the deep waters with the surface waters, affecting the distribution of nutrients and primary productivity. 3. Biologically productive areas are concentrated in areas of upwelling, in the shallower waters along continental margins, and at hydrothermal vents of the deep mid-ocean ridges. 4. Along the coasts there are kelp forests that shelter invertebrates, smaller fishes, seals, and top carnivores such as great white sharks. Coral reef communities, which include zooxanthellae, anemones, sponges, hydroids, tubeworms, molluscs, flatworms, starfish, urchins, and thousands of fish species, are among the most diverse and productive ecosystems on Earth. Intertidal ecosystems include rocky and sandy beaches, salt marshes, estuaries, and mangrove forests, which serve to buffer the land from the effects of storm surges and act as nursery areas for many marine organisms of economic importance, such as shrimp. 5. Coral reefs absorb wave energy and protect shorelines from damage, as well as providing essential habitat for many species. Increased water temperatures from global climate change, turbidity, nutrient influx (as from agricultural fertilizers in runoff), and toxic pollutants can all damage coral reef communities. Salt marshes and mangrove forests are often drained and converted to residential, commercial, recreational, or agricultural uses. 6. Examples include government policy regulating the shipping industry to cut down on oil spills; volunteer beach cleanups to pick up plastic trash and other non-biodegradable debris that can choke or injure organisms that ingest or become entangled in it; and policy and approaches to reduce overuse and runoff of excess nutrients that cause eutrophication, as with the Gulf of Mexico’s dead zone (Chapter 7). 7. Overfishing can remove the larger and fully mature fish faster than they are replaced by the population, thereby resulting in a decline in catch size and quality, and a decrease in the fish population because the death and export of IG-245 individuals exceeds birth and import. Some fishing techniques (bottom trawling, for instance) physically damage or destroy certain marine ecosystems. The collapse of North Atlantic cod fisheries is a prime example of overexploitation through trawling damage and direct fishing pressure. 8. Myers and Worm concluded that the oceans today contain only one-tenth of the large-bodied animals they once did, and that the loss (from industrialized fishing) happened so quickly in most places that scientists never knew the original abundance of these animals. 9. Commercial driftnetting catches and kills (by drowning) marine mammals and turtles, as well as many non-target fish species that die from exposure to air on ships’ decks. Similar by-catch problems exist with longline fishing, which hooks unwanted species as well as those desired, and even catches and kills marine birds. Bottom-trawling disturbs the seafloor and reefs, destroying habitat inhabited by many species. 10. Nearly all marine protected areas allow fishing or other extractive activities, whereas marine reserves do not permit such activities. Such marine reserves can serve as production areas for fish larvae that then disperse outside the reserve and stock other parts of the ocean. Interpreting Graphs and Data 1. Before the management plan, swordfish biomass was declining fairly rapidly. Beginning immediately after the plan, biomass rebounded. The opposite trends are apparent for fishing mortality: it rose before the plan and decreased after the plan. Overall, there is an inverse correlation between fishing mortality and biomass of the stock. 2. If trends continue, the swordfish stock should continue to increase. 3. The establishment of marine reserves (i.e., protected habitat) is vital for many species, although this is not always the case with large open-ocean fish such as swordfish unless the reserve is very large. For a species hunted for its meat like the swordfish, consumer seafood preferences may make at least as much difference; if people show concern for the species’ decline and reduce their consumption of swordfish, these purchasing choices will drive down the price of the fish and fishers will have less economic incentive to fish for them. Calculating Ecological Footprints Consumer group North America (21.6 kg per Annual consumption China (27.7 kg per IG-246 World (16.2 kg per You Your Class Your State The United States The World capita) capita) 21.6 kg Answers will vary Answers will vary 6.48 × 109 kg 27.7 kg Answers will vary Answers will vary 8.31 × 109 kg 16.2 kg Answers will vary Answers will vary 4.86 × 109 kg 1.77 × 1011 kg 1.04 × 1011 kg 1.38 × 1011 kg capita) 1. North American versus world fish consumption: 21.6 kg/16.2 kg = 1.33. North American vs. world ecological footprints: 3-nation average of 6.6 hectares/2.2 hectares = 3.00. With regards to fish consumption, North America is not as far above the world average as compared to our ecological footprint as a whole. This may be because of a greater popularity of seafood in many other cuisines around the world. We are, however, still 33% above the world average. 2. China’s large population already has an ecological footprint that exceeds the land area of its country. In order to feed that population, they must either import food from other countries, or harvest food from a common area that is part of no country (i.e., Earth’s oceans). 3. Answers will vary, but globally, fisheries are already suffering from overexploitation. The total human impact on those fisheries is the product of our population size and our per capita consumption rates, so if both are increasing, their product will increase even more quickly. The ecological consequences of such overexploitation may not be reversible, and numerous marine species could be driven to extinction. IG-247