Marine ecosystems of the world are made up of a wide variety ofplant and animal communities. Marine ecosystems are locatedmainly in coastal areas and in the open ocean. Organisms thatlive in coastal areas adapt to changes in water level and salinity.Organisms that live in the open ocean adapt to changes in tem-perature and the amount of sunlight and nutrients available.
Coastal WetlandsCoastal land areas that are covered by salt water for all or part ofthe time are known as coastal wetlands. Coastal wetlands providehabitat and nesting areas for many fish and wildlife. Coastal wet-lands also absorb excess rain, which protects areas from flooding,they filter out pollutants and sediments, and they provide recre-ational areas for boating, fishing, and hunting.
Estuaries Many coastal wetlands form in estuaries. An isan area in which fresh water from a river mixes with salt waterfrom the ocean. As the two bodies of water meet, currents formand cause mineral-rich mud and other nutrients to fall to the bot-tom. Figure 11 illustrates how the waters mix in such a way thatthe estuary becomes a nutrient trap. These nutrients then becomeavailable to producers, and in some shallow areas, marsh grasswill grow in the mud. Estuaries are very productive ecosystemsbecause they constantly receive fresh nutrients from the river andfrom the ocean. The surrounding land, such as the mainland or apeninsula, protects estuaries from the harsh force of ocean waves.
Plants and Animals of Estuaries For a week each spring, horse-shoe crabs, shown in Figure 12, crawl out of the ocean and ontothe beaches of Delaware Bay. In the shallow areas along theshore, the crabs mate and lay billions of eggs. Many migratingshorebirds depend on these eggs for food.
Estuaries support many marine organisms because estuariesreceive plenty of light for photosynthesis and plenty of nutrientsfor plants and animals. Rivers supply nutrients that have beenwashed from the land, and because the water is shallow, sunlightcan reach all the way to the bottom of the estuary. The light andnutrients support large populations of rooted plants as well asplankton. The plankton in turn provides food for larger animals,such as fish. Dolphins, manatees, seals, and other mammals oftenfeed on fish and plants in estuaries. Oysters, barnacles, and clamslive anchored to marsh grass or rocks and feed by filtering plank-ton out of the water. Organisms that live in estuaries are able totolerate variations in salinity because the salt content of the watervaries as fresh water and salt water mix when tides go in and out.
180 Chapter 7 Aquatic Ecosystems
Restoration of the Chesapeake Bay
The Chesapeake Bay is the largestestuary in the United States. Thebay produces large amounts ofseafood each year, supports manyspecies of wildlife, and providesrecreation for millions of people.
However, the ecosystems of thebay are threatened by several envi-ronmental problems. For example,pollution builds up because the tideflushes pollutants out of the bayvery slowly. Pollution builds upbecause only a very narrow openingjoins the bay and the ocean. By1980, the Chesapeake Bay wasseverely polluted with toxic indus-trial chemicals. Pesticides as well asexcess nutrients ran into the bayfrom housing developments, farms,and wastewater (including sewage).Marsh grasses and plankton weredying, and fish, oysters, and crabswere disappearing. Birds of prey,such as bald eagles, had almost
vanished. Therefore, fishers, envi-ronmentalists, and residents werealarmed and launched campaignsto save the bay.
Restoring Chesapeake Bayhabitats and water quality is noteasy. Maryland and Virginia, themain bordering states of the bay,have different environmental laws.Also, the bay’s watershed coversparts of four other states. Inter-ested groups would have to worktogether if they were to restore thebay. The Chesapeake Bay Programwas set up as a partnershipbetween the EnvironmentalProtection Agency, the District ofColumbia, Maryland, Pennsylvania,Virginia, and citizen advisorygroups. Goals included reducingchemical pollution, removing damsthat prevented fish from migrating,and reforesting river banks toreduce soil erosion.
� The Chesapeake Bay forms wherethe Potomac, Rappahannock, andother rivers meet the Atlantic Ocean.
Remarkable progress has beenmade in the last 20 years. Abouthalf of the wastewater flowing into
QuickLABEstuariesProcedure1. Place a few drops of red food
coloring in a test tube filledwith water.
2. In a separate test tube, addsalt water and a few drops ofyellow food coloring.
3. Gently place some of the freshwater solution on top of thesalt water solution.
Estuaries provide protected harbors, access to the ocean,and connection to a river. As a result, many of the world’smajor ports are built on estuaries. Of the 10 largest urbanareas in the world, 6 were built on estuaries. These 6 cities are Tokyo, New York, Shanghai, Buenos Aires, Rio de Janeiro,and Bombay.
Threats to Estuaries Estuaries that exist in populated areaswere often used as places to dump waste. Estuaries that arefilled with waste can be developed and used as building sites.This practice occurred extensively in California, which now hasplans to restore some of its estuary wetlands. The pollutantsthat damage estuaries are the same ones that pollute lakes,rivers, and the oceans: sewage, industrial waste containingtoxic chemicals, and agricultural runoff of soil containing pesti-cides and fertilizers. Most of these pollutants break down overtime, but estuaries cannot cope with the amounts produced bydense human populations.
Section 2 Marine Ecosystems 181
Figure 12 � Horseshoe crabs go tothe Delaware Bay, an estuarybetween New Jersey and Delaware,to lay their eggs.
the bay is now biologically treatedto remove pollutants and excessnutrients. Bald eagles are back, andindustry has reduced the chemicalpollutants released into the bay bynearly 70 percent. Planting treeshas restored forested buffers toabout 60 percent of the river banks,and populations of fish, such asstriped bass, are increasing.
However, the number of peoplein the bay area is increasing and thenumber of miles these people drive
drive, trying to conserve electricityand water, planting native vegeta-tion, using only a small amount offertilizer or water on your lawn orgarden, and properly disposing ofhazardous wastes such as motor oil,antifreeze, and cleaning fluids. Youcan help by picking up trash thatothers leave behind. You can alsojoin a citizens group to help pre-serve estuaries.
each year has increased even faster.In the last 30 years, miles traveledby vehicles increased four times asfast as the population. This has ledto runoff from streets and lawnsand pollution from vehicle exhaust,all of which harm the bay. The oys-ter harvest has decreased and theforested part of the bay’s watershedis still decreasing.
You can help save your localwatershed in the following ways: byreducing the number of miles you
� This great egret lives in one of the estuaries that borders theChesapeake Bay.
CRITICAL THINKING
1. Predicting Consequences Ifthe Chesapeake Bay Program hadnever been founded, what mighthave happened to the ChesapeakeBay? Explain how one organismmay have been affected.
2. Identifying RelationshipsHow may the use of less fertilizer onplants and lawns help the Chesa-peake Bay and other estuaries?
Salt Marshes Marsh grasses dominate much ofthe shoreline of the Gulf of Mexico and theAtlantic Coast of the United States. These
develop in estuaries where riversdeposit their load of mineral-rich mud. Here,thousands of acres of salt marsh support a com-munity of clams, fish, and aquatic birds. Themarsh also acts as a nursery in which manyspecies of shrimps, crabs, and fishes find protec-tion when they are small. As they grow to matu-rity and migrate to the sea, they are eaten bylarger fish or caught by commercial fisheries. Saltmarshes, like other wetlands, absorb pollutantsand protect inland areas.
Mangrove Swamps Swamps located along coastalareas of tropical and subtropical zones are called
Plants called mangrove treesdominate mangrove swamps. Mangrove trees,such as those shown in Figure 13, grow partlysubmerged in the warm, shallow, and protected
salt water of mangrove swamps. The swamps help protect thecoastline from erosion and reduce the damage from storms. Theyprovide the breeding and feeding grounds for about 2,000 animalspecies. Like salt marshes, mangrove swamps have been filledwith waste and destroyed in many parts of the world.
Rocky and Sandy Shores Rocky shores have many more plantsand animals than sandy shores do. The rocks provide anchoragefor seaweed and the many animals that live on them, such as seaanemones, mussels, and sponges. Sandy shores dry out when thetide goes out, and many of the tiny organisms that live betweenthe sand grains eat the plankton that are stranded on the sand.These organisms are the main food for a number of shorebirds.
such as the one in Figure 14, typically run paral-lel to the shore. These long, thin islands help protect the main-land and the coastal wetlands.
Barrier islands,
mangrove swamps.
marshessalt
182 Chapter 7
Figure 13 � Mangrove swamps arefound along warm, tropical coastsand are dominated by salt-tolerantmangrove trees.
Figure 14 � This barrier island islocated off the coast of Long Island,New York. Barrier islands are sepa-rated from the mainland and helpprotect the shore of the mainlandfrom erosion.
EcofactMangrove Swamps Mangrovescover 180 billion square meters oftropical coastlines around theworld. The largest single mangroveswamp is 5.7 billion square meters,located in the Sundarbans ofBangladesh. This single mangroveswamp provides habitat for theBengal tiger and helps supplyapproximately 300,000 peoplewith food, fuel, building materials,and medicines.
Coral Reefsare limestone ridges built by tiny coral animals called
coral polyps. Coral polyps secrete skeletons of limestone (calciumcarbonate), which slowly accumulate and form coral reefs.Thousands of species of plants and animals live in thecracks and crevices of coral reefs, which makescoral reefs among the most diverse ecosystemson Earth.
Corals live only in clear and warm saltwater where there is enough light for photo-synthesis, so coral reefs are found in shallow,tropical seas, as shown in Figure 15. Only theouter layer of a reef contains living corals,which build their rock homes with the help ofphotosynthetic algae. Corals, such as thoseshown in Figure 16, are predators that never chasetheir prey. They use stinging tentacles to capturesmall animals, such as zooplankton, that float or swimclose to the reef. Because of their convoluted shape, reefs providehabitats for a magnificent variety of tropical fish, and for snails,clams, and sponges.
Disappearing Coral Reefs Coral reefs are productive but fragileecosystems. An estimated 27 percent of the coral reefs in theworld are in danger of destruction from human activities. If thewater surrounding a reef is too hot or too cold or if fresh waterdrains into the water surrounding a reef, the corals may die. Ifthe water is too muddy, polluted, or too high in nutrients, thealgae that live within the corals will either die or grow out ofcontrol. If the algae grows out of control, it may kill the corals.
Oil spills, sewage, pesticide, and silt runoff have been linkedto coral-reef destruction. Furthermore, overfishing can devastatefish populations and upset the balance of a reef’s ecosystem.Because coral reefs grow slowly, a reef may not be able to repairitself after chunks of coral are destroyed by careless divers, fish-eries, shipwrecks, ships dropping anchor, or people breaking offpieces of it for decorative items or building materials.
Coral reefs
Section 2 Marine Ecosystems 183
Figure 16 � Coral reefs (bottom) arelimestone ridges built by tiny coralanimals. Coral animals have coraltentacles (top) that emerge from pro-tective structures to capture food.
Figure 15 � Coral reefs are found inwarm, shallow waters, where there isenough light for photosynthesis.Coral reefs support a great diversityof species.
OceansBecause water absorbs light, sunlight that is usable by plants forphotosynthesis penetrates only about 100 m (330 ft) into theocean before all of the sunlight is absorbed. As a result, much ofthe ocean’s life is concentrated in the shallow, coastal waters.Here, sunlight penetrates to the bottom and rivers wash nutrientsfrom the land. Seaweed and algae grow anchored to rocks, andphytoplankton drift on the surface. Invertebrates and fish thatfeed on these plants are also concentrated near the shore.
Plants and Animals of Oceans In the open ocean, phytoplanktongrow only in areas where there is enough light and nutrients. Asa result, the open ocean is one of the least productive of allecosystems. Phytoplankton have buoyancy devices, such as whip-like flagella, that prevent them from sinking into deep water,which is too dark for photosynthesis. The sea’s smallest herbi-vores are the zooplankton, which live near the surface with thephytoplankton they eat. The zooplankton include jellyfish, tinyshrimp, and the larvae of fish and bottom-dwelling animals, suchas oysters and lobsters. Fish feed on the plankton as do marinemammals such as whales.
The depths of the ocean are perpetually dark, so most food atthe ocean floor consists of dead organisms that fall from the sur-face. Decomposers, filter feeders, and the organisms that eat themlive in the deep areas of the ocean. Figure 17 illustrates the typesof organisms that may be found in the layers of the ocean at various depths, depending on available sunlight.
Figure 17 � The amount of sunlightavailable determines which organismscan live in each layer of the ocean.
FIELD ACTIVITY FIELD ACTIVITY Make a Miniature AquaticEcosystem Make your ownaquarium by collecting organismsfrom an aquatic ecosystem nearyour home or school. Be sure tocollect some water from theaquatic ecosystem. Bring yourcollection back to school and setup an aquarium. If necessary,research the Internet to find outthe special care that your ecosys-tem may require. Examine a fewdrops of your collected waterunder the microscope. Be sure tolook for algae or other forms oflife. Record and draw your obser-vations in your EcoLog. Observeand record the changes you seein your aquarium over the next 3weeks. What conditions areneeded to keep your miniatureecosystem healthy?
Threats to the Oceans Although oceans arehuge, they are steadily becoming more polluted.Most ocean pollution arises from activities onland. For example, plant nutrients washing offthe land as runoff from fertilized fields maycause algal blooms, some of which are poison-ous. Industrial waste and sewage dischargedinto rivers is the biggest source of coastal pollu-tion in the United States.
Overfishing and certain fishing methods arealso destroying some fish populations. Immensetrawl nets can entangle organisms that arelarger than the net holes. Marine mammals suchas dolphins, which must breathe air, can drownin the nets. Although it is against the law, someships discard fishing lines into the ocean, wherethey can strangle and kill fish and seals. The sea lion in Figure 18 was strangled by a net off the coast of California.
Arctic and Antarctic Ecosystems The arctic ecosystems at theNorth and South Poles depend on marine ecosystems becausenearly all the food comes from the ocean.
The Arctic Ocean is rich in nutrients from the surroundinglandmasses, and it supports large populations of plankton whichfeed a rich diversity of fish in the open water and under the ice.The fish are food for ocean birds, whales, and seals. Belugawhales, shown in Figure 19, feed on nearly 100 different arcticorganisms. Fish and seals also provide food for polar bearsand people on land.
The Antarctic is the only continent never colonized byhumans. It is governed by an international commission and isused mainly for research. Even during the summer, only a fewplants grow at the rocky edges of the continent. As in theArctic, plankton form the basis of the Antarctic food web. Theplankton nourish large numbers of fish, whales, and birds suchas penguins, which cannot fly because their wings have evolvedfor swimming.
Section 2 Marine Ecosystems 185
1. Explain why estuaries are very productive ecosys-tems. Why are estuaries vulnerable to the effects ofpollution?
2. Compare salt marshes with mangrove swamps.
3. Describe two factors that can damage coral reefs.
4. List two ways in which animals of the oceans arethreatened.
CRITICAL THINKING5. Predicting Consequences Suppose the sea level
were suddenly to rise by 100 m. What would happento the world’s coral reefs? Explain.
6. Analyzing Processes Read the description of estu-aries in this section and explain why cities are oftenbuilt on estuaries. How would building a city on anestuary affect the plants and animals living in an estuary? READING SKILLS
Main Ideas� Aquatic ecosystems can be classified as fresh-water ecosystems or marine ecosystems. Theplants and animals in aquatic ecosystems areadapted to specific environmental conditions.
� Freshwater ecosystems include lakes, ponds,freshwater wetlands, rivers, and streams. Thetypes of freshwater ecosystems are classified bythe depth of the water, the speed of the waterflow, and the availability of minerals, sunlight,and oxygen.
� Freshwater wetlands serve many functionswithin ecosystems. They trap and filter sedi-ments and pollutants; reduce the likelihood ofa flood; and buffer shorelines against erosion.
estuary, 179salt marsh, 182mangrove swamp,
182barrier island, 182coral reef, 183
� Marine ecosystems are identified by the pres-ence of salt water and include coastal wetlands,coral reefs, oceans, and polar ecosystems.
� Estuaries are among the most productive ofecosystems because they constantly receivefresh nutrients from a river and from an ocean.Estuaries provide habitat for a multitude ofplants and animals.
� Coral reefs are susceptible to destructionbecause they must remain at tropical tem-peratures and they must receive a large amountof sunlight. Coral reefs provide habitat forapproximately one-fourth of all marine organisms.
� Almost every person has an impact onaquatic ecosystems. Through understandinghow we affect aquatic ecosystems, we canreduce the negative effects we haveon them.
For each pair of terms, explain how the meaningsof the terms differ.
6. littoral zone and benthic zone7. plankton and nekton8. salt marsh and barrier island9. wetland and coral reef
Understanding Key Ideas10. Wetlands are important to fisheries in the
United States becausea. wetlands are the easiest place to catch fish.b. wetlands are the breeding grounds for
insects that are eaten by fish.c. wetlands provide the most desirable species
of fishes.d. many of the fish caught each year use wet-
lands for feeding and spawning.11. Animals that live in estuaries
a. tend to produce few offspring.b. are usually found in unpolluted
environments.c. must be adapted to varying levels of salinity.d. are adapted to cold-water conditions.
12. Bacteria cause eutrophication in lakes con-taining large amounts of plant nutrients by a. feeding on decaying plants and animals.b. reducing oxygen dissolved in the water.c. Both (a) and (b)d. Neither (a) nor (b)
13. Arctic ecosystems are considered marineecosystems becausea. arctic ecosystems contain an enormous
amount of frozen sea water.b. arctic ecosystems are inhabited by few
organisms.c. sunlight is limited.d. phytoplankton form the basis of arctic
food webs.14. Which of the following statements does not
describe a function of wetlands?a. Wetlands buffer shorelines against erosion.b. Wetlands provide spawning grounds for
commercially important fish and shellfish.c. Wetlands filter pollutants.d. Wetlands make good hazardous waste
dumpsites.15. Tiny animals, called coral polyps, that
excrete limestone createa. barrier islands.b. coral reefs.c. swamps.d. salt marshes.
16. Mangrove trees growa. along the coasts of rivers.b. in freshwater wetlands.c. in tropical areas and in subtropical areas. d. in the benthic zones of lakes.
17. The Florida Evergladesa. is the largest freshwater marsh in the
United States.b. protects threatened and endangered
wildlife.c. provides habitat for migratory birds.d. All of the above
18. Which of the following actions is an exampleof how humans affect wetlands?a. draining a wetland to create farmlandb. clearing a wetland to build a housing
developmentc. using a wetland as a landfilld. all of the above
C H A P T E R 7
Graph Skills Taking the following steps whenreading a graph will help you correctly interpretthe information. Be sure to read the title so thatyou understand what the graph represents. If thegraph has axes, read the titles of both the x- andthe y-axis. Examine the range of values on boththe x- and the y-axis. Finally, examine the data onthe graph, reading them from left to right, and putinto words what you think the graph represents.
ReviewShort Answer19. How does the phrase “best of both worlds”
relate to an estuary?20. Explain the difference between the types of
organisms that make up these classes: plank-ton, nekton, and benthos.
21. List three functions of wetlands.22. Describe what happens when a lake is con-
sidered to be eutrophic.23. What type of vegetation dominates man-
grove swamps?
Interpreting GraphicsThe pie graph below shows the percentage ofcoral reefs at risk in the world. Use the pie graphto answer questions 24–26.24. If there is a total of 255,300 km2 of coral
reefs in the world, how many square kilo-meters of coral reefs are at a high risk ofbeing destroyed?
25. Where would you expect to find coral reefsthat are at a low risk of being destroyed?
26. Where would you expect to find coral reefsthat are at a high risk of being destroyed?
Concept Mapping27. Use the following terms to create a concept
Critical Thinking28. Analyzing Relationships Write a short para-
graph that explains the relationship betweenthe speed of a river and the oxygen contentof a river.
29. Determining Cause and Effect Explainwhat may happen if the use of fertilizer onfarms and lawns around an estuary is notcontrolled.
30. Making Comparisons Read the paragraphunder the heading “Threats to Estuaries” inthis chapter. How do these threats compare tothose described under the heading, “Threatsto the Oceans?”
31. Analyzing Relationships Explain why plant-ing trees along a riverbank might benefit ariver ecosystem.
Cross-Disciplinary Connection32. Demography Six out of 10 of the largest
urban areas were built on estuaries. Threeof these cities are Tokyo, New York, andRio de Janeiro. Research the populations ofeach of these cities, and predict what mayhappen if population numbers continue toincrease.
Portfolio Project33. Research a Local Aquatic Ecosystem Observe
an aquatic ecosystem near your school orhome. This ecosystem can be as simple as apond or stream or as complex as a lake orestuary. Observe the types of plants and ani-mals in the aquatic ecosystem. Record anyinteractions among these organisms that youobserve. When you have recorded all of yourdata and observations, write a one-pagereport on the aquatic ecosystem.
34. Analyzing Data The graph below illustratesthe percentage of freshwater fish species thatare threatened in specific countries. Whatpercentage of freshwater fish species arethreatened in country B? in country D?
35. Evaluating Data If the number of freshwaterfish species in country C totals 599 differentspecies, how many of these species arethreatened?
WRITING SKILLS
36. Communicating Main Ideas What effectdoes overfishing have on estuaries? Whateffect does overfishing have on oceans?
37. Writing from Research Research endan-gered marine mammals of ocean and polarecosystems. Write a one-page report on thefactors that have caused these mammals tobecome endangered.
A B C
CountryD E
Perc
enta
ge
thre
aten
ed
Threatened Freshwater Fish Species
0
5
10
15
20
25
30
35
40
Read the passage below, and then answerthe questions that follow.
In the United States during the last 200 years,over 99 percent of native prairies have beenreplaced with farmland or urban developmentand most of the old-growth forests have beencut. Loss of so many of these habitats hasresulted in losses of biodiversity.
A new discipline, called conservationbiology, seeks to identify and maintain natu-ral areas. In areas where human influence isgreater, such as agricultural areas, formerstrip mines, and drained wetlands, biologistsmay have to reverse major changes andreplace missing ecosystem components. Forexample, returning a strip-mined area tograssland may require contouring the landsurface, introducing bacteria to the soil,planting grass and shrub seedlings, and evenusing periodic fires to manage the growth ofvegetation. Restoring an area to its naturalstate is called restoration ecology.
1. Which of the following phrases describesa likely task of a restoration ecologist?a. raising funds needed to create a
national parkb. returning missing ecosystem compo-
nents to a drained wetland c. educating citizens about the need to
protect a local habitatd. both (a) and (b)
2. According to the passage, which of thefollowing statements is true?a. Former strip mines tend to have a high
level of biodiversity.b. A conservation biologist would most
likely oppose the development of areasaround the Grand Canyon.
c. Periodic fires in some ecosystems donot help manage excess growth ofvegetation.
d. Most prairie ecosystems located in theUnited States have been preserved.
Now that you have read the chapter, take amoment to review your answers to the ReadingWarm-Up questions in your EcoLog. If necessary,revise your answers.
Eutrophication: Too Much of a Good Thing?Plants depend on nutrients such as phosphates and nitrates tosurvive. However, when people release large amounts of thesenutrients into rivers and lakes, artificial eutrophication canoccur. In artificial eutrophication, nutrients cause algae andplant life to grow rapidly and then die off and decay. Whenmicroorganisms decompose the algae and plant matter, they useup oxygen in the water, which causes the death of fish and otheranimals that depend on oxygen for survival. Eutrophication iscommonly caused by phosphates, which are often found indetergents, and by nitrates, which are found in animal wastesand fertilizers. In this lab, you will observe artificial eutrophica-tion in an aquatic ecosystem.
Procedure1. Working with your team, use a wax pencil to label one jar
“Control,” a second jar “Fertilizer,” and a third jar“Excess fertilizer.”
2. Put 750 mL of distilled water in each of the three jars. Readthe label on the fertilizer container to determine the recom-mended dilution of fertilizer for watering plants. To the“Fertilizer” jar, add the amount of fertilizer recommendedfor a quart of water. To the “Excess fertilizer” jar, add 10times this amount of fertilizer. Stir the contents of each jarthoroughly to dissolve the fertilizer.
Objectives� Observe
the effects of nitrates and phos-phates on an aquatic ecosystem.
� Compare the growth of organismsin different levels of nutrients.
� Predict possible effects nitrates andphosphates would have on anaquatic ecosystem in your area.
Materialsdistilled watereyedropperfertilizer, household usefluorescent lampgraduated cylinderguide to pond life identificationjars, 1 qt (3)microscopemicroscope slides with coverslipsplastic wrappond water that contains viable
organismsstirring rodwax pencil
USING SCIENTIFIC METHODS
Skills Practice Lab: OBSERVATIONC H A P T E R 7
� Step 5 Observe a drop of pondwater under the microscope.
3. Obtain a sample of pond water. Stir itgently but thoroughly to ensure thatthe organisms in it are evenly distrib-uted. Measure 100 mL of pond waterinto each of the three jars.
4. Cover each jar loosely with plasticwrap. Place all three jars about 20cm from a fluorescent lamp. (Do notplace the jars in direct sunlight, asthis may cause them to heat up too much.)
5. Observe a drop of pond water fromyour sample, under the microscope.On a sheet of paper, draw at least fourdifferent organisms that you see.Determine whether the organisms arealgae (usually green) or consumers(usually able to move). Describe thetotal number and type of organismsthat you see.
6. Based on what you have learned about eutrophication, makea prediction about how the pond organisms will growin each of the three jars.
7. Observe the jars when you first set them up and atleast once every three days for the next 3 weeks.Make a data table to record the date, color,odor, and any other observations you makefor each jar.
8. When life-forms begin to be visible in thejars (probably after a week), use an eyedrop-per to remove a sample of organismsfrom each jar and observe the sampleunder the microscope. Record yourobservations.
9. At the end of your 3-week obser-vation period, again remove a sample from each jar andobserve it under the microscope.Draw at least four of the mostabundant organisms that yousee, and describe how the number and type of organismshave changed.
Analysis1. Describing Events After three weeks, which jar shows the
most abundant growth of algae? What may have caused thisgrowth?
2. Analyzing Data Did you observe any effects on organismsother than algae in the jar that had the most abundant algaegrowth? Explain.
Conclusions3. Applying Conclusions Did your observations match your
predictions? Explain.4. Drawing Conclusions How can artificial eutrophication be
prevented in natural water bodies?
1. Designing Experiments Modify the experiment by usinghousehold dishwashing detergent instead of household fertilizer. Are the results different?
2. Research and Communications Research the watershedsthat are located close to your area. How might activitiessuch as farming and building affect watersheds?
Extension
� Step 7 Record your observationsof the jars every 3 days for 3 weeks.
Use the maps of wetland loss in the United Statesto answer the questions below.
1. Using a Key Use the key to determine how manystates had a decrease in wetland distribution from 5 to 12 percent to 1 to 5 percent.
2. Analyzing Data Is there any state on the map ofwetland distribution in the 1980s that has the samepercentage of wetland distribution as it did in the1780s? If so, how many?
3. Analyzing Data Which states have had the great-est decrease in wetland distribution since the 1780s?
4. Making Inferences What might have causedFlorida’s and Louisiana’s wetlands to decrease in distribution?
5. Using a Key Use the key to determine how manystates had a decrease in wetland distribution from 25 to 50 percent to 12 to 25 percent.
6. Identifying Trends If these trends of wetland losscontinue, what might a map of wetland distributionof the United States look like circa 2040?
What Do You Think?What are the benefits to creat-ing artificial reefs? How aremost artificial reefs created?Are there any disadvantages tocreating artificial reefs? Explainwhy creating artificial reefsmay be helpful in aquaticecosystems other than theocean. Research the Internet tofind out if there are any artifi-cial reefs in your community.
Hundreds of years ago, peoplefound that the fishing is often goodover a sunken ship. The fishing isespecially good if the wreck is in aprotected area, where it will not bebroken up by heavy surf or coveredwith silt from a river.
The reason fishing is often goodunder these conditions is becausemany marine organisms, such asseaweed, corals, and oysters liveonly where they can attach to ahard surface in clear water. So, therocky shores of New England andof the West Coast support manymore species than sandy areas do.
The Formation of a ReefOrganisms that attach to a hardbottom attract other species andeventually form a reef community.When seaweed grows on a rock,snails and crustaceans that eat theseaweed will join the community,
as will sea anemones, which feed onthe eggs, larvae, and waste producedby other organisms. Corals may set-tle on the bottom and add their hardskeletons to the reef. Then, fisharrive to feed on the reef organismsand to reproduce in the cracks andcrevices of the reef that protect themfrom predators. If the reef is in a relatively calm area, it will become adiverse community that fishermenand scuba divers can enjoy.
In recent years, many communi-ties have created artificial reefs bysinking various objects in theocean. Barges full of broken upconcrete are a common choice. TheSan Diego Oceans Foundation sanka decommissioned Canadian war-ship to create an artificial reef offMission Beach, California. Thewarship was sunk to attract touristswho are recreational divers. A non-profit group is working to bring thedecommissioned USAF’s GeneralHoyt S. Vandenburg to Key West tobe sunk as a diving reef that willenhance the Florida Keys NationalMarine Sanctuary. A reef founda-
tion in Georgia produces objectscalled reef balls. Reef balls are hol-low, concrete balls that have holesin them. They have legs that“stick” out to prevent them fromrolling around on the ocean floor.The balls come in various sizes andcan be towed behind even a smallboat to where they will be sunk.Reef balls are used to provide addi-tional hard surfaces for restoringdamaged coral reefs as well as tocreate new fishing and diving reefs.
Safe Artificial ReefsSinking artificial reefs is not prob-lem free. Obviously, the reef mustbe deep enough so that it does notinterfere with the movement ofships. But we cannot be sure whatdepth of water the ships of thefuture will need or that shippingchannels will be in the same places.In addition, if the object is to attractdivers, any parts that might trap orentangle a diver must be removed.Also, the reef must not pollute thewater or fall apart and leave debrisdrifting in the sea. In the case ofships that are used to create artifi-cial reefs, stripping out all the haz-ardous materials, such as plastics,insulation, and oil, is necessary.
� The gun turret (below) and theaircraft (left) are examples of objectsused to create artificial reefs.
