During the twentieth century scientists came to appreciate the important role that the oceans play in maintaining the Earth's climate. The oceans determine weather and long-term climate changes. They can also cause widespread damage to human populations, destroying human lives and property. Scientists are also still discovering the incredible diversity of life forms within the ocean depths. The oceans are home to more than 80% of all the life forms found on earth. The many levels in the oceans' complex food chain interact by producing food and structures as habitat for other species, as well as consuming organic material and wastes. Primary producers, such as phytoplankton, seaweed, and algae, are eaten by small animals and fish, which in turn are eaten by larger fish. These in turn are eaten by birds, larger fish, and such mammals as seals and humans. Surface currents and deep currents mix the waters and move nutrients about, replenishing the food source for all marine life living at various depths, providing a bounteous food supply for all.
Origin of the Oceans
The terms "ocean" and "sea" are sometimes used interchangeably. Earth's oceans are the Pacific, Atlantic, Indian, Arctic, and Southern. Generally, seas are a portion of a larger ocean, although they may be partially or completely enclosed by land, such as the Mediterranean Sea, the Red Sea, and the Black Sea. There are about thirty-five seas in the world.
Oceanographers (scientists who study the oceans) believe that the oceans are some 500 million years old. They also think that both the atmosphere on Earth and the oceans were formed through a process called "degas-sing" of the Earth's deep interior. According to this theory, the ocean originated from the escape of water vapor from the melted rocks of the early Earth. The vapor rose to form clouds surrounding the cooling planet. After the Earth's temperature had cooled to a point below the boiling point of water, rain began to fall and continued falling for many centuries. As this water drained into the huge hollows of the planet's cracked surface, the ocean was formed. The force of gravity kept this water on Earth.
Oceans as Controller of Earth's Climate
Oceans play a major role in the Earth's weather and long-term climate change. The oceans have a huge capacity to store heat and can affect the concentration of atmospheric gases that control the planet's temperature. The top eight feet of the oceans holds as much heat as the entire atmosphere, making the oceans' ability to distribute heat a very important factor in climate changes. Changes such as unusually warm (El Niño) or cold currents (La Niña) in the eastern portion of the Pacific (the largest ocean) can disrupt global weather patterns.
The oceans play a crucial role in the cycle of carbon dioxide, a process affecting global warming. The world's oceans store some of the twenty-two billion tons of carbon dioxide added each year to the atmosphere by natural sources and the burning of fossil fuels. Some scientists believe that the oceans serve as a reservoir for about half of all the carbon dioxide emitted each year, while the other half accumulates in the atmosphere.
When Oceans Become Deadly
COASTAL POPULATIONS GROW.
Coastal areas are particularly vulnerable to natural hazards such as hurricanes, tidal waves, and their associated flooding. A December 2004 tsunami, triggered by a massive earthquake in the Indian Ocean, killed at least 200,000 people and caused massive damage in Indonesia, Sri Lanka, India, Thailand, and many small islands in the region. The true death toll from the tsunami may never be known, and the devastation was so overwhelming that it is difficult to attach a dollar figure to it.
This terrible catastrophe highlights the dangers inherent in living near the coast of a large body of water. In 2000 more than one-fifth of the world's population (more than one billion people) lived in coastal areas. This living preference places huge segments of the world population at risk from coastal hazards (episodic or chronic destructive natural system events that affect coastal areas), and has increased pollution of both oceans and estuaries.
Coastal areas are some of the fastest-growing parts of the United States. The National Oceanic and Atmospheric Administration (NOAA) reported that 54% of the U.S. population (occupying only 26% of the total land mass) lives in coastal counties. In the time period 1990–2000, seventeen of the fastest-growing counties in the United States were located along the coast and nineteen of the twenty most densely populated counties in the nation were coastal. The U.S. Census Bureau estimated that by 2010, 127 million people would live in coastal areas. According to Coastal Areas and Marine Resources (December 2001), a report from the National Coastal Assessment Group, by 2020 the coastal states of Florida, California, Texas, and Washington alone are expected to gain approximately eighteen million people.
According to "Thirty Years of Protecting Oceans and Coasts," a January 13, 2003, Environmental Protection Agency (EPA) press release, more than half of the United States population lives within fifty miles of the coasts. In addition, an estimated 180 million Americans visit United States coastal areas each year, spending more than $600 billion. One of every six jobs in the United States is marine-related, generating $54 billion in goods and services annually. Coastal waters provide diverse and biologically productive habitats, supporting 66% of all United States commercial and recreational fishing and 45% of all protected species.
DANGEROUS STORMS.
The most common coastal hazard is the threat of the huge ocean storms that come ashore, generally during the warmer months of the year, and cause devastating damage to property and human life. These storms go by different names in different parts of the world. They are called hurricanes or tropical storms in the North Atlantic, eastern North Pacific, and western South Pacific. "Typhoon" is the common term used for storms in the China Sea and western North Pacific, while "cyclone" is the word used for a storm in the Arabian Sea, the Bay of Bengal, and the South Indian Ocean.
Because of the spinning of planet Earth, a serious tropical storm's spiral is counterclockwise north of the equator and clockwise in the Southern Hemisphere. These tropical storms are the most dangerous weather phenomenon known, causing destruction through their very strong winds, torrential rains, and storm surges. By far the greatest damage and the most deaths are caused by the storm surges, the elevated mounds of water pushed by the high winds. Surges can reach twenty feet or higher. In an ocean storm, a surge rolls over everything in its path, and combined with the violent waves and water currents the surges cause not only death and destruction, but also immense erosion of land.
Coastal hazards such as hurricanes, tropical storms, and northeasters bring high winds, storm surges, flooding, and shoreline erosion, all of which are particularly damaging to coastal areas. They are not usually considered disastrous unless they involve damage to people and their property. Recent impacts have been increasingly devastating. Estimated disaster losses in the United States range from $10 billion to $50 billion annually; the average cost of a major storm is $500 million. One of the primary factors contributing to the rise in disaster losses is the increasing population in high-risk coastal areas. Table 6.1 and Table 6.2 show the most deadly and the most costly tropical cyclones or hurricanes that made landfall on the U.S. mainland between 1900 and 2004.
The most costly tropical cyclone during this period was hurricane Andrew, which devastated southeast Florida and southern Louisiana in 1992. Although the death toll was relatively low, at thirty-five lives, the cost of damage done approached $35 billion and the storm left some 250,000 people homeless. In the fall of 2004 Florida was hit by four strong hurricanes (Charley, Frances, Ivan, and Jeanne) in just six weeks. Damages from these storms were estimated to cost $41 billion. The cost of large hurricanes has been rising, but because of advances in storm prediction and preparation, the cost in lives has declined. Table 6.2 lists the most costly hurricanes to strike the U.S. mainland between 1900 and 2004, but not one of the top ten on that list is also among the ten most deadly storms during the same period. In fact, only one of the twenty-five costliest storms is also among the ten deadliest, an unnamed storm that struck New England in 1938.
With populations growing in coastal areas, eliminating the destruction associated with tropical storms will be almost impossible. However, accurate forecasting and storm preparation are of increasing importance in continuing to keep death tolls from such storms to a minimum.
TABLE 6.1
The ten deadliest tropical cyclones to strike the mainland since 1900
| Rank | Hurricane | Year | Category | Deaths |
| 1 | Unnamed (TX, Galveston) | 1900 | 4 | 8.000a |
| 2 | Unnamed (FL, Lake Okeechobee) | 1928 | 4 | 1.836 |
| 3 | Unnamed (FL, Keys) | 1919 | 4 | 600b |
| 4 | Unnamed (New England) | 1938 | 3c | 600 |
| 5 | Unnamed (FL, Keys) | 1935 | 5 | 408 |
| 6 | Audrey (Southwest LA, inland TX) | 1957 | 4 | 390 |
| 7 | Unnamed (Northeast) | 1944 | 3c | 390d |
| 8 | Unnamed (LA, Grand Isle) | 1909 | 4 | 350 |
| 9 | Unnamed (LA, New Orleans) | 1915 | 4 | 275 |
| 10 | Unnamed (TX, Galveston) | 1915 | 4 | 275 |
| Note: Hurricanes, or tropical cyclones, were not named until the 1950s. | ||||
| aThis figure could be as high as 10,000 to 12,000. | ||||
| bOver 500 lost on ships at sea, 600–900 estimated deaths. | ||||
| cMoving more than 30 miles per hour. | ||||
| dOf the total lost 344 were lost on ships at sea. | ||||
TRYING TO GUESS THE FUTURE.
Much research is targeted at understanding coastal storms so that their occurrences can be predicted and coastal residents warned. In addition to increasing the amount of property at risk, coastal population growth has created potentially life-threatening problems with storm warnings and evacuation. It has become increasingly difficult to ensure that the ever-rising numbers of residents and visitors can be evacuated and transported to adequate shelters during storm events. Sometimes hurricane evacuation decisions must be made well in advance of issuing hurricane warnings in order to mobilize the appropriate manpower and resources needed for the evacuation. Also, when a significant percentage of the coastal population has not experienced an event such as a hurricane, people are less likely to prepare and respond properly before, during, and after the event.
Why Is the Ocean So Salty?
The salinity (saltiness) of the ocean is the result of several ongoing natural processes. Salts are the end products of the naturally occurring reactions between acids and metals and metal-like substances in the environment. Early in the life of the planet, the oceans probably contained very little salt. However, since the first rains began descending on the young Earth many millions of years ago and ran over the land, breaking up rocks, absorbing and reacting with them to create dissolved solids (salts), and then transporting them to the oceans, the oceans have become progressively more salty. The activity of the hydrological cycle further concentrates the ocean salts.
TABLE 6.2
The billion dollar club: the costliest tropical cyclones to strike the mainland since 1900
| Rank | Hurricane | Year | Category | Damage |
| 1 | Andrew (Southeast FL and LA) | 1992 | 5a | $34,954,825,000 |
| 2 | Charley (FL, SC) | 2004 | 4 | 14,000,000,000 |
| 3 | Ivan (AL) | 2004 | 3 | 13,000,000,000 |
| 4 | Hugo (SC) | 1989 | 4 | 9,739,820,675 |
| 5 | Agnes (FL, Northeast U.S.) | 1972 | 1 | 8,602,500,000 |
| 6 | Betsy (Southeast FL and LA) | 1965 | 3 | 8,516,866,023 |
| 7 | Frances (FL) | 2004 | 2 | 8,000,000,000 |
| 8 | Camille (MS, Southeast LA, VA) | 1969 | 5 | 6,992,441,549 |
| 9 | Jeanne (FL) | 2004 | 3 | 6,000,000,000 |
| 10 | Diane (Northeast U.S.) | 1955 | 1 | 5,540,676,187 |
| 11 | Frederic (AL, MS) | 1979 | 3 | 4,965,327,332 |
| 12 | Floyd (Mid Atlantic & Northeast U.S.) | 1999 | 2 | 4,666,817,360 |
| 13 | Unnamed (New England) | 1938 | 3b | 4,748,580,000 |
| 14 | Fran (NC) | 1996 | 3 | 3,670,400,000 |
| 15 | Opal (Northwest FL, AL) | 1995 | 3 | 3,520,596,085 |
| 16 | Alicia (North TX) | 1983 | 3 | 3,421,660,182 |
| 17 | Carol (Northeast U.S.) | 1954 | 3b | 3,134,443,557 |
| 18 | Carla (North & Central TX) | 1961 | 4 | 2,550,580,095 |
| 19 | Georges (FL Keys, MS, AL) | 1998 | 2 | 2,494,800,000 |
| 20 | Juan (LA) | 1985 | 1 | 2,418,795,844 |
| 21 | Donna (FL, Eastern U.S.) | 1960 | 4 | 2,407,888,443 |
| 22 | Celia (South TX) | 1970 | 3 | 2,015,663,203 |
| 23 | Elena (MS, AL, Northwest FL) | 1985 | 3 | 2,015,663,203 |
| 24 | Bob (NC, Northeast U.S.) | 1991 | 2 | 2,004,635,258 |
| 25 | Hazel (SC, NC) | 1954 | 4b | 1,910,582,732 |
| 26 | Unnamed (FL, MS, AL) | 1926 | 4 | 1,738,042,353 |
| 27 | Unnamed (North TX) | 1915 | 4 | 1,544,253,659 |
| 28 | Dora (Northeast FL) | 1964 | 2 | 1,540,946,262 |
| 29 | Eloise (Northwest FL) | 1975 | 3 | 1,489,250,000 |
| 30 | Gloria (Eastern US) | 1985 | 3b | 1,451,277,506 |
| 31 | Unnamed (Northeast U.S.) | 1944 | 3b | 1,221,342,593 |
| 32 | Beulah (South TX) | 1967 | 3 | 1,113,122,363 |
| aReclassified as category 5 in 2002. | ||||
| bMoving more than 30 miles per hour. | ||||
(See Figure 6.1.) The sun's heat vaporizes almost pure freshwater from the surface of the sea, leaving the salts behind. Table 6.3 shows the principal constituents of ocean water.
The salinity of the ocean is currently about thirty-five pounds per thousand pounds of seawater, or parts per thousand (ppt). This is similar to having a teaspoon of salt added to a glass of drinking water. In contrast, freshwater has less than 0.5 ppt. Salinity in estuaries varies from slightly brackish (0.5 to 5 ppt) at the freshwater end to moderately brackish (5 to 18 ppt), to highly saline (25 to 30 ppt) near the ocean.
Scientists estimate that the rivers and streams flowing from the United States into the ocean discharge 225 million tons of dissolved solids (salts) and 513 million tons of suspended sediment into the ocean each year. Throughout the world, rivers annually transport about four billion tons of dissolved salts to the ocean. Nearly
FIGURE 6.1
Sources of salts in the ocean
TABLE 6.3
Principal constituents of seawater
| Chemical constituent | Content (parts per thousand) |
| Calcium (Ca) | 0.419 |
| Magnesium (Mg) | 1.304 |
| Sodium (Na) | 10.710 |
| Potassium (K) | 0.390 |
| Bicarbonate (HCO3) | 0.146 |
| Sulfate (SO4) | 2.690 |
| Chloride (Cl) | 19.350 |
| Bromide (Br) | 0.070 |
| Total dissolved solids (salinity) | 35.079 |
an equal amount of salt is deposited by the ocean as sediment on its floor.
If the salt in the ocean were taken out and spread evenly over the Earth's entire land surface, it would form a layer more than 500 feet thick—about the height of a forty-story building. (See Figure 6.2.) Throughout the world the salinity of seawater is similar, although it is somewhat lower in the nearshore coastal waters, the polar seas, and near the mouths of large rivers.
USING SALINITY IN FORECASTING.
According to a January 29, 2003, National Aeronautics and Space Administration (NASA) news release ("Ocean Surface Salinity Influences El Niño Forecasts"), NASA-sponsored scientists at the University of Maryland may have discovered how to improve the ability to predict El Niño events by knowing the salt content of the ocean's surface. Scientists have found that salinity and temperature combine to affect the density of the ocean. Greater salinity results in an increase in ocean density with a corresponding depression of the sea surface height. In warmer, fresher waters, the density is lower, causing an elevation of the sea surface.
FIGURE 6.2
The amount of salt in the ocean
The surface salinity in two regions contributes to El Niño events: an area of warmer temperatures and lower salinity in the western Pacific, and the higher salinity and cooler temperatures in the eastern Pacific. Differences in surface salinity are related to changes in temperature and upper ocean heat content, which are parts of the El Niño phenomenon. They have the potential to influence the Earth's climate through air-sea interaction at the ocean's surface.
According to the article, the study is among the first to look at ocean salinity in El Niño; Southern Oscillation predictions and their relationship to tropical sea surface temperatures, sea level, winds, and fresh water from rain. Researchers studied data about sea surface temperatures, winds, rainfall, evaporation, sea surface height, and latent heat, for the period from 1980 through 1995. Using computer models, they performed a series of statistical predictions of the El Niño events for the period. They found that short-term predictions only require monitoring sea surface temperatures, while predictions over a season require the observation of sea level changes. They concluded that observations of salinity significantly improve predictions. When changes in salinity occur, they affect the El Niño event for the next six to twelve months. During this lag time, salinity changes have the potential to modify the layers of the ocean and affect the heat content of the western Pacific Ocean, the region where the unusual atmospheric and oceanic behavior associated with El Niño first develops.
Researchers believe that the study will be of great significance for the NASA Aquarius mission to monitor the surface salinity of the global ocean. According to data available on one of NASA's Aquarius mission Web sites (http://science.hq.nasa.gov/missions/satellite_59.htm, January 3, 2005), this mission is scheduled for launch in 2008 and will have an operational life of three years. Aquarius will provide the first global maps of salt concentration on the oceans' surfaces. Salt concentration has been a key area of scientific uncertainty in the oceans' capacity to store and transport heat, which in turn affects earth's climate and water cycle.
Coral Reefs—A Special Ocean Habitat
Coral reefs are among the richest marine ecosystems in terms of beauty, species, productivity, biomass (the amount of living matter), and structural complexity. They are dependent on intricate interactions between coral, which provides the structural framework, and the organisms that live among the coral. Corals thrive by acting at many levels in the food chain as producers of structures and food, and as consumers of organic material. Coral reefs thrive in nutrient-poor habitats by containing many species that have complex food chains to recycle the essential nutrients with great efficiency, making the reefs particularly vulnerable to any event or process that disrupts the recycling.
Almost every group of marine organisms has its greatest number of individual kinds of organisms in coral reefs. For example, more than 25% of all marine fish are found on the reefs. Estimates of fish productivity suggest that around 10% to 15% of the total worldwide catch comes from reefs. Since reefs occupy only about 600,000 square kilometers (less than 0.02%) of the ocean surface, their productivity and biodiversity are much greater than other marine ecosystems.
Most reefs form as long narrow ribbons along the edge between shallow and deep waters, and their assets are many. Fisheries for food, income from tourism and recreation, materials for new medicines, and shoreline protection from coastal storms are among the many economic benefits they provide.
CORAL REEF STRUCTURE.
Corals are simple, bottom-dwelling organisms related to the sea anemone and jellyfish. The basic building block of coral is a polyp, a tiny animal that has a common opening used to take in food and excrete wastes, surrounding a ring of tentacles. The weak stinging cells of the tentacles are used to capture small animal plankton from the water for food. Each polyp sits in its own tiny bowl in a limestone skeleton, which the coral is constantly building as it grows up from the ocean floor. Reef-building corals live in large colonies formed by the repeated divisions of genetically identical polyps. The colonies can take a wide variety of shapes including branched, leafy, or massive forms, which may grow continuously for thousands of years.
The cells of coral contain symbiotic algae that make organic matter through photosynthesis and release it into the water to feed their coral hosts. Symbiosis is the living together of two dissimilar organisms in intimate association or even close union for mutual benefit. The algae remove carbon dioxide and excreted nutrients while supplying food and nutrients to the coral and greatly enhance the rate at which the corals deposit their skeletons. The coral cells provide the algae with protective structure and access to light and nutrients. The vast majority of coral skeletons are white; their color comes from the pigmentation of the algae living among the polyps.
Because of their dependence on symbiotic algae, coral reefs can grow only under conditions favoring the algae. Coral reefs are confined to tropical waters because the algae require warm, shallow, well-lit waters that are free of turbidity and pollution. Corals act like plants, taking up dissolved and particulate material from the surrounding water and overgrowing one another in competition for light.
CORAL REEFS—ECOSYSTEMS AT RISK.
The proximity of coral reefs to land makes them particularly vulnerable to the effects of human actions. Because they depend on light, coral reefs can be severely damaged by silt smothering, nutrient enrichment leading to overgrowth by seaweed, and other factors that reduce water clarity and quality. Sport diving and overfishing for food and the aquarium trade can deplete species and damage coral, resulting in disruption to the intricate interactions among reef species, as well as coral decline. Introduction of exotic species through human activity can be devastating as the new predators consume the living reefs.
Coral "bleaching" is the unique response of corals to stress. The coral loses the microscopic algae that normally live within its cells and provide the coral with their color, their ability to rapidly grow skeleton, and much of their food. The bleached coral turns pale, transparent, or unusual colors, and then starves as it is unable to feed or reproduce. Increased bleaching is an early warning sign of deteriorating health and can be caused by extremes of light, temperature, or salinity. In the 1980s coral bleaching began to spread dramatically. In October 1998 NOAA announced that it had recorded record-breaking coral bleaching in the tropics. Warm sea surface temperatures due to El Niño are believed to be the primary cause.
Little is known about most coral reefs and their inhabitants, but scientists have begun the extensive and exhaustive studies necessary to determine if coral reefs are in decline and the causes of decline. Of prime concern is confirming the direct and indirect effects of human activities on coral reefs and their denizens.
CORAL REEFS IN THE UNITED STATES.
Coral reefs are found in only three places in the United States: Florida (primarily in the Florida Keys), throughout the Hawaiian archipelago, and in the offshore Flower Gardens of Texas. The Florida reef system is part of the Caribbean reef system, the third-largest barrier-reef ecosystem in the world. Five U.S. territories—American Samoa, Guam, the Northern Mariana Islands, Puerto Rico, and the U.S. Virgin Islands—also have lush reef areas. According to the 2000 Water Quality Inventory published by the EPA, the northwestern Hawaiian Islands make up 69% of the country's coral reef areas, by far the largest percentage in the United States and its territories. (See Figure 6.3.)
To protect the U.S. coral reefs, many have been placed in marine sanctuaries with varying degrees of protection. The full extent and condition of most U.S. coral reefs is only beginning to be studied as a special area of focus.
On September 26, 2002, NOAA released the first national assessment of the condition of coral reefs in the United States. The report, The State of Coral Reef Ecosystems of the United States and Pacific Freely Associated States, was prepared under the auspices of the U.S. Coral Reef Task Force, and establishes a baseline that now will be used for biennial reports on the health of coral reefs in the United States. NOAA also released A National Coral Reef Strategy, a report to Congress outlining specific action to address thirteen major goals, including the continuation of mapping and monitoring, to protect coral reefs.
According to The State of Coral Reef Ecosystems of the United States and Pacific Freely Associated States, there are an estimated 7,607 miles of United States reefs and a range of 4,479 to 31,470 miles of reefs off the Freely Associated States. An estimated 27% of the world's shallow water coral reefs may already be beyond recovery, and about 66% are severely degraded. The report also indicates that in all areas some coral reefs in the United States were in good-to-excellent health. However, every reef system was suffering from both human and natural disturbances. These reefs suffer from the same problems as do reefs all over the world, especially those resulting from rapidly growing coastal populations. The report states that 10.5 million people now live in U.S. coastal areas adjacent to shallow coral reefs, and every year about forty-five million people visit the areas.
FIGURE 6.3
U.S. coral reef areas, 2000
Among the major causes of damage to coral reefs, according to the report, are human-induced pressures such as coastal pollution, coastal development and runoff, and destructive fishing practices. Ship groundings, diseases, changing climate, trade in coral and live reef species, alien species, marine debris, harmful tourist activity, and tropical storms also contribute to the damage.
Florida and the U.S. Caribbean were considered to be in the most unfavorable condition, mainly because of nearby dense populations and the effects of hurricanes, disease, overfishing, and a proliferation of algae. Live coral cover in the Florida Keys had declined 37% since 1997. Since 1982, white-band disease had killed nearly all the elkhorn and staghorn corals off the coasts of St. Croix (U.S. Virgin Islands), Puerto Rico, and southeast Florida.
Coral reefs are extremely important for a number of reasons. They are the Earth's largest biological structures. They are vital sources of food, jobs, chemicals, shoreline protection, and life-saving pharmaceuticals. Tourism in the United States and Freely Associated States coastal reef areas generated $17.6 billion in 2000. Commercial fishing generated an additional $246.9 million annually. In south Florida, reefs supported 44,500 jobs, providing a total annual income of $1.2 billion.
New and important discoveries about coral reefs continue to be made. According to Geoscience Australia, the Australian national agency for geoscience research and geospatial information, three previously uncharted coral reef patches were discovered in Queensland's Gulf of Carpentaria in mid-2003. The reefs cover about eighty square kilometers (30.8 square miles) at a mean depth of 28.6 meters (93.8 feet) beneath the water surface. The discovery of these reefs is significant in part because of commonly held scientific beliefs that no reefs could exist in the muddy waters of the southern Gulf of Carpentaria. In addition, according to a Geoscience Australia Web site describing the discovery (http://www.ga.gov.au/oceans/projects/smac_subreef4.jsp, August 3, 2004), "Sub-merged reefs may provide an important refuge for corals during the next few decades when near-surface reefs are threatened by widespread coral bleaching due to warmer global sea surface temperatures."
Nearshore Waters
Nearshore waters occur in lakes, estuaries, and oceans, and reflect the conditions and activities within the watershed. A watershed is an area in which water, sediments, and dissolved materials drain to a common outlet, such as a lake, river, estuary, or ocean. The near-shore is an indefinite zone extending outward from the shoreline, well beyond the shallow water (in oceans and estuaries, beyond the zone where the waves break). It defines the area where the current is caused primarily by wave action as opposed to a current that is the result of water flow. Depending on the size of the water body, the nearshore waters may be minimal in size (a small lake) or very large (the coastal waters of the Atlantic Ocean).
Whether marine, estuarine, or fresh, nearshore waters serve a variety of functions. They are the prime recreational waters, providing opportunities for swimming, boating, diving, surfing, snorkeling, and fishing. Near-shore waters are intimately linked with wetlands and sea grasses and provide a unique habitat for a variety of plants and animals. These waters are the source of food and shelter for many species of fish and shellfish and provide habitat for 80% of the fish species in the United States. Nearshore waters also provide numerous opportunities for education and research for students, naturalists, and scientists.
Because of their proximity to the shoreline, nearshore waters are particularly vulnerable to pollution. As a result, water quality in most confined waters and some nearshore waters is deteriorating, which in turn affects the plant and animal life. In addition to pollution, near-shore waters are very vulnerable to the everyday (and to all appearances, harmless) activities of people. For example, swimming has been restricted in some shallow lagoons with coral reefs and beautiful beaches, because heavy use by swimmers resulted in chemical concentrations of suntan oil and lotion in the water that was high enough to kill or impair the coral reefs. Wakes from recreational powerboats in high-use areas have been shown to increase wave action, resulting in increased shoreline erosion. Increased pollutant levels from boat paints, spills during refueling, and leaks of gas and oil from recreational boat engines in areas of high recreational use affect both plants and animals. Private pier and boathouse construction result in shading of water, which contributes to sea grass decline. Balancing the need to accommodate the public's desire to enjoy water-related activities and ownership of waterfront property and the need to protect nearshore waters is a difficult management issue.
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