Aquatic EcosystemsProject Summary
Aquatic ecosystems are the most varied of all ecosystems, ranging from freshwater ponds to rivers, lakes, saltmarshes, coasts, mangroves and coral reefs to open ocean. Although a single type of ecosystem will be chosen for the project, it is hoped that the reports will be presented to the class to acquaint students with the characteristics of as many of these habitats as possible. The project will consist of selecting a particular type of aquatic ecosystem that is threatened in a geographical area listed below. This ecosystem, the threats to it--whether through pollution, damming, diversion or other activity--will be described, including its wildlife. Also certain aquatic species that are in sharp decline will be among the subjects listed for special attention. The ways in which this aquatic ecosystem, species or group of species is being conserved or destroyed will be a major focus.
The aquatic ecosystems of the world have never been more stressed and degraded. The rise in human population to more than 6 billion people by the end of the 20th century placed strains of overuse and pollution on the limited supplies of fresh water, leaving billions of people without adequate clean water supplies and creating rising tensions over water rights. In these conflicts, wildlife pays a high price, losing pristine habitat and becoming contaminated with toxic chemicals and oil spills that are killing wildlife around the world. Dams have endangered numerous fish by impeding their migrations, and developing countries have been damming their rivers at an increasing rate. Rivers that flowed swiftly become still ponds after damming, an alteration to which many fish cannot adjust. Many of these fish are also declining as a result of the introduction of non-native fish, which are out-competing them. The Nile Perch was introduced as a food fish in Lake Victoria, and it has virtually eliminated hundreds of species of native cichlid fish, colorful and ancient species. The Colorado River of the US west has many dams on it, which have totally altered the river's flow patterns and temperature, endangering many fish that had evolved in the swift-flowing, silt-laden water. The most dramatic example of a dam endangering a wide variety of plants and animals, and dislocating 1 million people, is the Three Gorges Dam being built on the Yangtze River of China. It will almost certainly result in the extinction of the Yangtze River Dolphin, a very ancient freshwater species, the Yangtze Sturgeon and numerous plants that will be inundated by the waters. Although far upstream, it will also have the effect of drying up wetlands downriver and at the delta. With inadequate provision for sewage treatment for the millions of people and industry living alongside the new lake formed by the dam, the Yangtze is expected to become extremely polluted. Large dams inundate vast areas, displacing thousands of people from their homes and drowning rare trees, plants and wildlife.
Diversion of rivers for agriculture or water supply has left many riverbeds and deltas dry, causing entire ecosystems to collapse. An increasing problem with rising temperatures has been violent storms which cause severe flooding of rivers, made worse by the deforestation that robs hillsides and riverbanks of protective trees that absorb rainfall throughout the year and hold the soil in place. Lakes and spring ponds that dry up in the summer are also being filled in by developers and government projects, eliminating habitat for myriad aquatic creatures, from frogs and salamanders to turtles and water birds.
Overfishing, pollution and destruction of ocean environments have reached crisis proportions, with 70 percent of all fish caught commercially in depleted status or worse, including some of the most ecologically important species--sharks, tuna and others at the top of their food chain. Toxic chemical pollution has increased, especially in colder waters, where whales and other cetaceans are dying from massive build-ups of chemicals such as PCBs (Polychlorinated Biphenyls), pesticides, heavy metals and other toxins. Along the pristine coast of Washington state, Killer Whales are dying from these toxic chemicals, as are white Beluga Whales in the St. Lawrence River. A Sperm Whale that died recently of toxic chemicals had to be disposed of as highly toxic waste. Other waste in the oceans is killing wildlife. Abandoned driftnets drown thousands of birds, seals, sea lions and sharks, and fishing line entangles endangered Northern Right Whales and other wildlife, drowning them. Plastic sheeting, balloons, plastic from six-packs and other trash are killing seabirds, such as the long-lived and declining albatross, which unknowingly feed this trash to their chicks, killing them, or swallow the items themselves, later dying of blocked intestines. Collisions with ships and motor boats are causing large numbers of deaths in Florida Manatees and whales.
Coral reefs, the most beautiful and biologically diverse ocean ecosystems, are dying from many threats. Dynamite and cyanide used to kill and capture fish destroy the entire reef. Overfishing, pollution and silt that washes off nearby lands from agriculture and development can combine to kill a reef. Global warming causes coral bleaching that is affecting a growing number of reefs. More than one-third of all coral reefs are now dead or dying.
Wetlands have declined in the United States by 50 percent. This has resulted in more destructive floods and losses in fisheries production. Wetlands filter pollutants, and their reduction has lowered water quality. Elsewhere in the world, similar declines have taken place. Both fresh and saltwater marshes provide important benefits in cleaning water through a natural filtration system. In fact, the worldwide value of this benefit to the Earth and human society has been calculated at $1.7 trillion. Marshes also provide important flood controls by absorbing large amounts of water from nearby sources or rainfall, as well as a multi-billion dollar benefit of serving as nurseries for fish, shellfish and other wildlife. Traditionally, however, they are filled in for development, airports, seaports and other commercial uses which are considered to be far more beneficial to society. It is important to reexamine such an approach, especially in view of the tremendous costs of flooding in human lives and property and the decline in fish and shellfish harvests.
An atmospheric phenomenon caused, apparently, by CFCs, or chlorofluorocarbons, chemicals used in refrigeration and for other industrial purposes, is thinning the ozone layer, a protective shield that filters the sun's rays
before they strike Earth. Large holes have developed over the Poles, especially the South Pole, allowing huge amounts of ultraviolet rays from the sun to enter the atmosphere, causing many cases of skin cancer in humans and having unforeseen effects on animals with sensitive skin like frogs and salamanders. Frog species are disappearing at a catastrophic rate, especially those that lay their eggs in the open, exposed to the ultraviolet rays of the sun. Frogs are also suffering grotesque birth defects, which may be caused by pesticides or virus outbreaks. Frogs’ decline may be a warning sign that serious problems exist in the aquatic ecosystems of the world that will soon begin to affect human beings.
o Read the Aquatic Ecosystems chapter, which describes many of these problems in detail and parts of the world where large numbers of animals and plants are endangered. The references cited will provide more information.
o Select a species of wildlife or plant that has become endangered as a result of the destruction of aquatic ecosystems or related activities. Describe its status, threats to its habitat and what--if anything--is being done to prevent its extinction.
o Select an aquatic area from the following list to study its wildlife and present status:
- United States’ Colorado River
- Florida's Everglades swamp
- Rivers and wetlands of the US East and Southeast
- Russia's Lake Baikal
- Central Asia's Aral Sea
- East Africa's Lake Victoria
- Southern Africa's Okavango Delta
- Brazil's Pantanal wetlands
- Amazon River and its dams
- China's Yangtze River
- Australia's Great Barrier Reef
- Mississippi River Delta and adjacent waters
All are described in the Aquatic Ecosystems chapter. See also Video and Books and Publications sections.
o The following wildlife has become endangered as a result of the destruction of these aquatic ecosystems or related activities. Select one and discuss threats, species involved and conservation programs:
- albatross and other large seabirds
- whales and dolphins
- sea turtles
o Select an aquatic animal or plant species that is threatened with extinction and write a short report about it, using the criteria in the project, "Profile of an Endangered Species." It can be a type of fish, frog, turtle, aquatic insect (such as a dragonfly), bird or mammal, for example. Write about the species in the context of its aquatic habitat, whether its habitat is being protected, and other threats to it, which may include pollution, trade or competition with exotic species. As source material, consult this book, Threatened Birds of the World, Walker's Mammals of the World and other references cited here or in the Books and Publications section of this book.
o Make comparisons between natural means of flood control, including marshes, beaver ponds and heavily forested stream and riversides, and artificial means, such as levees, dikes and canals. Water, A Natural History, listed below, is helpful in pointing out the differences. Compare the cost and success of natural means of controlling pollution, such as sewage through marshes that filter waste, and artificial means through sewage plants. Individual homes in suburban and rural areas use septic tanks and cesspools to store sewage. In times of heavy rain, however, they often overflow into rivers, as do urban sewage plants. In many parts of the world, no sewage treatment exists, causing rivers and waterways near cities to become severely polluted. Some cities in California and elsewhere have constructed artificial marshes to filter sewage water, creating, in the process, wildlife havens. New types of toilets, known as compost toilets, are another less-polluting innovation. Read Chapter 9, "Aqueducts and Toilet Bowls" in Water, A Natural History, and write a short report on improvements needed in the present systems.
o Grassroots organizations throughout the world have been successful in restoring rivers and other aquatic ecosystems. Using a book, such as How to Save a River. A Handbook for Citizen Action, select a river, wetland, pond (including beaver ponds), lake or vernal pool (temporary wetland that dries up in the summer) to help preserve or clean up from pollution. Small projects can be of importance in conservation. For example, some high school classes in the Midwest sampled a nearby marsh for the types of frogs found there and discovered that the majority were deformed, having five or more legs, misplaced eyes or other grotesque malformations. The situation was given publicity, and research began on the causes. Pesticide contamination was considered the most likely cause, since water from the marsh used to grow frogs in captivity produced similar deformities. One organization, The Riverlands Conservancy, has helped purchase river habitat in Oregon, Missouri and Washington totaling 17,174 acres since 1993. Measuring pollution in local waterways is an excellent class project that can lead to environmental action on the part of state or federal authorities. Save Our Streams program, run by The River Network, headquartered in Portland, Oregon, and its sister organization, The River Clearinghouse, provide information to activists throughout the country on an 800 "hot line," using a database of volunteer experts who provide advice. The River Watch Network has been instrumental in helping communities monitor water quality in order to restore and protect rivers. (See How to Save a River. A Handbook for Citizen Action for more information and other organizations, which include American Rivers, the International Rivers Network and Riverkeepers, working to preserve aquatic ecosystems.) Using these examples, propose a class project to help conserve a local aquatic ecosystem.
Books and Publications