The earth's axis of rotation wobbles like a spinning top. There are two periods (a wobble within a wobble): 19,000 AND 23,000 years. Precession has a profound effect on the earth's climate.
Throughout my research of various aquatic environments I came to understand that many students at the high school level do not have a basic understanding of this particular type of environment. For this reason, I have put together a teaching unit on aquatic environments. The unit will cover information, facts, figures, pictures, and examples of many types of aquatic environments on Earth. Students will participate in activities, labs, and discussions to gain a better understanding of the characteristics, global locations, adaptations, impacts and uses, threats, and conservation efforts in each habitat discussed in this teaching unit.
One of the habitats discussed in this teaching unit is an estuary. “An estuary is a partially enclosed body of water formed where freshwater from rivers and streams flows into the ocean, mixing with the salty sea water” (United States Environmental Protection Agency). Estuaries are protected by reefs, land, or barrier islands. This provides protection to the area within an estuary.
There are many different habitats found in an estuary. Examples of these habitats are freshwater and saltwater marshes, mangrove forests, and kelp beds. Many different organisms can be found here. The variety of plants and animals found in an estuary form a variety of different food webs.
Estuaries are beneficial because they provide an area where natural filtration of water occurs. Other uses of an estuary include recreation, cultural centers, and laboratories. Estuary environments provide economic benefits through tourism, fishing, and transportation areas (harbors) (United States Environmental Protection Agency).
Although estuaries provide a wealth of benefits to plants, animals, and people, estuaries are currently being threatened. Approximately half of the population of the United States alone lives in coastal areas. Stress on an estuary is increased by the number of people present, run-off containing toxic substances, and garbage entering the environment (Walker). Large conservation efforts have been made to protect the future of the estuary. Organizations such as the National Estuary Program (NEP) have strived to restore and protect the future of the estuary and the resources they provide.
A salt marsh is another aquatic environment in this unit. A salt marsh is a “transitional area between land and water, occurring along the intertidal shore of estuaries and sounds where salinity ranges from near ocean strength to near freshwater in upriver marshes” (South Carolina Department of Natural Resources).
In the United States alone, salt marshes can be found “from New Jersey to Northern Florida along the Atlantic Ocean rimming the Gulf of Mexico, and scattered along non-rocky stretches from Washington to San Diego” (www.botgard.ucla.edu). The areas close to the ocean are flooded by high tide daily. A salt marsh is divided into two main regions, low salt marsh and high salt marsh. The low salt marsh is found from the area of low tide to the area of high tide. The main plant found in the low salt marsh is cord grass (Spartina alterniflora). The high salt marsh ranges from the high tide line to the highest spring tide. In this area the plants are more terrestrial than aquatic. Examples of plants found in the high salt marsh are hay grass (Spartina patens), saltwort grass (Salicornia sp.), and spike grass (Districhlis spicata) (Pinet).
Salt marshes provide a protected area away from many predators where many organisms can grow and develop into adults. A salt marsh provides humans with areas for pelt hunting, fishing and other recreational activities. Salt marshes also help protect the inland land areas from natural disasters such as hurricanes.
The future of the salt marsh is being environmentally threatened by strong hurricanes and a rise in sea level. Humans are also intentionally and unintentionally threatening the salt marshes. Many marshes have been drained and filled for the planting of various crops, the building of homes and industrial buildings, and cleared to limit the insect population. Many marshes are impounded to control the water depth, salinity, nutrients, and gas levels. Pollution from many sources is another large threat to salt marshes, causing a decline in the productivity of salt marshes (Chabreck).
Some destruction to salt marshes has been minimized through federal and state laws. Permits may limit the amount of pollution from industry. Other actions that can be taken to minimize the threats to salt marshes include limiting the amount of run-off that enters the water cycle. Individuals can change some of their daily actions that do damage to the salt marshes, such as disposal of cleaners and other chemicals. Education students (and society) about salt marshes will raise awareness of the current threats to salt marshes and the resources they provide to humans and other organisms.
A third aquatic environment discussed in this teaching unit is a kelp forest. A kelp forest includes kelp and all of the organisms associated with kelp, such as mammals, fish, crabs, sea urchins, mollusks, and other algae. “Kelp forests are found on shallow rock shores in a mid-latitude band where light and various other ocean conditions are right” (Steneck and Graham).
Many kelp forests are currently being destroyed. Causes of the current decline in kelp forests include diseases, being eaten by organisms, and changes in the salinity and nutrient levels of the water. Toxins and other forms of pollution also contribute to the current destruction of the kelp forests. Another factor negatively impacting the kelp forest is the over harvesting and the lack of regulations concerning how kelp is harvested.
There are measures one can take to prevent the future loss of kelp forests. Limiting the amount and types of toxic substances used, support “environmentally-friendly” political leaders, and limiting the amount of fossil fuels used to help reduce the greenhouse effect. These small changes will help protect the environment of the kelp forests.
An additional aquatic environment many high school students do not understand a lot about is the mangrove swamp. A mangrove swamp is an area where “large woody, tree-like plants with exposed roots, called mangroves, dominate.” Mangroves are found in tropical areas suggesting the growth area is limited by the temperature of the air and water. Mangrove habitats are periodically covered with water during the day during high tide and uncovered at low tide (Hogarth).
The environment mangroves are found in caused the mangroves to adapt in order to survive. Mangroves have many types of arial roots to efficiently go through respiration. Mangroves cope with the high levels of salt by excreting the salt out of the plant. Salt is mainly eliminated through the leaves of the mangroves (Blaxland). Mangroves have also adapted to their environments through reproduction. “All mangroves disperse their offspring by water” and begin growing while sill on the parent plant (Hogarth).
Mangroves benefit humans by providing wood to burn for energy and used as building materials. Mangroves are also beneficial for the protection of nearby coastal areas from erosion. The benefits of mangroves are often unnoticed and altered for what is seen as a better use.
The altering of mangroves has threatened the environment. Water use and pollution cause severe damage to the mangroves. Natural damages such as typhoons or hurricanes can also cause severe damages. The clearing mangrove lands and creating shrimp farms is a current practice thought to bring in more money for the land owners at the expense of the health of the environment. This practice is actually very disastrous to mangroves and the environment.
Mangroves will have a future if students (and society) are educated about the overexploitation of the mangrove environment. Once students (and society) become more educated about the importance of mangroves they can be well maintained and saved for future generations.
A coral reef is the aquatic environment that many high school students have heard of, seen, or many even know a little about. A coral reef is “an organically constructed, wave-resistant structure created by carbonate-secreting animals and plants” (Pinet). Coral reefs are made of coral animals called polyps that use their tentacles to catch or string their food. There are microscopic algae found within the polyps called zooxanthellae that undergo photosynthesis and secrete carbonate to form the coral skeleton.
There are three types of corals. The first type is a fringing reef found extending from the shore into the sea. The second type is a barrier reef which is found several miles from the shore and forms a barrier between land and the sea. The third type of coral reef is an atoll. An atoll is ring shaped and is found in the open ocean (Gray).
Coral reefs are found in the Pacific, Atlantic, and the Indian Oceans. The reef is the home to up to twenty five percent of marine life and up to 2,500 species of coral (DeTemple).
Even though corals are often called one of the most beautiful things on Earth, humans are causing a large amount of harm to this natural wonder. Many coral reefs are loosing the algae inside the polyps and becoming bleached. Causes of coral bleaching include storms, sewage, waste, pollution, the large number of tourists, and cyanide fishing (Gray). Other threats to reefs include black band disease, grazing, global warming, and an increase in sediments and nutrients.
In order to save one of the most beautiful things on Earth, humans need to take action. The daily needs to people whose daily lives depend on the coral must change. Their needs must be met in different ways. Students (and society) need to be educated about the threats to the coral reefs and what is needed to reverse all of the damage currently being done to reefs around the world.
Through this high school teaching unit it is the hope that the students learn and gain a better understanding of each of the aquatic environments discussed. Through this education the students will understand the intentional and unintentional damage currently being done to these types of environments. Using the knowledge gained, students can make conservation efforts in hopes that these aquatic environments have a bright and strong future.
Blaxland, B. (2000). Water Worlds Mangroves. Australian Museum: Education Australia Pty Ltd.
Chabreck, R. (1988). Coastal Marshes Ecology and Wildlife Management. Minnesota: University of Minnesota Press.
DuTemple, L. (2000). Coral Reefs. California: Lucent Books, INC.
Gray, S. (2001). Coral Reefs. Minnesota: Compass Point Books.
Gogarth, P. (1999). The Biology of Mangroves. Oxford: Oxford University Press.
Mildred E. Mathias Botanical Garden. Coastal Salt Marsh. Retrieved June 1, 2004 from www.botgard.ucla.edu/html/botanytextbooks/worldvegetation/marinewetlands/saltmarsh/index.html
Pinet, R. (1998). Invitation to Oceanography. Massachusetts: Jones and Bartlett.
South Carolina Department of Natural Resources. (2004, June 8). Sea Science, Dynamics of the Salt Marsh. Retrieved June 1, 2004 from www.water.dnr.state.sc.us/marine/pub/seascience/dynamic.html
Steneck, R., M. Graham, B. Bourque, D. Corbett, J. Erlandson, J. Estes, and M. Tengner. (2002). Kelp forest ecosystems: biodiversity, stability, resilience, and future. Environmental Conservation, 29, 436-459.
United States Environmental Protection Agency. (2004, March 16). National Estuary Program. Retrieved June 1, 2004, from www.epa.gov
Walker, S. (2003). Life in an Estuary. Minnesota: Lerner Publication Co.
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