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Life of bays supplement Document Transcript

  • 1. Encounters in Excellence presentsLIFE OF THE BAYSA film lecure by Richard KernPresented at your school on: ___________sponsored by The Batchelor Foundation A Supplement for Teachers
  • 2. Life of the Bays The following supplement will clarify and provide depth to subjects focused upon in “Life of the Bays.” If these materials can be taught in the classroom a few days prior to the students seeing the film, the students will gain more from the presentation. Introduction In discussions of the major ecosystems of South Florida, the Everglades steals much of the spotlight. However, Florida Bay, Biscayne Bay and the Florida Keys are equally fascinating and equally important when considering the overall environmental health of our region. They face many of the same problems including pollution,redirected water flow and exotic invasive species that are contributing to their deterioration. In the movie LIFE OF THE BAYS the relationship of the various habitats found in the bays and keys will be explored. Attention will be given to many of the fascinating life-forms that reside there, as well as the impact human beings have on their future. Habitats 1. Florida’s CORAL REEFS can be found to the east and south of the Florida Keys just beyond the sea grass communities. Tiny sea animals called coral polyps build these reefs by secreting calcium carbonate, creating stony skeletons one upon the other over many years. Corals are ancient, the first known corals appearing over 500 million years ago. We get a sense of how the geology and climate of the earth has shifted over time when we realize that most of the Florida Keys are built upon exposed, ancient coral reefs. In and around the reefs live a large variety of beautiful tropical fish, as well as colorful sponges and exotic soft corals (sea whips, sea rods and sea fans, also called gorgonians), sea anemones, marine worms and a host of other interesting creatures. Many of these creatures have, over time, adapted uniquely to the complex landscape of the reef in order to survive. The balloonfish, for example has adapted the defensive ability to inflate its body, revealing dozens of spines. The green moray eel is an ambush predator that likes to hide in the crevasses of the coral reefs. It has a second set of jaws in the back of its throat to prevent prey from escaping its grip. In order for coral reefs to grow, several environmental factors are essential. Only in warm, shallow, and clear, and fairly calm waters will corals thrive. Therefore, the waters of South Florida are the only places off the continental U.S. coast where live coral reefs exist. (SC.7.E.6.4, SC.7.L.15.2) 2. The SEA GRASS community begins just beyond the shadow of the mangrove trees where the water is shallow enough for sunlight to penetrate and calm enough for the grasses to stay rooted. Three species of grasses grow here: Cuban shoal grass, manatee grass, and turtle grass- turtle grass being by far the most important. These beds of mostly turtle grass are considered to be the main nursery grounds for fish and invertebrates in American tropical water. Here in the grass beds juvenile fish grow and develop. As 1.
  • 3. adults they find their home largely on the coral reefs. Long, flat grass blades provide lots of surface area for attachment of filamentous algae plus many tiny invertebrates like hydroids, tunicates, and tube worms. Hosts of minute mollusks crawl on the blades, and so food supplies are plentiful for fish. Since the grass grows densely, it provides good cover from predators too. In addition to providing a structure for other marine life to grow and flourish, sea grasses are also a valuable food source for many important residents of the bay. Turtle grass constitutes the main diet of the green sea turtle, the West Indian manatee and the variegated sea urchin, which consumes more sea grass than either the turtle or the manatee. An important role played by sea grass communities near coral reefs is to strain out sediment drifting towards the ocean and help keep the water clear. As we learned earlier, clear water is important for the growth of corals. (SC.912.L.17.3) 3. The MANGROVE FRINGE, linking land and water environments, consists of 4 species of trees. On the land side are the buttonwoods and white mangroves. Closer to the water are the blackmangroves and lastly the most important species - the red mangrove - grows directly in the salt water. Two characteristics make mangrove trees uniquely suited for shoreline growth: they tolerate salt and they can survive, even flourish, in various levels of flooding and tidal surge. Mangroves are important in stabilizing the land. They also help to block the flow of salt water which helps to create estuaries which are transitional zones where fresh water from the inland mixes with salt water from the ocean, important feeding grounds for many species of wading birds. Mangroves also provide protection and nutrition for many species of young fish, shrimp and lobsters. The coral reefs, grass beds and mangrove fringe are linked together in a complex relationship that sustains all of the life of the bays. Mangroves are the link between land and sea. Their prop-roots create a buffer-zone that protects the mainland and the hardwood hammocks (another important ecosystem of the keys and coastal mainland) from storm winds. The erosive properties of water are monumental. The mangroves take root along the coast line and also help to prevent coastal erosion caused by the powerful tides and currents. The leaf of the red mangrove is the base of the food web for the bay ecosystem. The mangroves shed their leaves, which fall into the water and are broken down by bacteria and fungi. The resulting waste material washes out with the tides and currents to the sea grasses and coral reefs. The nutrients from the mangrove leaves are consumed by plankton which in turn feed tiny fish and invertebrates in the grass beds. (SC.6.E.6.1, SC.912.L.17.3, SC.912.L.17.9) 2.
  • 4. Life Cycle of the Coral Polyp Corals belong to the animal phylum Cnidaria. Cnidarians have radial symmetry with simple body cavities, and they all have stinging cells called nematocysts. Hydroids, jellyfish and sea anemones are other example of cnidarians. The reef building corals, sometimes called “hard corals” or “stony corals,” create a cup-shaped external skeleton which they build by secreting calcium carbonate. The soft body of the coral, called a polyp, can withdraw its many tentacles into the cup for protection. At night the tentacles are extended to catch plankton. Corals can reproduce sexually or asexually. In sexual reproduction sperm are released from the mouth of the body cavity into the sea where they may drift into the mouth of another polyp to fertilize the eggs there. This is called “broadcast spawning.” Later, the fertilized egg leaves through the mouth of the polyp and becomes a free-swimming larva called a “planula.” After swimming for several weeks, the planula attaches itself to a hard surface. At first just a small depression forms on the unattached end. Then tiny tentacles begin to pop up around this depression which soon becomes the body cavity of an adult polyp. When the polyp is completely formed, it then begins secreting its hard skeleton. There is an interesting relationship between most coral varieties and a type of alga called zooxanthellae. The single-celled algae actually live within the tissue of the coral polyp. The algae produce nutrients through photosynthesis which requires light. This is why clear, shallow water is important for coral growth. The corals use oxygen given off by the zooxanthellae as a by-product of photosynthesis. The algae also help in the building of the coral skeleton and in transporting certain nutrients within the coral polyp. This is an example of symbiotic mutualism, a relationship in which both organisms benefit. Zooxanthellae are also used by other forms of cnidarian life such as certain varieties of sea anemones and jellyfish, such as the cassiopea, which is also called the “upside-down jellyfish.” Corals are delicate creatures, and the landscape of the reef can shift dramatically with changes in climate. Coral bleaching can occur with a rapid shift in ocean temperatures. The shocked polyps expel the zooxanthellae from their tissues, which usually results in the death of the polyp. Oceanicacidification is the result of the rise of carbon dioxide levels in the sea. The oceans are important for absorbing carbon from the atmosphere and storing it. Too much acidity in the water, however, can cause the external calcium carbonate skeletons of the coral polyps to deteriorate. It is worth noting that gorgonians (soft corals), although growing on and adding much beauty to the reefs, differ from the stony, “reef-building” corals. They form flexible skeletons, and their polyp tentacles always number 8, with each tentacle often having tiny branches. Hard corals have smooth tentacles, numbering 6 or some multiple of 6, on each polyp. (SC.7.L.17.2, SC.912.L.17.4, SC912.E.7.9) Life Cycle of the Red Mangrove From the tiny yellow flower of the red mangrove tree grows a long, thin propagule. The propagule is not like a typical fruit. Instead, it is actually a young plant growing on the parent tree, sometimes for over a year. Like mammals, 3.
  • 5. mangroves are viviparous, meaning they produce live embryonic young instead of dormant seeds like most plants. When the propagule is ready to fall, it can be as much as 16 inches long. When it does fall, often it sinks into soft mud next to the parent tree and immediately begins to grow. Sometimes, however, the propagule floats away and is carried along for as much as a year with the course of the currents. Finally, one end of the propagule becomes waterlogged enough to pull the propagule into a vertical position. If the water in this new location is shallow enough and free from much turbulence, the new mangrove will sink into the soil below, sprout roots and leaves, and begin life, sometimes very far from where its journey began. (SC.912.L.17.3) Some Facts on the American Crocodile Although still listed as endangered, the American Crocodile has rebounded in recent years. There may be close to 2000 in South Florida now. They also live, but not abundantly, in other locations around the Caribbean, Central and South America. Still, the crocodile is far out-numbered by his close relative, the American Alligator, whose Florida population is estimated to be over one million. The narrower pointed snout is the most obvious difference between the crocodile and the alligator. The coloration of the crocodile is also slightly different, showing browner and more olive hues compared to the grays and blacks of the alligator. Crocodiles live in the brackish (salt mixed with fresh) waters of Biscayne and Florida Bays. Alligators prefer the fresh water of the Everglades, rivers and canals. Disappearing habitat is probably the biggest danger to the crocodile’s survival; therefore, in spite of recent increases, their future is still uncertain. Hypersalinity of the bays is also a stress factor. Although crocodiles have salt glands in their mouths for removing salt from the water, they can still dehydrate if the salt concentration is too high. Young crocodiles are particularly susceptible to dehydration. American crocodiles are primarily hole-nesters. An average of 40 three-inch, oval eggs are deposited in a hole dug in the beach sand. Approximately two months later the mother helps them hatch by digging them out and gently cracking the eggs and carrying the babies to the nearby water just as the alligator does. It is estimated that only one out of four of the young that hatch will survive to adulthood. Interestingly, in recent years successful nesting has occurred in the protected cooling canals of the Turkey Point Nuclear Power Plant in Homestead, Florida. It is now believed that 10% of the annual viable hatchlings are coming from the Turkey Point nests…a refreshing example of man’s potential to co-exist with nature in a positive way. (SC.912.L.17.12) The Life of the Bays As residents of South Florida, we have a close connection to the waters and life of our bays. The ocean connects us with much of the world. It supports our economy by encouraging trade, and tourism. We’re fed by its sea-life, and inspired by its beauty. As we continue to populate this area, however, we are competing more and more for land and resources. As our appetite for technology and material 4.
  • 6. spews carbon into our atmosphere. We are beginning to see the effects of carbon and greenhouse gasses on our environment, climate and weather patterns. Algae blooms (often due to pollution and runoff from the mainland) and turtle grass die-offs in both bays have brought about dramatic decreases in fish, shrimp and lobster populations, as have over-fishing. Off the keys, the delicate and slow growing coral reefs are suffering constant damage from bleaching, acidification and other stress-related diseases. Dragging anchors and careless divers also destroy the coral polyps, and propeller scars from speeding boats have caused serious damage to the sea grass beds. In fact, most of the environmental problems facing our bays can be directly or indirectly attributed to human pressure. Along with the key deer over a dozen species of plants and animals in the keys’ hammocks alone are threatened or endangered due to the spread of human population and infrastructure. These same factors have harmed the mangrove shorelines and beaches where the American Crocodile and several sea turtle species now fight for survival. In the waters offshore a lovable sea mammal, the West Indian Manatee, has made some small gains but still has a long struggle ahead. He is large, slow, and frequently surfaces for air which means he is poorly adapted to the hundreds of boats that cross our waters. Many manatees are struck and killed each year, their greatest threat. All is not lost, however, and there are efforts to mitigate and hopefully reverse some of the damage to these delicate ecosystems. Artificial reefs provide new homes for sea life while attracting recreational divers, taking some of the pressure off our coral reefs. Also, experimenting with methods to cultivate and transplant coral fragments and sea grasses may lead to revitalization of our reefs and grass beds. Technology has the possibility to develop and utilize new, clean methods of energy production, such as wind and solar. As individuals, we can take small steps to reduce our carbon footprint and to advocate for responsible and sustainable ways to live in and enjoy South Florida, while encouraging the health of our environment and protecting the life of the bays. (SC.7.E.6.6, SC.7.L.15.3,SC.912.L.17.15, SC.912.L.17.16, SC.912.L.17.17, SC.912.L.17.18, SC.912.E.6.6)goods rises, so does our need for energy. Much of this energy comes from burning fossil fuels, which Answers to Quiz (last page)1. b 6. F2. a,c,d 7. T3. b 8. T4. d 9. F5. c 10. F Suggested Websites: www.reefrelief.org www.biscayne.national-park.com 5.
  • 7. QuizMultiple choice1. What is considered to be the base of the food web for Florida Bay and Biscayne Bay? (a) shrimp larvae (b) mangrove leaves (c) fish eggs (d) turtle grass2. Name 3 conditions that ocean environments must have for coral reefs to grow well. (a) warm temperatures (b) higher than usual salinity (saltiness) (c) shallow water (d) clear water (e) deep water (f) fast currents3. New red mangrove trees start from….(a) sea cucumbers (b) propagules (c) prop roots (d) anemones (e) planula4. Coral reefs are made largely from….(a) tiny shells pressed together over many years (b) huge boulders upon which many sea plants have begun to grow (c) skeletons of coral shrimp (d) exoskeletons of tiny polyps5. Which species of animal consumes the most turtle grass? (a) West Indian manatee (b) lettuce sea slug (c) variegated sea urchin (d) green sea turtleTrue or False6. The American alligator has a narrower, more pointed snout than the American crocodile. ____7. A type of alga called zooxanthellae lives within the tissues of the coral polyp in an important symbiotic relationship. ____8. Coral reefs often protect sea grass beds from destructive strong currents. ____9. Under the prop roots of mangrove trees only two species of fish can survive. ____10. Where mangrove trees grow along a shoreline, loose sediment erodes away, and the shoreline recedes. ____ 6.