Coastal Vegetation Final

This topic submitted by Mary Keppler ( mlkeppler@hotmail.com) at 8:02 PM on 6/5/05.

The back of our truck was home on San Salvador in the Bahamas

Tropical Field Courses -Western Program-Miami University


Mary Keppler
GLG 413
June 4, 2005
Coastal Vegetation
Final Draft


Within the tropical regions of the Florida everglades and San Salvador, there exist several common species of plants that are remarkably abundant in an otherwise harsh environment. Temperature extremes and high salt concentration in the water are two factors that determine the species that can survive in coastal areas. Erosion along with human destruction threatens many of these plants and it is the role of concerned ecologists to understand these organisms before it is too late. There are many common species of coastal plants but eleven of these are guaranteed to be seen while on the trip, and these will be the focus of discussion.

The mangrove forests, which line the edge of several miles of coast throughout Florida, are comprised of mainly three species, commonly referred to as red, black, and white mangroves. Red mangroves, Rhizophora mangle (which is in the Rhizophoraceae family), grow along the water’s edge, closest to water and at the lowest elevation in comparison to black or white mangrove trees. Rhizophora mangle can be easily identified by its red tinted prop roots that rise above water level. These roots presented a formidable obstacle to conquerors and settlers alike. Higher upon the shore black mangrove trees can be found. Black mangroves, Avicennia germinans (which is in the Avicenniaceae family), can be quickly identified by the pneumatophores rising through the soil like little fingers. These projections provide oxygen exchange and stability in the sandy ground. Avicennia germinans can grow to a height of 14-20 meters and can tolerate greater fluxuations of salt content than Rhizophora mangle. The leaves of Avicennia germinans are usually covered with salt crystals. The salt on the leaves is a remnant of the process by which black mangroves remove salt from their systems. At even higher elevations, white mangroves grow. White mangroves, Laguncularia racemosa (Combretaceae family), live farthest from water and expel salt through two pores at the base of each leaf. Mangrove forests are indepensible in nature-especially in such a fragile ecosystem such as wetlands. Together these three species; Rhizophora mangle, Avicennia germinans, and Laguncularia racemosa, help to filter out dangerous chemicals coming from agricultural runoff and catch loose sediment-helping to curb erosion. Without mangrove tracts whole islands would be lost to erosion and chemicals would further pollute the ocean. Shrimp farmers and developers who see the trees as nothing but a nuisance threaten mangrove forests. The consequences of this destruction are not yet determined but already small islands are disappearing and areas of reef are suffering from the increase in chemical runoff.

Seagrass beds also provide a clean up service to the waters they inhabit. The two most common types of seagrass are Thalassia testudinum and Syringodium filiforme, commonly referred to turtle grass and manatee grass. Seagrasses are unique in that they are an angiosperm, a flowering plant. Most angiosperms live above sea level, but seagrasses are the exception. Once considered an algae it is now known that seagrasses have true roots, stems, leaves, etc. and all of these contain vascular tissue. Thalassia testudinum is in the Hydrocharitaceae family and can be identified by its leaves that are flat and ribbon like. Beds of Thalassia testudinum can extend for acres and are colonized by over one hundred species of epiphytes which are plants that gain moisture and oxygen from the surrounding air (in this case water) and attach themselves to another plant (in this case seagrass). Second in proportion to Thalassia testudinum in the Florida coast is Syringodium filiforme from the Cymodoceaceae family. Easily distinguished from its flat leaved neighbor by its cylindrical leaves. As their common names suggest, these grasses are the most grazed upon by sea turtles and manatees, as well as the endangered dugong, which closely resembles a manatee. The beds also provide shelter to seahorses and small fish from predators. Together with mangrove tracts these beds further clean the waters from chemical dumping and runoff to prevent nutrients from reaching the reefs, which would result in uncontrollable algae growth. A destroyed seagrass plot takes over decades to recover, not enough information is known on these vital plants to determine their exact recovery rate. More interest has been given to the preservation and restoration of mangrove forests and seagrass beds but there is still much to be learned from these organisms. Several other species of plants thrive on the coastal shores of the Caribbean, each of these help to balance and maintain the fragile ecosystem that exists there.

Borrichia arborescens, commonly referred to as silver sea-oxeye or tall sea-oxeye daisy, is in the Asteraceae family. This shrub grows between 2-4 feet and has silver/green foliage. Yellow daisy like flowers bloom from Borrichia arborescens but unlike daisies, the disk of the flower is larger than the rays that surround it. The fruit of Borrichia arborescens is small and needle like. A tea prepared from the leaves and branch tips is used for relief from colds, coughs, and fish poisoning. The leaves have also been eaten to prevent scurvy.

Coccoloba uvifera from the Polygonaceae family grows in a variety of forms from shrubs to trees. Their fruit that resembles grapes can identify these plants; accordingly this plant is often referred to as sea grape. The foliage of Coccoloba uvifera consists of broad, circular leaves that have distinct red veins when they mature. There are small ivory flowers that bloom from the plant but the “grapes” ripen in clusters from green to purple and are edible. Only female trees yield fruit so it is important to be able to identify the plant by its leaves as well. Sea grape is used in hedges and as a street tree in coastal cities throughout the tropics. Coccoloba uvifera is one of the most commonly used native plants in South Florida landscaping.

Ipomoea pescaprae grows as a vine and strongly resembles the morning glories we have growing in Ohio. Commonly called railroad vine or beach morning glory, Ipomoea pescaprae produces purple or pink funnel-shaped flowers which bloom in the morning and close around noon. Unlike seagrass, Ipomoea pescaprae grows very quickly and is used in many gardens around the Florida area since it is well adapted to beaches and coastal dunes. Planting Ipomoea pescaprae can prevent erosion as well as brighten up the landscape with color.

Mallotonia gnaphalodes is commonly known as sea lavender and belongs to the Boraginaceae family. This woody plant grows between 4-6 feet and has silvery leaves. The leaves are pubescent which means they are covered in tiny hairs that aid the plant in reducing water loss in the arid environment. Mallotonia gnaphalodes also has small white flowers that grow among the clustered leaves at the tip of the branches.

Uniola paniculata is an herbaceous plant that grows between 3-5 feet and highly resembles common oats giving it the name sea oats. Part of the Poaceae family, Uniola paniculata is highly salt tolerant and can grow close to the water’s edge. Growing from rhizomes, which are elongated stems that grow underground and sprout roots below and shoots above, Uniola paniculata can be a problem as an invasive species in certain areas but also plays an important role by maintaining sand dunes. Uniola paniculata is protected in Florida and Georgia (and probably other states as well), not because it is endangered or threatened, but because it stabilizes sand dunes. It is unlawful to pick wild sea oats (even the seeds).

Scaevola plumieri, also known as inkberry or beach plum, can be seen bearing white or black, round fruits. Scaevola plumieri is in the Goodeniaceae family, a family that is mostly limited to Australia and Oceania. The Goodeniaceae has fourteen genera, but only the Scaevola radiated outward. The drift seeds of the inkberry reached Africa, the Pacific Islands, the Caribbean, and land around the Gulf of Mexico. This plant is woody and grows between 1-6 feet with succulent stems which root when they come into contact with the ground. Growth such as this is referred to as tip layering. Scaevola plumieri has leaves that are glossy, thick, fleshy, and clustered at branch tips such as Mallotonia gnaphalodes. The fruits of Scaevola plumieri are edible but too many will result in sickness.

These eleven plants are all remarkably adapted to the harsh conditions of coastal living and they work together to hold the marine ecosystem in balance. With more research the valuable role of these plants will become more evident but they are being threatened from every angle. Restoration projects and protected areas are now the most important way to save these species before they disappear and with them all their unique assets.

Sources
Davidson, Osha Gray. The Enchanted Braid. Canada: John Wiley & Sons, Inc., 1998.

Garibaldi, Cristina. "Avicennia germinans." (1992): 315-318.

Gerace, Donald T., Gary K. Ostrander, and Garriet W. Smith. "Environment and development in Coastal Regions and Small Islands: San Salvador, Bahamas." 20 Mar 2005 .

Gilman, Edward F. “Borrichia arborescens.” University of Florida Institute of Food and Agricultural Sciences October 1999.

Gilman, Edward F. "Scaevola plumieri." University of Florida Institute of Food and Agricultural Sciences October 1999.

James A. Duke. 1983. Handbook of Energy Crops. Unpublished. http://www.hort.purdue.edu/newcrop/duke_energy/Rhizophora_mangle.html

Lodge, Thomas. The Everglades handbook: understanding the ecosystem. 2nd ed. Boca Raton: CRC Press, 2005.

McCoy, Earl. Rare, threatened, and endangered plant species southwest Florida and potential OCS activity impacts / by Earl D. McCoy; performed for National Coastal Ecosystems Team, Biological Services Program, Fish and Wildlife Service, U.S. Department of the Interior. Washington D.C.: The Team, 1981.

Meerow, Alan W. "Native Ground Covers for South Florida." University of Florida IFAS Extension September 2001.

Yogi, Julie, Melvin Wong, and David Hensley. "Salt and wind tolerance for landscape plants in Hawaii." University of Hawaii and Manoa College of Tropical Agriculture and Human Resources September 1996: 13-22.



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