1. Description

2. Distribution and habitat

3. Reproduction

4. Ecology

5. Relationship to humans

6. References

Description

Distribution and habitat

Turtle grass is found growing in meadows in calm shallow waters throughout the Caribbean Sea and the Gulf of Mexico and as far north as Cape Canaveral in Florida. Extensive meadows can be formed on muddy sand, coarse sandy and clayey seabeds, especially those with a calcareous content. This grass favours high-salinity waters with low turbidity such as calm lagoons. It cannot grow in fresh water but some growth is possible at a salinity of 10 parts per thousand. The plant's preferred range is 25 to 38.5 parts per thousand with a temperature range of {{convert|20|to|30|C|F}}. It is found from low-tide mark down to depths of {{convert|30|m}} depending on water clarity. It often grows in meadows with other seagrasses where it is the climax species.^[5]

Its temporal range spans from the Middle Eocene to present.^[7]

Reproduction

Turtle grass can reproduce both through vegetative and sexual reproduction. The main propagation method is by extension of the underground rhizome, or stem. This increase in rhizome length results in asexual ramets, or clonal colonies which are genetic replicates of the parent plant. A sexual reproduction mainly takes place in spring and early summer when productivity and sugar storage is highest, however, it can happen at any time of year. Although this propagation method results in an increase in the size of the turtle grass bed, extensive asexual reproduction limits genetic diversity and can put the meadow at severe risk if there is a disease outbreak.^[5] It has been found that where plants have been damaged mechanically, such as by the propellers of boats, the cut ends of rhizomes are unable to grow and holes may develop in the turtle grass meadow.^[4]

Turtle grass can also sexually reproduce through the production of underwater flowers and hydrophily. Turtle grass is dioecious, which means that there are separate male and female plants, each which produce an imperfect flower containing only one sex. Sexual reproduction takes place from April to July depending on location, however, flowering has been observed during the warm winters in Tampa Bay, Florida.^[8][9][10] When a plant produces flowers each small, flower is born onto a peduncle (botany). Female plants typically grow one green flower, while males often produce three to five pink, or white flowers.^[11][12][13] At night when male flowers are fully mature, they release mucilaginous pollen into the water column.^[14][15][16] The following morning, female flowers open.

There are two methods of pollination: hydrophily and biotic pollination. Through hydrophily, the pollen grains are carried through the water column by tides or currents and deposited upon an open pistillateflower. More recent investigation however, has uncovered active biotic pollination.Underwater video cameras have revealed that Crustacean, Polychaete, and Amphipoda swam towards open male flowers.^{[16][14][15][17]} These creatures were attracted to the seagrass’s nutritious mucilage—a carbohydrate-rich substance that houses pollen. As the invertebrates feeds on the mucilage, excess pollen grains stick to their bodies. They move from flower to flower feeding and spreading the pollen from male to female.

Seeds begin to develop in about 2–4 weeks if fertilization occurred.^[5] Female turtle grass fruits develop into green capsule about 20–25 mm in diameter and can include 1-6 small seedlings.^[15][11] After about 8 weeks of growth, the fruit undergoes dehiscence (botany), which releases neutrally buoyant seeds into the water column.^{[13][11][9][13][5]} Sometimes, if an event occurs producing significant water turbulence, an immature fruit may break off from the peduncle. This buoyant fruit acts as a transportation vessel as it continues to develop as. The fruit will moved around by wind, currents, and tides until it eventually split open to release the negatively botany seedlings into a new area. If the new location has favorable environmental conditions, the seedling will begin to grow. This is one way viviparous seedlings can start new patches of seagrass.^[18]

Ecology

Turtle grass and other seagrasses form meadows which are important habitats and feeding grounds. Associated seagrass species include Halophila engelmannii and Syringodium filiforme. Many epiphytes grow on the grasses, and algae, diatoms and bacterial films cover the surface of the leaf blades. The grass is eaten by turtles, herbivorous parrotfish, surgeonfish and sea urchins while the leaf surface films are a food source for many small invertebrates.^[5] Decaying turtle grass leaves are responsible for the majority of detritus in meadow areas. This grass is subject to periodic dieback episodes in the Florida Bay area. One such episode in 1987 killed off a large proportion of the plants and the resulting increased sedimentation and greater growth of epiphytes on the remaining plants caused a secondary dieback event. The areas affected have since been reseeded and planted with rhizomes and have recovered. In general, the population of this grass is stable.^[18]

Rhizomatous green algae in the genus Caulerpa often live among the grasses and many animals make seagrass meadows their home. These include bivalves and other molluscs, polychaete worms, amphipods and juvenile fish which hide among the leaf blades, sea urchins, crabs and caridean shrimps.^[5]

Relationship to humans

Along with Thalassia hemprichii which shares its common name with Thalassia testudinum, Turtle grass makes its way into the aquarium trade and it may be cropped at 12 in/30 cm.^[19]

References

• Ratu Ratini
• Ratus Frei
• Ratus ratus
• Ratu Vashti Annisa
• Ratu Veresa Toma
• Ratuwamai
• Ratuwamai municipality
• RA-TV
• Rat variety (disambiguation)
• Ratvik
• Ratwatte
• Ratzborg
• Ratzeburg Tortricid
• Ratzeburg tortricid
• Ratzenhofer
• Ratzer, Steve
• Ratzia
• Ratziinae
• Ratzinger Circle of Alumni (Ratzinger Schülerkreis)
• Ratzinger Prize
• Ratzlingen, Lower Saxony
• Ratzon, Michael
• Ratzsanktpeter
• Ratón de ferretería
• Rauan Isaliyev