Turtlegrass, also known as Thalassia testudinum, is a type of marine seagrass. It’s found in the Caribbean Sea and the Gulf of Mexico, usually in shallow sandy or muddy places.
Turtlegrass is important because it forms meadows that serve as habitats and feeding grounds for many animals, including turtles, fish, and invertebrates.
How Does Turtlegrass Look Like?
Turtlegrass is a perennial grass that grows from a long, jointed rhizome.
The rhizome is buried 5 to 10 cm (2 to 4 in) deep in the ground, sometimes even up to 25 centimeters (9.8 in).
Some parts of the rhizome have no leaves, while others have a bunch of erect, linear leaf blades.
These blades can be up to 30 centimeters (12 in) long and 2 cm (0.8 in) wide with rounded tips.
Turtlegrass has small greenish-white flowers that sometimes have a pink tint. After the flowers bloom, they are followed by seed pods.
Where Does Turtlegrass Grow?
Distribution and Habitat
Turtlegrass grows in meadows throughout the Caribbean Sea, the Gulf of Mexico, and as far north as Cape Canaveral in Florida.
It forms large meadows on muddy sand, coarse sandy and clayey seabeds, especially those with a calcareous content.
Turtlegrass prefers high-salinity waters with low turbidity, such as calm lagoons. It cannot grow in freshwater but can grow in salinity levels as low as 10 parts per thousand.
The ideal salinity range for Turtlegrass is 25 to 38.5 parts per thousand, with a temperature range of 20°C to 30°C (68°F to 86°F).
It’s found from the low-tide mark down to depths of 30 meters (98 ft), depending on water clarity. Turtlegrass often grows with other seagrasses and is the climax species in meadows.
How Does Turtlegrass Reproduce?
Reproduction Methods
Turtlegrass reproduces in two ways: vegetative and sexual reproduction.
The main method is through the growth of the underground rhizome, or stem. This growth results in asexual ramets, which are genetic copies of the parent plant.
Although asexual reproduction helps increase the size of the meadow, it can limit genetic diversity and put the meadow at risk if there is a disease outbreak.
Sexual reproduction occurs through the production of underwater flowers and hydrophily.
Turtlegrass is dioecious, meaning that there are separate male and female plants. Each plant produces an imperfect flower containing only one gender.
Sexual reproduction takes place from April to July, depending on the location.
Pollination
There are two methods of pollination for Turtlegrass: hydrophily and biotic pollination.
In hydrophilic pollination, pollen grains are carried through the water column by tides or currents and deposited on an open female flower.
Underwater video cameras have revealed small creatures like crustaceans, polychaetes, and amphipods swimming toward open male flowers.
These creatures are attracted to the nutritious mucilage, a carbohydrate-rich substance that houses pollen.
As they feed on the mucilage, excess pollen grains stick to their bodies, and they move from flower to flower, spreading pollen from male to female flowers.
What Is the Ecology of Turtlegrass Meadows?
Turtlegrass and other seagrasses form meadows that are important habitats and feeding grounds for many animals.
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.
Decaying Turtlegrass 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.
What Animals Live in Turtlegrass Meadows?
Many animals make their homes in seagrass meadows, including bivalves and other molluscs, polychaete worms, amphipods, juvenile fish (which hide among the leaf blades), sea urchins, crabs, and caridean shrimps.
How Is Turtlegrass Used by Humans?
Turtlegrass, along with Thalassia hemprichii (which shares its common name with Thalassia testudinum), is sometimes used in the aquarium trade.
It can be cropped at 12 in/30 cm to be used in aquariums.
Scientific Classification
| Kingdom: | Plantae |
| Order: | Alismatales |
| Family: | Hydrocharitaceae |
| Genus: | Thalassia |
| Scientific Name: | Thalassia testudinum |
| Also Known As: | Turtlegrass |
| Conservation Status: | Least Concern |