Seagrasses are the only flowering plants which grow in marine environments. There are about 60 species of fully marine seagrasses which belong to four families, all in the order Alismatales. Seagrasses evolved from terrestrial plants which recolonised the ocean 70 to 100 million years ago.
Hydrocharitaceae is a flowering plant family including 16 known genera with a total of ca 135 known species, that including a number of species of aquatic plant, for instance the tape-grasses, the well known Canadian waterweed, and frogbit.
Najas, the water-nymphs or naiads, is a genus of aquatic plants. It is cosmopolitan in distribution, first described for modern science by Linnaeus in 1753. Until 1997, it was rarely placed in the Hydrocharitaceae, and was often taken as constituting the family Najadaceae.
Vallisneria americana, commonly called wild celery, water-celery, tape grass, or eelgrass, is a plant in the family Hydrocharitaceae, the "tape-grasses". V. americana is a fresh water species that can tolerate salt, living in salinities varying from fresh water to 18 parts per thousand, although the limit to the salt tolerance is unclear, and is generally dependent on the duration and intensity of the plants’ exposure to the saline water. V. americana is a deep rooted plant with leaves, approximately one inch wide, with the ability to rise two or more meters above the clustered base of the plant. Contrary to the implications of one of its common names, wild celery bears little to no resemblance to the celery used as a vegetable. V. americana grows under water and is consumed by various animals, including the canvasback. The plants themselves are long, limp, flat, and have a green mid-ridge.
Halophila johnsonii, or Johnson's seagrass, is a small, asexual seagrass in the family Hydrocharitaceae. It occurs only on the southeastern coast of Florida, and was the first marine plant listed on the United States endangered species list, though it was removed from listing in April 2022. Female flowers have been observed, but even with decade long observational studies, neither male flowers nor seed have ever been observed.
Flabellia is a genus of green algae in the family Halimedaceae. Flabellaria is an accepted synonym of this genus. It is a monotypic genus and Flabellia petiolata is the only species; it is found in the eastern Atlantic Ocean and the Mediterranean Sea.
Simpson Bay Lagoon is one of the largest inland lagoons in the West Indies of the Caribbean. It is located on the island of Saint Martin. The border between the French and Dutch halves of the island runs across the centre of the lagoon. There are two small islands that lie in the lagoon: the larger, Grand Ilet to the north, is within the French region of Saint-Martin; the smaller, Little Key, to the south, is on the Dutch Sint Maarten side.
Halophila is a genus of seagrasses in the family Hydrocharitaceae, the tape-grasses. It was described as a genus in 1806. The number of its contained species, and its own placement in the order Alismatales, has evolved.
The Seagrasses of Western Australia are submerged flowering plants found along the coast, around islands, and in Estuaries of Western Australia. The region contains some of the largest seagrass meadows in the world, and is the most diverse in the number of species. The variety of habitats along its western and southern coasts is often soft sands in shallow subtropical waters, ideal for these plants.
Thalassia testudinum, commonly known as turtlegrass, is a species of marine seagrass. It forms meadows in shallow sandy or muddy locations in the Caribbean Sea and the Gulf of Mexico. Turtle grass and other seagrasses form meadows which are important habitats and feeding grounds. The grass is eaten by turtles and herbivorous fish, supports many epiphytes, and provides habitat for juvenile fish and many invertebrate taxa.
Ceratophyllum submersum, commonly known as the soft hornwort or tropical hornwort, is a species of Ceratophyllum. It is a submerged, free-floating aquatic plant. It has been reported from Europe, Central Asia, northern Africa, scattered places in tropical Africa, Turkey, Oman, Florida, and the Dominican Republic. It is similar to the submerged macrophyte Ceratophyllum demersum, a congeneric plant that is found in most regions of the world.
Halodule wrightii is an aquatic plant in the Cymodoceaceae family. It is referred to by the common names shoal grass or shoalweed, and is a plant species native to seacoasts of some of the warmer oceans of the world.
Ottelia is a genus of an aquatic plant family Hydrocharitaceae described as a genus in 1805. The genus is native to tropical and subtropical regions of Africa, Asia, South America, and Australia.
Zostera muelleri is a southern hemisphere temperate species of seagrass native to the seacoasts of South Australia, Victoria and Tasmania. and New Zealand. Today, Zostera muelleri can be found in regions of Australia, New Zealand, and Papua New Guinea, as well as areas of the eastern Indian Ocean, and the southwest and western central Pacific Ocean. Zostera muelleri is a marine angiosperm, and is commonly referred to as eelgrass or garweed. It is a fast growing and readily colonizing species that serves as a feeding ground for wading birds and aquatic animals, and a breeding ground for juvenile fish and shrimp species.
Halophila baillonis is a species of aquatic plant in the family Hydrocharitaceae. It is referred to by the common name clover grass. It is native to Brazil, Cayman Islands, Colombia, Costa Rica, Jamaica, Leeward Islands, Netherlands Antilles, Panama, Puerto Rico, Trinidad and Tobago, and Venezuela. It is listed on the IUCN Red List as "vulnerable" due to its naturally rare occurrence and fragmented populations.
Ludwigia grandiflora, the water primrose, is an aquatic plant of the order Myrtales.
Syringodium isoetifolium, commonly known as noodle seagrass, is a species of flowering plant in the family Cymodoceaceae, growing underwater in marine habitats. It forms seagrass meadows in shallow sandy or muddy locations in the Indian and Pacific Oceans.
Juncus bulbosus, the bulbous rush, is a species of flowering plant in the genus Juncus, native to Iceland, the Faroes, Europe, Macaronesia, and northwest Africa. It has been introduced to Australia, New Zealand, and some locations in northern North America. It is capable of nuisance growth in lakes and streams.
Pterocarpus officinalis, the dragonsblood tree, is a species of flowering plant in the family Fabaceae, native to southern Mexico, Central America, the Caribbean, and northern South America. It is typically found in coastal freshwater or slightly brackish habitats, in association with mangroves that occupy the more saline areas. Its timber is commercially traded.
Halophila australis, the paddle weed, is a species of seagrass in the family Hydrocharitaceae, native to southern Australia. Preferring calm waters, it is found on both mud and sand substrates from the low tide mark down to about 23 m (75 ft).
