There are more than 59 species of seagrasses; they have long, narrow leaves and often grow in "meadows" that look like grassland. They anchor themselves in mud or sand in sheltered inlets, estuaries and bays and conduct photosynthesis from light filtered through the water. They spend their entire life under water, including pollination.
Eelgrass, Zostera marina, is a sea-growing plant with roots, leaves, flower and a kind of seed. The most studied of all seagrasses, eelgrass is found in shallow, wave-protected estuaries and bays on both sides of North America, from Greenland to the Carolinas and from the Bering Sea to the Gulf of California. It must be rooted in sediment but requires light, usually growing in water less than 6 feet deep. Eelgrass dominates other seagrasses in cold northern waters.
Phyllospadix scouleri, an abundant surfgrass on the West Coast, is found in tide pools or below zero tide level from British Columbia to southern California. It is host to red algae and provides a habitat for fish and the California spiny lobster. It is sensitive to oil spills and sewage discharge, but if its system of spreading rhizomes survives, it can recover.
A related surfgrass, Phyllospandix torreyi, is more often found in sand-scoured sea bottoms from northern California to Baja California. It uses pointed, hooked bristles to cling to rocks.
Turtle grass, Thalassia testudinum, is a seagrass found widely from Florida, the Gulf of Mexico and the Caribbean south to Venezuela. It grows on mud and sand from 15 to 45 feet deep, depending on the species and the clarity of the local water. It is the dominant seagrass in southeast Florida and the Florida Gulf Coast. There are more species of seagrass in tropical waters than in temperate zones.
Manatee grass, Syringodium filiforme Kuetz, is found throughout the Caribbean, the Bahamas and Bermuda. It likes loose muddy sand bottoms of lagoons, inlets and tidal channels in mangrove swamps. It is a favorite source of food for several varieties of fish, sea urchins, sea turtles and conch.
Johnson's seagrass, Halophila johnsonii, is found in areas with high tidal currents and turbid waters in the area of Biscayne Bay, Florida. It likes coastal lagoons and the intertidal zone and grows at a greater depth than other seagrasses. Johnson's seagrass is a favorite food of the West Indian manatee and green sea turtles. It is threatened by dredging, propeller scarring, hurricanes, storm surges and polluted water.