Zostera is a small genus of widely distributed seagrasses, commonly called marine eelgrass, or simply seagrass or eelgrass, and also known as seaweed by some fishermen and recreational boaters including yachtsmen.found on sandy substrates or in estuaries, usually submerged or partially floating. Most Zostera are perennial. They have long, bright green, ribbon-like leaves, the width of which are about 0.4 in. Short stems grow up from extensive, white branching rhizomes. The flowers are enclosed in the sheaths of the leaf bases; the fruits are bladdery and can float. This Zostera grows in muddy and sandy shores only at and below spring tides. This plant is an important member of the coastal ecosystem in many areas because it helps to physically form the habitat and it plays a crucial role for many other species. For example, it provides a sheltered spawning ground for the Pacific herring (Clupea pallasii). Juvenile Atlantic cod (Gadus morhua) hide in eelgrass beds as they grow. The blue mussel (Mytilus edulis) attaches to its leaves. A great many animals use the plant for food, including the isopod Idotea chelipes and the purple sea urchin Paracentrotus lividus. The Atlantic brant (Branta bernicula hrota) subsists almost entirely on the plant. When the eelgrass dies, detaches, and washes up on the beach, a whole new ecosystem is founded; many species of insects and other invertebrates begin to inhabit the dead plant, including the amphipod Talitrus saltator.