Eelgrass

Description

Zostera marina is 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 1 centimetre (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. Zostera beds are important for sediment deposition, substrate stabilization, as substrate for epiphytic algae and micro-invertebrates, and as nursery grounds for many species of economically important fish and shellfish. Zostera often forms beds in bay mud in the estuarine setting. It is an important food for Brent geese and wigeons, and even (occasionally) caterpillars of the grass moth Dolicharthria punctalis. The slime mold Labyrinthula zosterae can cause the wasting disease of Zostera, with Z. marina being particularly susceptible, causing a decrease in the populations of the fauna that depend on Zostera. Zostera is able to maintain its turgor at a constant pressure in response to fluctuations in environmental osmolarity. It achieves this by losing solutes as the tide goes out and gaining solutes as the tide comes in