ålegras

Ålegras, or eelgrass (Zostera marina), is a marine flowering plant in the seagrass family Zosteraceae. It forms extensive underwater meadows in shallow coastal waters of the temperate Northern Hemisphere, notably around Europe and North America. It grows on sandy or muddy substrates in sheltered bays, estuaries, and lagoons where light reaches the seabed.

Description and life cycle. Ålegras has slender, grasslike leaves that arise from a creeping rhizome system. Leaves are typically flat and ribbonlike, often up to several tens of centimeters long and about 1–2 centimeters wide. The plant reproduces both asexually through rhizome spreading and sexually via small, inconspicuous flowers on a flowering shoot that emerges toward the surface in summer. Seeds disperse with the water or remain in the sediment, contributing to genetic diversity and recolonization.

Ecology and ecosystem services. Eelgrass meadows provide important habitat for a wide range of marine invertebrates and juvenile fish, functioning as nurseries and feeding grounds. They help stabilize sediments, reduce shoreline erosion, and improve water quality by trapping particulates and taking up nutrients. The dense vegetation also stores carbon in the underlying sediments, contributing to blue carbon.

Threats and conservation. Beds are sensitive to reduced light from nutrient pollution and turbidity, dredging, and physical disturbance from boating and fishing activities. Climate change and disease outbreaks have historically affected populations. Restoration and conservation efforts include protecting eelgrass habitats, reducing pollution, and restoring beds through transplantation or seed-based approaches. As a seagrass, ålegras is not a true grass but a marine angiosperm adapted to submerged life.