seagrass

Seagrass or seagrasses are a group of marine angiosperms that form dense underwater meadows in shallow coastal waters. They include genera such as Zostera (eelgrass), Posidonia, Thalassia, and Syringodium. Unlike seaweeds, seagrasses are true plants with roots, stems, and leaves, and they grow by means of underwater rhizomes and flowering shoots. They are adapted to saline, fully submerged conditions and rely on underwater photosynthesis.

Distribution and habitat: Seagrasses occur in temperate and tropical regions worldwide, in relatively clear, low-energy waters where sediments are suitable for rooting. They occupy shallow bays, lagoons, estuaries, and coastal shelves, and light availability largely governs their depth range.

Growth and reproduction: Seagrasses have horizontally growing rhizomes that stabilize sediment and form meadows. They reproduce sexually via flowering shoots and seeds and also asexually through rhizome expansion, enabling meadow recovery after disturbance. Lifespans can be many decades.

Ecological importance: Seagrass meadows serve as nursery habitats for many fish and invertebrates, stabilize sediments, dampen wave energy, and significantly contribute to carbon sequestration, sometimes referred to as blue carbon. They also influence nutrient cycling and water clarity by trapping fine particles.

Threats and conservation: Seagrasses face habitat loss from coastal development, dredging, boat propellers, and anchor damage, as well as eutrophication, sedimentation, and rising temperatures. Climate change and disease can cause rapid declines. Conservation approaches include protection of habitats, water-quality improvements, and restoration projects such as transplantation and seed-based methods.