Eelgrasses, in the genus Zostera, are flowering plants that spend their entire lives submerged in seawater. Other coastal plants, such as sea lavender and sea rocket, flaunt their flowers on the saltmarsh and strandline; Zoestra, however, has taken the plunge.
1. The magic number
Zostera is one of 11 seagrass genera, of which Britain’s coasts have three: Z. marina (eelgrass); Z. angustifolia (narrow-leaved eelgrass); and Z. noltei (dwarf eelgrass).
2. Versatile uses
Mattresses stuffed with dried eelgrass were used in French barracks in WWI.
3. Food and shelter
Eelgrass beds offer a refuge for long-snouted seahorses, which grip the grass with their tails. Tropical seagrass beds are vital food sources for green turtles, manatees and dugongs.
4. Ancient history
One colony of Mediterranean eelgrass (genus Posidonia) off the Ibiza coast is said to be 100,000 years old.
5. Family planning
To reproduce, eelgrass plants release long, thread-like pollen that drifts in the tide, becoming entangled in the grappling-hook-shaped female stigmas of other eelgrass plants.
6. Far and wide
Eelgrass propagules can be carried to far-away coasts on ocean currents, and sometimes even on the feathers of migratory wildfowl and wading birds. Zostera species have an enormous geographical range and can be found along shorelines from the Arctic to the Antarctic, via East Africa, the Antipodes and North Pacific.
7. Magnificent meadows
Migratory wildfowl, such as brent geese, whooper swans and wigeons feed from eelgrass meadows, which are also vital nurseries for fish, and cuttlefish attach eggs to their stems.
Illustration: Mike Langman
Phil Gates taught biology at Durham University and writes for The Guardian’s Country Diary column.