Seagrass is unique among flowering plants, in that all but one genus can live entirely immersed in seawater. More closely related to lilies and gingers than to true grasses, they grow in sediment on the sea floor, up to a depth of four metres. They have long narrow elongate leaves and a buried root-like structure, a rhizome. 

Behaviour

Seagrasses occupy a variety of coastal habitats, but typically occur in shallow, sheltered soft-bottomed marine coastlines and estuaries. Seagrass meadows may be monospecific or may consist of multi-species communities.  

Size

• Average length of leaves: 6-22 cm 
• Lifespan: Life span of single leaves varies between two and six months over the year, depending on the period in which they first appear on the shoot 

Status

Seagrass beds are a Priority Marine Feature, a UK Biodiversity Action Plan (BAP) habitat and an OSPAR (Oslo and Paris Convention) threatened and declining habitat. 

Distribution

Seagrass meadows can be found around the coast of the UK, but as a habitat they are rare and declining.  Approximately, 90% have been lost, half of which over the past thirty years.

When to see

January to December 

Facts

• There are four species of seagrass in the UK: two species of Tasselweeds (Ruppia maritima and Ruppia cirrhosa) and two Zostera species (Zostera marina and Zostera noltei), commonly known as eelgrass.  

• Seagrass/algae meadows are rated the third most valuable ecosystem globally (on a per hectare basis), only preceded by estuaries and wetlands. 
• Globally, seagrasses are as important as forests in storing carbon (on an area-basis); they can store carbon thirty-five times faster than rainforests.