Named by:

• Linnaeus, 1758.

Synonyms:

• None.

Varieties:

• Zostera marina var. angustifolia (Hornem).
• Zostera marina var. stenophyila (Ascherson & Graebner). The only difference from var. angustifolia is related to leaf vein number and location. (Butcher, 1941b).

Common names:

• Common eelgrass, wigeon grass, broad-leaved grass wrack, marlee, sedge, slitch

Zone:

• In the British Isles, it is considered to be fully marine and subtidal.
• Occurs in the shallow sublittoral, typically from below the mean low water mark to 5m.
• Elsewhere, in northern Europe and North America, Z. marina is recorded growing intertidally (mid-shore) as well as subtidally but these records may refer to Z. marina var. angustifolia = Z. angustifolia.

Habitat:

• Primarily muddy-sand or mud habitats.

Colour:

• Dark green, with leathery texture.

Abundance:

• This species appears to have been the most seriously affected by wasting disease
• Prior to these outbreaks, it was probably the most common species in Britain and populations do not appear to have returned to their original levels.

Sterile shoots:

• The leaves are alternately arranged and flattened.
• The sheaths at the base are fused into a tube around the stem.

-Leaf length:

• Maximum - 1 m, but typically between 20 - 50 cm.

-Leaf width:

• 4 - 10 mm wide.

-Leaf tip:

• Narrow, rounded tips, tips may have a sharp point (mucronate).

-Leaf veins:

• Approximately 5 – 11 parallel veins, that may be regularly spaced.

Flowering shoots

• Branched.

-Length:

• Are generally shorter than the sterile shoots, with a maximum length of 60 cm.

-Width:

• Are narrower than the sterile shoots.

• 2:1 - the stigma is twice as long as the style.

• Mid to late summer.

Seeds:

• Ribbed, brown seeds, up to 3.5 mm long, excluding the style.

Rhizomes:

• High root/rhizome biomass.
• In transverse section, clumps of strengthening fibres are present in the outer cortex (Butcher, 1941b).

• Generally perennial, beds expand by vegetative growth.
• Annual populations of Z. marina have been recorded in northern Europe and North America (van Lent & Vershuure, 1994a, b). However, these may be populations of what is considered to be Z. angustifolia within the British Isles.

• Can remain green throughout the year. Summer leaves shed in the autumn, are generally replaced by smaller winter leaves.

Longevity:

• Unknown.

Named by:

• (Hornem) Reichenb.

Synonyms:

• Z. hornemanniana (Tutin).
• Z. marina var. angustifolia (Hornem).

Common names:

• Narrow-leaved eelgrass.

Zone:

• It is commonly intertidal, ranging from the mid-shore down to Low Water Springs.
• It is considered to be just as susceptible to desiccation as Z. marina but survives intertidally where mudflats provide damp conditions.
• It may occasionally be found in deeper water, to a maximum depth of 4 m. However, these may be populations of what is considered to be Z. marina.

Habitat:

• It is common in estuarine conditions.
• It often occurs in mixed beds with Z. noltii, where it predominates in waterlogged depressions between the free-draining hummocks dominated by Z. noltii.

Colour:

• Light, yellow-green.

Abundance:

• In Britain, it may have replaced Z. marina as the most common Zostera species.

Sterile shoots:

• The leaves are alternately arranged and flattened.
• The sheaths at the base are fused into a tube around the stem.

- Leaf length:

• Between 15 - 30 cm.

- Leaf width:

• Typically around 2 (1.5 - 3) mm

- Leaf tip:

• Are initially rounded but as the plant matures, they become notched (emarginate).

- Leaf veins:

• Approximately 3 -5 veins.

Flowering shoots:

• Branched.

- Length:

• Are generally shorter than the sterile shoots, between 10 - 30 cm.

- Width:

• Are slightly narrower than the sterile shoots, around 1 mm.

- Stigma : style ratio:

• 1:1- the stigma is as long as the style

Flowering period:

• From early to late summer.

Seeds:

• Ribbed, brown seeds, 2.5 - 3.0 mm long, excluding the style.

Rhizomes:

• 1.0 - 2.0 mm thick and have slightly swollen nodes (Wyer et al, 1977);
• In transverse section, the fibre bundles occur in the outer layer of the cortex (Butcher, 1941b; Wyer et al, 1977).

• It appears to rely more upon annual seed set than Z. marina.

Seasonal leaf cover

• Begin loosing leaves from late September and beds may be bare of leaves by mid-winter (Wyer et al, 1977).

Longevity:

• Unknown, but some populations may be annual.

Named by:

• Hornemann.

Synonyms:

• Z. nana (Roth).

Common names:

• Dwarf eelgrass.

Zone:

• It is intertidal, forming a definite belt between Mean High Water and Mean Low Water Neap.
• It is the most tolerant of desiccation and is found highest up the shore.
• It is rarely found below the low water mark (Stace, 1997).

Habitat:

• Like Z. angustifolia, it is common in estuarine conditions.
• It often occurs with Z. angustifolia, with Z. noltii predominating on free-draining hummocks whilst Z. angustifolia predominates in the water-logged depressions.

Colour:

• Grass-green.

Abundance:

• In Britain, it the least common of the three Zostera species.

Sterile shoots:

• The leaves are alternately arranged and flattened.
• The sheath at the base clasps the stem but is not fused into a tube.

- Leaf length:

• Maximum length - 22 cm.

- Leaf width:

• 0.5 - 1.5 mm.

- Leaf tip:

• The leaves of Z. noltii are initially rounded but as the plant matures, they become notched (emarginate).

- Leaf veins:

• Approximately 3 irregularly spaced veins.

Flowering shoots:

• Un-branched or with a few branches near the base.

- Length:

• Are generally shorter than the sterile shoots.

- Width:

• Are generally narrower than the sterile shoots.

- Stigma : style ratio:

Flowering period:

• From mid to late summer.

Seeds:

• Smooth, white seeds, 1.5 - 2.0 mm long, excluding the style.

Rhizomes:

• In transverse section, the strengthening fibre bundles occur in the in the inner part of the cortical layer. (Butcher, 1941b; Wyer et al, 1977).

• Seed production is high.
• However, vegetative growth appears to be of equal or greater importance.

Seasonal leaf cover

• Retains its leaves well into the winter (Wyer et al, 1977).

Longevity:

• Unknown.