BIOTIC

BIOTIC Species Information for Zostera marina

Researched by

Dr Harvey Tyler-Walters

Data supplied by

MarLIN

Refereed by

Dr Leigh Jones

Taxonomy

Scientific name

Zostera marina

Common name

Common eelgrass

MCS Code

None

Recent Synonyms

None

Phylum

Anthophyta

Subphylum

Superclass

Class

Liliopsida

Subclass

Order

Potamogetonales

Suborder

Family

Zosteraceae

Genus

Zostera

Species

marina

Subspecies

Additional Information

Other common names include, wigeon grass, broad leaved grass wrack, marlee, sedge and slitch. Perennial populations show a seasonal changes in leaf growth, the long leaves found in summer are replaced by shorter, slow growing leaves in winter. The morphological characteristics, especially leaf width may vary with environmental conditions (Phillips & Menez 1988). In the UK literature Zostera marina is distinguished from Zostera angustifolia on the basis of morphology. However, outside the UK most authors consider Zostera angustifolia to be a phenotypic variant of Zostera marina. To avoid confusion only data relating to Zostera marina is presented.

Taxonomy References

Hartog den, 1970, Phillips & Menez, 1988, Davison & Hughes, 1998, Guiry, 2000, NBN, 2002,

General Biology

Growth form

Foliose

Feeding method

Photoautotroph

Mobility/Movement

Permanent attachment

Environmental position

Epifloral
Infaunal

Typical food types

Not relevant

Habit

Attached

Bioturbator

Not relevant

Flexibility

High (>45 degrees)

Fragility

Intermediate

Size

Medium-large(21-50cm)

Height

Exceptionally, up to 2 m

Growth Rate

5 m/year

Adult dispersal potential

10-100m

Dependency

Independent

Sociability

Solitary

Toxic/Poisonous?

General Biology Additional Information

The stated growth rate refers to vegetative growth recorded in perennial populations whereas annual populations may expand at 30m / year in good conditions (Holt et al. 1997). The following species have been recorded only from seagrass leaves:

the hydroid Laomedea angulata;
the algae Rhodophysema georgii, Halothrix lumbricalis,Leblondiella densa, Myrionema magnusii, Cladosiphon zosterae, Punctaria crispata; and
Cladosiphon contortus, which is larger and found primarily on Zosterasp.

Biology References

Hartog den, 1970, Phillips & Menez, 1988, Davison & Hughes, 1998, Jones et al., 2000, Anonymous, 1999(p), Holt et al., 1997,

Distribution and Habitat

Distribution in Britain & Ireland

Zostera marina has a wide but patchy distribution in southwest of England, the Solent and Isle of Wight on the south coast, Wales, western Ireland, western and eastern Scotland including Orkney and the Shetland Islands.

Global distribution

Widespread through the Atlantic and Pacific. It is the only seagrass species that extends into the Arctic Circle. It has a restricted distribution in the Mediterranean.

Biogeographic range

Not researched

Depth range

0 to 5m

Migratory

Non-migratory / Resident

Distribution Additional Information

In 1920s and 1930s the previously extensive beds of eelgrass were severely reduced by an outbreak of 'wasting disease', which appears to affect sublittoral Zostera marina primarily. To date, recovery has been poor or slow. An exceptional bed of Zostera marina occurs in the clear waters of Ventry Bay, south-west Ireland and extends from 0.5 to 10m in depth and up to 13m deep in some patches. It should be noted that the global distribution of Zostera marina includes records of Zostera angustifolia which is considered synonymous outside the UK. It extends from Arctic Circle in northern Russia to near Gibraltar, Spain along the European coast. In has a restricted distribution in the Mediterranean, limited to northern parts of Adriatic and Aegean Seas, brackish etangs and lagoons in southern France. On the western Atlantic coast it extends from west coast of Alaska to North Carolina. In the Pacific it is recorded from Japan, Korea and from Alaska to Baja California, Mexico.

Substratum preferences

Gravel / shingle
Muddy gravel
Sandy mud
Muddy sand

Physiographic preferences

Estuary
Isolated saline water (Lagoon)
Enclosed coast / Embayment

Biological zone

Sublittoral Fringe
Upper Infralittoral

Wave exposure

Sheltered
Very Sheltered

Tidal stream strength/Water flow

Weak (<1 kn)
Very Weak (negligible)

Salinity

Variable (18-40 psu)

Habitat Preferences Additional Information

Distribution References

Hartog den, 1970, Phillips & Menez, 1988, Davison & Hughes, 1998, Jones et al., 2000, Stewart et al., 1994, NBN, 2002,

Reproduction/Life History

Reproductive type

Vegetative
Protogynous hermaphrodite

Developmental mechanism

Oviparous

Reproductive Season

May to September

Reproductive Location

Reproductive frequency

Annual episodic

Regeneration potential

Life span

21-50 years

Age at reproductive maturity

1-2 years

Generation time

1-2 years

Fecundity

Insufficient information

Egg/propagule size

Fertilization type

Larvae/Juveniles
Larval/Juvenile dispersal potential	100-1000m	Larval settlement period	Not relevant
Duration of larval stage	Not relevant

Reproduction Preferences Additional Information

Zostera sp. are perennials but may act as annuals under stressful conditions (Phillips & Menez 1988). Eelgrass reproduces vegetatively, i.e.. by growth of rhizome. Vegetative reproduction probably exceeds seedling recruitment except in areas of sediment disturbance (Reusch et al. 1998; Phillips & Menez 1988). Examination of the population structure of a Zostera marina bed in the Baltic Sea suggested that individual genotypes (vegetatively produced clones) may be up to 50 years old and further suggested that the eelgrass bed at that site had been present for at least 67 years (Reusch et al. 1998).

All parts of the plant may float if they become detached from substrate. Pieces of rhizome or shoots (if displaced by for example storm action) may take root if they settle on suitable substratum.
The generative stalk may be released together with the seed compliment and may be carried great distances (Phillips & Menez, 1988).
In New York, USA, Churchill et al. (1985) recorded 5-13 percent of seeds with attached gas bubbles and achieved an average dispersal distance of 21m and up to 200m in a few cases.
Wildfowl may disperse seeds on their feet, or in their gut.. For example, 30 percent of freshwater eelgrass (Naja marina) seeds fed to ducks in Japan survived and successfully germinated after passage through their alimentary canals and potentially transported 100-200km (Fishman & Orth 1996).

Phillips & Menez (1988) state that seedling mortality is extremely high. Fishman & Orth (1996) report that 96 percent of seeds were lost from uncaged test areas due to transport (dispersal) or predation. Ecological genetics studies of Zostera marina in False and Padilla Bays on Pacific coast of USA (Ruckelhaus 1998), detected genetic differentiation between intertidal and subtidal zones and between the bays. Estimates of gene flow suggested that seed dispersal was more important than pollen dispersal, effective migration (2.9 migrants/generation) occurred between the bays (14 km apart) and that the population subdivision was in part explained by disturbance and recolonization. Phillips & Menez (1988) note that seedlings rarely occur within the eelgrass bed except in areas cleared by storms, blow-out or excessive herbivory.

Reproduction References

Hartog den, 1970, Phillips & Menez, 1988, Davison & Hughes, 1998, Reusch et al., 1998, Churchill et al., 1985, Stewart et al., 1994, Fishman & Orth, 1996, Rucklehaus, 1998,