Zostera noltei
Ecology
Although a coastal species, this perennial is found at higher levels of the shore than other Zostera species. It grows in sheltered estuaries and harbours, where it is found on mixed substrates of sand and mud. Plants are often concentrated in pools or runnels on the shore. Lowland.
Status
Trends
The distribution of Z. noltei appears to be stable, and it even persists in relatively polluted waters such as the Thames estuary. The reason for the decrease in Hampshire is unclear. It may have been present only as strand-line plants in other squares where it was last recorded before 1970.
World Distribution
Eurasian Southern-temperate element.
Broad Habitats
Light (Ellenberg): 8
Moisture (Ellenberg): 11
Reaction (Ellenberg): 8
Nitrogen (Ellenberg): 5
Salt Tolerance (Ellenberg): 8
January Mean Temperature (Celsius): 4.2
July Mean Temperature (Celsius): 14.9
Annual Precipitation (mm): 1020
Length: 12
Perennation - primary
Life Form - primary
Woodiness
Clonality - primary
Count of 10km squares in Great Britain: 159
Count of 10km squares in Ireland: 36
Count of 10km squares in the Channel Isles: 4
Atlas Change Index: -0.51
JNCC Designations
Scarce Atlas Account
Zostera noltii Hornem.
Dwarf eelgrass
Status: scarce
This is usually the most accessible of the three British Zostera species. It is found highest on the shore in sheltered estuaries and harbours, often adjacent to lower saltmarsh communities, and never below the low-water mark. It is found typically on mixtures of sand and mud, varying in consistency from firm to soft (Gubbay 1988), often in pools or runnels, although it is able to withstand more prolonged exposure than the other Zostera species. It can form extensive populations, as at Maplin Sands, where it covers 325 ha., and sometimes grows amongst stands of Spartina anglica (Gubbay 1988).
Z. noltii is a perennial, flowering in mid-late summer, with seed germination in the autumn. Vegetative dispersal of rhizome fragments is probably the usual means of colonising new sites.
Some of the apparent decline may he attributable to past misidentification, the recording of strandline specimens, or to purely temporal effects of natural variation of estuarine substrates. Whilst the apparent decline from the Moray Firth, Firth of Forth or Solent area might be attributed to pollution, it is difficult to reconcile this with the survival of populations around the Thames estuary. Invasive stands of Spartina anglica could pose a threat at some sites.
The plant is recorded around European coasts from the Mediterranean to south-western Norway and Sweden.
M. Scott
Atlas text references
Atlas (304d)
.
1970. The sea-grasses of the world.
.
1986. Atlas of north European vascular plants north of the Tropic of Cancer. 3 vols.
.
1965. Vergleichende Chorologie der zentraleuropäischen Flora. Volume 1. 2 vols.
.
1994. Scarce plants in Britain.