Biodiversity & Conservation

Zostera noltii beds in upper to mid shore muddy sand



Image Mark Davies - A bed of Zostera noltii with Hydrobia ulvae visible on the mud surface. Image width ca 40 cm.
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Distribution map

LS.LMS.ZOS.Znol recorded (dark blue bullet) and expected (light blue bullet) distribution in Britain and Ireland (see below)

  • EC_Habitats
  • UK_BAP

Recorded distribution in Britain and Ireland

This biotope is sparsely distributed around the UK, with particularly extensive stands in Cromarty Firth, and along the Essex and north Kent coasts.

Habitat preferences

Temperature range preferences - 5 -30 °C

Water clarity preferences - Medium clarity / Medium turbidity
Low clarity / High turbidity

Limiting Nutrients - Nitrogen (nitrates)
Phosphorus (phosphates)

Other preferences - No text entered

Additional information

Populations of Zostera noltii occur from the Mediterranean to southern Norway, the Black Sea, the Canary Islands and are regarded to prefer sea temperatures between about 5 - 30 C. However, Massa et al. (2009) found Zostera noltii to be tolerant of temperatures up to 37°C for an exposure period of 21 days. Therefore, they may not be sensitive to the range of temperatures likely in the British Isles (Davison & Hughes, 1998). Intertidal populations may be damaged by frost (den Hartog, 1987) and Covey & Hocking (1987) reported defoliation of Zostera noltii in the upper reaches of mudflats in Helford River due to ice formation in the exceptionally cold winter of 1987. However, the rhizomes survived and leaves are lost at this time of year due to shedding, storms or grazing with little apparent effect (Nacken & Reise, 2000).

Seagrass requires a particular light regime to net photosynthesize and grow. The intertidal is likely to be more turbid than the shallow subtidal occupied by Zostera marina due to runoff and re-suspension of sediment by wave and tidal action. Turbidity decreases light penetration and reduces the time available for net photosynthesis. However, intertidal Zostera noltii 'escapes' this turbidity since it is able to take advantage of the high light intensities at low tide (Vermaat et al., 1996).

Seagrass beds act as sinks for nutrients (Asmus & Asmus, 2000b) and as such, nitrogen may not be limiting in sparse intertidal seagrass beds. In sandy sediments phosphate may be limiting where it is adsorbed onto particles (Short, 1987; Jones et al., 2000).

This review can be cited as follows:

Tyler-Walters, H. & Wilding, C.M. 2008. Zostera noltii beds in upper to mid shore muddy sand. Marine Life Information Network: Biology and Sensitivity Key Information Sub-programme [on-line]. Plymouth: Marine Biological Association of the United Kingdom. [cited 30/11/2015]. Available from: <>