Biodiversity & Conservation

Beaked tasselweed - Ruppia maritima

Ruppia maritima

Image Sue Scott - A dense stand of Ruppia sp. Image width ca 10 cm.
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Distribution map

Ruppia maritima recorded (dark blue bullet) and expected (light blue bullet) distribution in Britain and Ireland (see below)

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Ruppia maritima is not listed under any importance categories.

Taxonomy icon Taxonomy Taxon English term
Phylum Angiospermophyta Seagrass, tassel weeds, reeds, sea pink & grasses
Class Liliopsida
Authority Linnaeus, 1753
Recent synonyms None
Map icon Recorded Distribution in Britain and Ireland Found all around the British coast wherever suitable habitat exists, as well as in brackish inland waters near Nantwich and Sanbach, Cheshire.
Habitat information icon Habitat information Ruppia maritima grows in soft sediments in sheltered shallow coastal waters, from full salinity to nearly fresh water but mainly in brackish waters of lagoonal habitats, lochs, estuaries, creeks and pools in salt marshes, wetlands, ditches and lakes.
Text page icon Description The leaves are bright green, <1 mm wide, 20 -115 mm long, elliptical in cross section with pointed, slightly toothed tips. The leaves are held in membranous sheaths, 5 -22 mm in length at their base. A system of fine, slender rhizomes and fine roots holds the plants into the substratum. Flowers and fruits are borne on a characteristic coiled stalk (the peduncle), which may hold the flowers at the water surface or underwater. However, growth form is very variable, including long, tall plants in deep water, or tightly branched short plants in shallow, clear water. Dwarf forms have also been observed.
Identifying features
  • Very slender stems, up to 0.4 m long, sparingly to richly branched.
  • Leaves, 0.35 -0.9mm wide, 20 -115 mm long, bright green with pointed (acute) slightly toothed tips.
  • Leaves ca 50 -210 times as long as wide.
  • Leave sheaths present, 5 -22 mm long.
  • Inflorescence borne on a slender, straight or tightly coiled peduncle, 12 -26mm in length but 0.5 -1.8 times as long as the longest carpel stalk.
  • Inflorescence of two flowers each with 3-5 carpels.
  • Seeds (duplets) pear-shaped, 2-2.8mm by 1.3-1.8mm, dark brown, with wine-red tubercles on surface.
Additional information icon Additional information The taxonomy of Ruppia spp. is difficult and under revision. Ruppia maritima may be confused with Ruppia cirrhosa (syn. spiralis), which has dark green, wider (0.4 -1.4 mm) elongate leaves, with blunt tips, and whose flowers have a relatively longer peduncle (Preston, 1995). Dwarf forms of Ruppia maritima may be confused with the needle spike-rush Eleocharis acicularis.

This review can be cited as follows:

Dr Harvey Tyler-Walters 2001. Ruppia maritima. Beaked tasselweed. Marine Life Information Network: Biology and Sensitivity Key Information Sub-programme [on-line]. Plymouth: Marine Biological Association of the United Kingdom. [cited 31/07/2010]. Available from: <http://www.marlin.ac.uk/speciesinformation.php?speciesID=4272>