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Intertidal narrow strap seagrass

Short description

Intertidal seagrass meadows dominated by the narrow strap seagrass Halodule uninervis.

Disclaimer: Ecosystem type descriptions are based on biophysical attributes identified in Central Queensland through expert advice and supported by scientific literature. Not all ecosystem types are mapped based on current inventory, and many of the ecosystems described here may also occur in other parts of Queensland.

<em>H. uninervis</em>, Gladstone. Photo by TropWATER Seagrass Ecology Group

Classification categories

Select from the links below to view related ecosystem type categories

Long description

Intertidal seagrass meadows dominated by the narrow strap seagrass Halodule uninervis. Halodule uninervis also includes a wide strap growth form, see type (12). These meadows can also include Zostera muelleri subsp. capricorni*, Cymodocea rotundata, Cymodocea serrulata, Enhalus acoroides, Halodule pinifolia, Halodule uninervis, Thalassia hemprichii, Thalassodendron ciliatum, Halophila spp. and Syringodium isoetifolium.

Seagrasses are not a taxonomically unified group, but rather an ecological group that arose through convergent evolution and includes several different families. They are all flowering plants that live underwater and need light to photosynthesise. They also produce seeds. They grow on muds, sands and fine gravels which may be mobile. Meadows may include other structural macrobiota, such as encrusting algae, erect macrophyte algae, bryozoans, sponges and molluscs (e.g. bivalves, cockles, whelks, razor clam beds), together with mobile invertebrate fauna, such as sea cucumbers, crabs (e.g. commercial sand crabs and other portunids) and polychaete worms.

Halodule uninervis is typically more enduring than early colonising species of the genus Halophila, but is considered a colonising and opportunistic seagrass forming both transitory and enduring meadows. Transitory meadows increase and decrease in extent and biomass seasonally, and can re-establish following complete loss through sexual reproduction. Enduring meadows may fluctuate but generally remain to some extent through seasons and years. More colonising species typically have fast shoot turnover, short lifespan, fast sexual maturation and development of a (dormant) seed bank. They have low physiological resistance to disturbance but a rapid ability to recover[5].

*Revision of Zostera capricorni has resulted in classification to subspecies. In Queensland, Zostera capricorni has been revised to Zostera muelleri subsp. capricorni[4].

Special values

Seagrasses provide a wide range of services, including:

  • primary production, carbon fixation and nutrient removal
  • support numerous herbivore and detritivore-based food webs, including food for dugongs and green turtles (mostly H. uninervis and H. ovalis), and many fisheries species (e.g. prawns and fishes) and others (e.g. razor clam)
  • fisheries habitat (e.g. food, refuge and reproduction)
  • coastal protection, erosion control and sediment capture
  • tourism, recreation, education and research[7][11][5].

Seagrass meadows, particularly those containing H. uninervis and H. ovalis, provide food for dugong[11] and green sea turtles[6]. Dugongs feed mostly on the roots of H. uninervis. Halodule uninervis[11] and H. ovalis [8] are reported to be the most nutritious seagrasses due to high nitrogen and starch content[12]. Grazing of H. uninervis and H. ovalis has been shown to increase production of a nitrogen-rich standing crop[8][1][6].

Diagnostic attributes

Inundation 'Intertidal – Lower low', 'Intertidal – Mid low', 'Intertidal – Upper low', 'Intertidal – Low undifferentiated', 'Intertidal – Lower medium', 'Intertidal – Upper-medium', 'Intertidal – Medium undifferentiated', 'Intertidal – High', 'Intertidal – Undifferentiated', 'Intertidal – High undifferentiated' although usually occurring below mean sea level

Structural macrobiota 'Seagrass – strap narrow'


Seagrass ecosystems vary in Period and Trend (seasonally and from year to year). The species composition, extent and biomass of seagrass meadows can vary seasonally and between years. The extent and biomass of seagrass meadows along the Queensland east coast are typically maximal in late spring and summer, and minimal over winter[2][3][10].


The following relates to distribution of this ecosystem type within the Central Queensland mapping area:

  • Unmapped. Halodule uninervis can have a narrow growth form but is not mapped in the Central Queensland area as available data did not distinguish between the wide and narrow growth form, with all H. uninervis allocated to narrow
  • Halodule uninervis provides food for dugong[11] and was observed in Port Curtis during recent seagrass surveys[9]
  • Extensive seagrass meadows in Port Curtis are the only described large area of seagrass between Hervey Bay and Shoalwater Bay, and are therefore very important regionally[9][3]. Aggregated Z. muelleri patches are the most extensive seagrass meadows in Port Curtis, together with relatively large areas of aggregated H. uninervis patches. Zostera muelleri dominated meadows on muddy sediments whereas H. uninervis dominated meadows on sandy sediments between Quoin and Facing Islands and along the exposed coasts of Boyne and Wild Cattle islands. Other seagrass meadows in Port Curtis include (in decreasing extent based on dominant genera) include: continuous Z. muelleri patches, aggregated Halophila spp. patches, continuous H. uninervis cover, isolated Z. muelleri patches and isolated H. uninervis patches[3]
  • Halodule uninervis dominated meadows have been mapped around Burrum Heads and along the western side of the Great Sandy Strait. Dugongs travel along this shore to feed, with tagging studies showing movements from Burrum Heads to Kauri Creek where there is a big persistent meadow[11]
  • Thalassia hemprichii does not occur in Central Queensland.


See type 12 (intertidal wide seagrass) for detailed discussion of relevant attributes.

Additional Information

Seagrass - Queensland Government

Case study: Hervey Bay seagrass and dugong - Queensland Government

Saltmarshes, seagrasses and algae - Department of Agriculture and Fisheries


Seagrass - Queensland Government

Seagrasses - Australian Institute of Marine Science (AIMS)

A Vulnerability Assessment for the Great Barrier Reef - Great Barrier Reef Marine Park Authority

Seagrass Restoration Network


  1. ^ Aragones, LV, Lawler, IR, Foley, WJ & Marsh, H (October 2006), 'Dugong grazing and turtle cropping: grazing optimization in tropical seagrass systems?', Oecologia. [online], vol. 149, no. 4, pp. 635-647. Available at: [Accessed 3 April 2019].
  2. ^ Bruinsma, C & Danaher, K (2001), Queensland Coastal Wetland Resources: Round Hill Head to Tin Can Inlet.. [online], vol. QI99081, Department of Primary Industries, Queensland Government., Brisbane. Available at:
  3. ^ a b c Danaher, K, Rasheed, M & Thomas, R (2005), The intertidal wetlands of Port Curtis, Department of Primary Industries and Fisheries.
  4. ^ Jacobs, S & Les, D (26 October 2009), 'New combinations in Zostera (Zosteraceae)', Telopea. [online], vol. 12, no. 3, pp. 419-423. Available at: [Accessed 25 March 2019].
  5. ^ a b Kilminster, K, McMahon, K, Waycott, M, Kendrick, GA, Scanes, P, McKenzie, L, O'Brien, KR, Lyons, M, Ferguson, A & Maxwell, P (2005), 'Unravelling complexity in seagrass systems for management: Australia as a microcosm', Science of the Total Environment, vol. 534, pp. 97-109, Elsevier.
  6. ^ a b Kuiper-Linley, M, Johnson, CR & Lanyon, JM (2007), 'Effects of simulated green turtle regrazing on seagrass abundance, growth and nutritional status in Moreton Bay, south-east Queensland, Australia', Marine and Freshwater Research. [online], vol. 58, no. 5, p. 492. Available at: [Accessed 5 April 2019].
  7. ^ McKenzie, LJ, Collier, CJ, Langlois, LA, Yoshida, RL, Smith, N & Waycott, M (2018), Marine Monitoring Program: Annual Report for inshore seagrass monitoring 2016-2017. Report for the Great Barrier Reef Marine Park Authority. [online], p. 248pp., Great Barrier Reef Marine Park Authority, Townsville. Available at:
  8. ^ a b Preen, AR, Long, WJL & Coles, RG (1995), 'Flood and cyclone related loss, and partial recovery, of more than 1000 km 2 of seagrass in Hervey Bay, Queensland, Australia', Aquatic Botany, vol. 52, no. 1, pp. 3-17, Elsevier.
  9. ^ a b Rasheed, MA, Thomas, R, Roelofs, AJ, Neil, KM & Kerville, SP (2003), Port Curtis and Rodds Bay Seagrass andBenthic Macro-Invertebrate Community Baseline Survey.
  10. ^ Sheaves, M (2005), 'Nature and consequences of biological connectivity in mangrove systems', Marine Ecology Progress Series. [online], vol. 302, pp. 293-305. Available at: [Accessed 15 March 2019].
  11. ^ a b c d e Sheppard, JK, Preen, AR, Marsh, H, Lawler, IR, Whiting, SD & Jones, RE (2006), 'Movement heterogeneity of dugongs, Dugong dugon(Müller), over large spatial scales', Journal of experimental marine biology and ecology, vol. 334, no. 1, pp. 64-83, Elsevier.
  12. ^ Sheppard, JK, Lawler, IR & Marsh, H (2007), 'Seagrass as pasture for seacows: Landscape-level dugong habitat evaluation', Estuarine, Coastal and Shelf Science, vol. 71, no. 1, pp. 117-132, Elsevier.

Last updated: 22 July 2019

This page should be cited as:

Department of Environment, Science and Innovation, Queensland (2019) Intertidal narrow strap seagrass, WetlandInfo website, accessed 18 March 2024. Available at:

Queensland Government
WetlandInfo   —   Department of Environment, Science and Innovation