Zostera muelleri is a southern hemisphere temperate species[5] of seagrass native to the seacoasts of South Australia, Victoria and Tasmania.[6][7] and New Zealand. Today, Zostera muelleri can be found in regions of Australia, New Zealand, and Papua New Guinea,[1] as well as areas of the eastern Indian Ocean, and the southwest and western central Pacific Ocean.[1] Zostera muelleri is a marine angiosperm, and is commonly referred to as eelgrass or garweed.[8] It is a fast growing and readily colonizing species that serves as a feeding ground for wading birds[9] and aquatic animals,[10] and a breeding ground for juvenile fish[10] and shrimp species.[9]
| Zostera muelleri | |
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Scientific classification 
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| Kingdom: | Plantae |
| Clade: | Tracheophytes |
| Clade: | Angiosperms |
| Clade: | Monocots |
| Order: | Alismatales |
| Family: | Zosteraceae |
| Genus: | Zostera |
| Species: | Z. muelleri
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| Binomial name | |
| Zostera muelleri | |
| Synonyms[4] | |
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Seagrasses are a flowering plant species, not to be confused with seaweed,[8] which do not form flowers, fruits, and seeds to reproduce. Seagrasses are important to the marine ecosystem for many reasons. For one, they provide food, homes, and breeding grounds to a variety of marine species.[5] Secondly, meadows of seagrass are important carbon reservoirs or sinks,[5] sequestering 10-18% of the ocean's carbon accumulation for long-term storage.[11] Seagrasses also enhance sediment accretion,[11] and protect coastlines from destructive wave energy.[9]
Taxonomy
editZostera muelleri belongs to the order Alismatales. There are approximately 72 species of seagrasses.[5] There are three families of seagrasses, Zosteraceae, Hydrocharitaceae, and Cymodoceaceae.[5] There is some taxonomic uncertainty with this species.[1] Zostera muelleri is synonymous with Z. mucronata, Z. capricorni, and Z. novazelandica,[1] which were once separate species, but since then molecular and morphological studies have confirmed that they are members of the same species.[9] In 2006, Jacobs et al. (2006) suggested the final name of the species be Z. muelleri.[1] Zostera muelleri has three subspecies, Z. muelleri subsp. capricorni, Z. muelleri subsp. mucronata, and Z. muelleri subsp. muelleri.[8]
Habitat and geographic range
editZostera muelleri is a perennial species, meaning populations of it endure year round.[12] They are mostly found in places such as littoral or sublittoral sand flats,[12] sheltered coastal embayments,[12] soft, muddy, sandy areas near a reef,[8] estuaries,[9] shallow bays,[9] and in intertidal shoals.[9] They aren't common on reefs because there is little space and nutrients for them to grow there.[8] Zostera muelleri is a marine species, but it can tolerate some freshwater inputs.[9] It mostly occurs in mono-specific meadows, but it can grow alongside Ruppia, Halophila, and Lepilena.[9] Zostera muelleri is widespread in Southern Australia, and its also found in New Zealand and Papua New Guinea.[1]
Morphology
editThis species has long strap-shaped leaves,[5] rounded leaf tips[9] and thin rhizomes that are <3 mm in diameter.[9] There are visible cross-veins in the leaf.[9] The rhizomes are either dark brown or yellow.[9] Young rhizomes are typically yellow, but the leaves of this plant can turn red if they're under high sunlight.[9] Because of its phenotype, Z. muelleri can be confused with Z. tasmanica and Z. capensis.[9] The leaf width morphology is variable, so Z. muelleri with thin leaves can sometimes also be confused with H. uninervus.[1]
Adaptations to marine life
editThe species Z. muelleri evolved from terrestrial plants, but adapted to marine life around 140 million years ago during the Cretaceous period.[5] In order to adapt to life in the ocean, the Z. muelleri genome lost/modified several genes which had once helped them survive on land, such as genes for hormone biosynthesis and signaling and cell wall catabolism.[5] Some of the genes that were lost include genes associated with ethylene synthesis and signaling pathways, as well as genes involved in pectin catabolism.[5] Additionally, genes for stomatal differentiation, terpenoid synthesis, and ultraviolet resistance were lost.[5] The genes responsible for salinity tolerance and stress-resistance remain in the genome.[5]
Reproduction
editSeagrasses are flowering species,[8] but they can reproduce both sexually and asexually.[12] Reproducing sexually increases genetic variation, which can enhance a plant's ability to adapt to a changing environment, but asexual reproduction requires less effort and is what Z. muelleri typically uses to maintain its population.[12] When reproducing sexually, the plant's flowers form an inflorescence that is enclosed in a spathe (a large sheathing bract that encloses flower clusters in certain plant species).[9] Each shoot can have up to 6 spathes, which contain 4-12 pairs of male and female flowers.[9] Larger plants will have more flowers. Male flowers typically mature before female flowers.[9] Once a flowering shoot matures, it darkens and breaks off the plant, and floats away. The enclosed seeds then become deposited in sediment someplace else.[9] Zostera muelleri can reproduce asexually via rhizome encroachment,[13] which is a form clonal reproduction. The plant can use this form of regeneration to recover from high intensity disturbances.[13]
Threats and losses
editThreats to this species include coastal development,[1] eutrophication,[11] boat mooring,[11] dredging,[11] agricultural/urban runoff,[11] and sedimentation.[1] Meadows of Z. muelleri have been lost in areas of Port Phillip Bay and New Zealand due to habitat disturbance, sedimentation, and turbidity.[9] During the 1960s, meadows of Z. muelleri in New Zealand were affected by a wasting disease.[1] Because it is less tolerant of heat than other tropical species, climate change may be a threat to meadows of this species in tropical regions.[1]
Conservation
editThere are currently no conservation measures for this species.[1]
References
edit- ^ a b c d e f g h i j k l m Short, F.T.; Williams, S.L.; Carruthers, T.J.R.; Waycott, M.; Kendrick, G.A.; Fourqurean, J.W.; Callabine, A.; Kenworthy, W.J.; Dennison, W.C. (2010). "Zostera muelleri". IUCN Red List of Threatened Species. 2010: e.T173384A7004901. doi:10.2305/IUCN.UK.2010-3.RLTS.T173384A7004901.en. Retrieved 20 November 2021.
- ^ "Zostera muelleri Irmisch ex Asch". Plants of the World Online. The Trustees of the Royal Botanic Gardens, Kew. n.d. Retrieved September 27, 2020.
- ^ "Zostera muelleri Irmisch ex Asch". World Flora Online. The World Flora Online Consortium. n.d. Retrieved September 27, 2020.
- ^ The Plant List
- ^ a b c d e f g h i j k HueyTyng Lee; Agnieszka A. Golicz; Philipp E. Bayer; Yuannian Jiao; Haibao Tang; Andrew H. Paterson; Gaurav Sablok; Rahul R. Krishnaraj; Chon-Kit Kenneth Chan; Jacqueline Batley; Gary A. Kendrick; Anthony W.D. Larkum; Peter J. Ralph & David Edwards (3 July 2016). "The Genome of a Southern Hemisphere Seagrass Species (Zostera muelleri)". Plant Physiology. 172 (1): 272–283. doi:10.1104/pp.16.00868. PMC 5074622. PMID 27373688.
- ^ Paul Friedrich August Ascherson. 1867. Linnaea 35: 168 Zostera muelleri
- ^ Paul Friedrich August Ascherson. 1867. Sitzungsberichte der Gesellschaft Naturforschender Freunde zu Berlin : 15. Zostera muelleri
- ^ a b c d e f "Zostera muelleri subsp. capricorni (Asch.) S.W.L.Jacobs". Atlas of Living Australia. Retrieved 16 April 2017.
- ^ a b c d e f g h i j k l m n o p q r s t Michelle Waycott; Kathryn McMahon; Paul Lavery (2014). A Guide to Southern Temperate Seagrasses. Csiro Publishing. pp. 90–91. ISBN 978-1486300167. Retrieved 16 April 2017.
- ^ a b "Seagrass database launched". UTS. 28 May 2015. Retrieved 16 April 2017.
- ^ a b c d e f Mathieu Pernice; Sutinee Sinutok; Gaurav Sablok; Audrey S. Commault; Martin Schliep; Peter I. Macreadie; Michael A. Rasheed; Peter J. Ralph (21 October 2016). "Molecular physiology reveals ammonium uptake and related gene expression in the seagrass Zostera muelleri". Marine Environmental Research. 122: 126–134. Bibcode:2016MarER.122..126P. doi:10.1016/j.marenvres.2016.10.003. hdl:10453/58802. PMID 28327303.
- ^ a b c d e Virginie M. Dos Santos; Fleur E. Matheson (16 December 2016). "Higher seagrass cover and biomass increases sexual reproductive effort: A rare case study of Zostera muelleri in New Zealand". Aquatic Botany. 138: 29–36. doi:10.1016/j.aquabot.2016.12.003.
- ^ a b Peter I. Macreadie; Paul H. York; Craig D.H. Sherman (21 January 2014). "Resilience of Zostera muelleri seagrass to small-scale disturbances: the relative importance of asexual versus sexual recovery". Ecology and Evolution. 4 (4): 450–461. doi:10.1002/ece3.933. PMC 3936391. PMID 24634729.