|Scientific Name:||Halophila ovalis|
|Species Authority:||(R.Br.) Hook.f.|
Halophila gaudichaudii J. Kuo
Halophila major (Zoll.) Miq.
Halophila mikii J. Kuo
Halophila okinawensis J. Kuo
|Taxonomic Notes:||This a member of the Halophila ovalis complex, which is under taxonomic review. Historically, other species currently considered to be in this complex may have been labelled as H. ovalis.|
|Red List Category & Criteria:||Least Concern ver 3.1|
|Assessor/s:||Short, F.T., Carruthers, T.J.R., Waycott, M., Kendrick, G.A., Fourqurean, J.W., Callabine, A., Kenworthy, W.J. & Dennison, W.C.|
|Reviewer/s:||Livingstone, S., Harwell, H. & Carpenter, K.E.|
This species is widespread. It is impacted by anthropogenic threats locally, but recovers quickly if the threats are removed. Population trends are stable or increasing in many parts of its range. This species is listed as Least Concern.
|Range Description:||Halophila ovalis is widespread in the Indo-Pacific. In the Pacific, it occurs from southern Japan throughout Southeast Asia, many islands of the western Pacific, and through all but the southern coast of Australia as well as Lord Howe and Norfolk Islands and as far east as Tonga and Samoa. In the Indian Ocean, H. ovalis is found from southwestern Australia to East Africa and the Red Sea, including Madagascar, with some exceptions of islands or coastlines with no records. Recently H. ovalis has been discovered in the Atlantic Ocean on the Island of Antigua (Short et al. 2010).|
Native:Antigua and Barbuda; Australia; Bahrain; Brunei Darussalam; China; Comoros; Egypt; Eritrea; Fiji; French Polynesia; India; Indonesia; Israel; Japan; Jordan; Kenya; Kuwait; Madagascar; Malaysia; Mauritius; Micronesia, Federated States of; Mozambique; Myanmar; New Caledonia; Oman; Palau; Papua New Guinea; Philippines; Qatar; Samoa; Saudi Arabia; Seychelles; Singapore; Somalia; South Africa; Sri Lanka; Sudan; Tanzania, United Republic of; Thailand; Tonga; United Arab Emirates; United States Minor Outlying Islands; Vanuatu; Viet Nam; Wallis and Futuna; Yemen
|FAO Marine Fishing Areas:||
Atlantic – southeast; Indian Ocean – eastern; Indian Ocean – western; Pacific – eastern central; Pacific – northwest; Pacific – southwest; Pacific – western central
|Range Map:||Click here to open the map viewer and explore range.|
This is a common species. Its global population trend is stable or increasing as it can tolerate disturbances.
A 1988 survey established the existence of approximately 1,200 km² of seagrass habitat in southwestern Hervey Bay, Australia. Surveys in 1992 and 1993 add an additional 400 km² of habitat in the northeastern portion of the bay which was not surveyed in 1988. Halophila spinulosa and Halophila ovalis were the most common seagrasses. Following two floods and a cyclone in 1992, virtually all of the seagrasses in southwestern Hervey Bay had disappeared which represents approximately 24% of the known area of seagrass along the east coast of Queensland. This die-off is unprecedented in the past 100 years. Initial recovery was restricted to deep water (>10 m) as recorded in 1993. Only a few, unpredictable shallow sites showed signs of recovery. Deep-water recovery was resulting from germination of seeds. Communities in deeper waters were expected to recover in a few years. Recovery for the shallow water region is unpredictable but recovery from other events has taken 10 or more years (Preen et al. 1995).
Cockburn Sound, Western Australia, has been subjected to steady degradation since 1954, with the establishment of an oil refinery and the successive establishments of steel works, fertilizer factories, sewage-treatment facilities, and a power station. This has lead to contaminated effluents and increased nutrient loads. Between 1954 and 1978 the meadow in this region reduced from 4,200 to 900 ha and leaf detritus production has reduced from 23,000 to 4,000 t dry weight/year. Seagrasses in this region include Posidonia sinuosa, P. australis, P. coriacea, Halophila ovalis, H. decipiens, Syringodium isoetifolium, Heterozostera tasmanica, Amphibolis griffithii, and A. antarctica (Cambridge and McComb 1984).
|Habitat and Ecology:||
Halophila ovalis is rapidly growing, with high turn-over, wide ecological range, and is considered a pioneering species. This species is one of the most common foods of the Dugong.
In Arabian Gulf, this species tolerates extreme conditions with salinity varying from 38-70 practical salinity units (psu) and temperatures of 10-39°C (inshore) and 19-33°C (offshore) (Green and Short 2003).
Photosynthetic studies in Tanzania indicate an enhanced photosynthetic rate in the high, frequently air-exposed, intertidal zone which may have been related to a capacity to take up the elevated HCO3 levels directly. This is a pioneer species in Mozambique in exposed sandy areas close to the coastline (Green and Short 2003).
It grows rapidly and survives well in unstable and depositional environments in eastern Australia (Green and Short 2003).
It is widely distributed in Thailand because of its ability to grow in different habitats, such as mud, muddy sand and dead coral fragments in the upper littoral and subtidal areas (Green and Short 2003).
In Peninsular Malaysia, it is common all around the coast on muddy shores and areas exposed at low tide. This species is ephemeral with rapid turn-over and high seed set and is well adapted to high levels of disturbance (Green and Short 2003).
In the western islands of the western Pacific, it is found in intertidal habitat mixed with Enhalus acoroides in Palau or Thalassia hemprichii in Yap, commonly found in deep water at the offshore edge of mixed seagrass meadows (Green and Short 2003). In Micronesia, it is tolerant of 40°C temperature and low salinity (Green and Short 2003).
In Indonesia, it has a wide vertical range, from the intertidal zone down to more than 20 m depth, and grows specially well on disturbed sediments such as the mounds of burrowing invertebrates (Green and Short 2003).
Halophila ovalis is more susceptible to elevated temperatures than some species of seagrass (Campbell et al. 2006). Climate change is also a threat for this species, and it is collected and sold internationally for aquaria.
Oil globules and oily black films discharges negatively affect H. ovalis in the Arabian Gulf (Green and Short 2003), and overexploitation and influences from activities on land (trawling activities, high hotel density in close proximity to the beach, raking, burying and removing seagrass beach cast material) occur in Kenyan and Tanzanian shores. Declining water quality due to increasing populations in coastal towns and cities is also an issue (Green and Short 2003).
In India, the natural causes of destruction are cyclones, waves, intense grazing and infestation of fungi and epiphytes, as well as "die-back" disease. Other threats include anthropogenic activities such as deforestation in the hinterland or mangrove destruction, construction of harbours or jetties, and loading and unloading of construction materials. Anchoring and moving of boats, ships, dredging and discharge of sediments, land filling and untreated sewage disposal (Green and Short 2003).
In Western Australia, threats include human activities such as direct physical damage caused by port and industrial development, pipelines, communication cables, mining and dredging, excessive loads of nutrients causing seagrass overgrowth and smothering by epiphytes, and land based activity associated with ports, industry, aquaculture, farming, direct physical damage by recreational and commercial boating activities (Green and Short 2003).
In eastern Australia, population reduction is caused by the result of light reduction due to sediment loads in water, coastal development, dredging and marine developments, and minor damage from boating and shipping activities. This species also could be impacted by coastal runoff and to some extent trawling activities (Green and Short 2003).
In Thailand, it is threatened by a combination of illegal fisheries and fishing practices, and land-based activities, especially mining, reduced water quality resulting from upland clearing, development along rivers and destruction of mangrove forests (Green and Short 2003).
In Malaysia, loss was caused by intensive sand mining for reclamation activities in mangrove swamps as part of the construction of a condominium which resulted to suspended particles in the water settled on its leaves, blocking sunlight for photosynthesis and causing considerable stress and mortality through burial. This species also was damaged by intense winds, waves and sediment movement during the northeast monsoon storms of October 1998 to January 1999 (Green and Short 2003).
In the western Pacific, threats include coastal development, dredging, and marina developments, climate change and associated increase in storm activity, water temperature and/or sea-level rise (Green and Short 2003).
In Indonesia, H. ovalis is threatened mainly by physical degradation such as mangrove cutting and coral reef damage, by marine pollution from both land- and marine-based resources, and by over exploitation of living marine resources such as fish, molluscs and sea cucumbers (Green and Short 2003).
In the Philippines, it is threatened by eutrophication, siltation, pollution, dredging and unsustainable fishing methods (Green and Short 2003).
In Japan, threats occur from industrial developments in coastal regions, land reclamation resulting to loss of vegetation, water pollution, disturbance of habitats by fish trawling, changes in environmental conditions due to human activities (Green and Short 2003).
In the United Arab Emirates, there has recently been implementation of the beginning of an effective management program that would start with baseline mapping, followed by periodic monitoring and mapping efforts. This species is also protected under the UNEP Regional Seas Programme, GCC (Gulf Cooperative Council), GAOCMAO (Gulf Area Oil Companies Mutual Aid Organisation) and other agreements which relate to environmental management and pollution controls. This species also is considered in the most recent management plan of the Mombosa Marine National Park and Reserve, and is included in the integrated coastal zone management initiatives in Tanzania by IUCN, Zanzibar (Menai Bay Conservation Project), Mafia Marine Park (by WWF) and Kinondoni Coastal Area Management Programme.
Halophila ovalis is found in a marine park in Swan River and in Shark Bay World Heritage Property which contains more than 4000 km² of seagrass beds of high density in Western Australia. It cannot be damaged without a permit in New South Whales and Queensland.
It also occurs in the seagrass beds in Haad Chao Mai National Park, the largest seagrass beds with the highest species diversity for a single area in Thailand. Management policies were proposed in 1998 by the Office of Environmental Policy and Planning in Thailand.
In the western Pacific islands, H. ovalis is recognized in the need for sanctuaries and protected areas. There are also NGOs focused on conservation and environmental protection integrated with traditional leadership and government agencies, suggesting that conservation measures and the acceptance of enforcement will continue to improve. Additionally, it is included in the management guide in the Seagrass Policy, Strategy and Action Plan drafted by the Indonesian Seagrass Committee (ISC), and monitored in SeagrassNet located in Puerto Galera (Philippines) which shows the impacts of eutrophication at the site adjacent to a coastal town (Green and Short 2003).
Cambridge, M.L. and McComb, A.J. 1984. The loss of seagrasses in Cockburn Sound, Western Australia. I. The time course and magnitude of seagrass decline in relation to industrial development. Aquatic Botany 20: 229-243.
Campbell, S.J., McKenzie, L.J. and Kerville, S.P. 2006. Photosynthetic responses of seven tropical seagrasses to elevated seawater temperature. Journal of Experimental Marine Biology and Ecology 330: 455-468.
Green, E.P. and Short, F.T. 2003. World Atlas of Seagrasses. University of California Press, Berkeley.
IUCN. 2010. IUCN Red List of Threatened Species (ver. 2010.3). Available at: http://www.iucnredlist.org. (Accessed: 2 September 2010).
Preen, A.R., Lee Long, W.J. and Coles, R.G. 1995. Flood and cyclone related loss, and partial recovery, of more than 1,000 km² of seagrass in Hervey Bay, Queensland, Australia. Aquatic Botany 52: 3-17.
Short, F.T., Moore, G.E., and Peyton, K.A. 2010. Halophila ovalis in the Tropical Atlantic Ocean. Aquatic Botany in press.
|Citation:||Short, F.T., Carruthers, T.J.R., Waycott, M., Kendrick, G.A., Fourqurean, J.W., Callabine, A., Kenworthy, W.J. & Dennison, W.C. 2010. Halophila ovalis. In: IUCN 2012. IUCN Red List of Threatened Species. Version 2012.2. <www.iucnredlist.org>. Downloaded on 18 June 2013.|
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